[turbofan] Context specialization is the job of the JSContextSpecialization.

src/compiler/js-context-specialization.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/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"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
-Reduction JSContextSpecializer::Reduce(Node* node) {
-  if (node->opcode() == IrOpcode::kJSLoadContext) {
-    return ReduceJSLoadContext(node);
-  }
-  if (node->opcode() == IrOpcode::kJSStoreContext) {
-    return ReduceJSStoreContext(node);
+Reduction JSContextSpecialization::Reduce(Node* node) {
+  switch (node->opcode()) {
+    case IrOpcode::kParameter:
+      return ReduceParameter(node);
+    case IrOpcode::kJSLoadContext:
+      return ReduceJSLoadContext(node);
+    case IrOpcode::kJSStoreContext:
+      return ReduceJSStoreContext(node);
+    default:
+      break;
   }
   return NoChange();
 }
 
 
-Reduction JSContextSpecializer::ReduceJSLoadContext(Node* node) {
+Reduction JSContextSpecialization::ReduceParameter(Node* node) {
+  DCHECK_EQ(IrOpcode::kParameter, node->opcode());
+  Node* const start = NodeProperties::GetValueInput(node, 0);
+  DCHECK_EQ(IrOpcode::kStart, start->opcode());
+  int const index = ParameterIndexOf(node->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) {
+    Handle<Context> context_constant;
+    if (context().ToHandle(&context_constant)) {
+      return Replace(jsgraph()->Constant(context_constant));
+    }
+  }
+  return NoChange();
+}
+
+
+Reduction JSContextSpecialization::ReduceJSLoadContext(Node* node) {
   DCHECK_EQ(IrOpcode::kJSLoadContext, node->opcode());
 
   HeapObjectMatcher 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());
 
@@ skipping 28 matching lines @@
 
   // 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 JSContextSpecializer::ReduceJSStoreContext(Node* node) {
+Reduction JSContextSpecialization::ReduceJSStoreContext(Node* node) {
   DCHECK_EQ(IrOpcode::kJSStoreContext, node->opcode());
 
   HeapObjectMatcher 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.
   Handle<Context> context = Handle<Context>::cast(m.Value().handle());
   for (size_t i = access.depth(); i > 0; --i) {
     context = handle(context->previous(), isolate());
   }
 
   node->set_op(javascript()->StoreContext(0, access.index()));
   node->ReplaceInput(0, jsgraph_->Constant(context));
   return Changed(node);
 }
 
 
-Isolate* JSContextSpecializer::isolate() const { return jsgraph()->isolate(); }
+Isolate* JSContextSpecialization::isolate() const {
+  return jsgraph()->isolate();
+}
 
 
-JSOperatorBuilder* JSContextSpecializer::javascript() const {
+JSOperatorBuilder* JSContextSpecialization::javascript() const {
   return jsgraph()->javascript();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8