1//===- GVN.cpp - Eliminate redundant values and loads ---------------------===//
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 pass performs global value numbering to eliminate fully redundant
11// instructions.  It also performs simple dead load elimination.
12//
13// Note that this pass does the value numbering itself; it does not use the
14// ValueNumbering analysis passes.
15//
16//===----------------------------------------------------------------------===//
17
18#include "llvm/Transforms/Scalar.h"
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/ADT/DepthFirstIterator.h"
21#include "llvm/ADT/Hashing.h"
22#include "llvm/ADT/MapVector.h"
23#include "llvm/ADT/SetVector.h"
24#include "llvm/ADT/SmallPtrSet.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Analysis/CFG.h"
28#include "llvm/Analysis/ConstantFolding.h"
29#include "llvm/Analysis/InstructionSimplify.h"
30#include "llvm/Analysis/Loads.h"
31#include "llvm/Analysis/MemoryBuiltins.h"
32#include "llvm/Analysis/MemoryDependenceAnalysis.h"
33#include "llvm/Analysis/PHITransAddr.h"
34#include "llvm/Analysis/ValueTracking.h"
35#include "llvm/IR/DataLayout.h"
36#include "llvm/IR/Dominators.h"
37#include "llvm/IR/GlobalVariable.h"
38#include "llvm/IR/IRBuilder.h"
39#include "llvm/IR/IntrinsicInst.h"
40#include "llvm/IR/LLVMContext.h"
41#include "llvm/IR/Metadata.h"
42#include "llvm/IR/PatternMatch.h"
43#include "llvm/Support/Allocator.h"
44#include "llvm/Support/CommandLine.h"
45#include "llvm/Support/Debug.h"
46#include "llvm/Target/TargetLibraryInfo.h"
47#include "llvm/Transforms/Utils/BasicBlockUtils.h"
48#include "llvm/Transforms/Utils/SSAUpdater.h"
49#include <vector>
50using namespace llvm;
51using namespace PatternMatch;
52
53#define DEBUG_TYPE "gvn"
54
55STATISTIC(NumGVNInstr,  "Number of instructions deleted");
56STATISTIC(NumGVNLoad,   "Number of loads deleted");
57STATISTIC(NumGVNPRE,    "Number of instructions PRE'd");
58STATISTIC(NumGVNBlocks, "Number of blocks merged");
59STATISTIC(NumGVNSimpl,  "Number of instructions simplified");
60STATISTIC(NumGVNEqProp, "Number of equalities propagated");
61STATISTIC(NumPRELoad,   "Number of loads PRE'd");
62
63static cl::opt<bool> EnablePRE("enable-pre",
64                               cl::init(true), cl::Hidden);
65static cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true));
66
67// Maximum allowed recursion depth.
68static cl::opt<uint32_t>
69MaxRecurseDepth("max-recurse-depth", cl::Hidden, cl::init(1000), cl::ZeroOrMore,
70                cl::desc("Max recurse depth (default = 1000)"));
71
72//===----------------------------------------------------------------------===//
73//                         ValueTable Class
74//===----------------------------------------------------------------------===//
75
76/// This class holds the mapping between values and value numbers.  It is used
77/// as an efficient mechanism to determine the expression-wise equivalence of
78/// two values.
79namespace {
80  struct Expression {
81    uint32_t opcode;
82    Type *type;
83    SmallVector<uint32_t, 4> varargs;
84
85    Expression(uint32_t o = ~2U) : opcode(o) { }
86
87    bool operator==(const Expression &other) const {
88      if (opcode != other.opcode)
89        return false;
90      if (opcode == ~0U || opcode == ~1U)
91        return true;
92      if (type != other.type)
93        return false;
94      if (varargs != other.varargs)
95        return false;
96      return true;
97    }
98
99    friend hash_code hash_value(const Expression &Value) {
100      return hash_combine(Value.opcode, Value.type,
101                          hash_combine_range(Value.varargs.begin(),
102                                             Value.varargs.end()));
103    }
104  };
105
106  class ValueTable {
107    DenseMap<Value*, uint32_t> valueNumbering;
108    DenseMap<Expression, uint32_t> expressionNumbering;
109    AliasAnalysis *AA;
110    MemoryDependenceAnalysis *MD;
111    DominatorTree *DT;
112
113    uint32_t nextValueNumber;
114
115    Expression create_expression(Instruction* I);
116    Expression create_cmp_expression(unsigned Opcode,
117                                     CmpInst::Predicate Predicate,
118                                     Value *LHS, Value *RHS);
119    Expression create_extractvalue_expression(ExtractValueInst* EI);
120    uint32_t lookup_or_add_call(CallInst* C);
121  public:
122    ValueTable() : nextValueNumber(1) { }
123    uint32_t lookup_or_add(Value *V);
124    uint32_t lookup(Value *V) const;
125    uint32_t lookup_or_add_cmp(unsigned Opcode, CmpInst::Predicate Pred,
126                               Value *LHS, Value *RHS);
127    void add(Value *V, uint32_t num);
128    void clear();
129    void erase(Value *v);
130    void setAliasAnalysis(AliasAnalysis* A) { AA = A; }
131    AliasAnalysis *getAliasAnalysis() const { return AA; }
132    void setMemDep(MemoryDependenceAnalysis* M) { MD = M; }
133    void setDomTree(DominatorTree* D) { DT = D; }
134    uint32_t getNextUnusedValueNumber() { return nextValueNumber; }
135    void verifyRemoved(const Value *) const;
136  };
137}
138
139namespace llvm {
140template <> struct DenseMapInfo<Expression> {
141  static inline Expression getEmptyKey() {
142    return ~0U;
143  }
144
145  static inline Expression getTombstoneKey() {
146    return ~1U;
147  }
148
149  static unsigned getHashValue(const Expression e) {
150    using llvm::hash_value;
151    return static_cast<unsigned>(hash_value(e));
152  }
153  static bool isEqual(const Expression &LHS, const Expression &RHS) {
154    return LHS == RHS;
155  }
156};
157
158}
159
160//===----------------------------------------------------------------------===//
161//                     ValueTable Internal Functions
162//===----------------------------------------------------------------------===//
163
164Expression ValueTable::create_expression(Instruction *I) {
165  Expression e;
166  e.type = I->getType();
167  e.opcode = I->getOpcode();
168  for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
169       OI != OE; ++OI)
170    e.varargs.push_back(lookup_or_add(*OI));
171  if (I->isCommutative()) {
172    // Ensure that commutative instructions that only differ by a permutation
173    // of their operands get the same value number by sorting the operand value
174    // numbers.  Since all commutative instructions have two operands it is more
175    // efficient to sort by hand rather than using, say, std::sort.
176    assert(I->getNumOperands() == 2 && "Unsupported commutative instruction!");
177    if (e.varargs[0] > e.varargs[1])
178      std::swap(e.varargs[0], e.varargs[1]);
179  }
180
181  if (CmpInst *C = dyn_cast<CmpInst>(I)) {
182    // Sort the operand value numbers so x<y and y>x get the same value number.
183    CmpInst::Predicate Predicate = C->getPredicate();
184    if (e.varargs[0] > e.varargs[1]) {
185      std::swap(e.varargs[0], e.varargs[1]);
186      Predicate = CmpInst::getSwappedPredicate(Predicate);
187    }
188    e.opcode = (C->getOpcode() << 8) | Predicate;
189  } else if (InsertValueInst *E = dyn_cast<InsertValueInst>(I)) {
190    for (InsertValueInst::idx_iterator II = E->idx_begin(), IE = E->idx_end();
191         II != IE; ++II)
192      e.varargs.push_back(*II);
193  }
194
195  return e;
196}
197
198Expression ValueTable::create_cmp_expression(unsigned Opcode,
199                                             CmpInst::Predicate Predicate,
200                                             Value *LHS, Value *RHS) {
201  assert((Opcode == Instruction::ICmp || Opcode == Instruction::FCmp) &&
202         "Not a comparison!");
203  Expression e;
204  e.type = CmpInst::makeCmpResultType(LHS->getType());
205  e.varargs.push_back(lookup_or_add(LHS));
206  e.varargs.push_back(lookup_or_add(RHS));
207
208  // Sort the operand value numbers so x<y and y>x get the same value number.
209  if (e.varargs[0] > e.varargs[1]) {
210    std::swap(e.varargs[0], e.varargs[1]);
211    Predicate = CmpInst::getSwappedPredicate(Predicate);
212  }
213  e.opcode = (Opcode << 8) | Predicate;
214  return e;
215}
216
217Expression ValueTable::create_extractvalue_expression(ExtractValueInst *EI) {
218  assert(EI && "Not an ExtractValueInst?");
219  Expression e;
220  e.type = EI->getType();
221  e.opcode = 0;
222
223  IntrinsicInst *I = dyn_cast<IntrinsicInst>(EI->getAggregateOperand());
224  if (I != nullptr && EI->getNumIndices() == 1 && *EI->idx_begin() == 0 ) {
225    // EI might be an extract from one of our recognised intrinsics. If it
226    // is we'll synthesize a semantically equivalent expression instead on
227    // an extract value expression.
228    switch (I->getIntrinsicID()) {
229      case Intrinsic::sadd_with_overflow:
230      case Intrinsic::uadd_with_overflow:
231        e.opcode = Instruction::Add;
232        break;
233      case Intrinsic::ssub_with_overflow:
234      case Intrinsic::usub_with_overflow:
235        e.opcode = Instruction::Sub;
236        break;
237      case Intrinsic::smul_with_overflow:
238      case Intrinsic::umul_with_overflow:
239        e.opcode = Instruction::Mul;
240        break;
241      default:
242        break;
243    }
244
245    if (e.opcode != 0) {
246      // Intrinsic recognized. Grab its args to finish building the expression.
247      assert(I->getNumArgOperands() == 2 &&
248             "Expect two args for recognised intrinsics.");
249      e.varargs.push_back(lookup_or_add(I->getArgOperand(0)));
250      e.varargs.push_back(lookup_or_add(I->getArgOperand(1)));
251      return e;
252    }
253  }
254
255  // Not a recognised intrinsic. Fall back to producing an extract value
256  // expression.
257  e.opcode = EI->getOpcode();
258  for (Instruction::op_iterator OI = EI->op_begin(), OE = EI->op_end();
259       OI != OE; ++OI)
260    e.varargs.push_back(lookup_or_add(*OI));
261
262  for (ExtractValueInst::idx_iterator II = EI->idx_begin(), IE = EI->idx_end();
263         II != IE; ++II)
264    e.varargs.push_back(*II);
265
266  return e;
267}
268
269//===----------------------------------------------------------------------===//
270//                     ValueTable External Functions
271//===----------------------------------------------------------------------===//
272
273/// add - Insert a value into the table with a specified value number.
274void ValueTable::add(Value *V, uint32_t num) {
275  valueNumbering.insert(std::make_pair(V, num));
276}
277
278uint32_t ValueTable::lookup_or_add_call(CallInst *C) {
279  if (AA->doesNotAccessMemory(C)) {
280    Expression exp = create_expression(C);
281    uint32_t &e = expressionNumbering[exp];
282    if (!e) e = nextValueNumber++;
283    valueNumbering[C] = e;
284    return e;
285  } else if (AA->onlyReadsMemory(C)) {
286    Expression exp = create_expression(C);
287    uint32_t &e = expressionNumbering[exp];
288    if (!e) {
289      e = nextValueNumber++;
290      valueNumbering[C] = e;
291      return e;
292    }
293    if (!MD) {
294      e = nextValueNumber++;
295      valueNumbering[C] = e;
296      return e;
297    }
298
299    MemDepResult local_dep = MD->getDependency(C);
300
301    if (!local_dep.isDef() && !local_dep.isNonLocal()) {
302      valueNumbering[C] =  nextValueNumber;
303      return nextValueNumber++;
304    }
305
306    if (local_dep.isDef()) {
307      CallInst* local_cdep = cast<CallInst>(local_dep.getInst());
308
309      if (local_cdep->getNumArgOperands() != C->getNumArgOperands()) {
310        valueNumbering[C] = nextValueNumber;
311        return nextValueNumber++;
312      }
313
314      for (unsigned i = 0, e = C->getNumArgOperands(); i < e; ++i) {
315        uint32_t c_vn = lookup_or_add(C->getArgOperand(i));
316        uint32_t cd_vn = lookup_or_add(local_cdep->getArgOperand(i));
317        if (c_vn != cd_vn) {
318          valueNumbering[C] = nextValueNumber;
319          return nextValueNumber++;
320        }
321      }
322
323      uint32_t v = lookup_or_add(local_cdep);
324      valueNumbering[C] = v;
325      return v;
326    }
327
328    // Non-local case.
329    const MemoryDependenceAnalysis::NonLocalDepInfo &deps =
330      MD->getNonLocalCallDependency(CallSite(C));
331    // FIXME: Move the checking logic to MemDep!
332    CallInst* cdep = nullptr;
333
334    // Check to see if we have a single dominating call instruction that is
335    // identical to C.
336    for (unsigned i = 0, e = deps.size(); i != e; ++i) {
337      const NonLocalDepEntry *I = &deps[i];
338      if (I->getResult().isNonLocal())
339        continue;
340
341      // We don't handle non-definitions.  If we already have a call, reject
342      // instruction dependencies.
343      if (!I->getResult().isDef() || cdep != nullptr) {
344        cdep = nullptr;
345        break;
346      }
347
348      CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->getResult().getInst());
349      // FIXME: All duplicated with non-local case.
350      if (NonLocalDepCall && DT->properlyDominates(I->getBB(), C->getParent())){
351        cdep = NonLocalDepCall;
352        continue;
353      }
354
355      cdep = nullptr;
356      break;
357    }
358
359    if (!cdep) {
360      valueNumbering[C] = nextValueNumber;
361      return nextValueNumber++;
362    }
363
364    if (cdep->getNumArgOperands() != C->getNumArgOperands()) {
365      valueNumbering[C] = nextValueNumber;
366      return nextValueNumber++;
367    }
368    for (unsigned i = 0, e = C->getNumArgOperands(); i < e; ++i) {
369      uint32_t c_vn = lookup_or_add(C->getArgOperand(i));
370      uint32_t cd_vn = lookup_or_add(cdep->getArgOperand(i));
371      if (c_vn != cd_vn) {
372        valueNumbering[C] = nextValueNumber;
373        return nextValueNumber++;
374      }
375    }
376
377    uint32_t v = lookup_or_add(cdep);
378    valueNumbering[C] = v;
379    return v;
380
381  } else {
382    valueNumbering[C] = nextValueNumber;
383    return nextValueNumber++;
384  }
385}
386
387/// lookup_or_add - Returns the value number for the specified value, assigning
388/// it a new number if it did not have one before.
