[turbofan]: Add a context relaxation Reducer

src/compiler/ast-graph-builder.h

 // 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.
 
 #ifndef V8_COMPILER_AST_GRAPH_BUILDER_H_
 #define V8_COMPILER_AST_GRAPH_BUILDER_H_
 
 #include "src/ast.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/liveness-analyzer.h"
@@ skipping 34 matching lines @@
   Node* NewBranch(Node* condition, BranchHint hint = BranchHint::kNone) {
     return NewNode(common()->Branch(hint), condition);
   }
 
  protected:
 #define DECLARE_VISIT(type) void Visit##type(type* node) override;
   // Visiting functions for AST nodes make this an AstVisitor.
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
+  Node* relaxed_context() const { return relaxed_context_; }

[titzer, 2015/07/02 14:52:07]

Can we just call this the outer_context_param() ?

+
   // Visiting function for declarations list is overridden.
   void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
 
  private:
   class AstContext;
   class AstEffectContext;
   class AstValueContext;
   class AstTestContext;
   class ContextScope;
   class ControlScope;
@@ skipping 46 matching lines @@
 
   // Analyzer of local variable liveness.
   LivenessAnalyzer liveness_analyzer_;
 
   // Function info for frame state construction.
   const FrameStateFunctionInfo* const frame_state_function_info_;
 
   // Type feedback table.
   JSTypeFeedbackTable* js_type_feedback_;
 
+  // The context that can be used for context relaxation if possible, otherwise
+  // nullptr.
+  Node* relaxed_context_;
+
   // Growth increment for the temporary buffer used to construct input lists to
   // new nodes.
   static const int kInputBufferSizeIncrement = 64;
 
   Zone* local_zone() const { return local_zone_; }
   Environment* environment() const { return environment_; }
   AstContext* ast_context() const { return ast_context_; }
   ControlScope* execution_control() const { return execution_control_; }
   ContextScope* execution_context() const { return execution_context_; }
   CommonOperatorBuilder* common() const { return jsgraph_->common(); }
@@ skipping 417 matching lines @@
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_GRAPH_BUILDER_H_