[PATCH] D158648: InstCombine: Introduce SimplifyDemandedUseFPClass

Matt Arsenault via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Wed Sep 13 07:16:45 PDT 2023

arsenm added inline comments.

Comment at: llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp:1846
+    case Intrinsic::fabs:
+      if (SimplifyDemandedFPClass(I, 0, llvm::fabs(DemandedMask), Known,
+                                  Depth + 1))
RKSimon wrote:
> arsenm wrote:
> > RKSimon wrote:
> > > nikic wrote:
> > > > It seems like this is correct, but only because `fabs(FPClassTest)` apparently does the exact opposite of what one would expect it to do. It's really `inverse_fabs()`.
> > > Do we need a llvm::inverse_fabs() ? Or at least a comment describing the behaviour
> > This probably just needs to be renamed, this is what it is. Not sure that's the right name, make_sign_insensitive or something maybe? unknown_sign?
> unknown_sign makes sense to me
OK, I can do that in a separate change. this is a pre-existing function 



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