Add -f[no-]strict-overflow to the Clang driver. Use it to set the

default for -fwrapv if that flag isn't specified explicitly. We always
prefer an explict setting of -fwrapv when present. Also adds support for
-fno-wrapv to allow disabling -fwrapv even when -fno-strict-overflow is
passed.

llvm-svn: 128353

1 files changed, 11 insertions, 1 deletions

diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index beaeade836c..81585c85674 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -1448,7 +1448,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     CmdArgs.push_back(A->getValue(Args));
   }
 
-  Args.AddLastArg(CmdArgs, options::OPT_fwrapv);
+  // -fno-strict-overflow implies -fwrapv if it isn't disabled, but
+  // -fstrict-overflow won't turn off an explicitly enabled -fwrapv.
+  if (Arg *A = Args.getLastArg(options::OPT_fwrapv,
+                               options::OPT_fno_wrapv)) {
+    if (A->getOption().matches(options::OPT_fwrapv))
+      CmdArgs.push_back("-fwrapv");
+  } else if (Arg *A = Args.getLastArg(options::OPT_fstrict_overflow,
+                                      options::OPT_fno_strict_overflow)) {
+    if (A->getOption().matches(options::OPT_fno_strict_overflow))
+      CmdArgs.push_back("-fwrapv");
+  }
   Args.AddLastArg(CmdArgs, options::OPT_fwritable_strings);
   Args.AddLastArg(CmdArgs, options::OPT_funroll_loops);