[clang] [llvm] [LangRef] Clarify specification for float min/max operations (PR #172012)

[Nikita Popov via cfe-commits]

================
@@ -17305,95 +17305,44 @@ The returned value is completely identical to the input except for the sign bit;
 in particular, if the input is a NaN, then the quiet/signaling bit and payload
 are perfectly preserved.
 
-.. _i_fminmax_family:
+Floating-point min/max intrinsics comparison
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-'``llvm.min.*``' Intrinsics Comparation
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LLVM supports three pairs of floating-point min/max intrinsics, which differ
+in their handling of :ref:`NaN values <floatnan>`:
 
-Standard:
-"""""""""
+ * ``llvm.minimum`` and ``llvm.maximum``: Return NaN if one the arguments is
+   NaN.
+ * ``llvm.minimumnum`` and ``llvm.maximumnum``: Return the other argument if
+   one of the arguments is NaN.
+ * ``llvm.minnum`` and ``llvm.maxnum``: For quiet NaNs behaves like
+   minimumnum/maximumnum. For signaling NaNs, non-deterministically returns
+   NaN or the other operand.
 
-IEEE754 and ISO C define some min/max operations, and they have some differences
-on working with qNaN/sNaN and +0.0/-0.0. Here is the list:
+Additionally, each of these intrinsics supports two behaviors for signed zeroes.
+By default, -0.0 is considered smaller than +0.0. If the ``nsz`` flag is
+specified, the order is non-deterministic.
----------------
nikic wrote:

Done.

https://github.com/llvm/llvm-project/pull/172012