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MemCpyOpt cannot use ABI alignment even if it was not given 

Summary: This patch fixes https://bugs.llvm.org/show_bug.cgi?id=44388 which incorrectly assigns an ABI alignment to memset when there was no explicit alignment given.

Reviewers: gchatelet, lenary, nikic

Reviewed By: nikic

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74083
This commit is contained in:
Juneyoung Lee 2020-02-06 06:20:36 +09:00
parent 2697e8bc1e
commit ad9ae6ee2b
2 changed files with 36 additions and 27 deletions
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46
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -144,6 +144,24 @@ bool MemsetRange::isProfitableToUseMemset(const DataLayout &DL) const {
return TheStores.size() > NumPointerStores+NumByteStores;
}
static Align findStoreAlignment(const DataLayout &DL, const StoreInst *SI) {
return DL.getValueOrABITypeAlignment(MaybeAlign(SI->getAlignment()),
SI->getOperand(0)->getType());
}
static Align findLoadAlignment(const DataLayout &DL, const LoadInst *LI) {
return DL.getValueOrABITypeAlignment(MaybeAlign(LI->getAlignment()),
LI->getType());
}
static Align findCommonAlignment(const DataLayout &DL, const StoreInst *SI,
const LoadInst *LI) {
Align StoreAlign = findStoreAlignment(DL, SI);
Align LoadAlign = findLoadAlignment(DL, LI);
return commonAlignment(StoreAlign, LoadAlign);
}
namespace {
class MemsetRanges {
@ -173,8 +191,8 @@ public:
void addStore(int64_t OffsetFromFirst, StoreInst *SI) {
int64_t StoreSize = DL.getTypeStoreSize(SI->getOperand(0)->getType());
addRange(OffsetFromFirst, StoreSize,
SI->getPointerOperand(), SI->getAlignment(), SI);
addRange(OffsetFromFirst, StoreSize, SI->getPointerOperand(),
findStoreAlignment(DL, SI).value(), SI);
}
void addMemSet(int64_t OffsetFromFirst, MemSetInst *MSI) {
@ -387,13 +405,8 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
// Get the starting pointer of the block.
StartPtr = Range.StartPtr;
// Determine alignment
const Align Alignment = DL.getValueOrABITypeAlignment(
MaybeAlign(Range.Alignment),
cast<PointerType>(StartPtr->getType())->getElementType());
AMemSet = Builder.CreateMemSet(StartPtr, ByteVal, Range.End - Range.Start,
Alignment);
MaybeAlign(Range.Alignment));
LLVM_DEBUG(dbgs() << "Replace stores:\n"; for (Instruction *SI
: Range.TheStores) dbgs()
<< *SI << '\n';
@ -413,23 +426,6 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
return AMemSet;
}
static Align findStoreAlignment(const DataLayout &DL, const StoreInst *SI) {
return DL.getValueOrABITypeAlignment(MaybeAlign(SI->getAlignment()),
SI->getOperand(0)->getType());
}
static Align findLoadAlignment(const DataLayout &DL, const LoadInst *LI) {
return DL.getValueOrABITypeAlignment(MaybeAlign(LI->getAlignment()),
LI->getType());
}
static Align findCommonAlignment(const DataLayout &DL, const StoreInst *SI,
const LoadInst *LI) {
Align StoreAlign = findStoreAlignment(DL, SI);
Align LoadAlign = findLoadAlignment(DL, LI);
return commonAlignment(StoreAlign, LoadAlign);
}
// This method try to lift a store instruction before position P.
// It will lift the store and its argument + that anything that
// may alias with these.

17
llvm/test/Transforms/MemCpyOpt/form-memset.ll
View File

@ -217,7 +217,7 @@ entry:
tail call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 12, i1 false)
ret void
; CHECK-LABEL: @test6(
; CHECK: call void @llvm.memset.p0i8.i64(i8* align 4 %2, i8 0, i64 24, i1 false)
; CHECK: call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 24, i1 false)
}
; More aggressive heuristic
@ -280,7 +280,7 @@ define void @test10(i8* nocapture %P) nounwind {
ret void
; CHECK-LABEL: @test10(
; CHECK-NOT: memset
; CHECK: call void @llvm.memset.p0i8.i64(i8* align 1 %P, i8 0, i64 42, i1 false)
; CHECK: call void @llvm.memset.p0i8.i64(i8* %P, i8 0, i64 42, i1 false)
; CHECK-NOT: memset
; CHECK: ret void
}
@ -299,3 +299,16 @@ entry:
; CHECK-NOT: store
; CHECK: call void @llvm.memset.p0i8.i64(i8* align 4 %1, i8 1, i64 23, i1 false)
}
; Alignment should be preserved when there is a store with default align
define void @test12(i32* nocapture %P) nounwind ssp {
entry:
store i32 0, i32* %P
%add.ptr = getelementptr inbounds i32, i32* %P, i64 1
%0 = bitcast i32* %add.ptr to i8*
tail call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 11, i1 false)
ret void
; CHECK-LABEL: @test12(
; CHECK-NOT: store
; CHECK: call void @llvm.memset.p0i8.i64(i8* align 4 %1, i8 0, i64 15, i1 false)
}