add -fbounds-checking option.
When enabled, clang generates bounds checks for array and pointers dereferences. Work to follow in LLVM's backend.

OK'ed by Chad; thanks for the review.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156431 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 0635be6..3a7efbc 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -675,6 +675,8 @@
     Res.push_back("-fno-operator-names");
   if (Opts.PascalStrings)
     Res.push_back("-fpascal-strings");
+  if (Opts.BoundsChecking > 0)
+    Res.push_back("-fbounds-checking=" + llvm::utostr(Opts.BoundsChecking));
   if (Opts.CatchUndefined)
     Res.push_back("-fcatch-undefined-behavior");
   if (Opts.AddressSanitizer)
@@ -1953,7 +1955,11 @@
     Opts.ObjCNonFragileABI2 = true;
   Opts.ObjCDefaultSynthProperties =
     Args.hasArg(OPT_fobjc_default_synthesize_properties);
-  Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior);
+  Opts.BoundsChecking = 0;
+  if ((Opts.CatchUndefined = Args.hasArg(OPT_fcatch_undefined_behavior)))
+    Opts.BoundsChecking = 5;
+  Opts.BoundsChecking = Args.getLastArgIntValue(OPT_fbounds_checking_EQ,
+                                                Opts.BoundsChecking, Diags);
   Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls);
   Opts.PackStruct = Args.getLastArgIntValue(OPT_fpack_struct_EQ, 0, Diags);
   Opts.PICLevel = Args.getLastArgIntValue(OPT_pic_level, 0, Diags);