[PATCH] D158068: [DAG] FoldSetCC - add missing icmp(X,undef) -> isTrueWhenEqual case

Mon Aug 21 09:15:15 PDT 2023

RKSimon added inline comments.

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Comment at: llvm/test/CodeGen/AMDGPU/swdev373493.ll:57
 bb:
   switch i32 undef, label %bb9 [
     i32 3, label %bb8
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arsenm wrote:
> yassingh wrote:
> > RKSimon wrote:
> > > nikic wrote:
> > > > Don't switch on undef...
> > > @yassingh This was added at D141895 - can this be replaced with the switch i32 %arg?
> > This came up in that review too. The test in question was generated by a lot of automatic reductions over a larger failure, I couldn't get rid of undef then either. 
> You need to replace it with a uniform value. If you just add a regular function argument, it will be divergent which is a much more radical change. The easiest update would probably be to swap the triple to amdpal from amdhsa, use amdgpu_gfx for the calling convention and make the new argument inreg
@yassingh Alternative to D158359 - could you run the original reduction again with this patch applied but D141895 disabled?

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  https://reviews.llvm.org/D158068/new/

https://reviews.llvm.org/D158068