Default lowering for experimental.widenable.condition

Introduces a pass that provides default lowering strategy for the
`experimental.widenable.condition` intrinsic, replacing all its uses with
`i1 true`.

Differential Revision: https://reviews.llvm.org/D56096
Reviewed By: reames

llvm-svn: 352739
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
index f357772..c91ffda 100644
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -80,6 +80,7 @@
   initializeLowerAtomicLegacyPassPass(Registry);
   initializeLowerExpectIntrinsicPass(Registry);
   initializeLowerGuardIntrinsicLegacyPassPass(Registry);
+  initializeLowerWidenableConditionLegacyPassPass(Registry);
   initializeMemCpyOptLegacyPassPass(Registry);
   initializeMergeICmpsPass(Registry);
   initializeMergedLoadStoreMotionLegacyPassPass(Registry);