<commit_before>//===- MemCpyOptimizer.cpp - Optimize use of memcpy and friends -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs various transformations related to eliminating memcpy
// calls, or transforming sets of stores into memset's.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "memcpyopt"
#include "llvm/Transforms/Scalar.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IRBuilder.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
#include <list>
using namespace llvm;

STATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted");
STATISTIC(NumMemSetInfer, "Number of memsets inferred");
STATISTIC(NumMoveToCpy,   "Number of memmoves converted to memcpy");
STATISTIC(NumCpyToSet,    "Number of memcpys converted to memset");

static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
                                  bool &VariableIdxFound, const TargetData &TD){
  // Skip over the first indices.
  gep_type_iterator GTI = gep_type_begin(GEP);
  for (unsigned i = 1; i != Idx; ++i, ++GTI)
    /*skip along*/;

  // Compute the offset implied by the rest of the indices.
  int64_t Offset = 0;
  for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
    ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
    if (OpC == 0)
      return VariableIdxFound = true;
    if (OpC->isZero()) continue;  // No offset.

    // Handle struct indices, which add their field offset to the pointer.
    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
      Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
      continue;
    }

    // Otherwise, we have a sequential type like an array or vector.  Multiply
    // the index by the ElementSize.
    uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
    Offset += Size*OpC->getSExtValue();
  }

  return Offset;
}

/// IsPointerOffset - Return true if Ptr1 is provably equal to Ptr2 plus a
/// constant offset, and return that constant offset.  For example, Ptr1 might
/// be &A[42], and Ptr2 might be &A[40].  In this case offset would be -8.
static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
                            const TargetData &TD) {
  Ptr1 = Ptr1->stripPointerCasts();
  Ptr2 = Ptr2->stripPointerCasts();
  GEPOperator *GEP1 = dyn_cast<GEPOperator>(Ptr1);
  GEPOperator *GEP2 = dyn_cast<GEPOperator>(Ptr2);

  bool VariableIdxFound = false;

  // If one pointer is a GEP and the other isn't, then see if the GEP is a
  // constant offset from the base, as in "P" and "gep P, 1".
  if (GEP1 && GEP2 == 0 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) {
    Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, TD);
    return !VariableIdxFound;
  }

  if (GEP2 && GEP1 == 0 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) {
    Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, TD);
    return !VariableIdxFound;
  }

  // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
  // base.  After that base, they may have some number of common (and
  // potentially variable) indices.  After that they handle some constant
  // offset, which determines their offset from each other.  At this point, we
  // handle no other case.
  if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
    return false;

  // Skip any common indices and track the GEP types.
  unsigned Idx = 1;
  for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
    if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx))
      break;

  int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD);
  int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD);
  if (VariableIdxFound) return false;

  Offset = Offset2-Offset1;
  return true;
}


/// MemsetRange - Represents a range of memset'd bytes with the ByteVal value.
/// This allows us to analyze stores like:
///   store 0 -> P+1
///   store 0 -> P+0
///   store 0 -> P+3
///   store 0 -> P+2
/// which sometimes happens with stores to arrays of structs etc.  When we see
/// the first store, we make a range [1, 2).  The second store extends the range
/// to [0, 2).  The third makes a new range [2, 3).  The fourth store joins the
/// two ranges into [0, 3) which is memset'able.
namespace {
struct MemsetRange {
  // Start/End - A semi range that describes the span that this range covers.
  // The range is closed at the start and open at the end: [Start, End).
  int64_t Start, End;

  /// StartPtr - The getelementptr instruction that points to the start of the
  /// range.
  Value *StartPtr;

  /// Alignment - The known alignment of the first store.
  unsigned Alignment;

  /// TheStores - The actual stores that make up this range.
  SmallVector<Instruction*, 16> TheStores;

  bool isProfitableToUseMemset(const TargetData &TD) const;

};
} // end anon namespace

bool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const {
  // If we found more than 4 stores to merge or 16 bytes, use memset.
  if (TheStores.size() >= 4 || End-Start >= 16) return true;

  // If there is nothing to merge, don't do anything.
  if (TheStores.size() < 2) return false;

  // If any of the stores are a memset, then it is always good to extend the
  // memset.
  for (unsigned i = 0, e = TheStores.size(); i != e; ++i)
    if (!isa<StoreInst>(TheStores[i]))
      return true;

  // Assume that the code generator is capable of merging pairs of stores
  // together if it wants to.
  if (TheStores.size() == 2) return false;

  // If we have fewer than 8 stores, it can still be worthwhile to do this.
  // For example, merging 4 i8 stores into an i32 store is useful almost always.
  // However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the
  // memset will be split into 2 32-bit stores anyway) and doing so can
  // pessimize the llvm optimizer.
  //
  // Since we don't have perfect knowledge here, make some assumptions: assume
  // the maximum GPR width is the same size as the pointer size and assume that
  // this width can be stored.  If so, check to see whether we will end up
  // actually reducing the number of stores used.
  unsigned Bytes = unsigned(End-Start);
  unsigned NumPointerStores = Bytes/TD.getPointerSize();

  // Assume the remaining bytes if any are done a byte at a time.
  unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize();

