[PGO][PGSO] SizeOpts changes.

Summary:
(Split of off D67120)

SizeOpts/MachineSizeOpts changes for profile guided size optimization.

(A second try after previously committed as r375254 and reverted as r375375.)

Subscribers: mgorny, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69409
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index 1d561c3..b2e76e2 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -93,6 +93,7 @@
   MachineRegisterInfo.cpp
   MachineScheduler.cpp
   MachineSink.cpp
+  MachineSizeOpts.cpp
   MachineSSAUpdater.cpp
   MachineTraceMetrics.cpp
   MachineVerifier.cpp