[turbofan] put gaps before instructions

src/compiler/instruction.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_INSTRUCTION_H_
 #define V8_COMPILER_INSTRUCTION_H_
 
 #include <deque>
 #include <iosfwd>
 #include <map>
@@ skipping 477 matching lines @@
   }
   Instruction* MarkAsCall() {
     bit_field_ = IsCallField::update(bit_field_, true);
     return this;
   }
   bool IsControl() const { return IsControlField::decode(bit_field_); }
   bool IsCall() const { return IsCallField::decode(bit_field_); }
   bool NeedsPointerMap() const { return IsCall(); }
   bool HasPointerMap() const { return pointer_map_ != NULL; }
 
-  bool IsGapMoves() const {
-    return opcode() == kGapInstruction || opcode() == kBlockStartInstruction;
-  }
+  bool IsGapMoves() const { return opcode() == kGapInstruction; }
   bool IsBlockStart() const { return opcode() == kBlockStartInstruction; }
   bool IsSourcePosition() const {
     return opcode() == kSourcePositionInstruction;
   }
 
   bool ClobbersRegisters() const { return IsCall(); }
   bool ClobbersTemps() const { return IsCall(); }
   bool ClobbersDoubleRegisters() const { return IsCall(); }
   PointerMap* pointer_map() const { return pointer_map_; }
 
@@ skipping 83 matching lines @@
   ParallelMove* GetParallelMove(InnerPosition pos) {
     return parallel_moves_[pos];
   }
 
   const ParallelMove* GetParallelMove(InnerPosition pos) const {
     return parallel_moves_[pos];
   }
 
   static GapInstruction* New(Zone* zone) {
     void* buffer = zone->New(sizeof(GapInstruction));
-    return new (buffer) GapInstruction(kGapInstruction);
+    return new (buffer) GapInstruction();
   }
 
   static GapInstruction* cast(Instruction* instr) {
     DCHECK(instr->IsGapMoves());
     return static_cast<GapInstruction*>(instr);
   }
 
   static const GapInstruction* cast(const Instruction* instr) {
     DCHECK(instr->IsGapMoves());
     return static_cast<const GapInstruction*>(instr);
   }
 
- protected:
-  explicit GapInstruction(InstructionCode opcode) : Instruction(opcode) {
+ private:
+  GapInstruction() : Instruction(kGapInstruction) {
     parallel_moves_[BEFORE] = NULL;
     parallel_moves_[START] = NULL;
     parallel_moves_[END] = NULL;
     parallel_moves_[AFTER] = NULL;
   }
 
- private:
   friend std::ostream& operator<<(std::ostream& os,
                                   const PrintableInstruction& instr);
   ParallelMove* parallel_moves_[LAST_INNER_POSITION + 1];
 };
 
 
-// This special kind of gap move instruction represents the beginning of a
-// block of code.
-class BlockStartInstruction FINAL : public GapInstruction {
+// This is a placeholder instruction marking the start of a block.
+class BlockStartInstruction FINAL : public Instruction {
  public:
   static BlockStartInstruction* New(Zone* zone) {
     void* buffer = zone->New(sizeof(BlockStartInstruction));
     return new (buffer) BlockStartInstruction();
   }
 
   static BlockStartInstruction* cast(Instruction* instr) {
     DCHECK(instr->IsBlockStart());
     return static_cast<BlockStartInstruction*>(instr);
   }
 
   static const BlockStartInstruction* cast(const Instruction* instr) {
     DCHECK(instr->IsBlockStart());
     return static_cast<const BlockStartInstruction*>(instr);
   }
 
  private:
-  BlockStartInstruction() : GapInstruction(kBlockStartInstruction) {}
+  BlockStartInstruction() : Instruction(kBlockStartInstruction) {}
 };
 
 
 class SourcePositionInstruction FINAL : public Instruction {
  public:
   static SourcePositionInstruction* New(Zone* zone, SourcePosition position) {
     void* buffer = zone->New(sizeof(SourcePositionInstruction));
     return new (buffer) SourcePositionInstruction(position);
   }
 
@@ skipping 287 matching lines @@
   const InstructionBlock* GetInstructionBlock(int instruction_index) const;
 
   bool IsReference(int virtual_register) const;
   bool IsDouble(int virtual_register) const;
 
   void MarkAsReference(int virtual_register);
   void MarkAsDouble(int virtual_register);
 
   void AddGapMove(int index, InstructionOperand* from, InstructionOperand* to);
 
-  BlockStartInstruction* GetBlockStart(BasicBlock::RpoNumber rpo) const;
+  const BlockStartInstruction* GetBlockStart(BasicBlock::RpoNumber rpo) const;
 
   typedef InstructionDeque::const_iterator const_iterator;
   const_iterator begin() const { return instructions_.begin(); }
   const_iterator end() const { return instructions_.end(); }
   const InstructionDeque& instructions() const { return instructions_; }
 
   GapInstruction* GapAt(int index) const {
     return GapInstruction::cast(InstructionAt(index));
   }
   bool IsGapAt(int index) const { return InstructionAt(index)->IsGapMoves(); }
@@ skipping 82 matching lines @@
 
 
 std::ostream& operator<<(std::ostream& os,
                          const PrintableInstructionSequence& code);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_H_