1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This transformation analyzes and transforms the induction variables (and
11// computations derived from them) into forms suitable for efficient execution
12// on the target.
13//
14// This pass performs a strength reduction on array references inside loops that
15// have as one or more of their components the loop induction variable, it
16// rewrites expressions to take advantage of scaled-index addressing modes
17// available on the target, and it performs a variety of other optimizations
18// related to loop induction variables.
19//
20// Terminology note: this code has a lot of handling for "post-increment" or
21// "post-inc" users. This is not talking about post-increment addressing modes;
22// it is instead talking about code like this:
23//
24//   %i = phi [ 0, %entry ], [ %i.next, %latch ]
25//   ...
26//   %i.next = add %i, 1
27//   %c = icmp eq %i.next, %n
28//
29// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
30// it's useful to think about these as the same register, with some uses using
31// the value of the register before the add and some using // it after. In this
32// example, the icmp is a post-increment user, since it uses %i.next, which is
33// the value of the induction variable after the increment. The other common
34// case of post-increment users is users outside the loop.
35//
36// TODO: More sophistication in the way Formulae are generated and filtered.
37//
38// TODO: Handle multiple loops at a time.
39//
40// TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
41//       of a GlobalValue?
42//
43// TODO: When truncation is free, truncate ICmp users' operands to make it a
44//       smaller encoding (on x86 at least).
45//
46// TODO: When a negated register is used by an add (such as in a list of
47//       multiple base registers, or as the increment expression in an addrec),
48//       we may not actually need both reg and (-1 * reg) in registers; the
49//       negation can be implemented by using a sub instead of an add. The
50//       lack of support for taking this into consideration when making
51//       register pressure decisions is partly worked around by the "Special"
52//       use kind.
53//
54//===----------------------------------------------------------------------===//
55
56#include "llvm/Transforms/Scalar.h"
57#include "llvm/ADT/DenseSet.h"
58#include "llvm/ADT/Hashing.h"
59#include "llvm/ADT/STLExtras.h"
60#include "llvm/ADT/SetVector.h"
61#include "llvm/ADT/SmallBitVector.h"
62#include "llvm/Analysis/IVUsers.h"
63#include "llvm/Analysis/LoopPass.h"
64#include "llvm/Analysis/ScalarEvolutionExpander.h"
65#include "llvm/Analysis/TargetTransformInfo.h"
66#include "llvm/IR/Constants.h"
67#include "llvm/IR/DerivedTypes.h"
68#include "llvm/IR/Dominators.h"
69#include "llvm/IR/Instructions.h"
70#include "llvm/IR/IntrinsicInst.h"
71#include "llvm/IR/ValueHandle.h"
72#include "llvm/Support/CommandLine.h"
73#include "llvm/Support/Debug.h"
74#include "llvm/Support/raw_ostream.h"
75#include "llvm/Transforms/Utils/BasicBlockUtils.h"
76#include "llvm/Transforms/Utils/Local.h"
77#include <algorithm>
78using namespace llvm;
79
80#define DEBUG_TYPE "loop-reduce"
81
82/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
83/// bail out. This threshold is far beyond the number of users that LSR can
84/// conceivably solve, so it should not affect generated code, but catches the
85/// worst cases before LSR burns too much compile time and stack space.
86static const unsigned MaxIVUsers = 200;
87
88// Temporary flag to cleanup congruent phis after LSR phi expansion.
89// It's currently disabled until we can determine whether it's truly useful or
90// not. The flag should be removed after the v3.0 release.
91// This is now needed for ivchains.
92static cl::opt<bool> EnablePhiElim(
93  "enable-lsr-phielim", cl::Hidden, cl::init(true),
94  cl::desc("Enable LSR phi elimination"));
95
96#ifndef NDEBUG
97// Stress test IV chain generation.
98static cl::opt<bool> StressIVChain(
99  "stress-ivchain", cl::Hidden, cl::init(false),
100  cl::desc("Stress test LSR IV chains"));
101#else
102static bool StressIVChain = false;
103#endif
104
105namespace {
106
107/// RegSortData - This class holds data which is used to order reuse candidates.
108class RegSortData {
109public:
110  /// UsedByIndices - This represents the set of LSRUse indices which reference
111  /// a particular register.
112  SmallBitVector UsedByIndices;
113
114  RegSortData() {}
115
116  void print(raw_ostream &OS) const;
117  void dump() const;
118};
119
120}
121
122void RegSortData::print(raw_ostream &OS) const {
123  OS << "[NumUses=" << UsedByIndices.count() << ']';
124}
125
126#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
127void RegSortData::dump() const {
128  print(errs()); errs() << '\n';
129}
130#endif
131
132namespace {
133
134/// RegUseTracker - Map register candidates to information about how they are
135/// used.
136class RegUseTracker {
137  typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
138
139  RegUsesTy RegUsesMap;
140  SmallVector<const SCEV *, 16> RegSequence;
141
142public:
143  void CountRegister(const SCEV *Reg, size_t LUIdx);
144  void DropRegister(const SCEV *Reg, size_t LUIdx);
145  void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
146
147  bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
148
149  const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
150
151  void clear();
152
153  typedef SmallVectorImpl<const SCEV *>::iterator iterator;
154  typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
155  iterator begin() { return RegSequence.begin(); }
156  iterator end()   { return RegSequence.end(); }
157  const_iterator begin() const { return RegSequence.begin(); }
158  const_iterator end() const   { return RegSequence.end(); }
159};
160
161}
162
163void
164RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
165  std::pair<RegUsesTy::iterator, bool> Pair =
166    RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
167  RegSortData &RSD = Pair.first->second;
168  if (Pair.second)
169    RegSequence.push_back(Reg);
170  RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
171  RSD.UsedByIndices.set(LUIdx);
172}
173
174void
175RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
176  RegUsesTy::iterator It = RegUsesMap.find(Reg);
177  assert(It != RegUsesMap.end());
178  RegSortData &RSD = It->second;
179  assert(RSD.UsedByIndices.size() > LUIdx);
180  RSD.UsedByIndices.reset(LUIdx);
181}
182
183void
184RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
185  assert(LUIdx <= LastLUIdx);
186
187  // Update RegUses. The data structure is not optimized for this purpose;
188  // we must iterate through it and update each of the bit vectors.
189  for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
190       I != E; ++I) {
191    SmallBitVector &UsedByIndices = I->second.UsedByIndices;
192    if (LUIdx < UsedByIndices.size())
193      UsedByIndices[LUIdx] =
194        LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
195    UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
196  }
197}
198
199bool
200RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
201  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
202  if (I == RegUsesMap.end())
203    return false;
204  const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
205  int i = UsedByIndices.find_first();
206  if (i == -1) return false;
207  if ((size_t)i != LUIdx) return true;
208  return UsedByIndices.find_next(i) != -1;
209}
210
211const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
212  RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
213  assert(I != RegUsesMap.end() && "Unknown register!");
214  return I->second.UsedByIndices;
215}
216
217void RegUseTracker::clear() {
218  RegUsesMap.clear();
219  RegSequence.clear();
220}
221
222namespace {
223
224/// Formula - This class holds information that describes a formula for
225/// computing satisfying a use. It may include broken-out immediates and scaled
226/// registers.
227struct Formula {
228  /// Global base address used for complex addressing.
229  GlobalValue *BaseGV;
230
231  /// Base offset for complex addressing.
232  int64_t BaseOffset;
233
234  /// Whether any complex addressing has a base register.
235  bool HasBaseReg;
236
237  /// The scale of any complex addressing.
238  int64_t Scale;
239
240  /// BaseRegs - The list of "base" registers for this use. When this is
241  /// non-empty. The canonical representation of a formula is
242  /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
243  /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
244  /// #1 enforces that the scaled register is always used when at least two
245  /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
246  /// #2 enforces that 1 * reg is reg.
247  /// This invariant can be temporarly broken while building a formula.
248  /// However, every formula inserted into the LSRInstance must be in canonical
249  /// form.
250  SmallVector<const SCEV *, 4> BaseRegs;
251
252  /// ScaledReg - The 'scaled' register for this use. This should be non-null
253  /// when Scale is not zero.
254  const SCEV *ScaledReg;
255
256  /// UnfoldedOffset - An additional constant offset which added near the
257  /// use. This requires a temporary register, but the offset itself can
258  /// live in an add immediate field rather than a register.
259  int64_t UnfoldedOffset;
260
261  Formula()
262      : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0),
263        ScaledReg(nullptr), UnfoldedOffset(0) {}
264
265  void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
266
267  bool isCanonical() const;
268
269  void Canonicalize();
270
271  bool Unscale();
272
273  size_t getNumRegs() const;
274  Type *getType() const;
275
276  void DeleteBaseReg(const SCEV *&S);
277
278  bool referencesReg(const SCEV *S) const;
279  bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
280                                  const RegUseTracker &RegUses) const;
281
282  void print(raw_ostream &OS) const;
283  void dump() const;
284};
285
286}
287
288/// DoInitialMatch - Recursion helper for InitialMatch.
289static void DoInitialMatch(const SCEV *S, Loop *L,
290                           SmallVectorImpl<const SCEV *> &Good,
291                           SmallVectorImpl<const SCEV *> &Bad,
292                           ScalarEvolution &SE) {
293  // Collect expressions which properly dominate the loop header.
294  if (SE.properlyDominates(S, L->getHeader())) {
295    Good.push_back(S);
296    return;
297  }
298
299  // Look at add operands.
300  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
301    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
302         I != E; ++I)
303      DoInitialMatch(*I, L, Good, Bad, SE);
304    return;
305  }
306
307  // Look at addrec operands.
308  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
309    if (!AR->getStart()->isZero()) {
310      DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
311      DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
312                                      AR->getStepRecurrence(SE),
313                                      // FIXME: AR->getNoWrapFlags()
314                                      AR->getLoop(), SCEV::FlagAnyWrap),
315                     L, Good, Bad, SE);
316      return;
317    }
318
319  // Handle a multiplication by -1 (negation) if it didn't fold.
320  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
321    if (Mul->getOperand(0)->isAllOnesValue()) {
322      SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
323      const SCEV *NewMul = SE.getMulExpr(Ops);
324
325      SmallVector<const SCEV *, 4> MyGood;
326      SmallVector<const SCEV *, 4> MyBad;
327      DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
328      const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
329        SE.getEffectiveSCEVType(NewMul->getType())));
330      for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
331           E = MyGood.end(); I != E; ++I)
332        Good.push_back(SE.getMulExpr(NegOne, *I));
333      for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
334           E = MyBad.end(); I != E; ++I)
335        Bad.push_back(SE.getMulExpr(NegOne, *I));
336      return;
337    }
338
339  // Ok, we can't do anything interesting. Just stuff the whole thing into a
340  // register and hope for the best.
341  Bad.push_back(S);
342}
343
344/// InitialMatch - Incorporate loop-variant parts of S into this Formula,
345/// attempting to keep all loop-invariant and loop-computable values in a
346/// single base register.
347void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
348  SmallVector<const SCEV *, 4> Good;
349  SmallVector<const SCEV *, 4> Bad;
350  DoInitialMatch(S, L, Good, Bad, SE);
351  if (!Good.empty()) {
352    const SCEV *Sum = SE.getAddExpr(Good);
353    if (!Sum->isZero())
354      BaseRegs.push_back(Sum);
355    HasBaseReg = true;
356  }
357  if (!Bad.empty()) {
358    const SCEV *Sum = SE.getAddExpr(Bad);
359    if (!Sum->isZero())
360      BaseRegs.push_back(Sum);
361    HasBaseReg = true;
362  }
363  Canonicalize();
364}
365
366/// \brief Check whether or not this formula statisfies the canonical
367/// representation.
368/// \see Formula::BaseRegs.
369bool Formula::isCanonical() const {
370  if (ScaledReg)
371    return Scale != 1 || !BaseRegs.empty();
372  return BaseRegs.size() <= 1;
373}
374
375/// \brief Helper method to morph a formula into its canonical representation.
376/// \see Formula::BaseRegs.
377/// Every formula having more than one base register, must use the ScaledReg
378/// field. Otherwise, we would have to do special cases everywhere in LSR
379/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
380/// On the other hand, 1*reg should be canonicalized into reg.
381void Formula::Canonicalize() {
382  if (isCanonical())
383    return;
384  // So far we did not need this case. This is easy to implement but it is
385  // useless to maintain dead code. Beside it could hurt compile time.
386  assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
387  // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
388  ScaledReg = BaseRegs.back();
389  BaseRegs.pop_back();
390  Scale = 1;
391  size_t BaseRegsSize = BaseRegs.size();
392  size_t Try = 0;
393  // If ScaledReg is an invariant, try to find a variant expression.
394  while (Try < BaseRegsSize && !isa<SCEVAddRecExpr>(ScaledReg))
395    std::swap(ScaledReg, BaseRegs[Try++]);
396}
397
398/// \brief Get rid of the scale in the formula.
399/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
400/// \return true if it was possible to get rid of the scale, false otherwise.
401/// \note After this operation the formula may not be in the canonical form.
402bool Formula::Unscale() {
403  if (Scale != 1)
404    return false;
405  Scale = 0;
406  BaseRegs.push_back(ScaledReg);
407  ScaledReg = nullptr;
408  return true;
409}
410
411/// getNumRegs - Return the total number of register operands used by this
412/// formula. This does not include register uses implied by non-constant
413/// addrec strides.
414size_t Formula::getNumRegs() const {
415  return !!ScaledReg + BaseRegs.size();
416}
417
418/// getType - Return the type of this formula, if it has one, or null
419/// otherwise. This type is meaningless except for the bit size.
420Type *Formula::getType() const {
421  return !BaseRegs.empty() ? BaseRegs.front()->getType() :
422         ScaledReg ? ScaledReg->getType() :
423         BaseGV ? BaseGV->getType() :
424         nullptr;
425}
426
427/// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
428void Formula::DeleteBaseReg(const SCEV *&S) {
429  if (&S != &BaseRegs.back())
430    std::swap(S, BaseRegs.back());
431  BaseRegs.pop_back();
432}
433
434/// referencesReg - Test if this formula references the given register.
435bool Formula::referencesReg(const SCEV *S) const {
436  return S == ScaledReg ||
437         std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
438}
439
440/// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
441/// which are used by uses other than the use with the given index.
442bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
443                                         const RegUseTracker &RegUses) const {
444  if (ScaledReg)
445    if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
446      return true;
447  for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
448       E = BaseRegs.end(); I != E; ++I)
449    if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
450      return true;
451  return false;
452}
453
454void Formula::print(raw_ostream &OS) const {
455  bool First = true;
456  if (BaseGV) {
457    if (!First) OS << " + "; else First = false;
458    BaseGV->printAsOperand(OS, /*PrintType=*/false);
459  }
460  if (BaseOffset != 0) {
461    if (!First) OS << " + "; else First = false;
462    OS << BaseOffset;
463  }
464  for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
465       E = BaseRegs.end(); I != E; ++I) {
466    if (!First) OS << " + "; else First = false;
467    OS << "reg(" << **I << ')';
468  }
469  if (HasBaseReg && BaseRegs.empty()) {
470    if (!First) OS << " + "; else First = false;
471    OS << "**error: HasBaseReg**";
472  } else if (!HasBaseReg && !BaseRegs.empty()) {
473    if (!First) OS << " + "; else First = false;
474    OS << "**error: !HasBaseReg**";
475  }
476  if (Scale != 0) {
477    if (!First) OS << " + "; else First = false;
478    OS << Scale << "*reg(";
479    if (ScaledReg)
480      OS << *ScaledReg;
481    else
482      OS << "<unknown>";
483    OS << ')';
484  }
485  if (UnfoldedOffset != 0) {
486    if (!First) OS << " + ";
487    OS << "imm(" << UnfoldedOffset << ')';
488  }
489}
490
491#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
492void Formula::dump() const {
493  print(errs()); errs() << '\n';
494}
495#endif
496
497/// isAddRecSExtable - Return true if the given addrec can be sign-extended
498/// without changing its value.
499static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
500  Type *WideTy =
501    IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
502  return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
503}
504
505/// isAddSExtable - Return true if the given add can be sign-extended
506/// without changing its value.
507static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
508  Type *WideTy =
509    IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
510  return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
511}
512
513/// isMulSExtable - Return true if the given mul can be sign-extended
514/// without changing its value.
515static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
516  Type *WideTy =
517    IntegerType::get(SE.getContext(),
518                     SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
519  return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
520}
521
522/// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
523/// and if the remainder is known to be zero,  or null otherwise. If
524/// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
525/// to Y, ignoring that the multiplication may overflow, which is useful when
526/// the result will be used in a context where the most significant bits are
527/// ignored.
528static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
529                                ScalarEvolution &SE,
530                                bool IgnoreSignificantBits = false) {
531  // Handle the trivial case, which works for any SCEV type.
532  if (LHS == RHS)
533    return SE.getConstant(LHS->getType(), 1);
534
535  // Handle a few RHS special cases.
536  const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
537  if (RC) {
538    const APInt &RA = RC->getValue()->getValue();
539    // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
540    // some folding.
541    if (RA.isAllOnesValue())
542      return SE.getMulExpr(LHS, RC);
543    // Handle x /s 1 as x.
544    if (RA == 1)
545      return LHS;
546  }
547
548  // Check for a division of a constant by a constant.
549  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
550    if (!RC)
551      return nullptr;
552    const APInt &LA = C->getValue()->getValue();
553    const APInt &RA = RC->getValue()->getValue();
554    if (LA.srem(RA) != 0)
555      return nullptr;
556    return SE.getConstant(LA.sdiv(RA));
557  }
558
559  // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
560  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
561    if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
562      const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
563                                      IgnoreSignificantBits);
564      if (!Step) return nullptr;
565      const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
566                                       IgnoreSignificantBits);
567      if (!Start) return nullptr;
568      // FlagNW is independent of the start value, step direction, and is
569      // preserved with smaller magnitude steps.
570      // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
571      return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
572    }
573    return nullptr;
574  }
575
576  // Distribute the sdiv over add operands, if the add doesn't overflow.
577  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
578    if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
579      SmallVector<const SCEV *, 8> Ops;
580      for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
581           I != E; ++I) {
582        const SCEV *Op = getExactSDiv(*I, RHS, SE,
583                                      IgnoreSignificantBits);
584        if (!Op) return nullptr;
585        Ops.push_back(Op);
586      }
587      return SE.getAddExpr(Ops);
588    }
589    return nullptr;
590  }
591
592  // Check for a multiply operand that we can pull RHS out of.
593  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
594    if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
595      SmallVector<const SCEV *, 4> Ops;
596      bool Found = false;
597      for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
598           I != E; ++I) {
599        const SCEV *S = *I;
600        if (!Found)
601          if (const SCEV *Q = getExactSDiv(S, RHS, SE,
602                                           IgnoreSignificantBits)) {
603            S = Q;
604            Found = true;
605          }
606        Ops.push_back(S);
607      }
608      return Found ? SE.getMulExpr(Ops) : nullptr;
609    }
610    return nullptr;
611  }
612
613  // Otherwise we don't know.
614  return nullptr;
615}
616
617/// ExtractImmediate - If S involves the addition of a constant integer value,
618/// return that integer value, and mutate S to point to a new SCEV with that
619/// value excluded.
620static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
621  if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
622    if (C->getValue()->getValue().getMinSignedBits() <= 64) {
623      S = SE.getConstant(C->getType(), 0);
624      return C->getValue()->getSExtValue();
625    }
626  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
627    SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
628    int64_t Result = ExtractImmediate(NewOps.front(), SE);
629    if (Result != 0)
630      S = SE.getAddExpr(NewOps);
631    return Result;
632  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
633    SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
634    int64_t Result = ExtractImmediate(NewOps.front(), SE);
635    if (Result != 0)
636      S = SE.getAddRecExpr(NewOps, AR->getLoop(),
637                           // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
638                           SCEV::FlagAnyWrap);
639    return Result;
640  }
641  return 0;
642}
643
644/// ExtractSymbol - If S involves the addition of a GlobalValue address,
645/// return that symbol, and mutate S to point to a new SCEV with that
646/// value excluded.
647static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
648  if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
649    if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
650      S = SE.getConstant(GV->getType(), 0);
651      return GV;
652    }
653  } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
654    SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
655    GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
656    if (Result)
657      S = SE.getAddExpr(NewOps);
658    return Result;
659  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
660    SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
661    GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
662    if (Result)
663      S = SE.getAddRecExpr(NewOps, AR->getLoop(),
664                           // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
665                           SCEV::FlagAnyWrap);
666    return Result;
667  }
668  return nullptr;
669}
670
671/// isAddressUse - Returns true if the specified instruction is using the
672/// specified value as an address.
673static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
674  bool isAddress = isa<LoadInst>(Inst);
675  if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
676    if (SI->getOperand(1) == OperandVal)
677      isAddress = true;
678  } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
679    // Addressing modes can also be folded into prefetches and a variety
680    // of intrinsics.
681    switch (II->getIntrinsicID()) {
682      default: break;
683      case Intrinsic::prefetch:
684      case Intrinsic::x86_sse_storeu_ps:
685      case Intrinsic::x86_sse2_storeu_pd:
686      case Intrinsic::x86_sse2_storeu_dq:
687      case Intrinsic::x86_sse2_storel_dq:
688        if (II->getArgOperand(0) == OperandVal)
689          isAddress = true;
690        break;
691    }
692  }
693  return isAddress;
694}
695
696/// getAccessType - Return the type of the memory being accessed.
697static Type *getAccessType(const Instruction *Inst) {
698  Type *AccessTy = Inst->getType();
699  if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
700    AccessTy = SI->getOperand(0)->getType();
701  else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
702    // Addressing modes can also be folded into prefetches and a variety
703    // of intrinsics.
704    switch (II->getIntrinsicID()) {
705    default: break;
706    case Intrinsic::x86_sse_storeu_ps:
707    case Intrinsic::x86_sse2_storeu_pd:
708    case Intrinsic::x86_sse2_storeu_dq:
709    case Intrinsic::x86_sse2_storel_dq:
710      AccessTy = II->getArgOperand(0)->getType();
711      break;
712    }
713  }
714
715  // All pointers have the same requirements, so canonicalize them to an
716  // arbitrary pointer type to minimize variation.
717  if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
718    AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
719                                PTy->getAddressSpace());
720
721  return AccessTy;
722}
723
724/// isExistingPhi - Return true if this AddRec is already a phi in its loop.
725static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
726  for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
727       PHINode *PN = dyn_cast<PHINode>(I); ++I) {
728    if (SE.isSCEVable(PN->getType()) &&
729        (SE.getEffectiveSCEVType(PN->getType()) ==
730         SE.getEffectiveSCEVType(AR->getType())) &&
731        SE.getSCEV(PN) == AR)
732      return true;
733  }
734  return false;
735}
736
737/// Check if expanding this expression is likely to incur significant cost. This
738/// is tricky because SCEV doesn't track which expressions are actually computed
739/// by the current IR.
740///
741/// We currently allow expansion of IV increments that involve adds,
742/// multiplication by constants, and AddRecs from existing phis.
743///
744/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
745/// obvious multiple of the UDivExpr.
746static bool isHighCostExpansion(const SCEV *S,
747                                SmallPtrSet<const SCEV*, 8> &Processed,
748                                ScalarEvolution &SE) {
749  // Zero/One operand expressions
750  switch (S->getSCEVType()) {
751  case scUnknown:
752  case scConstant:
753    return false;
754  case scTruncate:
755    return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
756                               Processed, SE);
757  case scZeroExtend:
758    return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
759                               Processed, SE);
760  case scSignExtend:
761    return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
762                               Processed, SE);
763  }
764
765  if (!Processed.insert(S))
766    return false;
767
768  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
769    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
770         I != E; ++I) {
771      if (isHighCostExpansion(*I, Processed, SE))
772        return true;
773    }
774    return false;
775  }
776
777  if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
778    if (Mul->getNumOperands() == 2) {
779      // Multiplication by a constant is ok
780      if (isa<SCEVConstant>(Mul->getOperand(0)))
781        return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
782
783      // If we have the value of one operand, check if an existing
784      // multiplication already generates this expression.
785      if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
786        Value *UVal = U->getValue();
787        for (User *UR : UVal->users()) {
788          // If U is a constant, it may be used by a ConstantExpr.
789          Instruction *UI = dyn_cast<Instruction>(UR);
790          if (UI && UI->getOpcode() == Instruction::Mul &&
791              SE.isSCEVable(UI->getType())) {
792            return SE.getSCEV(UI) == Mul;
793          }
794        }
795      }
796    }
797  }
798
799  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
800    if (isExistingPhi(AR, SE))
801      return false;
802  }
803
804  // Fow now, consider any other type of expression (div/mul/min/max) high cost.
805  return true;
806}
807
808/// DeleteTriviallyDeadInstructions - If any of the instructions is the
809/// specified set are trivially dead, delete them and see if this makes any of
810/// their operands subsequently dead.
811static bool
812DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
813  bool Changed = false;
814
815  while (!DeadInsts.empty()) {
816    Value *V = DeadInsts.pop_back_val();
817    Instruction *I = dyn_cast_or_null<Instruction>(V);
818
819    if (!I || !isInstructionTriviallyDead(I))
820      continue;
821
822    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
823      if (Instruction *U = dyn_cast<Instruction>(*OI)) {
824        *OI = nullptr;
825        if (U->use_empty())
826          DeadInsts.push_back(U);
827      }
828
829    I->eraseFromParent();
830    Changed = true;
831  }
832
833  return Changed;
834}
835
836namespace {
837class LSRUse;
838}
839
840/// \brief Check if the addressing mode defined by \p F is completely
841/// folded in \p LU at isel time.
842/// This includes address-mode folding and special icmp tricks.
843/// This function returns true if \p LU can accommodate what \p F
844/// defines and up to 1 base + 1 scaled + offset.
845/// In other words, if \p F has several base registers, this function may
846/// still return true. Therefore, users still need to account for
847/// additional base registers and/or unfolded offsets to derive an
848/// accurate cost model.
849static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
850                                 const LSRUse &LU, const Formula &F);
851// Get the cost of the scaling factor used in F for LU.
852static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
853                                     const LSRUse &LU, const Formula &F);
854
855namespace {
856
857/// Cost - This class is used to measure and compare candidate formulae.
858class Cost {
859  /// TODO: Some of these could be merged. Also, a lexical ordering
860  /// isn't always optimal.
861  unsigned NumRegs;
862  unsigned AddRecCost;
863  unsigned NumIVMuls;
864  unsigned NumBaseAdds;
865  unsigned ImmCost;
866  unsigned SetupCost;
867  unsigned ScaleCost;
868
869public:
870  Cost()
871    : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
872      SetupCost(0), ScaleCost(0) {}
873
874  bool operator<(const Cost &Other) const;
875
876  void Lose();
877
878#ifndef NDEBUG
879  // Once any of the metrics loses, they must all remain losers.
880  bool isValid() {
881    return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
882             | ImmCost | SetupCost | ScaleCost) != ~0u)
883      || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
884           & ImmCost & SetupCost & ScaleCost) == ~0u);
885  }
886#endif
887
888  bool isLoser() {
889    assert(isValid() && "invalid cost");
890    return NumRegs == ~0u;
891  }
892
893  void RateFormula(const TargetTransformInfo &TTI,
894                   const Formula &F,
895                   SmallPtrSet<const SCEV *, 16> &Regs,
896                   const DenseSet<const SCEV *> &VisitedRegs,
897                   const Loop *L,
898                   const SmallVectorImpl<int64_t> &Offsets,
899                   ScalarEvolution &SE, DominatorTree &DT,
900                   const LSRUse &LU,
901                   SmallPtrSet<const SCEV *, 16> *LoserRegs = nullptr);
902
903  void print(raw_ostream &OS) const;
904  void dump() const;
905
906private:
907  void RateRegister(const SCEV *Reg,
908                    SmallPtrSet<const SCEV *, 16> &Regs,
909                    const Loop *L,
910                    ScalarEvolution &SE, DominatorTree &DT);
911  void RatePrimaryRegister(const SCEV *Reg,
912                           SmallPtrSet<const SCEV *, 16> &Regs,
913                           const Loop *L,
914                           ScalarEvolution &SE, DominatorTree &DT,
915                           SmallPtrSet<const SCEV *, 16> *LoserRegs);
916};
917
918}
919
920/// RateRegister - Tally up interesting quantities from the given register.
921void Cost::RateRegister(const SCEV *Reg,
922                        SmallPtrSet<const SCEV *, 16> &Regs,
923                        const Loop *L,
924                        ScalarEvolution &SE, DominatorTree &DT) {
925  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
926    // If this is an addrec for another loop, don't second-guess its addrec phi
927    // nodes. LSR isn't currently smart enough to reason about more than one
928    // loop at a time. LSR has already run on inner loops, will not run on outer
929    // loops, and cannot be expected to change sibling loops.
930    if (AR->getLoop() != L) {
931      // If the AddRec exists, consider it's register free and leave it alone.
932      if (isExistingPhi(AR, SE))
933        return;
934
935      // Otherwise, do not consider this formula at all.
936      Lose();
937      return;
938    }
939    AddRecCost += 1; /// TODO: This should be a function of the stride.
940
941    // Add the step value register, if it needs one.
942    // TODO: The non-affine case isn't precisely modeled here.
943    if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
944      if (!Regs.count(AR->getOperand(1))) {
945        RateRegister(AR->getOperand(1), Regs, L, SE, DT);
946        if (isLoser())
947          return;
948      }
949    }
950  }
951  ++NumRegs;
952
953  // Rough heuristic; favor registers which don't require extra setup
954  // instructions in the preheader.
955  if (!isa<SCEVUnknown>(Reg) &&
956      !isa<SCEVConstant>(Reg) &&
957      !(isa<SCEVAddRecExpr>(Reg) &&
958        (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
959         isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
960    ++SetupCost;
961
962    NumIVMuls += isa<SCEVMulExpr>(Reg) &&
963                 SE.hasComputableLoopEvolution(Reg, L);
964}
965
966/// RatePrimaryRegister - Record this register in the set. If we haven't seen it
967/// before, rate it. Optional LoserRegs provides a way to declare any formula
968/// that refers to one of those regs an instant loser.
969void Cost::RatePrimaryRegister(const SCEV *Reg,
970                               SmallPtrSet<const SCEV *, 16> &Regs,
971                               const Loop *L,
972                               ScalarEvolution &SE, DominatorTree &DT,
973                               SmallPtrSet<const SCEV *, 16> *LoserRegs) {
974  if (LoserRegs && LoserRegs->count(Reg)) {
975    Lose();
976    return;
977  }
978  if (Regs.insert(Reg)) {
979    RateRegister(Reg, Regs, L, SE, DT);
980    if (LoserRegs && isLoser())
981      LoserRegs->insert(Reg);
982  }
983}
984
985void Cost::RateFormula(const TargetTransformInfo &TTI,
986                       const Formula &F,
987                       SmallPtrSet<const SCEV *, 16> &Regs,
988                       const DenseSet<const SCEV *> &VisitedRegs,
989                       const Loop *L,
990                       const SmallVectorImpl<int64_t> &Offsets,
991                       ScalarEvolution &SE, DominatorTree &DT,
992                       const LSRUse &LU,
993                       SmallPtrSet<const SCEV *, 16> *LoserRegs) {
994  assert(F.isCanonical() && "Cost is accurate only for canonical formula");
995  // Tally up the registers.
996  if (const SCEV *ScaledReg = F.ScaledReg) {
997    if (VisitedRegs.count(ScaledReg)) {
998      Lose();
999      return;
1000    }
1001    RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1002    if (isLoser())
1003      return;
1004  }
1005  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
1006       E = F.BaseRegs.end(); I != E; ++I) {
1007    const SCEV *BaseReg = *I;
1008    if (VisitedRegs.count(BaseReg)) {
1009      Lose();
1010      return;
1011    }
1012    RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1013    if (isLoser())
1014      return;
1015  }
1016
1017  // Determine how many (unfolded) adds we'll need inside the loop.
1018  size_t NumBaseParts = F.getNumRegs();
1019  if (NumBaseParts > 1)
1020    // Do not count the base and a possible second register if the target
1021    // allows to fold 2 registers.
1022    NumBaseAdds +=
1023        NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1024  NumBaseAdds += (F.UnfoldedOffset != 0);
1025
1026  // Accumulate non-free scaling amounts.
1027  ScaleCost += getScalingFactorCost(TTI, LU, F);
1028
1029  // Tally up the non-zero immediates.
1030  for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1031       E = Offsets.end(); I != E; ++I) {
1032    int64_t Offset = (uint64_t)*I + F.BaseOffset;
1033    if (F.BaseGV)
1034      ImmCost += 64; // Handle symbolic values conservatively.
1035                     // TODO: This should probably be the pointer size.
1036    else if (Offset != 0)
1037      ImmCost += APInt(64, Offset, true).getMinSignedBits();
1038  }
1039  assert(isValid() && "invalid cost");
1040}
1041
1042/// Lose - Set this cost to a losing value.
1043void Cost::Lose() {
1044  NumRegs = ~0u;
1045  AddRecCost = ~0u;
1046  NumIVMuls = ~0u;
1047  NumBaseAdds = ~0u;
1048  ImmCost = ~0u;
1049  SetupCost = ~0u;
1050  ScaleCost = ~0u;
1051}
1052
1053/// operator< - Choose the lower cost.
1054bool Cost::operator<(const Cost &Other) const {
1055  return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost,
1056                  ImmCost, SetupCost) <
1057         std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls,
1058                  Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost,
1059                  Other.SetupCost);
1060}
1061
1062void Cost::print(raw_ostream &OS) const {
1063  OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
1064  if (AddRecCost != 0)
1065    OS << ", with addrec cost " << AddRecCost;
1066  if (NumIVMuls != 0)
1067    OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
1068  if (NumBaseAdds != 0)
1069    OS << ", plus " << NumBaseAdds << " base add"
1070       << (NumBaseAdds == 1 ? "" : "s");
1071  if (ScaleCost != 0)
1072    OS << ", plus " << ScaleCost << " scale cost";
1073  if (ImmCost != 0)
1074    OS << ", plus " << ImmCost << " imm cost";
1075  if (SetupCost != 0)
1076    OS << ", plus " << SetupCost << " setup cost";
1077}
1078
1079#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1080void Cost::dump() const {
1081  print(errs()); errs() << '\n';
1082}
1083#endif
1084
1085namespace {
1086
1087/// LSRFixup - An operand value in an instruction which is to be replaced
1088/// with some equivalent, possibly strength-reduced, replacement.
1089struct LSRFixup {
1090  /// UserInst - The instruction which will be updated.
1091  Instruction *UserInst;
1092
1093  /// OperandValToReplace - The operand of the instruction which will
1094  /// be replaced. The operand may be used more than once; every instance
1095  /// will be replaced.
1096  Value *OperandValToReplace;
1097
1098  /// PostIncLoops - If this user is to use the post-incremented value of an
1099  /// induction variable, this variable is non-null and holds the loop
1100  /// associated with the induction variable.
1101  PostIncLoopSet PostIncLoops;
1102
1103  /// LUIdx - The index of the LSRUse describing the expression which
1104  /// this fixup needs, minus an offset (below).
1105  size_t LUIdx;
1106
1107  /// Offset - A constant offset to be added to the LSRUse expression.
1108  /// This allows multiple fixups to share the same LSRUse with different
1109  /// offsets, for example in an unrolled loop.
1110  int64_t Offset;
1111
1112  bool isUseFullyOutsideLoop(const Loop *L) const;
1113
1114  LSRFixup();
1115
1116  void print(raw_ostream &OS) const;
1117  void dump() const;
1118};
1119
1120}
1121
1122LSRFixup::LSRFixup()
1123  : UserInst(nullptr), OperandValToReplace(nullptr), LUIdx(~size_t(0)),
1124    Offset(0) {}
1125
1126/// isUseFullyOutsideLoop - Test whether this fixup always uses its
1127/// value outside of the given loop.
1128bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1129  // PHI nodes use their value in their incoming blocks.
1130  if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1131    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1132      if (PN->getIncomingValue(i) == OperandValToReplace &&
1133          L->contains(PN->getIncomingBlock(i)))
1134        return false;
1135    return true;
1136  }
1137
1138  return !L->contains(UserInst);
1139}
1140
1141void LSRFixup::print(raw_ostream &OS) const {
1142  OS << "UserInst=";
1143  // Store is common and interesting enough to be worth special-casing.
1144  if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1145    OS << "store ";
1146    Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1147  } else if (UserInst->getType()->isVoidTy())
1148    OS << UserInst->getOpcodeName();
1149  else
1150    UserInst->printAsOperand(OS, /*PrintType=*/false);
1151
1152  OS << ", OperandValToReplace=";
1153  OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1154
1155  for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
1156       E = PostIncLoops.end(); I != E; ++I) {
1157    OS << ", PostIncLoop=";
1158    (*I)->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1159  }
1160
1161  if (LUIdx != ~size_t(0))
1162    OS << ", LUIdx=" << LUIdx;
1163
1164  if (Offset != 0)
1165    OS << ", Offset=" << Offset;
1166}
1167
1168#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1169void LSRFixup::dump() const {
1170  print(errs()); errs() << '\n';
1171}
1172#endif
1173
1174namespace {
1175
1176/// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
1177/// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
1178struct UniquifierDenseMapInfo {
1179  static SmallVector<const SCEV *, 4> getEmptyKey() {
1180    SmallVector<const SCEV *, 4>  V;
1181    V.push_back(reinterpret_cast<const SCEV *>(-1));
1182    return V;
1183  }
1184
1185  static SmallVector<const SCEV *, 4> getTombstoneKey() {
1186    SmallVector<const SCEV *, 4> V;
1187    V.push_back(reinterpret_cast<const SCEV *>(-2));
1188    return V;
1189  }
1190
1191  static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1192    return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1193  }
1194
1195  static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1196                      const SmallVector<const SCEV *, 4> &RHS) {
1197    return LHS == RHS;
1198  }
1199};
1200
1201/// LSRUse - This class holds the state that LSR keeps for each use in
1202/// IVUsers, as well as uses invented by LSR itself. It includes information
1203/// about what kinds of things can be folded into the user, information about
1204/// the user itself, and information about how the use may be satisfied.
1205/// TODO: Represent multiple users of the same expression in common?
1206class LSRUse {
1207  DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1208
1209public:
1210  /// KindType - An enum for a kind of use, indicating what types of
1211  /// scaled and immediate operands it might support.
1212  enum KindType {
1213    Basic,   ///< A normal use, with no folding.
1214    Special, ///< A special case of basic, allowing -1 scales.
1215    Address, ///< An address use; folding according to TargetLowering
1216    ICmpZero ///< An equality icmp with both operands folded into one.
1217    // TODO: Add a generic icmp too?
1218  };
1219
1220  typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair;
1221
1222  KindType Kind;
1223  Type *AccessTy;
1224
1225  SmallVector<int64_t, 8> Offsets;
1226  int64_t MinOffset;
1227  int64_t MaxOffset;
1228
1229  /// AllFixupsOutsideLoop - This records whether all of the fixups using this
1230  /// LSRUse are outside of the loop, in which case some special-case heuristics
1231  /// may be used.
1232  bool AllFixupsOutsideLoop;
1233
1234  /// RigidFormula is set to true to guarantee that this use will be associated
1235  /// with a single formula--the one that initially matched. Some SCEV
1236  /// expressions cannot be expanded. This allows LSR to consider the registers
1237  /// used by those expressions without the need to expand them later after
1238  /// changing the formula.
1239  bool RigidFormula;
1240
1241  /// WidestFixupType - This records the widest use type for any fixup using
1242  /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
1243  /// max fixup widths to be equivalent, because the narrower one may be relying
1244  /// on the implicit truncation to truncate away bogus bits.
1245  Type *WidestFixupType;
1246
1247  /// Formulae - A list of ways to build a value that can satisfy this user.
1248  /// After the list is populated, one of these is selected heuristically and
1249  /// used to formulate a replacement for OperandValToReplace in UserInst.
1250  SmallVector<Formula, 12> Formulae;
1251
1252  /// Regs - The set of register candidates used by all formulae in this LSRUse.
1253  SmallPtrSet<const SCEV *, 4> Regs;
1254
1255  LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
1256                                      MinOffset(INT64_MAX),
1257                                      MaxOffset(INT64_MIN),
1258                                      AllFixupsOutsideLoop(true),
1259                                      RigidFormula(false),
1260                                      WidestFixupType(nullptr) {}
1261
1262  bool HasFormulaWithSameRegs(const Formula &F) const;
1263  bool InsertFormula(const Formula &F);
1264  void DeleteFormula(Formula &F);
1265  void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1266
1267  void print(raw_ostream &OS) const;
1268  void dump() const;
1269};
1270
1271}
1272
1273/// HasFormula - Test whether this use as a formula which has the same
1274/// registers as the given formula.
1275bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1276  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1277  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1278  // Unstable sort by host order ok, because this is only used for uniquifying.
1279  std::sort(Key.begin(), Key.end());
1280  return Uniquifier.count(Key);
1281}
1282
1283/// InsertFormula - If the given formula has not yet been inserted, add it to
1284/// the list, and return true. Return false otherwise.
1285/// The formula must be in canonical form.
1286bool LSRUse::InsertFormula(const Formula &F) {
1287  assert(F.isCanonical() && "Invalid canonical representation");
1288
1289  if (!Formulae.empty() && RigidFormula)
1290    return false;
1291
1292  SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1293  if (F.ScaledReg) Key.push_back(F.ScaledReg);
1294  // Unstable sort by host order ok, because this is only used for uniquifying.
1295  std::sort(Key.begin(), Key.end());
1296
1297  if (!Uniquifier.insert(Key).second)
1298    return false;
1299
1300  // Using a register to hold the value of 0 is not profitable.
1301  assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1302         "Zero allocated in a scaled register!");
1303#ifndef NDEBUG
1304  for (SmallVectorImpl<const SCEV *>::const_iterator I =
1305       F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1306    assert(!(*I)->isZero() && "Zero allocated in a base register!");
1307#endif
1308
1309  // Add the formula to the list.
1310  Formulae.push_back(F);
1311
1312  // Record registers now being used by this use.
1313  Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1314  if (F.ScaledReg)
1315    Regs.insert(F.ScaledReg);
1316
1317  return true;
1318}
1319
1320/// DeleteFormula - Remove the given formula from this use's list.
1321void LSRUse::DeleteFormula(Formula &F) {
1322  if (&F != &Formulae.back())
1323    std::swap(F, Formulae.back());
1324  Formulae.pop_back();
1325}
1326
1327/// RecomputeRegs - Recompute the Regs field, and update RegUses.
1328void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1329  // Now that we've filtered out some formulae, recompute the Regs set.
