Extend TargetPassConfig to allow running only a subset of the normal passes.

This is still a work in progress but I believe it is currently good enough
to fix PR13122 "Need unit test driver for codegen IR passes".  For example,
you can run llc with -stop-after=loop-reduce to have it dump out the IR after
running LSR.  Serializing machine-level IR is not yet supported but we have
some patches in progress for that.

The plan is to serialize the IR to a YAML file, containing separate sections
for the LLVM IR, machine-level IR, and whatever other info is needed.  Chad
suggested that we stash the stop-after pass in the YAML file and use that
instead of the start-after option to figure out where to restart the
compilation.  I think that's a great idea, but since it's not implemented yet
I put the -start-after option into this patch for testing purposes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159570 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/CppBackend/CPPTargetMachine.h b/lib/Target/CppBackend/CPPTargetMachine.h
index 92bca6c..9cbe798 100644
--- a/lib/Target/CppBackend/CPPTargetMachine.h
+++ b/lib/Target/CppBackend/CPPTargetMachine.h
@@ -31,7 +31,9 @@
   virtual bool addPassesToEmitFile(PassManagerBase &PM,
                                    formatted_raw_ostream &Out,
                                    CodeGenFileType FileType,
-                                   bool DisableVerify);
+                                   bool DisableVerify,
+                                   AnalysisID StartAfter,
+                                   AnalysisID StopAfter);
 
   virtual const TargetData *getTargetData() const { return 0; }
 };