Make FastNewFunctionContextStub take slots parameter

src/compiler/js-generic-lowering.cc

 // Copyright 2014 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.
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 409 matching lines @@
   }
 }
 
 
 void JSGenericLowering::LowerJSCreateFunctionContext(Node* node) {
   int const slot_count = OpParameter<int>(node->op());
   CallDescriptor::Flags flags = AdjustFrameStatesForCall(node);
 
   // Use the FastNewFunctionContextStub only for function contexts up maximum
   // size.
   if (slot_count <= FastNewFunctionContextStub::kMaximumSlots) {

[klaasb, 2016/07/29 09:51:36]

What about this and similar lines elsewhere? I would remove them and the
alternate branches (calls to the runtime). See discussion in earlier patches.

-    Callable callable = CodeFactory::FastNewContext(isolate(), slot_count);
+    Callable callable = CodeFactory::FastNewContext(isolate());
+    node->InsertInput(zone(), 1, jsgraph()->Int32Constant(slot_count));

[Benedikt Meurer, 2016/07/29 03:29:16]

I'm not sure this is correct according to the interface descriptor (same for the
FCG versions). The interface descriptor declares the slots parameter as tagged,
but you are passing it as untagged signed32 value (and also use it that way in
the stub). I think for this to work you have to change the interface descriptor
to declare the parameter as signed32.

[klaasb, 2016/07/29 09:51:36]

Done.

     ReplaceWithStubCall(node, callable, flags);
   } else {
     ReplaceWithRuntimeCall(node, Runtime::kNewFunctionContext);
   }
 }
 
 
 void JSGenericLowering::LowerJSCreateIterResultObject(Node* node) {
   ReplaceWithRuntimeCall(node, Runtime::kCreateIterResultObject);
 }
@@ skipping 229 matching lines @@
 }
 
 
 MachineOperatorBuilder* JSGenericLowering::machine() const {
   return jsgraph()->machine();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8