MIR Serialization: print and parse LLVM IR using MIR format.

This commit is the initial commit for the MIR serialization project.
It creates a new library under CodeGen called 'MIR'. This new
library adds a new machine function pass that prints out the LLVM IR 
using the MIR format. This pass is then added as a last pass when a 
'stop-after' option is used in llc. The new library adds the initial 
functionality for parsing of MIR files as well. This commit also 
extends the llc tool so that it can recognize and parse MIR input files.

Reviewers: Duncan P. N. Exon Smith, Matthias Braun, Philip Reames

Differential Revision: http://reviews.llvm.org/D9616


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237708 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LLVMTargetMachine.cpp

@@ -150,12 +150,7 @@ bool LLVMTargetMachine::addPassesToEmitFile(
     return true;
 
   if (StopAfter) {
-    // FIXME: The intent is that this should eventually write out a YAML file,
-    // containing the LLVM IR, the machine-level IR (when stopping after a
-    // machine-level pass), and whatever other information is needed to
-    // deserialize the code and resume compilation.  For now, just write the
-    // LLVM IR.
-    PM.add(createPrintModulePass(Out));
+    PM.add(createPrintMIRPass(outs()));
     return false;
   }