389uint32_t ValueTable::lookup_or_add(Value *V) {
390  DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
391  if (VI != valueNumbering.end())
392    return VI->second;
393
394  if (!isa<Instruction>(V)) {
395    valueNumbering[V] = nextValueNumber;
396    return nextValueNumber++;
397  }
398
399  Instruction* I = cast<Instruction>(V);
400  Expression exp;
401  switch (I->getOpcode()) {
402    case Instruction::Call:
403      return lookup_or_add_call(cast<CallInst>(I));
404    case Instruction::Add:
405    case Instruction::FAdd:
406    case Instruction::Sub:
407    case Instruction::FSub:
408    case Instruction::Mul:
409    case Instruction::FMul:
410    case Instruction::UDiv:
411    case Instruction::SDiv:
412    case Instruction::FDiv:
413    case Instruction::URem:
414    case Instruction::SRem:
415    case Instruction::FRem:
416    case Instruction::Shl:
417    case Instruction::LShr:
418    case Instruction::AShr:
419    case Instruction::And:
420    case Instruction::Or:
421    case Instruction::Xor:
422    case Instruction::ICmp:
423    case Instruction::FCmp:
424    case Instruction::Trunc:
425    case Instruction::ZExt:
426    case Instruction::SExt:
427    case Instruction::FPToUI:
428    case Instruction::FPToSI:
429    case Instruction::UIToFP:
430    case Instruction::SIToFP:
431    case Instruction::FPTrunc:
432    case Instruction::FPExt:
433    case Instruction::PtrToInt:
434    case Instruction::IntToPtr:
435    case Instruction::BitCast:
436    case Instruction::Select:
437    case Instruction::ExtractElement:
438    case Instruction::InsertElement:
439    case Instruction::ShuffleVector:
440    case Instruction::InsertValue:
441    case Instruction::GetElementPtr:
442      exp = create_expression(I);
443      break;
444    case Instruction::ExtractValue:
445      exp = create_extractvalue_expression(cast<ExtractValueInst>(I));
446      break;
447    default:
448      valueNumbering[V] = nextValueNumber;
449      return nextValueNumber++;
450  }
451
452  uint32_t& e = expressionNumbering[exp];
453  if (!e) e = nextValueNumber++;
454  valueNumbering[V] = e;
455  return e;
456}
457
458/// lookup - Returns the value number of the specified value. Fails if
459/// the value has not yet been numbered.
460uint32_t ValueTable::lookup(Value *V) const {
461  DenseMap<Value*, uint32_t>::const_iterator VI = valueNumbering.find(V);
462  assert(VI != valueNumbering.end() && "Value not numbered?");
463  return VI->second;
464}
465
466/// lookup_or_add_cmp - Returns the value number of the given comparison,
467/// assigning it a new number if it did not have one before.  Useful when
468/// we deduced the result of a comparison, but don't immediately have an
469/// instruction realizing that comparison to hand.
470uint32_t ValueTable::lookup_or_add_cmp(unsigned Opcode,
471                                       CmpInst::Predicate Predicate,
472                                       Value *LHS, Value *RHS) {
473  Expression exp = create_cmp_expression(Opcode, Predicate, LHS, RHS);
474  uint32_t& e = expressionNumbering[exp];
475  if (!e) e = nextValueNumber++;
476  return e;
477}
478
479/// clear - Remove all entries from the ValueTable.
480void ValueTable::clear() {
481  valueNumbering.clear();
482  expressionNumbering.clear();
483  nextValueNumber = 1;
484}
485
486/// erase - Remove a value from the value numbering.
487void ValueTable::erase(Value *V) {
488  valueNumbering.erase(V);
489}
490
491/// verifyRemoved - Verify that the value is removed from all internal data
492/// structures.
493void ValueTable::verifyRemoved(const Value *V) const {
494  for (DenseMap<Value*, uint32_t>::const_iterator
495         I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
496    assert(I->first != V && "Inst still occurs in value numbering map!");
497  }
498}
499
500//===----------------------------------------------------------------------===//
501//                                GVN Pass
502//===----------------------------------------------------------------------===//
503
504namespace {
505  class GVN;
506  struct AvailableValueInBlock {
507    /// BB - The basic block in question.
508    BasicBlock *BB;
509    enum ValType {
510      SimpleVal,  // A simple offsetted value that is accessed.
511      LoadVal,    // A value produced by a load.
512      MemIntrin,  // A memory intrinsic which is loaded from.
513      UndefVal    // A UndefValue representing a value from dead block (which
514                  // is not yet physically removed from the CFG).
515    };
516
517    /// V - The value that is live out of the block.
518    PointerIntPair<Value *, 2, ValType> Val;
519
520    /// Offset - The byte offset in Val that is interesting for the load query.
521    unsigned Offset;
522
523    static AvailableValueInBlock get(BasicBlock *BB, Value *V,
524                                     unsigned Offset = 0) {
525      AvailableValueInBlock Res;
526      Res.BB = BB;
527      Res.Val.setPointer(V);
528      Res.Val.setInt(SimpleVal);
529      Res.Offset = Offset;
530      return Res;
531    }
532
533    static AvailableValueInBlock getMI(BasicBlock *BB, MemIntrinsic *MI,
534                                       unsigned Offset = 0) {
535      AvailableValueInBlock Res;
536      Res.BB = BB;
537      Res.Val.setPointer(MI);
538      Res.Val.setInt(MemIntrin);
539      Res.Offset = Offset;
540      return Res;
541    }
542
543    static AvailableValueInBlock getLoad(BasicBlock *BB, LoadInst *LI,
544                                         unsigned Offset = 0) {
545      AvailableValueInBlock Res;
546      Res.BB = BB;
547      Res.Val.setPointer(LI);
548      Res.Val.setInt(LoadVal);
549      Res.Offset = Offset;
550      return Res;
551    }
552
553    static AvailableValueInBlock getUndef(BasicBlock *BB) {
554      AvailableValueInBlock Res;
555      Res.BB = BB;
556      Res.Val.setPointer(nullptr);
557      Res.Val.setInt(UndefVal);
558      Res.Offset = 0;
559      return Res;
560    }
561
562    bool isSimpleValue() const { return Val.getInt() == SimpleVal; }
563    bool isCoercedLoadValue() const { return Val.getInt() == LoadVal; }
564    bool isMemIntrinValue() const { return Val.getInt() == MemIntrin; }
565    bool isUndefValue() const { return Val.getInt() == UndefVal; }
566
567    Value *getSimpleValue() const {
568      assert(isSimpleValue() && "Wrong accessor");
569      return Val.getPointer();
570    }
571
572    LoadInst *getCoercedLoadValue() const {
573      assert(isCoercedLoadValue() && "Wrong accessor");
574      return cast<LoadInst>(Val.getPointer());
575    }
576
577    MemIntrinsic *getMemIntrinValue() const {
578      assert(isMemIntrinValue() && "Wrong accessor");
579      return cast<MemIntrinsic>(Val.getPointer());
580    }
581
582    /// MaterializeAdjustedValue - Emit code into this block to adjust the value
583    /// defined here to the specified type.  This handles various coercion cases.
584    Value *MaterializeAdjustedValue(Type *LoadTy, GVN &gvn) const;
585  };
586
587  class GVN : public FunctionPass {
588    bool NoLoads;
589    MemoryDependenceAnalysis *MD;
590    DominatorTree *DT;
591    const DataLayout *DL;
592    const TargetLibraryInfo *TLI;
593    SetVector<BasicBlock *> DeadBlocks;
594
595    ValueTable VN;
596
597    /// LeaderTable - A mapping from value numbers to lists of Value*'s that
598    /// have that value number.  Use findLeader to query it.
599    struct LeaderTableEntry {
600      Value *Val;
601      const BasicBlock *BB;
602      LeaderTableEntry *Next;
603    };
604    DenseMap<uint32_t, LeaderTableEntry> LeaderTable;
605    BumpPtrAllocator TableAllocator;
606
607    SmallVector<Instruction*, 8> InstrsToErase;
608
609    typedef SmallVector<NonLocalDepResult, 64> LoadDepVect;
610    typedef SmallVector<AvailableValueInBlock, 64> AvailValInBlkVect;
611    typedef SmallVector<BasicBlock*, 64> UnavailBlkVect;
612
613  public:
614    static char ID; // Pass identification, replacement for typeid
615    explicit GVN(bool noloads = false)
616        : FunctionPass(ID), NoLoads(noloads), MD(nullptr) {
617      initializeGVNPass(*PassRegistry::getPassRegistry());
618    }
619
620    bool runOnFunction(Function &F) override;
621
622    /// markInstructionForDeletion - This removes the specified instruction from
623    /// our various maps and marks it for deletion.
624    void markInstructionForDeletion(Instruction *I) {
625      VN.erase(I);
626      InstrsToErase.push_back(I);
627    }
628
629    const DataLayout *getDataLayout() const { return DL; }
630    DominatorTree &getDominatorTree() const { return *DT; }
631    AliasAnalysis *getAliasAnalysis() const { return VN.getAliasAnalysis(); }
632    MemoryDependenceAnalysis &getMemDep() const { return *MD; }
633  private:
634    /// addToLeaderTable - Push a new Value to the LeaderTable onto the list for
635    /// its value number.
636    void addToLeaderTable(uint32_t N, Value *V, const BasicBlock *BB) {
637      LeaderTableEntry &Curr = LeaderTable[N];
638      if (!Curr.Val) {
639        Curr.Val = V;
640        Curr.BB = BB;
641        return;
642      }
643
644      LeaderTableEntry *Node = TableAllocator.Allocate<LeaderTableEntry>();
645      Node->Val = V;
646      Node->BB = BB;
647      Node->Next = Curr.Next;
648      Curr.Next = Node;
649    }
650
651    /// removeFromLeaderTable - Scan the list of values corresponding to a given
652    /// value number, and remove the given instruction if encountered.
653    void removeFromLeaderTable(uint32_t N, Instruction *I, BasicBlock *BB) {
654      LeaderTableEntry* Prev = nullptr;
655      LeaderTableEntry* Curr = &LeaderTable[N];
656
657      while (Curr->Val != I || Curr->BB != BB) {
658        Prev = Curr;
659        Curr = Curr->Next;
660      }
661
662      if (Prev) {
663        Prev->Next = Curr->Next;
664      } else {
665        if (!Curr->Next) {
666          Curr->Val = nullptr;
667          Curr->BB = nullptr;
668        } else {
669          LeaderTableEntry* Next = Curr->Next;
670          Curr->Val = Next->Val;
671          Curr->BB = Next->BB;
672          Curr->Next = Next->Next;
673        }
674      }
675    }
676
677    // List of critical edges to be split between iterations.
678    SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit;
679
680    // This transformation requires dominator postdominator info
681    void getAnalysisUsage(AnalysisUsage &AU) const override {
682      AU.addRequired<DominatorTreeWrapperPass>();
683      AU.addRequired<TargetLibraryInfo>();
684      if (!NoLoads)
685        AU.addRequired<MemoryDependenceAnalysis>();
686      AU.addRequired<AliasAnalysis>();
687
688      AU.addPreserved<DominatorTreeWrapperPass>();
689      AU.addPreserved<AliasAnalysis>();
690    }
691
692
693    // Helper fuctions of redundant load elimination
694    bool processLoad(LoadInst *L);
695    bool processNonLocalLoad(LoadInst *L);
696    void AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
697                                 AvailValInBlkVect &ValuesPerBlock,
698                                 UnavailBlkVect &UnavailableBlocks);
699    bool PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
700                        UnavailBlkVect &UnavailableBlocks);
701
702    // Other helper routines
703    bool processInstruction(Instruction *I);
704    bool processBlock(BasicBlock *BB);
705    void dump(DenseMap<uint32_t, Value*> &d);
706    bool iterateOnFunction(Function &F);
707    bool performPRE(Function &F);
708    Value *findLeader(const BasicBlock *BB, uint32_t num);
709    void cleanupGlobalSets();
710    void verifyRemoved(const Instruction *I) const;
711    bool splitCriticalEdges();
712    BasicBlock *splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ);
713    unsigned replaceAllDominatedUsesWith(Value *From, Value *To,
714                                         const BasicBlockEdge &Root);
715    bool propagateEquality(Value *LHS, Value *RHS, const BasicBlockEdge &Root);
716    bool processFoldableCondBr(BranchInst *BI);
717    void addDeadBlock(BasicBlock *BB);
718    void assignValNumForDeadCode();
719  };
720
721  char GVN::ID = 0;
722}
723
724// createGVNPass - The public interface to this file...
725FunctionPass *llvm::createGVNPass(bool NoLoads) {
726  return new GVN(NoLoads);
727}
728
729INITIALIZE_PASS_BEGIN(GVN, "gvn", "Global Value Numbering", false, false)
730INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
731INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
732INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
733INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
734INITIALIZE_PASS_END(GVN, "gvn", "Global Value Numbering", false, false)
735
736#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
737void GVN::dump(DenseMap<uint32_t, Value*>& d) {
738  errs() << "{\n";
739  for (DenseMap<uint32_t, Value*>::iterator I = d.begin(),
740       E = d.end(); I != E; ++I) {
741      errs() << I->first << "\n";
742      I->second->dump();
743  }
744  errs() << "}\n";
745}
746#endif
747
748/// IsValueFullyAvailableInBlock - Return true if we can prove that the value
749/// we're analyzing is fully available in the specified block.  As we go, keep
750/// track of which blocks we know are fully alive in FullyAvailableBlocks.  This
751/// map is actually a tri-state map with the following values:
752///   0) we know the block *is not* fully available.
753///   1) we know the block *is* fully available.
754///   2) we do not know whether the block is fully available or not, but we are
755///      currently speculating that it will be.
756///   3) we are speculating for this block and have used that to speculate for
757///      other blocks.
758static bool IsValueFullyAvailableInBlock(BasicBlock *BB,
759                            DenseMap<BasicBlock*, char> &FullyAvailableBlocks,
760                            uint32_t RecurseDepth) {
761  if (RecurseDepth > MaxRecurseDepth)
762    return false;
763
764  // Optimistically assume that the block is fully available and check to see
765  // if we already know about this block in one lookup.
766  std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV =
767    FullyAvailableBlocks.insert(std::make_pair(BB, 2));
768
769  // If the entry already existed for this block, return the precomputed value.
770  if (!IV.second) {
771    // If this is a speculative "available" value, mark it as being used for
772    // speculation of other blocks.
773    if (IV.first->second == 2)
774      IV.first->second = 3;
775    return IV.first->second != 0;
776  }
777
778  // Otherwise, see if it is fully available in all predecessors.
779  pred_iterator PI = pred_begin(BB), PE = pred_end(BB);
780
781  // If this block has no predecessors, it isn't live-in here.
782  if (PI == PE)
783    goto SpeculationFailure;
784
785  for (; PI != PE; ++PI)
786    // If the value isn't fully available in one of our predecessors, then it
787    // isn't fully available in this block either.  Undo our previous
788    // optimistic assumption and bail out.
789    if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks,RecurseDepth+1))
790      goto SpeculationFailure;
791
792  return true;
793
794// SpeculationFailure - If we get here, we found out that this is not, after
795// all, a fully-available block.  We have a problem if we speculated on this and
796// used the speculation to mark other blocks as available.
