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Fix more fallout from r158919, similar to PR13547. 

This code used to only handle malloc-like calls, which do not read memory.
r158919 changed it to check isNoAliasFn(), which includes strdup-like and
realloc-like calls, but it was not checking for dependencies on the memory
read by those calls.

llvm-svn: 163106
This commit is contained in:
Bob Wilson 2012-09-03 05:15:15 +00:00
parent fd648a0320
commit dcc54decd5
2 changed files with 21 additions and 2 deletions
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7
llvm/lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -479,11 +479,16 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
// a subsequent bitcast of the malloc call result. There can be stores to
// the malloced memory between the malloc call and its bitcast uses, and we
// need to continue scanning until the malloc call.
if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, AA->getTargetLibraryInfo())){
const TargetLibraryInfo *TLI = AA->getTargetLibraryInfo();
if (isa<AllocaInst>(Inst) || isNoAliasFn(Inst, TLI)) {
const Value *AccessPtr = GetUnderlyingObject(MemLoc.Ptr, TD);
if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr))
return MemDepResult::getDef(Inst);
// If the allocation is not aliased and does not read memory (like
// strdup), it is safe to ignore.
if (isa<AllocaInst>(Inst) ||
isMallocLikeFn(Inst, TLI) || isCallocLikeFn(Inst, TLI))
continue;
}

14
llvm/test/Transforms/DeadStoreElimination/simple.ll
View File

@ -310,3 +310,17 @@ define void @test24([2 x i32]* %a, i32 %b, i32 %c) nounwind {
store i32 %c, i32* %4, align 4
ret void
}
; Check another case like PR13547 where strdup is not like malloc.
; CHECK: @test25
; CHECK: load i8
; CHECK: store i8 0
; CHECK: store i8 %tmp
define i8* @test25(i8* %p) nounwind {
%p.4 = getelementptr i8* %p, i64 4
%tmp = load i8* %p.4, align 1
store i8 0, i8* %p.4, align 1
%q = call i8* @strdup(i8* %p) nounwind optsize
store i8 %tmp, i8* %p.4, align 1
ret i8* %q
}