[CodeGen] Split SafeStack into a LegacyPass and a utility. NFC.

This lets the pass focus on gathering the required analyzes, and the
utility class focus on the transformation.

Differential Revision: https://reviews.llvm.org/D31303

llvm-svn: 302609
diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index 3fc12cc..871006c 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -79,7 +79,7 @@
   initializeRAGreedyPass(Registry);
   initializeRegisterCoalescerPass(Registry);
   initializeRenameIndependentSubregsPass(Registry);
-  initializeSafeStackPass(Registry);
+  initializeSafeStackLegacyPassPass(Registry);
   initializeShrinkWrapPass(Registry);
   initializeSlotIndexesPass(Registry);
   initializeStackColoringPass(Registry);