Update domtree incrementally in loop peeling.

With this change dominator tree remains in sync after each step of loop
peeling.

Differential Revision: https://reviews.llvm.org/D29029

llvm-svn: 292895
diff --git a/llvm/test/Transforms/LoopUnroll/peel-loop.ll b/llvm/test/Transforms/LoopUnroll/peel-loop.ll
index 2491220..bf0801f 100644
--- a/llvm/test/Transforms/LoopUnroll/peel-loop.ll
+++ b/llvm/test/Transforms/LoopUnroll/peel-loop.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -S -loop-unroll -unroll-force-peel-count=3 -simplifycfg -instcombine | FileCheck %s
+; RUN: opt < %s -S -loop-unroll -unroll-force-peel-count=3 -verify-dom-info -simplifycfg -instcombine | FileCheck %s
 
 ; Basic loop peeling - check that we can peel-off the first 3 loop iterations
 ; when explicitly requested.