797SpeculationFailure:
798  char &BBVal = FullyAvailableBlocks[BB];
799
800  // If we didn't speculate on this, just return with it set to false.
801  if (BBVal == 2) {
802    BBVal = 0;
803    return false;
804  }
805
806  // If we did speculate on this value, we could have blocks set to 1 that are
807  // incorrect.  Walk the (transitive) successors of this block and mark them as
808  // 0 if set to one.
809  SmallVector<BasicBlock*, 32> BBWorklist;
810  BBWorklist.push_back(BB);
811
812  do {
813    BasicBlock *Entry = BBWorklist.pop_back_val();
814    // Note that this sets blocks to 0 (unavailable) if they happen to not
815    // already be in FullyAvailableBlocks.  This is safe.
816    char &EntryVal = FullyAvailableBlocks[Entry];
817    if (EntryVal == 0) continue;  // Already unavailable.
818
819    // Mark as unavailable.
820    EntryVal = 0;
821
822    BBWorklist.append(succ_begin(Entry), succ_end(Entry));
823  } while (!BBWorklist.empty());
824
825  return false;
826}
827
828
829/// CanCoerceMustAliasedValueToLoad - Return true if
830/// CoerceAvailableValueToLoadType will succeed.
831static bool CanCoerceMustAliasedValueToLoad(Value *StoredVal,
832                                            Type *LoadTy,
833                                            const DataLayout &DL) {
834  // If the loaded or stored value is an first class array or struct, don't try
835  // to transform them.  We need to be able to bitcast to integer.
836  if (LoadTy->isStructTy() || LoadTy->isArrayTy() ||
837      StoredVal->getType()->isStructTy() ||
838      StoredVal->getType()->isArrayTy())
839    return false;
840
841  // The store has to be at least as big as the load.
842  if (DL.getTypeSizeInBits(StoredVal->getType()) <
843        DL.getTypeSizeInBits(LoadTy))
844    return false;
845
846  return true;
847}
848
849/// CoerceAvailableValueToLoadType - If we saw a store of a value to memory, and
850/// then a load from a must-aliased pointer of a different type, try to coerce
851/// the stored value.  LoadedTy is the type of the load we want to replace and
852/// InsertPt is the place to insert new instructions.
853///
854/// If we can't do it, return null.
855static Value *CoerceAvailableValueToLoadType(Value *StoredVal,
856                                             Type *LoadedTy,
857                                             Instruction *InsertPt,
858                                             const DataLayout &DL) {
859  if (!CanCoerceMustAliasedValueToLoad(StoredVal, LoadedTy, DL))
860    return nullptr;
861
862  // If this is already the right type, just return it.
863  Type *StoredValTy = StoredVal->getType();
864
865  uint64_t StoreSize = DL.getTypeSizeInBits(StoredValTy);
866  uint64_t LoadSize = DL.getTypeSizeInBits(LoadedTy);
867
868  // If the store and reload are the same size, we can always reuse it.
869  if (StoreSize == LoadSize) {
870    // Pointer to Pointer -> use bitcast.
871    if (StoredValTy->getScalarType()->isPointerTy() &&
872        LoadedTy->getScalarType()->isPointerTy())
873      return new BitCastInst(StoredVal, LoadedTy, "", InsertPt);
874
875    // Convert source pointers to integers, which can be bitcast.
876    if (StoredValTy->getScalarType()->isPointerTy()) {
877      StoredValTy = DL.getIntPtrType(StoredValTy);
878      StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
879    }
880
881    Type *TypeToCastTo = LoadedTy;
882    if (TypeToCastTo->getScalarType()->isPointerTy())
883      TypeToCastTo = DL.getIntPtrType(TypeToCastTo);
884
885    if (StoredValTy != TypeToCastTo)
886      StoredVal = new BitCastInst(StoredVal, TypeToCastTo, "", InsertPt);
887
888    // Cast to pointer if the load needs a pointer type.
889    if (LoadedTy->getScalarType()->isPointerTy())
890      StoredVal = new IntToPtrInst(StoredVal, LoadedTy, "", InsertPt);
891
892    return StoredVal;
893  }
894
895  // If the loaded value is smaller than the available value, then we can
896  // extract out a piece from it.  If the available value is too small, then we
897  // can't do anything.
898  assert(StoreSize >= LoadSize && "CanCoerceMustAliasedValueToLoad fail");
899
900  // Convert source pointers to integers, which can be manipulated.
901  if (StoredValTy->getScalarType()->isPointerTy()) {
902    StoredValTy = DL.getIntPtrType(StoredValTy);
903    StoredVal = new PtrToIntInst(StoredVal, StoredValTy, "", InsertPt);
904  }
905
906  // Convert vectors and fp to integer, which can be manipulated.
907  if (!StoredValTy->isIntegerTy()) {
908    StoredValTy = IntegerType::get(StoredValTy->getContext(), StoreSize);
909    StoredVal = new BitCastInst(StoredVal, StoredValTy, "", InsertPt);
910  }
911
912  // If this is a big-endian system, we need to shift the value down to the low
913  // bits so that a truncate will work.
914  if (DL.isBigEndian()) {
915    Constant *Val = ConstantInt::get(StoredVal->getType(), StoreSize-LoadSize);
916    StoredVal = BinaryOperator::CreateLShr(StoredVal, Val, "tmp", InsertPt);
917  }
918
919  // Truncate the integer to the right size now.
920  Type *NewIntTy = IntegerType::get(StoredValTy->getContext(), LoadSize);
921  StoredVal = new TruncInst(StoredVal, NewIntTy, "trunc", InsertPt);
922
923  if (LoadedTy == NewIntTy)
924    return StoredVal;
925
926  // If the result is a pointer, inttoptr.
927  if (LoadedTy->getScalarType()->isPointerTy())
928    return new IntToPtrInst(StoredVal, LoadedTy, "inttoptr", InsertPt);
929
930  // Otherwise, bitcast.
931  return new BitCastInst(StoredVal, LoadedTy, "bitcast", InsertPt);
932}
933
934/// AnalyzeLoadFromClobberingWrite - This function is called when we have a
935/// memdep query of a load that ends up being a clobbering memory write (store,
936/// memset, memcpy, memmove).  This means that the write *may* provide bits used
937/// by the load but we can't be sure because the pointers don't mustalias.
938///
939/// Check this case to see if there is anything more we can do before we give
940/// up.  This returns -1 if we have to give up, or a byte number in the stored
941/// value of the piece that feeds the load.
942static int AnalyzeLoadFromClobberingWrite(Type *LoadTy, Value *LoadPtr,
943                                          Value *WritePtr,
944                                          uint64_t WriteSizeInBits,
945                                          const DataLayout &DL) {
946  // If the loaded or stored value is a first class array or struct, don't try
947  // to transform them.  We need to be able to bitcast to integer.
948  if (LoadTy->isStructTy() || LoadTy->isArrayTy())
949    return -1;
950
951  int64_t StoreOffset = 0, LoadOffset = 0;
952  Value *StoreBase = GetPointerBaseWithConstantOffset(WritePtr,StoreOffset,&DL);
953  Value *LoadBase = GetPointerBaseWithConstantOffset(LoadPtr, LoadOffset, &DL);
954  if (StoreBase != LoadBase)
955    return -1;
956
957  // If the load and store are to the exact same address, they should have been
958  // a must alias.  AA must have gotten confused.
959  // FIXME: Study to see if/when this happens.  One case is forwarding a memset
960  // to a load from the base of the memset.
961#if 0
962  if (LoadOffset == StoreOffset) {
963    dbgs() << "STORE/LOAD DEP WITH COMMON POINTER MISSED:\n"
964    << "Base       = " << *StoreBase << "\n"
965    << "Store Ptr  = " << *WritePtr << "\n"
966    << "Store Offs = " << StoreOffset << "\n"
967    << "Load Ptr   = " << *LoadPtr << "\n";
968    abort();
969  }
970#endif
971
972  // If the load and store don't overlap at all, the store doesn't provide
973  // anything to the load.  In this case, they really don't alias at all, AA
974  // must have gotten confused.
975  uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy);
976
977  if ((WriteSizeInBits & 7) | (LoadSize & 7))
978    return -1;
979  uint64_t StoreSize = WriteSizeInBits >> 3;  // Convert to bytes.
980  LoadSize >>= 3;
981
982
983  bool isAAFailure = false;
984  if (StoreOffset < LoadOffset)
985    isAAFailure = StoreOffset+int64_t(StoreSize) <= LoadOffset;
986  else
987    isAAFailure = LoadOffset+int64_t(LoadSize) <= StoreOffset;
988
989  if (isAAFailure) {
990#if 0
991    dbgs() << "STORE LOAD DEP WITH COMMON BASE:\n"
992    << "Base       = " << *StoreBase << "\n"
993    << "Store Ptr  = " << *WritePtr << "\n"
994    << "Store Offs = " << StoreOffset << "\n"
995    << "Load Ptr   = " << *LoadPtr << "\n";
996    abort();
997#endif
998    return -1;
999  }
1000
1001  // If the Load isn't completely contained within the stored bits, we don't
1002  // have all the bits to feed it.  We could do something crazy in the future
1003  // (issue a smaller load then merge the bits in) but this seems unlikely to be
1004  // valuable.
1005  if (StoreOffset > LoadOffset ||
1006      StoreOffset+StoreSize < LoadOffset+LoadSize)
1007    return -1;
1008
1009  // Okay, we can do this transformation.  Return the number of bytes into the
1010  // store that the load is.
1011  return LoadOffset-StoreOffset;
1012}
1013
1014/// AnalyzeLoadFromClobberingStore - This function is called when we have a
1015/// memdep query of a load that ends up being a clobbering store.
1016static int AnalyzeLoadFromClobberingStore(Type *LoadTy, Value *LoadPtr,
1017                                          StoreInst *DepSI,
1018                                          const DataLayout &DL) {
1019  // Cannot handle reading from store of first-class aggregate yet.
1020  if (DepSI->getValueOperand()->getType()->isStructTy() ||
1021      DepSI->getValueOperand()->getType()->isArrayTy())
1022    return -1;
1023
1024  Value *StorePtr = DepSI->getPointerOperand();
1025  uint64_t StoreSize =DL.getTypeSizeInBits(DepSI->getValueOperand()->getType());
1026  return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
1027                                        StorePtr, StoreSize, DL);
1028}
1029
1030/// AnalyzeLoadFromClobberingLoad - This function is called when we have a
1031/// memdep query of a load that ends up being clobbered by another load.  See if
1032/// the other load can feed into the second load.
1033static int AnalyzeLoadFromClobberingLoad(Type *LoadTy, Value *LoadPtr,
1034                                         LoadInst *DepLI, const DataLayout &DL){
1035  // Cannot handle reading from store of first-class aggregate yet.
1036  if (DepLI->getType()->isStructTy() || DepLI->getType()->isArrayTy())
1037    return -1;
1038
1039  Value *DepPtr = DepLI->getPointerOperand();
1040  uint64_t DepSize = DL.getTypeSizeInBits(DepLI->getType());
1041  int R = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, DepSize, DL);
1042  if (R != -1) return R;
1043
1044  // If we have a load/load clobber an DepLI can be widened to cover this load,
1045  // then we should widen it!
1046  int64_t LoadOffs = 0;
1047  const Value *LoadBase =
1048    GetPointerBaseWithConstantOffset(LoadPtr, LoadOffs, &DL);
1049  unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
1050
1051  unsigned Size = MemoryDependenceAnalysis::
1052    getLoadLoadClobberFullWidthSize(LoadBase, LoadOffs, LoadSize, DepLI, DL);
1053  if (Size == 0) return -1;
1054
1055  return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, DepPtr, Size*8, DL);
1056}
1057
1058
1059
1060static int AnalyzeLoadFromClobberingMemInst(Type *LoadTy, Value *LoadPtr,
1061                                            MemIntrinsic *MI,
1062                                            const DataLayout &DL) {
1063  // If the mem operation is a non-constant size, we can't handle it.
1064  ConstantInt *SizeCst = dyn_cast<ConstantInt>(MI->getLength());
1065  if (!SizeCst) return -1;
1066  uint64_t MemSizeInBits = SizeCst->getZExtValue()*8;
1067
1068  // If this is memset, we just need to see if the offset is valid in the size
1069  // of the memset..
1070  if (MI->getIntrinsicID() == Intrinsic::memset)
1071    return AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr, MI->getDest(),
1072                                          MemSizeInBits, DL);
1073
1074  // If we have a memcpy/memmove, the only case we can handle is if this is a
1075  // copy from constant memory.  In that case, we can read directly from the
1076  // constant memory.
1077  MemTransferInst *MTI = cast<MemTransferInst>(MI);
1078
1079  Constant *Src = dyn_cast<Constant>(MTI->getSource());
1080  if (!Src) return -1;
1081
1082  GlobalVariable *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(Src, &DL));
1083  if (!GV || !GV->isConstant()) return -1;
1084
1085  // See if the access is within the bounds of the transfer.
1086  int Offset = AnalyzeLoadFromClobberingWrite(LoadTy, LoadPtr,
1087                                              MI->getDest(), MemSizeInBits, DL);
1088  if (Offset == -1)
1089    return Offset;
1090
1091  unsigned AS = Src->getType()->getPointerAddressSpace();
1092  // Otherwise, see if we can constant fold a load from the constant with the
1093  // offset applied as appropriate.
1094  Src = ConstantExpr::getBitCast(Src,
1095                                 Type::getInt8PtrTy(Src->getContext(), AS));
1096  Constant *OffsetCst =
1097    ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
1098  Src = ConstantExpr::getGetElementPtr(Src, OffsetCst);
1099  Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
1100  if (ConstantFoldLoadFromConstPtr(Src, &DL))
1101    return Offset;
1102  return -1;
1103}
1104
1105
1106/// GetStoreValueForLoad - This function is called when we have a
1107/// memdep query of a load that ends up being a clobbering store.  This means
1108/// that the store provides bits used by the load but we the pointers don't
1109/// mustalias.  Check this case to see if there is anything more we can do
1110/// before we give up.
1111static Value *GetStoreValueForLoad(Value *SrcVal, unsigned Offset,
1112                                   Type *LoadTy,
1113                                   Instruction *InsertPt, const DataLayout &DL){
1114  LLVMContext &Ctx = SrcVal->getType()->getContext();
1115
1116  uint64_t StoreSize = (DL.getTypeSizeInBits(SrcVal->getType()) + 7) / 8;
1117  uint64_t LoadSize = (DL.getTypeSizeInBits(LoadTy) + 7) / 8;
1118
1119  IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
1120
1121  // Compute which bits of the stored value are being used by the load.  Convert
1122  // to an integer type to start with.
