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[MemCpyOpt] Look at any dependency -not just source- for memset+memcpy.

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This fixes another miscompile introduced by r235232: when there was a
dependency on the memcpy destination other than the memset, we would
ignore it, because we only looked at the source dependency.

It was a mistake to use SrcDepInfo.  Instead, just use DepInfo.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237066 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha
2015-05-11 23:09:46 +00:00
parent 12a7fbc55c
commit 6eb095d7ae
2 changed files with 25 additions and 6 deletions
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13
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@@ -927,14 +927,12 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
return true; return true;
} }
AliasAnalysis::Location SrcLoc = AliasAnalysis::getLocationForSource(M); MemDepResult DepInfo = MD->getDependency(M);
MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(SrcLoc, true,
M, M->getParent());
// Try to turn a partially redundant memset + memcpy into // Try to turn a partially redundant memset + memcpy into
// memcpy + smaller memset. We don't need the memcpy size for this. // memcpy + smaller memset. We don't need the memcpy size for this.
if (SrcDepInfo.isClobber()) if (DepInfo.isClobber())
if (MemSetInst *MDep = dyn_cast<MemSetInst>(SrcDepInfo.getInst())) if (MemSetInst *MDep = dyn_cast<MemSetInst>(DepInfo.getInst()))
if (processMemSetMemCpyDependence(M, MDep)) if (processMemSetMemCpyDependence(M, MDep))
return true; return true;
@@ -948,7 +946,6 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
// c) memcpy from freshly alloca'd space or space that has just started its // c) memcpy from freshly alloca'd space or space that has just started its
// lifetime copies undefined data, and we can therefore eliminate the // lifetime copies undefined data, and we can therefore eliminate the
// memcpy in favor of the data that was already at the destination. // memcpy in favor of the data that was already at the destination.
MemDepResult DepInfo = MD->getDependency(M);
if (DepInfo.isClobber()) { if (DepInfo.isClobber()) {
if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) { if (CallInst *C = dyn_cast<CallInst>(DepInfo.getInst())) {
if (performCallSlotOptzn(M, M->getDest(), M->getSource(), if (performCallSlotOptzn(M, M->getDest(), M->getSource(),
@@ -961,6 +958,10 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
} }
} }
AliasAnalysis::Location SrcLoc = AliasAnalysis::getLocationForSource(M);
MemDepResult SrcDepInfo = MD->getPointerDependencyFrom(SrcLoc, true,
M, M->getParent());
if (SrcDepInfo.isClobber()) { if (SrcDepInfo.isClobber()) {
if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst())) if (MemCpyInst *MDep = dyn_cast<MemCpyInst>(SrcDepInfo.getInst()))
return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue()); return processMemCpyMemCpyDependence(M, MDep, CopySize->getZExtValue());

18
test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
View File

@@ -126,6 +126,24 @@ define void @test_different_dst(i8* %dst2, i8* %src, i64 %src_size, i8* %dst, i6
ret void ret void
} }
; Make sure we also take into account dependencies on the destination.
; CHECK-LABEL: define i8 @test_intermediate_read
; CHECK-NEXT: %ca = alloca [64 x i8], align 8
; CHECK-NEXT: %c = getelementptr [64 x i8], [64 x i8]* %ca, i64 0, i64 0
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %a, i8 0, i64 64, i32 1, i1 false)
; CHECK-NEXT: %r = load i8, i8* %a
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %a, i8* %b, i64 24, i32 1, i1 false)
; CHECK-NEXT: ret i8 %r
define i8 @test_intermediate_read(i8* %a, i8* %b) #0 {
%ca = alloca [64 x i8], align 8
%c = getelementptr [64 x i8], [64 x i8]* %ca, i64 0, i64 0
call void @llvm.memset.p0i8.i64(i8* %a, i8 0, i64 64, i32 1, i1 false)
%r = load i8, i8* %a
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %a, i8* %b, i64 24, i32 1, i1 false)
ret i8 %r
}
declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1)
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1) declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1)
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1)