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[MemCpy] Check for alias in performMemCpyToMemSetOptzn, instead of the identity of two operands

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Summary:
This fixes pr29105. The reason is that lifetime marks creates new
aliasing pointers the original ones, but before this patch aliases
were not checked in performMemCpyToMemSetOptzn.

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23846

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279769 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Tim Shen 2016-08-25 19:27:26 +00:00
parent 543a8c13a2
commit f65deb821d
2 changed files with 41 additions and 1 deletions
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4
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -1108,8 +1108,10 @@ bool MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
/// The \p MemCpy must have a Constant length.
bool MemCpyOptPass::performMemCpyToMemSetOptzn(MemCpyInst *MemCpy,
MemSetInst *MemSet) {
AliasAnalysis &AA = LookupAliasAnalysis();
// This only makes sense on memcpy(..., memset(...), ...).
if (MemSet->getRawDest() != MemCpy->getRawSource())
if (!AA.isMustAlias(MemSet->getRawDest(), MemCpy->getRawSource()))
return false;
ConstantInt *CopySize = cast<ConstantInt>(MemCpy->getLength());

38
test/Transforms/MemCpyOpt/pr29105.ll Normal file
View File

@ -0,0 +1,38 @@
; RUN: opt -memcpyopt -instcombine -S %s | FileCheck %s
%Foo = type { [2048 x i64] }
; CHECK-LABEL: @baz(
; CHECK-NOT: call void @llvm.memcpy
define void @baz() unnamed_addr #0 {
entry-block:
%x.sroa.0 = alloca [2048 x i64], align 8
%tmp0 = alloca [2048 x i64], align 8
%0 = bitcast [2048 x i64]* %tmp0 to i8*
%tmp2 = alloca %Foo, align 8
%x.sroa.0.0..sroa_cast6 = bitcast [2048 x i64]* %x.sroa.0 to i8*
call void @llvm.lifetime.start(i64 16384, i8* %x.sroa.0.0..sroa_cast6)
call void @llvm.lifetime.start(i64 16384, i8* %0)
call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 16384, i32 8, i1 false)
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %x.sroa.0.0..sroa_cast6, i8* %0, i64 16384, i32 8, i1 false)
call void @llvm.lifetime.end(i64 16384, i8* %0)
%1 = bitcast %Foo* %tmp2 to i8*
call void @llvm.lifetime.start(i64 16384, i8* %1)
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %1, i8* %x.sroa.0.0..sroa_cast6, i64 16384, i32 8, i1 false)
call void @bar(%Foo* noalias nocapture nonnull dereferenceable(16384) %tmp2)
call void @llvm.lifetime.end(i64 16384, i8* %1)
call void @llvm.lifetime.end(i64 16384, i8* %x.sroa.0.0..sroa_cast6)
ret void
}
declare void @llvm.lifetime.start(i64, i8* nocapture) #1
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1) #1
declare void @llvm.lifetime.end(i64, i8* nocapture) #1
declare void @bar(%Foo* noalias nocapture readonly dereferenceable(16384)) unnamed_addr #0
declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i32, i1) #1
attributes #0 = { uwtable }
attributes #1 = { argmemonly nounwind }