1//===- ScalarReplAggregates.cpp - Scalar Replacement of Aggregates --------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This transformation implements the well known scalar replacement of
11// aggregates transformation.  This xform breaks up alloca instructions of
12// aggregate type (structure or array) into individual alloca instructions for
13// each member (if possible).  Then, if possible, it transforms the individual
14// alloca instructions into nice clean scalar SSA form.
15//
16// This combines a simple SRoA algorithm with the Mem2Reg algorithm because they
17// often interact, especially for C++ programs.  As such, iterating between
18// SRoA, then Mem2Reg until we run out of things to promote works well.
19//
20//===----------------------------------------------------------------------===//
21
22#include "llvm/Transforms/Scalar.h"
23#include "llvm/ADT/SetVector.h"
24#include "llvm/ADT/SmallVector.h"
25#include "llvm/ADT/Statistic.h"
26#include "llvm/Analysis/AssumptionCache.h"
27#include "llvm/Analysis/Loads.h"
28#include "llvm/Analysis/ValueTracking.h"
29#include "llvm/IR/CallSite.h"
30#include "llvm/IR/Constants.h"
31#include "llvm/IR/DIBuilder.h"
32#include "llvm/IR/DataLayout.h"
33#include "llvm/IR/DebugInfo.h"
34#include "llvm/IR/DerivedTypes.h"
35#include "llvm/IR/Dominators.h"
36#include "llvm/IR/Function.h"
37#include "llvm/IR/GetElementPtrTypeIterator.h"
38#include "llvm/IR/GlobalVariable.h"
39#include "llvm/IR/IRBuilder.h"
40#include "llvm/IR/Instructions.h"
41#include "llvm/IR/IntrinsicInst.h"
42#include "llvm/IR/LLVMContext.h"
43#include "llvm/IR/Module.h"
44#include "llvm/IR/Operator.h"
45#include "llvm/Pass.h"
46#include "llvm/Support/Debug.h"
47#include "llvm/Support/ErrorHandling.h"
48#include "llvm/Support/MathExtras.h"
49#include "llvm/Support/raw_ostream.h"
50#include "llvm/Transforms/Utils/Local.h"
51#include "llvm/Transforms/Utils/PromoteMemToReg.h"
52#include "llvm/Transforms/Utils/SSAUpdater.h"
53using namespace llvm;
54
55#define DEBUG_TYPE "scalarrepl"
56
57STATISTIC(NumReplaced,  "Number of allocas broken up");
58STATISTIC(NumPromoted,  "Number of allocas promoted");
59STATISTIC(NumAdjusted,  "Number of scalar allocas adjusted to allow promotion");
60STATISTIC(NumConverted, "Number of aggregates converted to scalar");
61
62namespace {
63#define SROA SROA_
64  struct SROA : public FunctionPass {
65    SROA(int T, bool hasDT, char &ID, int ST, int AT, int SLT)
66      : FunctionPass(ID), HasDomTree(hasDT) {
67      if (T == -1)
68        SRThreshold = 128;
69      else
70        SRThreshold = T;
71      if (ST == -1)
72        StructMemberThreshold = 32;
73      else
74        StructMemberThreshold = ST;
75      if (AT == -1)
76        ArrayElementThreshold = 8;
77      else
78        ArrayElementThreshold = AT;
79      if (SLT == -1)
80        // Do not limit the scalar integer load size if no threshold is given.
81        ScalarLoadThreshold = -1;
82      else
83        ScalarLoadThreshold = SLT;
84    }
85
86    bool runOnFunction(Function &F) override;
87
88    bool performScalarRepl(Function &F);
89    bool performPromotion(Function &F);
90
91  private:
92    bool HasDomTree;
93
94    /// DeadInsts - Keep track of instructions we have made dead, so that
95    /// we can remove them after we are done working.
96    SmallVector<Value*, 32> DeadInsts;
97
98    /// AllocaInfo - When analyzing uses of an alloca instruction, this captures
99    /// information about the uses.  All these fields are initialized to false
100    /// and set to true when something is learned.
101    struct AllocaInfo {
102      /// The alloca to promote.
103      AllocaInst *AI;
104
105      /// CheckedPHIs - This is a set of verified PHI nodes, to prevent infinite
106      /// looping and avoid redundant work.
107      SmallPtrSet<PHINode*, 8> CheckedPHIs;
108
109      /// isUnsafe - This is set to true if the alloca cannot be SROA'd.
110      bool isUnsafe : 1;
111
112      /// isMemCpySrc - This is true if this aggregate is memcpy'd from.
113      bool isMemCpySrc : 1;
114
115      /// isMemCpyDst - This is true if this aggregate is memcpy'd into.
116      bool isMemCpyDst : 1;
117
118      /// hasSubelementAccess - This is true if a subelement of the alloca is
119      /// ever accessed, or false if the alloca is only accessed with mem
120      /// intrinsics or load/store that only access the entire alloca at once.
121      bool hasSubelementAccess : 1;
122
123      /// hasALoadOrStore - This is true if there are any loads or stores to it.
124      /// The alloca may just be accessed with memcpy, for example, which would
125      /// not set this.
126      bool hasALoadOrStore : 1;
127
128      explicit AllocaInfo(AllocaInst *ai)
129        : AI(ai), isUnsafe(false), isMemCpySrc(false), isMemCpyDst(false),
130          hasSubelementAccess(false), hasALoadOrStore(false) {}
131    };
132
133    /// SRThreshold - The maximum alloca size to considered for SROA.
134    unsigned SRThreshold;
135
136    /// StructMemberThreshold - The maximum number of members a struct can
137    /// contain to be considered for SROA.
138    unsigned StructMemberThreshold;
139
140    /// ArrayElementThreshold - The maximum number of elements an array can
141    /// have to be considered for SROA.
142    unsigned ArrayElementThreshold;
143
144    /// ScalarLoadThreshold - The maximum size in bits of scalars to load when
145    /// converting to scalar
146    unsigned ScalarLoadThreshold;
147
148    void MarkUnsafe(AllocaInfo &I, Instruction *User) {
149      I.isUnsafe = true;
150      DEBUG(dbgs() << "  Transformation preventing inst: " << *User << '\n');
151    }
152
153    bool isSafeAllocaToScalarRepl(AllocaInst *AI);
154
155    void isSafeForScalarRepl(Instruction *I, uint64_t Offset, AllocaInfo &Info);
156    void isSafePHISelectUseForScalarRepl(Instruction *User, uint64_t Offset,
157                                         AllocaInfo &Info);
158    void isSafeGEP(GetElementPtrInst *GEPI, uint64_t &Offset, AllocaInfo &Info);
159    void isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
160                         Type *MemOpType, bool isStore, AllocaInfo &Info,
161                         Instruction *TheAccess, bool AllowWholeAccess);
162    bool TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size,
163                          const DataLayout &DL);
164    uint64_t FindElementAndOffset(Type *&T, uint64_t &Offset, Type *&IdxTy,
165                                  const DataLayout &DL);
166
167    void DoScalarReplacement(AllocaInst *AI,
168                             std::vector<AllocaInst*> &WorkList);
169    void DeleteDeadInstructions();
170
171    void RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
172                              SmallVectorImpl<AllocaInst *> &NewElts);
173    void RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
174                        SmallVectorImpl<AllocaInst *> &NewElts);
175    void RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
176                    SmallVectorImpl<AllocaInst *> &NewElts);
177    void RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
178                                  uint64_t Offset,
179                                  SmallVectorImpl<AllocaInst *> &NewElts);
180    void RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
181                                      AllocaInst *AI,
182                                      SmallVectorImpl<AllocaInst *> &NewElts);
183    void RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
184                                       SmallVectorImpl<AllocaInst *> &NewElts);
185    void RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
186                                      SmallVectorImpl<AllocaInst *> &NewElts);
187    bool ShouldAttemptScalarRepl(AllocaInst *AI);
188  };
189
190  // SROA_DT - SROA that uses DominatorTree.
191  struct SROA_DT : public SROA {
192    static char ID;
193  public:
194    SROA_DT(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
195        SROA(T, true, ID, ST, AT, SLT) {
196      initializeSROA_DTPass(*PassRegistry::getPassRegistry());
197    }
198
199    // getAnalysisUsage - This pass does not require any passes, but we know it
200    // will not alter the CFG, so say so.
201    void getAnalysisUsage(AnalysisUsage &AU) const override {
202      AU.addRequired<AssumptionCacheTracker>();
203      AU.addRequired<DominatorTreeWrapperPass>();
204      AU.setPreservesCFG();
205    }
206  };
207
208  // SROA_SSAUp - SROA that uses SSAUpdater.
209  struct SROA_SSAUp : public SROA {
210    static char ID;
211  public:
212    SROA_SSAUp(int T = -1, int ST = -1, int AT = -1, int SLT = -1) :
213        SROA(T, false, ID, ST, AT, SLT) {
214      initializeSROA_SSAUpPass(*PassRegistry::getPassRegistry());
215    }
216
217    // getAnalysisUsage - This pass does not require any passes, but we know it
218    // will not alter the CFG, so say so.
219    void getAnalysisUsage(AnalysisUsage &AU) const override {
220      AU.addRequired<AssumptionCacheTracker>();
221      AU.setPreservesCFG();
222    }
223  };
224
225}
226
227char SROA_DT::ID = 0;
228char SROA_SSAUp::ID = 0;
229
230INITIALIZE_PASS_BEGIN(SROA_DT, "scalarrepl",
231                "Scalar Replacement of Aggregates (DT)", false, false)
232INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
233INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
234INITIALIZE_PASS_END(SROA_DT, "scalarrepl",
235                "Scalar Replacement of Aggregates (DT)", false, false)
236
237INITIALIZE_PASS_BEGIN(SROA_SSAUp, "scalarrepl-ssa",
238                      "Scalar Replacement of Aggregates (SSAUp)", false, false)
239INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
240INITIALIZE_PASS_END(SROA_SSAUp, "scalarrepl-ssa",
241                    "Scalar Replacement of Aggregates (SSAUp)", false, false)
242
243// Public interface to the ScalarReplAggregates pass
244FunctionPass *llvm::createScalarReplAggregatesPass(int Threshold,
245                                                   bool UseDomTree,
246                                                   int StructMemberThreshold,
247                                                   int ArrayElementThreshold,
248                                                   int ScalarLoadThreshold) {
249  if (UseDomTree)
250    return new SROA_DT(Threshold, StructMemberThreshold, ArrayElementThreshold,
251                       ScalarLoadThreshold);
252  return new SROA_SSAUp(Threshold, StructMemberThreshold,
253                        ArrayElementThreshold, ScalarLoadThreshold);
254}
255
256
257//===----------------------------------------------------------------------===//
258// Convert To Scalar Optimization.
259//===----------------------------------------------------------------------===//
260
261namespace {
262/// ConvertToScalarInfo - This class implements the "Convert To Scalar"
263/// optimization, which scans the uses of an alloca and determines if it can
264/// rewrite it in terms of a single new alloca that can be mem2reg'd.
265class ConvertToScalarInfo {
266  /// AllocaSize - The size of the alloca being considered in bytes.
267  unsigned AllocaSize;
268  const DataLayout &DL;
269  unsigned ScalarLoadThreshold;
270
271  /// IsNotTrivial - This is set to true if there is some access to the object
272  /// which means that mem2reg can't promote it.
273  bool IsNotTrivial;
274
275  /// ScalarKind - Tracks the kind of alloca being considered for promotion,
276  /// computed based on the uses of the alloca rather than the LLVM type system.
277  enum {
278    Unknown,
279
280    // Accesses via GEPs that are consistent with element access of a vector
281    // type. This will not be converted into a vector unless there is a later
282    // access using an actual vector type.
283    ImplicitVector,
284
285    // Accesses via vector operations and GEPs that are consistent with the
286    // layout of a vector type.
287    Vector,
288
289    // An integer bag-of-bits with bitwise operations for insertion and
290    // extraction. Any combination of types can be converted into this kind
291    // of scalar.
292    Integer
293  } ScalarKind;
294
295  /// VectorTy - This tracks the type that we should promote the vector to if
296  /// it is possible to turn it into a vector.  This starts out null, and if it
297  /// isn't possible to turn into a vector type, it gets set to VoidTy.
298  VectorType *VectorTy;
299
300  /// HadNonMemTransferAccess - True if there is at least one access to the
301  /// alloca that is not a MemTransferInst.  We don't want to turn structs into
302  /// large integers unless there is some potential for optimization.
303  bool HadNonMemTransferAccess;
304
305  /// HadDynamicAccess - True if some element of this alloca was dynamic.
306  /// We don't yet have support for turning a dynamic access into a large
307  /// integer.
308  bool HadDynamicAccess;
309
310public:
311  explicit ConvertToScalarInfo(unsigned Size, const DataLayout &DL,
312                               unsigned SLT)
313    : AllocaSize(Size), DL(DL), ScalarLoadThreshold(SLT), IsNotTrivial(false),
314    ScalarKind(Unknown), VectorTy(nullptr), HadNonMemTransferAccess(false),
315    HadDynamicAccess(false) { }
316
317  AllocaInst *TryConvert(AllocaInst *AI);
318
319private:
320  bool CanConvertToScalar(Value *V, uint64_t Offset, Value* NonConstantIdx);
321  void MergeInTypeForLoadOrStore(Type *In, uint64_t Offset);
322  bool MergeInVectorType(VectorType *VInTy, uint64_t Offset);
323  void ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI, uint64_t Offset,
324                           Value *NonConstantIdx);
325
326  Value *ConvertScalar_ExtractValue(Value *NV, Type *ToType,
327                                    uint64_t Offset, Value* NonConstantIdx,
328                                    IRBuilder<> &Builder);
329  Value *ConvertScalar_InsertValue(Value *StoredVal, Value *ExistingVal,
330                                   uint64_t Offset, Value* NonConstantIdx,
331                                   IRBuilder<> &Builder);
332};
333} // end anonymous namespace.
334
335
336/// TryConvert - Analyze the specified alloca, and if it is safe to do so,
337/// rewrite it to be a new alloca which is mem2reg'able.  This returns the new
338/// alloca if possible or null if not.
339AllocaInst *ConvertToScalarInfo::TryConvert(AllocaInst *AI) {
340  // If we can't convert this scalar, or if mem2reg can trivially do it, bail
341  // out.
342  if (!CanConvertToScalar(AI, 0, nullptr) || !IsNotTrivial)
343    return nullptr;
344
345  // If an alloca has only memset / memcpy uses, it may still have an Unknown
346  // ScalarKind. Treat it as an Integer below.
