[PATCH] D62158: [InstCombine] canonicalize minnum/maxnum with 'nnan' to fcmp+select

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

In D62158#1509118 <https://reviews.llvm.org/D62158#1509118>, @spatel wrote:

>




>> Also last I knew, the use of matchSelectPattern in SelectionDAGBuilder was somewhat buggy. It leaves behind a dead use, so in the initial combine, it breaks hasOneUse checks and prevents necessary early matching. There was also a second problem that I don't remember the details of
> 
> Ok, I didn't know there was a problem there. Do we have a bug report with an example?

No. IIRC I ran into this during r344914.  The FIXME for the regression on reduction_fast_min_pattern_v4f16 in test/CodeGen/AMDGPU/reduction.ll


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