Optimize redundant HCompareMap instructions with known successors.

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 323 matching lines @@
       // If the instruction changes maps, it should be handled above.
       CHECK(!instr->CheckGVNFlag(kChangesMaps));
     }
   }
 
   void ReduceCompareMap(HCompareMap* instr) {
     MapSet maps = FindMaps(instr->value()->ActualValue());
     if (maps == NULL) return;
     if (maps->Contains(instr->map())) {
       if (maps->size() == 1) {
-        // TODO(titzer): replace with goto true branch
+        TRACE(("Marking redundant CompareMap #%d at B%d as true\n",
+            instr->id(), instr->block()->block_id()));
+        instr->set_known_successor_index(0);
         INC_STAT(compares_true_);
       }
     } else {
-      // TODO(titzer): replace with goto false branch
+      TRACE(("Marking redundant CompareMap #%d at B%d as false\n",
+          instr->id(), instr->block()->block_id()));
+      instr->set_known_successor_index(1);
       INC_STAT(compares_false_);
     }
   }
 
   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.
@@ skipping 221 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