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simplify some code. If we can infer alignment for source and dest that are

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greater than memcpy alignment, and if we lower to load/store, use the best 
alignment info we have.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45943 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-01-13 22:30:28 +00:00
parent 6d0339d451
commit 88b39744ec
1 changed files with 22 additions and 21 deletions
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43
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -7854,34 +7854,35 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
// If we can determine a pointer alignment that is bigger than currently
// set, update the alignment.
if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
unsigned Alignment1 = GetOrEnforceKnownAlignment(MI->getOperand(1), TD);
unsigned Alignment2 = GetOrEnforceKnownAlignment(MI->getOperand(2), TD);
unsigned Align = std::min(Alignment1, Alignment2);
if (MI->getAlignment()->getZExtValue() < Align) {
MI->setAlignment(ConstantInt::get(Type::Int32Ty, Align));
unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getOperand(1), TD);
unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getOperand(2), TD);
unsigned MinAlign = std::min(DstAlign, SrcAlign);
unsigned CopyAlign = MI->getAlignment()->getZExtValue();
if (CopyAlign < MinAlign) {
MI->setAlignment(ConstantInt::get(Type::Int32Ty, MinAlign));
Changed = true;
}
// If MemCpyInst length is 1/2/4/8 bytes then replace memcpy with
// load/store.
ConstantInt *MemOpLength = dyn_cast<ConstantInt>(CI.getOperand(3));
if (MemOpLength) {
if (ConstantInt *MemOpLength = dyn_cast<ConstantInt>(CI.getOperand(3))) {
// Source and destination pointer types are always "i8*" for intrinsic.
// If Size is 8 then use Int64Ty
// If Size is 4 then use Int32Ty
// If Size is 2 then use Int16Ty
// If Size is 1 then use Int8Ty
unsigned Size = MemOpLength->getZExtValue();
unsigned Align = cast<ConstantInt>(CI.getOperand(4))->getZExtValue();
PointerType *NewPtrTy = NULL;
// Destination pointer type is always i8 *
// If Size is 8 then use Int64Ty
// If Size is 4 then use Int32Ty
// If Size is 2 then use Int16Ty
// If Size is 1 then use Int8Ty
if (Size && Size <=8 && !(Size&(Size-1)))
NewPtrTy = PointerType::getUnqual(IntegerType::get(Size<<3));
if (NewPtrTy) {
if (Size && Size <= 8 && !(Size&(Size-1))) {
Type *NewPtrTy = PointerType::getUnqual(IntegerType::get(Size<<3));
// If the memcpy/memmove provides better alignment info than we can
// infer, use it.
SrcAlign = std::max(SrcAlign, CopyAlign);
DstAlign = std::max(DstAlign, CopyAlign);
Value *Src = InsertBitCastBefore(CI.getOperand(2), NewPtrTy, CI);
Value *Dest = InsertBitCastBefore(CI.getOperand(1), NewPtrTy, CI);
Value *L = new LoadInst(Src, "tmp", false, Align, &CI);
Value *NS = new StoreInst(L, Dest, false, Align, &CI);
Value *L = new LoadInst(Src, "tmp", false, SrcAlign, &CI);
Value *NS = new StoreInst(L, Dest, false, DstAlign, &CI);
CI.replaceAllUsesWith(NS);
Changed = true;
return EraseInstFromFunction(CI);