Add docs

Author: wzssyqa

clang/docs/LanguageExtensions.rst

@@ -818,7 +818,23 @@ of different sizes and signs is forbidden in binary and ternary builtins.
  T __builtin_elementwise_fmod(T x, T y)         return The floating-point remainder of (x/y) whose sign                floating point types
                                                 matches the sign of x.
  T __builtin_elementwise_max(T x, T y)          return x or y, whichever is larger                                     integer and floating point types
+                                                For floating point types, follows semantics of maxNum
+                                                in IEEE 754-2008. See `LangRef
+                                                <http://llvm.org/docs/LangRef.html#llvm-min-intrinsics-comparation>`_
+                                                for the comparison.
  T __builtin_elementwise_min(T x, T y)          return x or y, whichever is smaller                                    integer and floating point types
+                                                For floating point types, follows semantics of minNum
+                                                in IEEE 754-2008. See `LangRef
+                                                <http://llvm.org/docs/LangRef.html#llvm-min-intrinsics-comparation>`_
+                                                for the comparison.
+ T __builtin_elementwise_maxnum(T x, T y)       return x or y, whichever is larger. Follows IEEE 754-2008              floating point types
+                                                semantics (maxNum) with +0.0>-0.0. See `LangRef
+                                                <http://llvm.org/docs/LangRef.html#llvm-min-intrinsics-comparation>`_
+                                                for the comparison.
+ T __builtin_elementwise_minnum(T x, T y)       return x or y, whichever is smaller. Follows IEEE 754-2008             floating point types
+                                                semantics (minNum) with +0.0>-0.0. See `LangRef
+                                                <http://llvm.org/docs/LangRef.html#llvm-min-intrinsics-comparation>`_
+                                                for the comparison.
  T __builtin_elementwise_add_sat(T x, T y)      return the sum of x and y, clamped to the range of                     integer types
                                                 representable values for the signed/unsigned integer type.
  T __builtin_elementwise_sub_sat(T x, T y)      return the difference of x and y, clamped to the range of              integer types