  // If we will reduce the # stores (according to this heuristic), do the
  // transformation.  This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32
  // etc.
  return TheStores.size() > NumPointerStores+NumByteStores;
}


namespace {
class MemsetRanges {
  /// Ranges - A sorted list of the memset ranges.  We use std::list here
  /// because each element is relatively large and expensive to copy.
  std::list<MemsetRange> Ranges;
  typedef std::list<MemsetRange>::iterator range_iterator;
  const TargetData &TD;
public:
  MemsetRanges(const TargetData &td) : TD(td) {}

  typedef std::list<MemsetRange>::const_iterator const_iterator;
  const_iterator begin() const { return Ranges.begin(); }
  const_iterator end() const { return Ranges.end(); }
  bool empty() const { return Ranges.empty(); }

  void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
    if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
      addStore(OffsetFromFirst, SI);
    else
      addMemSet(OffsetFromFirst, cast<MemSetInst>(Inst));
  }

  void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
    int64_t StoreSize = TD.getTypeStoreSize(SI->getOperand(0)->getType());

    addRange(OffsetFromFirst, StoreSize,
             SI->getPointerOperand(), SI->getAlignment(), SI);
  }

  void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
    int64_t Size = cast<ConstantInt>(MSI->getLength())->getZExtValue();
    addRange(OffsetFromFirst, Size, MSI->getDest(), MSI->getAlignment(), MSI);
  }

  void addRange(int64_t Start, int64_t Size, Value *Ptr,
                unsigned Alignment, Instruction *Inst);

};

} // end anon namespace


/// addRange - Add a new store to the MemsetRanges data structure.  This adds a
/// new range for the specified store at the specified offset, merging into
/// existing ranges as appropriate.
///
/// Do a linear search of the ranges to see if this can be joined and/or to
/// find the insertion point in the list.  We keep the ranges sorted for
/// simplicity here.  This is a linear search of a linked list, which is ugly,
/// however the number of ranges is limited, so this won't get crazy slow.
void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
                            unsigned Alignment, Instruction *Inst) {
  int64_t End = Start+Size;
  range_iterator I = Ranges.begin(), E = Ranges.end();

  while (I != E && Start > I->End)
    ++I;

  // We now know that I == E, in which case we didn't find anything to merge
  // with, or that Start <= I->End.  If End < I->Start or I == E, then we need
  // to insert a new range.  Handle this now.
  if (I == E || End < I->Start) {
    MemsetRange &R = *Ranges.insert(I, MemsetRange());
    R.Start        = Start;
    R.End          = End;
    R.StartPtr     = Ptr;
    R.Alignment    = Alignment;
    R.TheStores.push_back(Inst);
    return;
  }

  // This store overlaps with I, add it.
  I->TheStores.push_back(Inst);

  // At this point, we may have an interval that completely contains our store.
  // If so, just add it to the interval and return.
  if (I->Start <= Start && I->End >= End)
    return;

  // Now we know that Start <= I->End and End >= I->Start so the range overlaps
  // but is not entirely contained within the range.

  // See if the range extends the start of the range.  In this case, it couldn't
  // possibly cause it to join the prior range, because otherwise we would have
  // stopped on *it*.
  if (Start < I->Start) {
    I->Start = Start;
    I->StartPtr = Ptr;
    I->Alignment = Alignment;
  }

  // Now we know that Start <= I->End and Start >= I->Start (so the startpoint
  // is in or right at the end of I), and that End >= I->Start.  Extend I out to
  // End.
  if (End > I->End) {
    I->End = End;
    range_iterator NextI = I;
    while (++NextI != E && End >= NextI->Start) {
      // Merge the range in.
      I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end());
      if (NextI->End > I->End)
        I->End = NextI->End;
      Ranges.erase(NextI);
      NextI = I;
    }
  }
}

//===----------------------------------------------------------------------===//
//                         MemCpyOpt Pass
//===----------------------------------------------------------------------===//

namespace {
  class MemCpyOpt : public FunctionPass {
    MemoryDependenceAnalysis *MD;
    TargetLibraryInfo *TLI;
    const TargetData *TD;
  public:
    static char ID; // Pass identification, replacement for typeid
    MemCpyOpt() : FunctionPass(ID) {
      initializeMemCpyOptPass(*PassRegistry::getPassRegistry());
      MD = 0;
      TLI = 0;
      TD = 0;
    }

    bool runOnFunction(Function &F);

  private:
    // This transformation requires dominator postdominator info
    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
      AU.setPreservesCFG();
      AU.addRequired<DominatorTree>();
      AU.addRequired<MemoryDependenceAnalysis>();
      AU.addRequired<AliasAnalysis>();
      AU.addRequired<TargetLibraryInfo>();
      AU.addPreserved<AliasAnalysis>();
      AU.addPreserved<MemoryDependenceAnalysis>();
    }

    // Helper fuctions
    bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
    bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
    bool processMemCpy(MemCpyInst *M);
    bool processMemMove(MemMoveInst *M);
    bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
                              uint64_t cpyLen, unsigned cpyAlign, CallInst *C);
    bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
                                       uint64_t MSize);
    bool processByValArgument(CallSite CS, unsigned ArgNo);
    Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
                                      Value *ByteVal);

    bool iterateOnFunction(Function &F);
  };

  char MemCpyOpt::ID = 0;
}

// createMemCpyOptPass - The public interface to this file...
FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); }

INITIALIZE_PASS_BEGIN(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
                      false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
                    false, false)

/// tryMergingIntoMemset - When scanning forward over instructions, we look for
/// some other patterns to fold away.  In particular, this looks for stores to
/// neighboring locations of memory.  If it sees enough consecutive ones, it
/// attempts to merge them together into a memcpy/memset.
Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
                                             Value *StartPtr, Value *ByteVal) {
  if (TD == 0) return 0;

  // Okay, so we now have a single store that can be splatable.  Scan to find
  // all subsequent stores of the same value to offset from the same pointer.
  // Join these together into ranges, so we can decide whether contiguous blocks
  // are stored.
  MemsetRanges Ranges(*TD);