1123  if (SrcVal->getType()->getScalarType()->isPointerTy())
1124    SrcVal = Builder.CreatePtrToInt(SrcVal,
1125        DL.getIntPtrType(SrcVal->getType()));
1126  if (!SrcVal->getType()->isIntegerTy())
1127    SrcVal = Builder.CreateBitCast(SrcVal, IntegerType::get(Ctx, StoreSize*8));
1128
1129  // Shift the bits to the least significant depending on endianness.
1130  unsigned ShiftAmt;
1131  if (DL.isLittleEndian())
1132    ShiftAmt = Offset*8;
1133  else
1134    ShiftAmt = (StoreSize-LoadSize-Offset)*8;
1135
1136  if (ShiftAmt)
1137    SrcVal = Builder.CreateLShr(SrcVal, ShiftAmt);
1138
1139  if (LoadSize != StoreSize)
1140    SrcVal = Builder.CreateTrunc(SrcVal, IntegerType::get(Ctx, LoadSize*8));
1141
1142  return CoerceAvailableValueToLoadType(SrcVal, LoadTy, InsertPt, DL);
1143}
1144
1145/// GetLoadValueForLoad - This function is called when we have a
1146/// memdep query of a load that ends up being a clobbering load.  This means
1147/// that the load *may* provide bits used by the load but we can't be sure
1148/// because the pointers don't mustalias.  Check this case to see if there is
1149/// anything more we can do before we give up.
1150static Value *GetLoadValueForLoad(LoadInst *SrcVal, unsigned Offset,
1151                                  Type *LoadTy, Instruction *InsertPt,
1152                                  GVN &gvn) {
1153  const DataLayout &DL = *gvn.getDataLayout();
1154  // If Offset+LoadTy exceeds the size of SrcVal, then we must be wanting to
1155  // widen SrcVal out to a larger load.
1156  unsigned SrcValSize = DL.getTypeStoreSize(SrcVal->getType());
1157  unsigned LoadSize = DL.getTypeStoreSize(LoadTy);
1158  if (Offset+LoadSize > SrcValSize) {
1159    assert(SrcVal->isSimple() && "Cannot widen volatile/atomic load!");
1160    assert(SrcVal->getType()->isIntegerTy() && "Can't widen non-integer load");
1161    // If we have a load/load clobber an DepLI can be widened to cover this
1162    // load, then we should widen it to the next power of 2 size big enough!
1163    unsigned NewLoadSize = Offset+LoadSize;
1164    if (!isPowerOf2_32(NewLoadSize))
1165      NewLoadSize = NextPowerOf2(NewLoadSize);
1166
1167    Value *PtrVal = SrcVal->getPointerOperand();
1168
1169    // Insert the new load after the old load.  This ensures that subsequent
1170    // memdep queries will find the new load.  We can't easily remove the old
1171    // load completely because it is already in the value numbering table.
1172    IRBuilder<> Builder(SrcVal->getParent(), ++BasicBlock::iterator(SrcVal));
1173    Type *DestPTy =
1174      IntegerType::get(LoadTy->getContext(), NewLoadSize*8);
1175    DestPTy = PointerType::get(DestPTy,
1176                               PtrVal->getType()->getPointerAddressSpace());
1177    Builder.SetCurrentDebugLocation(SrcVal->getDebugLoc());
1178    PtrVal = Builder.CreateBitCast(PtrVal, DestPTy);
1179    LoadInst *NewLoad = Builder.CreateLoad(PtrVal);
1180    NewLoad->takeName(SrcVal);
1181    NewLoad->setAlignment(SrcVal->getAlignment());
1182
1183    DEBUG(dbgs() << "GVN WIDENED LOAD: " << *SrcVal << "\n");
1184    DEBUG(dbgs() << "TO: " << *NewLoad << "\n");
1185
1186    // Replace uses of the original load with the wider load.  On a big endian
1187    // system, we need to shift down to get the relevant bits.
1188    Value *RV = NewLoad;
1189    if (DL.isBigEndian())
1190      RV = Builder.CreateLShr(RV,
1191                    NewLoadSize*8-SrcVal->getType()->getPrimitiveSizeInBits());
1192    RV = Builder.CreateTrunc(RV, SrcVal->getType());
1193    SrcVal->replaceAllUsesWith(RV);
1194
1195    // We would like to use gvn.markInstructionForDeletion here, but we can't
1196    // because the load is already memoized into the leader map table that GVN
1197    // tracks.  It is potentially possible to remove the load from the table,
1198    // but then there all of the operations based on it would need to be
1199    // rehashed.  Just leave the dead load around.
1200    gvn.getMemDep().removeInstruction(SrcVal);
1201    SrcVal = NewLoad;
1202  }
1203
1204  return GetStoreValueForLoad(SrcVal, Offset, LoadTy, InsertPt, DL);
1205}
1206
1207
1208/// GetMemInstValueForLoad - This function is called when we have a
1209/// memdep query of a load that ends up being a clobbering mem intrinsic.
1210static Value *GetMemInstValueForLoad(MemIntrinsic *SrcInst, unsigned Offset,
1211                                     Type *LoadTy, Instruction *InsertPt,
1212                                     const DataLayout &DL){
1213  LLVMContext &Ctx = LoadTy->getContext();
1214  uint64_t LoadSize = DL.getTypeSizeInBits(LoadTy)/8;
1215
1216  IRBuilder<> Builder(InsertPt->getParent(), InsertPt);
1217
1218  // We know that this method is only called when the mem transfer fully
1219  // provides the bits for the load.
1220  if (MemSetInst *MSI = dyn_cast<MemSetInst>(SrcInst)) {
1221    // memset(P, 'x', 1234) -> splat('x'), even if x is a variable, and
1222    // independently of what the offset is.
1223    Value *Val = MSI->getValue();
1224    if (LoadSize != 1)
1225      Val = Builder.CreateZExt(Val, IntegerType::get(Ctx, LoadSize*8));
1226
1227    Value *OneElt = Val;
1228
1229    // Splat the value out to the right number of bits.
1230    for (unsigned NumBytesSet = 1; NumBytesSet != LoadSize; ) {
1231      // If we can double the number of bytes set, do it.
1232      if (NumBytesSet*2 <= LoadSize) {
1233        Value *ShVal = Builder.CreateShl(Val, NumBytesSet*8);
1234        Val = Builder.CreateOr(Val, ShVal);
1235        NumBytesSet <<= 1;
1236        continue;
1237      }
1238
1239      // Otherwise insert one byte at a time.
1240      Value *ShVal = Builder.CreateShl(Val, 1*8);
1241      Val = Builder.CreateOr(OneElt, ShVal);
1242      ++NumBytesSet;
1243    }
1244
1245    return CoerceAvailableValueToLoadType(Val, LoadTy, InsertPt, DL);
1246  }
1247
1248  // Otherwise, this is a memcpy/memmove from a constant global.
1249  MemTransferInst *MTI = cast<MemTransferInst>(SrcInst);
1250  Constant *Src = cast<Constant>(MTI->getSource());
1251  unsigned AS = Src->getType()->getPointerAddressSpace();
1252
1253  // Otherwise, see if we can constant fold a load from the constant with the
1254  // offset applied as appropriate.
1255  Src = ConstantExpr::getBitCast(Src,
1256                                 Type::getInt8PtrTy(Src->getContext(), AS));
1257  Constant *OffsetCst =
1258    ConstantInt::get(Type::getInt64Ty(Src->getContext()), (unsigned)Offset);
1259  Src = ConstantExpr::getGetElementPtr(Src, OffsetCst);
1260  Src = ConstantExpr::getBitCast(Src, PointerType::get(LoadTy, AS));
1261  return ConstantFoldLoadFromConstPtr(Src, &DL);
1262}
1263
1264
1265/// ConstructSSAForLoadSet - Given a set of loads specified by ValuesPerBlock,
1266/// construct SSA form, allowing us to eliminate LI.  This returns the value
1267/// that should be used at LI's definition site.
1268static Value *ConstructSSAForLoadSet(LoadInst *LI,
1269                         SmallVectorImpl<AvailableValueInBlock> &ValuesPerBlock,
1270                                     GVN &gvn) {
1271  // Check for the fully redundant, dominating load case.  In this case, we can
1272  // just use the dominating value directly.
1273  if (ValuesPerBlock.size() == 1 &&
1274      gvn.getDominatorTree().properlyDominates(ValuesPerBlock[0].BB,
1275                                               LI->getParent())) {
1276    assert(!ValuesPerBlock[0].isUndefValue() && "Dead BB dominate this block");
1277    return ValuesPerBlock[0].MaterializeAdjustedValue(LI->getType(), gvn);
1278  }
1279
1280  // Otherwise, we have to construct SSA form.
1281  SmallVector<PHINode*, 8> NewPHIs;
1282  SSAUpdater SSAUpdate(&NewPHIs);
1283  SSAUpdate.Initialize(LI->getType(), LI->getName());
1284
1285  Type *LoadTy = LI->getType();
1286
1287  for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) {
1288    const AvailableValueInBlock &AV = ValuesPerBlock[i];
1289    BasicBlock *BB = AV.BB;
1290
1291    if (SSAUpdate.HasValueForBlock(BB))
1292      continue;
1293
1294    SSAUpdate.AddAvailableValue(BB, AV.MaterializeAdjustedValue(LoadTy, gvn));
1295  }
1296
1297  // Perform PHI construction.
1298  Value *V = SSAUpdate.GetValueInMiddleOfBlock(LI->getParent());
1299
1300  // If new PHI nodes were created, notify alias analysis.
1301  if (V->getType()->getScalarType()->isPointerTy()) {
1302    AliasAnalysis *AA = gvn.getAliasAnalysis();
1303
1304    for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
1305      AA->copyValue(LI, NewPHIs[i]);
1306
1307    // Now that we've copied information to the new PHIs, scan through
1308    // them again and inform alias analysis that we've added potentially
1309    // escaping uses to any values that are operands to these PHIs.
1310    for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i) {
1311      PHINode *P = NewPHIs[i];
1312      for (unsigned ii = 0, ee = P->getNumIncomingValues(); ii != ee; ++ii) {
1313        unsigned jj = PHINode::getOperandNumForIncomingValue(ii);
1314        AA->addEscapingUse(P->getOperandUse(jj));
1315      }
1316    }
1317  }
1318
1319  return V;
1320}
1321
1322Value *AvailableValueInBlock::MaterializeAdjustedValue(Type *LoadTy, GVN &gvn) const {
1323  Value *Res;
1324  if (isSimpleValue()) {
1325    Res = getSimpleValue();
1326    if (Res->getType() != LoadTy) {
1327      const DataLayout *DL = gvn.getDataLayout();
1328      assert(DL && "Need target data to handle type mismatch case");
1329      Res = GetStoreValueForLoad(Res, Offset, LoadTy, BB->getTerminator(),
1330                                 *DL);
1331
1332      DEBUG(dbgs() << "GVN COERCED NONLOCAL VAL:\nOffset: " << Offset << "  "
1333                   << *getSimpleValue() << '\n'
1334                   << *Res << '\n' << "\n\n\n");
1335    }
1336  } else if (isCoercedLoadValue()) {
1337    LoadInst *Load = getCoercedLoadValue();
1338    if (Load->getType() == LoadTy && Offset == 0) {
1339      Res = Load;
1340    } else {
1341      Res = GetLoadValueForLoad(Load, Offset, LoadTy, BB->getTerminator(),
1342                                gvn);
1343
1344      DEBUG(dbgs() << "GVN COERCED NONLOCAL LOAD:\nOffset: " << Offset << "  "
1345                   << *getCoercedLoadValue() << '\n'
1346                   << *Res << '\n' << "\n\n\n");
1347    }
1348  } else if (isMemIntrinValue()) {
1349    const DataLayout *DL = gvn.getDataLayout();
1350    assert(DL && "Need target data to handle type mismatch case");
1351    Res = GetMemInstValueForLoad(getMemIntrinValue(), Offset,
1352                                 LoadTy, BB->getTerminator(), *DL);
1353    DEBUG(dbgs() << "GVN COERCED NONLOCAL MEM INTRIN:\nOffset: " << Offset
1354                 << "  " << *getMemIntrinValue() << '\n'
1355                 << *Res << '\n' << "\n\n\n");
1356  } else {
1357    assert(isUndefValue() && "Should be UndefVal");
1358    DEBUG(dbgs() << "GVN COERCED NONLOCAL Undef:\n";);
1359    return UndefValue::get(LoadTy);
1360  }
1361  return Res;
1362}
1363
1364static bool isLifetimeStart(const Instruction *Inst) {
1365  if (const IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst))
1366    return II->getIntrinsicID() == Intrinsic::lifetime_start;
1367  return false;
1368}
1369
1370void GVN::AnalyzeLoadAvailability(LoadInst *LI, LoadDepVect &Deps,
1371                                  AvailValInBlkVect &ValuesPerBlock,
1372                                  UnavailBlkVect &UnavailableBlocks) {
1373
1374  // Filter out useless results (non-locals, etc).  Keep track of the blocks
1375  // where we have a value available in repl, also keep track of whether we see
1376  // dependencies that produce an unknown value for the load (such as a call
1377  // that could potentially clobber the load).
1378  unsigned NumDeps = Deps.size();
1379  for (unsigned i = 0, e = NumDeps; i != e; ++i) {
1380    BasicBlock *DepBB = Deps[i].getBB();
1381    MemDepResult DepInfo = Deps[i].getResult();
1382
1383    if (DeadBlocks.count(DepBB)) {
1384      // Dead dependent mem-op disguise as a load evaluating the same value
1385      // as the load in question.
1386      ValuesPerBlock.push_back(AvailableValueInBlock::getUndef(DepBB));
1387      continue;
1388    }
1389
1390    if (!DepInfo.isDef() && !DepInfo.isClobber()) {
1391      UnavailableBlocks.push_back(DepBB);
1392      continue;
1393    }
1394
1395    if (DepInfo.isClobber()) {
1396      // The address being loaded in this non-local block may not be the same as
1397      // the pointer operand of the load if PHI translation occurs.  Make sure
1398      // to consider the right address.
1399      Value *Address = Deps[i].getAddress();
1400
1401      // If the dependence is to a store that writes to a superset of the bits
1402      // read by the load, we can extract the bits we need for the load from the
1403      // stored value.
1404      if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInfo.getInst())) {
1405        if (DL && Address) {
1406          int Offset = AnalyzeLoadFromClobberingStore(LI->getType(), Address,
1407                                                      DepSI, *DL);
1408          if (Offset != -1) {
1409            ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1410                                                       DepSI->getValueOperand(),
1411                                                                Offset));
1412            continue;
1413          }
1414        }
1415      }
1416
1417      // Check to see if we have something like this:
1418      //    load i32* P
1419      //    load i8* (P+1)
1420      // if we have this, replace the later with an extraction from the former.
1421      if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInfo.getInst())) {
1422        // If this is a clobber and L is the first instruction in its block, then
1423        // we have the first instruction in the entry block.