1330  SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
1331  Regs.clear();
1332  for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
1333       E = Formulae.end(); I != E; ++I) {
1334    const Formula &F = *I;
1335    if (F.ScaledReg) Regs.insert(F.ScaledReg);
1336    Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1337  }
1338
1339  // Update the RegTracker.
1340  for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
1341       E = OldRegs.end(); I != E; ++I)
1342    if (!Regs.count(*I))
1343      RegUses.DropRegister(*I, LUIdx);
1344}
1345
1346void LSRUse::print(raw_ostream &OS) const {
1347  OS << "LSR Use: Kind=";
1348  switch (Kind) {
1349  case Basic:    OS << "Basic"; break;
1350  case Special:  OS << "Special"; break;
1351  case ICmpZero: OS << "ICmpZero"; break;
1352  case Address:
1353    OS << "Address of ";
1354    if (AccessTy->isPointerTy())
1355      OS << "pointer"; // the full pointer type could be really verbose
1356    else
1357      OS << *AccessTy;
1358  }
1359
1360  OS << ", Offsets={";
1361  for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1362       E = Offsets.end(); I != E; ++I) {
1363    OS << *I;
1364    if (std::next(I) != E)
1365      OS << ',';
1366  }
1367  OS << '}';
1368
1369  if (AllFixupsOutsideLoop)
1370    OS << ", all-fixups-outside-loop";
1371
1372  if (WidestFixupType)
1373    OS << ", widest fixup type: " << *WidestFixupType;
1374}
1375
1376#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1377void LSRUse::dump() const {
1378  print(errs()); errs() << '\n';
1379}
1380#endif
1381
1382static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1383                                 LSRUse::KindType Kind, Type *AccessTy,
1384                                 GlobalValue *BaseGV, int64_t BaseOffset,
1385                                 bool HasBaseReg, int64_t Scale) {
1386  switch (Kind) {
1387  case LSRUse::Address:
1388    return TTI.isLegalAddressingMode(AccessTy, BaseGV, BaseOffset, HasBaseReg, Scale);
1389
1390    // Otherwise, just guess that reg+reg addressing is legal.
1391    //return ;
1392
1393  case LSRUse::ICmpZero:
1394    // There's not even a target hook for querying whether it would be legal to
1395    // fold a GV into an ICmp.
1396    if (BaseGV)
1397      return false;
1398
1399    // ICmp only has two operands; don't allow more than two non-trivial parts.
1400    if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1401      return false;
1402
1403    // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1404    // putting the scaled register in the other operand of the icmp.
1405    if (Scale != 0 && Scale != -1)
1406      return false;
1407
1408    // If we have low-level target information, ask the target if it can fold an
1409    // integer immediate on an icmp.
1410    if (BaseOffset != 0) {
1411      // We have one of:
1412      // ICmpZero     BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1413      // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1414      // Offs is the ICmp immediate.
1415      if (Scale == 0)
1416        // The cast does the right thing with INT64_MIN.
1417        BaseOffset = -(uint64_t)BaseOffset;
1418      return TTI.isLegalICmpImmediate(BaseOffset);
1419    }
1420
1421    // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1422    return true;
1423
1424  case LSRUse::Basic:
1425    // Only handle single-register values.
1426    return !BaseGV && Scale == 0 && BaseOffset == 0;
1427
1428  case LSRUse::Special:
1429    // Special case Basic to handle -1 scales.
1430    return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1431  }
1432
1433  llvm_unreachable("Invalid LSRUse Kind!");
1434}
1435
1436static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1437                                 int64_t MinOffset, int64_t MaxOffset,
1438                                 LSRUse::KindType Kind, Type *AccessTy,
1439                                 GlobalValue *BaseGV, int64_t BaseOffset,
1440                                 bool HasBaseReg, int64_t Scale) {
1441  // Check for overflow.
1442  if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1443      (MinOffset > 0))
1444    return false;
1445  MinOffset = (uint64_t)BaseOffset + MinOffset;
1446  if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1447      (MaxOffset > 0))
1448    return false;
1449  MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1450
1451  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1452                              HasBaseReg, Scale) &&
1453         isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1454                              HasBaseReg, Scale);
1455}
1456
1457static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1458                                 int64_t MinOffset, int64_t MaxOffset,
1459                                 LSRUse::KindType Kind, Type *AccessTy,
1460                                 const Formula &F) {
1461  // For the purpose of isAMCompletelyFolded either having a canonical formula
1462  // or a scale not equal to zero is correct.
1463  // Problems may arise from non canonical formulae having a scale == 0.
1464  // Strictly speaking it would best to just rely on canonical formulae.
1465  // However, when we generate the scaled formulae, we first check that the
1466  // scaling factor is profitable before computing the actual ScaledReg for
1467  // compile time sake.
1468  assert((F.isCanonical() || F.Scale != 0));
1469  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1470                              F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1471}
1472
1473/// isLegalUse - Test whether we know how to expand the current formula.
1474static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1475                       int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1476                       GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg,
1477                       int64_t Scale) {
1478  // We know how to expand completely foldable formulae.
1479  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1480                              BaseOffset, HasBaseReg, Scale) ||
1481         // Or formulae that use a base register produced by a sum of base
1482         // registers.
1483         (Scale == 1 &&
1484          isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1485                               BaseGV, BaseOffset, true, 0));
1486}
1487
1488static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1489                       int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1490                       const Formula &F) {
1491  return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1492                    F.BaseOffset, F.HasBaseReg, F.Scale);
1493}
1494
1495static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1496                                 const LSRUse &LU, const Formula &F) {
1497  return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1498                              LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1499                              F.Scale);
1500}
1501
1502static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1503                                     const LSRUse &LU, const Formula &F) {
1504  if (!F.Scale)
1505    return 0;
1506
1507  // If the use is not completely folded in that instruction, we will have to
1508  // pay an extra cost only for scale != 1.
1509  if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1510                            LU.AccessTy, F))
1511    return F.Scale != 1;
1512
1513  switch (LU.Kind) {
1514  case LSRUse::Address: {
1515    // Check the scaling factor cost with both the min and max offsets.
1516    int ScaleCostMinOffset =
1517      TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1518                               F.BaseOffset + LU.MinOffset,
1519                               F.HasBaseReg, F.Scale);
1520    int ScaleCostMaxOffset =
1521      TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1522                               F.BaseOffset + LU.MaxOffset,
1523                               F.HasBaseReg, F.Scale);
1524
1525    assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1526           "Legal addressing mode has an illegal cost!");
1527    return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1528  }
1529  case LSRUse::ICmpZero:
1530  case LSRUse::Basic:
1531  case LSRUse::Special:
1532    // The use is completely folded, i.e., everything is folded into the
1533    // instruction.
1534    return 0;
1535  }
1536
1537  llvm_unreachable("Invalid LSRUse Kind!");
1538}
1539
1540static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1541                             LSRUse::KindType Kind, Type *AccessTy,
1542                             GlobalValue *BaseGV, int64_t BaseOffset,
1543                             bool HasBaseReg) {
1544  // Fast-path: zero is always foldable.
1545  if (BaseOffset == 0 && !BaseGV) return true;
1546
1547  // Conservatively, create an address with an immediate and a
1548  // base and a scale.
1549  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1550
1551  // Canonicalize a scale of 1 to a base register if the formula doesn't
1552  // already have a base register.
1553  if (!HasBaseReg && Scale == 1) {
1554    Scale = 0;
1555    HasBaseReg = true;
1556  }
1557
1558  return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1559                              HasBaseReg, Scale);
1560}
1561
1562static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1563                             ScalarEvolution &SE, int64_t MinOffset,
1564                             int64_t MaxOffset, LSRUse::KindType Kind,
1565                             Type *AccessTy, const SCEV *S, bool HasBaseReg) {
1566  // Fast-path: zero is always foldable.
1567  if (S->isZero()) return true;
1568
1569  // Conservatively, create an address with an immediate and a
1570  // base and a scale.
1571  int64_t BaseOffset = ExtractImmediate(S, SE);
1572  GlobalValue *BaseGV = ExtractSymbol(S, SE);
1573
1574  // If there's anything else involved, it's not foldable.
1575  if (!S->isZero()) return false;
1576
1577  // Fast-path: zero is always foldable.
1578  if (BaseOffset == 0 && !BaseGV) return true;
1579
1580  // Conservatively, create an address with an immediate and a
1581  // base and a scale.
1582  int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1583
1584  return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1585                              BaseOffset, HasBaseReg, Scale);
1586}
1587
1588namespace {
1589
1590/// IVInc - An individual increment in a Chain of IV increments.
1591/// Relate an IV user to an expression that computes the IV it uses from the IV
1592/// used by the previous link in the Chain.
1593///
1594/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1595/// original IVOperand. The head of the chain's IVOperand is only valid during
1596/// chain collection, before LSR replaces IV users. During chain generation,
1597/// IncExpr can be used to find the new IVOperand that computes the same
1598/// expression.
1599struct IVInc {
1600  Instruction *UserInst;
1601  Value* IVOperand;
1602  const SCEV *IncExpr;
1603
1604  IVInc(Instruction *U, Value *O, const SCEV *E):
1605    UserInst(U), IVOperand(O), IncExpr(E) {}
1606};
1607
1608// IVChain - The list of IV increments in program order.
1609// We typically add the head of a chain without finding subsequent links.
1610struct IVChain {
1611  SmallVector<IVInc,1> Incs;
1612  const SCEV *ExprBase;
1613
1614  IVChain() : ExprBase(nullptr) {}
1615
1616  IVChain(const IVInc &Head, const SCEV *Base)
1617    : Incs(1, Head), ExprBase(Base) {}
1618
1619  typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1620
1621  // begin - return the first increment in the chain.
1622  const_iterator begin() const {
1623    assert(!Incs.empty());
1624    return std::next(Incs.begin());
1625  }
1626  const_iterator end() const {
1627    return Incs.end();
1628  }
1629
1630  // hasIncs - Returns true if this chain contains any increments.
1631  bool hasIncs() const { return Incs.size() >= 2; }
1632
1633  // add - Add an IVInc to the end of this chain.
1634  void add(const IVInc &X) { Incs.push_back(X); }
1635
1636  // tailUserInst - Returns the last UserInst in the chain.
1637  Instruction *tailUserInst() const { return Incs.back().UserInst; }
1638
1639  // isProfitableIncrement - Returns true if IncExpr can be profitably added to
1640  // this chain.
1641  bool isProfitableIncrement(const SCEV *OperExpr,
1642                             const SCEV *IncExpr,
1643                             ScalarEvolution&);
1644};
1645
1646/// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1647/// Distinguish between FarUsers that definitely cross IV increments and
1648/// NearUsers that may be used between IV increments.
1649struct ChainUsers {
1650  SmallPtrSet<Instruction*, 4> FarUsers;
1651  SmallPtrSet<Instruction*, 4> NearUsers;
1652};
1653
1654/// LSRInstance - This class holds state for the main loop strength reduction
1655/// logic.
1656class LSRInstance {
1657  IVUsers &IU;
1658  ScalarEvolution &SE;
1659  DominatorTree &DT;
1660  LoopInfo &LI;
1661  const TargetTransformInfo &TTI;
1662  Loop *const L;
1663  bool Changed;
1664
1665  /// IVIncInsertPos - This is the insert position that the current loop's
1666  /// induction variable increment should be placed. In simple loops, this is
1667  /// the latch block's terminator. But in more complicated cases, this is a
1668  /// position which will dominate all the in-loop post-increment users.
1669  Instruction *IVIncInsertPos;
1670
1671  /// Factors - Interesting factors between use strides.
1672  SmallSetVector<int64_t, 8> Factors;
1673
1674  /// Types - Interesting use types, to facilitate truncation reuse.
1675  SmallSetVector<Type *, 4> Types;
1676
1677  /// Fixups - The list of operands which are to be replaced.
1678  SmallVector<LSRFixup, 16> Fixups;
1679
1680  /// Uses - The list of interesting uses.
1681  SmallVector<LSRUse, 16> Uses;
1682
1683  /// RegUses - Track which uses use which register candidates.
1684  RegUseTracker RegUses;
1685
1686  // Limit the number of chains to avoid quadratic behavior. We don't expect to
1687  // have more than a few IV increment chains in a loop. Missing a Chain falls
1688  // back to normal LSR behavior for those uses.
1689  static const unsigned MaxChains = 8;
1690
1691  /// IVChainVec - IV users can form a chain of IV increments.
1692  SmallVector<IVChain, MaxChains> IVChainVec;
1693
1694  /// IVIncSet - IV users that belong to profitable IVChains.
1695  SmallPtrSet<Use*, MaxChains> IVIncSet;
1696
1697  void OptimizeShadowIV();
1698  bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1699  ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1700  void OptimizeLoopTermCond();
1701
1702  void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1703                        SmallVectorImpl<ChainUsers> &ChainUsersVec);
1704  void FinalizeChain(IVChain &Chain);
1705  void CollectChains();
1706  void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1707                       SmallVectorImpl<WeakVH> &DeadInsts);
1708
1709  void CollectInterestingTypesAndFactors();
1710  void CollectFixupsAndInitialFormulae();
1711
1712  LSRFixup &getNewFixup() {
1713    Fixups.push_back(LSRFixup());
1714    return Fixups.back();
1715  }
1716
1717  // Support for sharing of LSRUses between LSRFixups.
1718  typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy;
1719  UseMapTy UseMap;
1720
1721  bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1722                          LSRUse::KindType Kind, Type *AccessTy);
1723
1724  std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1725                                    LSRUse::KindType Kind,
1726                                    Type *AccessTy);
1727
1728  void DeleteUse(LSRUse &LU, size_t LUIdx);
1729
1730  LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1731
1732  void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1733  void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1734  void CountRegisters(const Formula &F, size_t LUIdx);
1735  bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1736
1737  void CollectLoopInvariantFixupsAndFormulae();
1738
1739  void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1740                              unsigned Depth = 0);
1741
1742  void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1743                                  const Formula &Base, unsigned Depth,
1744                                  size_t Idx, bool IsScaledReg = false);
1745  void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1746  void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1747                                   const Formula &Base, size_t Idx,
1748                                   bool IsScaledReg = false);
1749  void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1750  void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1751                                   const Formula &Base,
1752                                   const SmallVectorImpl<int64_t> &Worklist,
1753                                   size_t Idx, bool IsScaledReg = false);
1754  void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1755  void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1756  void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1757  void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1758  void GenerateCrossUseConstantOffsets();
1759  void GenerateAllReuseFormulae();
1760
1761  void FilterOutUndesirableDedicatedRegisters();
1762
1763  size_t EstimateSearchSpaceComplexity() const;
1764  void NarrowSearchSpaceByDetectingSupersets();
1765  void NarrowSearchSpaceByCollapsingUnrolledCode();
1766  void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1767  void NarrowSearchSpaceByPickingWinnerRegs();
1768  void NarrowSearchSpaceUsingHeuristics();
1769
1770  void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1771                    Cost &SolutionCost,
1772                    SmallVectorImpl<const Formula *> &Workspace,
1773                    const Cost &CurCost,
1774                    const SmallPtrSet<const SCEV *, 16> &CurRegs,
1775                    DenseSet<const SCEV *> &VisitedRegs) const;
1776  void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1777
1778  BasicBlock::iterator
1779    HoistInsertPosition(BasicBlock::iterator IP,
1780                        const SmallVectorImpl<Instruction *> &Inputs) const;
1781  BasicBlock::iterator
1782    AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1783                                  const LSRFixup &LF,
1784                                  const LSRUse &LU,
1785                                  SCEVExpander &Rewriter) const;
1786
1787  Value *Expand(const LSRFixup &LF,
1788                const Formula &F,
1789                BasicBlock::iterator IP,
1790                SCEVExpander &Rewriter,
1791                SmallVectorImpl<WeakVH> &DeadInsts) const;
1792  void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1793                     const Formula &F,
1794                     SCEVExpander &Rewriter,
1795                     SmallVectorImpl<WeakVH> &DeadInsts,
1796                     Pass *P) const;
1797  void Rewrite(const LSRFixup &LF,
1798               const Formula &F,
1799               SCEVExpander &Rewriter,
1800               SmallVectorImpl<WeakVH> &DeadInsts,
1801               Pass *P) const;
1802  void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1803                         Pass *P);
1804
1805public:
1806  LSRInstance(Loop *L, Pass *P);
1807
1808  bool getChanged() const { return Changed; }
1809
1810  void print_factors_and_types(raw_ostream &OS) const;
1811  void print_fixups(raw_ostream &OS) const;
1812  void print_uses(raw_ostream &OS) const;
1813  void print(raw_ostream &OS) const;
1814  void dump() const;
1815};
1816
1817}
1818
1819/// OptimizeShadowIV - If IV is used in a int-to-float cast
1820/// inside the loop then try to eliminate the cast operation.
1821void LSRInstance::OptimizeShadowIV() {
1822  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1823  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1824    return;
1825
1826  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1827       UI != E; /* empty */) {
1828    IVUsers::const_iterator CandidateUI = UI;
1829    ++UI;
1830    Instruction *ShadowUse = CandidateUI->getUser();
1831    Type *DestTy = nullptr;
1832    bool IsSigned = false;
1833
1834    /* If shadow use is a int->float cast then insert a second IV
1835       to eliminate this cast.
1836
1837         for (unsigned i = 0; i < n; ++i)
1838           foo((double)i);
1839
1840       is transformed into
1841
1842         double d = 0.0;
1843         for (unsigned i = 0; i < n; ++i, ++d)
1844           foo(d);
1845    */
1846    if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1847      IsSigned = false;
1848      DestTy = UCast->getDestTy();
1849    }
1850    else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1851      IsSigned = true;
1852      DestTy = SCast->getDestTy();
1853    }
1854    if (!DestTy) continue;
1855
1856    // If target does not support DestTy natively then do not apply
1857    // this transformation.
1858    if (!TTI.isTypeLegal(DestTy)) continue;
1859
1860    PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1861    if (!PH) continue;
1862    if (PH->getNumIncomingValues() != 2) continue;
1863
1864    Type *SrcTy = PH->getType();
1865    int Mantissa = DestTy->getFPMantissaWidth();
1866    if (Mantissa == -1) continue;
1867    if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1868      continue;
1869
1870    unsigned Entry, Latch;
1871    if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1872      Entry = 0;
1873      Latch = 1;
1874    } else {
1875      Entry = 1;
1876      Latch = 0;
1877    }
1878
1879    ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1880    if (!Init) continue;
1881    Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1882                                        (double)Init->getSExtValue() :
1883                                        (double)Init->getZExtValue());
1884
1885    BinaryOperator *Incr =
1886      dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1887    if (!Incr) continue;
1888    if (Incr->getOpcode() != Instruction::Add
1889        && Incr->getOpcode() != Instruction::Sub)
1890      continue;
1891
1892    /* Initialize new IV, double d = 0.0 in above example. */
1893    ConstantInt *C = nullptr;
1894    if (Incr->getOperand(0) == PH)
1895      C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1896    else if (Incr->getOperand(1) == PH)
1897      C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1898    else
1899      continue;
1900
1901    if (!C) continue;
1902
1903    // Ignore negative constants, as the code below doesn't handle them
1904    // correctly. TODO: Remove this restriction.
1905    if (!C->getValue().isStrictlyPositive()) continue;
1906
1907    /* Add new PHINode. */
1908    PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1909
1910    /* create new increment. '++d' in above example. */
1911    Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1912    BinaryOperator *NewIncr =
1913      BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1914                               Instruction::FAdd : Instruction::FSub,
1915                             NewPH, CFP, "IV.S.next.", Incr);
1916
1917    NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1918    NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1919
1920    /* Remove cast operation */
1921    ShadowUse->replaceAllUsesWith(NewPH);
1922    ShadowUse->eraseFromParent();
1923    Changed = true;
1924    break;
1925  }
1926}
1927
1928/// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1929/// set the IV user and stride information and return true, otherwise return
1930/// false.
1931bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1932  for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1933    if (UI->getUser() == Cond) {
1934      // NOTE: we could handle setcc instructions with multiple uses here, but
1935      // InstCombine does it as well for simple uses, it's not clear that it
1936      // occurs enough in real life to handle.
1937      CondUse = UI;
1938      return true;
1939    }
1940  return false;
1941}
1942
1943/// OptimizeMax - Rewrite the loop's terminating condition if it uses
1944/// a max computation.
1945///
1946/// This is a narrow solution to a specific, but acute, problem. For loops
1947/// like this:
1948///
1949///   i = 0;
1950///   do {
1951///     p[i] = 0.0;
1952///   } while (++i < n);
1953///
1954/// the trip count isn't just 'n', because 'n' might not be positive. And
1955/// unfortunately this can come up even for loops where the user didn't use
1956/// a C do-while loop. For example, seemingly well-behaved top-test loops
1957/// will commonly be lowered like this:
1958//
1959///   if (n > 0) {
1960///     i = 0;
1961///     do {
1962///       p[i] = 0.0;
1963///     } while (++i < n);
1964///   }
1965///
1966/// and then it's possible for subsequent optimization to obscure the if
1967/// test in such a way that indvars can't find it.
1968///
1969/// When indvars can't find the if test in loops like this, it creates a
1970/// max expression, which allows it to give the loop a canonical
1971/// induction variable:
1972///
1973///   i = 0;
1974///   max = n < 1 ? 1 : n;
1975///   do {
1976///     p[i] = 0.0;
1977///   } while (++i != max);
1978///
1979/// Canonical induction variables are necessary because the loop passes
1980/// are designed around them. The most obvious example of this is the
1981/// LoopInfo analysis, which doesn't remember trip count values. It
1982/// expects to be able to rediscover the trip count each time it is
1983/// needed, and it does this using a simple analysis that only succeeds if
1984/// the loop has a canonical induction variable.
