| // 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/compiler/js-context-specialization.h" |
| |
| #include "src/compiler/common-operator.h" |
| #include "src/compiler/js-graph.h" |
| #include "src/compiler/js-operator.h" |
| #include "src/compiler/node-matchers.h" |
| #include "src/compiler/node-properties.h" |
| #include "src/contexts.h" |
| #include "src/objects-inl.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| Reduction JSContextSpecialization::Reduce(Node* node) { |
| switch (node->opcode()) { |
| case IrOpcode::kJSLoadContext: |
| return ReduceJSLoadContext(node); |
| case IrOpcode::kJSStoreContext: |
| return ReduceJSStoreContext(node); |
| default: |
| break; |
| } |
| return NoChange(); |
| } |
| |
| |
| MaybeHandle<Context> JSContextSpecialization::GetSpecializationContext( |
| Node* node) { |
| DCHECK(node->opcode() == IrOpcode::kJSLoadContext || |
| node->opcode() == IrOpcode::kJSStoreContext); |
| Node* const object = NodeProperties::GetValueInput(node, 0); |
| switch (object->opcode()) { |
| case IrOpcode::kHeapConstant: |
| return Handle<Context>::cast(OpParameter<Handle<HeapObject>>(object)); |
| case IrOpcode::kParameter: { |
| Node* const start = NodeProperties::GetValueInput(object, 0); |
| DCHECK_EQ(IrOpcode::kStart, start->opcode()); |
| int const index = ParameterIndexOf(object->op()); |
| // The context is always the last parameter to a JavaScript function, and |
| // {Parameter} indices start at -1, so value outputs of {Start} look like |
| // this: closure, receiver, param0, ..., paramN, context. |
| if (index == start->op()->ValueOutputCount() - 2) { |
| return context(); |
| } |
| break; |
| } |
| default: |
| break; |
| } |
| return MaybeHandle<Context>(); |
| } |
| |
| |
| Reduction JSContextSpecialization::ReduceJSLoadContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode()); |
| |
| // Get the specialization context from the node. |
| Handle<Context> context; |
| if (!GetSpecializationContext(node).ToHandle(&context)) return NoChange(); |
| |
| // Find the right parent context. |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| for (size_t i = access.depth(); i > 0; --i) { |
| context = handle(context->previous(), isolate()); |
| } |
| |
| // If the access itself is mutable, only fold-in the parent. |
| if (!access.immutable()) { |
| // The access does not have to look up a parent, nothing to fold. |
| if (access.depth() == 0) { |
| return NoChange(); |
| } |
| const Operator* op = jsgraph_->javascript()->LoadContext( |
| 0, access.index(), access.immutable()); |
| node->ReplaceInput(0, jsgraph_->Constant(context)); |
| NodeProperties::ChangeOp(node, op); |
| return Changed(node); |
| } |
| Handle<Object> value = |
| handle(context->get(static_cast<int>(access.index())), isolate()); |
| |
| // Even though the context slot is immutable, the context might have escaped |
| // before the function to which it belongs has initialized the slot. |
| // We must be conservative and check if the value in the slot is currently the |
| // hole or undefined. If it is neither of these, then it must be initialized. |
| if (value->IsUndefined() || value->IsTheHole()) { |
| return NoChange(); |
| } |
| |
| // Success. The context load can be replaced with the constant. |
| // TODO(titzer): record the specialization for sharing code across multiple |
| // contexts that have the same value in the corresponding context slot. |
| if (value->IsConsString()) { |
| value = String::Flatten(Handle<String>::cast(value), TENURED); |
| } |
| Node* constant = jsgraph_->Constant(value); |
| ReplaceWithValue(node, constant); |
| return Replace(constant); |
| } |
| |
| |
| Reduction JSContextSpecialization::ReduceJSStoreContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode()); |
| |
| // Get the specialization context from the node. |
| Handle<Context> context; |
| if (!GetSpecializationContext(node).ToHandle(&context)) return NoChange(); |
| |
| // The access does not have to look up a parent, nothing to fold. |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| if (access.depth() == 0) { |
| return NoChange(); |
| } |
| |
| // Find the right parent context. |
| for (size_t i = access.depth(); i > 0; --i) { |
| context = handle(context->previous(), isolate()); |
| } |
| |
| node->ReplaceInput(0, jsgraph_->Constant(context)); |
| NodeProperties::ChangeOp(node, javascript()->StoreContext(0, access.index())); |
| return Changed(node); |
| } |
| |
| |
| Isolate* JSContextSpecialization::isolate() const { |
| return jsgraph()->isolate(); |
| } |
| |
| |
| JSOperatorBuilder* JSContextSpecialization::javascript() const { |
| return jsgraph()->javascript(); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |