[llvm] r292691 - [ValueTracking] Clarify comments on CannotBeOrderedLessThanZero and SignBitMustBeZero.

[Justin Lebar via llvm-commits]

Author: jlebar
Date: Fri Jan 20 18:59:40 2017
New Revision: 292691

URL: http://llvm.org/viewvc/llvm-project?rev=292691&view=rev
Log:
[ValueTracking] Clarify comments on CannotBeOrderedLessThanZero and SignBitMustBeZero.

Reviewers: hfinkel, efriedma, sanjoy

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28926

Modified:
    llvm/trunk/include/llvm/Analysis/ValueTracking.h

Modified: llvm/trunk/include/llvm/Analysis/ValueTracking.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/ValueTracking.h?rev=292691&r1=292690&r2=292691&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Analysis/ValueTracking.h (original)
+++ llvm/trunk/include/llvm/Analysis/ValueTracking.h Fri Jan 20 18:59:40 2017
@@ -167,13 +167,25 @@ template <typename T> class ArrayRef;
   bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
                             unsigned Depth = 0);
 
-  /// Return true if we can prove that the specified FP value is either a NaN or
-  /// never less than 0.0.
-  /// If \p IncludeNeg0 is false, -0.0 is considered less than 0.0.
+  /// Return true if we can prove that the specified FP value is either NaN or
+  /// never less than -0.0.
+  ///
+  ///      NaN --> true
+  ///       +0 --> true
+  ///       -0 --> true
+  ///   x > +0 --> true
+  ///   x < -0 --> false
+  ///
   bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI);
 
-  /// \returns true if we can prove that the specified FP value has a 0 sign
-  /// bit.
+  /// Return true if we can prove that the specified FP value's sign bit is 0.
+  ///
+  ///      NaN --> true/false (depending on the NaN's sign bit)
+  ///       +0 --> true
+  ///       -0 --> false
+  ///   x > +0 --> true
+  ///   x < -0 --> false
+  ///
   bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI);
 
   /// If the specified value can be set by repeating the same byte in memory,