1985///
1986/// However, when it comes time to generate code, the maximum operation
1987/// can be quite costly, especially if it's inside of an outer loop.
1988///
1989/// This function solves this problem by detecting this type of loop and
1990/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1991/// the instructions for the maximum computation.
1992///
1993ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1994  // Check that the loop matches the pattern we're looking for.
1995  if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1996      Cond->getPredicate() != CmpInst::ICMP_NE)
1997    return Cond;
1998
1999  SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2000  if (!Sel || !Sel->hasOneUse()) return Cond;
2001
2002  const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2003  if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2004    return Cond;
2005  const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2006
2007  // Add one to the backedge-taken count to get the trip count.
2008  const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2009  if (IterationCount != SE.getSCEV(Sel)) return Cond;
2010
2011  // Check for a max calculation that matches the pattern. There's no check
2012  // for ICMP_ULE here because the comparison would be with zero, which
2013  // isn't interesting.
2014  CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2015  const SCEVNAryExpr *Max = nullptr;
2016  if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2017    Pred = ICmpInst::ICMP_SLE;
2018    Max = S;
2019  } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2020    Pred = ICmpInst::ICMP_SLT;
2021    Max = S;
2022  } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2023    Pred = ICmpInst::ICMP_ULT;
2024    Max = U;
2025  } else {
2026    // No match; bail.
2027    return Cond;
2028  }
2029
2030  // To handle a max with more than two operands, this optimization would
2031  // require additional checking and setup.
2032  if (Max->getNumOperands() != 2)
2033    return Cond;
2034
2035  const SCEV *MaxLHS = Max->getOperand(0);
2036  const SCEV *MaxRHS = Max->getOperand(1);
2037
2038  // ScalarEvolution canonicalizes constants to the left. For < and >, look
2039  // for a comparison with 1. For <= and >=, a comparison with zero.
2040  if (!MaxLHS ||
2041      (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2042    return Cond;
2043
2044  // Check the relevant induction variable for conformance to
2045  // the pattern.
2046  const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2047  const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2048  if (!AR || !AR->isAffine() ||
2049      AR->getStart() != One ||
2050      AR->getStepRecurrence(SE) != One)
2051    return Cond;
2052
2053  assert(AR->getLoop() == L &&
2054         "Loop condition operand is an addrec in a different loop!");
2055
2056  // Check the right operand of the select, and remember it, as it will
2057  // be used in the new comparison instruction.
2058  Value *NewRHS = nullptr;
2059  if (ICmpInst::isTrueWhenEqual(Pred)) {
2060    // Look for n+1, and grab n.
2061    if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2062      if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2063         if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2064           NewRHS = BO->getOperand(0);
2065    if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2066      if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2067        if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2068          NewRHS = BO->getOperand(0);
2069    if (!NewRHS)
2070      return Cond;
2071  } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2072    NewRHS = Sel->getOperand(1);
2073  else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2074    NewRHS = Sel->getOperand(2);
2075  else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2076    NewRHS = SU->getValue();
2077  else
2078    // Max doesn't match expected pattern.
2079    return Cond;
2080
2081  // Determine the new comparison opcode. It may be signed or unsigned,
2082  // and the original comparison may be either equality or inequality.
2083  if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2084    Pred = CmpInst::getInversePredicate(Pred);
2085
2086  // Ok, everything looks ok to change the condition into an SLT or SGE and
2087  // delete the max calculation.
2088  ICmpInst *NewCond =
2089    new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2090
2091  // Delete the max calculation instructions.
2092  Cond->replaceAllUsesWith(NewCond);
2093  CondUse->setUser(NewCond);
2094  Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2095  Cond->eraseFromParent();
2096  Sel->eraseFromParent();
2097  if (Cmp->use_empty())
2098    Cmp->eraseFromParent();
2099  return NewCond;
2100}
2101
2102/// OptimizeLoopTermCond - Change loop terminating condition to use the
2103/// postinc iv when possible.
2104void
2105LSRInstance::OptimizeLoopTermCond() {
2106  SmallPtrSet<Instruction *, 4> PostIncs;
2107
2108  BasicBlock *LatchBlock = L->getLoopLatch();
2109  SmallVector<BasicBlock*, 8> ExitingBlocks;
2110  L->getExitingBlocks(ExitingBlocks);
2111
2112  for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
2113    BasicBlock *ExitingBlock = ExitingBlocks[i];
2114
2115    // Get the terminating condition for the loop if possible.  If we
2116    // can, we want to change it to use a post-incremented version of its
2117    // induction variable, to allow coalescing the live ranges for the IV into
2118    // one register value.
2119
2120    BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2121    if (!TermBr)
2122      continue;
2123    // FIXME: Overly conservative, termination condition could be an 'or' etc..
2124    if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2125      continue;
2126
2127    // Search IVUsesByStride to find Cond's IVUse if there is one.
2128    IVStrideUse *CondUse = nullptr;
2129    ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2130    if (!FindIVUserForCond(Cond, CondUse))
2131      continue;
2132
2133    // If the trip count is computed in terms of a max (due to ScalarEvolution
2134    // being unable to find a sufficient guard, for example), change the loop
2135    // comparison to use SLT or ULT instead of NE.
2136    // One consequence of doing this now is that it disrupts the count-down
2137    // optimization. That's not always a bad thing though, because in such
2138    // cases it may still be worthwhile to avoid a max.
2139    Cond = OptimizeMax(Cond, CondUse);
2140
2141    // If this exiting block dominates the latch block, it may also use
2142    // the post-inc value if it won't be shared with other uses.
2143    // Check for dominance.
2144    if (!DT.dominates(ExitingBlock, LatchBlock))
2145      continue;
2146
2147    // Conservatively avoid trying to use the post-inc value in non-latch
2148    // exits if there may be pre-inc users in intervening blocks.
2149    if (LatchBlock != ExitingBlock)
2150      for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2151        // Test if the use is reachable from the exiting block. This dominator
2152        // query is a conservative approximation of reachability.
2153        if (&*UI != CondUse &&
2154            !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2155          // Conservatively assume there may be reuse if the quotient of their
2156          // strides could be a legal scale.
2157          const SCEV *A = IU.getStride(*CondUse, L);
2158          const SCEV *B = IU.getStride(*UI, L);
2159          if (!A || !B) continue;
2160          if (SE.getTypeSizeInBits(A->getType()) !=
2161              SE.getTypeSizeInBits(B->getType())) {
2162            if (SE.getTypeSizeInBits(A->getType()) >
2163                SE.getTypeSizeInBits(B->getType()))
2164              B = SE.getSignExtendExpr(B, A->getType());
2165            else
2166              A = SE.getSignExtendExpr(A, B->getType());
2167          }
2168          if (const SCEVConstant *D =
2169                dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2170            const ConstantInt *C = D->getValue();
2171            // Stride of one or negative one can have reuse with non-addresses.
2172            if (C->isOne() || C->isAllOnesValue())
2173              goto decline_post_inc;
2174            // Avoid weird situations.
2175            if (C->getValue().getMinSignedBits() >= 64 ||
2176                C->getValue().isMinSignedValue())
2177              goto decline_post_inc;
2178            // Check for possible scaled-address reuse.
2179            Type *AccessTy = getAccessType(UI->getUser());
2180            int64_t Scale = C->getSExtValue();
2181            if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2182                                          /*BaseOffset=*/ 0,
2183                                          /*HasBaseReg=*/ false, Scale))
2184              goto decline_post_inc;
2185            Scale = -Scale;
2186            if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2187                                          /*BaseOffset=*/ 0,
2188                                          /*HasBaseReg=*/ false, Scale))
2189              goto decline_post_inc;
2190          }
2191        }
2192
2193    DEBUG(dbgs() << "  Change loop exiting icmp to use postinc iv: "
2194                 << *Cond << '\n');
2195
2196    // It's possible for the setcc instruction to be anywhere in the loop, and
2197    // possible for it to have multiple users.  If it is not immediately before
2198    // the exiting block branch, move it.
2199    if (&*++BasicBlock::iterator(Cond) != TermBr) {
2200      if (Cond->hasOneUse()) {
2201        Cond->moveBefore(TermBr);
2202      } else {
2203        // Clone the terminating condition and insert into the loopend.
2204        ICmpInst *OldCond = Cond;
2205        Cond = cast<ICmpInst>(Cond->clone());
2206        Cond->setName(L->getHeader()->getName() + ".termcond");
2207        ExitingBlock->getInstList().insert(TermBr, Cond);
2208
2209        // Clone the IVUse, as the old use still exists!
2210        CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2211        TermBr->replaceUsesOfWith(OldCond, Cond);
2212      }
2213    }
2214
2215    // If we get to here, we know that we can transform the setcc instruction to
2216    // use the post-incremented version of the IV, allowing us to coalesce the
2217    // live ranges for the IV correctly.
2218    CondUse->transformToPostInc(L);
2219    Changed = true;
2220
2221    PostIncs.insert(Cond);
2222  decline_post_inc:;
2223  }
2224
2225  // Determine an insertion point for the loop induction variable increment. It
2226  // must dominate all the post-inc comparisons we just set up, and it must
2227  // dominate the loop latch edge.
2228  IVIncInsertPos = L->getLoopLatch()->getTerminator();
2229  for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
2230       E = PostIncs.end(); I != E; ++I) {
2231    BasicBlock *BB =
2232      DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2233                                    (*I)->getParent());
2234    if (BB == (*I)->getParent())
2235      IVIncInsertPos = *I;
2236    else if (BB != IVIncInsertPos->getParent())
2237      IVIncInsertPos = BB->getTerminator();
2238  }
2239}
2240
2241/// reconcileNewOffset - Determine if the given use can accommodate a fixup
2242/// at the given offset and other details. If so, update the use and
2243/// return true.
2244bool
2245LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2246                                LSRUse::KindType Kind, Type *AccessTy) {
2247  int64_t NewMinOffset = LU.MinOffset;
2248  int64_t NewMaxOffset = LU.MaxOffset;
2249  Type *NewAccessTy = AccessTy;
2250
2251  // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2252  // something conservative, however this can pessimize in the case that one of
2253  // the uses will have all its uses outside the loop, for example.
2254  if (LU.Kind != Kind)
2255    return false;
2256
2257  // Check for a mismatched access type, and fall back conservatively as needed.
2258  // TODO: Be less conservative when the type is similar and can use the same
2259  // addressing modes.
2260  if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2261    NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2262
2263  // Conservatively assume HasBaseReg is true for now.
2264  if (NewOffset < LU.MinOffset) {
2265    if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2266                          LU.MaxOffset - NewOffset, HasBaseReg))
2267      return false;
2268    NewMinOffset = NewOffset;
2269  } else if (NewOffset > LU.MaxOffset) {
2270    if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2271                          NewOffset - LU.MinOffset, HasBaseReg))
2272      return false;
2273    NewMaxOffset = NewOffset;
2274  }
2275
2276  // Update the use.
2277  LU.MinOffset = NewMinOffset;
2278  LU.MaxOffset = NewMaxOffset;
2279  LU.AccessTy = NewAccessTy;
2280  if (NewOffset != LU.Offsets.back())
2281    LU.Offsets.push_back(NewOffset);
2282  return true;
2283}
2284
2285/// getUse - Return an LSRUse index and an offset value for a fixup which
2286/// needs the given expression, with the given kind and optional access type.
2287/// Either reuse an existing use or create a new one, as needed.
2288std::pair<size_t, int64_t>
2289LSRInstance::getUse(const SCEV *&Expr,
2290                    LSRUse::KindType Kind, Type *AccessTy) {
2291  const SCEV *Copy = Expr;
2292  int64_t Offset = ExtractImmediate(Expr, SE);
2293
2294  // Basic uses can't accept any offset, for example.
2295  if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2296                        Offset, /*HasBaseReg=*/ true)) {
2297    Expr = Copy;
2298    Offset = 0;
2299  }
2300
2301  std::pair<UseMapTy::iterator, bool> P =
2302    UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2303  if (!P.second) {
2304    // A use already existed with this base.
2305    size_t LUIdx = P.first->second;
2306    LSRUse &LU = Uses[LUIdx];
2307    if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2308      // Reuse this use.
2309      return std::make_pair(LUIdx, Offset);
2310  }
2311
2312  // Create a new use.
2313  size_t LUIdx = Uses.size();
2314  P.first->second = LUIdx;
2315  Uses.push_back(LSRUse(Kind, AccessTy));
2316  LSRUse &LU = Uses[LUIdx];
2317
2318  // We don't need to track redundant offsets, but we don't need to go out
2319  // of our way here to avoid them.
2320  if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2321    LU.Offsets.push_back(Offset);
2322
2323  LU.MinOffset = Offset;
2324  LU.MaxOffset = Offset;
2325  return std::make_pair(LUIdx, Offset);
2326}
2327
2328/// DeleteUse - Delete the given use from the Uses list.
2329void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2330  if (&LU != &Uses.back())
2331    std::swap(LU, Uses.back());
2332  Uses.pop_back();
2333
2334  // Update RegUses.
2335  RegUses.SwapAndDropUse(LUIdx, Uses.size());
2336}
2337
2338/// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2339/// a formula that has the same registers as the given formula.
2340LSRUse *
2341LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2342                                       const LSRUse &OrigLU) {
2343  // Search all uses for the formula. This could be more clever.
2344  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2345    LSRUse &LU = Uses[LUIdx];
2346    // Check whether this use is close enough to OrigLU, to see whether it's
2347    // worthwhile looking through its formulae.
2348    // Ignore ICmpZero uses because they may contain formulae generated by
2349    // GenerateICmpZeroScales, in which case adding fixup offsets may
2350    // be invalid.
2351    if (&LU != &OrigLU &&
2352        LU.Kind != LSRUse::ICmpZero &&
2353        LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2354        LU.WidestFixupType == OrigLU.WidestFixupType &&
2355        LU.HasFormulaWithSameRegs(OrigF)) {
2356      // Scan through this use's formulae.
2357      for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2358           E = LU.Formulae.end(); I != E; ++I) {
2359        const Formula &F = *I;
2360        // Check to see if this formula has the same registers and symbols
2361        // as OrigF.
2362        if (F.BaseRegs == OrigF.BaseRegs &&
2363            F.ScaledReg == OrigF.ScaledReg &&
2364            F.BaseGV == OrigF.BaseGV &&
2365            F.Scale == OrigF.Scale &&
2366            F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2367          if (F.BaseOffset == 0)
2368            return &LU;
2369          // This is the formula where all the registers and symbols matched;
2370          // there aren't going to be any others. Since we declined it, we
2371          // can skip the rest of the formulae and proceed to the next LSRUse.
2372          break;
2373        }
2374      }
2375    }
2376  }
2377
2378  // Nothing looked good.
2379  return nullptr;
2380}
2381
2382void LSRInstance::CollectInterestingTypesAndFactors() {
2383  SmallSetVector<const SCEV *, 4> Strides;
2384
2385  // Collect interesting types and strides.
2386  SmallVector<const SCEV *, 4> Worklist;
2387  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2388    const SCEV *Expr = IU.getExpr(*UI);
2389
2390    // Collect interesting types.
2391    Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2392
2393    // Add strides for mentioned loops.
2394    Worklist.push_back(Expr);
2395    do {
2396      const SCEV *S = Worklist.pop_back_val();
2397      if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2398        if (AR->getLoop() == L)
2399          Strides.insert(AR->getStepRecurrence(SE));
2400        Worklist.push_back(AR->getStart());
2401      } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2402        Worklist.append(Add->op_begin(), Add->op_end());
2403      }
2404    } while (!Worklist.empty());
2405  }
2406
2407  // Compute interesting factors from the set of interesting strides.
2408  for (SmallSetVector<const SCEV *, 4>::const_iterator
2409       I = Strides.begin(), E = Strides.end(); I != E; ++I)
2410    for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2411         std::next(I); NewStrideIter != E; ++NewStrideIter) {
2412      const SCEV *OldStride = *I;
2413      const SCEV *NewStride = *NewStrideIter;
2414
2415      if (SE.getTypeSizeInBits(OldStride->getType()) !=
2416          SE.getTypeSizeInBits(NewStride->getType())) {
2417        if (SE.getTypeSizeInBits(OldStride->getType()) >
2418            SE.getTypeSizeInBits(NewStride->getType()))
2419          NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2420        else
2421          OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2422      }
2423      if (const SCEVConstant *Factor =
2424            dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2425                                                        SE, true))) {
2426        if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2427          Factors.insert(Factor->getValue()->getValue().getSExtValue());
2428      } else if (const SCEVConstant *Factor =
2429                   dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2430                                                               NewStride,
2431                                                               SE, true))) {
2432        if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2433          Factors.insert(Factor->getValue()->getValue().getSExtValue());
2434      }
2435    }
2436
2437  // If all uses use the same type, don't bother looking for truncation-based
2438  // reuse.
2439  if (Types.size() == 1)
2440    Types.clear();
2441
2442  DEBUG(print_factors_and_types(dbgs()));
2443}
2444
2445/// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2446/// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2447/// Instructions to IVStrideUses, we could partially skip this.
2448static User::op_iterator
2449findIVOperand(User::op_iterator OI, User::op_iterator OE,
2450              Loop *L, ScalarEvolution &SE) {
2451  for(; OI != OE; ++OI) {
2452    if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2453      if (!SE.isSCEVable(Oper->getType()))
2454        continue;
2455
2456      if (const SCEVAddRecExpr *AR =
2457          dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2458        if (AR->getLoop() == L)
2459          break;
2460      }
2461    }
2462  }
2463  return OI;
2464}
2465
2466/// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2467/// operands, so wrap it in a convenient helper.
2468static Value *getWideOperand(Value *Oper) {
2469  if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2470    return Trunc->getOperand(0);
2471  return Oper;
2472}
2473
2474/// isCompatibleIVType - Return true if we allow an IV chain to include both
2475/// types.
2476static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2477  Type *LType = LVal->getType();
2478  Type *RType = RVal->getType();
2479  return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2480}
2481
2482/// getExprBase - Return an approximation of this SCEV expression's "base", or
2483/// NULL for any constant. Returning the expression itself is
2484/// conservative. Returning a deeper subexpression is more precise and valid as
2485/// long as it isn't less complex than another subexpression. For expressions
2486/// involving multiple unscaled values, we need to return the pointer-type
2487/// SCEVUnknown. This avoids forming chains across objects, such as:
2488/// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2489///
2490/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2491/// SCEVUnknown, we simply return the rightmost SCEV operand.
2492static const SCEV *getExprBase(const SCEV *S) {
2493  switch (S->getSCEVType()) {
2494  default: // uncluding scUnknown.
2495    return S;
2496  case scConstant:
2497    return nullptr;
2498  case scTruncate:
2499    return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2500  case scZeroExtend:
2501    return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2502  case scSignExtend:
2503    return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2504  case scAddExpr: {
2505    // Skip over scaled operands (scMulExpr) to follow add operands as long as
2506    // there's nothing more complex.
2507    // FIXME: not sure if we want to recognize negation.
2508    const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2509    for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2510           E(Add->op_begin()); I != E; ++I) {
2511      const SCEV *SubExpr = *I;
2512      if (SubExpr->getSCEVType() == scAddExpr)
2513        return getExprBase(SubExpr);
2514
2515      if (SubExpr->getSCEVType() != scMulExpr)
2516        return SubExpr;
2517    }
2518    return S; // all operands are scaled, be conservative.
2519  }
2520  case scAddRecExpr:
2521    return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2522  }
2523}
2524
2525/// Return true if the chain increment is profitable to expand into a loop
2526/// invariant value, which may require its own register. A profitable chain
2527/// increment will be an offset relative to the same base. We allow such offsets
2528/// to potentially be used as chain increment as long as it's not obviously
2529/// expensive to expand using real instructions.
2530bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2531                                    const SCEV *IncExpr,
2532                                    ScalarEvolution &SE) {
2533  // Aggressively form chains when -stress-ivchain.
2534  if (StressIVChain)
2535    return true;
2536
2537  // Do not replace a constant offset from IV head with a nonconstant IV
2538  // increment.
2539  if (!isa<SCEVConstant>(IncExpr)) {
2540    const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2541    if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2542      return 0;
2543  }
2544
2545  SmallPtrSet<const SCEV*, 8> Processed;
2546  return !isHighCostExpansion(IncExpr, Processed, SE);
2547}
2548
2549/// Return true if the number of registers needed for the chain is estimated to
2550/// be less than the number required for the individual IV users. First prohibit
2551/// any IV users that keep the IV live across increments (the Users set should
2552/// be empty). Next count the number and type of increments in the chain.
2553///
2554/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2555/// effectively use postinc addressing modes. Only consider it profitable it the
2556/// increments can be computed in fewer registers when chained.
2557///
2558/// TODO: Consider IVInc free if it's already used in another chains.
2559static bool
2560isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users,
2561                  ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2562  if (StressIVChain)
2563    return true;
2564
2565  if (!Chain.hasIncs())
2566    return false;
2567
2568  if (!Users.empty()) {
2569    DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2570          for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(),
2571                 E = Users.end(); I != E; ++I) {
2572            dbgs() << "  " << **I << "\n";
2573          });
2574    return false;
2575  }
2576  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2577
2578  // The chain itself may require a register, so intialize cost to 1.
2579  int cost = 1;
2580
2581  // A complete chain likely eliminates the need for keeping the original IV in
2582  // a register. LSR does not currently know how to form a complete chain unless
2583  // the header phi already exists.
