r233238 - Add an explanatory comment as to why we're turning on and off

[Eric Christopher]

Author: echristo
Date: Wed Mar 25 19:50:13 2015
New Revision: 233238

URL: http://llvm.org/viewvc/llvm-project?rev=233238&view=rev
Log:
Add an explanatory comment as to why we're turning on and off
certain other options as aliases. There be dragons here.

Modified:
    cfe/trunk/include/clang/Driver/Options.td

Modified: cfe/trunk/include/clang/Driver/Options.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/Options.td?rev=233238&r1=233237&r2=233238&view=diff
==============================================================================
--- cfe/trunk/include/clang/Driver/Options.td (original)
+++ cfe/trunk/include/clang/Driver/Options.td Wed Mar 25 19:50:13 2015
@@ -1187,6 +1187,9 @@ def mno_sse3 : Flag<["-"], "mno-sse3">,
 def mno_sse4a : Flag<["-"], "mno-sse4a">, Group<m_x86_Features_Group>;
 def mno_sse4_1 : Flag<["-"], "mno-sse4.1">, Group<m_x86_Features_Group>;
 def mno_sse4_2 : Flag<["-"], "mno-sse4.2">, Group<m_x86_Features_Group>;
+// -mno-sse4 turns off sse4.1 which has the effect of turning off everything
+// later than 4.1. -msse4 turns on 4.2 which has the effect of turning on
+// everything earlier than 4.2.
 def mno_sse4 : Flag<["-"], "mno-sse4">, Alias<mno_sse4_1>;
 def mno_sse : Flag<["-"], "mno-sse">, Group<m_x86_Features_Group>;
 def mno_ssse3 : Flag<["-"], "mno-ssse3">, Group<m_x86_Features_Group>;