[PATCH] D148230: ValueTracking: fadd +0 cannot return -0

[Jay Foad via Phabricator via llvm-commits]

foad added inline comments.


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Comment at: llvm/include/llvm/Analysis/ValueTracking.h:281
+  /// Return true if it's known this can never be a positive subnormal
+  bool isKnownNeverPosSubnormal() const {
+    return isKnownNever(fcPosSubnormal);
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Matter of taste I guess, but I don't think a helper function this simple actually helps.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:3936
   return isKnownNeverNegZero() &&
          (isKnownNeverNegSubnormal() || inputDenormalIsIEEE(F, Ty));
 }
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Could use inputDenormalIsIEEEOrPosZero here.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:3943
+  return isKnownNeverPosZero() &&
+         (isKnownNeverSubnormal() || inputDenormalIsIEEEOrPosZero(F, Ty));
+}
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This doesn't work. If denormal mode is PosZero then a denormal can be flushed to +0, so this function should return false.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D148230/new/

https://reviews.llvm.org/D148230