347  if (ScalarKind == Unknown)
348    ScalarKind = Integer;
349
350  if (ScalarKind == Vector && VectorTy->getBitWidth() != AllocaSize * 8)
351    ScalarKind = Integer;
352
353  // If we were able to find a vector type that can handle this with
354  // insert/extract elements, and if there was at least one use that had
355  // a vector type, promote this to a vector.  We don't want to promote
356  // random stuff that doesn't use vectors (e.g. <9 x double>) because then
357  // we just get a lot of insert/extracts.  If at least one vector is
358  // involved, then we probably really do have a union of vector/array.
359  Type *NewTy;
360  if (ScalarKind == Vector) {
361    assert(VectorTy && "Missing type for vector scalar.");
362    DEBUG(dbgs() << "CONVERT TO VECTOR: " << *AI << "\n  TYPE = "
363          << *VectorTy << '\n');
364    NewTy = VectorTy;  // Use the vector type.
365  } else {
366    unsigned BitWidth = AllocaSize * 8;
367
368    // Do not convert to scalar integer if the alloca size exceeds the
369    // scalar load threshold.
370    if (BitWidth > ScalarLoadThreshold)
371      return nullptr;
372
373    if ((ScalarKind == ImplicitVector || ScalarKind == Integer) &&
374        !HadNonMemTransferAccess && !DL.fitsInLegalInteger(BitWidth))
375      return nullptr;
376    // Dynamic accesses on integers aren't yet supported.  They need us to shift
377    // by a dynamic amount which could be difficult to work out as we might not
378    // know whether to use a left or right shift.
379    if (ScalarKind == Integer && HadDynamicAccess)
380      return nullptr;
381
382    DEBUG(dbgs() << "CONVERT TO SCALAR INTEGER: " << *AI << "\n");
383    // Create and insert the integer alloca.
384    NewTy = IntegerType::get(AI->getContext(), BitWidth);
385  }
386  AllocaInst *NewAI =
387      new AllocaInst(NewTy, nullptr, "", &AI->getParent()->front());
388  ConvertUsesToScalar(AI, NewAI, 0, nullptr);
389  return NewAI;
390}
391
392/// MergeInTypeForLoadOrStore - Add the 'In' type to the accumulated vector type
393/// (VectorTy) so far at the offset specified by Offset (which is specified in
394/// bytes).
395///
396/// There are two cases we handle here:
397///   1) A union of vector types of the same size and potentially its elements.
398///      Here we turn element accesses into insert/extract element operations.
399///      This promotes a <4 x float> with a store of float to the third element
400///      into a <4 x float> that uses insert element.
401///   2) A fully general blob of memory, which we turn into some (potentially
402///      large) integer type with extract and insert operations where the loads
403///      and stores would mutate the memory.  We mark this by setting VectorTy
404///      to VoidTy.
405void ConvertToScalarInfo::MergeInTypeForLoadOrStore(Type *In,
406                                                    uint64_t Offset) {
407  // If we already decided to turn this into a blob of integer memory, there is
408  // nothing to be done.
409  if (ScalarKind == Integer)
410    return;
411
412  // If this could be contributing to a vector, analyze it.
413
414  // If the In type is a vector that is the same size as the alloca, see if it
415  // matches the existing VecTy.
416  if (VectorType *VInTy = dyn_cast<VectorType>(In)) {
417    if (MergeInVectorType(VInTy, Offset))
418      return;
419  } else if (In->isFloatTy() || In->isDoubleTy() ||
420             (In->isIntegerTy() && In->getPrimitiveSizeInBits() >= 8 &&
421              isPowerOf2_32(In->getPrimitiveSizeInBits()))) {
422    // Full width accesses can be ignored, because they can always be turned
423    // into bitcasts.
424    unsigned EltSize = In->getPrimitiveSizeInBits()/8;
425    if (EltSize == AllocaSize)
426      return;
427
428    // If we're accessing something that could be an element of a vector, see
429    // if the implied vector agrees with what we already have and if Offset is
430    // compatible with it.
431    if (Offset % EltSize == 0 && AllocaSize % EltSize == 0 &&
432        (!VectorTy || EltSize == VectorTy->getElementType()
433                                         ->getPrimitiveSizeInBits()/8)) {
434      if (!VectorTy) {
435        ScalarKind = ImplicitVector;
436        VectorTy = VectorType::get(In, AllocaSize/EltSize);
437      }
438      return;
439    }
440  }
441
442  // Otherwise, we have a case that we can't handle with an optimized vector
443  // form.  We can still turn this into a large integer.
444  ScalarKind = Integer;
445}
446
447/// MergeInVectorType - Handles the vector case of MergeInTypeForLoadOrStore,
448/// returning true if the type was successfully merged and false otherwise.
449bool ConvertToScalarInfo::MergeInVectorType(VectorType *VInTy,
450                                            uint64_t Offset) {
451  if (VInTy->getBitWidth()/8 == AllocaSize && Offset == 0) {
452    // If we're storing/loading a vector of the right size, allow it as a
453    // vector.  If this the first vector we see, remember the type so that
454    // we know the element size. If this is a subsequent access, ignore it
455    // even if it is a differing type but the same size. Worst case we can
456    // bitcast the resultant vectors.
457    if (!VectorTy)
458      VectorTy = VInTy;
459    ScalarKind = Vector;
460    return true;
461  }
462
463  return false;
464}
465
466/// CanConvertToScalar - V is a pointer.  If we can convert the pointee and all
467/// its accesses to a single vector type, return true and set VecTy to
468/// the new type.  If we could convert the alloca into a single promotable
469/// integer, return true but set VecTy to VoidTy.  Further, if the use is not a
470/// completely trivial use that mem2reg could promote, set IsNotTrivial.  Offset
471/// is the current offset from the base of the alloca being analyzed.
472///
473/// If we see at least one access to the value that is as a vector type, set the
474/// SawVec flag.
475bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset,
476                                             Value* NonConstantIdx) {
477  for (User *U : V->users()) {
478    Instruction *UI = cast<Instruction>(U);
479
480    if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
481      // Don't break volatile loads.
482      if (!LI->isSimple())
483        return false;
484      // Don't touch MMX operations.
485      if (LI->getType()->isX86_MMXTy())
486        return false;
487      HadNonMemTransferAccess = true;
488      MergeInTypeForLoadOrStore(LI->getType(), Offset);
489      continue;
490    }
491
492    if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
493      // Storing the pointer, not into the value?
494      if (SI->getOperand(0) == V || !SI->isSimple()) return false;
495      // Don't touch MMX operations.
496      if (SI->getOperand(0)->getType()->isX86_MMXTy())
497        return false;
498      HadNonMemTransferAccess = true;
499      MergeInTypeForLoadOrStore(SI->getOperand(0)->getType(), Offset);
500      continue;
501    }
502
503    if (BitCastInst *BCI = dyn_cast<BitCastInst>(UI)) {
504      if (!onlyUsedByLifetimeMarkers(BCI))
505        IsNotTrivial = true;  // Can't be mem2reg'd.
506      if (!CanConvertToScalar(BCI, Offset, NonConstantIdx))
507        return false;
508      continue;
509    }
510
511    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(UI)) {
512      // If this is a GEP with a variable indices, we can't handle it.
513      PointerType* PtrTy = dyn_cast<PointerType>(GEP->getPointerOperandType());
514      if (!PtrTy)
515        return false;
516
517      // Compute the offset that this GEP adds to the pointer.
518      SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
519      Value *GEPNonConstantIdx = nullptr;
520      if (!GEP->hasAllConstantIndices()) {
521        if (!isa<VectorType>(PtrTy->getElementType()))
522          return false;
523        if (NonConstantIdx)
524          return false;
525        GEPNonConstantIdx = Indices.pop_back_val();
526        if (!GEPNonConstantIdx->getType()->isIntegerTy(32))
527          return false;
528        HadDynamicAccess = true;
529      } else
530        GEPNonConstantIdx = NonConstantIdx;
531      uint64_t GEPOffset = DL.getIndexedOffset(PtrTy,
532                                               Indices);
533      // See if all uses can be converted.
534      if (!CanConvertToScalar(GEP, Offset+GEPOffset, GEPNonConstantIdx))
535        return false;
536      IsNotTrivial = true;  // Can't be mem2reg'd.
537      HadNonMemTransferAccess = true;
538      continue;
539    }
540
541    // If this is a constant sized memset of a constant value (e.g. 0) we can
542    // handle it.
543    if (MemSetInst *MSI = dyn_cast<MemSetInst>(UI)) {
544      // Store to dynamic index.
545      if (NonConstantIdx)
546        return false;
547      // Store of constant value.
548      if (!isa<ConstantInt>(MSI->getValue()))
549        return false;
550
551      // Store of constant size.
552      ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
553      if (!Len)
554        return false;
555
556      // If the size differs from the alloca, we can only convert the alloca to
557      // an integer bag-of-bits.
558      // FIXME: This should handle all of the cases that are currently accepted
559      // as vector element insertions.
560      if (Len->getZExtValue() != AllocaSize || Offset != 0)
561        ScalarKind = Integer;
562
563      IsNotTrivial = true;  // Can't be mem2reg'd.
564      HadNonMemTransferAccess = true;
565      continue;
566    }
567
568    // If this is a memcpy or memmove into or out of the whole allocation, we
569    // can handle it like a load or store of the scalar type.
570    if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(UI)) {
571      // Store to dynamic index.
572      if (NonConstantIdx)
573        return false;
574      ConstantInt *Len = dyn_cast<ConstantInt>(MTI->getLength());
575      if (!Len || Len->getZExtValue() != AllocaSize || Offset != 0)
576        return false;
577
578      IsNotTrivial = true;  // Can't be mem2reg'd.
579      continue;
580    }
581
582    // If this is a lifetime intrinsic, we can handle it.
583    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(UI)) {
584      if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
585          II->getIntrinsicID() == Intrinsic::lifetime_end) {
586        continue;
587      }
588    }
589
590    // Otherwise, we cannot handle this!
591    return false;
592  }
593
594  return true;
595}
596
597/// ConvertUsesToScalar - Convert all of the users of Ptr to use the new alloca
598/// directly.  This happens when we are converting an "integer union" to a
599/// single integer scalar, or when we are converting a "vector union" to a
600/// vector with insert/extractelement instructions.
601///
602/// Offset is an offset from the original alloca, in bits that need to be
603/// shifted to the right.  By the end of this, there should be no uses of Ptr.
604void ConvertToScalarInfo::ConvertUsesToScalar(Value *Ptr, AllocaInst *NewAI,
605                                              uint64_t Offset,
606                                              Value* NonConstantIdx) {
607  while (!Ptr->use_empty()) {
608    Instruction *User = cast<Instruction>(Ptr->user_back());
609
610    if (BitCastInst *CI = dyn_cast<BitCastInst>(User)) {
611      ConvertUsesToScalar(CI, NewAI, Offset, NonConstantIdx);
612      CI->eraseFromParent();
613      continue;
614    }
615
616    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(User)) {
617      // Compute the offset that this GEP adds to the pointer.
618      SmallVector<Value*, 8> Indices(GEP->op_begin()+1, GEP->op_end());
619      Value* GEPNonConstantIdx = nullptr;
620      if (!GEP->hasAllConstantIndices()) {
621        assert(!NonConstantIdx &&
622               "Dynamic GEP reading from dynamic GEP unsupported");
623        GEPNonConstantIdx = Indices.pop_back_val();
624      } else
625        GEPNonConstantIdx = NonConstantIdx;
626      uint64_t GEPOffset = DL.getIndexedOffset(GEP->getPointerOperandType(),
627                                               Indices);
628      ConvertUsesToScalar(GEP, NewAI, Offset+GEPOffset*8, GEPNonConstantIdx);
629      GEP->eraseFromParent();
630      continue;
631    }
632
633    IRBuilder<> Builder(User);
634
635    if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
636      // The load is a bit extract from NewAI shifted right by Offset bits.
637      Value *LoadedVal = Builder.CreateLoad(NewAI);
638      Value *NewLoadVal
639        = ConvertScalar_ExtractValue(LoadedVal, LI->getType(), Offset,
640                                     NonConstantIdx, Builder);
641      LI->replaceAllUsesWith(NewLoadVal);
642      LI->eraseFromParent();
643      continue;
644    }
645
646    if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
647      assert(SI->getOperand(0) != Ptr && "Consistency error!");
648      Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
649      Value *New = ConvertScalar_InsertValue(SI->getOperand(0), Old, Offset,
650                                             NonConstantIdx, Builder);
651      Builder.CreateStore(New, NewAI);
652      SI->eraseFromParent();
653
654      // If the load we just inserted is now dead, then the inserted store
655      // overwrote the entire thing.
656      if (Old->use_empty())
657        Old->eraseFromParent();
658      continue;
659    }
660
661    // If this is a constant sized memset of a constant value (e.g. 0) we can
662    // transform it into a store of the expanded constant value.
663    if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
664      assert(MSI->getRawDest() == Ptr && "Consistency error!");
665      assert(!NonConstantIdx && "Cannot replace dynamic memset with insert");
666      int64_t SNumBytes = cast<ConstantInt>(MSI->getLength())->getSExtValue();
667      if (SNumBytes > 0 && (SNumBytes >> 32) == 0) {
668        unsigned NumBytes = static_cast<unsigned>(SNumBytes);
669        unsigned Val = cast<ConstantInt>(MSI->getValue())->getZExtValue();
670
671        // Compute the value replicated the right number of times.
672        APInt APVal(NumBytes*8, Val);
673
674        // Splat the value if non-zero.
675        if (Val)
676          for (unsigned i = 1; i != NumBytes; ++i)
677            APVal |= APVal << 8;
678
679        Instruction *Old = Builder.CreateLoad(NewAI, NewAI->getName()+".in");
680        Value *New = ConvertScalar_InsertValue(
681                                    ConstantInt::get(User->getContext(), APVal),
682                                               Old, Offset, nullptr, Builder);
683        Builder.CreateStore(New, NewAI);
684
685        // If the load we just inserted is now dead, then the memset overwrote
686        // the entire thing.
687        if (Old->use_empty())
688          Old->eraseFromParent();
689      }
690      MSI->eraseFromParent();
691      continue;
692    }
693
694    // If this is a memcpy or memmove into or out of the whole allocation, we
695    // can handle it like a load or store of the scalar type.
696    if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(User)) {
697      assert(Offset == 0 && "must be store to start of alloca");
698      assert(!NonConstantIdx && "Cannot replace dynamic transfer with insert");
699
700      // If the source and destination are both to the same alloca, then this is
701      // a noop copy-to-self, just delete it.  Otherwise, emit a load and store
702      // as appropriate.
