Stub Cache: speed up load callback accessor by allocating data handle on stack.

src/ia32/stub-cache-ia32.cc

 // Copyright 2006-2009 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 429 matching lines @@
   __ j(zero, miss, not_taken);
 
   // Check that the maps haven't changed.
   Register reg =
       CheckPrototypes(object, receiver, holder,
                       scratch1, scratch2, name, miss);
 
   // Push the arguments on the JS stack of the caller.
   __ pop(scratch2);  // remove return address
   __ push(receiver);  // receiver
-  __ push(Immediate(Handle<AccessorInfo>(callback)));  // callback data
+  __ push(reg);  // holder
+  __ mov(reg, Immediate(Handle<AccessorInfo>(callback)));  // callback data

[antonm, 2009/07/23 21:12:58]

why not __ push(Immediate....)?

[Vitaly Repeshko, 2009/07/24 13:45:38]

I need this data in a register anyway (to support the push below). Current
approach saves us a relocation entry.

+  __ push(reg);
+  __ push(FieldOperand(reg, AccessorInfo::kDataOffset));

[antonm, 2009/07/23 21:12:58]

ditto (shortcutting if data is not in new space)

[Vitaly Repeshko, 2009/07/24 13:45:38]

I tried it and my measurements didn't show any difference in performance. So I'd
prefer to keep this simple.

   __ push(name_reg);  // name
-  __ push(reg);  // holder
   __ push(scratch2);  // restore return address
 
   // Do tail-call to the runtime system.
   ExternalReference load_callback_property =
       ExternalReference(IC_Utility(IC::kLoadCallbackProperty));
-  __ TailCallRuntime(load_callback_property, 4);
+  __ TailCallRuntime(load_callback_property, 5);
 }
 
 
 void StubCompiler::GenerateLoadConstant(JSObject* object,
                                         JSObject* holder,
                                         Register receiver,
                                         Register scratch1,
                                         Register scratch2,
                                         Object* value,
                                         String* name,
@@ skipping 959 matching lines @@
   GenerateLoadMiss(masm(), Code::KEYED_LOAD_IC);
 
   // Return the generated code.
   return GetCode(CALLBACKS, name);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal