[turbofan] Simply context specialization and fix for OSR.

src/compiler/ast-graph-builder.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/ast-graph-builder.h"
 
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/linkage.h"
@@ skipping 361 matching lines @@
 AstGraphBuilder::AstGraphBuilder(Zone* local_zone, CompilationInfo* info,
                                  JSGraph* jsgraph, LoopAssignmentAnalysis* loop)
     : local_zone_(local_zone),
       info_(info),
       jsgraph_(jsgraph),
       environment_(nullptr),
       ast_context_(nullptr),
       globals_(0, local_zone),
       execution_control_(nullptr),
       execution_context_(nullptr),
-      function_context_(nullptr),
       input_buffer_size_(0),
       input_buffer_(nullptr),
       exit_control_(nullptr),
       loop_assignment_analysis_(loop) {
   InitializeAstVisitor(info->isolate(), local_zone);
 }
 
 
 Node* AstGraphBuilder::GetFunctionClosure() {
   if (!function_closure_.is_set()) {
     const Operator* op =
         common()->Parameter(Linkage::kJSFunctionCallClosureParamIndex);
     Node* node = NewNode(op, graph()->start());
     function_closure_.set(node);
   }
   return function_closure_.get();
 }
 
 
-Node* AstGraphBuilder::GetFunctionContext() {
-  DCHECK(function_context_ != nullptr);
-  return function_context_;
-}
+Node* AstGraphBuilder::GetFunctionContext() { return function_context_.get(); }
 
 
 Node* AstGraphBuilder::NewOuterContextParam() {
   // Parameter (arity + 1) is special for the outer context of the function
   const Operator* op = common()->Parameter(info()->num_parameters() + 1);
   return NewNode(op, graph()->start());
 }
 
 
 Node* AstGraphBuilder::NewCurrentContextOsrValue() {
   // TODO(titzer): use a real OSR value here; a parameter works by accident.
   // Parameter (arity + 1) is special for the outer context of the function
   const Operator* op = common()->Parameter(info()->num_parameters() + 1);
   return NewNode(op, graph()->start());
 }
 
 
-bool AstGraphBuilder::CreateGraph() {
+bool AstGraphBuilder::CreateGraph(bool constant_context) {
   Scope* scope = info()->scope();
   DCHECK(graph() != NULL);
 
   // Set up the basic structure of the graph.
   int parameter_count = info()->num_parameters();
   graph()->SetStart(graph()->NewNode(common()->Start(parameter_count)));
 
   // Initialize control scope.
   ControlScope control(this, 0);
 
   // Initialize the top-level environment.
   Environment env(this, scope, graph()->start());
   set_environment(&env);
 
   if (info()->is_osr()) {
     // Use OSR normal entry as the start of the top-level environment.
     // It will be replaced with {Dead} after typing and optimizations.
     NewNode(common()->OsrNormalEntry());
   }
 
   // Initialize the incoming context.
-  function_context_ = NewOuterContextParam();
-  ContextScope incoming(this, scope, function_context_);
+  if (constant_context) {

[Michael Starzinger, 2015/02/18 17:37:32]

nit: Can we move this logic into GetFunctionContext, pass in the boolean and
just call it from here?

[titzer, 2015/02/19 09:53:04]

As discussed in person, I've moved this into CreateFunctionContext and inlined
the function_context_.get() at usage sites.

+    function_context_.set(jsgraph()->HeapConstant(info()->context()));
+  } else {
+    function_context_.set(NewOuterContextParam());
+  }
+  ContextScope incoming(this, scope, function_context_.get());
 
   // Build receiver check for sloppy mode if necessary.
   // TODO(mstarzinger/verwaest): Should this be moved back into the CallIC?
   Node* original_receiver = env.Lookup(scope->receiver());
   Node* patched_receiver = BuildPatchReceiverToGlobalProxy(original_receiver);
   env.Bind(scope->receiver(), patched_receiver);
 
   bool ok;
   int heap_slots = info()->num_heap_slots() - Context::MIN_CONTEXT_SLOTS;
   if (heap_slots > 0) {
     // Push a new inner context scope for the function.
     Node* closure = GetFunctionClosure();
-    Node* inner_context = BuildLocalFunctionContext(function_context_, closure);
+    Node* inner_context =
+        BuildLocalFunctionContext(function_context_.get(), closure);
     ContextScope top_context(this, scope, inner_context);
     ok = CreateGraphBody();
   } else {
     // Simply use the outer function context in building the graph.
     ok = CreateGraphBody();
   }
 
   // Finish the basic structure of the graph.
   if (ok) {
     environment()->UpdateControlDependency(exit_control());
@@ skipping 2564 matching lines @@
 
   // Resurrect a dead environment by copying the contents of the other one and
   // placing a singleton merge as the new control dependency.
   if (this->IsMarkedAsUnreachable()) {
     Node* other_control = other->control_dependency_;
     Node* inputs[] = {other_control};
     control_dependency_ =
         graph()->NewNode(common()->Merge(1), arraysize(inputs), inputs, true);
     effect_dependency_ = other->effect_dependency_;
     values_ = other->values_;
+    contexts_ = other->contexts_;
     return;
   }
 
   // Create a merge of the control dependencies of both environments and update
   // the current environment's control dependency accordingly.
   Node* control = builder_->MergeControl(this->GetControlDependency(),
                                          other->GetControlDependency());
   UpdateControlDependency(control);
 
   // Create a merge of the effect dependencies of both environments and update
@@ skipping 153 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8