Implement [Generator].prototype.return.

src/full-codegen/x64/full-codegen-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 1853 matching lines @@
     case Yield::kSuspend:
       // Pop value from top-of-stack slot; box result into result register.
       EmitCreateIteratorResult(false);
       __ Push(result_register());
       // Fall through.
     case Yield::kInitial: {
       Label suspend, continuation, post_runtime, resume;
 
       __ jmp(&suspend);
       __ bind(&continuation);
+      // When we arrive here, the stack top is the resume mode and
+      // result_register() holds the input value (the argument given to the
+      // respective resume operation).
       __ RecordGeneratorContinuation();
-      __ jmp(&resume);
+      __ Pop(rbx);
+      __ SmiCompare(rbx, Smi::FromInt(JSGeneratorObject::RETURN));
+      __ j(not_equal, &resume);
+      __ Push(result_register());
+      EmitCreateIteratorResult(true);
+      EmitUnwindBeforeReturn();
+      EmitReturnSequence();
 
       __ bind(&suspend);
       VisitForAccumulatorValue(expr->generator_object());
       DCHECK(continuation.pos() > 0 && Smi::IsValid(continuation.pos()));
       __ Move(FieldOperand(rax, JSGeneratorObject::kContinuationOffset),
               Smi::FromInt(continuation.pos()));
       __ movp(FieldOperand(rax, JSGeneratorObject::kContextOffset), rsi);
       __ movp(rcx, rsi);
       __ RecordWriteField(rax, JSGeneratorObject::kContextOffset, rcx, rdx,
                           kDontSaveFPRegs);
@@ skipping 56 matching lines @@
       __ bind(&l_try);
       __ Pop(rax);                                       // result
       int handler_index = NewHandlerTableEntry();
       EnterTryBlock(handler_index, &l_catch);
       const int try_block_size = TryCatch::kElementCount * kPointerSize;
       __ Push(rax);                                      // result
 
       __ jmp(&l_suspend);
       __ bind(&l_continuation);
       __ RecordGeneratorContinuation();
-      __ jmp(&l_resume);
+      __ Pop(rbx);
+      __ SmiCompare(rbx, Smi::FromInt(JSGeneratorObject::RETURN));
+      __ j(not_equal, &l_resume);
+      __ Push(result_register());
+      EmitCreateIteratorResult(true);
+      EmitUnwindBeforeReturn();
+      EmitReturnSequence();

[Dan Ehrenberg, 2016/01/20 23:48:21]

Looks like you're supporting yield* here; what's the remaining issue?

 
       __ bind(&l_suspend);
       const int generator_object_depth = kPointerSize + try_block_size;
       __ movp(rax, Operand(rsp, generator_object_depth));
       __ Push(rax);                                      // g
       __ Push(Smi::FromInt(handler_index));              // handler-index
       DCHECK(l_continuation.pos() > 0 && Smi::IsValid(l_continuation.pos()));
       __ Move(FieldOperand(rax, JSGeneratorObject::kContinuationOffset),
               Smi::FromInt(l_continuation.pos()));
       __ movp(FieldOperand(rax, JSGeneratorObject::kContextOffset), rsi);
@@ skipping 54 matching lines @@
       __ Move(LoadDescriptor::SlotRegister(),
               SmiFromSlot(expr->ValueFeedbackSlot()));
       CallLoadIC(NOT_INSIDE_TYPEOF);                     // result.value in rax
       context()->DropAndPlug(2, rax);                    // drop iter and g
       break;
     }
   }
 }
 
 
-void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
-    Expression *value,
+void FullCodeGenerator::EmitGeneratorResume(
+    Expression* generator, Expression* value,
     JSGeneratorObject::ResumeMode resume_mode) {
   // The value stays in rax, and is ultimately read by the resumed generator, as
   // if CallRuntime(Runtime::kSuspendJSGeneratorObject) returned it. Or it
   // is read to throw the value when the resumed generator is already closed.
   // rbx will hold the generator object until the activation has been resumed.
   VisitForStackValue(generator);
   VisitForAccumulatorValue(value);
   __ Pop(rbx);
 
   // Load suspended function and context.
@@ skipping 37 matching lines @@
   if (resume_mode == JSGeneratorObject::NEXT) {
     Label slow_resume;
     __ cmpp(rdx, Immediate(0));
     __ j(not_zero, &slow_resume);
     __ movp(rdx, FieldOperand(rdi, JSFunction::kCodeEntryOffset));
     __ SmiToInteger64(rcx,
         FieldOperand(rbx, JSGeneratorObject::kContinuationOffset));
     __ addp(rdx, rcx);
     __ Move(FieldOperand(rbx, JSGeneratorObject::kContinuationOffset),
             Smi::FromInt(JSGeneratorObject::kGeneratorExecuting));
+    __ Push(Smi::FromInt(resume_mode));  // Consumed in continuation.

[Benedikt Meurer, 2016/01/21 05:09:02]

I'd vote for dedicated continuations instead of this push magic.

     __ jmp(rdx);
     __ 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);
   __ subp(rdx, Immediate(1));
   __ j(carry, &call_resume);
   __ Push(rcx);
   __ jmp(&push_operand_holes);
   __ bind(&call_resume);
+  __ Push(Smi::FromInt(resume_mode));  // Consumed in continuation.
   __ Push(rbx);
   __ Push(result_register());
   __ Push(Smi::FromInt(resume_mode));
   __ CallRuntime(Runtime::kResumeJSGeneratorObject);
   // Not reached: the runtime call returns elsewhere.
   __ Abort(kGeneratorFailedToResume);
 
   __ bind(&done);
   context()->Plug(result_register());
 }
@@ skipping 2642 matching lines @@
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64