703      AllocaInst *OrigAI = cast<AllocaInst>(GetUnderlyingObject(Ptr, DL, 0));
704
705      if (GetUnderlyingObject(MTI->getSource(), DL, 0) != OrigAI) {
706        // Dest must be OrigAI, change this to be a load from the original
707        // pointer (bitcasted), then a store to our new alloca.
708        assert(MTI->getRawDest() == Ptr && "Neither use is of pointer?");
709        Value *SrcPtr = MTI->getSource();
710        PointerType* SPTy = cast<PointerType>(SrcPtr->getType());
711        PointerType* AIPTy = cast<PointerType>(NewAI->getType());
712        if (SPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
713          AIPTy = PointerType::get(AIPTy->getElementType(),
714                                   SPTy->getAddressSpace());
715        }
716        SrcPtr = Builder.CreateBitCast(SrcPtr, AIPTy);
717
718        LoadInst *SrcVal = Builder.CreateLoad(SrcPtr, "srcval");
719        SrcVal->setAlignment(MTI->getAlignment());
720        Builder.CreateStore(SrcVal, NewAI);
721      } else if (GetUnderlyingObject(MTI->getDest(), DL, 0) != OrigAI) {
722        // Src must be OrigAI, change this to be a load from NewAI then a store
723        // through the original dest pointer (bitcasted).
724        assert(MTI->getRawSource() == Ptr && "Neither use is of pointer?");
725        LoadInst *SrcVal = Builder.CreateLoad(NewAI, "srcval");
726
727        PointerType* DPTy = cast<PointerType>(MTI->getDest()->getType());
728        PointerType* AIPTy = cast<PointerType>(NewAI->getType());
729        if (DPTy->getAddressSpace() != AIPTy->getAddressSpace()) {
730          AIPTy = PointerType::get(AIPTy->getElementType(),
731                                   DPTy->getAddressSpace());
732        }
733        Value *DstPtr = Builder.CreateBitCast(MTI->getDest(), AIPTy);
734
735        StoreInst *NewStore = Builder.CreateStore(SrcVal, DstPtr);
736        NewStore->setAlignment(MTI->getAlignment());
737      } else {
738        // Noop transfer. Src == Dst
739      }
740
741      MTI->eraseFromParent();
742      continue;
743    }
744
745    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
746      if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
747          II->getIntrinsicID() == Intrinsic::lifetime_end) {
748        // There's no need to preserve these, as the resulting alloca will be
749        // converted to a register anyways.
750        II->eraseFromParent();
751        continue;
752      }
753    }
754
755    llvm_unreachable("Unsupported operation!");
756  }
757}
758
759/// ConvertScalar_ExtractValue - Extract a value of type ToType from an integer
760/// or vector value FromVal, extracting the bits from the offset specified by
761/// Offset.  This returns the value, which is of type ToType.
762///
763/// This happens when we are converting an "integer union" to a single
764/// integer scalar, or when we are converting a "vector union" to a vector with
765/// insert/extractelement instructions.
766///
767/// Offset is an offset from the original alloca, in bits that need to be
768/// shifted to the right.
769Value *ConvertToScalarInfo::
770ConvertScalar_ExtractValue(Value *FromVal, Type *ToType,
771                           uint64_t Offset, Value* NonConstantIdx,
772                           IRBuilder<> &Builder) {
773  // If the load is of the whole new alloca, no conversion is needed.
774  Type *FromType = FromVal->getType();
775  if (FromType == ToType && Offset == 0)
776    return FromVal;
777
778  // If the result alloca is a vector type, this is either an element
779  // access or a bitcast to another vector type of the same size.
780  if (VectorType *VTy = dyn_cast<VectorType>(FromType)) {
781    unsigned FromTypeSize = DL.getTypeAllocSize(FromType);
782    unsigned ToTypeSize = DL.getTypeAllocSize(ToType);
783    if (FromTypeSize == ToTypeSize)
784        return Builder.CreateBitCast(FromVal, ToType);
785
786    // Otherwise it must be an element access.
787    unsigned Elt = 0;
788    if (Offset) {
789      unsigned EltSize = DL.getTypeAllocSizeInBits(VTy->getElementType());
790      Elt = Offset/EltSize;
791      assert(EltSize*Elt == Offset && "Invalid modulus in validity checking");
792    }
793    // Return the element extracted out of it.
794    Value *Idx;
795    if (NonConstantIdx) {
796      if (Elt)
797        Idx = Builder.CreateAdd(NonConstantIdx,
798                                Builder.getInt32(Elt),
799                                "dyn.offset");
800      else
801        Idx = NonConstantIdx;
802    } else
803      Idx = Builder.getInt32(Elt);
804    Value *V = Builder.CreateExtractElement(FromVal, Idx);
805    if (V->getType() != ToType)
806      V = Builder.CreateBitCast(V, ToType);
807    return V;
808  }
809
810  // If ToType is a first class aggregate, extract out each of the pieces and
811  // use insertvalue's to form the FCA.
812  if (StructType *ST = dyn_cast<StructType>(ToType)) {
813    assert(!NonConstantIdx &&
814           "Dynamic indexing into struct types not supported");
815    const StructLayout &Layout = *DL.getStructLayout(ST);
816    Value *Res = UndefValue::get(ST);
817    for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
818      Value *Elt = ConvertScalar_ExtractValue(FromVal, ST->getElementType(i),
819                                        Offset+Layout.getElementOffsetInBits(i),
820                                              nullptr, Builder);
821      Res = Builder.CreateInsertValue(Res, Elt, i);
822    }
823    return Res;
824  }
825
826  if (ArrayType *AT = dyn_cast<ArrayType>(ToType)) {
827    assert(!NonConstantIdx &&
828           "Dynamic indexing into array types not supported");
829    uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
830    Value *Res = UndefValue::get(AT);
831    for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
832      Value *Elt = ConvertScalar_ExtractValue(FromVal, AT->getElementType(),
833                                              Offset+i*EltSize, nullptr,
834                                              Builder);
835      Res = Builder.CreateInsertValue(Res, Elt, i);
836    }
837    return Res;
838  }
839
840  // Otherwise, this must be a union that was converted to an integer value.
841  IntegerType *NTy = cast<IntegerType>(FromVal->getType());
842
843  // If this is a big-endian system and the load is narrower than the
844  // full alloca type, we need to do a shift to get the right bits.
845  int ShAmt = 0;
846  if (DL.isBigEndian()) {
847    // On big-endian machines, the lowest bit is stored at the bit offset
848    // from the pointer given by getTypeStoreSizeInBits.  This matters for
849    // integers with a bitwidth that is not a multiple of 8.
850    ShAmt = DL.getTypeStoreSizeInBits(NTy) -
851            DL.getTypeStoreSizeInBits(ToType) - Offset;
852  } else {
853    ShAmt = Offset;
854  }
855
856  // Note: we support negative bitwidths (with shl) which are not defined.
857  // We do this to support (f.e.) loads off the end of a structure where
858  // only some bits are used.
859  if (ShAmt > 0 && (unsigned)ShAmt < NTy->getBitWidth())
860    FromVal = Builder.CreateLShr(FromVal,
861                                 ConstantInt::get(FromVal->getType(), ShAmt));
862  else if (ShAmt < 0 && (unsigned)-ShAmt < NTy->getBitWidth())
863    FromVal = Builder.CreateShl(FromVal,
864                                ConstantInt::get(FromVal->getType(), -ShAmt));
865
866  // Finally, unconditionally truncate the integer to the right width.
867  unsigned LIBitWidth = DL.getTypeSizeInBits(ToType);
868  if (LIBitWidth < NTy->getBitWidth())
869    FromVal =
870      Builder.CreateTrunc(FromVal, IntegerType::get(FromVal->getContext(),
871                                                    LIBitWidth));
872  else if (LIBitWidth > NTy->getBitWidth())
873    FromVal =
874       Builder.CreateZExt(FromVal, IntegerType::get(FromVal->getContext(),
875                                                    LIBitWidth));
876
877  // If the result is an integer, this is a trunc or bitcast.
878  if (ToType->isIntegerTy()) {
879    // Should be done.
880  } else if (ToType->isFloatingPointTy() || ToType->isVectorTy()) {
881    // Just do a bitcast, we know the sizes match up.
882    FromVal = Builder.CreateBitCast(FromVal, ToType);
883  } else {
884    // Otherwise must be a pointer.
885    FromVal = Builder.CreateIntToPtr(FromVal, ToType);
886  }
887  assert(FromVal->getType() == ToType && "Didn't convert right?");
888  return FromVal;
889}
890
891/// ConvertScalar_InsertValue - Insert the value "SV" into the existing integer
892/// or vector value "Old" at the offset specified by Offset.
893///
894/// This happens when we are converting an "integer union" to a
895/// single integer scalar, or when we are converting a "vector union" to a
896/// vector with insert/extractelement instructions.
897///
898/// Offset is an offset from the original alloca, in bits that need to be
899/// shifted to the right.
900///
901/// NonConstantIdx is an index value if there was a GEP with a non-constant
902/// index value.  If this is 0 then all GEPs used to find this insert address
903/// are constant.
904Value *ConvertToScalarInfo::
905ConvertScalar_InsertValue(Value *SV, Value *Old,
906                          uint64_t Offset, Value* NonConstantIdx,
907                          IRBuilder<> &Builder) {
908  // Convert the stored type to the actual type, shift it left to insert
909  // then 'or' into place.
910  Type *AllocaType = Old->getType();
911  LLVMContext &Context = Old->getContext();
912
913  if (VectorType *VTy = dyn_cast<VectorType>(AllocaType)) {
914    uint64_t VecSize = DL.getTypeAllocSizeInBits(VTy);
915    uint64_t ValSize = DL.getTypeAllocSizeInBits(SV->getType());
916
917    // Changing the whole vector with memset or with an access of a different
918    // vector type?
919    if (ValSize == VecSize)
920        return Builder.CreateBitCast(SV, AllocaType);
921
922    // Must be an element insertion.
923    Type *EltTy = VTy->getElementType();
924    if (SV->getType() != EltTy)
925      SV = Builder.CreateBitCast(SV, EltTy);
926    uint64_t EltSize = DL.getTypeAllocSizeInBits(EltTy);
927    unsigned Elt = Offset/EltSize;
928    Value *Idx;
929    if (NonConstantIdx) {
930      if (Elt)
931        Idx = Builder.CreateAdd(NonConstantIdx,
932                                Builder.getInt32(Elt),
933                                "dyn.offset");
934      else
935        Idx = NonConstantIdx;
936    } else
937      Idx = Builder.getInt32(Elt);
938    return Builder.CreateInsertElement(Old, SV, Idx);
939  }
940
941  // If SV is a first-class aggregate value, insert each value recursively.
942  if (StructType *ST = dyn_cast<StructType>(SV->getType())) {
943    assert(!NonConstantIdx &&
944           "Dynamic indexing into struct types not supported");
945    const StructLayout &Layout = *DL.getStructLayout(ST);
946    for (unsigned i = 0, e = ST->getNumElements(); i != e; ++i) {
947      Value *Elt = Builder.CreateExtractValue(SV, i);
948      Old = ConvertScalar_InsertValue(Elt, Old,
949                                      Offset+Layout.getElementOffsetInBits(i),
950                                      nullptr, Builder);
951    }
952    return Old;
953  }
954
955  if (ArrayType *AT = dyn_cast<ArrayType>(SV->getType())) {
956    assert(!NonConstantIdx &&
957           "Dynamic indexing into array types not supported");
958    uint64_t EltSize = DL.getTypeAllocSizeInBits(AT->getElementType());
959    for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
960      Value *Elt = Builder.CreateExtractValue(SV, i);
961      Old = ConvertScalar_InsertValue(Elt, Old, Offset+i*EltSize, nullptr,
962                                      Builder);
963    }
964    return Old;
965  }
966
967  // If SV is a float, convert it to the appropriate integer type.
968  // If it is a pointer, do the same.
969  unsigned SrcWidth = DL.getTypeSizeInBits(SV->getType());
970  unsigned DestWidth = DL.getTypeSizeInBits(AllocaType);
971  unsigned SrcStoreWidth = DL.getTypeStoreSizeInBits(SV->getType());
972  unsigned DestStoreWidth = DL.getTypeStoreSizeInBits(AllocaType);
973  if (SV->getType()->isFloatingPointTy() || SV->getType()->isVectorTy())
974    SV = Builder.CreateBitCast(SV, IntegerType::get(SV->getContext(),SrcWidth));
975  else if (SV->getType()->isPointerTy())
976    SV = Builder.CreatePtrToInt(SV, DL.getIntPtrType(SV->getType()));
977
978  // Zero extend or truncate the value if needed.
979  if (SV->getType() != AllocaType) {
980    if (SV->getType()->getPrimitiveSizeInBits() <
981             AllocaType->getPrimitiveSizeInBits())
982      SV = Builder.CreateZExt(SV, AllocaType);
983    else {
984      // Truncation may be needed if storing more than the alloca can hold
985      // (undefined behavior).
986      SV = Builder.CreateTrunc(SV, AllocaType);
987      SrcWidth = DestWidth;
988      SrcStoreWidth = DestStoreWidth;
989    }
990  }
991
992  // If this is a big-endian system and the store is narrower than the
993  // full alloca type, we need to do a shift to get the right bits.
994  int ShAmt = 0;
995  if (DL.isBigEndian()) {
996    // On big-endian machines, the lowest bit is stored at the bit offset
997    // from the pointer given by getTypeStoreSizeInBits.  This matters for
998    // integers with a bitwidth that is not a multiple of 8.
999    ShAmt = DestStoreWidth - SrcStoreWidth - Offset;
1000  } else {
1001    ShAmt = Offset;
1002  }
1003
1004  // Note: we support negative bitwidths (with shr) which are not defined.
1005  // We do this to support (f.e.) stores off the end of a structure where
1006  // only some bits in the structure are set.
1007  APInt Mask(APInt::getLowBitsSet(DestWidth, SrcWidth));
1008  if (ShAmt > 0 && (unsigned)ShAmt < DestWidth) {
1009    SV = Builder.CreateShl(SV, ConstantInt::get(SV->getType(), ShAmt));
1010    Mask <<= ShAmt;
1011  } else if (ShAmt < 0 && (unsigned)-ShAmt < DestWidth) {
1012    SV = Builder.CreateLShr(SV, ConstantInt::get(SV->getType(), -ShAmt));
1013    Mask = Mask.lshr(-ShAmt);
1014  }
1015
1016  // Mask out the bits we are about to insert from the old value, and or
1017  // in the new bits.
