MIPS: Delegating yield does not re-box result objects.

src/mips/full-codegen-mips.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 2038 matching lines @@
       __ lw(a3, MemOperand(sp, 1 * kPointerSize));       // iter
       __ push(a3);                                       // iter
       __ push(a0);                                       // exception
       __ mov(a0, a3);                                    // iter
       __ LoadRoot(a2, Heap::kthrow_stringRootIndex);     // "throw"
       Handle<Code> throw_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(throw_ic);                                  // iter.throw in a0
       __ mov(a0, v0);
       __ jmp(&l_call);
 
-      // try { received = yield result.value }
+      // try { received = %yield result }
+      // Shuffle the received result above a try handler and yield it without
+      // re-boxing.
       __ bind(&l_try);
-      EmitCreateIteratorResult(false);                   // pop and box to v0
+      __ pop(a0);                                        // result
       __ PushTryHandler(StackHandler::CATCH, expr->index());
       const int handler_size = StackHandlerConstants::kSize;
       __ push(a0);                                       // result
       __ lw(a3, MemOperand(sp, (0 + 1) * kPointerSize + handler_size));  // g
       __ push(a3);                                       // g
       __ CallRuntime(Runtime::kSuspendJSGeneratorObject, 1);
       __ mov(a0, v0);
       __ lw(context_register(),
             MemOperand(fp, StandardFrameConstants::kContextOffset));
       __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
@@ skipping 24 matching lines @@
       __ mov(a1, a0);
       ParameterCount count(1);
       __ InvokeFunction(a1, count, CALL_FUNCTION,
                         NullCallWrapper(), CALL_AS_METHOD);
       __ lw(cp, MemOperand(fp, StandardFrameConstants::kContextOffset));
       __ jmp(&l_loop);
       __ bind(&l_call_runtime);
       __ push(a0);
       __ CallRuntime(Runtime::kCall, 3);
 
-      // val = result.value; if (!result.done) goto l_try;
+      // if (!result.done) goto l_try;
       __ bind(&l_loop);
       __ mov(a0, v0);
-      // result.value
       __ push(a0);                                       // save result
-      __ LoadRoot(a2, Heap::kvalue_stringRootIndex);     // "value"
-      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
-      CallIC(value_ic);                                  // result.value in a0
-      __ mov(a0, v0);
-      __ pop(a1);                                        // result
-      __ push(a0);                                       // result.value
-      __ mov(a0, a1);                                    // result
       __ LoadRoot(a2, Heap::kdone_stringRootIndex);      // "done"
       Handle<Code> done_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(done_ic);                                   // result.done in v0
       __ mov(a0, v0);
       Handle<Code> bool_ic = ToBooleanStub::GetUninitialized(isolate());
       CallIC(bool_ic);
       __ Branch(&l_try, eq, v0, Operand(zero_reg));
 
       // result.value
-      __ pop(v0);                                        // result.value
+      __ pop(a0);                                        // result
+      __ LoadRoot(a2, Heap::kvalue_stringRootIndex);     // "value"
+      Handle<Code> value_ic = isolate()->builtins()->LoadIC_Initialize();
+      CallIC(value_ic);                                  // result.value in r0

[Paul Lind, 2013/06/13 17:32:46]

nit: comment r0 -> v0

       context()->DropAndPlug(2, v0);                     // drop iter and g
       break;
     }
   }
 }
 
 
 void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
     Expression *value,
     JSGeneratorObject::ResumeMode resume_mode) {
@@ skipping 2811 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS