Don't propagate information through phis in loop headers.

src/hydrogen-check-elimination.cc

Index: src/hydrogen-check-elimination.cc
diff --git a/src/hydrogen-check-elimination.cc b/src/hydrogen-check-elimination.cc
index 5fdb3e3f3c48fa1260005eeeab7ec7e6ae537ebd..59b1b266844d455b9042d0505057013de47d3b4d 100644
--- a/src/hydrogen-check-elimination.cc
+++ b/src/hydrogen-check-elimination.cc
@@ -164,7 +164,7 @@ class HCheckTable : public ZoneObject {
     copy->size_ = size_;
 
     // Create entries for succ block's phis.
-    if (succ->phis()->length() > 0) {
+    if (!succ->IsLoopHeader() && succ->phis()->length() > 0) {
       int pred_index = succ->PredecessorIndexOf(from_block);
       for (int phi_index = 0;
            phi_index < succ->phis()->length();