1018  if (SrcWidth != DestWidth) {
1019    assert(DestWidth > SrcWidth);
1020    Old = Builder.CreateAnd(Old, ConstantInt::get(Context, ~Mask), "mask");
1021    SV = Builder.CreateOr(Old, SV, "ins");
1022  }
1023  return SV;
1024}
1025
1026
1027//===----------------------------------------------------------------------===//
1028// SRoA Driver
1029//===----------------------------------------------------------------------===//
1030
1031
1032bool SROA::runOnFunction(Function &F) {
1033  if (skipOptnoneFunction(F))
1034    return false;
1035
1036  bool Changed = performPromotion(F);
1037
1038  while (1) {
1039    bool LocalChange = performScalarRepl(F);
1040    if (!LocalChange) break;   // No need to repromote if no scalarrepl
1041    Changed = true;
1042    LocalChange = performPromotion(F);
1043    if (!LocalChange) break;   // No need to re-scalarrepl if no promotion
1044  }
1045
1046  return Changed;
1047}
1048
1049namespace {
1050class AllocaPromoter : public LoadAndStorePromoter {
1051  AllocaInst *AI;
1052  DIBuilder *DIB;
1053  SmallVector<DbgDeclareInst *, 4> DDIs;
1054  SmallVector<DbgValueInst *, 4> DVIs;
1055public:
1056  AllocaPromoter(ArrayRef<Instruction*> Insts, SSAUpdater &S,
1057                 DIBuilder *DB)
1058    : LoadAndStorePromoter(Insts, S), AI(nullptr), DIB(DB) {}
1059
1060  void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
1061    // Remember which alloca we're promoting (for isInstInList).
1062    this->AI = AI;
1063    if (auto *L = LocalAsMetadata::getIfExists(AI)) {
1064      if (auto *DINode = MetadataAsValue::getIfExists(AI->getContext(), L)) {
1065        for (User *U : DINode->users())
1066          if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
1067            DDIs.push_back(DDI);
1068          else if (DbgValueInst *DVI = dyn_cast<DbgValueInst>(U))
1069            DVIs.push_back(DVI);
1070      }
1071    }
1072
1073    LoadAndStorePromoter::run(Insts);
1074    AI->eraseFromParent();
1075    for (SmallVectorImpl<DbgDeclareInst *>::iterator I = DDIs.begin(),
1076           E = DDIs.end(); I != E; ++I) {
1077      DbgDeclareInst *DDI = *I;
1078      DDI->eraseFromParent();
1079    }
1080    for (SmallVectorImpl<DbgValueInst *>::iterator I = DVIs.begin(),
1081           E = DVIs.end(); I != E; ++I) {
1082      DbgValueInst *DVI = *I;
1083      DVI->eraseFromParent();
1084    }
1085  }
1086
1087  bool isInstInList(Instruction *I,
1088                    const SmallVectorImpl<Instruction*> &Insts) const override {
1089    if (LoadInst *LI = dyn_cast<LoadInst>(I))
1090      return LI->getOperand(0) == AI;
1091    return cast<StoreInst>(I)->getPointerOperand() == AI;
1092  }
1093
1094  void updateDebugInfo(Instruction *Inst) const override {
1095    for (SmallVectorImpl<DbgDeclareInst *>::const_iterator I = DDIs.begin(),
1096           E = DDIs.end(); I != E; ++I) {
1097      DbgDeclareInst *DDI = *I;
1098      if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
1099        ConvertDebugDeclareToDebugValue(DDI, SI, *DIB);
1100      else if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
1101        ConvertDebugDeclareToDebugValue(DDI, LI, *DIB);
1102    }
1103    for (SmallVectorImpl<DbgValueInst *>::const_iterator I = DVIs.begin(),
1104           E = DVIs.end(); I != E; ++I) {
1105      DbgValueInst *DVI = *I;
1106      Value *Arg = nullptr;
1107      if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1108        // If an argument is zero extended then use argument directly. The ZExt
1109        // may be zapped by an optimization pass in future.
1110        if (ZExtInst *ZExt = dyn_cast<ZExtInst>(SI->getOperand(0)))
1111          Arg = dyn_cast<Argument>(ZExt->getOperand(0));
1112        if (SExtInst *SExt = dyn_cast<SExtInst>(SI->getOperand(0)))
1113          Arg = dyn_cast<Argument>(SExt->getOperand(0));
1114        if (!Arg)
1115          Arg = SI->getOperand(0);
1116      } else if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
1117        Arg = LI->getOperand(0);
1118      } else {
1119        continue;
1120      }
1121      DIB->insertDbgValueIntrinsic(Arg, 0, DVI->getVariable(),
1122                                   DVI->getExpression(), DVI->getDebugLoc(),
1123                                   Inst);
1124    }
1125  }
1126};
1127} // end anon namespace
1128
1129/// isSafeSelectToSpeculate - Select instructions that use an alloca and are
1130/// subsequently loaded can be rewritten to load both input pointers and then
1131/// select between the result, allowing the load of the alloca to be promoted.
1132/// From this:
1133///   %P2 = select i1 %cond, i32* %Alloca, i32* %Other
1134///   %V = load i32* %P2
1135/// to:
1136///   %V1 = load i32* %Alloca      -> will be mem2reg'd
1137///   %V2 = load i32* %Other
1138///   %V = select i1 %cond, i32 %V1, i32 %V2
1139///
1140/// We can do this to a select if its only uses are loads and if the operand to
1141/// the select can be loaded unconditionally.
1142static bool isSafeSelectToSpeculate(SelectInst *SI) {
1143  const DataLayout &DL = SI->getModule()->getDataLayout();
1144  bool TDerefable = isDereferenceablePointer(SI->getTrueValue(), DL);
1145  bool FDerefable = isDereferenceablePointer(SI->getFalseValue(), DL);
1146
1147  for (User *U : SI->users()) {
1148    LoadInst *LI = dyn_cast<LoadInst>(U);
1149    if (!LI || !LI->isSimple()) return false;
1150
1151    // Both operands to the select need to be dereferencable, either absolutely
1152    // (e.g. allocas) or at this point because we can see other accesses to it.
1153    if (!TDerefable &&
1154        !isSafeToLoadUnconditionally(SI->getTrueValue(), LI,
1155                                     LI->getAlignment()))
1156      return false;
1157    if (!FDerefable &&
1158        !isSafeToLoadUnconditionally(SI->getFalseValue(), LI,
1159                                     LI->getAlignment()))
1160      return false;
1161  }
1162
1163  return true;
1164}
1165
1166/// isSafePHIToSpeculate - PHI instructions that use an alloca and are
1167/// subsequently loaded can be rewritten to load both input pointers in the pred
1168/// blocks and then PHI the results, allowing the load of the alloca to be
1169/// promoted.
1170/// From this:
1171///   %P2 = phi [i32* %Alloca, i32* %Other]
1172///   %V = load i32* %P2
1173/// to:
1174///   %V1 = load i32* %Alloca      -> will be mem2reg'd
1175///   ...
1176///   %V2 = load i32* %Other
1177///   ...
1178///   %V = phi [i32 %V1, i32 %V2]
1179///
1180/// We can do this to a select if its only uses are loads and if the operand to
1181/// the select can be loaded unconditionally.
1182static bool isSafePHIToSpeculate(PHINode *PN) {
1183  // For now, we can only do this promotion if the load is in the same block as
1184  // the PHI, and if there are no stores between the phi and load.
1185  // TODO: Allow recursive phi users.
1186  // TODO: Allow stores.
1187  BasicBlock *BB = PN->getParent();
1188  unsigned MaxAlign = 0;
1189  for (User *U : PN->users()) {
1190    LoadInst *LI = dyn_cast<LoadInst>(U);
1191    if (!LI || !LI->isSimple()) return false;
1192
1193    // For now we only allow loads in the same block as the PHI.  This is a
1194    // common case that happens when instcombine merges two loads through a PHI.
1195    if (LI->getParent() != BB) return false;
1196
1197    // Ensure that there are no instructions between the PHI and the load that
1198    // could store.
1199    for (BasicBlock::iterator BBI(PN); &*BBI != LI; ++BBI)
1200      if (BBI->mayWriteToMemory())
1201        return false;
1202
1203    MaxAlign = std::max(MaxAlign, LI->getAlignment());
1204  }
1205
1206  const DataLayout &DL = PN->getModule()->getDataLayout();
1207
1208  // Okay, we know that we have one or more loads in the same block as the PHI.
1209  // We can transform this if it is safe to push the loads into the predecessor
1210  // blocks.  The only thing to watch out for is that we can't put a possibly
1211  // trapping load in the predecessor if it is a critical edge.
1212  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1213    BasicBlock *Pred = PN->getIncomingBlock(i);
1214    Value *InVal = PN->getIncomingValue(i);
1215
1216    // If the terminator of the predecessor has side-effects (an invoke),
1217    // there is no safe place to put a load in the predecessor.
1218    if (Pred->getTerminator()->mayHaveSideEffects())
1219      return false;
1220
1221    // If the value is produced by the terminator of the predecessor
1222    // (an invoke), there is no valid place to put a load in the predecessor.
1223    if (Pred->getTerminator() == InVal)
1224      return false;
1225
1226    // If the predecessor has a single successor, then the edge isn't critical.
1227    if (Pred->getTerminator()->getNumSuccessors() == 1)
1228      continue;
1229
1230    // If this pointer is always safe to load, or if we can prove that there is
1231    // already a load in the block, then we can move the load to the pred block.
1232    if (isDereferenceablePointer(InVal, DL) ||
1233        isSafeToLoadUnconditionally(InVal, Pred->getTerminator(), MaxAlign))
1234      continue;
1235
1236    return false;
1237  }
1238
1239  return true;
1240}
1241
1242
1243/// tryToMakeAllocaBePromotable - This returns true if the alloca only has
1244/// direct (non-volatile) loads and stores to it.  If the alloca is close but
1245/// not quite there, this will transform the code to allow promotion.  As such,
1246/// it is a non-pure predicate.
1247static bool tryToMakeAllocaBePromotable(AllocaInst *AI, const DataLayout &DL) {
1248  SetVector<Instruction*, SmallVector<Instruction*, 4>,
1249            SmallPtrSet<Instruction*, 4> > InstsToRewrite;
1250  for (User *U : AI->users()) {
1251    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
1252      if (!LI->isSimple())
1253        return false;
1254      continue;
1255    }
1256
1257    if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
1258      if (SI->getOperand(0) == AI || !SI->isSimple())
1259        return false;   // Don't allow a store OF the AI, only INTO the AI.
1260      continue;
1261    }
1262
1263    if (SelectInst *SI = dyn_cast<SelectInst>(U)) {
1264      // If the condition being selected on is a constant, fold the select, yes
1265      // this does (rarely) happen early on.
1266      if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getCondition())) {
1267        Value *Result = SI->getOperand(1+CI->isZero());
1268        SI->replaceAllUsesWith(Result);
1269        SI->eraseFromParent();
1270
1271        // This is very rare and we just scrambled the use list of AI, start
1272        // over completely.
1273        return tryToMakeAllocaBePromotable(AI, DL);
1274      }
1275
1276      // If it is safe to turn "load (select c, AI, ptr)" into a select of two
1277      // loads, then we can transform this by rewriting the select.
1278      if (!isSafeSelectToSpeculate(SI))
1279        return false;
1280
1281      InstsToRewrite.insert(SI);
1282      continue;
1283    }
1284
1285    if (PHINode *PN = dyn_cast<PHINode>(U)) {
1286      if (PN->use_empty()) {  // Dead PHIs can be stripped.
1287        InstsToRewrite.insert(PN);
1288        continue;
1289      }
1290
1291      // If it is safe to turn "load (phi [AI, ptr, ...])" into a PHI of loads
1292      // in the pred blocks, then we can transform this by rewriting the PHI.
1293      if (!isSafePHIToSpeculate(PN))
1294        return false;
1295
1296      InstsToRewrite.insert(PN);
1297      continue;
1298    }
1299
1300    if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) {
1301      if (onlyUsedByLifetimeMarkers(BCI)) {
1302        InstsToRewrite.insert(BCI);
1303        continue;
1304      }
1305    }
1306
1307    return false;
1308  }
1309
1310  // If there are no instructions to rewrite, then all uses are load/stores and
1311  // we're done!
1312  if (InstsToRewrite.empty())
1313    return true;
1314
1315  // If we have instructions that need to be rewritten for this to be promotable
1316  // take care of it now.
1317  for (unsigned i = 0, e = InstsToRewrite.size(); i != e; ++i) {
1318    if (BitCastInst *BCI = dyn_cast<BitCastInst>(InstsToRewrite[i])) {
1319      // This could only be a bitcast used by nothing but lifetime intrinsics.
1320      for (BitCastInst::user_iterator I = BCI->user_begin(), E = BCI->user_end();
1321           I != E;)
1322        cast<Instruction>(*I++)->eraseFromParent();
1323      BCI->eraseFromParent();
1324      continue;
1325    }
1326
1327    if (SelectInst *SI = dyn_cast<SelectInst>(InstsToRewrite[i])) {
1328      // Selects in InstsToRewrite only have load uses.  Rewrite each as two
1329      // loads with a new select.
1330      while (!SI->use_empty()) {
1331        LoadInst *LI = cast<LoadInst>(SI->user_back());
1332
1333        IRBuilder<> Builder(LI);
1334        LoadInst *TrueLoad =
1335          Builder.CreateLoad(SI->getTrueValue(), LI->getName()+".t");
1336        LoadInst *FalseLoad =
1337          Builder.CreateLoad(SI->getFalseValue(), LI->getName()+".f");
1338
1339        // Transfer alignment and AA info if present.
1340        TrueLoad->setAlignment(LI->getAlignment());
1341        FalseLoad->setAlignment(LI->getAlignment());
1342
1343        AAMDNodes Tags;
1344        LI->getAAMetadata(Tags);
1345        if (Tags) {
1346          TrueLoad->setAAMetadata(Tags);
1347          FalseLoad->setAAMetadata(Tags);
1348        }
1349
1350        Value *V = Builder.CreateSelect(SI->getCondition(), TrueLoad, FalseLoad);
1351        V->takeName(LI);
1352        LI->replaceAllUsesWith(V);
1353        LI->eraseFromParent();
1354      }
1355
1356      // Now that all the loads are gone, the select is gone too.
1357      SI->eraseFromParent();
1358      continue;
1359    }
1360
1361    // Otherwise, we have a PHI node which allows us to push the loads into the
1362    // predecessors.
