Reland rL312315: [MergeICmps] MergeICmps is a new optimization pass that turns chains of integer

Add missing header.

This reverts commit 86dd6335cf7607af22f383a9a8e072ba929848cf.

llvm-svn: 312322
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index ce6f93e..d41fe6a 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -73,6 +73,7 @@
   initializeLowerExpectIntrinsicPass(Registry);
   initializeLowerGuardIntrinsicLegacyPassPass(Registry);
   initializeMemCpyOptLegacyPassPass(Registry);
+  initializeMergeICmpsPass(Registry);
   initializeMergedLoadStoreMotionLegacyPassPass(Registry);
   initializeNaryReassociateLegacyPassPass(Registry);
   initializePartiallyInlineLibCallsLegacyPassPass(Registry);