2584  if (isa<PHINode>(Chain.tailUserInst())
2585      && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2586    --cost;
2587  }
2588  const SCEV *LastIncExpr = nullptr;
2589  unsigned NumConstIncrements = 0;
2590  unsigned NumVarIncrements = 0;
2591  unsigned NumReusedIncrements = 0;
2592  for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2593       I != E; ++I) {
2594
2595    if (I->IncExpr->isZero())
2596      continue;
2597
2598    // Incrementing by zero or some constant is neutral. We assume constants can
2599    // be folded into an addressing mode or an add's immediate operand.
2600    if (isa<SCEVConstant>(I->IncExpr)) {
2601      ++NumConstIncrements;
2602      continue;
2603    }
2604
2605    if (I->IncExpr == LastIncExpr)
2606      ++NumReusedIncrements;
2607    else
2608      ++NumVarIncrements;
2609
2610    LastIncExpr = I->IncExpr;
2611  }
2612  // An IV chain with a single increment is handled by LSR's postinc
2613  // uses. However, a chain with multiple increments requires keeping the IV's
2614  // value live longer than it needs to be if chained.
2615  if (NumConstIncrements > 1)
2616    --cost;
2617
2618  // Materializing increment expressions in the preheader that didn't exist in
2619  // the original code may cost a register. For example, sign-extended array
2620  // indices can produce ridiculous increments like this:
2621  // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2622  cost += NumVarIncrements;
2623
2624  // Reusing variable increments likely saves a register to hold the multiple of
2625  // the stride.
2626  cost -= NumReusedIncrements;
2627
2628  DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2629               << "\n");
2630
2631  return cost < 0;
2632}
2633
2634/// ChainInstruction - Add this IV user to an existing chain or make it the head
2635/// of a new chain.
2636void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2637                                   SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2638  // When IVs are used as types of varying widths, they are generally converted
2639  // to a wider type with some uses remaining narrow under a (free) trunc.
2640  Value *const NextIV = getWideOperand(IVOper);
2641  const SCEV *const OperExpr = SE.getSCEV(NextIV);
2642  const SCEV *const OperExprBase = getExprBase(OperExpr);
2643
2644  // Visit all existing chains. Check if its IVOper can be computed as a
2645  // profitable loop invariant increment from the last link in the Chain.
2646  unsigned ChainIdx = 0, NChains = IVChainVec.size();
2647  const SCEV *LastIncExpr = nullptr;
2648  for (; ChainIdx < NChains; ++ChainIdx) {
2649    IVChain &Chain = IVChainVec[ChainIdx];
2650
2651    // Prune the solution space aggressively by checking that both IV operands
2652    // are expressions that operate on the same unscaled SCEVUnknown. This
2653    // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2654    // first avoids creating extra SCEV expressions.
2655    if (!StressIVChain && Chain.ExprBase != OperExprBase)
2656      continue;
2657
2658    Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2659    if (!isCompatibleIVType(PrevIV, NextIV))
2660      continue;
2661
2662    // A phi node terminates a chain.
2663    if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2664      continue;
2665
2666    // The increment must be loop-invariant so it can be kept in a register.
2667    const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2668    const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2669    if (!SE.isLoopInvariant(IncExpr, L))
2670      continue;
2671
2672    if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2673      LastIncExpr = IncExpr;
2674      break;
2675    }
2676  }
2677  // If we haven't found a chain, create a new one, unless we hit the max. Don't
2678  // bother for phi nodes, because they must be last in the chain.
2679  if (ChainIdx == NChains) {
2680    if (isa<PHINode>(UserInst))
2681      return;
2682    if (NChains >= MaxChains && !StressIVChain) {
2683      DEBUG(dbgs() << "IV Chain Limit\n");
2684      return;
2685    }
2686    LastIncExpr = OperExpr;
2687    // IVUsers may have skipped over sign/zero extensions. We don't currently
2688    // attempt to form chains involving extensions unless they can be hoisted
2689    // into this loop's AddRec.
2690    if (!isa<SCEVAddRecExpr>(LastIncExpr))
2691      return;
2692    ++NChains;
2693    IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2694                                 OperExprBase));
2695    ChainUsersVec.resize(NChains);
2696    DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2697                 << ") IV=" << *LastIncExpr << "\n");
2698  } else {
2699    DEBUG(dbgs() << "IV Chain#" << ChainIdx << "  Inc: (" << *UserInst
2700                 << ") IV+" << *LastIncExpr << "\n");
2701    // Add this IV user to the end of the chain.
2702    IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2703  }
2704  IVChain &Chain = IVChainVec[ChainIdx];
2705
2706  SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2707  // This chain's NearUsers become FarUsers.
2708  if (!LastIncExpr->isZero()) {
2709    ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2710                                            NearUsers.end());
2711    NearUsers.clear();
2712  }
2713
2714  // All other uses of IVOperand become near uses of the chain.
2715  // We currently ignore intermediate values within SCEV expressions, assuming
2716  // they will eventually be used be the current chain, or can be computed
2717  // from one of the chain increments. To be more precise we could
2718  // transitively follow its user and only add leaf IV users to the set.
2719  for (User *U : IVOper->users()) {
2720    Instruction *OtherUse = dyn_cast<Instruction>(U);
2721    if (!OtherUse)
2722      continue;
2723    // Uses in the chain will no longer be uses if the chain is formed.
2724    // Include the head of the chain in this iteration (not Chain.begin()).
2725    IVChain::const_iterator IncIter = Chain.Incs.begin();
2726    IVChain::const_iterator IncEnd = Chain.Incs.end();
2727    for( ; IncIter != IncEnd; ++IncIter) {
2728      if (IncIter->UserInst == OtherUse)
2729        break;
2730    }
2731    if (IncIter != IncEnd)
2732      continue;
2733
2734    if (SE.isSCEVable(OtherUse->getType())
2735        && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2736        && IU.isIVUserOrOperand(OtherUse)) {
2737      continue;
2738    }
2739    NearUsers.insert(OtherUse);
2740  }
2741
2742  // Since this user is part of the chain, it's no longer considered a use
2743  // of the chain.
2744  ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2745}
2746
2747/// CollectChains - Populate the vector of Chains.
2748///
2749/// This decreases ILP at the architecture level. Targets with ample registers,
2750/// multiple memory ports, and no register renaming probably don't want
2751/// this. However, such targets should probably disable LSR altogether.
2752///
2753/// The job of LSR is to make a reasonable choice of induction variables across
2754/// the loop. Subsequent passes can easily "unchain" computation exposing more
2755/// ILP *within the loop* if the target wants it.
2756///
2757/// Finding the best IV chain is potentially a scheduling problem. Since LSR
2758/// will not reorder memory operations, it will recognize this as a chain, but
2759/// will generate redundant IV increments. Ideally this would be corrected later
2760/// by a smart scheduler:
2761///        = A[i]
2762///        = A[i+x]
2763/// A[i]   =
2764/// A[i+x] =
2765///
2766/// TODO: Walk the entire domtree within this loop, not just the path to the
2767/// loop latch. This will discover chains on side paths, but requires
2768/// maintaining multiple copies of the Chains state.
2769void LSRInstance::CollectChains() {
2770  DEBUG(dbgs() << "Collecting IV Chains.\n");
2771  SmallVector<ChainUsers, 8> ChainUsersVec;
2772
2773  SmallVector<BasicBlock *,8> LatchPath;
2774  BasicBlock *LoopHeader = L->getHeader();
2775  for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2776       Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2777    LatchPath.push_back(Rung->getBlock());
2778  }
2779  LatchPath.push_back(LoopHeader);
2780
2781  // Walk the instruction stream from the loop header to the loop latch.
2782  for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2783         BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2784       BBIter != BBEnd; ++BBIter) {
2785    for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2786         I != E; ++I) {
2787      // Skip instructions that weren't seen by IVUsers analysis.
2788      if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2789        continue;
2790
2791      // Ignore users that are part of a SCEV expression. This way we only
2792      // consider leaf IV Users. This effectively rediscovers a portion of
2793      // IVUsers analysis but in program order this time.
2794      if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2795        continue;
2796
2797      // Remove this instruction from any NearUsers set it may be in.
2798      for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2799           ChainIdx < NChains; ++ChainIdx) {
2800        ChainUsersVec[ChainIdx].NearUsers.erase(I);
2801      }
2802      // Search for operands that can be chained.
2803      SmallPtrSet<Instruction*, 4> UniqueOperands;
2804      User::op_iterator IVOpEnd = I->op_end();
2805      User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2806      while (IVOpIter != IVOpEnd) {
2807        Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2808        if (UniqueOperands.insert(IVOpInst))
2809          ChainInstruction(I, IVOpInst, ChainUsersVec);
2810        IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2811      }
2812    } // Continue walking down the instructions.
2813  } // Continue walking down the domtree.
2814  // Visit phi backedges to determine if the chain can generate the IV postinc.
2815  for (BasicBlock::iterator I = L->getHeader()->begin();
2816       PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2817    if (!SE.isSCEVable(PN->getType()))
2818      continue;
2819
2820    Instruction *IncV =
2821      dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2822    if (IncV)
2823      ChainInstruction(PN, IncV, ChainUsersVec);
2824  }
2825  // Remove any unprofitable chains.
2826  unsigned ChainIdx = 0;
2827  for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2828       UsersIdx < NChains; ++UsersIdx) {
2829    if (!isProfitableChain(IVChainVec[UsersIdx],
2830                           ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
2831      continue;
2832    // Preserve the chain at UsesIdx.
2833    if (ChainIdx != UsersIdx)
2834      IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2835    FinalizeChain(IVChainVec[ChainIdx]);
2836    ++ChainIdx;
2837  }
2838  IVChainVec.resize(ChainIdx);
2839}
2840
2841void LSRInstance::FinalizeChain(IVChain &Chain) {
2842  assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2843  DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
2844
2845  for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2846       I != E; ++I) {
2847    DEBUG(dbgs() << "        Inc: " << *I->UserInst << "\n");
2848    User::op_iterator UseI =
2849      std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
2850    assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
2851    IVIncSet.insert(UseI);
2852  }
2853}
2854
2855/// Return true if the IVInc can be folded into an addressing mode.
2856static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2857                             Value *Operand, const TargetTransformInfo &TTI) {
2858  const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2859  if (!IncConst || !isAddressUse(UserInst, Operand))
2860    return false;
2861
2862  if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2863    return false;
2864
2865  int64_t IncOffset = IncConst->getValue()->getSExtValue();
2866  if (!isAlwaysFoldable(TTI, LSRUse::Address,
2867                        getAccessType(UserInst), /*BaseGV=*/ nullptr,
2868                        IncOffset, /*HaseBaseReg=*/ false))
2869    return false;
2870
2871  return true;
2872}
2873
2874/// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2875/// materialize the IV user's operand from the previous IV user's operand.
2876void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2877                                  SmallVectorImpl<WeakVH> &DeadInsts) {
2878  // Find the new IVOperand for the head of the chain. It may have been replaced
2879  // by LSR.
2880  const IVInc &Head = Chain.Incs[0];
2881  User::op_iterator IVOpEnd = Head.UserInst->op_end();
2882  // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
2883  User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2884                                             IVOpEnd, L, SE);
2885  Value *IVSrc = nullptr;
2886  while (IVOpIter != IVOpEnd) {
2887    IVSrc = getWideOperand(*IVOpIter);
2888
2889    // If this operand computes the expression that the chain needs, we may use
2890    // it. (Check this after setting IVSrc which is used below.)
2891    //
2892    // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2893    // narrow for the chain, so we can no longer use it. We do allow using a
2894    // wider phi, assuming the LSR checked for free truncation. In that case we
2895    // should already have a truncate on this operand such that
2896    // getSCEV(IVSrc) == IncExpr.
2897    if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2898        || SE.getSCEV(IVSrc) == Head.IncExpr) {
2899      break;
2900    }
2901    IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2902  }
2903  if (IVOpIter == IVOpEnd) {
2904    // Gracefully give up on this chain.
2905    DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2906    return;
2907  }
2908
2909  DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2910  Type *IVTy = IVSrc->getType();
2911  Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2912  const SCEV *LeftOverExpr = nullptr;
2913  for (IVChain::const_iterator IncI = Chain.begin(),
2914         IncE = Chain.end(); IncI != IncE; ++IncI) {
2915
2916    Instruction *InsertPt = IncI->UserInst;
2917    if (isa<PHINode>(InsertPt))
2918      InsertPt = L->getLoopLatch()->getTerminator();
2919
2920    // IVOper will replace the current IV User's operand. IVSrc is the IV
2921    // value currently held in a register.
2922    Value *IVOper = IVSrc;
2923    if (!IncI->IncExpr->isZero()) {
2924      // IncExpr was the result of subtraction of two narrow values, so must
2925      // be signed.
2926      const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
2927      LeftOverExpr = LeftOverExpr ?
2928        SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2929    }
2930    if (LeftOverExpr && !LeftOverExpr->isZero()) {
2931      // Expand the IV increment.
2932      Rewriter.clearPostInc();
2933      Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2934      const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2935                                             SE.getUnknown(IncV));
2936      IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2937
2938      // If an IV increment can't be folded, use it as the next IV value.
2939      if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
2940                            TTI)) {
2941        assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2942        IVSrc = IVOper;
2943        LeftOverExpr = nullptr;
2944      }
2945    }
2946    Type *OperTy = IncI->IVOperand->getType();
2947    if (IVTy != OperTy) {
2948      assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2949             "cannot extend a chained IV");
2950      IRBuilder<> Builder(InsertPt);
2951      IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2952    }
2953    IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
2954    DeadInsts.push_back(IncI->IVOperand);
2955  }
2956  // If LSR created a new, wider phi, we may also replace its postinc. We only
2957  // do this if we also found a wide value for the head of the chain.
2958  if (isa<PHINode>(Chain.tailUserInst())) {
2959    for (BasicBlock::iterator I = L->getHeader()->begin();
2960         PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2961      if (!isCompatibleIVType(Phi, IVSrc))
2962        continue;
2963      Instruction *PostIncV = dyn_cast<Instruction>(
2964        Phi->getIncomingValueForBlock(L->getLoopLatch()));
2965      if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2966        continue;
2967      Value *IVOper = IVSrc;
2968      Type *PostIncTy = PostIncV->getType();
2969      if (IVTy != PostIncTy) {
2970        assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2971        IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2972        Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2973        IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2974      }
2975      Phi->replaceUsesOfWith(PostIncV, IVOper);
2976      DeadInsts.push_back(PostIncV);
2977    }
2978  }
2979}
2980
2981void LSRInstance::CollectFixupsAndInitialFormulae() {
2982  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2983    Instruction *UserInst = UI->getUser();
2984    // Skip IV users that are part of profitable IV Chains.
2985    User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2986                                       UI->getOperandValToReplace());
2987    assert(UseI != UserInst->op_end() && "cannot find IV operand");
2988    if (IVIncSet.count(UseI))
2989      continue;
2990
2991    // Record the uses.
2992    LSRFixup &LF = getNewFixup();
2993    LF.UserInst = UserInst;
2994    LF.OperandValToReplace = UI->getOperandValToReplace();
2995    LF.PostIncLoops = UI->getPostIncLoops();
2996
2997    LSRUse::KindType Kind = LSRUse::Basic;
2998    Type *AccessTy = nullptr;
2999    if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
3000      Kind = LSRUse::Address;
3001      AccessTy = getAccessType(LF.UserInst);
3002    }
3003
3004    const SCEV *S = IU.getExpr(*UI);
3005
3006    // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3007    // (N - i == 0), and this allows (N - i) to be the expression that we work
3008    // with rather than just N or i, so we can consider the register
3009    // requirements for both N and i at the same time. Limiting this code to
3010    // equality icmps is not a problem because all interesting loops use
3011    // equality icmps, thanks to IndVarSimplify.
3012    if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
3013      if (CI->isEquality()) {
3014        // Swap the operands if needed to put the OperandValToReplace on the
3015        // left, for consistency.
3016        Value *NV = CI->getOperand(1);
3017        if (NV == LF.OperandValToReplace) {
3018          CI->setOperand(1, CI->getOperand(0));
3019          CI->setOperand(0, NV);
3020          NV = CI->getOperand(1);
3021          Changed = true;
3022        }
3023
3024        // x == y  -->  x - y == 0
3025        const SCEV *N = SE.getSCEV(NV);
3026        if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3027          // S is normalized, so normalize N before folding it into S
3028          // to keep the result normalized.
3029          N = TransformForPostIncUse(Normalize, N, CI, nullptr,
3030                                     LF.PostIncLoops, SE, DT);
3031          Kind = LSRUse::ICmpZero;
3032          S = SE.getMinusSCEV(N, S);
3033        }
3034
3035        // -1 and the negations of all interesting strides (except the negation
3036        // of -1) are now also interesting.
3037        for (size_t i = 0, e = Factors.size(); i != e; ++i)
3038          if (Factors[i] != -1)
3039            Factors.insert(-(uint64_t)Factors[i]);
3040        Factors.insert(-1);
3041      }
3042
3043    // Set up the initial formula for this use.
3044    std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3045    LF.LUIdx = P.first;
3046    LF.Offset = P.second;
3047    LSRUse &LU = Uses[LF.LUIdx];
3048    LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3049    if (!LU.WidestFixupType ||
3050        SE.getTypeSizeInBits(LU.WidestFixupType) <
3051        SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3052      LU.WidestFixupType = LF.OperandValToReplace->getType();
3053
3054    // If this is the first use of this LSRUse, give it a formula.
3055    if (LU.Formulae.empty()) {
3056      InsertInitialFormula(S, LU, LF.LUIdx);
3057      CountRegisters(LU.Formulae.back(), LF.LUIdx);
3058    }
3059  }
3060
3061  DEBUG(print_fixups(dbgs()));
3062}
3063
3064/// InsertInitialFormula - Insert a formula for the given expression into
3065/// the given use, separating out loop-variant portions from loop-invariant
3066/// and loop-computable portions.
3067void
3068LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3069  // Mark uses whose expressions cannot be expanded.
3070  if (!isSafeToExpand(S, SE))
3071    LU.RigidFormula = true;
3072
3073  Formula F;
3074  F.InitialMatch(S, L, SE);
3075  bool Inserted = InsertFormula(LU, LUIdx, F);
3076  assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3077}
3078
3079/// InsertSupplementalFormula - Insert a simple single-register formula for
3080/// the given expression into the given use.
3081void
3082LSRInstance::InsertSupplementalFormula(const SCEV *S,
3083                                       LSRUse &LU, size_t LUIdx) {
3084  Formula F;
3085  F.BaseRegs.push_back(S);
3086  F.HasBaseReg = true;
3087  bool Inserted = InsertFormula(LU, LUIdx, F);
3088  assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3089}
3090
3091/// CountRegisters - Note which registers are used by the given formula,
3092/// updating RegUses.
3093void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3094  if (F.ScaledReg)
3095    RegUses.CountRegister(F.ScaledReg, LUIdx);
3096  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
3097       E = F.BaseRegs.end(); I != E; ++I)
3098    RegUses.CountRegister(*I, LUIdx);
3099}
3100
3101/// InsertFormula - If the given formula has not yet been inserted, add it to
3102/// the list, and return true. Return false otherwise.
3103bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3104  // Do not insert formula that we will not be able to expand.
3105  assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3106         "Formula is illegal");
3107  if (!LU.InsertFormula(F))
3108    return false;
3109
3110  CountRegisters(F, LUIdx);
3111  return true;
3112}
3113
3114/// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
3115/// loop-invariant values which we're tracking. These other uses will pin these
3116/// values in registers, making them less profitable for elimination.
3117/// TODO: This currently misses non-constant addrec step registers.
3118/// TODO: Should this give more weight to users inside the loop?
3119void
3120LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3121  SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3122  SmallPtrSet<const SCEV *, 8> Inserted;
3123
3124  while (!Worklist.empty()) {
3125    const SCEV *S = Worklist.pop_back_val();
3126
3127    if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3128      Worklist.append(N->op_begin(), N->op_end());
3129    else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3130      Worklist.push_back(C->getOperand());
3131    else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3132      Worklist.push_back(D->getLHS());
3133      Worklist.push_back(D->getRHS());
3134    } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3135      if (!Inserted.insert(US)) continue;
3136      const Value *V = US->getValue();
3137      if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3138        // Look for instructions defined outside the loop.
3139        if (L->contains(Inst)) continue;
3140      } else if (isa<UndefValue>(V))
3141        // Undef doesn't have a live range, so it doesn't matter.
3142        continue;
3143      for (const Use &U : V->uses()) {
3144        const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3145        // Ignore non-instructions.
3146        if (!UserInst)
3147          continue;
3148        // Ignore instructions in other functions (as can happen with
3149        // Constants).
3150        if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3151          continue;
3152        // Ignore instructions not dominated by the loop.
3153        const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3154          UserInst->getParent() :
3155          cast<PHINode>(UserInst)->getIncomingBlock(
3156            PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3157        if (!DT.dominates(L->getHeader(), UseBB))
3158          continue;
3159        // Ignore uses which are part of other SCEV expressions, to avoid
3160        // analyzing them multiple times.
3161        if (SE.isSCEVable(UserInst->getType())) {
3162          const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3163          // If the user is a no-op, look through to its uses.
3164          if (!isa<SCEVUnknown>(UserS))
3165            continue;
3166          if (UserS == US) {
3167            Worklist.push_back(
3168              SE.getUnknown(const_cast<Instruction *>(UserInst)));
3169            continue;
3170          }
3171        }
3172        // Ignore icmp instructions which are already being analyzed.