1363    PHINode *PN = cast<PHINode>(InstsToRewrite[i]);
1364    if (PN->use_empty()) {
1365      PN->eraseFromParent();
1366      continue;
1367    }
1368
1369    Type *LoadTy = cast<PointerType>(PN->getType())->getElementType();
1370    PHINode *NewPN = PHINode::Create(LoadTy, PN->getNumIncomingValues(),
1371                                     PN->getName()+".ld", PN);
1372
1373    // Get the AA tags and alignment to use from one of the loads.  It doesn't
1374    // matter which one we get and if any differ, it doesn't matter.
1375    LoadInst *SomeLoad = cast<LoadInst>(PN->user_back());
1376
1377    AAMDNodes AATags;
1378    SomeLoad->getAAMetadata(AATags);
1379    unsigned Align = SomeLoad->getAlignment();
1380
1381    // Rewrite all loads of the PN to use the new PHI.
1382    while (!PN->use_empty()) {
1383      LoadInst *LI = cast<LoadInst>(PN->user_back());
1384      LI->replaceAllUsesWith(NewPN);
1385      LI->eraseFromParent();
1386    }
1387
1388    // Inject loads into all of the pred blocks.  Keep track of which blocks we
1389    // insert them into in case we have multiple edges from the same block.
1390    DenseMap<BasicBlock*, LoadInst*> InsertedLoads;
1391
1392    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1393      BasicBlock *Pred = PN->getIncomingBlock(i);
1394      LoadInst *&Load = InsertedLoads[Pred];
1395      if (!Load) {
1396        Load = new LoadInst(PN->getIncomingValue(i),
1397                            PN->getName() + "." + Pred->getName(),
1398                            Pred->getTerminator());
1399        Load->setAlignment(Align);
1400        if (AATags) Load->setAAMetadata(AATags);
1401      }
1402
1403      NewPN->addIncoming(Load, Pred);
1404    }
1405
1406    PN->eraseFromParent();
1407  }
1408
1409  ++NumAdjusted;
1410  return true;
1411}
1412
1413bool SROA::performPromotion(Function &F) {
1414  std::vector<AllocaInst*> Allocas;
1415  const DataLayout &DL = F.getParent()->getDataLayout();
1416  DominatorTree *DT = nullptr;
1417  if (HasDomTree)
1418    DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
1419  AssumptionCache &AC =
1420      getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
1421
1422  BasicBlock &BB = F.getEntryBlock();  // Get the entry node for the function
1423  DIBuilder DIB(*F.getParent(), /*AllowUnresolved*/ false);
1424  bool Changed = false;
1425  SmallVector<Instruction*, 64> Insts;
1426  while (1) {
1427    Allocas.clear();
1428
1429    // Find allocas that are safe to promote, by looking at all instructions in
1430    // the entry node
1431    for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
1432      if (AllocaInst *AI = dyn_cast<AllocaInst>(I))       // Is it an alloca?
1433        if (tryToMakeAllocaBePromotable(AI, DL))
1434          Allocas.push_back(AI);
1435
1436    if (Allocas.empty()) break;
1437
1438    if (HasDomTree)
1439      PromoteMemToReg(Allocas, *DT, nullptr, &AC);
1440    else {
1441      SSAUpdater SSA;
1442      for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
1443        AllocaInst *AI = Allocas[i];
1444
1445        // Build list of instructions to promote.
1446        for (User *U : AI->users())
1447          Insts.push_back(cast<Instruction>(U));
1448        AllocaPromoter(Insts, SSA, &DIB).run(AI, Insts);
1449        Insts.clear();
1450      }
1451    }
1452    NumPromoted += Allocas.size();
1453    Changed = true;
1454  }
1455
1456  return Changed;
1457}
1458
1459
1460/// ShouldAttemptScalarRepl - Decide if an alloca is a good candidate for
1461/// SROA.  It must be a struct or array type with a small number of elements.
1462bool SROA::ShouldAttemptScalarRepl(AllocaInst *AI) {
1463  Type *T = AI->getAllocatedType();
1464  // Do not promote any struct that has too many members.
1465  if (StructType *ST = dyn_cast<StructType>(T))
1466    return ST->getNumElements() <= StructMemberThreshold;
1467  // Do not promote any array that has too many elements.
1468  if (ArrayType *AT = dyn_cast<ArrayType>(T))
1469    return AT->getNumElements() <= ArrayElementThreshold;
1470  return false;
1471}
1472
1473// performScalarRepl - This algorithm is a simple worklist driven algorithm,
1474// which runs on all of the alloca instructions in the entry block, removing
1475// them if they are only used by getelementptr instructions.
1476//
1477bool SROA::performScalarRepl(Function &F) {
1478  std::vector<AllocaInst*> WorkList;
1479  const DataLayout &DL = F.getParent()->getDataLayout();
1480
1481  // Scan the entry basic block, adding allocas to the worklist.
1482  BasicBlock &BB = F.getEntryBlock();
1483  for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
1484    if (AllocaInst *A = dyn_cast<AllocaInst>(I))
1485      WorkList.push_back(A);
1486
1487  // Process the worklist
1488  bool Changed = false;
1489  while (!WorkList.empty()) {
1490    AllocaInst *AI = WorkList.back();
1491    WorkList.pop_back();
1492
1493    // Handle dead allocas trivially.  These can be formed by SROA'ing arrays
1494    // with unused elements.
1495    if (AI->use_empty()) {
1496      AI->eraseFromParent();
1497      Changed = true;
1498      continue;
1499    }
1500
1501    // If this alloca is impossible for us to promote, reject it early.
1502    if (AI->isArrayAllocation() || !AI->getAllocatedType()->isSized())
1503      continue;
1504
1505    // Check to see if we can perform the core SROA transformation.  We cannot
1506    // transform the allocation instruction if it is an array allocation
1507    // (allocations OF arrays are ok though), and an allocation of a scalar
1508    // value cannot be decomposed at all.
1509    uint64_t AllocaSize = DL.getTypeAllocSize(AI->getAllocatedType());
1510
1511    // Do not promote [0 x %struct].
1512    if (AllocaSize == 0) continue;
1513
1514    // Do not promote any struct whose size is too big.
1515    if (AllocaSize > SRThreshold) continue;
1516
1517    // If the alloca looks like a good candidate for scalar replacement, and if
1518    // all its users can be transformed, then split up the aggregate into its
1519    // separate elements.
1520    if (ShouldAttemptScalarRepl(AI) && isSafeAllocaToScalarRepl(AI)) {
1521      DoScalarReplacement(AI, WorkList);
1522      Changed = true;
1523      continue;
1524    }
1525
1526    // If we can turn this aggregate value (potentially with casts) into a
1527    // simple scalar value that can be mem2reg'd into a register value.
1528    // IsNotTrivial tracks whether this is something that mem2reg could have
1529    // promoted itself.  If so, we don't want to transform it needlessly.  Note
1530    // that we can't just check based on the type: the alloca may be of an i32
1531    // but that has pointer arithmetic to set byte 3 of it or something.
1532    if (AllocaInst *NewAI =
1533            ConvertToScalarInfo((unsigned)AllocaSize, DL, ScalarLoadThreshold)
1534                .TryConvert(AI)) {
1535      NewAI->takeName(AI);
1536      AI->eraseFromParent();
1537      ++NumConverted;
1538      Changed = true;
1539      continue;
1540    }
1541
1542    // Otherwise, couldn't process this alloca.
1543  }
1544
1545  return Changed;
1546}
1547
1548/// DoScalarReplacement - This alloca satisfied the isSafeAllocaToScalarRepl
1549/// predicate, do SROA now.
1550void SROA::DoScalarReplacement(AllocaInst *AI,
1551                               std::vector<AllocaInst*> &WorkList) {
1552  DEBUG(dbgs() << "Found inst to SROA: " << *AI << '\n');
1553  SmallVector<AllocaInst*, 32> ElementAllocas;
1554  if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
1555    ElementAllocas.reserve(ST->getNumContainedTypes());
1556    for (unsigned i = 0, e = ST->getNumContainedTypes(); i != e; ++i) {
1557      AllocaInst *NA = new AllocaInst(ST->getContainedType(i), nullptr,
1558                                      AI->getAlignment(),
1559                                      AI->getName() + "." + Twine(i), AI);
1560      ElementAllocas.push_back(NA);
1561      WorkList.push_back(NA);  // Add to worklist for recursive processing
1562    }
1563  } else {
1564    ArrayType *AT = cast<ArrayType>(AI->getAllocatedType());
1565    ElementAllocas.reserve(AT->getNumElements());
1566    Type *ElTy = AT->getElementType();
1567    for (unsigned i = 0, e = AT->getNumElements(); i != e; ++i) {
1568      AllocaInst *NA = new AllocaInst(ElTy, nullptr, AI->getAlignment(),
1569                                      AI->getName() + "." + Twine(i), AI);
1570      ElementAllocas.push_back(NA);
1571      WorkList.push_back(NA);  // Add to worklist for recursive processing
1572    }
1573  }
1574
1575  // Now that we have created the new alloca instructions, rewrite all the
1576  // uses of the old alloca.
1577  RewriteForScalarRepl(AI, AI, 0, ElementAllocas);
1578
1579  // Now erase any instructions that were made dead while rewriting the alloca.
1580  DeleteDeadInstructions();
1581  AI->eraseFromParent();
1582
1583  ++NumReplaced;
1584}
1585
1586/// DeleteDeadInstructions - Erase instructions on the DeadInstrs list,
1587/// recursively including all their operands that become trivially dead.
1588void SROA::DeleteDeadInstructions() {
1589  while (!DeadInsts.empty()) {
1590    Instruction *I = cast<Instruction>(DeadInsts.pop_back_val());
1591
1592    for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
1593      if (Instruction *U = dyn_cast<Instruction>(*OI)) {
1594        // Zero out the operand and see if it becomes trivially dead.
1595        // (But, don't add allocas to the dead instruction list -- they are
1596        // already on the worklist and will be deleted separately.)
1597        *OI = nullptr;
1598        if (isInstructionTriviallyDead(U) && !isa<AllocaInst>(U))
1599          DeadInsts.push_back(U);
1600      }
1601
1602    I->eraseFromParent();
1603  }
1604}
1605
1606/// isSafeForScalarRepl - Check if instruction I is a safe use with regard to
1607/// performing scalar replacement of alloca AI.  The results are flagged in
1608/// the Info parameter.  Offset indicates the position within AI that is
1609/// referenced by this instruction.
1610void SROA::isSafeForScalarRepl(Instruction *I, uint64_t Offset,
1611                               AllocaInfo &Info) {
1612  const DataLayout &DL = I->getModule()->getDataLayout();
1613  for (Use &U : I->uses()) {
1614    Instruction *User = cast<Instruction>(U.getUser());
1615
1616    if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1617      isSafeForScalarRepl(BC, Offset, Info);
1618    } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1619      uint64_t GEPOffset = Offset;
1620      isSafeGEP(GEPI, GEPOffset, Info);
1621      if (!Info.isUnsafe)
1622        isSafeForScalarRepl(GEPI, GEPOffset, Info);
1623    } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1624      ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1625      if (!Length || Length->isNegative())
1626        return MarkUnsafe(Info, User);
1627
1628      isSafeMemAccess(Offset, Length->getZExtValue(), nullptr,
1629                      U.getOperandNo() == 0, Info, MI,
1630                      true /*AllowWholeAccess*/);
1631    } else if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1632      if (!LI->isSimple())
1633        return MarkUnsafe(Info, User);
1634      Type *LIType = LI->getType();
1635      isSafeMemAccess(Offset, DL.getTypeAllocSize(LIType), LIType, false, Info,
1636                      LI, true /*AllowWholeAccess*/);
1637      Info.hasALoadOrStore = true;
1638
1639    } else if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1640      // Store is ok if storing INTO the pointer, not storing the pointer
1641      if (!SI->isSimple() || SI->getOperand(0) == I)
1642        return MarkUnsafe(Info, User);
1643
1644      Type *SIType = SI->getOperand(0)->getType();
1645      isSafeMemAccess(Offset, DL.getTypeAllocSize(SIType), SIType, true, Info,
1646                      SI, true /*AllowWholeAccess*/);
1647      Info.hasALoadOrStore = true;
1648    } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1649      if (II->getIntrinsicID() != Intrinsic::lifetime_start &&
1650          II->getIntrinsicID() != Intrinsic::lifetime_end)
1651        return MarkUnsafe(Info, User);
1652    } else if (isa<PHINode>(User) || isa<SelectInst>(User)) {
1653      isSafePHISelectUseForScalarRepl(User, Offset, Info);
1654    } else {
1655      return MarkUnsafe(Info, User);
1656    }
1657    if (Info.isUnsafe) return;
1658  }
1659}
1660
1661
1662/// isSafePHIUseForScalarRepl - If we see a PHI node or select using a pointer
1663/// derived from the alloca, we can often still split the alloca into elements.
1664/// This is useful if we have a large alloca where one element is phi'd
1665/// together somewhere: we can SRoA and promote all the other elements even if
1666/// we end up not being able to promote this one.
1667///
1668/// All we require is that the uses of the PHI do not index into other parts of
1669/// the alloca.  The most important use case for this is single load and stores
1670/// that are PHI'd together, which can happen due to code sinking.
1671void SROA::isSafePHISelectUseForScalarRepl(Instruction *I, uint64_t Offset,
1672                                           AllocaInfo &Info) {
1673  // If we've already checked this PHI, don't do it again.
1674  if (PHINode *PN = dyn_cast<PHINode>(I))
1675    if (!Info.CheckedPHIs.insert(PN).second)
1676      return;
1677
1678  const DataLayout &DL = I->getModule()->getDataLayout();
1679  for (User *U : I->users()) {
1680    Instruction *UI = cast<Instruction>(U);
1681
1682    if (BitCastInst *BC = dyn_cast<BitCastInst>(UI)) {
1683      isSafePHISelectUseForScalarRepl(BC, Offset, Info);
1684    } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(UI)) {
1685      // Only allow "bitcast" GEPs for simplicity.  We could generalize this,
1686      // but would have to prove that we're staying inside of an element being
1687      // promoted.
