[LoopInterchange] Incrementally update the dominator tree.

We can use incremental dominator tree updates to avoid re-calculating
the dominator tree after interchanging 2 loops.

Reviewers: dmgreen, kuhar

Reviewed By: kuhar

Differential Revision: https://reviews.llvm.org/D43176

llvm-svn: 325122
diff --git a/llvm/test/Transforms/LoopInterchange/call-instructions.ll b/llvm/test/Transforms/LoopInterchange/call-instructions.ll
index e2428ac..c33abde 100644
--- a/llvm/test/Transforms/LoopInterchange/call-instructions.ll
+++ b/llvm/test/Transforms/LoopInterchange/call-instructions.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -basicaa -loop-interchange -S | FileCheck %s
+; RUN: opt < %s -basicaa -loop-interchange -verify-dom-info -S | FileCheck %s
 ;; We test the complete .ll for adjustment in outer loop header/latch and inner loop header/latch.
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"