[PATCH] D143195: ValueTracking: Add start of computeKnownFPClass API

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added inline comments.


================
Comment at: llvm/include/llvm/Analysis/ValueTracking.h:217-221
+  /// If the sign bit is definitively known to be 1.
+  bool SignBitKnownOne = false;
+
+  /// If the sign bit is definitively known to be 0.
+  bool SignBitKnownZero = false;
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jcranmer-intel wrote:
> Would it make sense instead to have a `std::optional<bool> KnownSignBit` here?
Annoyingly operator &/|/^ don't work on std::optional<bool> so I think this made some of the patch a bit uglier


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:4111-4113
+    // Cannot produce nan
+    Known.KnownFPClasses =
+        static_cast<FPClassTest>(Known.KnownFPClasses & ~fcNan & fcAllFlags);
----------------
jcranmer-intel wrote:
> This pattern is common enough that I think `KnownFPClass` should have a `ruleOut(FPClassTest)` method or something similar to implement this method.
knownNot?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143195/new/

https://reviews.llvm.org/D143195