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[InstCombine] fix undef propagation for vector urem transform (PR44186) 

As described here:
https://bugs.llvm.org/show_bug.cgi?id=44186

The match() code safely allows undef values, but we can't safely
propagate a vector constant that contains an undef to the new
compare instruction.
This commit is contained in:
Sanjay Patel 2019-12-02 12:10:05 -05:00
parent d8d5106225
commit af4e59949c
2 changed files with 5 additions and 3 deletions
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6
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -1368,8 +1368,10 @@ Instruction *InstCombiner::visitURem(BinaryOperator &I) {
}
// 1 urem X -> zext(X != 1)
if (match(Op0, m_One()))
return CastInst::CreateZExtOrBitCast(Builder.CreateICmpNE(Op1, Op0), Ty);
if (match(Op0, m_One())) {
Value *Cmp = Builder.CreateICmpNE(Op1, ConstantInt::get(Ty, 1));
return CastInst::CreateZExtOrBitCast(Cmp, Ty);
}
// X urem C -> X < C ? X : X - C, where C >= signbit.
if (match(Op1, m_Negative())) {

2
llvm/test/Transforms/InstCombine/vector-urem.ll
View File

@ -39,7 +39,7 @@ define <4 x i32> @test_v4i32_one(<4 x i32> %a0) {
define <4 x i32> @test_v4i32_one_undef(<4 x i32> %a0) {
; CHECK-LABEL: @test_v4i32_one_undef(
; CHECK-NEXT: [[TMP1:%.*]] = icmp ne <4 x i32> [[A0:%.*]], <i32 1, i32 1, i32 1, i32 undef>
; CHECK-NEXT: [[TMP1:%.*]] = icmp ne <4 x i32> [[A0:%.*]], <i32 1, i32 1, i32 1, i32 1>
; CHECK-NEXT: [[TMP2:%.*]] = zext <4 x i1> [[TMP1]] to <4 x i32>
; CHECK-NEXT: ret <4 x i32> [[TMP2]]
;