1688      if (!GEPI->hasAllZeroIndices())
1689        return MarkUnsafe(Info, UI);
1690      isSafePHISelectUseForScalarRepl(GEPI, Offset, Info);
1691    } else if (LoadInst *LI = dyn_cast<LoadInst>(UI)) {
1692      if (!LI->isSimple())
1693        return MarkUnsafe(Info, UI);
1694      Type *LIType = LI->getType();
1695      isSafeMemAccess(Offset, DL.getTypeAllocSize(LIType), LIType, false, Info,
1696                      LI, false /*AllowWholeAccess*/);
1697      Info.hasALoadOrStore = true;
1698
1699    } else if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
1700      // Store is ok if storing INTO the pointer, not storing the pointer
1701      if (!SI->isSimple() || SI->getOperand(0) == I)
1702        return MarkUnsafe(Info, UI);
1703
1704      Type *SIType = SI->getOperand(0)->getType();
1705      isSafeMemAccess(Offset, DL.getTypeAllocSize(SIType), SIType, true, Info,
1706                      SI, false /*AllowWholeAccess*/);
1707      Info.hasALoadOrStore = true;
1708    } else if (isa<PHINode>(UI) || isa<SelectInst>(UI)) {
1709      isSafePHISelectUseForScalarRepl(UI, Offset, Info);
1710    } else {
1711      return MarkUnsafe(Info, UI);
1712    }
1713    if (Info.isUnsafe) return;
1714  }
1715}
1716
1717/// isSafeGEP - Check if a GEP instruction can be handled for scalar
1718/// replacement.  It is safe when all the indices are constant, in-bounds
1719/// references, and when the resulting offset corresponds to an element within
1720/// the alloca type.  The results are flagged in the Info parameter.  Upon
1721/// return, Offset is adjusted as specified by the GEP indices.
1722void SROA::isSafeGEP(GetElementPtrInst *GEPI,
1723                     uint64_t &Offset, AllocaInfo &Info) {
1724  gep_type_iterator GEPIt = gep_type_begin(GEPI), E = gep_type_end(GEPI);
1725  if (GEPIt == E)
1726    return;
1727  bool NonConstant = false;
1728  unsigned NonConstantIdxSize = 0;
1729
1730  // Walk through the GEP type indices, checking the types that this indexes
1731  // into.
1732  for (; GEPIt != E; ++GEPIt) {
1733    // Ignore struct elements, no extra checking needed for these.
1734    if ((*GEPIt)->isStructTy())
1735      continue;
1736
1737    ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPIt.getOperand());
1738    if (!IdxVal)
1739      return MarkUnsafe(Info, GEPI);
1740  }
1741
1742  // Compute the offset due to this GEP and check if the alloca has a
1743  // component element at that offset.
1744  SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
1745  // If this GEP is non-constant then the last operand must have been a
1746  // dynamic index into a vector.  Pop this now as it has no impact on the
1747  // constant part of the offset.
1748  if (NonConstant)
1749    Indices.pop_back();
1750
1751  const DataLayout &DL = GEPI->getModule()->getDataLayout();
1752  Offset += DL.getIndexedOffset(GEPI->getPointerOperandType(), Indices);
1753  if (!TypeHasComponent(Info.AI->getAllocatedType(), Offset, NonConstantIdxSize,
1754                        DL))
1755    MarkUnsafe(Info, GEPI);
1756}
1757
1758/// isHomogeneousAggregate - Check if type T is a struct or array containing
1759/// elements of the same type (which is always true for arrays).  If so,
1760/// return true with NumElts and EltTy set to the number of elements and the
1761/// element type, respectively.
1762static bool isHomogeneousAggregate(Type *T, unsigned &NumElts,
1763                                   Type *&EltTy) {
1764  if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1765    NumElts = AT->getNumElements();
1766    EltTy = (NumElts == 0 ? nullptr : AT->getElementType());
1767    return true;
1768  }
1769  if (StructType *ST = dyn_cast<StructType>(T)) {
1770    NumElts = ST->getNumContainedTypes();
1771    EltTy = (NumElts == 0 ? nullptr : ST->getContainedType(0));
1772    for (unsigned n = 1; n < NumElts; ++n) {
1773      if (ST->getContainedType(n) != EltTy)
1774        return false;
1775    }
1776    return true;
1777  }
1778  return false;
1779}
1780
1781/// isCompatibleAggregate - Check if T1 and T2 are either the same type or are
1782/// "homogeneous" aggregates with the same element type and number of elements.
1783static bool isCompatibleAggregate(Type *T1, Type *T2) {
1784  if (T1 == T2)
1785    return true;
1786
1787  unsigned NumElts1, NumElts2;
1788  Type *EltTy1, *EltTy2;
1789  if (isHomogeneousAggregate(T1, NumElts1, EltTy1) &&
1790      isHomogeneousAggregate(T2, NumElts2, EltTy2) &&
1791      NumElts1 == NumElts2 &&
1792      EltTy1 == EltTy2)
1793    return true;
1794
1795  return false;
1796}
1797
1798/// isSafeMemAccess - Check if a load/store/memcpy operates on the entire AI
1799/// alloca or has an offset and size that corresponds to a component element
1800/// within it.  The offset checked here may have been formed from a GEP with a
1801/// pointer bitcasted to a different type.
1802///
1803/// If AllowWholeAccess is true, then this allows uses of the entire alloca as a
1804/// unit.  If false, it only allows accesses known to be in a single element.
1805void SROA::isSafeMemAccess(uint64_t Offset, uint64_t MemSize,
1806                           Type *MemOpType, bool isStore,
1807                           AllocaInfo &Info, Instruction *TheAccess,
1808                           bool AllowWholeAccess) {
1809  const DataLayout &DL = TheAccess->getModule()->getDataLayout();
1810  // Check if this is a load/store of the entire alloca.
1811  if (Offset == 0 && AllowWholeAccess &&
1812      MemSize == DL.getTypeAllocSize(Info.AI->getAllocatedType())) {
1813    // This can be safe for MemIntrinsics (where MemOpType is 0) and integer
1814    // loads/stores (which are essentially the same as the MemIntrinsics with
1815    // regard to copying padding between elements).  But, if an alloca is
1816    // flagged as both a source and destination of such operations, we'll need
1817    // to check later for padding between elements.
1818    if (!MemOpType || MemOpType->isIntegerTy()) {
1819      if (isStore)
1820        Info.isMemCpyDst = true;
1821      else
1822        Info.isMemCpySrc = true;
1823      return;
1824    }
1825    // This is also safe for references using a type that is compatible with
1826    // the type of the alloca, so that loads/stores can be rewritten using
1827    // insertvalue/extractvalue.
1828    if (isCompatibleAggregate(MemOpType, Info.AI->getAllocatedType())) {
1829      Info.hasSubelementAccess = true;
1830      return;
1831    }
1832  }
1833  // Check if the offset/size correspond to a component within the alloca type.
1834  Type *T = Info.AI->getAllocatedType();
1835  if (TypeHasComponent(T, Offset, MemSize, DL)) {
1836    Info.hasSubelementAccess = true;
1837    return;
1838  }
1839
1840  return MarkUnsafe(Info, TheAccess);
1841}
1842
1843/// TypeHasComponent - Return true if T has a component type with the
1844/// specified offset and size.  If Size is zero, do not check the size.
1845bool SROA::TypeHasComponent(Type *T, uint64_t Offset, uint64_t Size,
1846                            const DataLayout &DL) {
1847  Type *EltTy;
1848  uint64_t EltSize;
1849  if (StructType *ST = dyn_cast<StructType>(T)) {
1850    const StructLayout *Layout = DL.getStructLayout(ST);
1851    unsigned EltIdx = Layout->getElementContainingOffset(Offset);
1852    EltTy = ST->getContainedType(EltIdx);
1853    EltSize = DL.getTypeAllocSize(EltTy);
1854    Offset -= Layout->getElementOffset(EltIdx);
1855  } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
1856    EltTy = AT->getElementType();
1857    EltSize = DL.getTypeAllocSize(EltTy);
1858    if (Offset >= AT->getNumElements() * EltSize)
1859      return false;
1860    Offset %= EltSize;
1861  } else if (VectorType *VT = dyn_cast<VectorType>(T)) {
1862    EltTy = VT->getElementType();
1863    EltSize = DL.getTypeAllocSize(EltTy);
1864    if (Offset >= VT->getNumElements() * EltSize)
1865      return false;
1866    Offset %= EltSize;
1867  } else {
1868    return false;
1869  }
1870  if (Offset == 0 && (Size == 0 || EltSize == Size))
1871    return true;
1872  // Check if the component spans multiple elements.
1873  if (Offset + Size > EltSize)
1874    return false;
1875  return TypeHasComponent(EltTy, Offset, Size, DL);
1876}
1877
1878/// RewriteForScalarRepl - Alloca AI is being split into NewElts, so rewrite
1879/// the instruction I, which references it, to use the separate elements.
1880/// Offset indicates the position within AI that is referenced by this
1881/// instruction.
1882void SROA::RewriteForScalarRepl(Instruction *I, AllocaInst *AI, uint64_t Offset,
1883                                SmallVectorImpl<AllocaInst *> &NewElts) {
1884  const DataLayout &DL = I->getModule()->getDataLayout();
1885  for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI!=E;) {
1886    Use &TheUse = *UI++;
1887    Instruction *User = cast<Instruction>(TheUse.getUser());
1888
1889    if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
1890      RewriteBitCast(BC, AI, Offset, NewElts);
1891      continue;
1892    }
1893
1894    if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
1895      RewriteGEP(GEPI, AI, Offset, NewElts);
1896      continue;
1897    }
1898
1899    if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(User)) {
1900      ConstantInt *Length = dyn_cast<ConstantInt>(MI->getLength());
1901      uint64_t MemSize = Length->getZExtValue();
1902      if (Offset == 0 && MemSize == DL.getTypeAllocSize(AI->getAllocatedType()))
1903        RewriteMemIntrinUserOfAlloca(MI, I, AI, NewElts);
1904      // Otherwise the intrinsic can only touch a single element and the
1905      // address operand will be updated, so nothing else needs to be done.
1906      continue;
1907    }
1908
1909    if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(User)) {
1910      if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
1911          II->getIntrinsicID() == Intrinsic::lifetime_end) {
1912        RewriteLifetimeIntrinsic(II, AI, Offset, NewElts);
1913      }
1914      continue;
1915    }
1916
1917    if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
1918      Type *LIType = LI->getType();
1919
1920      if (isCompatibleAggregate(LIType, AI->getAllocatedType())) {
1921        // Replace:
1922        //   %res = load { i32, i32 }* %alloc
1923        // with:
1924        //   %load.0 = load i32* %alloc.0
1925        //   %insert.0 insertvalue { i32, i32 } zeroinitializer, i32 %load.0, 0
1926        //   %load.1 = load i32* %alloc.1
1927        //   %insert = insertvalue { i32, i32 } %insert.0, i32 %load.1, 1
1928        // (Also works for arrays instead of structs)
1929        Value *Insert = UndefValue::get(LIType);
1930        IRBuilder<> Builder(LI);
1931        for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1932          Value *Load = Builder.CreateLoad(NewElts[i], "load");
1933          Insert = Builder.CreateInsertValue(Insert, Load, i, "insert");
1934        }
1935        LI->replaceAllUsesWith(Insert);
1936        DeadInsts.push_back(LI);
1937      } else if (LIType->isIntegerTy() &&
1938                 DL.getTypeAllocSize(LIType) ==
1939                     DL.getTypeAllocSize(AI->getAllocatedType())) {
1940        // If this is a load of the entire alloca to an integer, rewrite it.
1941        RewriteLoadUserOfWholeAlloca(LI, AI, NewElts);
1942      }
1943      continue;
1944    }
1945
1946    if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
1947      Value *Val = SI->getOperand(0);
1948      Type *SIType = Val->getType();
1949      if (isCompatibleAggregate(SIType, AI->getAllocatedType())) {
1950        // Replace:
1951        //   store { i32, i32 } %val, { i32, i32 }* %alloc
1952        // with:
1953        //   %val.0 = extractvalue { i32, i32 } %val, 0
1954        //   store i32 %val.0, i32* %alloc.0
1955        //   %val.1 = extractvalue { i32, i32 } %val, 1
1956        //   store i32 %val.1, i32* %alloc.1
1957        // (Also works for arrays instead of structs)
1958        IRBuilder<> Builder(SI);
1959        for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
1960          Value *Extract = Builder.CreateExtractValue(Val, i, Val->getName());
1961          Builder.CreateStore(Extract, NewElts[i]);
1962        }
1963        DeadInsts.push_back(SI);
1964      } else if (SIType->isIntegerTy() &&
1965                 DL.getTypeAllocSize(SIType) ==
1966                     DL.getTypeAllocSize(AI->getAllocatedType())) {
1967        // If this is a store of the entire alloca from an integer, rewrite it.
1968        RewriteStoreUserOfWholeAlloca(SI, AI, NewElts);
1969      }
1970      continue;
1971    }
1972
1973    if (isa<SelectInst>(User) || isa<PHINode>(User)) {
1974      // If we have a PHI user of the alloca itself (as opposed to a GEP or
1975      // bitcast) we have to rewrite it.  GEP and bitcast uses will be RAUW'd to
1976      // the new pointer.
1977      if (!isa<AllocaInst>(I)) continue;
1978
1979      assert(Offset == 0 && NewElts[0] &&
1980             "Direct alloca use should have a zero offset");
1981
1982      // If we have a use of the alloca, we know the derived uses will be
1983      // utilizing just the first element of the scalarized result.  Insert a
1984      // bitcast of the first alloca before the user as required.
1985      AllocaInst *NewAI = NewElts[0];
1986      BitCastInst *BCI = new BitCastInst(NewAI, AI->getType(), "", NewAI);
1987      NewAI->moveBefore(BCI);
1988      TheUse = BCI;
1989      continue;
1990    }
1991  }
1992}
1993
1994/// RewriteBitCast - Update a bitcast reference to the alloca being replaced
1995/// and recursively continue updating all of its uses.
1996void SROA::RewriteBitCast(BitCastInst *BC, AllocaInst *AI, uint64_t Offset,
1997                          SmallVectorImpl<AllocaInst *> &NewElts) {
1998  RewriteForScalarRepl(BC, AI, Offset, NewElts);
1999  if (BC->getOperand(0) != AI)
2000    return;
2001
2002  // The bitcast references the original alloca.  Replace its uses with
2003  // references to the alloca containing offset zero (which is normally at
2004  // index zero, but might not be in cases involving structs with elements
2005  // of size zero).
