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Memory dependence analysis was incorrectly stopping to scan for stores to a pointer at bitcast uses of a malloc call.

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It should continue scanning until the malloc call, and this patch fixes that.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83931 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Victor Hernandez 2009-10-13 01:42:53 +00:00
parent 2b7b37a4c9
commit 5c78736f85
2 changed files with 20 additions and 10 deletions
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15
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -225,16 +225,11 @@ getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
// the allocation, return Def. This means that there is no dependence and
// the access can be optimized based on that. For example, a load could
// turn into undef.
if (AllocationInst *AI = dyn_cast<AllocationInst>(Inst)) {
Value *AccessPtr = MemPtr->getUnderlyingObject();
if (AccessPtr == AI ||
AA->alias(AI, 1, AccessPtr, 1) == AliasAnalysis::MustAlias)
return MemDepResult::getDef(AI);
continue;
}
if (isMalloc(Inst)) {
// Note: Only determine this to be a malloc if Inst is the malloc call, not
// 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<AllocationInst>(Inst) || extractMallocCall(Inst)) {
Value *AccessPtr = MemPtr->getUnderlyingObject();
if (AccessPtr == Inst ||

15
test/Transforms/GVN/2009-11-12-MemDepMallocBitCast.ll Normal file
View File

@ -0,0 +1,15 @@
; Test to make sure malloc's bitcast does not block detection of a store
; to aliased memory; GVN should not optimize away the load in this program.
; RUN: opt < %s -gvn -S | FileCheck %s
define i64 @test() {
%1 = tail call i8* @malloc(i64 mul (i64 4, i64 ptrtoint (i64* getelementptr (i64* null, i64 1) to i64))) ; <i8*> [#uses=2]
store i8 42, i8* %1
%X = bitcast i8* %1 to i64* ; <i64*> [#uses=1]
%Y = load i64* %X ; <i64> [#uses=1]
ret i64 %Y
; CHECK: %Y = load i64* %X
; CHECK: ret i64 %Y
}
declare noalias i8* @malloc(i64)