add EP_OptimizerLast extension point

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153353 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/IPO/PassManagerBuilder.cpp b/lib/Transforms/IPO/PassManagerBuilder.cpp
index 8408437..243ba1a 100644
--- a/lib/Transforms/IPO/PassManagerBuilder.cpp
+++ b/lib/Transforms/IPO/PassManagerBuilder.cpp
@@ -202,6 +202,7 @@
     if (OptLevel > 1)
       MPM.add(createConstantMergePass());     // Merge dup global constants
   }
+  addExtensionsToPM(EP_OptimizerLast, MPM);
 }
 
 void PassManagerBuilder::populateLTOPassManager(PassManagerBase &PM,