[LoopSimplifyCFG] Suppress expensive DomTree verification

This patch makes verification level lower for builds with
inexpensive checks.

Differential Revision: https://reviews.llvm.org/D61055

llvm-svn: 359446
diff --git a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
index b565cb9..9fa4afb 100644
--- a/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
@@ -598,7 +598,13 @@
 
 #ifndef NDEBUG
     // Make sure that we have preserved all data structures after the transform.
-    assert(DT.verify() && "DT broken after transform!");
+#if defined(EXPENSIVE_CHECKS)
+    assert(DT.verify(DominatorTree::VerificationLevel::Full) &&
+           "DT broken after transform!");
+#else
+    assert(DT.verify(DominatorTree::VerificationLevel::Fast) &&
+           "DT broken after transform!");
+#endif
     assert(DT.isReachableFromEntry(Header));
     LI.verify(DT);
 #endif