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[MemCpyOpt] Don't sink LoadInst below possible clobber. 

Differential Revision: https://reviews.llvm.org/D26811

llvm-svn: 290611
This commit is contained in:
Bryant Wong 2016-12-27 17:58:12 +00:00
parent e0ee5cf7c8
commit 7cb744621b
2 changed files with 47 additions and 5 deletions
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16
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -489,7 +489,8 @@ static unsigned findCommonAlignment(const DataLayout &DL, const StoreInst *SI,
// It will lift the store and its argument + that anything that
// may alias with these.
// The method returns true if it was successful.
static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P) {
static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P,
const LoadInst *LI) {
// If the store alias this position, early bail out.
MemoryLocation StoreLoc = MemoryLocation::get(SI);
if (AA.getModRefInfo(P, StoreLoc) != MRI_NoModRef)
@ -506,12 +507,13 @@ static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P) {
SmallVector<Instruction*, 8> ToLift;
// Memory locations of lifted instructions.
SmallVector<MemoryLocation, 8> MemLocs;
MemLocs.push_back(StoreLoc);
SmallVector<MemoryLocation, 8> MemLocs{StoreLoc};
// Lifted callsites.
SmallVector<ImmutableCallSite, 8> CallSites;
const MemoryLocation LoadLoc = MemoryLocation::get(LI);
for (auto I = --SI->getIterator(), E = P->getIterator(); I != E; --I) {
auto *C = &*I;
@ -535,7 +537,11 @@ static bool moveUp(AliasAnalysis &AA, StoreInst *SI, Instruction *P) {
continue;
if (MayAlias) {
if (auto CS = ImmutableCallSite(C)) {
// Since LI is implicitly moved downwards past the lifted instructions,
// none of them may modify its source.
if (AA.getModRefInfo(C, LoadLoc) & MRI_Mod)
return false;
else if (auto CS = ImmutableCallSite(C)) {
// If we can't lift this before P, it's game over.
if (AA.getModRefInfo(P, CS) != MRI_NoModRef)
return false;
@ -610,7 +616,7 @@ bool MemCpyOptPass::processStore(StoreInst *SI, BasicBlock::iterator &BBI) {
// position if nothing alias the store memory after this and the store
// destination is not in the range.
if (P && P != SI) {
if (!moveUp(AA, SI, P))
if (!moveUp(AA, SI, P, LI))
P = nullptr;
}

36
llvm/test/Transforms/MemCpyOpt/load-store-to-memcpy.ll Normal file
View File

@ -0,0 +1,36 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -basicaa -scoped-noalias -memcpyopt -S %s | FileCheck %s
%T = type { i8, i32 }
; memcpy(%d, %a) should not be generated since store2 may-aliases load %a.
define void @f(%T* %a, %T* %b, %T* %c, %T* %d) {
; CHECK-LABEL: @f(
; CHECK-NEXT: [[VAL:%.*]] = load %T, %T* %a, !alias.scope !0
; CHECK-NEXT: store %T { i8 23, i32 23 }, %T* %b, !alias.scope !3
; CHECK-NEXT: store %T { i8 44, i32 44 }, %T* %c, !alias.scope !6, !noalias !3
; CHECK-NEXT: store %T [[VAL]], %T* %d, !alias.scope !9, !noalias !12
; CHECK-NEXT: ret void
;
%val = load %T, %T* %a, !alias.scope !{!10}
; store1 may-aliases the load
store %T { i8 23, i32 23 }, %T* %b, !alias.scope !{!11}
; store2 may-aliases the load and store3
store %T { i8 44, i32 44 }, %T* %c, !alias.scope !{!12}, !noalias !{!11}
; store3
store %T %val, %T* %d, !alias.scope !{!13}, !noalias !{!10, !11}
ret void
}
!0 = !{!0}
!1 = !{!1}
!2 = !{!2}
!3 = !{!3}
!10 = !{ !10, !0 }
!11 = !{ !11, !1 }
!12 = !{ !12, !2 }
!13 = !{ !13, !3 }