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Fix PR3720 by properly propagating alignment information from memcpy/memmove

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onto element accesses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66053 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-03-04 19:20:50 +00:00
parent 66941988de
commit 1541e0f7da
2 changed files with 53 additions and 7 deletions
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41
lib/Transforms/Scalar/ScalarReplAggregates.cpp
View File

@ -287,7 +287,8 @@ bool SROA::performScalarRepl(Function &F) {
const Type *VectorTy = 0;
bool HadAVector = false;
if (CanConvertToScalar(AI, IsNotTrivial, VectorTy, HadAVector,
0, unsigned(AllocaSize)) && IsNotTrivial) {
0, unsigned(AllocaSize)) && IsNotTrivial &&
AllocaSize <= 128) {
AllocaInst *NewAI;
// If we were able to find a vector type that can handle this with
// insert/extract elements, and if there was at least one use that had
@ -721,8 +722,9 @@ void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
SmallVector<AllocaInst*, 32> &NewElts) {
// If this is a memcpy/memmove, construct the other pointer as the
// appropriate type.
// appropriate type. The "Other" pointer is the pointer that goes to
Value *OtherPtr = 0;
unsigned MemAlignment = MI->getAlignment()->getZExtValue();
if (MemCpyInst *MCI = dyn_cast<MemCpyInst>(MI)) {
if (BCInst == MCI->getRawDest())
OtherPtr = MCI->getRawSource();
@ -771,22 +773,47 @@ void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
for (unsigned i = 0, e = NewElts.size(); i != e; ++i) {
// If this is a memcpy/memmove, emit a GEP of the other element address.
Value *OtherElt = 0;
unsigned OtherEltAlign = MemAlignment;
if (OtherPtr) {
Value *Idx[2] = { Zero, ConstantInt::get(Type::Int32Ty, i) };
OtherElt = GetElementPtrInst::Create(OtherPtr, Idx, Idx + 2,
OtherPtr->getNameStr()+"."+utostr(i),
MI);
uint64_t EltOffset;
const PointerType *OtherPtrTy = cast<PointerType>(OtherPtr->getType());
if (const StructType *ST =
dyn_cast<StructType>(OtherPtrTy->getElementType())) {
EltOffset = TD->getStructLayout(ST)->getElementOffset(i);
} else {
const Type *EltTy =
cast<SequentialType>(OtherPtr->getType())->getElementType();
EltOffset = TD->getTypePaddedSize(EltTy)*i;
}
// The alignment of the other pointer is the guaranteed alignment of the
// element, which is affected by both the known alignment of the whole
// mem intrinsic and the alignment of the element. If the alignment of
// the memcpy (f.e.) is 32 but the element is at a 4-byte offset, then the
// known alignment is just 4 bytes.
OtherEltAlign = (unsigned)MinAlign(OtherEltAlign, EltOffset);
}
Value *EltPtr = NewElts[i];
const Type *EltTy =cast<PointerType>(EltPtr->getType())->getElementType();
const Type *EltTy = cast<PointerType>(EltPtr->getType())->getElementType();
// If we got down to a scalar, insert a load or store as appropriate.
if (EltTy->isSingleValueType()) {
if (isa<MemCpyInst>(MI) || isa<MemMoveInst>(MI)) {
Value *Elt = new LoadInst(SROADest ? OtherElt : EltPtr, "tmp",
MI);
new StoreInst(Elt, SROADest ? EltPtr : OtherElt, MI);
if (SROADest) {
// From Other to Alloca.
Value *Elt = new LoadInst(OtherElt, "tmp", false, OtherEltAlign, MI);
new StoreInst(Elt, EltPtr, MI);
} else {
// From Alloca to Other.
Value *Elt = new LoadInst(EltPtr, "tmp", MI);
new StoreInst(Elt, OtherElt, false, OtherEltAlign, MI);
}
continue;
}
assert(isa<MemSetInst>(MI));
@ -852,7 +879,7 @@ void SROA::RewriteMemIntrinUserOfAlloca(MemIntrinsic *MI, Instruction *BCInst,
SROADest ? EltPtr : OtherElt, // Dest ptr
SROADest ? OtherElt : EltPtr, // Src ptr
ConstantInt::get(MI->getOperand(3)->getType(), EltSize), // Size
Zero // Align
ConstantInt::get(Type::Int32Ty, OtherEltAlign) // Align
};
CallInst::Create(TheFn, Ops, Ops + 4, "", MI);
} else {

19
test/Transforms/ScalarRepl/2009-03-04-MemCpyAlign.ll Normal file
View File

@ -0,0 +1,19 @@
; The store into %p should end up with a known alignment of 1, since the memcpy
; is only known to access it with 1-byte alignment.
; RUN: llvm-as < %s | opt -scalarrepl | llvm-dis | grep {store i16 1, .*, align 1}
; PR3720
%struct.st = type { i16 }
define void @f(i8* %p) nounwind {
entry:
%s = alloca %struct.st, align 4 ; <%struct.st*> [#uses=2]
%0 = getelementptr %struct.st* %s, i32 0, i32 0 ; <i16*> [#uses=1]
store i16 1, i16* %0, align 4
%s1 = bitcast %struct.st* %s to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.i32(i8* %p, i8* %s1, i32 2, i32 1)
ret void
}
declare void @llvm.memcpy.i32(i8* nocapture, i8* nocapture, i32, i32) nounwind