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fix PR7589: In brief:

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gep P, (zext x) != gep P, (sext x)

DecomposeGEPExpression was getting this wrong, confusing
basicaa.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111352 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-08-18 04:28:19 +00:00
parent 903175096e
commit 91b2307a89
2 changed files with 24 additions and 3 deletions
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6
lib/Analysis/ValueTracking.cpp
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@ -1018,9 +1018,9 @@ static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
}
}
// Since clients don't care about the high bits of the value, just scales and
// offsets, we can look through extensions.
if (isa<SExtInst>(V) || isa<ZExtInst>(V)) {
// Since GEP indices are sign extended anyway, we don't care about the high
// bits of a sign extended value - just scales and offsets.
if (isa<SExtInst>(V)) {
Value *CastOp = cast<CastInst>(V)->getOperand(0);
unsigned OldWidth = Scale.getBitWidth();
unsigned SmallWidth = CastOp->getType()->getPrimitiveSizeInBits();

21
test/Analysis/BasicAA/featuretest.ll
View File

@ -104,3 +104,24 @@ define i32 @constexpr_test() {
; CHECK: @constexpr_test
; CHECK: ret i32 0
}
; PR7589
; These two index expressions are different, this cannot be CSE'd.
define i16 @zext_sext_confusion(i16* %row2col, i5 %j) nounwind{
entry:
%sum5.cast = zext i5 %j to i64 ; <i64> [#uses=1]
%P1 = getelementptr i16* %row2col, i64 %sum5.cast
%row2col.load.1.2 = load i16* %P1, align 1 ; <i16> [#uses=1]
%sum13.cast31 = sext i5 %j to i6 ; <i6> [#uses=1]
%sum13.cast = zext i6 %sum13.cast31 to i64 ; <i64> [#uses=1]
%P2 = getelementptr i16* %row2col, i64 %sum13.cast
%row2col.load.1.6 = load i16* %P2, align 1 ; <i16> [#uses=1]
%.ret = sub i16 %row2col.load.1.6, %row2col.load.1.2 ; <i16> [#uses=1]
ret i16 %.ret
; CHECK: @zext_sext_confusion
; CHECK: ret i16 %.ret
}