Generators can resume

src/ia32/full-codegen-ia32.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 1919 matching lines @@
       EmitReturnSequence();
       break;
     }
 
     case Yield::DELEGATING:
       UNIMPLEMENTED();
   }
 }
 
 
+void FullCodeGenerator::EmitResume(Expression *generator_expr,
+                                   Expression *value_expr,
+                                   JSGeneratorObject::ResumeMode resume_mode) {
+  // ebx will hold the generator object until the activation has been resumed.
+  VisitForAccumulatorValue(generator_expr);
+  __ mov(ebx, result_register());

[Michael Starzinger, 2013/04/21 22:45:21]

The ebx register might get clobbered while evaluating the value expression of
the resume below. This will be hard to find if someone changes the usage of
%_GeneratorSend in the runtime code. Use the stack to preserve generator object.

[wingo, 2013/04/23 13:51:04]

Good catch!  Fixed.

+
+  // The value stays in eax, and is ultimately read by the resumed generator, as
+  // if the CallRuntime(Runtime::kSuspendJSGeneratorObject) returned it.
+  VisitForAccumulatorValue(value_expr);
+
+  // Check generator state.
+  Label wrong_state, done;
+  __ mov(edx, FieldOperand(ebx, JSGeneratorObject::kContinuationOffset));
+  __ SmiUntag(edx);

[Michael Starzinger, 2013/04/21 22:45:21]

No need to untag and compare, we can compare right against a Smi. Also we should
be able to use the FieldOperand directly in the compare, just one instruction.

[wingo, 2013/04/23 13:51:04]

Done.

+  __ cmp(edx, Immediate(0));
+  __ j(less_equal, &wrong_state);
+
+  // Load suspended function and context.
+  __ mov(esi, FieldOperand(ebx, JSGeneratorObject::kContextOffset));
+  __ mov(edi, FieldOperand(ebx, JSGeneratorObject::kFunctionOffset));
+
+  // Push holes for arguments to generator function.
+  __ mov(edx, FieldOperand(edi, JSFunction::kSharedFunctionInfoOffset));
+  __ mov(edx,
+         FieldOperand(edx, SharedFunctionInfo::kFormalParameterCountOffset));
+  __ mov(ecx, isolate()->factory()->the_hole_value());
+  Label push_argument_holes;
+  __ bind(&push_argument_holes);
+  __ push(ecx);
+  __ sub(edx, Immediate(1));
+  __ j(not_carry, &push_argument_holes);
+
+  // Enter a new JavaScript frame, and initialize its slots as they were when
+  // the generator was suspended.
+  Label push_frame, resume_frame;
+  __ bind(&push_frame);
+  __ call(&resume_frame);
+  __ jmp(&done);
+  __ bind(&resume_frame);
+  __ push(ebp);  // Caller's frame pointer.
+  __ mov(ebp, esp);
+  __ push(esi);  // Callee's context.
+  __ push(edi);  // Callee's JS Function.
+
+  // Load the operand stack size.
+  __ mov(edx, FieldOperand(ebx, JSGeneratorObject::kOperandStackOffset));
+  __ mov(edx, FieldOperand(edx, FixedArray::kLengthOffset));
+  __ SmiUntag(edx);
+
+  // If we are sending a value and there is no operand stack, we can jump back
+  // in directly.
+  if (resume_mode == JSGeneratorObject::kSend) {
+    Label slow_resume;
+    __ cmp(edx, Immediate(0));
+    __ j(not_zero, &slow_resume);
+    __ mov(edx, FieldOperand(edi, JSFunction::kCodeEntryOffset));
+    __ mov(ecx, FieldOperand(ebx, JSGeneratorObject::kContinuationOffset));
+    __ SmiUntag(ecx);
+    __ add(edx, ecx);
+    __ mov(FieldOperand(ebx, JSGeneratorObject::kContinuationOffset),
+           Immediate(Smi::FromInt(JSGeneratorObject::kGeneratorExecuting)));
+    __ jmp(edx);
+    __ bind(&slow_resume);
+  }
+
+  // Otherwise, we push holes for the operand stack and call the runtime to fix
+  // up the stack and the handlers.
+  Label push_operand_holes, call_resume;
+  __ bind(&push_operand_holes);
+  __ sub(edx, Immediate(1));
+  __ j(carry, &call_resume);
+  __ push(ecx);
+  __ jmp(&push_operand_holes);
+  __ bind(&call_resume);
+  __ push(ebx);
+  __ push(result_register());
+  __ Push(Smi::FromInt(resume_mode));
+  __ CallRuntime(Runtime::kResumeJSGeneratorObject, 3);
+  // Not reached: the runtime call returns elsewhere.
+  __ int3();
+
+  // Throw error if we attempt to operate on a running generator.
+  __ bind(&wrong_state);
+  __ push(ebx);
+  __ CallRuntime(Runtime::kThrowGeneratorStateError, 1);
+
+  __ bind(&done);
+  context()->Plug(result_register());
+}
+
+
 void FullCodeGenerator::EmitNamedPropertyLoad(Property* prop) {
   SetSourcePosition(prop->position());
   Literal* key = prop->key()->AsLiteral();
   ASSERT(!key->handle()->IsSmi());
   __ mov(ecx, Immediate(key->handle()));
   Handle<Code> ic = isolate()->builtins()->LoadIC_Initialize();
   CallIC(ic, RelocInfo::CODE_TARGET, prop->PropertyFeedbackId());
 }
 
 
@@ skipping 2650 matching lines @@
   *stack_depth = 0;
   *context_length = 0;
   return previous_;
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32