Factor FlattenCFG out from SimplifyCFG

Patch by: Mei Ye

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187764 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 6355204..a6b3f4e 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -235,7 +235,7 @@
   }
 
   MPM.add(createAggressiveDCEPass());         // Delete dead instructions
-  MPM.add(createCFGSimplificationPass(true)); // Merge & remove BBs
+  MPM.add(createCFGSimplificationPass()); // Merge & remove BBs
   MPM.add(createInstructionCombiningPass());  // Clean up after everything.
 
   // As an experimental mode, run any vectorization passes in a separate
@@ -371,7 +371,7 @@
   PM.add(createJumpThreadingPass());
 
   // Delete basic blocks, which optimization passes may have killed.
-  PM.add(createCFGSimplificationPass(true));
+  PM.add(createCFGSimplificationPass());
 
   // Now that we have optimized the program, discard unreachable functions.
   PM.add(createGlobalDCEPass());