2006  Type *T = AI->getAllocatedType();
2007  uint64_t EltOffset = 0;
2008  Type *IdxTy;
2009  uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy,
2010                                      BC->getModule()->getDataLayout());
2011  Instruction *Val = NewElts[Idx];
2012  if (Val->getType() != BC->getDestTy()) {
2013    Val = new BitCastInst(Val, BC->getDestTy(), "", BC);
2014    Val->takeName(BC);
2015  }
2016  BC->replaceAllUsesWith(Val);
2017  DeadInsts.push_back(BC);
2018}
2019
2020/// FindElementAndOffset - Return the index of the element containing Offset
2021/// within the specified type, which must be either a struct or an array.
2022/// Sets T to the type of the element and Offset to the offset within that
2023/// element.  IdxTy is set to the type of the index result to be used in a
2024/// GEP instruction.
2025uint64_t SROA::FindElementAndOffset(Type *&T, uint64_t &Offset, Type *&IdxTy,
2026                                    const DataLayout &DL) {
2027  uint64_t Idx = 0;
2028
2029  if (StructType *ST = dyn_cast<StructType>(T)) {
2030    const StructLayout *Layout = DL.getStructLayout(ST);
2031    Idx = Layout->getElementContainingOffset(Offset);
2032    T = ST->getContainedType(Idx);
2033    Offset -= Layout->getElementOffset(Idx);
2034    IdxTy = Type::getInt32Ty(T->getContext());
2035    return Idx;
2036  } else if (ArrayType *AT = dyn_cast<ArrayType>(T)) {
2037    T = AT->getElementType();
2038    uint64_t EltSize = DL.getTypeAllocSize(T);
2039    Idx = Offset / EltSize;
2040    Offset -= Idx * EltSize;
2041    IdxTy = Type::getInt64Ty(T->getContext());
2042    return Idx;
2043  }
2044  VectorType *VT = cast<VectorType>(T);
2045  T = VT->getElementType();
2046  uint64_t EltSize = DL.getTypeAllocSize(T);
2047  Idx = Offset / EltSize;
2048  Offset -= Idx * EltSize;
2049  IdxTy = Type::getInt64Ty(T->getContext());
2050  return Idx;
2051}
2052
2053/// RewriteGEP - Check if this GEP instruction moves the pointer across
2054/// elements of the alloca that are being split apart, and if so, rewrite
2055/// the GEP to be relative to the new element.
2056void SROA::RewriteGEP(GetElementPtrInst *GEPI, AllocaInst *AI, uint64_t Offset,
2057                      SmallVectorImpl<AllocaInst *> &NewElts) {
2058  uint64_t OldOffset = Offset;
2059  const DataLayout &DL = GEPI->getModule()->getDataLayout();
2060  SmallVector<Value*, 8> Indices(GEPI->op_begin() + 1, GEPI->op_end());
2061  // If the GEP was dynamic then it must have been a dynamic vector lookup.
2062  // In this case, it must be the last GEP operand which is dynamic so keep that
2063  // aside until we've found the constant GEP offset then add it back in at the
2064  // end.
2065  Value* NonConstantIdx = nullptr;
2066  if (!GEPI->hasAllConstantIndices())
2067    NonConstantIdx = Indices.pop_back_val();
2068  Offset += DL.getIndexedOffset(GEPI->getPointerOperandType(), Indices);
2069
2070  RewriteForScalarRepl(GEPI, AI, Offset, NewElts);
2071
2072  Type *T = AI->getAllocatedType();
2073  Type *IdxTy;
2074  uint64_t OldIdx = FindElementAndOffset(T, OldOffset, IdxTy, DL);
2075  if (GEPI->getOperand(0) == AI)
2076    OldIdx = ~0ULL; // Force the GEP to be rewritten.
2077
2078  T = AI->getAllocatedType();
2079  uint64_t EltOffset = Offset;
2080  uint64_t Idx = FindElementAndOffset(T, EltOffset, IdxTy, DL);
2081
2082  // If this GEP does not move the pointer across elements of the alloca
2083  // being split, then it does not needs to be rewritten.
2084  if (Idx == OldIdx)
2085    return;
2086
2087  Type *i32Ty = Type::getInt32Ty(AI->getContext());
2088  SmallVector<Value*, 8> NewArgs;
2089  NewArgs.push_back(Constant::getNullValue(i32Ty));
2090  while (EltOffset != 0) {
2091    uint64_t EltIdx = FindElementAndOffset(T, EltOffset, IdxTy, DL);
2092    NewArgs.push_back(ConstantInt::get(IdxTy, EltIdx));
2093  }
2094  if (NonConstantIdx) {
2095    Type* GepTy = T;
2096    // This GEP has a dynamic index.  We need to add "i32 0" to index through
2097    // any structs or arrays in the original type until we get to the vector
2098    // to index.
2099    while (!isa<VectorType>(GepTy)) {
2100      NewArgs.push_back(Constant::getNullValue(i32Ty));
2101      GepTy = cast<CompositeType>(GepTy)->getTypeAtIndex(0U);
2102    }
2103    NewArgs.push_back(NonConstantIdx);
2104  }
2105  Instruction *Val = NewElts[Idx];
2106  if (NewArgs.size() > 1) {
2107    Val = GetElementPtrInst::CreateInBounds(Val, NewArgs, "", GEPI);
2108    Val->takeName(GEPI);
2109  }
2110  if (Val->getType() != GEPI->getType())
2111    Val = new BitCastInst(Val, GEPI->getType(), Val->getName(), GEPI);
2112  GEPI->replaceAllUsesWith(Val);
2113  DeadInsts.push_back(GEPI);
2114}
2115
2116/// RewriteLifetimeIntrinsic - II is a lifetime.start/lifetime.end. Rewrite it
2117/// to mark the lifetime of the scalarized memory.
2118void SROA::RewriteLifetimeIntrinsic(IntrinsicInst *II, AllocaInst *AI,
2119                                    uint64_t Offset,
2120                                    SmallVectorImpl<AllocaInst *> &NewElts) {
2121  ConstantInt *OldSize = cast<ConstantInt>(II->getArgOperand(0));
2122  // Put matching lifetime markers on everything from Offset up to
2123  // Offset+OldSize.
2124  Type *AIType = AI->getAllocatedType();
2125  const DataLayout &DL = II->getModule()->getDataLayout();
2126  uint64_t NewOffset = Offset;
2127  Type *IdxTy;
2128  uint64_t Idx = FindElementAndOffset(AIType, NewOffset, IdxTy, DL);
2129
2130  IRBuilder<> Builder(II);
2131  uint64_t Size = OldSize->getLimitedValue();
2132
2133  if (NewOffset) {
2134    // Splice the first element and index 'NewOffset' bytes in.  SROA will
2135    // split the alloca again later.
2136    unsigned AS = AI->getType()->getAddressSpace();
2137    Value *V = Builder.CreateBitCast(NewElts[Idx], Builder.getInt8PtrTy(AS));
2138    V = Builder.CreateGEP(Builder.getInt8Ty(), V, Builder.getInt64(NewOffset));
2139
2140    IdxTy = NewElts[Idx]->getAllocatedType();
2141    uint64_t EltSize = DL.getTypeAllocSize(IdxTy) - NewOffset;
2142    if (EltSize > Size) {
2143      EltSize = Size;
2144      Size = 0;
2145    } else {
2146      Size -= EltSize;
2147    }
2148    if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2149      Builder.CreateLifetimeStart(V, Builder.getInt64(EltSize));
2150    else
2151      Builder.CreateLifetimeEnd(V, Builder.getInt64(EltSize));
2152    ++Idx;
2153  }
2154
2155  for (; Idx != NewElts.size() && Size; ++Idx) {
2156    IdxTy = NewElts[Idx]->getAllocatedType();
2157    uint64_t EltSize = DL.getTypeAllocSize(IdxTy);
2158    if (EltSize > Size) {
2159      EltSize = Size;
2160      Size = 0;
2161    } else {
2162      Size -= EltSize;
2163    }
2164    if (II->getIntrinsicID() == Intrinsic::lifetime_start)
2165      Builder.CreateLifetimeStart(NewElts[Idx],
2166                                  Builder.getInt64(EltSize));
2167    else
2168      Builder.CreateLifetimeEnd(NewElts[Idx],
2169                                Builder.getInt64(EltSize));
2170  }
2171  DeadInsts.push_back(II);
2172}
2173
2174/// RewriteMemIntrinUserOfAlloca - MI is a memcpy/memset/memmove from or to AI.
2175/// Rewrite it to copy or set the elements of the scalarized memory.
2176void
2177SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *Inst,
2178                                   AllocaInst *AI,
2179                                   SmallVectorImpl<AllocaInst *> &NewElts) {
2180  // If this is a memcpy/memmove, construct the other pointer as the
2181  // appropriate type.  The "Other" pointer is the pointer that goes to memory
2182  // that doesn't have anything to do with the alloca that we are promoting. For
2183  // memset, this Value* stays null.
2184  Value *OtherPtr = nullptr;
2185  unsigned MemAlignment = MI->getAlignment();
2186  if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) { // memmove/memcopy
2187    if (Inst == MTI->getRawDest())
2188      OtherPtr = MTI->getRawSource();
2189    else {
2190      assert(Inst == MTI->getRawSource());
2191      OtherPtr = MTI->getRawDest();
2192    }
2193  }
2194
2195  // If there is an other pointer, we want to convert it to the same pointer
2196  // type as AI has, so we can GEP through it safely.
2197  if (OtherPtr) {
2198    unsigned AddrSpace =
2199      cast<PointerType>(OtherPtr->getType())->getAddressSpace();
2200
2201    // Remove bitcasts and all-zero GEPs from OtherPtr.  This is an
2202    // optimization, but it's also required to detect the corner case where
2203    // both pointer operands are referencing the same memory, and where
2204    // OtherPtr may be a bitcast or GEP that currently being rewritten.  (This
2205    // function is only called for mem intrinsics that access the whole
2206    // aggregate, so non-zero GEPs are not an issue here.)
2207    OtherPtr = OtherPtr->stripPointerCasts();
2208
2209    // Copying the alloca to itself is a no-op: just delete it.
2210    if (OtherPtr == AI || OtherPtr == NewElts[0]) {
2211      // This code will run twice for a no-op memcpy -- once for each operand.
2212      // Put only one reference to MI on the DeadInsts list.
2213      for (SmallVectorImpl<Value *>::const_iterator I = DeadInsts.begin(),
2214             E = DeadInsts.end(); I != E; ++I)
2215        if (*I == MI) return;
2216      DeadInsts.push_back(MI);
2217      return;
2218    }
2219
2220    // If the pointer is not the right type, insert a bitcast to the right
2221    // type.
2222    Type *NewTy =
2223      PointerType::get(AI->getType()->getElementType(), AddrSpace);
2224
2225    if (OtherPtr->getType() != NewTy)
2226      OtherPtr = new BitCastInst(OtherPtr, NewTy, OtherPtr->getName(), MI);
2227  }
2228
2229  // Process each element of the aggregate.
2230  bool SROADest = MI->getRawDest() == Inst;
2231
2232  Constant *Zero = Constant::getNullValue(Type::getInt32Ty(MI->getContext()));
2233  const DataLayout &DL = MI->getModule()->getDataLayout();
2234
2235  for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2236    // If this is a memcpy/memmove, emit a GEP of the other element address.
2237    Value *OtherElt = nullptr;
2238    unsigned OtherEltAlign = MemAlignment;
2239
2240    if (OtherPtr) {
2241      Value *Idx[2] = { Zero,
2242                      ConstantInt::get(Type::getInt32Ty(MI->getContext()), i) };
2243      OtherElt = GetElementPtrInst::CreateInBounds(OtherPtr, Idx,
2244                                              OtherPtr->getName()+"."+Twine(i),
2245                                                   MI);
2246      uint64_t EltOffset;
2247      PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
2248      Type *OtherTy = OtherPtrTy->getElementType();
2249      if (StructType *ST = dyn_cast<StructType>(OtherTy)) {
2250        EltOffset = DL.getStructLayout(ST)->getElementOffset(i);
2251      } else {
2252        Type *EltTy = cast<SequentialType>(OtherTy)->getElementType();
2253        EltOffset = DL.getTypeAllocSize(EltTy) * i;
2254      }
2255
2256      // The alignment of the other pointer is the guaranteed alignment of the
2257      // element, which is affected by both the known alignment of the whole
2258      // mem intrinsic and the alignment of the element.  If the alignment of
2259      // the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
2260      // known alignment is just 4 bytes.
2261      OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
2262    }
2263
2264    Value *EltPtr = NewElts[i];
2265    Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
2266
2267    // If we got down to a scalar, insert a load or store as appropriate.
2268    if (EltTy->isSingleValueType()) {
2269      if (isa<MemTransferInst>(MI)) {
2270        if (SROADest) {
2271          // From Other to Alloca.
2272          Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
2273          new StoreInst(Elt, EltPtr, MI);
2274        } else {
2275          // From Alloca to Other.
2276          Value *Elt = new LoadInst(EltPtr, "tmp", MI);
2277          new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
2278        }
2279        continue;
2280      }
2281      assert(isa<MemSetInst>(MI));
2282
2283      // If the stored element is zero (common case), just store a null
2284      // constant.
2285      Constant *StoreVal;
2286      if (ConstantInt *CI = dyn_cast<ConstantInt>(MI->getArgOperand(1))) {
2287        if (CI->isZero()) {
2288          StoreVal = Constant::getNullValue(EltTy);  // 0.0, null, 0, <0,0>
2289        } else {
2290          // If EltTy is a vector type, get the element type.
2291          Type *ValTy = EltTy->getScalarType();
2292
2293          // Construct an integer with the right value.
2294          unsigned EltSize = DL.getTypeSizeInBits(ValTy);
2295          APInt OneVal(EltSize, CI->getZExtValue());
2296          APInt TotalVal(OneVal);
2297          // Set each byte.
2298          for (unsigned i = 0; 8*i < EltSize; ++i) {
2299            TotalVal = TotalVal.shl(8);
2300            TotalVal |= OneVal;
2301          }
2302
2303          // Convert the integer value to the appropriate type.
2304          StoreVal = ConstantInt::get(CI->getContext(), TotalVal);
2305          if (ValTy->isPointerTy())
2306            StoreVal = ConstantExpr::getIntToPtr(StoreVal, ValTy);
2307          else if (ValTy->isFloatingPointTy())
2308            StoreVal = ConstantExpr::getBitCast(StoreVal, ValTy);
2309          assert(StoreVal->getType() == ValTy && "Type mismatch!");
2310
2311          // If the requested value was a vector constant, create it.
2312          if (EltTy->isVectorTy()) {
2313            unsigned NumElts = cast<VectorType>(EltTy)->getNumElements();
2314            StoreVal = ConstantVector::getSplat(NumElts, StoreVal);
2315          }
2316        }
2317        new StoreInst(StoreVal, EltPtr, MI);
2318        continue;
2319      }
2320      // Otherwise, if we're storing a byte variable, use a memset call for
2321      // this element.
