Check elimination now sets known successor branch of HCompareObjectEqAndBranch (correctness fix).

src/hydrogen-check-elimination.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 70 matching lines @@
         break;
       }
       case HValue::kStoreNamedField: {
         ReduceStoreNamedField(HStoreNamedField::cast(instr));
         break;
       }
       case HValue::kCompareMap: {
         ReduceCompareMap(HCompareMap::cast(instr));
         break;
       }
+      case HValue::kCompareObjectEqAndBranch: {
+        ReduceCompareObjectEqAndBranch(HCompareObjectEqAndBranch::cast(instr));
+        break;
+      }
       case HValue::kTransitionElementsKind: {
         ReduceTransitionElementsKind(
             HTransitionElementsKind::cast(instr));
         break;
       }
       case HValue::kCheckMapValue: {
         ReduceCheckMapValue(HCheckMapValue::cast(instr));
         break;
       }
       case HValue::kCheckHeapObject: {
@@ skipping 371 matching lines @@
 
     TRACE(("Marking redundant CompareMap #%d for #%d at B%d as %s\n",
         instr->id(), instr->value()->id(), instr->block()->block_id(),
         succ == 0 ? "true" : "false"));
     instr->set_known_successor_index(succ);
 
     int unreachable_succ = 1 - succ;
     instr->block()->MarkSuccEdgeUnreachable(unreachable_succ);
   }
 
+  void ReduceCompareObjectEqAndBranch(HCompareObjectEqAndBranch* instr) {
+    MapSet maps_left = FindMaps(instr->left()->ActualValue());
+    if (maps_left == NULL) return;
+    MapSet maps_right = FindMaps(instr->right()->ActualValue());
+    if (maps_right == NULL) return;
+    MapSet intersection = maps_left->Intersect(maps_right, phase_->zone());
+    if (intersection->size() > 0) return;
+
+    TRACE(("Marking redundant CompareObjectEqAndBranch #%d at B%d as false\n",
+        instr->id(), instr->block()->block_id()));
+    int succ = 1;
+    instr->set_known_successor_index(succ);
+
+    int unreachable_succ = 1 - succ;
+    instr->block()->MarkSuccEdgeUnreachable(unreachable_succ);
+  }
+
   void ReduceTransitionElementsKind(HTransitionElementsKind* instr) {
     MapSet maps = FindMaps(instr->object()->ActualValue());
     // Can only learn more about an object that already has a known set of maps.
     if (maps == NULL) return;
     if (maps->Contains(instr->original_map())) {
       // If the object has the original map, it will be transitioned.
       maps->Remove(instr->original_map());
       maps->Add(instr->transitioned_map(), phase_->zone());
     } else {
       // Object does not have the given map, thus the transition is redundant.
@@ skipping 223 matching lines @@
   PRINT_STAT(removed_cho);
   PRINT_STAT(narrowed);
   PRINT_STAT(loads);
   PRINT_STAT(empty);
   PRINT_STAT(compares_true);
   PRINT_STAT(compares_false);
   PRINT_STAT(transitions);
 }
 
 } }  // namespace v8::internal