1424        if (DepLI != LI && Address && DL) {
1425          int Offset = AnalyzeLoadFromClobberingLoad(LI->getType(), Address,
1426                                                     DepLI, *DL);
1427
1428          if (Offset != -1) {
1429            ValuesPerBlock.push_back(AvailableValueInBlock::getLoad(DepBB,DepLI,
1430                                                                    Offset));
1431            continue;
1432          }
1433        }
1434      }
1435
1436      // If the clobbering value is a memset/memcpy/memmove, see if we can
1437      // forward a value on from it.
1438      if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(DepInfo.getInst())) {
1439        if (DL && Address) {
1440          int Offset = AnalyzeLoadFromClobberingMemInst(LI->getType(), Address,
1441                                                        DepMI, *DL);
1442          if (Offset != -1) {
1443            ValuesPerBlock.push_back(AvailableValueInBlock::getMI(DepBB, DepMI,
1444                                                                  Offset));
1445            continue;
1446          }
1447        }
1448      }
1449
1450      UnavailableBlocks.push_back(DepBB);
1451      continue;
1452    }
1453
1454    // DepInfo.isDef() here
1455
1456    Instruction *DepInst = DepInfo.getInst();
1457
1458    // Loading the allocation -> undef.
1459    if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI) ||
1460        // Loading immediately after lifetime begin -> undef.
1461        isLifetimeStart(DepInst)) {
1462      ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1463                                             UndefValue::get(LI->getType())));
1464      continue;
1465    }
1466
1467    // Loading from calloc (which zero initializes memory) -> zero
1468    if (isCallocLikeFn(DepInst, TLI)) {
1469      ValuesPerBlock.push_back(AvailableValueInBlock::get(
1470          DepBB, Constant::getNullValue(LI->getType())));
1471      continue;
1472    }
1473
1474    if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
1475      // Reject loads and stores that are to the same address but are of
1476      // different types if we have to.
1477      if (S->getValueOperand()->getType() != LI->getType()) {
1478        // If the stored value is larger or equal to the loaded value, we can
1479        // reuse it.
1480        if (!DL || !CanCoerceMustAliasedValueToLoad(S->getValueOperand(),
1481                                                    LI->getType(), *DL)) {
1482          UnavailableBlocks.push_back(DepBB);
1483          continue;
1484        }
1485      }
1486
1487      ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
1488                                                         S->getValueOperand()));
1489      continue;
1490    }
1491
1492    if (LoadInst *LD = dyn_cast<LoadInst>(DepInst)) {
1493      // If the types mismatch and we can't handle it, reject reuse of the load.
1494      if (LD->getType() != LI->getType()) {
1495        // If the stored value is larger or equal to the loaded value, we can
1496        // reuse it.
1497        if (!DL || !CanCoerceMustAliasedValueToLoad(LD, LI->getType(),*DL)) {
1498          UnavailableBlocks.push_back(DepBB);
1499          continue;
1500        }
1501      }
1502      ValuesPerBlock.push_back(AvailableValueInBlock::getLoad(DepBB, LD));
1503      continue;
1504    }
1505
1506    UnavailableBlocks.push_back(DepBB);
1507  }
1508}
1509
1510bool GVN::PerformLoadPRE(LoadInst *LI, AvailValInBlkVect &ValuesPerBlock,
1511                         UnavailBlkVect &UnavailableBlocks) {
1512  // Okay, we have *some* definitions of the value.  This means that the value
1513  // is available in some of our (transitive) predecessors.  Lets think about
1514  // doing PRE of this load.  This will involve inserting a new load into the
1515  // predecessor when it's not available.  We could do this in general, but
1516  // prefer to not increase code size.  As such, we only do this when we know
1517  // that we only have to insert *one* load (which means we're basically moving
1518  // the load, not inserting a new one).
1519
1520  SmallPtrSet<BasicBlock *, 4> Blockers;
1521  for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
1522    Blockers.insert(UnavailableBlocks[i]);
1523
1524  // Let's find the first basic block with more than one predecessor.  Walk
1525  // backwards through predecessors if needed.
1526  BasicBlock *LoadBB = LI->getParent();
1527  BasicBlock *TmpBB = LoadBB;
1528
1529  while (TmpBB->getSinglePredecessor()) {
1530    TmpBB = TmpBB->getSinglePredecessor();
1531    if (TmpBB == LoadBB) // Infinite (unreachable) loop.
1532      return false;
1533    if (Blockers.count(TmpBB))
1534      return false;
1535
1536    // If any of these blocks has more than one successor (i.e. if the edge we
1537    // just traversed was critical), then there are other paths through this
1538    // block along which the load may not be anticipated.  Hoisting the load
1539    // above this block would be adding the load to execution paths along
1540    // which it was not previously executed.
1541    if (TmpBB->getTerminator()->getNumSuccessors() != 1)
1542      return false;
1543  }
1544
1545  assert(TmpBB);
1546  LoadBB = TmpBB;
1547
1548  // Check to see how many predecessors have the loaded value fully
1549  // available.
1550  MapVector<BasicBlock *, Value *> PredLoads;
1551  DenseMap<BasicBlock*, char> FullyAvailableBlocks;
1552  for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i)
1553    FullyAvailableBlocks[ValuesPerBlock[i].BB] = true;
1554  for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
1555    FullyAvailableBlocks[UnavailableBlocks[i]] = false;
1556
1557  SmallVector<BasicBlock *, 4> CriticalEdgePred;
1558  for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
1559       PI != E; ++PI) {
1560    BasicBlock *Pred = *PI;
1561    if (IsValueFullyAvailableInBlock(Pred, FullyAvailableBlocks, 0)) {
1562      continue;
1563    }
1564
1565    if (Pred->getTerminator()->getNumSuccessors() != 1) {
1566      if (isa<IndirectBrInst>(Pred->getTerminator())) {
1567        DEBUG(dbgs() << "COULD NOT PRE LOAD BECAUSE OF INDBR CRITICAL EDGE '"
1568              << Pred->getName() << "': " << *LI << '\n');
1569        return false;
1570      }
1571
1572      if (LoadBB->isLandingPad()) {
1573        DEBUG(dbgs()
1574              << "COULD NOT PRE LOAD BECAUSE OF LANDING PAD CRITICAL EDGE '"
1575              << Pred->getName() << "': " << *LI << '\n');
1576        return false;
1577      }
1578
1579      CriticalEdgePred.push_back(Pred);
1580    } else {
1581      // Only add the predecessors that will not be split for now.
1582      PredLoads[Pred] = nullptr;
1583    }
1584  }
1585
1586  // Decide whether PRE is profitable for this load.
1587  unsigned NumUnavailablePreds = PredLoads.size() + CriticalEdgePred.size();
1588  assert(NumUnavailablePreds != 0 &&
1589         "Fully available value should already be eliminated!");
1590
1591  // If this load is unavailable in multiple predecessors, reject it.
1592  // FIXME: If we could restructure the CFG, we could make a common pred with
1593  // all the preds that don't have an available LI and insert a new load into
1594  // that one block.
1595  if (NumUnavailablePreds != 1)
1596      return false;
1597
1598  // Split critical edges, and update the unavailable predecessors accordingly.
1599  for (BasicBlock *OrigPred : CriticalEdgePred) {
1600    BasicBlock *NewPred = splitCriticalEdges(OrigPred, LoadBB);
1601    assert(!PredLoads.count(OrigPred) && "Split edges shouldn't be in map!");
1602    PredLoads[NewPred] = nullptr;
1603    DEBUG(dbgs() << "Split critical edge " << OrigPred->getName() << "->"
1604                 << LoadBB->getName() << '\n');
1605  }
1606
1607  // Check if the load can safely be moved to all the unavailable predecessors.
1608  bool CanDoPRE = true;
1609  SmallVector<Instruction*, 8> NewInsts;
1610  for (auto &PredLoad : PredLoads) {
1611    BasicBlock *UnavailablePred = PredLoad.first;
1612
1613    // Do PHI translation to get its value in the predecessor if necessary.  The
1614    // returned pointer (if non-null) is guaranteed to dominate UnavailablePred.
1615
1616    // If all preds have a single successor, then we know it is safe to insert
1617    // the load on the pred (?!?), so we can insert code to materialize the
1618    // pointer if it is not available.
1619    PHITransAddr Address(LI->getPointerOperand(), DL);
1620    Value *LoadPtr = nullptr;
1621    LoadPtr = Address.PHITranslateWithInsertion(LoadBB, UnavailablePred,
1622                                                *DT, NewInsts);
1623
1624    // If we couldn't find or insert a computation of this phi translated value,
1625    // we fail PRE.
1626    if (!LoadPtr) {
1627      DEBUG(dbgs() << "COULDN'T INSERT PHI TRANSLATED VALUE OF: "
1628            << *LI->getPointerOperand() << "\n");
1629      CanDoPRE = false;
1630      break;
1631    }
1632
1633    PredLoad.second = LoadPtr;
1634  }
1635
1636  if (!CanDoPRE) {
1637    while (!NewInsts.empty()) {
1638      Instruction *I = NewInsts.pop_back_val();
1639      if (MD) MD->removeInstruction(I);
1640      I->eraseFromParent();
1641    }
1642    // HINT: Don't revert the edge-splitting as following transformation may
1643    // also need to split these critical edges.
1644    return !CriticalEdgePred.empty();
1645  }
1646
1647  // Okay, we can eliminate this load by inserting a reload in the predecessor
1648  // and using PHI construction to get the value in the other predecessors, do
1649  // it.
1650  DEBUG(dbgs() << "GVN REMOVING PRE LOAD: " << *LI << '\n');
1651  DEBUG(if (!NewInsts.empty())
1652          dbgs() << "INSERTED " << NewInsts.size() << " INSTS: "
1653                 << *NewInsts.back() << '\n');
1654
1655  // Assign value numbers to the new instructions.
1656  for (unsigned i = 0, e = NewInsts.size(); i != e; ++i) {
1657    // FIXME: We really _ought_ to insert these value numbers into their
1658    // parent's availability map.  However, in doing so, we risk getting into
1659    // ordering issues.  If a block hasn't been processed yet, we would be
1660    // marking a value as AVAIL-IN, which isn't what we intend.
1661    VN.lookup_or_add(NewInsts[i]);
1662  }
1663
1664  for (const auto &PredLoad : PredLoads) {
1665    BasicBlock *UnavailablePred = PredLoad.first;
1666    Value *LoadPtr = PredLoad.second;
1667
1668    Instruction *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false,
1669                                        LI->getAlignment(),
1670                                        UnavailablePred->getTerminator());
1671
1672    // Transfer the old load's TBAA tag to the new load.
1673    if (MDNode *Tag = LI->getMetadata(LLVMContext::MD_tbaa))
1674      NewLoad->setMetadata(LLVMContext::MD_tbaa, Tag);
1675
1676    // Transfer DebugLoc.
1677    NewLoad->setDebugLoc(LI->getDebugLoc());
1678
1679    // Add the newly created load.
1680    ValuesPerBlock.push_back(AvailableValueInBlock::get(UnavailablePred,
1681                                                        NewLoad));
1682    MD->invalidateCachedPointerInfo(LoadPtr);
1683    DEBUG(dbgs() << "GVN INSERTED " << *NewLoad << '\n');
1684  }
1685
1686  // Perform PHI construction.
1687  Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
1688  LI->replaceAllUsesWith(V);
1689  if (isa<PHINode>(V))
1690    V->takeName(LI);
1691  if (V->getType()->getScalarType()->isPointerTy())
1692    MD->invalidateCachedPointerInfo(V);
1693  markInstructionForDeletion(LI);
1694  ++NumPRELoad;
1695  return true;
1696}
1697
1698/// processNonLocalLoad - Attempt to eliminate a load whose dependencies are
1699/// non-local by performing PHI construction.
1700bool GVN::processNonLocalLoad(LoadInst *LI) {
1701  // Step 1: Find the non-local dependencies of the load.
1702  LoadDepVect Deps;
1703  AliasAnalysis::Location Loc = VN.getAliasAnalysis()->getLocation(LI);
1704  MD->getNonLocalPointerDependency(Loc, true, LI->getParent(), Deps);
1705
1706  // If we had to process more than one hundred blocks to find the
1707  // dependencies, this load isn't worth worrying about.  Optimizing
1708  // it will be too expensive.
1709  unsigned NumDeps = Deps.size();
1710  if (NumDeps > 100)
1711    return false;
1712
1713  // If we had a phi translation failure, we'll have a single entry which is a
1714  // clobber in the current block.  Reject this early.
1715  if (NumDeps == 1 &&
1716      !Deps[0].getResult().isDef() && !Deps[0].getResult().isClobber()) {
1717    DEBUG(
1718      dbgs() << "GVN: non-local load ";
1719      LI->printAsOperand(dbgs());
1720      dbgs() << " has unknown dependencies\n";
1721    );
1722    return false;
1723  }
1724
1725  // Step 2: Analyze the availability of the load
1726  AvailValInBlkVect ValuesPerBlock;
1727  UnavailBlkVect UnavailableBlocks;
1728  AnalyzeLoadAvailability(LI, Deps, ValuesPerBlock, UnavailableBlocks);
1729
1730  // If we have no predecessors that produce a known value for this load, exit
1731  // early.
1732  if (ValuesPerBlock.empty())
1733    return false;
1734
1735  // Step 3: Eliminate fully redundancy.
1736  //
1737  // If all of the instructions we depend on produce a known value for this
1738  // load, then it is fully redundant and we can use PHI insertion to compute
1739  // its value.  Insert PHIs and remove the fully redundant value now.
1740  if (UnavailableBlocks.empty()) {
1741    DEBUG(dbgs() << "GVN REMOVING NONLOCAL LOAD: " << *LI << '\n');
1742
1743    // Perform PHI construction.
1744    Value *V = ConstructSSAForLoadSet(LI, ValuesPerBlock, *this);
1745    LI->replaceAllUsesWith(V);
1746
1747    if (isa<PHINode>(V))
1748      V->takeName(LI);
1749    if (V->getType()->getScalarType()->isPointerTy())
1750      MD->invalidateCachedPointerInfo(V);
1751    markInstructionForDeletion(LI);
1752    ++NumGVNLoad;
1753    return true;
1754  }
1755
1756  // Step 4: Eliminate partial redundancy.
1757  if (!EnablePRE || !EnableLoadPRE)
1758    return false;
1759
1760  return PerformLoadPRE(LI, ValuesPerBlock, UnavailableBlocks);
1761}
1762
1763
1764static void patchReplacementInstruction(Instruction *I, Value *Repl) {
1765  // Patch the replacement so that it is not more restrictive than the value
1766  // being replaced.
