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[InstSimplify] simplifyPHINode phi fold incorrect according to alive2 #115250

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akshayrdeodhar opened this issue Nov 7, 2024 · 2 comments
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[InstSimplify] simplifyPHINode phi fold incorrect according to alive2 #115250

akshayrdeodhar opened this issue Nov 7, 2024 · 2 comments
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duplicate Resolved as duplicate llvm:instcombine miscompilation

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@akshayrdeodhar
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akshayrdeodhar commented Nov 7, 2024 •
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When a phi has undef as one of the incoming values, and an SSA value as the other, and the SSA value dominates the phi, replacing the phi with the SSA value is incorrect according to alive2.

Is this an actual bug?

https://alive2.llvm.org/ce/z/7RNy3W
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CC: @manasij7479

@akshayrdeodhar akshayrdeodhar changed the title [InstSimplify] simplifyPHINode phi fold incorrect according to alive [InstSimplify] simplifyPHINode phi fold incorrect according to alive2 Nov 7, 2024
@dtcxzyw dtcxzyw added the duplicate Resolved as duplicate label Nov 7, 2024
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dtcxzyw commented Nov 7, 2024

Duplicate of #68683.

@nikic nikic closed this as not planned Won't fix, can't repro, duplicate, stale Nov 7, 2024
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@nikic @EugeneZelenko @dtcxzyw @akshayrdeodhar