Optimize the equality check case of ICCompare stubs.

src/hydrogen.cc

 // Copyright 2011 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 5980 matching lines @@
       return ast_context()->ReturnInstruction(result, expr->id());
     }
   } else if (op == Token::IN) {
     HIn* result = new(zone()) HIn(context, left, right);
     result->set_position(expr->position());
     return ast_context()->ReturnInstruction(result, expr->id());
   } else if (type_info.IsNonPrimitive()) {
     switch (op) {
       case Token::EQ:
       case Token::EQ_STRICT: {
-        AddInstruction(new(zone()) HCheckNonSmi(left));
-        AddInstruction(HCheckInstanceType::NewIsSpecObject(left));
-        AddInstruction(new(zone()) HCheckNonSmi(right));
-        AddInstruction(HCheckInstanceType::NewIsSpecObject(right));
-        HCompareObjectEqAndBranch* result =
-            new(zone()) HCompareObjectEqAndBranch(left, right);
-        result->set_position(expr->position());
-        return ast_context()->ReturnControl(result, expr->id());
+        // Can we get away with map check and not instance type check?
+        Handle<Map> map = oracle()->GetCompareMap(expr);
+        if (!map.is_null()) {
+          AddInstruction(new(zone()) HCheckNonSmi(left));
+          AddInstruction(new(zone()) HCheckMap(left, map));
+          AddInstruction(new(zone()) HCheckNonSmi(right));
+          AddInstruction(new(zone()) HCheckMap(right, map));
+          HCompareObjectEqAndBranch* result =
+              new(zone()) HCompareObjectEqAndBranch(left, right);
+          result->set_position(expr->position());
+          return ast_context()->ReturnControl(result, expr->id());
+        } else {
+          AddInstruction(new(zone()) HCheckNonSmi(left));
+          AddInstruction(HCheckInstanceType::NewIsSpecObject(left));
+          AddInstruction(new(zone()) HCheckNonSmi(right));
+          AddInstruction(HCheckInstanceType::NewIsSpecObject(right));
+          HCompareObjectEqAndBranch* result =
+              new(zone()) HCompareObjectEqAndBranch(left, right);
+          result->set_position(expr->position());
+          return ast_context()->ReturnControl(result, expr->id());
+        }
       }
       default:
         return Bailout("Unsupported non-primitive compare");
     }
   } else if (type_info.IsString() && oracle()->IsSymbolCompare(expr) &&
              (op == Token::EQ || op == Token::EQ_STRICT)) {
     AddInstruction(new(zone()) HCheckNonSmi(left));
     AddInstruction(HCheckInstanceType::NewIsSymbol(left));
     AddInstruction(new(zone()) HCheckNonSmi(right));
     AddInstruction(HCheckInstanceType::NewIsSymbol(right));
@@ skipping 1075 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal