Implement support for -fwrapv, rdar://7221421

As part of this, pull together trapv handling into the same enum.

This also add support for NSW multiplies.

This also makes PCH disagreement on overflow behavior silent, since it
really doesn't matter except for warnings and codegen (no macros get 
defined etc).

llvm-svn: 106956

1 files changed, 10 insertions, 4 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index e7a75a6..76770ae 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -549,8 +549,11 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-femit-all-decls");
   if (Opts.MathErrno)
     Res.push_back("-fmath-errno");
-  if (Opts.OverflowChecking)
-    Res.push_back("-ftrapv");
+  switch (Opts.getSignedOverflowBehavior()) {
+  case LangOptions::SOB_Undefined: break;
+  case LangOptions::SOB_Defined:   Res.push_back("-fwrapv"); break;
+  case LangOptions::SOB_Trapping:  Res.push_back("-ftrapv"); break;
+  }
   if (Opts.HeinousExtensions)
     Res.push_back("-fheinous-gnu-extensions");
   // Optimize is implicit.
@@ -1257,8 +1260,11 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
 
   if (Args.hasArg(OPT_fvisibility_inlines_hidden))
     Opts.InlineVisibilityHidden = 1;
-    
-  Opts.OverflowChecking = Args.hasArg(OPT_ftrapv);
+  
+  if (Args.hasArg(OPT_ftrapv))
+    Opts.setSignedOverflowBehavior(LangOptions::SOB_Trapping); 
+  else if (Args.hasArg(OPT_fwrapv))
+    Opts.setSignedOverflowBehavior(LangOptions::SOB_Defined); 
 
   // Mimicing gcc's behavior, trigraphs are only enabled if -trigraphs
   // is specified, or -std is set to a conforming mode.