[turbofan] Simply context specialization and fix for OSR.

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index c33cc60ce573afa4b9270c3f83a8588e3f085421..d502099f5aa23cb9b0835c73afc86314d1a4a93c 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -379,7 +379,6 @@ AstGraphBuilder::AstGraphBuilder(Zone* local_zone, CompilationInfo* info,
       globals_(0, local_zone),
       execution_control_(nullptr),
       execution_context_(nullptr),
-      function_context_(nullptr),
       input_buffer_size_(0),
       input_buffer_(nullptr),
       exit_control_(nullptr),
@@ -399,10 +398,7 @@ Node* AstGraphBuilder::GetFunctionClosure() {
 }
 
 
-Node* AstGraphBuilder::GetFunctionContext() {
-  DCHECK(function_context_ != nullptr);
-  return function_context_;
-}
+Node* AstGraphBuilder::GetFunctionContext() { return function_context_.get(); }
 
 
 Node* AstGraphBuilder::NewOuterContextParam() {
@@ -420,7 +416,7 @@ Node* AstGraphBuilder::NewCurrentContextOsrValue() {
 }
 
 
-bool AstGraphBuilder::CreateGraph() {
+bool AstGraphBuilder::CreateGraph(bool constant_context) {
   Scope* scope = info()->scope();
   DCHECK(graph() != NULL);
 
@@ -442,8 +438,12 @@ bool AstGraphBuilder::CreateGraph() {
   }
 
   // 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?
@@ -456,7 +456,8 @@ bool AstGraphBuilder::CreateGraph() {
   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 {
@@ -3041,6 +3042,7 @@ void AstGraphBuilder::Environment::Merge(Environment* other) {
         graph()->NewNode(common()->Merge(1), arraysize(inputs), inputs, true);
     effect_dependency_ = other->effect_dependency_;
     values_ = other->values_;
+    contexts_ = other->contexts_;
     return;
   }