[LangRef] clarify semantics of the frem instruction

As noted in D40594, the frem instruction corresponds to fmod() except that it can't set errno.
I modified the text that we currently use for intrinsics that map to libm functions and applied
it to frem.

Differential Revision: https://reviews.llvm.org/D40629

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319437 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index a091cc1dd2ae79450927977db480196598c02338..dbd456667772cb5abe66fac39affecc016ed125f 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -6827,10 +6827,12 @@ Both arguments must have identical types.
 Semantics:
 """"""""""
 
-This instruction returns the *remainder* of a division. The remainder
-has the same sign as the dividend. This instruction can also take any
-number of :ref:`fast-math flags <fastmath>`, which are optimization hints
-to enable otherwise unsafe floating point optimizations:
+Return the same value as a libm '``fmod``' function but without trapping or 
+setting ``errno``.
+
+The remainder has the same sign as the dividend. This instruction can also 
+take any number of :ref:`fast-math flags <fastmath>`, which are optimization
+hints to enable otherwise unsafe floating-point optimizations:
 
 Example:
 """"""""