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[DAG] SimplifySetCC - failure to simplify icmp(not(x),not(y)) -> icmp(y, x) patterns #61120

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RKSimon opened this issue Mar 2, 2023 · 1 comment
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[DAG] SimplifySetCC - failure to simplify icmp(not(x),not(y)) -> icmp(y, x) patterns #61120

RKSimon opened this issue Mar 2, 2023 · 1 comment
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llvm:codegen missed-optimization

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@RKSimon
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RKSimon commented Mar 2, 2023 •
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https://godbolt.org/z/E4rjf9se4

This is handled in instcombine, but under certain circumstances they can appear in the DAG as well (noticed while trying to improve ABD expansion on x86).

We do get the EQ/NE cases indirectly via the fold: (X^Y) == (X^Z) --> Y == Z
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junaire commented Mar 21, 2023

Hi @RKSimon , I would like to work on this. I've created https://reviews.llvm.org/D146512.

@junaire junaire self-assigned this Mar 21, 2023
junaire added a commit that referenced this issue Mar 23, 2023
@junaire
Precommit test for #61120
1c420cd 
Signed-off-by: Jun Zhang <jun@junz.org>
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