[llvm] CodeGen: Strengthen definition of F{MIN|MAX}NUM_IEEE nodes (PR #85195)

[Jay Foad via llvm-commits]

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@@ -521,16 +521,32 @@ The return value of (FMAXNUM 0.0, -0.0) could be either 0.0 or -0.0.
 G_FMINNUM_IEEE
 ^^^^^^^^^^^^^^
 
-Perform floating-point minimum on two values, following the IEEE-754 2008
-definition. This differs from FMINNUM in the handling of signaling NaNs. If one
-input is a signaling NaN, returns a quiet NaN.
+Perform floating-point minimum on two values, following IEEE-754
+definitions. This differs from FMINNUM in the handling of signaling
+NaNs.
+
+If one input is a signaling NaN, returns a quiet NaN. This matches
+IEEE-754 2008's minnum/maxnum for signaling NaNs (which differs from
+2019).
+
+These treat -0 / as ordered less than +0, matching the behavior of
+IEEE-754 2019's minimumNumber/maximumNumber (which was unspecified
+in 2008).
 
 G_FMAXNUM_IEEE
 ^^^^^^^^^^^^^^
 
-Perform floating-point maximum on two values, following the IEEE-754 2008
-definition. This differs from FMAXNUM in the handling of signaling NaNs. If one
-input is a signaling NaN, returns a quiet NaN.
+Perform floating-point maximum on two values, following IEEE-754
+definitions. This differs from FMAXNUM in the handling of signaling
+NaNs.
+
+If one input is a signaling NaN, returns a quiet NaN. This matches
+IEEE-754 2008's minnum/maxnum for signaling NaNs (which differs from
+2019).
+
+These treat -0 / as ordered less than +0, matching the behavior of
----------------
jayfoad wrote:

Stray `/`

https://github.com/llvm/llvm-project/pull/85195