3173        if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3174          unsigned OtherIdx = !U.getOperandNo();
3175          Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3176          if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3177            continue;
3178        }
3179
3180        LSRFixup &LF = getNewFixup();
3181        LF.UserInst = const_cast<Instruction *>(UserInst);
3182        LF.OperandValToReplace = U;
3183        std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, nullptr);
3184        LF.LUIdx = P.first;
3185        LF.Offset = P.second;
3186        LSRUse &LU = Uses[LF.LUIdx];
3187        LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3188        if (!LU.WidestFixupType ||
3189            SE.getTypeSizeInBits(LU.WidestFixupType) <
3190            SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3191          LU.WidestFixupType = LF.OperandValToReplace->getType();
3192        InsertSupplementalFormula(US, LU, LF.LUIdx);
3193        CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3194        break;
3195      }
3196    }
3197  }
3198}
3199
3200/// CollectSubexprs - Split S into subexpressions which can be pulled out into
3201/// separate registers. If C is non-null, multiply each subexpression by C.
3202///
3203/// Return remainder expression after factoring the subexpressions captured by
3204/// Ops. If Ops is complete, return NULL.
3205static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3206                                   SmallVectorImpl<const SCEV *> &Ops,
3207                                   const Loop *L,
3208                                   ScalarEvolution &SE,
3209                                   unsigned Depth = 0) {
3210  // Arbitrarily cap recursion to protect compile time.
3211  if (Depth >= 3)
3212    return S;
3213
3214  if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3215    // Break out add operands.
3216    for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
3217         I != E; ++I) {
3218      const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1);
3219      if (Remainder)
3220        Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3221    }
3222    return nullptr;
3223  } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3224    // Split a non-zero base out of an addrec.
3225    if (AR->getStart()->isZero())
3226      return S;
3227
3228    const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3229                                            C, Ops, L, SE, Depth+1);
3230    // Split the non-zero AddRec unless it is part of a nested recurrence that
3231    // does not pertain to this loop.
3232    if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3233      Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3234      Remainder = nullptr;
3235    }
3236    if (Remainder != AR->getStart()) {
3237      if (!Remainder)
3238        Remainder = SE.getConstant(AR->getType(), 0);
3239      return SE.getAddRecExpr(Remainder,
3240                              AR->getStepRecurrence(SE),
3241                              AR->getLoop(),
3242                              //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3243                              SCEV::FlagAnyWrap);
3244    }
3245  } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3246    // Break (C * (a + b + c)) into C*a + C*b + C*c.
3247    if (Mul->getNumOperands() != 2)
3248      return S;
3249    if (const SCEVConstant *Op0 =
3250        dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3251      C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3252      const SCEV *Remainder =
3253        CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3254      if (Remainder)
3255        Ops.push_back(SE.getMulExpr(C, Remainder));
3256      return nullptr;
3257    }
3258  }
3259  return S;
3260}
3261
3262/// \brief Helper function for LSRInstance::GenerateReassociations.
3263void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3264                                             const Formula &Base,
3265                                             unsigned Depth, size_t Idx,
3266                                             bool IsScaledReg) {
3267  const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3268  SmallVector<const SCEV *, 8> AddOps;
3269  const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3270  if (Remainder)
3271    AddOps.push_back(Remainder);
3272
3273  if (AddOps.size() == 1)
3274    return;
3275
3276  for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3277                                                     JE = AddOps.end();
3278       J != JE; ++J) {
3279
3280    // Loop-variant "unknown" values are uninteresting; we won't be able to
3281    // do anything meaningful with them.
3282    if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3283      continue;
3284
3285    // Don't pull a constant into a register if the constant could be folded
3286    // into an immediate field.
3287    if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3288                         LU.AccessTy, *J, Base.getNumRegs() > 1))
3289      continue;
3290
3291    // Collect all operands except *J.
3292    SmallVector<const SCEV *, 8> InnerAddOps(
3293        ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3294    InnerAddOps.append(std::next(J),
3295                       ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3296
3297    // Don't leave just a constant behind in a register if the constant could
3298    // be folded into an immediate field.
3299    if (InnerAddOps.size() == 1 &&
3300        isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3301                         LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3302      continue;
3303
3304    const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3305    if (InnerSum->isZero())
3306      continue;
3307    Formula F = Base;
3308
3309    // Add the remaining pieces of the add back into the new formula.
3310    const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3311    if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3312        TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3313                                InnerSumSC->getValue()->getZExtValue())) {
3314      F.UnfoldedOffset =
3315          (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3316      if (IsScaledReg)
3317        F.ScaledReg = nullptr;
3318      else
3319        F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3320    } else if (IsScaledReg)
3321      F.ScaledReg = InnerSum;
3322    else
3323      F.BaseRegs[Idx] = InnerSum;
3324
3325    // Add J as its own register, or an unfolded immediate.
3326    const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3327    if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3328        TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3329                                SC->getValue()->getZExtValue()))
3330      F.UnfoldedOffset =
3331          (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3332    else
3333      F.BaseRegs.push_back(*J);
3334    // We may have changed the number of register in base regs, adjust the
3335    // formula accordingly.
3336    F.Canonicalize();
3337
3338    if (InsertFormula(LU, LUIdx, F))
3339      // If that formula hadn't been seen before, recurse to find more like
3340      // it.
3341      GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3342  }
3343}
3344
3345/// GenerateReassociations - Split out subexpressions from adds and the bases of
3346/// addrecs.
3347void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3348                                         Formula Base, unsigned Depth) {
3349  assert(Base.isCanonical() && "Input must be in the canonical form");
3350  // Arbitrarily cap recursion to protect compile time.
3351  if (Depth >= 3)
3352    return;
3353
3354  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3355    GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3356
3357  if (Base.Scale == 1)
3358    GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3359                               /* Idx */ -1, /* IsScaledReg */ true);
3360}
3361
3362/// GenerateCombinations - Generate a formula consisting of all of the
3363/// loop-dominating registers added into a single register.
3364void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3365                                       Formula Base) {
3366  // This method is only interesting on a plurality of registers.
3367  if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3368    return;
3369
3370  // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3371  // processing the formula.
3372  Base.Unscale();
3373  Formula F = Base;
3374  F.BaseRegs.clear();
3375  SmallVector<const SCEV *, 4> Ops;
3376  for (SmallVectorImpl<const SCEV *>::const_iterator
3377       I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
3378    const SCEV *BaseReg = *I;
3379    if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3380        !SE.hasComputableLoopEvolution(BaseReg, L))
3381      Ops.push_back(BaseReg);
3382    else
3383      F.BaseRegs.push_back(BaseReg);
3384  }
3385  if (Ops.size() > 1) {
3386    const SCEV *Sum = SE.getAddExpr(Ops);
3387    // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3388    // opportunity to fold something. For now, just ignore such cases
3389    // rather than proceed with zero in a register.
3390    if (!Sum->isZero()) {
3391      F.BaseRegs.push_back(Sum);
3392      F.Canonicalize();
3393      (void)InsertFormula(LU, LUIdx, F);
3394    }
3395  }
3396}
3397
3398/// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3399void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3400                                              const Formula &Base, size_t Idx,
3401                                              bool IsScaledReg) {
3402  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3403  GlobalValue *GV = ExtractSymbol(G, SE);
3404  if (G->isZero() || !GV)
3405    return;
3406  Formula F = Base;
3407  F.BaseGV = GV;
3408  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3409    return;
3410  if (IsScaledReg)
3411    F.ScaledReg = G;
3412  else
3413    F.BaseRegs[Idx] = G;
3414  (void)InsertFormula(LU, LUIdx, F);
3415}
3416
3417/// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3418void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3419                                          Formula Base) {
3420  // We can't add a symbolic offset if the address already contains one.
3421  if (Base.BaseGV) return;
3422
3423  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3424    GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3425  if (Base.Scale == 1)
3426    GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3427                                /* IsScaledReg */ true);
3428}
3429
3430/// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3431void LSRInstance::GenerateConstantOffsetsImpl(
3432    LSRUse &LU, unsigned LUIdx, const Formula &Base,
3433    const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3434  const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3435  for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
3436                                                E = Worklist.end();
3437       I != E; ++I) {
3438    Formula F = Base;
3439    F.BaseOffset = (uint64_t)Base.BaseOffset - *I;
3440    if (isLegalUse(TTI, LU.MinOffset - *I, LU.MaxOffset - *I, LU.Kind,
3441                   LU.AccessTy, F)) {
3442      // Add the offset to the base register.
3443      const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
3444      // If it cancelled out, drop the base register, otherwise update it.
3445      if (NewG->isZero()) {
3446        if (IsScaledReg) {
3447          F.Scale = 0;
3448          F.ScaledReg = nullptr;
3449        } else
3450          F.DeleteBaseReg(F.BaseRegs[Idx]);
3451        F.Canonicalize();
3452      } else if (IsScaledReg)
3453        F.ScaledReg = NewG;
3454      else
3455        F.BaseRegs[Idx] = NewG;
3456
3457      (void)InsertFormula(LU, LUIdx, F);
3458    }
3459  }
3460
3461  int64_t Imm = ExtractImmediate(G, SE);
3462  if (G->isZero() || Imm == 0)
3463    return;
3464  Formula F = Base;
3465  F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3466  if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3467    return;
3468  if (IsScaledReg)
3469    F.ScaledReg = G;
3470  else
3471    F.BaseRegs[Idx] = G;
3472  (void)InsertFormula(LU, LUIdx, F);
3473}
3474
3475/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3476void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3477                                          Formula Base) {
3478  // TODO: For now, just add the min and max offset, because it usually isn't
3479  // worthwhile looking at everything inbetween.
3480  SmallVector<int64_t, 2> Worklist;
3481  Worklist.push_back(LU.MinOffset);
3482  if (LU.MaxOffset != LU.MinOffset)
3483    Worklist.push_back(LU.MaxOffset);
3484
3485  for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3486    GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3487  if (Base.Scale == 1)
3488    GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3489                                /* IsScaledReg */ true);
3490}
3491
3492/// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3493/// the comparison. For example, x == y -> x*c == y*c.
3494void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3495                                         Formula Base) {
3496  if (LU.Kind != LSRUse::ICmpZero) return;
3497
3498  // Determine the integer type for the base formula.
3499  Type *IntTy = Base.getType();
3500  if (!IntTy) return;
3501  if (SE.getTypeSizeInBits(IntTy) > 64) return;
3502
3503  // Don't do this if there is more than one offset.
3504  if (LU.MinOffset != LU.MaxOffset) return;
3505
3506  assert(!Base.BaseGV && "ICmpZero use is not legal!");
3507
3508  // Check each interesting stride.
3509  for (SmallSetVector<int64_t, 8>::const_iterator
3510       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3511    int64_t Factor = *I;
3512
3513    // Check that the multiplication doesn't overflow.
3514    if (Base.BaseOffset == INT64_MIN && Factor == -1)
3515      continue;
3516    int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3517    if (NewBaseOffset / Factor != Base.BaseOffset)
3518      continue;
3519    // If the offset will be truncated at this use, check that it is in bounds.
3520    if (!IntTy->isPointerTy() &&
3521        !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3522      continue;
3523
3524    // Check that multiplying with the use offset doesn't overflow.
3525    int64_t Offset = LU.MinOffset;
3526    if (Offset == INT64_MIN && Factor == -1)
3527      continue;
3528    Offset = (uint64_t)Offset * Factor;
3529    if (Offset / Factor != LU.MinOffset)
3530      continue;
3531    // If the offset will be truncated at this use, check that it is in bounds.
3532    if (!IntTy->isPointerTy() &&
3533        !ConstantInt::isValueValidForType(IntTy, Offset))
3534      continue;
3535
3536    Formula F = Base;
3537    F.BaseOffset = NewBaseOffset;
3538
3539    // Check that this scale is legal.
3540    if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3541      continue;
3542
3543    // Compensate for the use having MinOffset built into it.
3544    F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3545
3546    const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3547
3548    // Check that multiplying with each base register doesn't overflow.
3549    for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3550      F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3551      if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3552        goto next;
3553    }
3554
3555    // Check that multiplying with the scaled register doesn't overflow.
3556    if (F.ScaledReg) {
3557      F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3558      if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3559        continue;
3560    }
3561
3562    // Check that multiplying with the unfolded offset doesn't overflow.
3563    if (F.UnfoldedOffset != 0) {
3564      if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3565        continue;
3566      F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3567      if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3568        continue;
3569      // If the offset will be truncated, check that it is in bounds.
3570      if (!IntTy->isPointerTy() &&
3571          !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3572        continue;
3573    }
3574
3575    // If we make it here and it's legal, add it.
3576    (void)InsertFormula(LU, LUIdx, F);
3577  next:;
3578  }
3579}
3580
3581/// GenerateScales - Generate stride factor reuse formulae by making use of
3582/// scaled-offset address modes, for example.
3583void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3584  // Determine the integer type for the base formula.
3585  Type *IntTy = Base.getType();
3586  if (!IntTy) return;
3587
3588  // If this Formula already has a scaled register, we can't add another one.
3589  // Try to unscale the formula to generate a better scale.
3590  if (Base.Scale != 0 && !Base.Unscale())
3591    return;
3592
3593  assert(Base.Scale == 0 && "Unscale did not did its job!");
3594
3595  // Check each interesting stride.
3596  for (SmallSetVector<int64_t, 8>::const_iterator
3597       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3598    int64_t Factor = *I;
3599
3600    Base.Scale = Factor;
3601    Base.HasBaseReg = Base.BaseRegs.size() > 1;
3602    // Check whether this scale is going to be legal.
3603    if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3604                    Base)) {
3605      // As a special-case, handle special out-of-loop Basic users specially.
3606      // TODO: Reconsider this special case.
3607      if (LU.Kind == LSRUse::Basic &&
3608          isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3609                     LU.AccessTy, Base) &&
3610          LU.AllFixupsOutsideLoop)
3611        LU.Kind = LSRUse::Special;
3612      else
3613        continue;
3614    }
3615    // For an ICmpZero, negating a solitary base register won't lead to
3616    // new solutions.
3617    if (LU.Kind == LSRUse::ICmpZero &&
3618        !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3619      continue;
3620    // For each addrec base reg, apply the scale, if possible.
3621    for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3622      if (const SCEVAddRecExpr *AR =
3623            dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3624        const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3625        if (FactorS->isZero())
3626          continue;
3627        // Divide out the factor, ignoring high bits, since we'll be
3628        // scaling the value back up in the end.
3629        if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3630          // TODO: This could be optimized to avoid all the copying.
3631          Formula F = Base;
3632          F.ScaledReg = Quotient;
3633          F.DeleteBaseReg(F.BaseRegs[i]);
3634          // The canonical representation of 1*reg is reg, which is already in
3635          // Base. In that case, do not try to insert the formula, it will be
3636          // rejected anyway.
3637          if (F.Scale == 1 && F.BaseRegs.empty())
3638            continue;
3639          (void)InsertFormula(LU, LUIdx, F);
3640        }
3641      }
3642  }
3643}
3644
3645/// GenerateTruncates - Generate reuse formulae from different IV types.
3646void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3647  // Don't bother truncating symbolic values.
3648  if (Base.BaseGV) return;
3649
3650  // Determine the integer type for the base formula.
3651  Type *DstTy = Base.getType();
3652  if (!DstTy) return;
3653  DstTy = SE.getEffectiveSCEVType(DstTy);
3654
3655  for (SmallSetVector<Type *, 4>::const_iterator
3656       I = Types.begin(), E = Types.end(); I != E; ++I) {
3657    Type *SrcTy = *I;
3658    if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3659      Formula F = Base;
3660
3661      if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
3662      for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
3663           JE = F.BaseRegs.end(); J != JE; ++J)
3664        *J = SE.getAnyExtendExpr(*J, SrcTy);
3665
3666      // TODO: This assumes we've done basic processing on all uses and
3667      // have an idea what the register usage is.
3668      if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3669        continue;
3670
3671      (void)InsertFormula(LU, LUIdx, F);
3672    }
3673  }
3674}
3675
3676namespace {
3677
3678/// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3679/// defer modifications so that the search phase doesn't have to worry about
3680/// the data structures moving underneath it.
3681struct WorkItem {
3682  size_t LUIdx;
3683  int64_t Imm;
3684  const SCEV *OrigReg;
3685
3686  WorkItem(size_t LI, int64_t I, const SCEV *R)
3687    : LUIdx(LI), Imm(I), OrigReg(R) {}
3688
3689  void print(raw_ostream &OS) const;
3690  void dump() const;
3691};
3692
3693}
3694
3695void WorkItem::print(raw_ostream &OS) const {
3696  OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3697     << " , add offset " << Imm;
3698}
3699
3700#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3701void WorkItem::dump() const {
3702  print(errs()); errs() << '\n';
3703}
3704#endif
3705
3706/// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3707/// distance apart and try to form reuse opportunities between them.
3708void LSRInstance::GenerateCrossUseConstantOffsets() {
3709  // Group the registers by their value without any added constant offset.
3710  typedef std::map<int64_t, const SCEV *> ImmMapTy;
3711  typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
3712  RegMapTy Map;
3713  DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3714  SmallVector<const SCEV *, 8> Sequence;
3715  for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3716       I != E; ++I) {
3717    const SCEV *Reg = *I;
3718    int64_t Imm = ExtractImmediate(Reg, SE);
3719    std::pair<RegMapTy::iterator, bool> Pair =
3720      Map.insert(std::make_pair(Reg, ImmMapTy()));
3721    if (Pair.second)
3722      Sequence.push_back(Reg);
3723    Pair.first->second.insert(std::make_pair(Imm, *I));
3724    UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
3725  }
3726
3727  // Now examine each set of registers with the same base value. Build up
3728  // a list of work to do and do the work in a separate step so that we're
3729  // not adding formulae and register counts while we're searching.
3730  SmallVector<WorkItem, 32> WorkItems;
3731  SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3732  for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
3733       E = Sequence.end(); I != E; ++I) {
3734    const SCEV *Reg = *I;
3735    const ImmMapTy &Imms = Map.find(Reg)->second;
3736
3737    // It's not worthwhile looking for reuse if there's only one offset.
3738    if (Imms.size() == 1)
3739      continue;
3740
3741    DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3742          for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3743               J != JE; ++J)
3744            dbgs() << ' ' << J->first;
3745          dbgs() << '\n');
3746
3747    // Examine each offset.
3748    for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3749         J != JE; ++J) {
3750      const SCEV *OrigReg = J->second;
3751
3752      int64_t JImm = J->first;
3753      const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3754
3755      if (!isa<SCEVConstant>(OrigReg) &&
3756          UsedByIndicesMap[Reg].count() == 1) {
3757        DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3758        continue;
3759      }
3760
3761      // Conservatively examine offsets between this orig reg a few selected
3762      // other orig regs.
3763      ImmMapTy::const_iterator OtherImms[] = {
3764        Imms.begin(), std::prev(Imms.end()),
3765        Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3766                         2)
3767      };
3768      for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3769        ImmMapTy::const_iterator M = OtherImms[i];
3770        if (M == J || M == JE) continue;
3771
3772        // Compute the difference between the two.
3773        int64_t Imm = (uint64_t)JImm - M->first;
3774        for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3775             LUIdx = UsedByIndices.find_next(LUIdx))
3776          // Make a memo of this use, offset, and register tuple.
3777          if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
3778            WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3779      }
3780    }
3781  }
3782
3783  Map.clear();
3784  Sequence.clear();
3785  UsedByIndicesMap.clear();
3786  UniqueItems.clear();
3787
3788  // Now iterate through the worklist and add new formulae.
3789  for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
3790       E = WorkItems.end(); I != E; ++I) {
3791    const WorkItem &WI = *I;
3792    size_t LUIdx = WI.LUIdx;
3793    LSRUse &LU = Uses[LUIdx];
3794    int64_t Imm = WI.Imm;
3795    const SCEV *OrigReg = WI.OrigReg;
3796
3797    Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3798    const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3799    unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3800
3801    // TODO: Use a more targeted data structure.
3802    for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3803      Formula F = LU.Formulae[L];
3804      // FIXME: The code for the scaled and unscaled registers looks
3805      // very similar but slightly different. Investigate if they
3806      // could be merged. That way, we would not have to unscale the
3807      // Formula.
3808      F.Unscale();
3809      // Use the immediate in the scaled register.
3810      if (F.ScaledReg == OrigReg) {
3811        int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
3812        // Don't create 50 + reg(-50).
3813        if (F.referencesReg(SE.getSCEV(
3814                   ConstantInt::get(IntTy, -(uint64_t)Offset))))
3815          continue;
3816        Formula NewF = F;
3817        NewF.BaseOffset = Offset;
3818        if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3819                        NewF))
3820          continue;
3821        NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3822
3823        // If the new scale is a constant in a register, and adding the constant
3824        // value to the immediate would produce a value closer to zero than the
3825        // immediate itself, then the formula isn't worthwhile.
3826        if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3827          if (C->getValue()->isNegative() !=
3828                (NewF.BaseOffset < 0) &&
3829              (C->getValue()->getValue().abs() * APInt(BitWidth, F.Scale))
3830                .ule(abs64(NewF.BaseOffset)))
3831            continue;
3832
3833        // OK, looks good.
3834        NewF.Canonicalize();
3835        (void)InsertFormula(LU, LUIdx, NewF);
3836      } else {
3837        // Use the immediate in a base register.
