Author: lattner
Date: Sun Jan 13 16:30:28 2008
New Revision: 45943
URL: http://llvm.org/viewvc/llvm-project?rev=45943&view=rev
Log:
simplify some code. If we can infer alignment for source and dest that are
greater than memcpy alignment, and if we lower to load/store, use the best
alignment info we have.
Modified:
llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=45943&r1=45942&r2=45943&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Sun Jan 13
16:30:28 2008
@@ -7854,34 +7854,35 @@
// 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);
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