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Failure to optimize based on umax implication #63896

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nikic opened this issue Jul 16, 2023 · 1 comment
Closed

Failure to optimize based on umax implication #63896

nikic opened this issue Jul 16, 2023 · 1 comment
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@dtcxzyw
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llvm:optimizations missed-optimization

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@nikic
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nikic commented Jul 16, 2023

https://alive2.llvm.org/ce/z/o_8ch3

define i1 @src(i8 %x, i8 %y) {
  %max = call i8 @llvm.umax.i8(i8 %x, i8 1)
  %cmp = icmp ugt i8 %y, %max
  br i1 %cmp, label %if, label %end

if:
  %cmp2 = icmp ugt i8 %y, %x
  ret i1 %cmp2

end:
  ret i1 false
}

define i1 @tgt(i8 %x, i8 %y) {
  %max = call i8 @llvm.umax.i8(i8 %x, i8 1)
  %cmp = icmp ugt i8 %y, %max
  br i1 %cmp, label %if, label %end

if:
  ret i1 true

end:
  ret i1 false
}

declare i8 @llvm.umax.i8(i8, i8)

This might be either for ConstraintElimination or InstCombine.

For the case where icmp ugt i8 %y, 1 is used, CVP/LVI could also handle this.
@nikic nikic mentioned this issue Jul 16, 2023
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@dtcxzyw dtcxzyw self-assigned this Jul 16, 2023
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dtcxzyw commented Jul 16, 2023

Candidate patch https://reviews.llvm.org/D155412

dtcxzyw added a commit that referenced this issue Jul 24, 2023
@dtcxzyw
[ConstraintElim] Add test cases from PR63896. NFC.
de0d27c 
This patch adds some test cases from #63896.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D155853
veselypeta pushed a commit to veselypeta/cherillvm that referenced this issue Sep 7, 2024
@dtcxzyw @veselypeta
[ConstraintElim] Add test cases from PR63896. NFC.
cf0aff4 
This patch adds some test cases from llvm/llvm-project#63896.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D155853
veselypeta pushed a commit to veselypeta/cherillvm that referenced this issue Sep 7, 2024
@dtcxzyw @veselypeta
[ConstraintElim] Add facts implied by MinMaxIntrinsic
60134db 
Fixes llvm/llvm-project#63896 and rust-lang/rust#113757.
This patch adds facts implied by llvm.smin/smax/umin/umax intrinsics.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D155412
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