[PATCH] D138180: InstCombine: Fold negations of is_fpclass intrinsics

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp:3715-3717
+      II->setArgOperand(
+          1, ConstantInt::get(ClassMask->getType(),
+                              ~ClassMask->getZExtValue() & fcAllFlags));
----------------
sepavloff wrote:
> It must work for IEEE numbers. But for non-IEEE it is possible that a value does not belong to any of the classes known to `is_fpclass`. For example, type `x86_fp80` has so-called unsupported values. Do you think this transformation can be safely applied to such numbers also or it is better to limit it to IEEE numbers only?
I don't know anything about x87. How is the intrinsic lowered for it?

Is it just these "pseudo-X" cases? I'd assume those are covered by the non-pseudo tests?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D138180/new/

https://reviews.llvm.org/D138180