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[MemCpyOpt] Don't hoist store that's not guaranteed to execute 

MemCpyOpt can hoist stores while load+store pairs into memcpy.
This hoisting can currently result in stores being executed that
weren't guaranteed to execute in the original problem.

Differential Revision: https://reviews.llvm.org/D89154
This commit is contained in:
Nikita Popov 2020-10-09 21:09:16 +02:00
parent 2b96dcebfa
commit 5e855f1e80
2 changed files with 9 additions and 5 deletions
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5
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -491,6 +491,11 @@ bool MemCpyOptPass::moveUp(StoreInst *SI, Instruction *P, const LoadInst *LI) {
for (auto I = --SI->getIterator(), E = P->getIterator(); I != E; --I) {
auto *C = &*I;
// Make sure hoisting does not perform a store that was not guaranteed to
// happen.
if (!isGuaranteedToTransferExecutionToSuccessor(C))
return false;
bool MayAlias = isModOrRefSet(AA->getModRefInfo(C, None));
bool NeedLift = false;

9
llvm/test/Transforms/MemCpyOpt/fca2memcpy.ll
View File

@ -147,12 +147,11 @@ define void @noaliasaddrproducer(%S* %src, %S* noalias %dst, i32* noalias %dstid
define void @throwing_call(%S* noalias %src, %S* %dst) {
; CHECK-LABEL: @throwing_call(
; CHECK-NEXT: [[TMP1:%.*]] = bitcast %S* [[SRC:%.*]] to i8*
; CHECK-NEXT: [[TMP2:%.*]] = bitcast %S* [[DST:%.*]] to i8*
; CHECK-NEXT: [[TMP3:%.*]] = bitcast %S* [[SRC]] to i8*
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 8 [[TMP2]], i8* align 8 [[TMP3]], i64 16, i1 false)
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 8 [[TMP1]], i8 0, i64 16, i1 false)
; CHECK-NEXT: [[TMP1:%.*]] = load [[S:%.*]], %S* [[SRC:%.*]], align 8
; CHECK-NEXT: [[TMP2:%.*]] = bitcast %S* [[SRC]] to i8*
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 8 [[TMP2]], i8 0, i64 16, i1 false)
; CHECK-NEXT: call void @call() [[ATTR2:#.*]]
; CHECK-NEXT: store [[S]] [[TMP1]], %S* [[DST:%.*]], align 8
; CHECK-NEXT: ret void
;
%1 = load %S, %S* %src