[turbofan] fine grained in-block move optimization

src/compiler/move-optimizer.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_MOVE_OPTIMIZER_
 #define V8_COMPILER_MOVE_OPTIMIZER_
 
 #include "src/compiler/instruction.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 class MoveOptimizer final {
  public:
   MoveOptimizer(Zone* local_zone, InstructionSequence* code);
   void Run();
 
  private:
   typedef ZoneVector<MoveOperands*> MoveOpVector;
   typedef ZoneVector<Instruction*> Instructions;
 
   InstructionSequence* code() const { return code_; }
   Zone* local_zone() const { return local_zone_; }
   Zone* code_zone() const { return code()->zone(); }
   MoveOpVector& local_vector() { return local_vector_; }
 
-  void CompressBlock(InstructionBlock* blocke);
-  void CompressMoves(ParallelMove* left, ParallelMove* right);
+  // Consolidate moves into the first gap.
+  void CompressGaps(Instruction* instr);
+
+  // Attempt to push down to the last instruction those moves that can.
+  void CompressBlock(InstructionBlock* block);
+
+  // Consolidate moves into the first gap.
+  void CompressMoves(ParallelMove* left, MoveOpVector* right);
+
+  // Push down those moves in the gap of from that do not change the
+  // semantics of the from instruction, nor the semantics of the moves
+  // that remain behind.
+  void MigrateMoves(Instruction* to, Instruction* from);
+
+  void RemoveClobberedDestinations(Instruction* instruction);
+
   const Instruction* LastInstruction(const InstructionBlock* block) const;
+
+  // Consolidate common moves appearing accross all predecessors of a block.
   void OptimizeMerge(InstructionBlock* block);
   void FinalizeMoves(Instruction* instr);
 
   Zone* const local_zone_;
   InstructionSequence* const code_;
-  Instructions to_finalize_;
   MoveOpVector local_vector_;
 
   DISALLOW_COPY_AND_ASSIGN(MoveOptimizer);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_MOVE_OPTIMIZER_