  BasicBlock::iterator BI = StartInst;
  for (++BI; !isa<TerminatorInst>(BI); ++BI) {
    if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
      // If the instruction is readnone, ignore it, otherwise bail out.  We
      // don't even allow readonly here because we don't want something like:
      // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
      if (BI->mayWriteToMemory() || BI->mayReadFromMemory())
        break;
      continue;
    }

    if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
      // If this is a store, see if we can merge it in.
      if (!NextStore->isSimple()) break;

      // Check to see if this stored value is of the same byte-splattable value.
      if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
        break;

      // Check to see if this store is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(),
                           Offset, *TD))
        break;

      Ranges.addStore(Offset, NextStore);
    } else {
      MemSetInst *MSI = cast<MemSetInst>(BI);

      if (MSI->isVolatile() || ByteVal != MSI->getValue() ||
          !isa<ConstantInt>(MSI->getLength()))
        break;

      // Check to see if this store is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, MSI->getDest(), Offset, *TD))
        break;

      Ranges.addMemSet(Offset, MSI);
    }
  }

  // If we have no ranges, then we just had a single store with nothing that
  // could be merged in.  This is a very common case of course.
  if (Ranges.empty())
    return 0;

  // If we had at least one store that could be merged in, add the starting
  // store as well.  We try to avoid this unless there is at least something
  // interesting as a small compile-time optimization.
  Ranges.addInst(0, StartInst);

  // If we create any memsets, we put it right before the first instruction that
  // isn't part of the memset block.  This ensure that the memset is dominated
  // by any addressing instruction needed by the start of the block.
  IRBuilder<> Builder(BI);

  // Now that we have full information about ranges, loop over the ranges and
  // emit memset's for anything big enough to be worthwhile.
  Instruction *AMemSet = 0;
  for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
       I != E; ++I) {
    const MemsetRange &Range = *I;

    if (Range.TheStores.size() == 1) continue;

    // If it is profitable to lower this range to memset, do so now.
    if (!Range.isProfitableToUseMemset(*TD))
      continue;

    // Otherwise, we do want to transform this!  Create a new memset.
    // Get the starting pointer of the block.
    StartPtr = Range.StartPtr;

    // Determine alignment
    unsigned Alignment = Range.Alignment;
    if (Alignment == 0) {
      Type *EltType =
        cast<PointerType>(StartPtr->getType())->getElementType();
      Alignment = TD->getABITypeAlignment(EltType);
    }

    AMemSet =
      Builder.CreateMemSet(StartPtr, ByteVal, Range.End-Range.Start, Alignment);

    DEBUG(dbgs() << "Replace stores:\n";
          for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i)
            dbgs() << *Range.TheStores[i] << '\n';
          dbgs() << "With: " << *AMemSet << '\n');

    if (!Range.TheStores.empty())
      AMemSet->setDebugLoc(Range.TheStores[0]->getDebugLoc());

    // Zap all the stores.
    for (SmallVector<Instruction*, 16>::const_iterator
         SI = Range.TheStores.begin(),
         SE = Range.TheStores.end(); SI != SE; ++SI) {
      MD->removeInstruction(*SI);
      (*SI)->eraseFromParent();
    }
    ++NumMemSetInfer;
  }

  return AMemSet;
}


bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
  if (!SI->isSimple()) return false;

  if (TD == 0) return false;

  // Detect cases where we're performing call slot forwarding, but
  // happen to be using a load-store pair to implement it, rather than
  // a memcpy.
  if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
    if (LI->isSimple() && LI->hasOneUse() &&
        LI->getParent() == SI->getParent()) {
      MemDepResult ldep = MD->getDependency(LI);
      CallInst *C = 0;
      if (ldep.isClobber() && !isa<MemCpyInst>(ldep.getInst()))
        C = dyn_cast<CallInst>(ldep.getInst());

      if (C) {
        // Check that nothing touches the dest of the "copy" between
        // the call and the store.
        AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
        AliasAnalysis::Location StoreLoc = AA.getLocation(SI);
        for (BasicBlock::iterator I = --BasicBlock::iterator(SI),
                                  E = C; I != E; --I) {
          if (AA.getModRefInfo(&*I, StoreLoc) != AliasAnalysis::NoModRef) {
            C = 0;
            break;
          }
        }
      }

      if (C) {
        unsigned storeAlign = SI->getAlignment();
        if (!storeAlign)
          storeAlign = TD->getABITypeAlignment(SI->getOperand(0)->getType());
        unsigned loadAlign = LI->getAlignment();
        if (!loadAlign)
          loadAlign = TD->getABITypeAlignment(LI->getType());

        bool changed = performCallSlotOptzn(LI,
                        SI->getPointerOperand()->stripPointerCasts(),
                        LI->getPointerOperand()->stripPointerCasts(),
                        TD->getTypeStoreSize(SI->getOperand(0)->getType()),
                        std::min(storeAlign, loadAlign), C);
        if (changed) {
          MD->removeInstruction(SI);
          SI->eraseFromParent();
          MD->removeInstruction(LI);
          LI->eraseFromParent();
          ++NumMemCpyInstr;
          return true;
        }
      }
    }
  }

  // There are two cases that are interesting for this code to handle: memcpy
  // and memset.  Right now we only handle memset.

  // Ensure that the value being stored is something that can be memset'able a
  // byte at a time like "0" or "-1" or any width, as well as things like
  // 0xA0A0A0A0 and 0.0.
  if (Value *ByteVal = isBytewiseValue(SI->getOperand(0)))
    if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
                                              ByteVal)) {
      BBI = I;  // Don't invalidate iterator.
      return true;
    }

  return false;
}

bool MemCpyOpt::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
  // See if there is another memset or store neighboring this memset which
  // allows us to widen out the memset to do a single larger store.
  if (isa<ConstantInt>(MSI->getLength()) && !MSI->isVolatile())
    if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
                                              MSI->getValue())) {
      BBI = I;  // Don't invalidate iterator.
      return true;
    }
  return false;
}


/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
/// the call write its result directly into the destination of the memcpy.
bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
                                     Value *cpyDest, Value *cpySrc,
                                     uint64_t cpyLen, unsigned cpyAlign,
                                     CallInst *C) {
  // The general transformation to keep in mind is
  //
  //   call @func(..., src, ...)
  //   memcpy(dest, src, ...)
  //
  // ->
  //
  //   memcpy(dest, src, ...)
  //   call @func(..., dest, ...)
  //
  // Since moving the memcpy is technically awkward, we additionally check that
  // src only holds uninitialized values at the moment of the call, meaning that
  // the memcpy can be discarded rather than moved.

  // Deliberately get the source and destination with bitcasts stripped away,
  // because we'll need to do type comparisons based on the underlying type.
  CallSite CS(C);

  // Require that src be an alloca.  This simplifies the reasoning considerably.
  AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
  if (!srcAlloca)
    return false;

  // Check that all of src is copied to dest.
  if (TD == 0) return false;

  ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
  if (!srcArraySize)
    return false;

  uint64_t srcSize = TD->getTypeAllocSize(srcAlloca->getAllocatedType()) *
    srcArraySize->getZExtValue();

  if (cpyLen < srcSize)
    return false;

  // Check that dest points to memory that is at least as aligned as src.
  unsigned srcAlign = srcAlloca->getAlignment();
  if (!srcAlign)
    srcAlign = TD->getABITypeAlignment(srcAlloca->getAllocatedType());
  bool isDestSufficientlyAligned = srcAlign <= cpyAlign;
  // If dest is not aligned enough and we can't increase its alignment then
  // bail out.
  if (!isDestSufficientlyAligned && !isa<AllocaInst>(cpyDest))
    return false;

  // Check that accessing the first srcSize bytes of dest will not cause a
  // trap.  Otherwise the transform is invalid since it might cause a trap
  // to occur earlier than it otherwise would.
  if (AllocaInst *A = dyn_cast<AllocaInst>(cpyDest)) {
    // The destination is an alloca.  Check it is larger than srcSize.
    ConstantInt *destArraySize = dyn_cast<ConstantInt>(A->getArraySize());
    if (!destArraySize)
      return false;

    uint64_t destSize = TD->getTypeAllocSize(A->getAllocatedType()) *
      destArraySize->getZExtValue();

    if (destSize < srcSize)
      return false;
  } else if (Argument *A = dyn_cast<Argument>(cpyDest)) {
    // If the destination is an sret parameter then only accesses that are
    // outside of the returned struct type can trap.
    if (!A->hasStructRetAttr())
      return false;

    Type *StructTy = cast<PointerType>(A->getType())->getElementType();
    uint64_t destSize = TD->getTypeAllocSize(StructTy);

    if (destSize < srcSize)
      return false;
  } else {
    return false;
  }

  // Check that src is not accessed except via the call and the memcpy.  This
  // guarantees that it holds only undefined values when passed in (so the final
  // memcpy can be dropped), that it is not read or written between the call and
  // the memcpy, and that writing beyond the end of it is undefined.
  SmallVector<User*, 8> srcUseList(srcAlloca->use_begin(),
                                   srcAlloca->use_end());
  while (!srcUseList.empty()) {
    User *UI = srcUseList.pop_back_val();

    if (isa<BitCastInst>(UI)) {
      for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
           I != E; ++I)
        srcUseList.push_back(*I);
    } else if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(UI)) {
      if (G->hasAllZeroIndices())
        for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
             I != E; ++I)
          srcUseList.push_back(*I);
      else
        return false;<commit_msg>Move this test a bit later, after the point at which we know that we either have an alloca or a parameter, since then the alloca test should make sense to readers, while before it probably appears too specific.  No functionality change.<commit_after>//===- MemCpyOptimizer.cpp - Optimize use of memcpy and friends -----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs various transformations related to eliminating memcpy
// calls, or transforming sets of stores into memset's.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "memcpyopt"
#include "llvm/Transforms/Scalar.h"
#include "llvm/GlobalVariable.h"
#include "llvm/IRBuilder.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Transforms/Utils/Local.h"
#include <list>
using namespace llvm;

STATISTIC(NumMemCpyInstr, "Number of memcpy instructions deleted");
STATISTIC(NumMemSetInfer, "Number of memsets inferred");
STATISTIC(NumMoveToCpy,   "Number of memmoves converted to memcpy");
STATISTIC(NumCpyToSet,    "Number of memcpys converted to memset");

static int64_t GetOffsetFromIndex(const GEPOperator *GEP, unsigned Idx,
                                  bool &VariableIdxFound, const TargetData &TD){
  // Skip over the first indices.
  gep_type_iterator GTI = gep_type_begin(GEP);
  for (unsigned i = 1; i != Idx; ++i, ++GTI)
    /*skip along*/;

  // Compute the offset implied by the rest of the indices.
  int64_t Offset = 0;
  for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
    ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
    if (OpC == 0)
      return VariableIdxFound = true;
    if (OpC->isZero()) continue;  // No offset.

