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Don't fold (select C, (gep Ptr, Idx), Ptr) if C is vector but Idx is scalar 

The folding rule (select C, (gep Ptr, Idx), Ptr) -> (gep Ptr, (select C,
Idx, 0)) creates a malformed SELECT IR if C is a vector while Idx is scalar.

  SELECT VecC, ScalarIdx, 0

We could splat Idx to a vector but it defeats the purpose of
optimisation. Don't apply the folding rule in this case.

This fixes a regression from commit d561b6fbdb.
This commit is contained in:
Yi Kong 2021-09-22 15:50:12 +08:00
parent 36daf074d9
commit d0746f2e9b
2 changed files with 16 additions and 1 deletions
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4
llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
View File

@ -3004,8 +3004,10 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
if (Gep->getNumOperands() != 2 || Gep->getPointerOperand() != Base ||
!Gep->hasOneUse())
return nullptr;
Type *ElementType = Gep->getResultElementType();
Value *Idx = Gep->getOperand(1);
if (isa<VectorType>(CondVal->getType()) && !isa<VectorType>(Idx->getType()))
return nullptr;
Type *ElementType = Gep->getResultElementType();
Value *NewT = Idx;
Value *NewF = Constant::getNullValue(Idx->getType());
if (Swap)

13
llvm/test/Transforms/InstCombine/select-gep.ll
View File

@ -244,3 +244,16 @@ define i32* @test6(i32* %p, i64 %x, i64 %y) {
ret i32* %sel
}
declare void @use_i32p(i32*)
; We cannot create a select-with-idx with a vector condition but scalar idx.
define <2 x i64*> @test7(<2 x i64*> %p1, i64 %idx, <2 x i1> %cc) {
; CHECK-LABEL: @test7(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i64, <2 x i64*> [[P1:%.*]], i64 [[IDX]]
; CHECK-NEXT: [[SELECT:%.*]] = select <2 x i1> [[CC:%.*]], <2 x i64*> [[P1:%.*]], <2 x i64*> [[GEP]]
; CHECK-NEXT: ret <2 x i64*> [[SELECT]]
;
%gep = getelementptr i64, <2 x i64*> %p1, i64 %idx
%select = select <2 x i1> %cc, <2 x i64*> %p1, <2 x i64*> %gep
ret <2 x i64*> %select
}