3838        for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3839          const SCEV *BaseReg = F.BaseRegs[N];
3840          if (BaseReg != OrigReg)
3841            continue;
3842          Formula NewF = F;
3843          NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
3844          if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
3845                          LU.Kind, LU.AccessTy, NewF)) {
3846            if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3847              continue;
3848            NewF = F;
3849            NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3850          }
3851          NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3852
3853          // If the new formula has a constant in a register, and adding the
3854          // constant value to the immediate would produce a value closer to
3855          // zero than the immediate itself, then the formula isn't worthwhile.
3856          for (SmallVectorImpl<const SCEV *>::const_iterator
3857               J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
3858               J != JE; ++J)
3859            if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
3860              if ((C->getValue()->getValue() + NewF.BaseOffset).abs().slt(
3861                   abs64(NewF.BaseOffset)) &&
3862                  (C->getValue()->getValue() +
3863                   NewF.BaseOffset).countTrailingZeros() >=
3864                   countTrailingZeros<uint64_t>(NewF.BaseOffset))
3865                goto skip_formula;
3866
3867          // Ok, looks good.
3868          NewF.Canonicalize();
3869          (void)InsertFormula(LU, LUIdx, NewF);
3870          break;
3871        skip_formula:;
3872        }
3873      }
3874    }
3875  }
3876}
3877
3878/// GenerateAllReuseFormulae - Generate formulae for each use.
3879void
3880LSRInstance::GenerateAllReuseFormulae() {
3881  // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3882  // queries are more precise.
3883  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3884    LSRUse &LU = Uses[LUIdx];
3885    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3886      GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3887    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3888      GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3889  }
3890  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3891    LSRUse &LU = Uses[LUIdx];
3892    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3893      GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3894    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3895      GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3896    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3897      GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3898    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3899      GenerateScales(LU, LUIdx, LU.Formulae[i]);
3900  }
3901  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3902    LSRUse &LU = Uses[LUIdx];
3903    for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3904      GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3905  }
3906
3907  GenerateCrossUseConstantOffsets();
3908
3909  DEBUG(dbgs() << "\n"
3910                  "After generating reuse formulae:\n";
3911        print_uses(dbgs()));
3912}
3913
3914/// If there are multiple formulae with the same set of registers used
3915/// by other uses, pick the best one and delete the others.
3916void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3917  DenseSet<const SCEV *> VisitedRegs;
3918  SmallPtrSet<const SCEV *, 16> Regs;
3919  SmallPtrSet<const SCEV *, 16> LoserRegs;
3920#ifndef NDEBUG
3921  bool ChangedFormulae = false;
3922#endif
3923
3924  // Collect the best formula for each unique set of shared registers. This
3925  // is reset for each use.
3926  typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>
3927    BestFormulaeTy;
3928  BestFormulaeTy BestFormulae;
3929
3930  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3931    LSRUse &LU = Uses[LUIdx];
3932    DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3933
3934    bool Any = false;
3935    for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3936         FIdx != NumForms; ++FIdx) {
3937      Formula &F = LU.Formulae[FIdx];
3938
3939      // Some formulas are instant losers. For example, they may depend on
3940      // nonexistent AddRecs from other loops. These need to be filtered
3941      // immediately, otherwise heuristics could choose them over others leading
3942      // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3943      // avoids the need to recompute this information across formulae using the
3944      // same bad AddRec. Passing LoserRegs is also essential unless we remove
3945      // the corresponding bad register from the Regs set.
3946      Cost CostF;
3947      Regs.clear();
3948      CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, LU,
3949                        &LoserRegs);
3950      if (CostF.isLoser()) {
3951        // During initial formula generation, undesirable formulae are generated
3952        // by uses within other loops that have some non-trivial address mode or
3953        // use the postinc form of the IV. LSR needs to provide these formulae
3954        // as the basis of rediscovering the desired formula that uses an AddRec
3955        // corresponding to the existing phi. Once all formulae have been
3956        // generated, these initial losers may be pruned.
3957        DEBUG(dbgs() << "  Filtering loser "; F.print(dbgs());
3958              dbgs() << "\n");
3959      }
3960      else {
3961        SmallVector<const SCEV *, 4> Key;
3962        for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
3963               JE = F.BaseRegs.end(); J != JE; ++J) {
3964          const SCEV *Reg = *J;
3965          if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3966            Key.push_back(Reg);
3967        }
3968        if (F.ScaledReg &&
3969            RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3970          Key.push_back(F.ScaledReg);
3971        // Unstable sort by host order ok, because this is only used for
3972        // uniquifying.
3973        std::sort(Key.begin(), Key.end());
3974
3975        std::pair<BestFormulaeTy::const_iterator, bool> P =
3976          BestFormulae.insert(std::make_pair(Key, FIdx));
3977        if (P.second)
3978          continue;
3979
3980        Formula &Best = LU.Formulae[P.first->second];
3981
3982        Cost CostBest;
3983        Regs.clear();
3984        CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, LU.Offsets, SE,
3985                             DT, LU);
3986        if (CostF < CostBest)
3987          std::swap(F, Best);
3988        DEBUG(dbgs() << "  Filtering out formula "; F.print(dbgs());
3989              dbgs() << "\n"
3990                        "    in favor of formula "; Best.print(dbgs());
3991              dbgs() << '\n');
3992      }
3993#ifndef NDEBUG
3994      ChangedFormulae = true;
3995#endif
3996      LU.DeleteFormula(F);
3997      --FIdx;
3998      --NumForms;
3999      Any = true;
4000    }
4001
4002    // Now that we've filtered out some formulae, recompute the Regs set.
4003    if (Any)
4004      LU.RecomputeRegs(LUIdx, RegUses);
4005
4006    // Reset this to prepare for the next use.
4007    BestFormulae.clear();
4008  }
4009
4010  DEBUG(if (ChangedFormulae) {
4011          dbgs() << "\n"
4012                    "After filtering out undesirable candidates:\n";
4013          print_uses(dbgs());
4014        });
4015}
4016
4017// This is a rough guess that seems to work fairly well.
4018static const size_t ComplexityLimit = UINT16_MAX;
4019
4020/// EstimateSearchSpaceComplexity - Estimate the worst-case number of
4021/// solutions the solver might have to consider. It almost never considers
4022/// this many solutions because it prune the search space, but the pruning
4023/// isn't always sufficient.
4024size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4025  size_t Power = 1;
4026  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4027       E = Uses.end(); I != E; ++I) {
4028    size_t FSize = I->Formulae.size();
4029    if (FSize >= ComplexityLimit) {
4030      Power = ComplexityLimit;
4031      break;
4032    }
4033    Power *= FSize;
4034    if (Power >= ComplexityLimit)
4035      break;
4036  }
4037  return Power;
4038}
4039
4040/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
4041/// of the registers of another formula, it won't help reduce register
4042/// pressure (though it may not necessarily hurt register pressure); remove
4043/// it to simplify the system.
4044void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4045  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4046    DEBUG(dbgs() << "The search space is too complex.\n");
4047
4048    DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4049                    "which use a superset of registers used by other "
4050                    "formulae.\n");
4051
4052    for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4053      LSRUse &LU = Uses[LUIdx];
4054      bool Any = false;
4055      for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4056        Formula &F = LU.Formulae[i];
4057        // Look for a formula with a constant or GV in a register. If the use
4058        // also has a formula with that same value in an immediate field,
4059        // delete the one that uses a register.
4060        for (SmallVectorImpl<const SCEV *>::const_iterator
4061             I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4062          if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4063            Formula NewF = F;
4064            NewF.BaseOffset += C->getValue()->getSExtValue();
4065            NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4066                                (I - F.BaseRegs.begin()));
4067            if (LU.HasFormulaWithSameRegs(NewF)) {
4068              DEBUG(dbgs() << "  Deleting "; F.print(dbgs()); dbgs() << '\n');
4069              LU.DeleteFormula(F);
4070              --i;
4071              --e;
4072              Any = true;
4073              break;
4074            }
4075          } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4076            if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4077              if (!F.BaseGV) {
4078                Formula NewF = F;
4079                NewF.BaseGV = GV;
4080                NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4081                                    (I - F.BaseRegs.begin()));
4082                if (LU.HasFormulaWithSameRegs(NewF)) {
4083                  DEBUG(dbgs() << "  Deleting "; F.print(dbgs());
4084                        dbgs() << '\n');
4085                  LU.DeleteFormula(F);
4086                  --i;
4087                  --e;
4088                  Any = true;
4089                  break;
4090                }
4091              }
4092          }
4093        }
4094      }
4095      if (Any)
4096        LU.RecomputeRegs(LUIdx, RegUses);
4097    }
4098
4099    DEBUG(dbgs() << "After pre-selection:\n";
4100          print_uses(dbgs()));
4101  }
4102}
4103
4104/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
4105/// for expressions like A, A+1, A+2, etc., allocate a single register for
4106/// them.
4107void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4108  if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4109    return;
4110
4111  DEBUG(dbgs() << "The search space is too complex.\n"
4112                  "Narrowing the search space by assuming that uses separated "
4113                  "by a constant offset will use the same registers.\n");
4114
4115  // This is especially useful for unrolled loops.
4116
4117  for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4118    LSRUse &LU = Uses[LUIdx];
4119    for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
4120         E = LU.Formulae.end(); I != E; ++I) {
4121      const Formula &F = *I;
4122      if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4123        continue;
4124
4125      LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4126      if (!LUThatHas)
4127        continue;
4128
4129      if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4130                              LU.Kind, LU.AccessTy))
4131        continue;
4132
4133      DEBUG(dbgs() << "  Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4134
4135      LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4136
4137      // Update the relocs to reference the new use.
4138      for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
4139           E = Fixups.end(); I != E; ++I) {
4140        LSRFixup &Fixup = *I;
4141        if (Fixup.LUIdx == LUIdx) {
4142          Fixup.LUIdx = LUThatHas - &Uses.front();
4143          Fixup.Offset += F.BaseOffset;
4144          // Add the new offset to LUThatHas' offset list.
4145          if (LUThatHas->Offsets.back() != Fixup.Offset) {
4146            LUThatHas->Offsets.push_back(Fixup.Offset);
4147            if (Fixup.Offset > LUThatHas->MaxOffset)
4148              LUThatHas->MaxOffset = Fixup.Offset;
4149            if (Fixup.Offset < LUThatHas->MinOffset)
4150              LUThatHas->MinOffset = Fixup.Offset;
4151          }
4152          DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4153        }
4154        if (Fixup.LUIdx == NumUses-1)
4155          Fixup.LUIdx = LUIdx;
4156      }
4157
4158      // Delete formulae from the new use which are no longer legal.
4159      bool Any = false;
4160      for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4161        Formula &F = LUThatHas->Formulae[i];
4162        if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4163                        LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4164          DEBUG(dbgs() << "  Deleting "; F.print(dbgs());
4165                dbgs() << '\n');
4166          LUThatHas->DeleteFormula(F);
4167          --i;
4168          --e;
4169          Any = true;
4170        }
4171      }
4172
4173      if (Any)
4174        LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4175
4176      // Delete the old use.
4177      DeleteUse(LU, LUIdx);
4178      --LUIdx;
4179      --NumUses;
4180      break;
4181    }
4182  }
4183
4184  DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4185}
4186
4187/// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
4188/// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4189/// we've done more filtering, as it may be able to find more formulae to
4190/// eliminate.
4191void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4192  if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4193    DEBUG(dbgs() << "The search space is too complex.\n");
4194
4195    DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4196                    "undesirable dedicated registers.\n");
4197
4198    FilterOutUndesirableDedicatedRegisters();
4199
4200    DEBUG(dbgs() << "After pre-selection:\n";
4201          print_uses(dbgs()));
4202  }
4203}
4204
4205/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
4206/// to be profitable, and then in any use which has any reference to that
4207/// register, delete all formulae which do not reference that register.
4208void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4209  // With all other options exhausted, loop until the system is simple
4210  // enough to handle.
4211  SmallPtrSet<const SCEV *, 4> Taken;
4212  while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4213    // Ok, we have too many of formulae on our hands to conveniently handle.
4214    // Use a rough heuristic to thin out the list.
4215    DEBUG(dbgs() << "The search space is too complex.\n");
4216
4217    // Pick the register which is used by the most LSRUses, which is likely
4218    // to be a good reuse register candidate.
4219    const SCEV *Best = nullptr;
4220    unsigned BestNum = 0;
4221    for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
4222         I != E; ++I) {
4223      const SCEV *Reg = *I;
4224      if (Taken.count(Reg))
4225        continue;
4226      if (!Best)
4227        Best = Reg;
4228      else {
4229        unsigned Count = RegUses.getUsedByIndices(Reg).count();
4230        if (Count > BestNum) {
4231          Best = Reg;
4232          BestNum = Count;
4233        }
4234      }
4235    }
4236
4237    DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4238                 << " will yield profitable reuse.\n");
4239    Taken.insert(Best);
4240
4241    // In any use with formulae which references this register, delete formulae
4242    // which don't reference it.
4243    for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4244      LSRUse &LU = Uses[LUIdx];
4245      if (!LU.Regs.count(Best)) continue;
4246
4247      bool Any = false;
4248      for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4249        Formula &F = LU.Formulae[i];
4250        if (!F.referencesReg(Best)) {
4251          DEBUG(dbgs() << "  Deleting "; F.print(dbgs()); dbgs() << '\n');
4252          LU.DeleteFormula(F);
4253          --e;
4254          --i;
4255          Any = true;
4256          assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4257          continue;
4258        }
4259      }
4260
4261      if (Any)
4262        LU.RecomputeRegs(LUIdx, RegUses);
4263    }
4264
4265    DEBUG(dbgs() << "After pre-selection:\n";
4266          print_uses(dbgs()));
4267  }
4268}
4269
4270/// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
4271/// formulae to choose from, use some rough heuristics to prune down the number
4272/// of formulae. This keeps the main solver from taking an extraordinary amount
4273/// of time in some worst-case scenarios.
4274void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4275  NarrowSearchSpaceByDetectingSupersets();
4276  NarrowSearchSpaceByCollapsingUnrolledCode();
4277  NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4278  NarrowSearchSpaceByPickingWinnerRegs();
4279}
4280
4281/// SolveRecurse - This is the recursive solver.
4282void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4283                               Cost &SolutionCost,
4284                               SmallVectorImpl<const Formula *> &Workspace,
4285                               const Cost &CurCost,
4286                               const SmallPtrSet<const SCEV *, 16> &CurRegs,
4287                               DenseSet<const SCEV *> &VisitedRegs) const {
4288  // Some ideas:
4289  //  - prune more:
4290  //    - use more aggressive filtering
4291  //    - sort the formula so that the most profitable solutions are found first
4292  //    - sort the uses too
4293  //  - search faster:
4294  //    - don't compute a cost, and then compare. compare while computing a cost
4295  //      and bail early.
4296  //    - track register sets with SmallBitVector
4297
4298  const LSRUse &LU = Uses[Workspace.size()];
4299
4300  // If this use references any register that's already a part of the
4301  // in-progress solution, consider it a requirement that a formula must
4302  // reference that register in order to be considered. This prunes out
4303  // unprofitable searching.
4304  SmallSetVector<const SCEV *, 4> ReqRegs;
4305  for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
4306       E = CurRegs.end(); I != E; ++I)
4307    if (LU.Regs.count(*I))
4308      ReqRegs.insert(*I);
4309
4310  SmallPtrSet<const SCEV *, 16> NewRegs;
4311  Cost NewCost;
4312  for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
4313       E = LU.Formulae.end(); I != E; ++I) {
4314    const Formula &F = *I;
4315
4316    // Ignore formulae which may not be ideal in terms of register reuse of
4317    // ReqRegs.  The formula should use all required registers before
4318    // introducing new ones.
4319    int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4320    for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
4321         JE = ReqRegs.end(); J != JE; ++J) {
4322      const SCEV *Reg = *J;
4323      if ((F.ScaledReg && F.ScaledReg == Reg) ||
4324          std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) !=
4325          F.BaseRegs.end()) {
4326        --NumReqRegsToFind;
4327        if (NumReqRegsToFind == 0)
4328          break;
4329      }
4330    }
4331    if (NumReqRegsToFind != 0) {
4332      // If none of the formulae satisfied the required registers, then we could
4333      // clear ReqRegs and try again. Currently, we simply give up in this case.
4334      continue;
4335    }
4336
4337    // Evaluate the cost of the current formula. If it's already worse than
4338    // the current best, prune the search at that point.
4339    NewCost = CurCost;
4340    NewRegs = CurRegs;
4341    NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT,
4342                        LU);
4343    if (NewCost < SolutionCost) {
4344      Workspace.push_back(&F);
4345      if (Workspace.size() != Uses.size()) {
4346        SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4347                     NewRegs, VisitedRegs);
4348        if (F.getNumRegs() == 1 && Workspace.size() == 1)
4349          VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4350      } else {
4351        DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4352              dbgs() << ".\n Regs:";
4353              for (SmallPtrSet<const SCEV *, 16>::const_iterator
4354                   I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
4355                dbgs() << ' ' << **I;
4356              dbgs() << '\n');
4357
4358        SolutionCost = NewCost;
4359        Solution = Workspace;
4360      }
4361      Workspace.pop_back();
4362    }
4363  }
4364}
4365
4366/// Solve - Choose one formula from each use. Return the results in the given
4367/// Solution vector.
4368void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4369  SmallVector<const Formula *, 8> Workspace;
4370  Cost SolutionCost;
4371  SolutionCost.Lose();
4372  Cost CurCost;
4373  SmallPtrSet<const SCEV *, 16> CurRegs;
4374  DenseSet<const SCEV *> VisitedRegs;
4375  Workspace.reserve(Uses.size());
4376
4377  // SolveRecurse does all the work.
4378  SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4379               CurRegs, VisitedRegs);
4380  if (Solution.empty()) {
4381    DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4382    return;
4383  }
4384
4385  // Ok, we've now made all our decisions.
4386  DEBUG(dbgs() << "\n"
4387                  "The chosen solution requires "; SolutionCost.print(dbgs());
4388        dbgs() << ":\n";
4389        for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4390          dbgs() << "  ";
4391          Uses[i].print(dbgs());
4392          dbgs() << "\n"
4393                    "    ";
4394          Solution[i]->print(dbgs());
4395          dbgs() << '\n';
4396        });
4397
4398  assert(Solution.size() == Uses.size() && "Malformed solution!");
4399}
4400
4401/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4402/// the dominator tree far as we can go while still being dominated by the
4403/// input positions. This helps canonicalize the insert position, which
4404/// encourages sharing.
4405BasicBlock::iterator
4406LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4407                                 const SmallVectorImpl<Instruction *> &Inputs)
4408                                                                         const {
4409  for (;;) {
4410    const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4411    unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4412
4413    BasicBlock *IDom;
4414    for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4415      if (!Rung) return IP;
4416      Rung = Rung->getIDom();
4417      if (!Rung) return IP;
4418      IDom = Rung->getBlock();
4419
4420      // Don't climb into a loop though.
4421      const Loop *IDomLoop = LI.getLoopFor(IDom);
4422      unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4423      if (IDomDepth <= IPLoopDepth &&
4424          (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4425        break;
4426    }
4427
4428    bool AllDominate = true;
4429    Instruction *BetterPos = nullptr;
4430    Instruction *Tentative = IDom->getTerminator();
4431    for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
4432         E = Inputs.end(); I != E; ++I) {
4433      Instruction *Inst = *I;
4434      if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4435        AllDominate = false;
4436        break;
4437      }
4438      // Attempt to find an insert position in the middle of the block,
4439      // instead of at the end, so that it can be used for other expansions.
4440      if (IDom == Inst->getParent() &&
4441          (!BetterPos || !DT.dominates(Inst, BetterPos)))
4442        BetterPos = std::next(BasicBlock::iterator(Inst));
4443    }
4444    if (!AllDominate)
4445      break;
4446    if (BetterPos)
4447      IP = BetterPos;
4448    else
4449      IP = Tentative;
4450  }
4451
4452  return IP;
4453}
4454
4455/// AdjustInsertPositionForExpand - Determine an input position which will be
4456/// dominated by the operands and which will dominate the result.
4457BasicBlock::iterator
4458LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4459                                           const LSRFixup &LF,
4460                                           const LSRUse &LU,
4461                                           SCEVExpander &Rewriter) const {
4462  // Collect some instructions which must be dominated by the
4463  // expanding replacement. These must be dominated by any operands that
4464  // will be required in the expansion.
4465  SmallVector<Instruction *, 4> Inputs;
4466  if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4467    Inputs.push_back(I);
4468  if (LU.Kind == LSRUse::ICmpZero)
4469    if (Instruction *I =
4470          dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4471      Inputs.push_back(I);
4472  if (LF.PostIncLoops.count(L)) {
4473    if (LF.isUseFullyOutsideLoop(L))
4474      Inputs.push_back(L->getLoopLatch()->getTerminator());
4475    else
4476      Inputs.push_back(IVIncInsertPos);
4477  }
4478  // The expansion must also be dominated by the increment positions of any
4479  // loops it for which it is using post-inc mode.
4480  for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
4481       E = LF.PostIncLoops.end(); I != E; ++I) {
4482    const Loop *PIL = *I;
4483    if (PIL == L) continue;
4484
4485    // Be dominated by the loop exit.
4486    SmallVector<BasicBlock *, 4> ExitingBlocks;
4487    PIL->getExitingBlocks(ExitingBlocks);
4488    if (!ExitingBlocks.empty()) {
4489      BasicBlock *BB = ExitingBlocks[0];
4490      for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4491        BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4492      Inputs.push_back(BB->getTerminator());
4493    }
4494  }
4495
4496  assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4497         && !isa<DbgInfoIntrinsic>(LowestIP) &&
4498         "Insertion point must be a normal instruction");
4499
4500  // Then, climb up the immediate dominator tree as far as we can go while
4501  // still being dominated by the input positions.
