Split -fsanitize=bounds to -fsanitize=array-bounds (for the frontend-inserted

check using the ubsan runtime) and -fsanitize=local-bounds (for the middle-end
check which inserts traps).

Remove -fsanitize=local-bounds from -fsanitize=undefined. It does not produce
useful diagnostics and has false positives (PR17635), and is not a good
compromise position between UBSan's checks and ASan's checks.

Map -fbounds-checking to -fsanitize=local-bounds to restore Clang's historical
behavior for that flag.

llvm-svn: 193205

clang/lib/CodeGen/BackendUtil.cpp

@@ -245,7 +245,7 @@ void EmitAssemblyHelper::CreatePasses(TargetMachine *TM) {
                            addObjCARCOptPass);
   }
 
-  if (LangOpts.Sanitize.Bounds) {
+  if (LangOpts.Sanitize.LocalBounds) {
     PMBuilder.addExtension(PassManagerBuilder::EP_ScalarOptimizerLate,
                            addBoundsCheckingPass);
     PMBuilder.addExtension(PassManagerBuilder::EP_EnabledOnOptLevel0,