[turbofan] Avoid embedding type feedback vector into code.

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index 2c9f1be4c9d903b2c74ef95e947293cac986054c..ce4ec8ea17cfeaf76fc9c842319d6c45de217692 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -88,7 +88,6 @@ class AstGraphBuilder : public AstVisitor {
   // Nodes representing values in the activation record.
   SetOncePointer<Node> function_closure_;
   SetOncePointer<Node> function_context_;
-  SetOncePointer<Node> feedback_vector_;
 
   // Tracks how many try-blocks are currently entered.
   int try_catch_nesting_level_;
@@ -98,6 +97,10 @@ class AstGraphBuilder : public AstVisitor {
   int input_buffer_size_;
   Node** input_buffer_;
 
+  // Optimization to cache loaded feedback vector.
+  // TODO(mstarzinger): Can we let GVN take care of that?

[Michael Starzinger, 2015/06/22 14:57:56]

Is there particular reason why machine loads are not marked as kIdempotent?

[Benedikt Meurer, 2015/06/23 04:12:38]

I'm not sure if we can mark Load as idempotent. We could try.
But independent of that, we should still canonicalize the feedback vector in the
AstGraphBuilder; this optimization is cheap and local, and w/o it we'd create
two additional nodes per feedback vector user.

[Michael Starzinger, 2015/06/23 07:59:22]

Acknowledged. Removed the TODO.

+  SetOncePointer<Node> feedback_vector_;
+
   // Control nodes that exit the function body.
   ZoneVector<Node*> exit_controls_;
 
@@ -149,9 +152,6 @@ class AstGraphBuilder : public AstVisitor {
   Node* GetFunctionClosureForContext();
   Node* GetFunctionClosure();
 
-  // Get or create the node that represents the functions type feedback vector.
-  Node* GetFeedbackVector();
-
   // Node creation helpers.
   Node* NewNode(const Operator* op, bool incomplete = false) {
     return MakeNode(op, 0, static_cast<Node**>(NULL), incomplete);
@@ -306,8 +306,10 @@ class AstGraphBuilder : public AstVisitor {
   Node* BuildLoadBuiltinsObject();
   Node* BuildLoadGlobalObject();
   Node* BuildLoadGlobalProxy();
-  Node* BuildLoadClosure();
-  Node* BuildLoadObjectField(Node* object, int offset);
+  Node* BuildLoadFeedbackVector();
+
+  // Builder for accessing a (potentially immutable) object field.
+  Node* BuildLoadObjectField(Node* object, int offset, bool immutable = false);
 
   // Builders for accessing external references.
   Node* BuildLoadExternal(ExternalReference ref, MachineType type);