Rename LowerSubregs to ExpandPostRAPseudos.

I'll fix the file contents in the next commit.

This pass is currently expanding the COPY and SUBREG_TO_REG pseudos. I
am going to add a hook so targets can expand more pseudo-instructions
after register allocation.

Many targets have pseudo-instructions that assist the register
allocator.  They can be expanded after register allocation, before PEI
and PostRA scheduling.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140469 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CMakeLists.txt

@@ -14,6 +14,7 @@ add_llvm_library(LLVMCodeGen
   ELFCodeEmitter.cpp
   ELFWriter.cpp
   ExpandISelPseudos.cpp
+  ExpandPostRAPseudos.cpp
   GCMetadata.cpp
   GCMetadataPrinter.cpp
   GCStrategy.cpp
@@ -33,7 +34,6 @@ add_llvm_library(LLVMCodeGen
   LiveRangeCalc.cpp
   LiveRangeEdit.cpp
   LocalStackSlotAllocation.cpp
-  LowerSubregs.cpp
   MachineBasicBlock.cpp
   MachineBlockFrequencyInfo.cpp
   MachineBranchProbabilityInfo.cpp