[NewPassManager] Add tuning option: LoopUnrolling [clang-change]

Summary:
Use CodeGenOpts's setting for loop unrolling.
[to be coupled with D61618]

Reviewers: chandlerc

Subscribers: jlebar, dmgreen, cfe-commits, llvm-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61620

llvm-svn: 361653
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 1dbeec1..c5e56c7 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1051,6 +1051,7 @@
   }
 
   PipelineTuningOptions PTO;
+  PTO.LoopUnrolling = CodeGenOpts.UnrollLoops;
   // For historical reasons, loop interleaving is set to mirror setting for loop
   // unrolling.
   PTO.LoopInterleaving = CodeGenOpts.UnrollLoops;