1767  BinaryOperator *Op = dyn_cast<BinaryOperator>(I);
1768  BinaryOperator *ReplOp = dyn_cast<BinaryOperator>(Repl);
1769  if (Op && ReplOp && isa<OverflowingBinaryOperator>(Op) &&
1770      isa<OverflowingBinaryOperator>(ReplOp)) {
1771    if (ReplOp->hasNoSignedWrap() && !Op->hasNoSignedWrap())
1772      ReplOp->setHasNoSignedWrap(false);
1773    if (ReplOp->hasNoUnsignedWrap() && !Op->hasNoUnsignedWrap())
1774      ReplOp->setHasNoUnsignedWrap(false);
1775  }
1776  if (Instruction *ReplInst = dyn_cast<Instruction>(Repl)) {
1777    SmallVector<std::pair<unsigned, MDNode*>, 4> Metadata;
1778    ReplInst->getAllMetadataOtherThanDebugLoc(Metadata);
1779    for (int i = 0, n = Metadata.size(); i < n; ++i) {
1780      unsigned Kind = Metadata[i].first;
1781      MDNode *IMD = I->getMetadata(Kind);
1782      MDNode *ReplMD = Metadata[i].second;
1783      switch(Kind) {
1784      default:
1785        ReplInst->setMetadata(Kind, nullptr); // Remove unknown metadata
1786        break;
1787      case LLVMContext::MD_dbg:
1788        llvm_unreachable("getAllMetadataOtherThanDebugLoc returned a MD_dbg");
1789      case LLVMContext::MD_tbaa:
1790        ReplInst->setMetadata(Kind, MDNode::getMostGenericTBAA(IMD, ReplMD));
1791        break;
1792      case LLVMContext::MD_range:
1793        ReplInst->setMetadata(Kind, MDNode::getMostGenericRange(IMD, ReplMD));
1794        break;
1795      case LLVMContext::MD_prof:
1796        llvm_unreachable("MD_prof in a non-terminator instruction");
1797        break;
1798      case LLVMContext::MD_fpmath:
1799        ReplInst->setMetadata(Kind, MDNode::getMostGenericFPMath(IMD, ReplMD));
1800        break;
1801      case LLVMContext::MD_invariant_load:
1802        // Only set the !invariant.load if it is present in both instructions.
1803        ReplInst->setMetadata(Kind, IMD);
1804        break;
1805      }
1806    }
1807  }
1808}
1809
1810static void patchAndReplaceAllUsesWith(Instruction *I, Value *Repl) {
1811  patchReplacementInstruction(I, Repl);
1812  I->replaceAllUsesWith(Repl);
1813}
1814
1815/// processLoad - Attempt to eliminate a load, first by eliminating it
1816/// locally, and then attempting non-local elimination if that fails.
1817bool GVN::processLoad(LoadInst *L) {
1818  if (!MD)
1819    return false;
1820
1821  if (!L->isSimple())
1822    return false;
1823
1824  if (L->use_empty()) {
1825    markInstructionForDeletion(L);
1826    return true;
1827  }
1828
1829  // ... to a pointer that has been loaded from before...
1830  MemDepResult Dep = MD->getDependency(L);
1831
1832  // If we have a clobber and target data is around, see if this is a clobber
1833  // that we can fix up through code synthesis.
1834  if (Dep.isClobber() && DL) {
1835    // Check to see if we have something like this:
1836    //   store i32 123, i32* %P
1837    //   %A = bitcast i32* %P to i8*
1838    //   %B = gep i8* %A, i32 1
1839    //   %C = load i8* %B
1840    //
1841    // We could do that by recognizing if the clobber instructions are obviously
1842    // a common base + constant offset, and if the previous store (or memset)
1843    // completely covers this load.  This sort of thing can happen in bitfield
1844    // access code.
1845    Value *AvailVal = nullptr;
1846    if (StoreInst *DepSI = dyn_cast<StoreInst>(Dep.getInst())) {
1847      int Offset = AnalyzeLoadFromClobberingStore(L->getType(),
1848                                                  L->getPointerOperand(),
1849                                                  DepSI, *DL);
1850      if (Offset != -1)
1851        AvailVal = GetStoreValueForLoad(DepSI->getValueOperand(), Offset,
1852                                        L->getType(), L, *DL);
1853    }
1854
1855    // Check to see if we have something like this:
1856    //    load i32* P
1857    //    load i8* (P+1)
1858    // if we have this, replace the later with an extraction from the former.
1859    if (LoadInst *DepLI = dyn_cast<LoadInst>(Dep.getInst())) {
1860      // If this is a clobber and L is the first instruction in its block, then
1861      // we have the first instruction in the entry block.
1862      if (DepLI == L)
1863        return false;
1864
1865      int Offset = AnalyzeLoadFromClobberingLoad(L->getType(),
1866                                                 L->getPointerOperand(),
1867                                                 DepLI, *DL);
1868      if (Offset != -1)
1869        AvailVal = GetLoadValueForLoad(DepLI, Offset, L->getType(), L, *this);
1870    }
1871
1872    // If the clobbering value is a memset/memcpy/memmove, see if we can forward
1873    // a value on from it.
1874    if (MemIntrinsic *DepMI = dyn_cast<MemIntrinsic>(Dep.getInst())) {
1875      int Offset = AnalyzeLoadFromClobberingMemInst(L->getType(),
1876                                                    L->getPointerOperand(),
1877                                                    DepMI, *DL);
1878      if (Offset != -1)
1879        AvailVal = GetMemInstValueForLoad(DepMI, Offset, L->getType(), L, *DL);
1880    }
1881
1882    if (AvailVal) {
1883      DEBUG(dbgs() << "GVN COERCED INST:\n" << *Dep.getInst() << '\n'
1884            << *AvailVal << '\n' << *L << "\n\n\n");
1885
1886      // Replace the load!
1887      L->replaceAllUsesWith(AvailVal);
1888      if (AvailVal->getType()->getScalarType()->isPointerTy())
1889        MD->invalidateCachedPointerInfo(AvailVal);
1890      markInstructionForDeletion(L);
1891      ++NumGVNLoad;
1892      return true;
1893    }
1894  }
1895
1896  // If the value isn't available, don't do anything!
1897  if (Dep.isClobber()) {
1898    DEBUG(
1899      // fast print dep, using operator<< on instruction is too slow.
1900      dbgs() << "GVN: load ";
1901      L->printAsOperand(dbgs());
1902      Instruction *I = Dep.getInst();
1903      dbgs() << " is clobbered by " << *I << '\n';
1904    );
1905    return false;
1906  }
1907
1908  // If it is defined in another block, try harder.
1909  if (Dep.isNonLocal())
1910    return processNonLocalLoad(L);
1911
1912  if (!Dep.isDef()) {
1913    DEBUG(
1914      // fast print dep, using operator<< on instruction is too slow.
1915      dbgs() << "GVN: load ";
1916      L->printAsOperand(dbgs());
1917      dbgs() << " has unknown dependence\n";
1918    );
1919    return false;
1920  }
1921
1922  Instruction *DepInst = Dep.getInst();
1923  if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) {
1924    Value *StoredVal = DepSI->getValueOperand();
1925
1926    // The store and load are to a must-aliased pointer, but they may not
1927    // actually have the same type.  See if we know how to reuse the stored
1928    // value (depending on its type).
1929    if (StoredVal->getType() != L->getType()) {
1930      if (DL) {
1931        StoredVal = CoerceAvailableValueToLoadType(StoredVal, L->getType(),
1932                                                   L, *DL);
1933        if (!StoredVal)
1934          return false;
1935
1936        DEBUG(dbgs() << "GVN COERCED STORE:\n" << *DepSI << '\n' << *StoredVal
1937                     << '\n' << *L << "\n\n\n");
1938      }
1939      else
1940        return false;
1941    }
1942
1943    // Remove it!
1944    L->replaceAllUsesWith(StoredVal);
1945    if (StoredVal->getType()->getScalarType()->isPointerTy())
1946      MD->invalidateCachedPointerInfo(StoredVal);
1947    markInstructionForDeletion(L);
1948    ++NumGVNLoad;
1949    return true;
1950  }
1951
1952  if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInst)) {
1953    Value *AvailableVal = DepLI;
1954
1955    // The loads are of a must-aliased pointer, but they may not actually have
1956    // the same type.  See if we know how to reuse the previously loaded value
1957    // (depending on its type).
1958    if (DepLI->getType() != L->getType()) {
1959      if (DL) {
1960        AvailableVal = CoerceAvailableValueToLoadType(DepLI, L->getType(),
1961                                                      L, *DL);
1962        if (!AvailableVal)
1963          return false;
1964
1965        DEBUG(dbgs() << "GVN COERCED LOAD:\n" << *DepLI << "\n" << *AvailableVal
1966                     << "\n" << *L << "\n\n\n");
1967      }
1968      else
1969        return false;
1970    }
1971
1972    // Remove it!
1973    patchAndReplaceAllUsesWith(L, AvailableVal);
1974    if (DepLI->getType()->getScalarType()->isPointerTy())
1975      MD->invalidateCachedPointerInfo(DepLI);
1976    markInstructionForDeletion(L);
1977    ++NumGVNLoad;
1978    return true;
1979  }
1980
1981  // If this load really doesn't depend on anything, then we must be loading an
1982  // undef value.  This can happen when loading for a fresh allocation with no
1983  // intervening stores, for example.
1984  if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI)) {
1985    L->replaceAllUsesWith(UndefValue::get(L->getType()));
1986    markInstructionForDeletion(L);
1987    ++NumGVNLoad;
1988    return true;
1989  }
1990
1991  // If this load occurs either right after a lifetime begin,
1992  // then the loaded value is undefined.
1993  if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(DepInst)) {
1994    if (II->getIntrinsicID() == Intrinsic::lifetime_start) {
1995      L->replaceAllUsesWith(UndefValue::get(L->getType()));
1996      markInstructionForDeletion(L);
1997      ++NumGVNLoad;
1998      return true;
1999    }
2000  }
2001
2002  // If this load follows a calloc (which zero initializes memory),
2003  // then the loaded value is zero
2004  if (isCallocLikeFn(DepInst, TLI)) {
2005    L->replaceAllUsesWith(Constant::getNullValue(L->getType()));
2006    markInstructionForDeletion(L);
2007    ++NumGVNLoad;
2008    return true;
2009  }
2010
2011  return false;
2012}
2013
2014// findLeader - In order to find a leader for a given value number at a
2015// specific basic block, we first obtain the list of all Values for that number,
2016// and then scan the list to find one whose block dominates the block in
2017// question.  This is fast because dominator tree queries consist of only
2018// a few comparisons of DFS numbers.
2019Value *GVN::findLeader(const BasicBlock *BB, uint32_t num) {
2020  LeaderTableEntry Vals = LeaderTable[num];
2021  if (!Vals.Val) return nullptr;
2022
2023  Value *Val = nullptr;
2024  if (DT->dominates(Vals.BB, BB)) {
2025    Val = Vals.Val;
2026    if (isa<Constant>(Val)) return Val;
2027  }
2028
2029  LeaderTableEntry* Next = Vals.Next;
2030  while (Next) {
2031    if (DT->dominates(Next->BB, BB)) {
2032      if (isa<Constant>(Next->Val)) return Next->Val;
2033      if (!Val) Val = Next->Val;
2034    }
2035
2036    Next = Next->Next;
2037  }
2038
2039  return Val;
2040}
2041
2042/// replaceAllDominatedUsesWith - Replace all uses of 'From' with 'To' if the
2043/// use is dominated by the given basic block.  Returns the number of uses that
2044/// were replaced.
2045unsigned GVN::replaceAllDominatedUsesWith(Value *From, Value *To,
2046                                          const BasicBlockEdge &Root) {
2047  unsigned Count = 0;
2048  for (Value::use_iterator UI = From->use_begin(), UE = From->use_end();
2049       UI != UE; ) {
2050    Use &U = *UI++;
2051
2052    if (DT->dominates(Root, U)) {
2053      U.set(To);
2054      ++Count;
2055    }
2056  }
2057  return Count;
2058}
2059
2060/// isOnlyReachableViaThisEdge - There is an edge from 'Src' to 'Dst'.  Return
2061/// true if every path from the entry block to 'Dst' passes via this edge.  In
2062/// particular 'Dst' must not be reachable via another edge from 'Src'.
2063static bool isOnlyReachableViaThisEdge(const BasicBlockEdge &E,
2064                                       DominatorTree *DT) {
2065  // While in theory it is interesting to consider the case in which Dst has
2066  // more than one predecessor, because Dst might be part of a loop which is
2067  // only reachable from Src, in practice it is pointless since at the time
2068  // GVN runs all such loops have preheaders, which means that Dst will have
2069  // been changed to have only one predecessor, namely Src.
2070  const BasicBlock *Pred = E.getEnd()->getSinglePredecessor();
2071  const BasicBlock *Src = E.getStart();
2072  assert((!Pred || Pred == Src) && "No edge between these basic blocks!");
2073  (void)Src;
2074  return Pred != nullptr;
2075}
2076
2077/// propagateEquality - The given values are known to be equal in every block
2078/// dominated by 'Root'.  Exploit this, for example by replacing 'LHS' with
2079/// 'RHS' everywhere in the scope.  Returns whether a change was made.
2080bool GVN::propagateEquality(Value *LHS, Value *RHS,
2081                            const BasicBlockEdge &Root) {
2082  SmallVector<std::pair<Value*, Value*>, 4> Worklist;
2083  Worklist.push_back(std::make_pair(LHS, RHS));
2084  bool Changed = false;
2085  // For speed, compute a conservative fast approximation to
2086  // DT->dominates(Root, Root.getEnd());
2087  bool RootDominatesEnd = isOnlyReachableViaThisEdge(Root, DT);
2088
2089  while (!Worklist.empty()) {
2090    std::pair<Value*, Value*> Item = Worklist.pop_back_val();
2091    LHS = Item.first; RHS = Item.second;
2092
2093    if (LHS == RHS) continue;
2094    assert(LHS->getType() == RHS->getType() && "Equality but unequal types!");
2095
2096    // Don't try to propagate equalities between constants.
2097    if (isa<Constant>(LHS) && isa<Constant>(RHS)) continue;
2098
2099    // Prefer a constant on the right-hand side, or an Argument if no constants.
2100    if (isa<Constant>(LHS) || (isa<Argument>(LHS) && !isa<Constant>(RHS)))
2101      std::swap(LHS, RHS);
2102    assert((isa<Argument>(LHS) || isa<Instruction>(LHS)) && "Unexpected value!");
2103
2104    // If there is no obvious reason to prefer the left-hand side over the right-
2105    // hand side, ensure the longest lived term is on the right-hand side, so the
2106    // shortest lived term will be replaced by the longest lived.  This tends to
2107    // expose more simplifications.
2108    uint32_t LVN = VN.lookup_or_add(LHS);
2109    if ((isa<Argument>(LHS) && isa<Argument>(RHS)) ||
2110        (isa<Instruction>(LHS) && isa<Instruction>(RHS))) {
2111      // Move the 'oldest' value to the right-hand side, using the value number as
2112      // a proxy for age.
