Update docs for fast-math flags.

This adds fneg, phi and select to the list of operations that may use
fast-math flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@375250 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index d2fe2ac..c3f4011 100644
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -2459,9 +2459,10 @@
 Fast-Math Flags
 ---------------
 
-LLVM IR floating-point operations (:ref:`fadd <i_fadd>`,
+LLVM IR floating-point operations (:ref:`fneg <i_fneg>`, :ref:`fadd <i_fadd>`,
 :ref:`fsub <i_fsub>`, :ref:`fmul <i_fmul>`, :ref:`fdiv <i_fdiv>`,
-:ref:`frem <i_frem>`, :ref:`fcmp <i_fcmp>`) and :ref:`call <i_call>`
+:ref:`frem <i_frem>`, :ref:`fcmp <i_fcmp>`), :ref:`phi <i_phi>`,
+:ref:`select <i_select>` and :ref:`call <i_call>`
 may use the following flags to enable otherwise unsafe
 floating-point transformations.