Allocate generator result objects before unwinding try handlers

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 1934 matching lines @@
 
 void FullCodeGenerator::VisitYield(Yield* expr) {
   Comment cmnt(masm_, "[ Yield");
   // Evaluate yielded value first; the initial iterator definition depends on
   // this.  It stays on the stack while we update the iterator.
   VisitForStackValue(expr->expression());
 
   switch (expr->yield_kind()) {
     case Yield::INITIAL:
     case Yield::SUSPEND: {
+      if (expr->yield_kind() == Yield::SUSPEND) {

[Michael Starzinger, 2013/06/12 10:47:56]

This can be modeled by flipping the two cases above, moving the additional steps
for Yield::SUSPEND up and letting it fall-through to Yield::INITIAL. I think
that would be easier to read. Same applies to other architectures.

+        // Pop value from top-of-stack slot, box result into result register.
+        EmitCreateIteratorResult(false);
+        __ push(result_register());
+      }
       VisitForStackValue(expr->generator_object());
       __ CallRuntime(Runtime::kSuspendJSGeneratorObject, 1);
       __ mov(context_register(),
              Operand(ebp, StandardFrameConstants::kContextOffset));
 
       Label resume;
       __ CompareRoot(result_register(), Heap::kTheHoleValueRootIndex);
       __ j(not_equal, &resume);
-      if (expr->yield_kind() == Yield::SUSPEND) {
-        EmitReturnIteratorResult(false);
-      } else {
-        __ pop(result_register());
-        EmitReturnSequence();
-      }
+      __ pop(result_register());
+      EmitReturnSequence();
 
       __ bind(&resume);
       context()->Plug(result_register());
       break;
     }
 
     case Yield::FINAL: {
       VisitForAccumulatorValue(expr->generator_object());
       __ mov(FieldOperand(result_register(),
                           JSGeneratorObject::kContinuationOffset),
              Immediate(Smi::FromInt(JSGeneratorObject::kGeneratorClosed)));
-      EmitReturnIteratorResult(true);
+      // Pop value from top-of-stack slot, box result into result register.
+      EmitCreateIteratorResult(true);
+      EmitUnwindBeforeReturn();
+      EmitReturnSequence();
       break;
     }
 
     case Yield::DELEGATING: {
       VisitForStackValue(expr->generator_object());
 
       // Initial stack layout is as follows:
       // [sp + 1 * kPointerSize] iter
       // [sp + 0 * kPointerSize] g
 
       Label l_catch, l_try, l_resume, l_next, l_call, l_loop;
       // Initial send value is undefined.
       __ mov(eax, isolate()->factory()->undefined_value());
       __ jmp(&l_next);
 
       // catch (e) { receiver = iter; f = iter.throw; arg = e; goto l_call; }
       __ bind(&l_catch);
       handler_table()->set(expr->index(), Smi::FromInt(l_catch.pos()));
       __ mov(edx, Operand(esp, 1 * kPointerSize));       // iter
       __ push(edx);                                      // iter
       __ push(eax);                                      // exception
       __ mov(ecx, isolate()->factory()->throw_string());  // "throw"
       Handle<Code> throw_ic = isolate()->builtins()->LoadIC_Initialize();
       CallIC(throw_ic);                                  // iter.throw in eax
       __ jmp(&l_call);
 
       // try { received = yield result.value }
       __ bind(&l_try);
-      __ pop(eax);                                       // result.value
+      EmitCreateIteratorResult(false);                    // pop and box to eax
       __ PushTryHandler(StackHandler::CATCH, expr->index());
       const int handler_size = StackHandlerConstants::kSize;
-      __ push(eax);                                      // result.value
+      __ push(eax);                                      // result
       __ push(Operand(esp, (0 + 1) * kPointerSize + handler_size));  // g
       __ CallRuntime(Runtime::kSuspendJSGeneratorObject, 1);
       __ mov(context_register(),
              Operand(ebp, StandardFrameConstants::kContextOffset));
       __ CompareRoot(eax, Heap::kTheHoleValueRootIndex);
       __ j(not_equal, &l_resume);
-      EmitReturnIteratorResult(false);
+      __ pop(eax);                                       // result
+      EmitReturnSequence();
       __ bind(&l_resume);                                // received in eax
       __ PopTryHandler();
 
       // receiver = iter; f = iter.next; arg = received;
       __ bind(&l_next);
       __ mov(edx, Operand(esp, 1 * kPointerSize));       // iter
       __ push(edx);                                      // iter
       __ push(eax);                                      // received
       __ mov(ecx, isolate()->factory()->next_string());  // "next"
       Handle<Code> next_ic = isolate()->builtins()->LoadIC_Initialize();
@@ skipping 132 matching lines @@
   // 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::EmitReturnIteratorResult(bool done) {
+void FullCodeGenerator::EmitCreateIteratorResult(bool done) {
   Label gc_required;
   Label allocated;
 
   Handle<Map> map(isolate()->native_context()->generator_result_map());
 
   __ Allocate(map->instance_size(), eax, ecx, edx, &gc_required, TAG_OBJECT);
+  __ jmp(&allocated);
+
+  __ bind(&gc_required);
+  __ Push(Smi::FromInt(map->instance_size()));
+  __ CallRuntime(Runtime::kAllocateInNewSpace, 1);
+  __ mov(context_register(),
+         Operand(ebp, StandardFrameConstants::kContextOffset));
 
   __ bind(&allocated);
   __ mov(ebx, map);
   __ pop(ecx);
   __ mov(edx, isolate()->factory()->ToBoolean(done));
   ASSERT_EQ(map->instance_size(), 5 * kPointerSize);
   __ mov(FieldOperand(eax, HeapObject::kMapOffset), ebx);
   __ mov(FieldOperand(eax, JSObject::kPropertiesOffset),
          isolate()->factory()->empty_fixed_array());
   __ mov(FieldOperand(eax, JSObject::kElementsOffset),
          isolate()->factory()->empty_fixed_array());
   __ mov(FieldOperand(eax, JSGeneratorObject::kResultValuePropertyOffset), ecx);
   __ mov(FieldOperand(eax, JSGeneratorObject::kResultDonePropertyOffset), edx);
 
   // Only the value field needs a write barrier, as the other values are in the
   // root set.
   __ RecordWriteField(eax, JSGeneratorObject::kResultValuePropertyOffset,
                       ecx, edx, kDontSaveFPRegs);
-
-  if (done) {
-    // Exit all nested statements.
-    NestedStatement* current = nesting_stack_;
-    int stack_depth = 0;
-    int context_length = 0;
-    while (current != NULL) {
-      current = current->Exit(&stack_depth, &context_length);
-    }
-    __ Drop(stack_depth);
-  }
-
-  EmitReturnSequence();
-
-  __ bind(&gc_required);
-  __ Push(Smi::FromInt(map->instance_size()));
-  __ CallRuntime(Runtime::kAllocateInNewSpace, 1);
-  __ mov(context_register(),
-         Operand(ebp, StandardFrameConstants::kContextOffset));
-  __ jmp(&allocated);
 }
 
 
 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 2695 matching lines @@
   *stack_depth = 0;
   *context_length = 0;
   return previous_;
 }
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32