[turbofan] simplify gap ordering

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>
 #include <set>
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/frame.h"
 #include "src/compiler/instruction-codes.h"
 #include "src/compiler/opcodes.h"
 #include "src/compiler/register-configuration.h"
 #include "src/compiler/schedule.h"
 #include "src/compiler/source-position.h"
 #include "src/zone-allocator.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // A couple of reserved opcodes are used for internal use.
 const InstructionCode kGapInstruction = -1;
-const InstructionCode kBlockStartInstruction = -2;
-const InstructionCode kSourcePositionInstruction = -3;
+const InstructionCode kSourcePositionInstruction = -2;
 
 #define INSTRUCTION_OPERAND_LIST(V)                                  \
   V(Constant, CONSTANT, 0)                                           \
   V(Immediate, IMMEDIATE, 0)                                         \
   V(StackSlot, STACK_SLOT, 128)                                      \
   V(DoubleStackSlot, DOUBLE_STACK_SLOT, 128)                         \
   V(Register, REGISTER, RegisterConfiguration::kMaxGeneralRegisters) \
   V(DoubleRegister, DOUBLE_REGISTER, RegisterConfiguration::kMaxDoubleRegisters)
 
 class InstructionOperand : public ZoneObject {
@@ skipping 445 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 IsBlockStart() const { return opcode() == kBlockStartInstruction; }
+  bool IsGapMoves() const { return opcode() == kGapInstruction; }
   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_; }
 
   void set_pointer_map(PointerMap* map) {
@@ skipping 125 matching lines @@
     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 {
- 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) {}
-};
-
-
 class SourcePositionInstruction FINAL : public Instruction {
  public:
   static SourcePositionInstruction* New(Zone* zone, SourcePosition position) {
     void* buffer = zone->New(sizeof(SourcePositionInstruction));
     return new (buffer) SourcePositionInstruction(position);
   }
 
   SourcePosition source_position() const { return source_position_; }
 
   static SourcePositionInstruction* cast(Instruction* instr) {
@@ skipping 295 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;
+  GapInstruction* 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 91 matching lines @@
 
 
 std::ostream& operator<<(std::ostream& os,
                          const PrintableInstructionSequence& code);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_H_