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

certain other options as aliases. There be dragons here.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@233238 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index bab4be9a433c657313eacbf07c78ab5fb2b8f45d..593969c72f12b520093d6876568a4da9719c738f 100644 (file)
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -1187,6 +1187,9 @@ def mno_sse3 : Flag<["-"], "mno-sse3">, Group<m_x86_Features_Group>;
 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>;