[turbofan] Move context specialization into JSContextSpecializer.

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/js-type-feedback.h"
@@ skipping 465 matching lines @@
   if (!function_closure_.is_set()) {
     const Operator* op = common()->Parameter(
         Linkage::kJSFunctionCallClosureParamIndex, "%closure");
     Node* node = NewNode(op, graph()->start());
     function_closure_.set(node);
   }
   return function_closure_.get();
 }
 
 
-void AstGraphBuilder::CreateFunctionContext(bool constant_context) {
-  function_context_.set(constant_context
-                            ? jsgraph()->HeapConstant(info()->context())
-                            : NewOuterContextParam());
+Node* AstGraphBuilder::GetFunctionContext() {
+  if (!function_context_.is_set()) {
+    const Operator* op = common()->Parameter(
+        info()->num_parameters_including_this(), "%context");
+    Node* node = NewNode(op, graph()->start());
+    function_context_.set(node);
+  }
+  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_including_this(), "%context");
-  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_including_this(), "%osr-context");
-  return NewNode(op, graph()->start());
-}
-
-
-bool AstGraphBuilder::CreateGraph(bool constant_context, bool stack_check) {
+bool AstGraphBuilder::CreateGraph(bool stack_check) {
   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 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.
-  CreateFunctionContext(constant_context);
-  ContextScope incoming(this, scope, function_context_.get());
+  ContextScope incoming(this, scope, GetFunctionContext());
 
   // Initialize control scope.
   ControlScope control(this);
 
   // Build receiver check for sloppy mode if necessary.
   // TODO(mstarzinger/verwaest): Should this be moved back into the CallIC?
   Node* patched_receiver = nullptr;
   if (scope->has_this_declaration()) {
     Node* original_receiver = NewNode(common()->Parameter(0), graph()->start());
     patched_receiver = BuildPatchReceiverToGlobalProxy(original_receiver);
     if (scope->receiver()->IsStackAllocated()) {
       env.Bind(scope->receiver(), patched_receiver);
     }
   }
 
   // Build function context only if there are context allocated variables.
   if (info()->num_heap_slots() > 0) {
     // Push a new inner context scope for the function.
     Node* inner_context =
-        BuildLocalFunctionContext(function_context_.get(), patched_receiver);
+        BuildLocalFunctionContext(GetFunctionContext(), patched_receiver);
     ContextScope top_context(this, scope, inner_context);
     CreateGraphBody(stack_check);
   } else {
     // Simply use the outer function context in building the graph.
     CreateGraphBody(stack_check);
   }
 
   // Finish the basic structure of the graph.
   DCHECK_NE(0u, exit_controls_.size());
   int const input_count = static_cast<int>(exit_controls_.size());
@@ skipping 3068 matching lines @@
   Node* global = BuildLoadGlobalObject();
   Node* builtins =
       BuildLoadObjectField(global, JSGlobalObject::kBuiltinsOffset);
   return builtins;
 }
 
 
 Node* AstGraphBuilder::BuildLoadGlobalObject() {
   const Operator* load_op =
       javascript()->LoadContext(0, Context::GLOBAL_OBJECT_INDEX, true);
-  return NewNode(load_op, function_context_.get());
+  return NewNode(load_op, GetFunctionContext());
 }
 
 
 Node* AstGraphBuilder::BuildLoadGlobalProxy() {
   Node* global = BuildLoadGlobalObject();
   Node* proxy =
       BuildLoadObjectField(global, JSGlobalObject::kGlobalProxyOffset);
   return proxy;
 }
 
@@ skipping 406 matching lines @@
     // Connect the Loop node to end via a Terminate node.
     Node* terminate = builder_->graph()->NewNode(
         builder_->common()->Terminate(), effect, control);
     builder_->exit_controls_.push_back(terminate);
   }
 
   if (builder_->info()->is_osr()) {
     // Introduce phis for all context values in the case of an OSR graph.
     for (int i = 0; i < static_cast<int>(contexts()->size()); ++i) {
       Node* val = contexts()->at(i);
-      if (!IrOpcode::IsConstantOpcode(val->opcode())) {
+      if (!IrOpcode::IsConstantOpcode(val->opcode()) &&
+          (val != builder_->GetFunctionContext() ||
+           !builder_->info()->is_context_specializing())) {
         contexts()->at(i) = builder_->NewPhi(1, val, control);
       }
     }
   }
 
   if (is_osr) {
     // Merge OSR values as inputs to the phis of the loop.
     Graph* graph = builder_->graph();
     Node* osr_loop_entry = builder_->graph()->NewNode(
         builder_->common()->OsrLoopEntry(), graph->start(), graph->start());
 
     builder_->MergeControl(control, osr_loop_entry);
     builder_->MergeEffect(effect, osr_loop_entry, control);
 
     for (int i = 0; i < size; ++i) {
       Node* val = values()->at(i);
       if (!IrOpcode::IsConstantOpcode(val->opcode())) {
         Node* osr_value =
             graph->NewNode(builder_->common()->OsrValue(i), osr_loop_entry);
         values()->at(i) = builder_->MergeValue(val, osr_value, control);
       }
     }
 
     // Rename all the contexts in the environment.
     // The innermost context is the OSR value, and the outer contexts are
     // reconstructed by dynamically walking up the context chain.
+    // TODO(titzer): use a real OSR value here; a parameter works by accident.

[titzer, 2015/07/03 09:28:17]

To get rid of this TODO, we need a special OSR value that will represent the
context on the stack that the linkage knows about. Then context specialization
won't be confused by seeing a weird parameter that really represents an OSR
value.

We should do this in a separate CL first.

[Michael Starzinger, 2015/07/06 13:08:40]

Done, see: https://codereview.chromium.org/1213043005/

+    Node* innermost_context = graph->NewNode(
+        builder_->common()->Parameter(
+            builder_->info()->num_parameters_including_this(), "%osr-context"),
+        graph->start());
     Node* osr_context = nullptr;
     const Operator* op =
         builder_->javascript()->LoadContext(0, Context::PREVIOUS_INDEX, true);
     int last = static_cast<int>(contexts()->size() - 1);
     for (int i = last; i >= 0; i--) {
       Node* val = contexts()->at(i);
-      if (!IrOpcode::IsConstantOpcode(val->opcode())) {
-        osr_context = (i == last) ? builder_->NewCurrentContextOsrValue()
+      if (!IrOpcode::IsConstantOpcode(val->opcode()) &&
+          (val != builder_->GetFunctionContext() ||
+           !builder_->info()->is_context_specializing())) {
+        osr_context = (i == last) ? innermost_context
                                   : graph->NewNode(op, osr_context, osr_context,
                                                    osr_loop_entry);
         contexts()->at(i) = builder_->MergeValue(val, osr_context, control);
       } else {
         osr_context = val;
       }
     }
   }
 }
 
@@ skipping 66 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