2113      uint32_t RVN = VN.lookup_or_add(RHS);
2114      if (LVN < RVN) {
2115        std::swap(LHS, RHS);
2116        LVN = RVN;
2117      }
2118    }
2119
2120    // If value numbering later sees that an instruction in the scope is equal
2121    // to 'LHS' then ensure it will be turned into 'RHS'.  In order to preserve
2122    // the invariant that instructions only occur in the leader table for their
2123    // own value number (this is used by removeFromLeaderTable), do not do this
2124    // if RHS is an instruction (if an instruction in the scope is morphed into
2125    // LHS then it will be turned into RHS by the next GVN iteration anyway, so
2126    // using the leader table is about compiling faster, not optimizing better).
2127    // The leader table only tracks basic blocks, not edges. Only add to if we
2128    // have the simple case where the edge dominates the end.
2129    if (RootDominatesEnd && !isa<Instruction>(RHS))
2130      addToLeaderTable(LVN, RHS, Root.getEnd());
2131
2132    // Replace all occurrences of 'LHS' with 'RHS' everywhere in the scope.  As
2133    // LHS always has at least one use that is not dominated by Root, this will
2134    // never do anything if LHS has only one use.
2135    if (!LHS->hasOneUse()) {
2136      unsigned NumReplacements = replaceAllDominatedUsesWith(LHS, RHS, Root);
2137      Changed |= NumReplacements > 0;
2138      NumGVNEqProp += NumReplacements;
2139    }
2140
2141    // Now try to deduce additional equalities from this one.  For example, if the
2142    // known equality was "(A != B)" == "false" then it follows that A and B are
2143    // equal in the scope.  Only boolean equalities with an explicit true or false
2144    // RHS are currently supported.
2145    if (!RHS->getType()->isIntegerTy(1))
2146      // Not a boolean equality - bail out.
2147      continue;
2148    ConstantInt *CI = dyn_cast<ConstantInt>(RHS);
2149    if (!CI)
2150      // RHS neither 'true' nor 'false' - bail out.
2151      continue;
2152    // Whether RHS equals 'true'.  Otherwise it equals 'false'.
2153    bool isKnownTrue = CI->isAllOnesValue();
2154    bool isKnownFalse = !isKnownTrue;
2155
2156    // If "A && B" is known true then both A and B are known true.  If "A || B"
2157    // is known false then both A and B are known false.
2158    Value *A, *B;
2159    if ((isKnownTrue && match(LHS, m_And(m_Value(A), m_Value(B)))) ||
2160        (isKnownFalse && match(LHS, m_Or(m_Value(A), m_Value(B))))) {
2161      Worklist.push_back(std::make_pair(A, RHS));
2162      Worklist.push_back(std::make_pair(B, RHS));
2163      continue;
2164    }
2165
2166    // If we are propagating an equality like "(A == B)" == "true" then also
2167    // propagate the equality A == B.  When propagating a comparison such as
2168    // "(A >= B)" == "true", replace all instances of "A < B" with "false".
2169    if (ICmpInst *Cmp = dyn_cast<ICmpInst>(LHS)) {
2170      Value *Op0 = Cmp->getOperand(0), *Op1 = Cmp->getOperand(1);
2171
2172      // If "A == B" is known true, or "A != B" is known false, then replace
2173      // A with B everywhere in the scope.
2174      if ((isKnownTrue && Cmp->getPredicate() == CmpInst::ICMP_EQ) ||
2175          (isKnownFalse && Cmp->getPredicate() == CmpInst::ICMP_NE))
2176        Worklist.push_back(std::make_pair(Op0, Op1));
2177
2178      // If "A >= B" is known true, replace "A < B" with false everywhere.
2179      CmpInst::Predicate NotPred = Cmp->getInversePredicate();
2180      Constant *NotVal = ConstantInt::get(Cmp->getType(), isKnownFalse);
2181      // Since we don't have the instruction "A < B" immediately to hand, work out
2182      // the value number that it would have and use that to find an appropriate
2183      // instruction (if any).
2184      uint32_t NextNum = VN.getNextUnusedValueNumber();
2185      uint32_t Num = VN.lookup_or_add_cmp(Cmp->getOpcode(), NotPred, Op0, Op1);
2186      // If the number we were assigned was brand new then there is no point in
2187      // looking for an instruction realizing it: there cannot be one!
2188      if (Num < NextNum) {
2189        Value *NotCmp = findLeader(Root.getEnd(), Num);
2190        if (NotCmp && isa<Instruction>(NotCmp)) {
2191          unsigned NumReplacements =
2192            replaceAllDominatedUsesWith(NotCmp, NotVal, Root);
2193          Changed |= NumReplacements > 0;
2194          NumGVNEqProp += NumReplacements;
2195        }
2196      }
2197      // Ensure that any instruction in scope that gets the "A < B" value number
2198      // is replaced with false.
2199      // The leader table only tracks basic blocks, not edges. Only add to if we
2200      // have the simple case where the edge dominates the end.
2201      if (RootDominatesEnd)
2202        addToLeaderTable(Num, NotVal, Root.getEnd());
2203
2204      continue;
2205    }
2206  }
2207
2208  return Changed;
2209}
2210
2211/// processInstruction - When calculating availability, handle an instruction
2212/// by inserting it into the appropriate sets
2213bool GVN::processInstruction(Instruction *I) {
2214  // Ignore dbg info intrinsics.
2215  if (isa<DbgInfoIntrinsic>(I))
2216    return false;
2217
2218  // If the instruction can be easily simplified then do so now in preference
2219  // to value numbering it.  Value numbering often exposes redundancies, for
2220  // example if it determines that %y is equal to %x then the instruction
2221  // "%z = and i32 %x, %y" becomes "%z = and i32 %x, %x" which we now simplify.
2222  if (Value *V = SimplifyInstruction(I, DL, TLI, DT)) {
2223    I->replaceAllUsesWith(V);
2224    if (MD && V->getType()->getScalarType()->isPointerTy())
2225      MD->invalidateCachedPointerInfo(V);
2226    markInstructionForDeletion(I);
2227    ++NumGVNSimpl;
2228    return true;
2229  }
2230
2231  if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
2232    if (processLoad(LI))
2233      return true;
2234
2235    unsigned Num = VN.lookup_or_add(LI);
2236    addToLeaderTable(Num, LI, LI->getParent());
2237    return false;
2238  }
2239
2240  // For conditional branches, we can perform simple conditional propagation on
2241  // the condition value itself.
2242  if (BranchInst *BI = dyn_cast<BranchInst>(I)) {
2243    if (!BI->isConditional())
2244      return false;
2245
2246    if (isa<Constant>(BI->getCondition()))
2247      return processFoldableCondBr(BI);
2248
2249    Value *BranchCond = BI->getCondition();
2250    BasicBlock *TrueSucc = BI->getSuccessor(0);
2251    BasicBlock *FalseSucc = BI->getSuccessor(1);
2252    // Avoid multiple edges early.
2253    if (TrueSucc == FalseSucc)
2254      return false;
2255
2256    BasicBlock *Parent = BI->getParent();
2257    bool Changed = false;
2258
2259    Value *TrueVal = ConstantInt::getTrue(TrueSucc->getContext());
2260    BasicBlockEdge TrueE(Parent, TrueSucc);
2261    Changed |= propagateEquality(BranchCond, TrueVal, TrueE);
2262
2263    Value *FalseVal = ConstantInt::getFalse(FalseSucc->getContext());
2264    BasicBlockEdge FalseE(Parent, FalseSucc);
2265    Changed |= propagateEquality(BranchCond, FalseVal, FalseE);
2266
2267    return Changed;
2268  }
2269
2270  // For switches, propagate the case values into the case destinations.
2271  if (SwitchInst *SI = dyn_cast<SwitchInst>(I)) {
2272    Value *SwitchCond = SI->getCondition();
2273    BasicBlock *Parent = SI->getParent();
2274    bool Changed = false;
2275
2276    // Remember how many outgoing edges there are to every successor.
2277    SmallDenseMap<BasicBlock *, unsigned, 16> SwitchEdges;
2278    for (unsigned i = 0, n = SI->getNumSuccessors(); i != n; ++i)
2279      ++SwitchEdges[SI->getSuccessor(i)];
2280
2281    for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
2282         i != e; ++i) {
2283      BasicBlock *Dst = i.getCaseSuccessor();
2284      // If there is only a single edge, propagate the case value into it.
2285      if (SwitchEdges.lookup(Dst) == 1) {
2286        BasicBlockEdge E(Parent, Dst);
2287        Changed |= propagateEquality(SwitchCond, i.getCaseValue(), E);
2288      }
2289    }
2290    return Changed;
2291  }
2292
2293  // Instructions with void type don't return a value, so there's
2294  // no point in trying to find redundancies in them.
2295  if (I->getType()->isVoidTy()) return false;
2296
2297  uint32_t NextNum = VN.getNextUnusedValueNumber();
2298  unsigned Num = VN.lookup_or_add(I);
2299
2300  // Allocations are always uniquely numbered, so we can save time and memory
2301  // by fast failing them.
2302  if (isa<AllocaInst>(I) || isa<TerminatorInst>(I) || isa<PHINode>(I)) {
2303    addToLeaderTable(Num, I, I->getParent());
2304    return false;
2305  }
2306
2307  // If the number we were assigned was a brand new VN, then we don't
2308  // need to do a lookup to see if the number already exists
2309  // somewhere in the domtree: it can't!
2310  if (Num >= NextNum) {
2311    addToLeaderTable(Num, I, I->getParent());
2312    return false;
2313  }
2314
2315  // Perform fast-path value-number based elimination of values inherited from
2316  // dominators.
2317  Value *repl = findLeader(I->getParent(), Num);
2318  if (!repl) {
2319    // Failure, just remember this instance for future use.
2320    addToLeaderTable(Num, I, I->getParent());
2321    return false;
2322  }
2323
2324  // Remove it!
2325  patchAndReplaceAllUsesWith(I, repl);
2326  if (MD && repl->getType()->getScalarType()->isPointerTy())
2327    MD->invalidateCachedPointerInfo(repl);
2328  markInstructionForDeletion(I);
2329  return true;
2330}
2331
2332/// runOnFunction - This is the main transformation entry point for a function.
2333bool GVN::runOnFunction(Function& F) {
2334  if (skipOptnoneFunction(F))
2335    return false;
2336
2337  if (!NoLoads)
2338    MD = &getAnalysis<MemoryDependenceAnalysis>();
2339  DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
2340  DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
2341  DL = DLP ? &DLP->getDataLayout() : nullptr;
2342  TLI = &getAnalysis<TargetLibraryInfo>();
2343  VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>());
2344  VN.setMemDep(MD);
2345  VN.setDomTree(DT);
2346
2347  bool Changed = false;
2348  bool ShouldContinue = true;
2349
2350  // Merge unconditional branches, allowing PRE to catch more
2351  // optimization opportunities.
2352  for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) {
2353    BasicBlock *BB = FI++;
2354
2355    bool removedBlock = MergeBlockIntoPredecessor(BB, this);
2356    if (removedBlock) ++NumGVNBlocks;
2357
2358    Changed |= removedBlock;
2359  }
2360
2361  unsigned Iteration = 0;
2362  while (ShouldContinue) {
2363    DEBUG(dbgs() << "GVN iteration: " << Iteration << "\n");
2364    ShouldContinue = iterateOnFunction(F);
2365    Changed |= ShouldContinue;
2366    ++Iteration;
2367  }
2368
2369  if (EnablePRE) {
2370    // Fabricate val-num for dead-code in order to suppress assertion in
2371    // performPRE().
2372    assignValNumForDeadCode();
2373    bool PREChanged = true;
2374    while (PREChanged) {
2375      PREChanged = performPRE(F);
2376      Changed |= PREChanged;
2377    }
2378  }
2379
2380  // FIXME: Should perform GVN again after PRE does something.  PRE can move
2381  // computations into blocks where they become fully redundant.  Note that
2382  // we can't do this until PRE's critical edge splitting updates memdep.
2383  // Actually, when this happens, we should just fully integrate PRE into GVN.
2384
2385  cleanupGlobalSets();
2386  // Do not cleanup DeadBlocks in cleanupGlobalSets() as it's called for each
2387  // iteration.
2388  DeadBlocks.clear();
2389
2390  return Changed;
2391}
2392
2393
2394bool GVN::processBlock(BasicBlock *BB) {
2395  // FIXME: Kill off InstrsToErase by doing erasing eagerly in a helper function
2396  // (and incrementing BI before processing an instruction).
2397  assert(InstrsToErase.empty() &&
2398         "We expect InstrsToErase to be empty across iterations");
2399  if (DeadBlocks.count(BB))
2400    return false;
2401
2402  bool ChangedFunction = false;
2403
2404  for (BasicBlock::iterator BI = BB->begin(), BE = BB->end();
2405       BI != BE;) {
2406    ChangedFunction |= processInstruction(BI);
2407    if (InstrsToErase.empty()) {
2408      ++BI;
2409      continue;
2410    }
2411
2412    // If we need some instructions deleted, do it now.
2413    NumGVNInstr += InstrsToErase.size();
2414
2415    // Avoid iterator invalidation.
2416    bool AtStart = BI == BB->begin();
2417    if (!AtStart)
2418      --BI;
2419
2420    for (SmallVectorImpl<Instruction *>::iterator I = InstrsToErase.begin(),
2421         E = InstrsToErase.end(); I != E; ++I) {
2422      DEBUG(dbgs() << "GVN removed: " << **I << '\n');
2423      if (MD) MD->removeInstruction(*I);
2424      DEBUG(verifyRemoved(*I));
2425      (*I)->eraseFromParent();
2426    }
2427    InstrsToErase.clear();
2428
2429    if (AtStart)
2430      BI = BB->begin();
2431    else
2432      ++BI;
2433  }
2434
2435  return ChangedFunction;
2436}
2437
2438/// performPRE - Perform a purely local form of PRE that looks for diamond
2439/// control flow patterns and attempts to perform simple PRE at the join point.
2440bool GVN::performPRE(Function &F) {
2441  bool Changed = false;
2442  SmallVector<std::pair<Value*, BasicBlock*>, 8> predMap;
2443  for (BasicBlock *CurrentBlock : depth_first(&F.getEntryBlock())) {
2444    // Nothing to PRE in the entry block.
2445    if (CurrentBlock == &F.getEntryBlock()) continue;
2446
2447    // Don't perform PRE on a landing pad.
2448    if (CurrentBlock->isLandingPad()) continue;
2449
2450    for (BasicBlock::iterator BI = CurrentBlock->begin(),
2451         BE = CurrentBlock->end(); BI != BE; ) {
2452      Instruction *CurInst = BI++;
2453
2454      if (isa<AllocaInst>(CurInst) ||
2455          isa<TerminatorInst>(CurInst) || isa<PHINode>(CurInst) ||
2456          CurInst->getType()->isVoidTy() ||
2457          CurInst->mayReadFromMemory() || CurInst->mayHaveSideEffects() ||
2458          isa<DbgInfoIntrinsic>(CurInst))
2459        continue;
2460
2461      // Don't do PRE on compares. The PHI would prevent CodeGenPrepare from
2462      // sinking the compare again, and it would force the code generator to
2463      // move the i1 from processor flags or predicate registers into a general
2464      // purpose register.
