| // 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.h" |
| #include "src/compiler/common-operator.h" |
| #include "src/compiler/graph-inl.h" |
| #include "src/compiler/js-operator.h" |
| #include "src/compiler/node-matchers.h" |
| #include "src/compiler/node-properties-inl.h" |
| |
| namespace v8 { |
| namespace internal { |
| namespace compiler { |
| |
| Reduction JSContextSpecializer::Reduce(Node* node) { |
| if (node == context_) { |
| Node* constant = jsgraph_->Constant(info_->context()); |
| NodeProperties::ReplaceWithValue(node, constant); |
| return Replace(constant); |
| } |
| if (node->opcode() == IrOpcode::kJSLoadContext) { |
| return ReduceJSLoadContext(node); |
| } |
| if (node->opcode() == IrOpcode::kJSStoreContext) { |
| return ReduceJSStoreContext(node); |
| } |
| return NoChange(); |
| } |
| |
| |
| Reduction JSContextSpecializer::ReduceJSLoadContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode()); |
| |
| HeapObjectMatcher<Context> m(NodeProperties::GetValueInput(node, 0)); |
| // If the context is not constant, no reduction can occur. |
| if (!m.HasValue()) { |
| return NoChange(); |
| } |
| |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| |
| // Find the right parent context. |
| Context* context = *m.Value().handle(); |
| for (size_t i = access.depth(); i > 0; --i) { |
| context = context->previous(); |
| } |
| |
| // 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->set_op(op); |
| Handle<Object> context_handle = Handle<Object>(context, info_->isolate()); |
| node->ReplaceInput(0, jsgraph_->Constant(context_handle)); |
| return Changed(node); |
| } |
| Handle<Object> value = Handle<Object>( |
| context->get(static_cast<int>(access.index())), info_->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. |
| Node* constant = jsgraph_->Constant(value); |
| NodeProperties::ReplaceWithValue(node, constant); |
| return Replace(constant); |
| } |
| |
| |
| Reduction JSContextSpecializer::ReduceJSStoreContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode()); |
| |
| HeapObjectMatcher<Context> m(NodeProperties::GetValueInput(node, 0)); |
| // If the context is not constant, no reduction can occur. |
| if (!m.HasValue()) { |
| return NoChange(); |
| } |
| |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| |
| // The access does not have to look up a parent, nothing to fold. |
| if (access.depth() == 0) { |
| return NoChange(); |
| } |
| |
| // Find the right parent context. |
| Context* context = *m.Value().handle(); |
| for (size_t i = access.depth(); i > 0; --i) { |
| context = context->previous(); |
| } |
| |
| const Operator* op = jsgraph_->javascript()->StoreContext(0, access.index()); |
| node->set_op(op); |
| Handle<Object> new_context_handle = Handle<Object>(context, info_->isolate()); |
| node->ReplaceInput(0, jsgraph_->Constant(new_context_handle)); |
| |
| return Changed(node); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |