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.

llvm-svn: 91198

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -32,10 +32,11 @@ CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
     SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
     CXXThisDecl(0), CXXVTTDecl(0),
     ConditionalBranchLevel(0), TerminateHandler(0),
-    UniqueAggrDestructorCount(0) {
+    UniqueAggrDestructorCount(0), AbortBB(0) {
   LLVMIntTy = ConvertType(getContext().IntTy);
   LLVMPointerWidth = Target.getPointerWidth(0);
   Exceptions = getContext().getLangOptions().Exceptions;
+  CatchUndefined = getContext().getLangOptions().CatchUndefined;
 }
 
 ASTContext &CodeGenFunction::getContext() const {