[MIR] MIRNamer pass for improving MIR test authoring experience.

This patch reuses the MIR vreg renamer from the MIRCanonicalizerPass to cleanup
names of vregs in a MIR file for MIR test authors. I found it useful when
writing a regression test for a globalisel failure I encountered recently and
thought it might be useful for other folks as well.

Differential Revision: https://reviews.llvm.org/D67209

llvm-svn: 371121
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 1228a2d..3cf0c60 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -122,6 +122,7 @@
   RegisterScavenging.cpp
   RenameIndependentSubregs.cpp
   MIRVRegNamerUtils.cpp
+  MIRNamerPass.cpp
   MIRCanonicalizerPass.cpp
   RegisterUsageInfo.cpp
   RegUsageInfoCollector.cpp