| // 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(); |
| } |
| |
| Reduction JSContextSpecialization::SimplifyJSLoadContext(Node* node, |
| Node* new_context, |
| size_t new_depth) { |
| DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode()); |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| DCHECK_LE(new_depth, access.depth()); |
| |
| if (new_depth == access.depth() && |
| new_context == NodeProperties::GetContextInput(node)) { |
| return NoChange(); |
| } |
| |
| const Operator* op = jsgraph_->javascript()->LoadContext( |
| new_depth, access.index(), access.immutable()); |
| NodeProperties::ReplaceContextInput(node, new_context); |
| NodeProperties::ChangeOp(node, op); |
| return Changed(node); |
| } |
| |
| Reduction JSContextSpecialization::SimplifyJSStoreContext(Node* node, |
| Node* new_context, |
| size_t new_depth) { |
| DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode()); |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| DCHECK_LE(new_depth, access.depth()); |
| |
| if (new_depth == access.depth() && |
| new_context == NodeProperties::GetContextInput(node)) { |
| return NoChange(); |
| } |
| |
| const Operator* op = |
| jsgraph_->javascript()->StoreContext(new_depth, access.index()); |
| NodeProperties::ReplaceContextInput(node, new_context); |
| NodeProperties::ChangeOp(node, op); |
| return Changed(node); |
| } |
| |
| Reduction JSContextSpecialization::ReduceJSLoadContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode()); |
| |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| size_t depth = access.depth(); |
| |
| // First walk up the context chain in the graph as far as possible. |
| Node* outer = NodeProperties::GetOuterContext(node, &depth); |
| |
| Handle<Context> concrete; |
| if (!NodeProperties::GetSpecializationContext(outer, context()) |
| .ToHandle(&concrete)) { |
| // We do not have a concrete context object, so we can only partially reduce |
| // the load by folding-in the outer context node. |
| return SimplifyJSLoadContext(node, outer, depth); |
| } |
| |
| // Now walk up the concrete context chain for the remaining depth. |
| for (; depth > 0; --depth) { |
| concrete = handle(concrete->previous(), isolate()); |
| } |
| |
| if (!access.immutable()) { |
| // We found the requested context object but since the context slot is |
| // mutable we can only partially reduce the load. |
| return SimplifyJSLoadContext(node, jsgraph()->Constant(concrete), depth); |
| } |
| |
| // 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. Only if it is neither of these, can we be sure that |
| // it won't change anymore. |
| Handle<Object> value(concrete->get(static_cast<int>(access.index())), |
| isolate()); |
| if (value->IsUndefined(isolate()) || value->IsTheHole(isolate())) { |
| return SimplifyJSLoadContext(node, jsgraph()->Constant(concrete), depth); |
| } |
| |
| // 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); |
| ReplaceWithValue(node, constant); |
| return Replace(constant); |
| } |
| |
| |
| Reduction JSContextSpecialization::ReduceJSStoreContext(Node* node) { |
| DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode()); |
| |
| const ContextAccess& access = ContextAccessOf(node->op()); |
| size_t depth = access.depth(); |
| |
| // First walk up the context chain in the graph until we reduce the depth to 0 |
| // or hit a node that does not have a CreateXYZContext operator. |
| Node* outer = NodeProperties::GetOuterContext(node, &depth); |
| |
| Handle<Context> concrete; |
| if (!NodeProperties::GetSpecializationContext(outer, context()) |
| .ToHandle(&concrete)) { |
| // We do not have a concrete context object, so we can only partially reduce |
| // the load by folding-in the outer context node. |
| return SimplifyJSStoreContext(node, outer, depth); |
| } |
| |
| // Now walk up the concrete context chain for the remaining depth. |
| for (; depth > 0; --depth) { |
| concrete = handle(concrete->previous(), isolate()); |
| } |
| |
| return SimplifyJSStoreContext(node, jsgraph()->Constant(concrete), depth); |
| } |
| |
| |
| Isolate* JSContextSpecialization::isolate() const { |
| return jsgraph()->isolate(); |
| } |
| |
| |
| JSOperatorBuilder* JSContextSpecialization::javascript() const { |
| return jsgraph()->javascript(); |
| } |
| |
| } // namespace compiler |
| } // namespace internal |
| } // namespace v8 |