    // Handle struct indices, which add their field offset to the pointer.
    if (StructType *STy = dyn_cast<StructType>(*GTI)) {
      Offset += TD.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
      continue;
    }

    // Otherwise, we have a sequential type like an array or vector.  Multiply
    // the index by the ElementSize.
    uint64_t Size = TD.getTypeAllocSize(GTI.getIndexedType());
    Offset += Size*OpC->getSExtValue();
  }

  return Offset;
}

/// IsPointerOffset - Return true if Ptr1 is provably equal to Ptr2 plus a
/// constant offset, and return that constant offset.  For example, Ptr1 might
/// be &A[42], and Ptr2 might be &A[40].  In this case offset would be -8.
static bool IsPointerOffset(Value *Ptr1, Value *Ptr2, int64_t &Offset,
                            const TargetData &TD) {
  Ptr1 = Ptr1->stripPointerCasts();
  Ptr2 = Ptr2->stripPointerCasts();
  GEPOperator *GEP1 = dyn_cast<GEPOperator>(Ptr1);
  GEPOperator *GEP2 = dyn_cast<GEPOperator>(Ptr2);

  bool VariableIdxFound = false;

  // If one pointer is a GEP and the other isn't, then see if the GEP is a
  // constant offset from the base, as in "P" and "gep P, 1".
  if (GEP1 && GEP2 == 0 && GEP1->getOperand(0)->stripPointerCasts() == Ptr2) {
    Offset = -GetOffsetFromIndex(GEP1, 1, VariableIdxFound, TD);
    return !VariableIdxFound;
  }

  if (GEP2 && GEP1 == 0 && GEP2->getOperand(0)->stripPointerCasts() == Ptr1) {
    Offset = GetOffsetFromIndex(GEP2, 1, VariableIdxFound, TD);
    return !VariableIdxFound;
  }

  // Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
  // base.  After that base, they may have some number of common (and
  // potentially variable) indices.  After that they handle some constant
  // offset, which determines their offset from each other.  At this point, we
  // handle no other case.
  if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
    return false;

  // Skip any common indices and track the GEP types.
  unsigned Idx = 1;
  for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
    if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx))
      break;

  int64_t Offset1 = GetOffsetFromIndex(GEP1, Idx, VariableIdxFound, TD);
  int64_t Offset2 = GetOffsetFromIndex(GEP2, Idx, VariableIdxFound, TD);
  if (VariableIdxFound) return false;

  Offset = Offset2-Offset1;
  return true;
}


/// MemsetRange - Represents a range of memset'd bytes with the ByteVal value.
/// This allows us to analyze stores like:
///   store 0 -> P+1
///   store 0 -> P+0
///   store 0 -> P+3
///   store 0 -> P+2
/// which sometimes happens with stores to arrays of structs etc.  When we see
/// the first store, we make a range [1, 2).  The second store extends the range
/// to [0, 2).  The third makes a new range [2, 3).  The fourth store joins the
/// two ranges into [0, 3) which is memset'able.
namespace {
struct MemsetRange {
  // Start/End - A semi range that describes the span that this range covers.
  // The range is closed at the start and open at the end: [Start, End).
  int64_t Start, End;

  /// StartPtr - The getelementptr instruction that points to the start of the
  /// range.
  Value *StartPtr;

  /// Alignment - The known alignment of the first store.
  unsigned Alignment;

  /// TheStores - The actual stores that make up this range.
  SmallVector<Instruction*, 16> TheStores;

  bool isProfitableToUseMemset(const TargetData &TD) const;

};
} // end anon namespace

bool MemsetRange::isProfitableToUseMemset(const TargetData &TD) const {
  // If we found more than 4 stores to merge or 16 bytes, use memset.
  if (TheStores.size() >= 4 || End-Start >= 16) return true;

  // If there is nothing to merge, don't do anything.
  if (TheStores.size() < 2) return false;

  // If any of the stores are a memset, then it is always good to extend the
  // memset.
  for (unsigned i = 0, e = TheStores.size(); i != e; ++i)
    if (!isa<StoreInst>(TheStores[i]))
      return true;

  // Assume that the code generator is capable of merging pairs of stores
  // together if it wants to.
  if (TheStores.size() == 2) return false;

  // If we have fewer than 8 stores, it can still be worthwhile to do this.
  // For example, merging 4 i8 stores into an i32 store is useful almost always.
  // However, merging 2 32-bit stores isn't useful on a 32-bit architecture (the
  // memset will be split into 2 32-bit stores anyway) and doing so can
  // pessimize the llvm optimizer.
  //
  // Since we don't have perfect knowledge here, make some assumptions: assume
  // the maximum GPR width is the same size as the pointer size and assume that
  // this width can be stored.  If so, check to see whether we will end up
  // actually reducing the number of stores used.
  unsigned Bytes = unsigned(End-Start);
  unsigned NumPointerStores = Bytes/TD.getPointerSize();

  // Assume the remaining bytes if any are done a byte at a time.
  unsigned NumByteStores = Bytes - NumPointerStores*TD.getPointerSize();

  // If we will reduce the # stores (according to this heuristic), do the
  // transformation.  This encourages merging 4 x i8 -> i32 and 2 x i16 -> i32
  // etc.
  return TheStores.size() > NumPointerStores+NumByteStores;
}


namespace {
class MemsetRanges {
  /// Ranges - A sorted list of the memset ranges.  We use std::list here
  /// because each element is relatively large and expensive to copy.
  std::list<MemsetRange> Ranges;
  typedef std::list<MemsetRange>::iterator range_iterator;
  const TargetData &TD;
public:
  MemsetRanges(const TargetData &td) : TD(td) {}

  typedef std::list<MemsetRange>::const_iterator const_iterator;
  const_iterator begin() const { return Ranges.begin(); }
  const_iterator end() const { return Ranges.end(); }
  bool empty() const { return Ranges.empty(); }

  void addInst(int64_t OffsetFromFirst, Instruction *Inst) {
    if (StoreInst *SI = dyn_cast<StoreInst>(Inst))
      addStore(OffsetFromFirst, SI);
    else
      addMemSet(OffsetFromFirst, cast<MemSetInst>(Inst));
  }

  void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
    int64_t StoreSize = TD.getTypeStoreSize(SI->getOperand(0)->getType());

    addRange(OffsetFromFirst, StoreSize,
             SI->getPointerOperand(), SI->getAlignment(), SI);
  }

  void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
    int64_t Size = cast<ConstantInt>(MSI->getLength())->getZExtValue();
    addRange(OffsetFromFirst, Size, MSI->getDest(), MSI->getAlignment(), MSI);
  }

  void addRange(int64_t Start, int64_t Size, Value *Ptr,
                unsigned Alignment, Instruction *Inst);

};

} // end anon namespace


/// addRange - Add a new store to the MemsetRanges data structure.  This adds a
/// new range for the specified store at the specified offset, merging into
/// existing ranges as appropriate.
///
/// Do a linear search of the ranges to see if this can be joined and/or to
/// find the insertion point in the list.  We keep the ranges sorted for
/// simplicity here.  This is a linear search of a linked list, which is ugly,
/// however the number of ranges is limited, so this won't get crazy slow.
void MemsetRanges::addRange(int64_t Start, int64_t Size, Value *Ptr,
                            unsigned Alignment, Instruction *Inst) {
  int64_t End = Start+Size;
  range_iterator I = Ranges.begin(), E = Ranges.end();

  while (I != E && Start > I->End)
    ++I;

  // We now know that I == E, in which case we didn't find anything to merge
  // with, or that Start <= I->End.  If End < I->Start or I == E, then we need
  // to insert a new range.  Handle this now.
  if (I == E || End < I->Start) {
    MemsetRange &R = *Ranges.insert(I, MemsetRange());
    R.Start        = Start;
    R.End          = End;
    R.StartPtr     = Ptr;
    R.Alignment    = Alignment;
    R.TheStores.push_back(Inst);
    return;
  }

  // This store overlaps with I, add it.
  I->TheStores.push_back(Inst);

  // At this point, we may have an interval that completely contains our store.
  // If so, just add it to the interval and return.
  if (I->Start <= Start && I->End >= End)
    return;

  // Now we know that Start <= I->End and End >= I->Start so the range overlaps
  // but is not entirely contained within the range.

  // See if the range extends the start of the range.  In this case, it couldn't
  // possibly cause it to join the prior range, because otherwise we would have
  // stopped on *it*.
  if (Start < I->Start) {
    I->Start = Start;
    I->StartPtr = Ptr;
    I->Alignment = Alignment;
  }

  // Now we know that Start <= I->End and Start >= I->Start (so the startpoint
  // is in or right at the end of I), and that End >= I->Start.  Extend I out to
  // End.
  if (End > I->End) {
    I->End = End;
    range_iterator NextI = I;
    while (++NextI != E && End >= NextI->Start) {
      // Merge the range in.
      I->TheStores.append(NextI->TheStores.begin(), NextI->TheStores.end());
      if (NextI->End > I->End)
        I->End = NextI->End;
      Ranges.erase(NextI);
      NextI = I;
    }
  }
}

//===----------------------------------------------------------------------===//
//                         MemCpyOpt Pass
//===----------------------------------------------------------------------===//

namespace {
  class MemCpyOpt : public FunctionPass {
    MemoryDependenceAnalysis *MD;
    TargetLibraryInfo *TLI;
    const TargetData *TD;
  public:
    static char ID; // Pass identification, replacement for typeid
    MemCpyOpt() : FunctionPass(ID) {
      initializeMemCpyOptPass(*PassRegistry::getPassRegistry());
      MD = 0;
      TLI = 0;
      TD = 0;
    }

    bool runOnFunction(Function &F);

  private:
    // This transformation requires dominator postdominator info
    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
      AU.setPreservesCFG();
      AU.addRequired<DominatorTree>();
      AU.addRequired<MemoryDependenceAnalysis>();
      AU.addRequired<AliasAnalysis>();
      AU.addRequired<TargetLibraryInfo>();
      AU.addPreserved<AliasAnalysis>();
      AU.addPreserved<MemoryDependenceAnalysis>();
    }

    // Helper fuctions
    bool processStore(StoreInst *SI, BasicBlock::iterator &BBI);
    bool processMemSet(MemSetInst *SI, BasicBlock::iterator &BBI);
    bool processMemCpy(MemCpyInst *M);
    bool processMemMove(MemMoveInst *M);
    bool performCallSlotOptzn(Instruction *cpy, Value *cpyDst, Value *cpySrc,
                              uint64_t cpyLen, unsigned cpyAlign, CallInst *C);
    bool processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
                                       uint64_t MSize);
    bool processByValArgument(CallSite CS, unsigned ArgNo);
    Instruction *tryMergingIntoMemset(Instruction *I, Value *StartPtr,
                                      Value *ByteVal);

    bool iterateOnFunction(Function &F);
  };

  char MemCpyOpt::ID = 0;
}

// createMemCpyOptPass - The public interface to this file...
FunctionPass *llvm::createMemCpyOptPass() { return new MemCpyOpt(); }

INITIALIZE_PASS_BEGIN(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
                      false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTree)
INITIALIZE_PASS_DEPENDENCY(MemoryDependenceAnalysis)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(MemCpyOpt, "memcpyopt", "MemCpy Optimization",
                    false, false)

/// tryMergingIntoMemset - When scanning forward over instructions, we look for
/// some other patterns to fold away.  In particular, this looks for stores to
/// neighboring locations of memory.  If it sees enough consecutive ones, it
/// attempts to merge them together into a memcpy/memset.
Instruction *MemCpyOpt::tryMergingIntoMemset(Instruction *StartInst,
                                             Value *StartPtr, Value *ByteVal) {
  if (TD == 0) return 0;

  // Okay, so we now have a single store that can be splatable.  Scan to find
  // all subsequent stores of the same value to offset from the same pointer.
  // Join these together into ranges, so we can decide whether contiguous blocks
  // are stored.
  MemsetRanges Ranges(*TD);

  BasicBlock::iterator BI = StartInst;
  for (++BI; !isa<TerminatorInst>(BI); ++BI) {
    if (!isa<StoreInst>(BI) && !isa<MemSetInst>(BI)) {
      // If the instruction is readnone, ignore it, otherwise bail out.  We
      // don't even allow readonly here because we don't want something like:
      // A[1] = 2; strlen(A); A[2] = 2; -> memcpy(A, ...); strlen(A).
      if (BI->mayWriteToMemory() || BI->mayReadFromMemory())
        break;
      continue;
    }

    if (StoreInst *NextStore = dyn_cast<StoreInst>(BI)) {
      // If this is a store, see if we can merge it in.
      if (!NextStore->isSimple()) break;

      // Check to see if this stored value is of the same byte-splattable value.
      if (ByteVal != isBytewiseValue(NextStore->getOperand(0)))
        break;

      // Check to see if this store is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, NextStore->getPointerOperand(),
                           Offset, *TD))
        break;

      Ranges.addStore(Offset, NextStore);
    } else {
      MemSetInst *MSI = cast<MemSetInst>(BI);

      if (MSI->isVolatile() || ByteVal != MSI->getValue() ||
          !isa<ConstantInt>(MSI->getLength()))
        break;

      // Check to see if this store is to a constant offset from the start ptr.
      int64_t Offset;
      if (!IsPointerOffset(StartPtr, MSI->getDest(), Offset, *TD))
        break;

      Ranges.addMemSet(Offset, MSI);
    }
  }

  // If we have no ranges, then we just had a single store with nothing that
  // could be merged in.  This is a very common case of course.
  if (Ranges.empty())
    return 0;

  // If we had at least one store that could be merged in, add the starting
  // store as well.  We try to avoid this unless there is at least something
  // interesting as a small compile-time optimization.
  Ranges.addInst(0, StartInst);

  // If we create any memsets, we put it right before the first instruction that
  // isn't part of the memset block.  This ensure that the memset is dominated
  // by any addressing instruction needed by the start of the block.
  IRBuilder<> Builder(BI);

  // Now that we have full information about ranges, loop over the ranges and
  // emit memset's for anything big enough to be worthwhile.
  Instruction *AMemSet = 0;
  for (MemsetRanges::const_iterator I = Ranges.begin(), E = Ranges.end();
       I != E; ++I) {
    const MemsetRange &Range = *I;

    if (Range.TheStores.size() == 1) continue;

    // If it is profitable to lower this range to memset, do so now.
    if (!Range.isProfitableToUseMemset(*TD))
      continue;

    // Otherwise, we do want to transform this!  Create a new memset.
    // Get the starting pointer of the block.
    StartPtr = Range.StartPtr;

    // Determine alignment
    unsigned Alignment = Range.Alignment;
    if (Alignment == 0) {
      Type *EltType =
        cast<PointerType>(StartPtr->getType())->getElementType();
      Alignment = TD->getABITypeAlignment(EltType);
    }

    AMemSet =
      Builder.CreateMemSet(StartPtr, ByteVal, Range.End-Range.Start, Alignment);

    DEBUG(dbgs() << "Replace stores:\n";
          for (unsigned i = 0, e = Range.TheStores.size(); i != e; ++i)
            dbgs() << *Range.TheStores[i] << '\n';
          dbgs() << "With: " << *AMemSet << '\n');

    if (!Range.TheStores.empty())
      AMemSet->setDebugLoc(Range.TheStores[0]->getDebugLoc());

    // Zap all the stores.
    for (SmallVector<Instruction*, 16>::const_iterator
         SI = Range.TheStores.begin(),
         SE = Range.TheStores.end(); SI != SE; ++SI) {
      MD->removeInstruction(*SI);
      (*SI)->eraseFromParent();
    }
    ++NumMemSetInfer;
  }

  return AMemSet;
}


bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
  if (!SI->isSimple()) return false;

  if (TD == 0) return false;

  // Detect cases where we're performing call slot forwarding, but
  // happen to be using a load-store pair to implement it, rather than
  // a memcpy.
  if (LoadInst *LI = dyn_cast<LoadInst>(SI->getOperand(0))) {
    if (LI->isSimple() && LI->hasOneUse() &&
        LI->getParent() == SI->getParent()) {
      MemDepResult ldep = MD->getDependency(LI);
      CallInst *C = 0;
      if (ldep.isClobber() && !isa<MemCpyInst>(ldep.getInst()))
        C = dyn_cast<CallInst>(ldep.getInst());

      if (C) {
        // Check that nothing touches the dest of the "copy" between
        // the call and the store.
        AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
        AliasAnalysis::Location StoreLoc = AA.getLocation(SI);
        for (BasicBlock::iterator I = --BasicBlock::iterator(SI),
                                  E = C; I != E; --I) {
          if (AA.getModRefInfo(&*I, StoreLoc) != AliasAnalysis::NoModRef) {
            C = 0;
            break;
          }
        }
      }

      if (C) {
        unsigned storeAlign = SI->getAlignment();
        if (!storeAlign)
          storeAlign = TD->getABITypeAlignment(SI->getOperand(0)->getType());
        unsigned loadAlign = LI->getAlignment();
        if (!loadAlign)
          loadAlign = TD->getABITypeAlignment(LI->getType());

        bool changed = performCallSlotOptzn(LI,
                        SI->getPointerOperand()->stripPointerCasts(),
                        LI->getPointerOperand()->stripPointerCasts(),
                        TD->getTypeStoreSize(SI->getOperand(0)->getType()),
                        std::min(storeAlign, loadAlign), C);
        if (changed) {
          MD->removeInstruction(SI);
          SI->eraseFromParent();
          MD->removeInstruction(LI);
          LI->eraseFromParent();
          ++NumMemCpyInstr;
          return true;
        }
      }
    }
  }

  // There are two cases that are interesting for this code to handle: memcpy
  // and memset.  Right now we only handle memset.

