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PR9561: A store with a negative offset (via GEP) could erroniously say that it

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completely overlaps a previous store, thus mistakenly deleting that store. Check
for this condition.

llvm-svn: 128319
This commit is contained in:
Bill Wendling 2011-03-26 01:20:37 +00:00
parent b05e6939a0
commit 72b390743d
2 changed files with 24 additions and 0 deletions
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2
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -354,8 +354,10 @@ static bool isCompleteOverwrite(const AliasAnalysis::Location &Later,
// In this case, we see if the later store completely overlaps all bytes // In this case, we see if the later store completely overlaps all bytes
// stored by the previous store. // stored by the previous store.
if (Off1 < Off2 || // Earlier starts before Later. if (Off1 < Off2 || // Earlier starts before Later.
Off2 < 0 || // Later is -.
Off1+Earlier.Size > Off2+Later.Size) // Earlier goes beyond Later. Off1+Earlier.Size > Off2+Later.Size) // Earlier goes beyond Later.
return false; return false;
// Otherwise, we have complete overlap. // Otherwise, we have complete overlap.
return true; return true;
} }

22
test/Transforms/DeadStoreElimination/2011-03-25-DSEMiscompile.ll Normal file
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@ -0,0 +1,22 @@
; RUN: opt < %s -basicaa -dse -S | FileCheck %s
; PR9561
target triple = "i386-apple-darwin9.8"
@A = external global [0 x i32]
declare cc10 void @Func2(i32*, i32*, i32*, i32)
define cc10 void @Func1(i32* noalias %Arg1, i32* noalias %Arg2, i32* %Arg3, i32 %Arg4) {
entry:
store i32 add (i32 ptrtoint ([0 x i32]* @A to i32), i32 1), i32* %Arg2
; CHECK: store i32 add (i32 ptrtoint ([0 x i32]* @A to i32), i32 1), i32* %Arg2
%ln2gz = getelementptr i32* %Arg1, i32 14
%ln2gA = bitcast i32* %ln2gz to double*
%ln2gB = load double* %ln2gA
%ln2gD = getelementptr i32* %Arg2, i32 -3
%ln2gE = bitcast i32* %ln2gD to double*
store double %ln2gB, double* %ln2gE
; CHECK: store double %ln2gB, double* %ln2gE
tail call cc10 void @Func2(i32* %Arg1, i32* %Arg2, i32* %Arg3, i32 %Arg4) nounwind
ret void
}