[PATCH] D149112: InstCombine: Try to turn is.fpclass sign checks to fcmp with 0

[Jay Foad via Phabricator via llvm-commits]

foad added inline comments.


================
Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:826
+
 /// \returns true if the test performed by llvm.is.fpclass(x, \p Mask) is
+/// equivalent to fcmp o__ x, 0.0 with the floating-point environment assumed
----------------
foad wrote:
> "returns true" needs updating.
ping


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp:848-851
+  case fcPosSubnormal | fcPosNormal | fcPosInf:
+    if (inputDenormalIsIEEE(F, Ty))
+      return FCmpInst::FCMP_OGT;
+    break;
----------------
arsenm wrote:
> foad wrote:
> > Any reason not to add the DAZ counterpart of this case, i.e. `fcPosNormal | fcPosInf`? And the same for OLT.
> It is already handled, this is called twice. The second time with the inverted mask (so actually we have some redundant cases here). I could either expand all the cases here and stop doing the invert trick, or trim the redundant cases 
Yeah, now it looks odd that the two FMP_ONE cases are missing.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D149112/new/

https://reviews.llvm.org/D149112