  // Ensure that the value being stored is something that can be memset'able a
  // byte at a time like "0" or "-1" or any width, as well as things like
  // 0xA0A0A0A0 and 0.0.
  if (Value *ByteVal = isBytewiseValue(SI->getOperand(0)))
    if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
                                              ByteVal)) {
      BBI = I;  // Don't invalidate iterator.
      return true;
    }

  return false;
}

bool MemCpyOpt::processMemSet(MemSetInst *MSI, BasicBlock::iterator &BBI) {
  // See if there is another memset or store neighboring this memset which
  // allows us to widen out the memset to do a single larger store.
  if (isa<ConstantInt>(MSI->getLength()) && !MSI->isVolatile())
    if (Instruction *I = tryMergingIntoMemset(MSI, MSI->getDest(),
                                              MSI->getValue())) {
      BBI = I;  // Don't invalidate iterator.
      return true;
    }
  return false;
}


/// performCallSlotOptzn - takes a memcpy and a call that it depends on,
/// and checks for the possibility of a call slot optimization by having
/// the call write its result directly into the destination of the memcpy.
bool MemCpyOpt::performCallSlotOptzn(Instruction *cpy,
                                     Value *cpyDest, Value *cpySrc,
                                     uint64_t cpyLen, unsigned cpyAlign,
                                     CallInst *C) {
  // The general transformation to keep in mind is
  //
  //   call @func(..., src, ...)
  //   memcpy(dest, src, ...)
  //
  // ->
  //
  //   memcpy(dest, src, ...)
  //   call @func(..., dest, ...)
  //
  // Since moving the memcpy is technically awkward, we additionally check that
  // src only holds uninitialized values at the moment of the call, meaning that
  // the memcpy can be discarded rather than moved.

  // Deliberately get the source and destination with bitcasts stripped away,
  // because we'll need to do type comparisons based on the underlying type.
  CallSite CS(C);

  // Require that src be an alloca.  This simplifies the reasoning considerably.
  AllocaInst *srcAlloca = dyn_cast<AllocaInst>(cpySrc);
  if (!srcAlloca)
    return false;

  // Check that all of src is copied to dest.
  if (TD == 0) return false;

  ConstantInt *srcArraySize = dyn_cast<ConstantInt>(srcAlloca->getArraySize());
  if (!srcArraySize)
    return false;

  uint64_t srcSize = TD->getTypeAllocSize(srcAlloca->getAllocatedType()) *
    srcArraySize->getZExtValue();

  if (cpyLen < srcSize)
    return false;

  // Check that accessing the first srcSize bytes of dest will not cause a
  // trap.  Otherwise the transform is invalid since it might cause a trap
  // to occur earlier than it otherwise would.
  if (AllocaInst *A = dyn_cast<AllocaInst>(cpyDest)) {
    // The destination is an alloca.  Check it is larger than srcSize.
    ConstantInt *destArraySize = dyn_cast<ConstantInt>(A->getArraySize());
    if (!destArraySize)
      return false;

    uint64_t destSize = TD->getTypeAllocSize(A->getAllocatedType()) *
      destArraySize->getZExtValue();

    if (destSize < srcSize)
      return false;
  } else if (Argument *A = dyn_cast<Argument>(cpyDest)) {
    // If the destination is an sret parameter then only accesses that are
    // outside of the returned struct type can trap.
    if (!A->hasStructRetAttr())
      return false;

    Type *StructTy = cast<PointerType>(A->getType())->getElementType();
    uint64_t destSize = TD->getTypeAllocSize(StructTy);

    if (destSize < srcSize)
      return false;
  } else {
    return false;
  }

  // Check that dest points to memory that is at least as aligned as src.
  unsigned srcAlign = srcAlloca->getAlignment();
  if (!srcAlign)
    srcAlign = TD->getABITypeAlignment(srcAlloca->getAllocatedType());
  bool isDestSufficientlyAligned = srcAlign <= cpyAlign;
  // If dest is not aligned enough and we can't increase its alignment then
  // bail out.
  if (!isDestSufficientlyAligned && !isa<AllocaInst>(cpyDest))
    return false;

  // Check that src is not accessed except via the call and the memcpy.  This
  // guarantees that it holds only undefined values when passed in (so the final
  // memcpy can be dropped), that it is not read or written between the call and
  // the memcpy, and that writing beyond the end of it is undefined.
  SmallVector<User*, 8> srcUseList(srcAlloca->use_begin(),
                                   srcAlloca->use_end());
  while (!srcUseList.empty()) {
    User *UI = srcUseList.pop_back_val();

    if (isa<BitCastInst>(UI)) {
      for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
           I != E; ++I)
        srcUseList.push_back(*I);
    } else if (GetElementPtrInst *G = dyn_cast<GetElementPtrInst>(UI)) {
      if (G->hasAllZeroIndices())
        for (User::use_iterator I = UI->use_begin(), E = UI->use_end();
             I != E; ++I)
          srcUseList.push_back(*I);
      else
        return false;
{'fraction_non_alphanumeric': 0.12616794737569878, 'fraction_numerical': 0.007743515793216522, 'mean_word_length': 2.7089896695728624, 'pattern_counts': {'":': 0, '<': 137, '<?xml version=': 0, '>': 369, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 30, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '4769417', 'n_tokens_mistral': 15605, 'n_tokens_neox': 15087, 'n_words': 5164}