2322    }
2323
2324    unsigned EltSize = DL.getTypeAllocSize(EltTy);
2325    if (!EltSize)
2326      continue;
2327
2328    IRBuilder<> Builder(MI);
2329
2330    // Finally, insert the meminst for this element.
2331    if (isa<MemSetInst>(MI)) {
2332      Builder.CreateMemSet(EltPtr, MI->getArgOperand(1), EltSize,
2333                           MI->isVolatile());
2334    } else {
2335      assert(isa<MemTransferInst>(MI));
2336      Value *Dst = SROADest ? EltPtr : OtherElt;  // Dest ptr
2337      Value *Src = SROADest ? OtherElt : EltPtr;  // Src ptr
2338
2339      if (isa<MemCpyInst>(MI))
2340        Builder.CreateMemCpy(Dst, Src, EltSize, OtherEltAlign,MI->isVolatile());
2341      else
2342        Builder.CreateMemMove(Dst, Src, EltSize,OtherEltAlign,MI->isVolatile());
2343    }
2344  }
2345  DeadInsts.push_back(MI);
2346}
2347
2348/// RewriteStoreUserOfWholeAlloca - We found a store of an integer that
2349/// overwrites the entire allocation.  Extract out the pieces of the stored
2350/// integer and store them individually.
2351void
2352SROA::RewriteStoreUserOfWholeAlloca(StoreInst *SI, AllocaInst *AI,
2353                                    SmallVectorImpl<AllocaInst *> &NewElts) {
2354  // Extract each element out of the integer according to its structure offset
2355  // and store the element value to the individual alloca.
2356  Value *SrcVal = SI->getOperand(0);
2357  Type *AllocaEltTy = AI->getAllocatedType();
2358  const DataLayout &DL = SI->getModule()->getDataLayout();
2359  uint64_t AllocaSizeBits = DL.getTypeAllocSizeInBits(AllocaEltTy);
2360
2361  IRBuilder<> Builder(SI);
2362
2363  // Handle tail padding by extending the operand
2364  if (DL.getTypeSizeInBits(SrcVal->getType()) != AllocaSizeBits)
2365    SrcVal = Builder.CreateZExt(SrcVal,
2366                            IntegerType::get(SI->getContext(), AllocaSizeBits));
2367
2368  DEBUG(dbgs() << "PROMOTING STORE TO WHOLE ALLOCA: " << *AI << '\n' << *SI
2369               << '\n');
2370
2371  // There are two forms here: AI could be an array or struct.  Both cases
2372  // have different ways to compute the element offset.
2373  if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2374    const StructLayout *Layout = DL.getStructLayout(EltSTy);
2375
2376    for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2377      // Get the number of bits to shift SrcVal to get the value.
2378      Type *FieldTy = EltSTy->getElementType(i);
2379      uint64_t Shift = Layout->getElementOffsetInBits(i);
2380
2381      if (DL.isBigEndian())
2382        Shift = AllocaSizeBits - Shift - DL.getTypeAllocSizeInBits(FieldTy);
2383
2384      Value *EltVal = SrcVal;
2385      if (Shift) {
2386        Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2387        EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2388      }
2389
2390      // Truncate down to an integer of the right size.
2391      uint64_t FieldSizeBits = DL.getTypeSizeInBits(FieldTy);
2392
2393      // Ignore zero sized fields like {}, they obviously contain no data.
2394      if (FieldSizeBits == 0) continue;
2395
2396      if (FieldSizeBits != AllocaSizeBits)
2397        EltVal = Builder.CreateTrunc(EltVal,
2398                             IntegerType::get(SI->getContext(), FieldSizeBits));
2399      Value *DestField = NewElts[i];
2400      if (EltVal->getType() == FieldTy) {
2401        // Storing to an integer field of this size, just do it.
2402      } else if (FieldTy->isFloatingPointTy() || FieldTy->isVectorTy()) {
2403        // Bitcast to the right element type (for fp/vector values).
2404        EltVal = Builder.CreateBitCast(EltVal, FieldTy);
2405      } else {
2406        // Otherwise, bitcast the dest pointer (for aggregates).
2407        DestField = Builder.CreateBitCast(DestField,
2408                                     PointerType::getUnqual(EltVal->getType()));
2409      }
2410      new StoreInst(EltVal, DestField, SI);
2411    }
2412
2413  } else {
2414    ArrayType *ATy = cast<ArrayType>(AllocaEltTy);
2415    Type *ArrayEltTy = ATy->getElementType();
2416    uint64_t ElementOffset = DL.getTypeAllocSizeInBits(ArrayEltTy);
2417    uint64_t ElementSizeBits = DL.getTypeSizeInBits(ArrayEltTy);
2418
2419    uint64_t Shift;
2420
2421    if (DL.isBigEndian())
2422      Shift = AllocaSizeBits-ElementOffset;
2423    else
2424      Shift = 0;
2425
2426    for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2427      // Ignore zero sized fields like {}, they obviously contain no data.
2428      if (ElementSizeBits == 0) continue;
2429
2430      Value *EltVal = SrcVal;
2431      if (Shift) {
2432        Value *ShiftVal = ConstantInt::get(EltVal->getType(), Shift);
2433        EltVal = Builder.CreateLShr(EltVal, ShiftVal, "sroa.store.elt");
2434      }
2435
2436      // Truncate down to an integer of the right size.
2437      if (ElementSizeBits != AllocaSizeBits)
2438        EltVal = Builder.CreateTrunc(EltVal,
2439                                     IntegerType::get(SI->getContext(),
2440                                                      ElementSizeBits));
2441      Value *DestField = NewElts[i];
2442      if (EltVal->getType() == ArrayEltTy) {
2443        // Storing to an integer field of this size, just do it.
2444      } else if (ArrayEltTy->isFloatingPointTy() ||
2445                 ArrayEltTy->isVectorTy()) {
2446        // Bitcast to the right element type (for fp/vector values).
2447        EltVal = Builder.CreateBitCast(EltVal, ArrayEltTy);
2448      } else {
2449        // Otherwise, bitcast the dest pointer (for aggregates).
2450        DestField = Builder.CreateBitCast(DestField,
2451                                     PointerType::getUnqual(EltVal->getType()));
2452      }
2453      new StoreInst(EltVal, DestField, SI);
2454
2455      if (DL.isBigEndian())
2456        Shift -= ElementOffset;
2457      else
2458        Shift += ElementOffset;
2459    }
2460  }
2461
2462  DeadInsts.push_back(SI);
2463}
2464
2465/// RewriteLoadUserOfWholeAlloca - We found a load of the entire allocation to
2466/// an integer.  Load the individual pieces to form the aggregate value.
2467void
2468SROA::RewriteLoadUserOfWholeAlloca(LoadInst *LI, AllocaInst *AI,
2469                                   SmallVectorImpl<AllocaInst *> &NewElts) {
2470  // Extract each element out of the NewElts according to its structure offset
2471  // and form the result value.
2472  Type *AllocaEltTy = AI->getAllocatedType();
2473  const DataLayout &DL = LI->getModule()->getDataLayout();
2474  uint64_t AllocaSizeBits = DL.getTypeAllocSizeInBits(AllocaEltTy);
2475
2476  DEBUG(dbgs() << "PROMOTING LOAD OF WHOLE ALLOCA: " << *AI << '\n' << *LI
2477               << '\n');
2478
2479  // There are two forms here: AI could be an array or struct.  Both cases
2480  // have different ways to compute the element offset.
2481  const StructLayout *Layout = nullptr;
2482  uint64_t ArrayEltBitOffset = 0;
2483  if (StructType *EltSTy = dyn_cast<StructType>(AllocaEltTy)) {
2484    Layout = DL.getStructLayout(EltSTy);
2485  } else {
2486    Type *ArrayEltTy = cast<ArrayType>(AllocaEltTy)->getElementType();
2487    ArrayEltBitOffset = DL.getTypeAllocSizeInBits(ArrayEltTy);
2488  }
2489
2490  Value *ResultVal =
2491    Constant::getNullValue(IntegerType::get(LI->getContext(), AllocaSizeBits));
2492
2493  for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
2494    // Load the value from the alloca.  If the NewElt is an aggregate, cast
2495    // the pointer to an integer of the same size before doing the load.
2496    Value *SrcField = NewElts[i];
2497    Type *FieldTy =
2498      cast<PointerType>(SrcField->getType())->getElementType();
2499    uint64_t FieldSizeBits = DL.getTypeSizeInBits(FieldTy);
2500
2501    // Ignore zero sized fields like {}, they obviously contain no data.
2502    if (FieldSizeBits == 0) continue;
2503
2504    IntegerType *FieldIntTy = IntegerType::get(LI->getContext(),
2505                                                     FieldSizeBits);
2506    if (!FieldTy->isIntegerTy() && !FieldTy->isFloatingPointTy() &&
2507        !FieldTy->isVectorTy())
2508      SrcField = new BitCastInst(SrcField,
2509                                 PointerType::getUnqual(FieldIntTy),
2510                                 "", LI);
2511    SrcField = new LoadInst(SrcField, "sroa.load.elt", LI);
2512
2513    // If SrcField is a fp or vector of the right size but that isn't an
2514    // integer type, bitcast to an integer so we can shift it.
2515    if (SrcField->getType() != FieldIntTy)
2516      SrcField = new BitCastInst(SrcField, FieldIntTy, "", LI);
2517
2518    // Zero extend the field to be the same size as the final alloca so that
2519    // we can shift and insert it.
2520    if (SrcField->getType() != ResultVal->getType())
2521      SrcField = new ZExtInst(SrcField, ResultVal->getType(), "", LI);
2522
2523    // Determine the number of bits to shift SrcField.
2524    uint64_t Shift;
2525    if (Layout) // Struct case.
2526      Shift = Layout->getElementOffsetInBits(i);
2527    else  // Array case.
2528      Shift = i*ArrayEltBitOffset;
2529
2530    if (DL.isBigEndian())
2531      Shift = AllocaSizeBits-Shift-FieldIntTy->getBitWidth();
2532
2533    if (Shift) {
2534      Value *ShiftVal = ConstantInt::get(SrcField->getType(), Shift);
2535      SrcField = BinaryOperator::CreateShl(SrcField, ShiftVal, "", LI);
2536    }
2537
2538    // Don't create an 'or x, 0' on the first iteration.
2539    if (!isa<Constant>(ResultVal) ||
2540        !cast<Constant>(ResultVal)->isNullValue())
2541      ResultVal = BinaryOperator::CreateOr(SrcField, ResultVal, "", LI);
2542    else
2543      ResultVal = SrcField;
2544  }
2545
2546  // Handle tail padding by truncating the result
2547  if (DL.getTypeSizeInBits(LI->getType()) != AllocaSizeBits)
2548    ResultVal = new TruncInst(ResultVal, LI->getType(), "", LI);
2549
2550  LI->replaceAllUsesWith(ResultVal);
2551  DeadInsts.push_back(LI);
2552}
2553
2554/// HasPadding - Return true if the specified type has any structure or
2555/// alignment padding in between the elements that would be split apart
2556/// by SROA; return false otherwise.
2557static bool HasPadding(Type *Ty, const DataLayout &DL) {
2558  if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
2559    Ty = ATy->getElementType();
2560    return DL.getTypeSizeInBits(Ty) != DL.getTypeAllocSizeInBits(Ty);
2561  }
2562
2563  // SROA currently handles only Arrays and Structs.
2564  StructType *STy = cast<StructType>(Ty);
2565  const StructLayout *SL = DL.getStructLayout(STy);
2566  unsigned PrevFieldBitOffset = 0;
2567  for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
2568    unsigned FieldBitOffset = SL->getElementOffsetInBits(i);
2569
2570    // Check to see if there is any padding between this element and the
2571    // previous one.
2572    if (i) {
2573      unsigned PrevFieldEnd =
2574        PrevFieldBitOffset+DL.getTypeSizeInBits(STy->getElementType(i-1));
2575      if (PrevFieldEnd < FieldBitOffset)
2576        return true;
2577    }
2578    PrevFieldBitOffset = FieldBitOffset;
2579  }
2580  // Check for tail padding.
2581  if (unsigned EltCount = STy->getNumElements()) {
2582    unsigned PrevFieldEnd = PrevFieldBitOffset +
2583      DL.getTypeSizeInBits(STy->getElementType(EltCount-1));
2584    if (PrevFieldEnd < SL->getSizeInBits())
2585      return true;
2586  }
2587  return false;
2588}
2589
2590/// isSafeStructAllocaToScalarRepl - Check to see if the specified allocation of
2591/// an aggregate can be broken down into elements.  Return 0 if not, 3 if safe,
2592/// or 1 if safe after canonicalization has been performed.
2593bool SROA::isSafeAllocaToScalarRepl(AllocaInst *AI) {
2594  // Loop over the use list of the alloca.  We can only transform it if all of
2595  // the users are safe to transform.
2596  AllocaInfo Info(AI);
2597
2598  isSafeForScalarRepl(AI, 0, Info);
2599  if (Info.isUnsafe) {
2600    DEBUG(dbgs() << "Cannot transform: " << *AI << '\n');
2601    return false;
2602  }
2603
2604  const DataLayout &DL = AI->getModule()->getDataLayout();
2605
2606  // Okay, we know all the users are promotable.  If the aggregate is a memcpy
2607  // source and destination, we have to be careful.  In particular, the memcpy
2608  // could be moving around elements that live in structure padding of the LLVM
2609  // types, but may actually be used.  In these cases, we refuse to promote the
2610  // struct.
2611  if (Info.isMemCpySrc && Info.isMemCpyDst &&
2612      HasPadding(AI->getAllocatedType(), DL))
2613    return false;
2614
2615  // If the alloca never has an access to just *part* of it, but is accessed
2616  // via loads and stores, then we should use ConvertToScalarInfo to promote
2617  // the alloca instead of promoting each piece at a time and inserting fission
2618  // and fusion code.
2619  if (!Info.hasSubelementAccess && Info.hasALoadOrStore) {
2620    // If the struct/array just has one element, use basic SRoA.
2621    if (StructType *ST = dyn_cast<StructType>(AI->getAllocatedType())) {
2622      if (ST->getNumElements() > 1) return false;
2623    } else {
2624      if (cast<ArrayType>(AI->getAllocatedType())->getNumElements() > 1)
2625        return false;
2626    }
2627  }
2628
2629  return true;
2630}
2631