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[InstSimplify] Clarify use of FixedVectorType in SimplifySelectInst

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Folding a select of vector constants that include undef elements only
applies to fixed vectors, but there's no earlier check the type is not
scalable so it crashes for scalable vectors. This adds a check so this
optimization is only attempted for fixed vectors.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D92046
This commit is contained in:
Cullen Rhodes 2020-11-24 18:07:13 +00:00
parent 4a8996e74d
commit 50fbdf20c1
2 changed files with 13 additions and 1 deletions
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3
lib/Analysis/InstructionSimplify.cpp
View File

@ -4136,7 +4136,8 @@ static Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
// Deal with partial undef vector constants: select ?, VecC, VecC' --> VecC''
Constant *TrueC, *FalseC;
if (TrueVal->getType()->isVectorTy() && match(TrueVal, m_Constant(TrueC)) &&
if (isa<FixedVectorType>(TrueVal->getType()) &&
match(TrueVal, m_Constant(TrueC)) &&
match(FalseVal, m_Constant(FalseC))) {
unsigned NumElts =
cast<FixedVectorType>(TrueC->getType())->getNumElements();

11
test/Transforms/InstSimplify/select.ll
View File

@ -957,3 +957,14 @@ define i32 @pr47322_more_poisonous_replacement(i32 %arg) {
ret i32 %r1.sroa.0.1
}
declare i32 @llvm.cttz.i32(i32, i1 immarg)
; Partial undef scalable vectors should be ignored.
define <vscale x 2 x i1> @ignore_scalable_undef(<vscale x 2 x i1> %cond) {
; CHECK-LABEL: @ignore_scalable_undef(
; CHECK-NEXT: [[S:%.*]] = select <vscale x 2 x i1> [[COND:%.*]], <vscale x 2 x i1> undef, <vscale x 2 x i1> insertelement (<vscale x 2 x i1> undef, i1 true, i32 0)
; CHECK-NEXT: ret <vscale x 2 x i1> [[S]]
;
%vec = insertelement <vscale x 2 x i1> undef, i1 true, i32 0
%s = select <vscale x 2 x i1> %cond, <vscale x 2 x i1> undef, <vscale x 2 x i1> %vec
ret <vscale x 2 x i1> %s
}