X87: [generators] Implement Generator.prototype.return.

  port dbd86408 (r33744)

  original commit message:
  Note: This is currently only used by yield*, we still need to support it in
  other places (such as for-of loops).  It can be used manually of course.

  (This CL does not touch the full-codegen implementation of yield* because that
  code is already dead.  The yield* desugaring already supports return and doesn't
  need to be touched.)

BUG=

Review URL: https://codereview.chromium.org/1671783002

Cr-Commit-Position: refs/heads/master@{#33760}

src/full-codegen/x87/full-codegen-x87.cc

@@ -1839,8 +1839,17 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
 
       __ 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(ebx);
+      __ cmp(ebx, Immediate(Smi::FromInt(JSGeneratorObject::RETURN)));
+      __ j(not_equal, &resume);
+      __ push(result_register());
+      EmitCreateIteratorResult(true);
+      EmitUnwindBeforeReturn();
+      EmitReturnSequence();
 
       __ bind(&suspend);
       VisitForAccumulatorValue(expr->generator_object());
@@ -2001,8 +2010,8 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
 
   // Store input value into generator object.
   __ mov(FieldOperand(ebx, JSGeneratorObject::kInputOffset), result_register());
-  __ mov(edx, result_register());
-  __ RecordWriteField(ebx, JSGeneratorObject::kInputOffset, edx, ecx,
+  __ mov(ecx, result_register());
+  __ RecordWriteField(ebx, JSGeneratorObject::kInputOffset, ecx, edx,
                       kDontSaveFPRegs);
 
   // Load suspended function and context.
@@ -2053,6 +2062,7 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
     __ add(edx, ecx);
     __ mov(FieldOperand(ebx, JSGeneratorObject::kContinuationOffset),
            Immediate(Smi::FromInt(JSGeneratorObject::kGeneratorExecuting)));
+    __ Push(Smi::FromInt(resume_mode));  // Consumed in continuation.
     __ jmp(edx);
     __ bind(&slow_resume);
   }
@@ -2066,6 +2076,7 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
   __ push(ecx);
   __ jmp(&push_operand_holes);
   __ bind(&call_resume);
+  __ Push(Smi::FromInt(resume_mode));  // Consumed in continuation.
   __ push(ebx);
   __ push(result_register());
   __ Push(Smi::FromInt(resume_mode));