Implement runtime checks for undefined behavior.  WIP.

This implements a new flag -fcatch-undefined-behavior.  The flag turns
on additional runtime checks for:

  T a[I];

  a[i]    abort when i < 0 or i >= I.

Future stuff includes shifts by >= bitwidth amounts.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91198 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 1d82d82..4279db5 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -895,6 +895,7 @@
   }
 
   // Forward -f (flag) options which we can pass directly.
+  Args.AddLastArg(CmdArgs, options::OPT_fcatch_undefined_behavior);
   Args.AddLastArg(CmdArgs, options::OPT_femit_all_decls);
   Args.AddLastArg(CmdArgs, options::OPT_ffreestanding);
   Args.AddLastArg(CmdArgs, options::OPT_fheinous_gnu_extensions);