Avoid copying flow-sensitive state when only a goto separates blocks.

src/hydrogen-flow-engine.h

Index: src/hydrogen-flow-engine.h
diff --git a/src/hydrogen-flow-engine.h b/src/hydrogen-flow-engine.h
index dfe43ec6c3ba94b3c38ee2aa2fb4c561ea390919..4e1275546f611e2401e467484976f73d59b3e784 100644
--- a/src/hydrogen-flow-engine.h
+++ b/src/hydrogen-flow-engine.h
@@ -138,12 +138,19 @@ class HFlowEngine {
       }
 
       // Propagate the block state forward to all successor blocks.
-      for (int i = 0; i < block->end()->SuccessorCount(); i++) {
+      int max = block->end()->SuccessorCount();
+      for (int i = 0; i < max; i++) {
         HBasicBlock* succ = block->end()->SuccessorAt(i);
         IncrementPredecessorCount(succ);
         if (StateAt(succ) == NULL) {
           // This is the first state to reach the successor.
-          SetStateAt(succ, state->Copy(succ, zone_));
+          if (max == 1 && succ->predecessors()->length() == 1) {
+            // Optimization: successor can inherit this state.
+            SetStateAt(succ, state);
+          } else {
+            // Successor needs a copy of the state.
+            SetStateAt(succ, state->Copy(succ, zone_));
+          }
         } else {
           // Merge the current state with the state already at the successor.
           SetStateAt(succ, state->Merge(succ, StateAt(succ), zone_));