4502  BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4503
4504  // Don't insert instructions before PHI nodes.
4505  while (isa<PHINode>(IP)) ++IP;
4506
4507  // Ignore landingpad instructions.
4508  while (isa<LandingPadInst>(IP)) ++IP;
4509
4510  // Ignore debug intrinsics.
4511  while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4512
4513  // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4514  // IP consistent across expansions and allows the previously inserted
4515  // instructions to be reused by subsequent expansion.
4516  while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4517
4518  return IP;
4519}
4520
4521/// Expand - Emit instructions for the leading candidate expression for this
4522/// LSRUse (this is called "expanding").
4523Value *LSRInstance::Expand(const LSRFixup &LF,
4524                           const Formula &F,
4525                           BasicBlock::iterator IP,
4526                           SCEVExpander &Rewriter,
4527                           SmallVectorImpl<WeakVH> &DeadInsts) const {
4528  const LSRUse &LU = Uses[LF.LUIdx];
4529  if (LU.RigidFormula)
4530    return LF.OperandValToReplace;
4531
4532  // Determine an input position which will be dominated by the operands and
4533  // which will dominate the result.
4534  IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4535
4536  // Inform the Rewriter if we have a post-increment use, so that it can
4537  // perform an advantageous expansion.
4538  Rewriter.setPostInc(LF.PostIncLoops);
4539
4540  // This is the type that the user actually needs.
4541  Type *OpTy = LF.OperandValToReplace->getType();
4542  // This will be the type that we'll initially expand to.
4543  Type *Ty = F.getType();
4544  if (!Ty)
4545    // No type known; just expand directly to the ultimate type.
4546    Ty = OpTy;
4547  else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4548    // Expand directly to the ultimate type if it's the right size.
4549    Ty = OpTy;
4550  // This is the type to do integer arithmetic in.
4551  Type *IntTy = SE.getEffectiveSCEVType(Ty);
4552
4553  // Build up a list of operands to add together to form the full base.
4554  SmallVector<const SCEV *, 8> Ops;
4555
4556  // Expand the BaseRegs portion.
4557  for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
4558       E = F.BaseRegs.end(); I != E; ++I) {
4559    const SCEV *Reg = *I;
4560    assert(!Reg->isZero() && "Zero allocated in a base register!");
4561
4562    // If we're expanding for a post-inc user, make the post-inc adjustment.
4563    PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4564    Reg = TransformForPostIncUse(Denormalize, Reg,
4565                                 LF.UserInst, LF.OperandValToReplace,
4566                                 Loops, SE, DT);
4567
4568    Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr, IP)));
4569  }
4570
4571  // Expand the ScaledReg portion.
4572  Value *ICmpScaledV = nullptr;
4573  if (F.Scale != 0) {
4574    const SCEV *ScaledS = F.ScaledReg;
4575
4576    // If we're expanding for a post-inc user, make the post-inc adjustment.
4577    PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4578    ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4579                                     LF.UserInst, LF.OperandValToReplace,
4580                                     Loops, SE, DT);
4581
4582    if (LU.Kind == LSRUse::ICmpZero) {
4583      // Expand ScaleReg as if it was part of the base regs.
4584      if (F.Scale == 1)
4585        Ops.push_back(
4586            SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, IP)));
4587      else {
4588        // An interesting way of "folding" with an icmp is to use a negated
4589        // scale, which we'll implement by inserting it into the other operand
4590        // of the icmp.
4591        assert(F.Scale == -1 &&
4592               "The only scale supported by ICmpZero uses is -1!");
4593        ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr, IP);
4594      }
4595    } else {
4596      // Otherwise just expand the scaled register and an explicit scale,
4597      // which is expected to be matched as part of the address.
4598
4599      // Flush the operand list to suppress SCEVExpander hoisting address modes.
4600      // Unless the addressing mode will not be folded.
4601      if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4602          isAMCompletelyFolded(TTI, LU, F)) {
4603        Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4604        Ops.clear();
4605        Ops.push_back(SE.getUnknown(FullV));
4606      }
4607      ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, IP));
4608      if (F.Scale != 1)
4609        ScaledS =
4610            SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
4611      Ops.push_back(ScaledS);
4612    }
4613  }
4614
4615  // Expand the GV portion.
4616  if (F.BaseGV) {
4617    // Flush the operand list to suppress SCEVExpander hoisting.
4618    if (!Ops.empty()) {
4619      Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4620      Ops.clear();
4621      Ops.push_back(SE.getUnknown(FullV));
4622    }
4623    Ops.push_back(SE.getUnknown(F.BaseGV));
4624  }
4625
4626  // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4627  // unfolded offsets. LSR assumes they both live next to their uses.
4628  if (!Ops.empty()) {
4629    Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4630    Ops.clear();
4631    Ops.push_back(SE.getUnknown(FullV));
4632  }
4633
4634  // Expand the immediate portion.
4635  int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
4636  if (Offset != 0) {
4637    if (LU.Kind == LSRUse::ICmpZero) {
4638      // The other interesting way of "folding" with an ICmpZero is to use a
4639      // negated immediate.
4640      if (!ICmpScaledV)
4641        ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4642      else {
4643        Ops.push_back(SE.getUnknown(ICmpScaledV));
4644        ICmpScaledV = ConstantInt::get(IntTy, Offset);
4645      }
4646    } else {
4647      // Just add the immediate values. These again are expected to be matched
4648      // as part of the address.
4649      Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4650    }
4651  }
4652
4653  // Expand the unfolded offset portion.
4654  int64_t UnfoldedOffset = F.UnfoldedOffset;
4655  if (UnfoldedOffset != 0) {
4656    // Just add the immediate values.
4657    Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4658                                                       UnfoldedOffset)));
4659  }
4660
4661  // Emit instructions summing all the operands.
4662  const SCEV *FullS = Ops.empty() ?
4663                      SE.getConstant(IntTy, 0) :
4664                      SE.getAddExpr(Ops);
4665  Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4666
4667  // We're done expanding now, so reset the rewriter.
4668  Rewriter.clearPostInc();
4669
4670  // An ICmpZero Formula represents an ICmp which we're handling as a
4671  // comparison against zero. Now that we've expanded an expression for that
4672  // form, update the ICmp's other operand.
4673  if (LU.Kind == LSRUse::ICmpZero) {
4674    ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4675    DeadInsts.push_back(CI->getOperand(1));
4676    assert(!F.BaseGV && "ICmp does not support folding a global value and "
4677                           "a scale at the same time!");
4678    if (F.Scale == -1) {
4679      if (ICmpScaledV->getType() != OpTy) {
4680        Instruction *Cast =
4681          CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4682                                                   OpTy, false),
4683                           ICmpScaledV, OpTy, "tmp", CI);
4684        ICmpScaledV = Cast;
4685      }
4686      CI->setOperand(1, ICmpScaledV);
4687    } else {
4688      // A scale of 1 means that the scale has been expanded as part of the
4689      // base regs.
4690      assert((F.Scale == 0 || F.Scale == 1) &&
4691             "ICmp does not support folding a global value and "
4692             "a scale at the same time!");
4693      Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4694                                           -(uint64_t)Offset);
4695      if (C->getType() != OpTy)
4696        C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4697                                                          OpTy, false),
4698                                  C, OpTy);
4699
4700      CI->setOperand(1, C);
4701    }
4702  }
4703
4704  return FullV;
4705}
4706
4707/// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4708/// of their operands effectively happens in their predecessor blocks, so the
4709/// expression may need to be expanded in multiple places.
4710void LSRInstance::RewriteForPHI(PHINode *PN,
4711                                const LSRFixup &LF,
4712                                const Formula &F,
4713                                SCEVExpander &Rewriter,
4714                                SmallVectorImpl<WeakVH> &DeadInsts,
4715                                Pass *P) const {
4716  DenseMap<BasicBlock *, Value *> Inserted;
4717  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4718    if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4719      BasicBlock *BB = PN->getIncomingBlock(i);
4720
4721      // If this is a critical edge, split the edge so that we do not insert
4722      // the code on all predecessor/successor paths.  We do this unless this
4723      // is the canonical backedge for this loop, which complicates post-inc
4724      // users.
4725      if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4726          !isa<IndirectBrInst>(BB->getTerminator())) {
4727        BasicBlock *Parent = PN->getParent();
4728        Loop *PNLoop = LI.getLoopFor(Parent);
4729        if (!PNLoop || Parent != PNLoop->getHeader()) {
4730          // Split the critical edge.
4731          BasicBlock *NewBB = nullptr;
4732          if (!Parent->isLandingPad()) {
4733            NewBB = SplitCriticalEdge(BB, Parent, P,
4734                                      /*MergeIdenticalEdges=*/true,
4735                                      /*DontDeleteUselessPhis=*/true);
4736          } else {
4737            SmallVector<BasicBlock*, 2> NewBBs;
4738            SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
4739            NewBB = NewBBs[0];
4740          }
4741          // If NewBB==NULL, then SplitCriticalEdge refused to split because all
4742          // phi predecessors are identical. The simple thing to do is skip
4743          // splitting in this case rather than complicate the API.
4744          if (NewBB) {
4745            // If PN is outside of the loop and BB is in the loop, we want to
4746            // move the block to be immediately before the PHI block, not
4747            // immediately after BB.
4748            if (L->contains(BB) && !L->contains(PN))
4749              NewBB->moveBefore(PN->getParent());
4750
4751            // Splitting the edge can reduce the number of PHI entries we have.
4752            e = PN->getNumIncomingValues();
4753            BB = NewBB;
4754            i = PN->getBasicBlockIndex(BB);
4755          }
4756        }
4757      }
4758
4759      std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4760        Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
4761      if (!Pair.second)
4762        PN->setIncomingValue(i, Pair.first->second);
4763      else {
4764        Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4765
4766        // If this is reuse-by-noop-cast, insert the noop cast.
4767        Type *OpTy = LF.OperandValToReplace->getType();
4768        if (FullV->getType() != OpTy)
4769          FullV =
4770            CastInst::Create(CastInst::getCastOpcode(FullV, false,
4771                                                     OpTy, false),
4772                             FullV, LF.OperandValToReplace->getType(),
4773                             "tmp", BB->getTerminator());
4774
4775        PN->setIncomingValue(i, FullV);
4776        Pair.first->second = FullV;
4777      }
4778    }
4779}
4780
4781/// Rewrite - Emit instructions for the leading candidate expression for this
4782/// LSRUse (this is called "expanding"), and update the UserInst to reference
4783/// the newly expanded value.
4784void LSRInstance::Rewrite(const LSRFixup &LF,
4785                          const Formula &F,
4786                          SCEVExpander &Rewriter,
4787                          SmallVectorImpl<WeakVH> &DeadInsts,
4788                          Pass *P) const {
4789  // First, find an insertion point that dominates UserInst. For PHI nodes,
4790  // find the nearest block which dominates all the relevant uses.
4791  if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4792    RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4793  } else {
4794    Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4795
4796    // If this is reuse-by-noop-cast, insert the noop cast.
4797    Type *OpTy = LF.OperandValToReplace->getType();
4798    if (FullV->getType() != OpTy) {
4799      Instruction *Cast =
4800        CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4801                         FullV, OpTy, "tmp", LF.UserInst);
4802      FullV = Cast;
4803    }
4804
4805    // Update the user. ICmpZero is handled specially here (for now) because
4806    // Expand may have updated one of the operands of the icmp already, and
4807    // its new value may happen to be equal to LF.OperandValToReplace, in
4808    // which case doing replaceUsesOfWith leads to replacing both operands
4809    // with the same value. TODO: Reorganize this.
4810    if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4811      LF.UserInst->setOperand(0, FullV);
4812    else
4813      LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4814  }
4815
4816  DeadInsts.push_back(LF.OperandValToReplace);
4817}
4818
4819/// ImplementSolution - Rewrite all the fixup locations with new values,
4820/// following the chosen solution.
4821void
4822LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4823                               Pass *P) {
4824  // Keep track of instructions we may have made dead, so that
4825  // we can remove them after we are done working.
4826  SmallVector<WeakVH, 16> DeadInsts;
4827
4828  SCEVExpander Rewriter(SE, "lsr");
4829#ifndef NDEBUG
4830  Rewriter.setDebugType(DEBUG_TYPE);
4831#endif
4832  Rewriter.disableCanonicalMode();
4833  Rewriter.enableLSRMode();
4834  Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4835
4836  // Mark phi nodes that terminate chains so the expander tries to reuse them.
4837  for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4838         ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4839    if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst()))
4840      Rewriter.setChainedPhi(PN);
4841  }
4842
4843  // Expand the new value definitions and update the users.
4844  for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4845       E = Fixups.end(); I != E; ++I) {
4846    const LSRFixup &Fixup = *I;
4847
4848    Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4849
4850    Changed = true;
4851  }
4852
4853  for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4854         ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4855    GenerateIVChain(*ChainI, Rewriter, DeadInsts);
4856    Changed = true;
4857  }
4858  // Clean up after ourselves. This must be done before deleting any
4859  // instructions.
4860  Rewriter.clear();
4861
4862  Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4863}
4864
4865LSRInstance::LSRInstance(Loop *L, Pass *P)
4866    : IU(P->getAnalysis<IVUsers>()), SE(P->getAnalysis<ScalarEvolution>()),
4867      DT(P->getAnalysis<DominatorTreeWrapperPass>().getDomTree()),
4868      LI(P->getAnalysis<LoopInfo>()),
4869      TTI(P->getAnalysis<TargetTransformInfo>()), L(L), Changed(false),
4870      IVIncInsertPos(nullptr) {
4871  // If LoopSimplify form is not available, stay out of trouble.
4872  if (!L->isLoopSimplifyForm())
4873    return;
4874
4875  // If there's no interesting work to be done, bail early.
4876  if (IU.empty()) return;
4877
4878  // If there's too much analysis to be done, bail early. We won't be able to
4879  // model the problem anyway.
4880  unsigned NumUsers = 0;
4881  for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
4882    if (++NumUsers > MaxIVUsers) {
4883      DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L
4884            << "\n");
4885      return;
4886    }
4887  }
4888
4889#ifndef NDEBUG
4890  // All dominating loops must have preheaders, or SCEVExpander may not be able
4891  // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4892  //
4893  // IVUsers analysis should only create users that are dominated by simple loop
4894  // headers. Since this loop should dominate all of its users, its user list
4895  // should be empty if this loop itself is not within a simple loop nest.
4896  for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4897       Rung; Rung = Rung->getIDom()) {
4898    BasicBlock *BB = Rung->getBlock();
4899    const Loop *DomLoop = LI.getLoopFor(BB);
4900    if (DomLoop && DomLoop->getHeader() == BB) {
4901      assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4902    }
4903  }
4904#endif // DEBUG
4905
4906  DEBUG(dbgs() << "\nLSR on loop ";
4907        L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
4908        dbgs() << ":\n");
4909
4910  // First, perform some low-level loop optimizations.
4911  OptimizeShadowIV();
4912  OptimizeLoopTermCond();
4913
4914  // If loop preparation eliminates all interesting IV users, bail.
4915  if (IU.empty()) return;
4916
4917  // Skip nested loops until we can model them better with formulae.
4918  if (!L->empty()) {
4919    DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4920    return;
4921  }
4922
4923  // Start collecting data and preparing for the solver.
4924  CollectChains();
4925  CollectInterestingTypesAndFactors();
4926  CollectFixupsAndInitialFormulae();
4927  CollectLoopInvariantFixupsAndFormulae();
4928
4929  assert(!Uses.empty() && "IVUsers reported at least one use");
4930  DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4931        print_uses(dbgs()));
4932
4933  // Now use the reuse data to generate a bunch of interesting ways
4934  // to formulate the values needed for the uses.
4935  GenerateAllReuseFormulae();
4936
4937  FilterOutUndesirableDedicatedRegisters();
4938  NarrowSearchSpaceUsingHeuristics();
4939
4940  SmallVector<const Formula *, 8> Solution;
4941  Solve(Solution);
4942
4943  // Release memory that is no longer needed.
4944  Factors.clear();
4945  Types.clear();
4946  RegUses.clear();
4947
4948  if (Solution.empty())
4949    return;
4950
4951#ifndef NDEBUG
4952  // Formulae should be legal.
4953  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), E = Uses.end();
4954       I != E; ++I) {
4955    const LSRUse &LU = *I;
4956    for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4957                                                  JE = LU.Formulae.end();
4958         J != JE; ++J)
4959      assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4960                        *J) && "Illegal formula generated!");
4961  };
4962#endif
4963
4964  // Now that we've decided what we want, make it so.
4965  ImplementSolution(Solution, P);
4966}
4967
4968void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4969  if (Factors.empty() && Types.empty()) return;
4970
4971  OS << "LSR has identified the following interesting factors and types: ";
4972  bool First = true;
4973
4974  for (SmallSetVector<int64_t, 8>::const_iterator
4975       I = Factors.begin(), E = Factors.end(); I != E; ++I) {
4976    if (!First) OS << ", ";
4977    First = false;
4978    OS << '*' << *I;
4979  }
4980
4981  for (SmallSetVector<Type *, 4>::const_iterator
4982       I = Types.begin(), E = Types.end(); I != E; ++I) {
4983    if (!First) OS << ", ";
4984    First = false;
4985    OS << '(' << **I << ')';
4986  }
4987  OS << '\n';
4988}
4989
4990void LSRInstance::print_fixups(raw_ostream &OS) const {
4991  OS << "LSR is examining the following fixup sites:\n";
4992  for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4993       E = Fixups.end(); I != E; ++I) {
4994    dbgs() << "  ";
4995    I->print(OS);
4996    OS << '\n';
4997  }
4998}
4999
5000void LSRInstance::print_uses(raw_ostream &OS) const {
5001  OS << "LSR is examining the following uses:\n";
5002  for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
5003       E = Uses.end(); I != E; ++I) {
5004    const LSRUse &LU = *I;
5005    dbgs() << "  ";
5006    LU.print(OS);
5007    OS << '\n';
5008    for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
5009         JE = LU.Formulae.end(); J != JE; ++J) {
5010      OS << "    ";
5011      J->print(OS);
5012      OS << '\n';
5013    }
5014  }
5015}
5016
5017void LSRInstance::print(raw_ostream &OS) const {
5018  print_factors_and_types(OS);
5019  print_fixups(OS);
5020  print_uses(OS);
5021}
5022
5023#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5024void LSRInstance::dump() const {
5025  print(errs()); errs() << '\n';
5026}
5027#endif
5028
5029namespace {
5030
5031class LoopStrengthReduce : public LoopPass {
5032public:
5033  static char ID; // Pass ID, replacement for typeid
5034  LoopStrengthReduce();
5035
5036private:
5037  bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5038  void getAnalysisUsage(AnalysisUsage &AU) const override;
5039};
5040
5041}
5042
5043char LoopStrengthReduce::ID = 0;
5044INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5045                "Loop Strength Reduction", false, false)
5046INITIALIZE_AG_DEPENDENCY(TargetTransformInfo)
5047INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
5048INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
5049INITIALIZE_PASS_DEPENDENCY(IVUsers)
5050INITIALIZE_PASS_DEPENDENCY(LoopInfo)
5051INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5052INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5053                "Loop Strength Reduction", false, false)
5054
5055
5056Pass *llvm::createLoopStrengthReducePass() {
5057  return new LoopStrengthReduce();
5058}
5059
5060LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5061  initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5062}
5063
5064void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5065  // We split critical edges, so we change the CFG.  However, we do update
5066  // many analyses if they are around.
5067  AU.addPreservedID(LoopSimplifyID);
5068
5069  AU.addRequired<LoopInfo>();
5070  AU.addPreserved<LoopInfo>();
5071  AU.addRequiredID(LoopSimplifyID);
5072  AU.addRequired<DominatorTreeWrapperPass>();
5073  AU.addPreserved<DominatorTreeWrapperPass>();
5074  AU.addRequired<ScalarEvolution>();
5075  AU.addPreserved<ScalarEvolution>();
5076  // Requiring LoopSimplify a second time here prevents IVUsers from running
5077  // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5078  AU.addRequiredID(LoopSimplifyID);
5079  AU.addRequired<IVUsers>();
5080  AU.addPreserved<IVUsers>();
5081  AU.addRequired<TargetTransformInfo>();
5082}
5083
5084bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5085  if (skipOptnoneFunction(L))
5086    return false;
5087
5088  bool Changed = false;
5089
5090  // Run the main LSR transformation.
5091  Changed |= LSRInstance(L, this).getChanged();
5092
5093  // Remove any extra phis created by processing inner loops.
5094  Changed |= DeleteDeadPHIs(L->getHeader());
5095  if (EnablePhiElim && L->isLoopSimplifyForm()) {
5096    SmallVector<WeakVH, 16> DeadInsts;
5097    SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
5098#ifndef NDEBUG
5099    Rewriter.setDebugType(DEBUG_TYPE);
5100#endif
5101    unsigned numFolded = Rewriter.replaceCongruentIVs(
5102        L, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), DeadInsts,
5103        &getAnalysis<TargetTransformInfo>());
5104    if (numFolded) {
5105      Changed = true;
5106      DeleteTriviallyDeadInstructions(DeadInsts);
5107      DeleteDeadPHIs(L->getHeader());
5108    }
5109  }
5110  return Changed;
5111}
5112