Allow removal of obsolete map checks after transitions.

src/hydrogen-instructions.cc

 // Copyright 2012 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 1144 matching lines @@
     case IS_SYMBOL:
       *mask = kIsSymbolMask;
       *tag = kSymbolTag;
       return;
     default:
       UNREACHABLE();
   }
 }
 
 
+void HCheckMaps::SetSideEffectDominator(GVNFlag side_effect,
+                                        HValue* dominator) {
+  ASSERT(side_effect == kChangesMaps);
+  // TODO(mstarzinger): For now we specialize on HStoreNamedField, but once
+  // type information is rich enough we should generalize this to any HType
+  // for which the map is known.
+  if (dominator->IsStoreNamedField()) {
+    HStoreNamedField* store = HStoreNamedField::cast(dominator);
+    Handle<Map> map = store->transition();
+    if (map.is_null() || store->object() != value()) return;
+    for (int i = 0; i < map_set()->length(); i++) {
+      if (map.is_identical_to(map_set()->at(i))) {
+        DeleteAndReplaceWith(NULL);
+        return;
+      }
+    }
+  }
+}
+
+
 void HLoadElements::PrintDataTo(StringStream* stream) {
   value()->PrintNameTo(stream);
   if (HasTypeCheck()) {
     stream->Add(" ");
     typecheck()->PrintNameTo(stream);
   }
 }
 
 
 void HCheckMaps::PrintDataTo(StringStream* stream) {
@@ skipping 1630 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal