Allocate generator result objects before unwinding try handlers

src/ia32/full-codegen-ia32.cc

Index: src/ia32/full-codegen-ia32.cc
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index c77faaad80e06a31c8e10b326bcbeff1465e9fbb..0763620b6d4e0e0b52d9737bdee61160fae310f5 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -1952,6 +1952,11 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
   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(),
@@ -1960,12 +1965,8 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       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());
@@ -1977,7 +1978,10 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
       __ 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;
     }
 
@@ -2006,17 +2010,18 @@ void FullCodeGenerator::VisitYield(Yield* expr) {
 
       // 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();
 
@@ -2169,13 +2174,20 @@ void FullCodeGenerator::EmitGeneratorResume(Expression *generator,
 }
 
 
-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);
@@ -2194,26 +2206,6 @@ void FullCodeGenerator::EmitReturnIteratorResult(bool done) {
   // 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);
 }