2465      if (isa<CmpInst>(CurInst))
2466        continue;
2467
2468      // We don't currently value number ANY inline asm calls.
2469      if (CallInst *CallI = dyn_cast<CallInst>(CurInst))
2470        if (CallI->isInlineAsm())
2471          continue;
2472
2473      uint32_t ValNo = VN.lookup(CurInst);
2474
2475      // Look for the predecessors for PRE opportunities.  We're
2476      // only trying to solve the basic diamond case, where
2477      // a value is computed in the successor and one predecessor,
2478      // but not the other.  We also explicitly disallow cases
2479      // where the successor is its own predecessor, because they're
2480      // more complicated to get right.
2481      unsigned NumWith = 0;
2482      unsigned NumWithout = 0;
2483      BasicBlock *PREPred = nullptr;
2484      predMap.clear();
2485
2486      for (pred_iterator PI = pred_begin(CurrentBlock),
2487           PE = pred_end(CurrentBlock); PI != PE; ++PI) {
2488        BasicBlock *P = *PI;
2489        // We're not interested in PRE where the block is its
2490        // own predecessor, or in blocks with predecessors
2491        // that are not reachable.
2492        if (P == CurrentBlock) {
2493          NumWithout = 2;
2494          break;
2495        } else if (!DT->isReachableFromEntry(P))  {
2496          NumWithout = 2;
2497          break;
2498        }
2499
2500        Value* predV = findLeader(P, ValNo);
2501        if (!predV) {
2502          predMap.push_back(std::make_pair(static_cast<Value *>(nullptr), P));
2503          PREPred = P;
2504          ++NumWithout;
2505        } else if (predV == CurInst) {
2506          /* CurInst dominates this predecessor. */
2507          NumWithout = 2;
2508          break;
2509        } else {
2510          predMap.push_back(std::make_pair(predV, P));
2511          ++NumWith;
2512        }
2513      }
2514
2515      // Don't do PRE when it might increase code size, i.e. when
2516      // we would need to insert instructions in more than one pred.
2517      if (NumWithout != 1 || NumWith == 0)
2518        continue;
2519
2520      // Don't do PRE across indirect branch.
2521      if (isa<IndirectBrInst>(PREPred->getTerminator()))
2522        continue;
2523
2524      // We can't do PRE safely on a critical edge, so instead we schedule
2525      // the edge to be split and perform the PRE the next time we iterate
2526      // on the function.
2527      unsigned SuccNum = GetSuccessorNumber(PREPred, CurrentBlock);
2528      if (isCriticalEdge(PREPred->getTerminator(), SuccNum)) {
2529        toSplit.push_back(std::make_pair(PREPred->getTerminator(), SuccNum));
2530        continue;
2531      }
2532
2533      // Instantiate the expression in the predecessor that lacked it.
2534      // Because we are going top-down through the block, all value numbers
2535      // will be available in the predecessor by the time we need them.  Any
2536      // that weren't originally present will have been instantiated earlier
2537      // in this loop.
2538      Instruction *PREInstr = CurInst->clone();
2539      bool success = true;
2540      for (unsigned i = 0, e = CurInst->getNumOperands(); i != e; ++i) {
2541        Value *Op = PREInstr->getOperand(i);
2542        if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op))
2543          continue;
2544
2545        if (Value *V = findLeader(PREPred, VN.lookup(Op))) {
2546          PREInstr->setOperand(i, V);
2547        } else {
2548          success = false;
2549          break;
2550        }
2551      }
2552
2553      // Fail out if we encounter an operand that is not available in
2554      // the PRE predecessor.  This is typically because of loads which
2555      // are not value numbered precisely.
2556      if (!success) {
2557        DEBUG(verifyRemoved(PREInstr));
2558        delete PREInstr;
2559        continue;
2560      }
2561
2562      PREInstr->insertBefore(PREPred->getTerminator());
2563      PREInstr->setName(CurInst->getName() + ".pre");
2564      PREInstr->setDebugLoc(CurInst->getDebugLoc());
2565      VN.add(PREInstr, ValNo);
2566      ++NumGVNPRE;
2567
2568      // Update the availability map to include the new instruction.
2569      addToLeaderTable(ValNo, PREInstr, PREPred);
2570
2571      // Create a PHI to make the value available in this block.
2572      PHINode* Phi = PHINode::Create(CurInst->getType(), predMap.size(),
2573                                     CurInst->getName() + ".pre-phi",
2574                                     CurrentBlock->begin());
2575      for (unsigned i = 0, e = predMap.size(); i != e; ++i) {
2576        if (Value *V = predMap[i].first)
2577          Phi->addIncoming(V, predMap[i].second);
2578        else
2579          Phi->addIncoming(PREInstr, PREPred);
2580      }
2581
2582      VN.add(Phi, ValNo);
2583      addToLeaderTable(ValNo, Phi, CurrentBlock);
2584      Phi->setDebugLoc(CurInst->getDebugLoc());
2585      CurInst->replaceAllUsesWith(Phi);
2586      if (Phi->getType()->getScalarType()->isPointerTy()) {
2587        // Because we have added a PHI-use of the pointer value, it has now
2588        // "escaped" from alias analysis' perspective.  We need to inform
2589        // AA of this.
2590        for (unsigned ii = 0, ee = Phi->getNumIncomingValues(); ii != ee;
2591             ++ii) {
2592          unsigned jj = PHINode::getOperandNumForIncomingValue(ii);
2593          VN.getAliasAnalysis()->addEscapingUse(Phi->getOperandUse(jj));
2594        }
2595
2596        if (MD)
2597          MD->invalidateCachedPointerInfo(Phi);
2598      }
2599      VN.erase(CurInst);
2600      removeFromLeaderTable(ValNo, CurInst, CurrentBlock);
2601
2602      DEBUG(dbgs() << "GVN PRE removed: " << *CurInst << '\n');
2603      if (MD) MD->removeInstruction(CurInst);
2604      DEBUG(verifyRemoved(CurInst));
2605      CurInst->eraseFromParent();
2606      Changed = true;
2607    }
2608  }
2609
2610  if (splitCriticalEdges())
2611    Changed = true;
2612
2613  return Changed;
2614}
2615
2616/// Split the critical edge connecting the given two blocks, and return
2617/// the block inserted to the critical edge.
2618BasicBlock *GVN::splitCriticalEdges(BasicBlock *Pred, BasicBlock *Succ) {
2619  BasicBlock *BB = SplitCriticalEdge(Pred, Succ, this);
2620  if (MD)
2621    MD->invalidateCachedPredecessors();
2622  return BB;
2623}
2624
2625/// splitCriticalEdges - Split critical edges found during the previous
2626/// iteration that may enable further optimization.
2627bool GVN::splitCriticalEdges() {
2628  if (toSplit.empty())
2629    return false;
2630  do {
2631    std::pair<TerminatorInst*, unsigned> Edge = toSplit.pop_back_val();
2632    SplitCriticalEdge(Edge.first, Edge.second, this);
2633  } while (!toSplit.empty());
2634  if (MD) MD->invalidateCachedPredecessors();
2635  return true;
2636}
2637
2638/// iterateOnFunction - Executes one iteration of GVN
2639bool GVN::iterateOnFunction(Function &F) {
2640  cleanupGlobalSets();
2641
2642  // Top-down walk of the dominator tree
2643  bool Changed = false;
2644#if 0
2645  // Needed for value numbering with phi construction to work.
2646  ReversePostOrderTraversal<Function*> RPOT(&F);
2647  for (ReversePostOrderTraversal<Function*>::rpo_iterator RI = RPOT.begin(),
2648       RE = RPOT.end(); RI != RE; ++RI)
2649    Changed |= processBlock(*RI);
2650#else
2651  // Save the blocks this function have before transformation begins. GVN may
2652  // split critical edge, and hence may invalidate the RPO/DT iterator.
2653  //
2654  std::vector<BasicBlock *> BBVect;
2655  BBVect.reserve(256);
2656  for (DomTreeNode *x : depth_first(DT->getRootNode()))
2657    BBVect.push_back(x->getBlock());
2658
2659  for (std::vector<BasicBlock *>::iterator I = BBVect.begin(), E = BBVect.end();
2660       I != E; I++)
2661    Changed |= processBlock(*I);
2662#endif
2663
2664  return Changed;
2665}
2666
2667void GVN::cleanupGlobalSets() {
2668  VN.clear();
2669  LeaderTable.clear();
2670  TableAllocator.Reset();
2671}
2672
2673/// verifyRemoved - Verify that the specified instruction does not occur in our
2674/// internal data structures.
2675void GVN::verifyRemoved(const Instruction *Inst) const {
2676  VN.verifyRemoved(Inst);
2677
2678  // Walk through the value number scope to make sure the instruction isn't
2679  // ferreted away in it.
2680  for (DenseMap<uint32_t, LeaderTableEntry>::const_iterator
2681       I = LeaderTable.begin(), E = LeaderTable.end(); I != E; ++I) {
2682    const LeaderTableEntry *Node = &I->second;
2683    assert(Node->Val != Inst && "Inst still in value numbering scope!");
2684
2685    while (Node->Next) {
2686      Node = Node->Next;
2687      assert(Node->Val != Inst && "Inst still in value numbering scope!");
2688    }
2689  }
2690}
2691
2692// BB is declared dead, which implied other blocks become dead as well. This
2693// function is to add all these blocks to "DeadBlocks". For the dead blocks'
2694// live successors, update their phi nodes by replacing the operands
2695// corresponding to dead blocks with UndefVal.
2696//
2697void GVN::addDeadBlock(BasicBlock *BB) {
2698  SmallVector<BasicBlock *, 4> NewDead;
2699  SmallSetVector<BasicBlock *, 4> DF;
2700
2701  NewDead.push_back(BB);
2702  while (!NewDead.empty()) {
2703    BasicBlock *D = NewDead.pop_back_val();
2704    if (DeadBlocks.count(D))
2705      continue;
2706
2707    // All blocks dominated by D are dead.
2708    SmallVector<BasicBlock *, 8> Dom;
2709    DT->getDescendants(D, Dom);
2710    DeadBlocks.insert(Dom.begin(), Dom.end());
2711
2712    // Figure out the dominance-frontier(D).
2713    for (SmallVectorImpl<BasicBlock *>::iterator I = Dom.begin(),
2714           E = Dom.end(); I != E; I++) {
2715      BasicBlock *B = *I;
2716      for (succ_iterator SI = succ_begin(B), SE = succ_end(B); SI != SE; SI++) {
2717        BasicBlock *S = *SI;
2718        if (DeadBlocks.count(S))
2719          continue;
2720
2721        bool AllPredDead = true;
2722        for (pred_iterator PI = pred_begin(S), PE = pred_end(S); PI != PE; PI++)
2723          if (!DeadBlocks.count(*PI)) {
2724            AllPredDead = false;
2725            break;
2726          }
2727
2728        if (!AllPredDead) {
2729          // S could be proved dead later on. That is why we don't update phi
2730          // operands at this moment.
2731          DF.insert(S);
2732        } else {
2733          // While S is not dominated by D, it is dead by now. This could take
2734          // place if S already have a dead predecessor before D is declared
2735          // dead.
2736          NewDead.push_back(S);
2737        }
2738      }
2739    }
2740  }
2741
2742  // For the dead blocks' live successors, update their phi nodes by replacing
2743  // the operands corresponding to dead blocks with UndefVal.
2744  for(SmallSetVector<BasicBlock *, 4>::iterator I = DF.begin(), E = DF.end();
2745        I != E; I++) {
2746    BasicBlock *B = *I;
2747    if (DeadBlocks.count(B))
2748      continue;
2749
2750    SmallVector<BasicBlock *, 4> Preds(pred_begin(B), pred_end(B));
2751    for (SmallVectorImpl<BasicBlock *>::iterator PI = Preds.begin(),
2752           PE = Preds.end(); PI != PE; PI++) {
2753      BasicBlock *P = *PI;
2754
2755      if (!DeadBlocks.count(P))
2756        continue;
2757
2758      if (isCriticalEdge(P->getTerminator(), GetSuccessorNumber(P, B))) {
2759        if (BasicBlock *S = splitCriticalEdges(P, B))
2760          DeadBlocks.insert(P = S);
2761      }
2762
2763      for (BasicBlock::iterator II = B->begin(); isa<PHINode>(II); ++II) {
2764        PHINode &Phi = cast<PHINode>(*II);
2765        Phi.setIncomingValue(Phi.getBasicBlockIndex(P),
2766                             UndefValue::get(Phi.getType()));
2767      }
2768    }
2769  }
2770}
2771
2772// If the given branch is recognized as a foldable branch (i.e. conditional
2773// branch with constant condition), it will perform following analyses and
2774// transformation.
2775//  1) If the dead out-coming edge is a critical-edge, split it. Let
2776//     R be the target of the dead out-coming edge.
2777//  1) Identify the set of dead blocks implied by the branch's dead outcoming
2778//     edge. The result of this step will be {X| X is dominated by R}
2779//  2) Identify those blocks which haves at least one dead prodecessor. The
2780//     result of this step will be dominance-frontier(R).
2781//  3) Update the PHIs in DF(R) by replacing the operands corresponding to
2782//     dead blocks with "UndefVal" in an hope these PHIs will optimized away.
2783//
2784// Return true iff *NEW* dead code are found.
2785bool GVN::processFoldableCondBr(BranchInst *BI) {
2786  if (!BI || BI->isUnconditional())
2787    return false;
2788
2789  ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
2790  if (!Cond)
2791    return false;
2792
2793  BasicBlock *DeadRoot = Cond->getZExtValue() ?
2794                         BI->getSuccessor(1) : BI->getSuccessor(0);
2795  if (DeadBlocks.count(DeadRoot))
2796    return false;
2797
2798  if (!DeadRoot->getSinglePredecessor())
2799    DeadRoot = splitCriticalEdges(BI->getParent(), DeadRoot);
2800
2801  addDeadBlock(DeadRoot);
2802  return true;
2803}
2804
2805// performPRE() will trigger assert if it come across an instruciton without
2806// associated val-num. As it normally has far more live instructions than dead
2807// instructions, it makes more sense just to "fabricate" a val-number for the
2808// dead code than checking if instruction involved is dead or not.
2809void GVN::assignValNumForDeadCode() {
2810  for (SetVector<BasicBlock *>::iterator I = DeadBlocks.begin(),
2811        E = DeadBlocks.end(); I != E; I++) {
2812    BasicBlock *BB = *I;
2813    for (BasicBlock::iterator II = BB->begin(), EE = BB->end();
2814          II != EE; II++) {
2815      Instruction *Inst = &*II;
2816      unsigned ValNum = VN.lookup_or_add(Inst);
2817      addToLeaderTable(ValNum, Inst, BB);
2818    }
2819  }
2820}
2821