[PATCH] D54001: [ValueTracking] determine sign of 0.0 from select when matching min/max FP

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: efriedma, arsenm, RKSimon.
Herald added subscribers: wdng, mcrosier.

In PR39475:
https://bugs.llvm.org/show_bug.cgi?id=39475
..we may fail to recognize/simplify fabs() in some cases because we do not canonicalize fcmp with a -0.0 operand.

Adding that canonicalization can cause regressions on min/max FP tests, so that's this patch: for the purpose of determining whether something is min/max, let the value returned by the select determine how we treat a 0.0 operand in the fcmp.

This patch doesn't actually change the -0.0 to +0.0. It just changes the analysis, so we don't fail to recognize equivalent min/max patterns that only differ in the signbit of 0.0.


https://reviews.llvm.org/D54001

Files:
  lib/Analysis/ValueTracking.cpp
  test/Transforms/InstCombine/minmax-fp.ll
  unittests/Analysis/ValueTrackingTest.cpp

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