MIPS: Improve performance of simulator in debug mode.

src/mips/simulator-mips.h

Index: src/mips/simulator-mips.h
diff --git a/src/mips/simulator-mips.h b/src/mips/simulator-mips.h
index 5c77756394e24d55fe15af266d91dea9add0e4f9..394d8e650a88a02e2bc2ad10fb9ca44de87aa5d0 100644
--- a/src/mips/simulator-mips.h
+++ b/src/mips/simulator-mips.h
@@ -113,6 +113,39 @@ class CachePage {
   char validity_map_[kValidityMapSize];  // One byte per line.
 };
 
+class SimInstructionBase : public InstructionBase {
+ public:
+  Type InstructionType() const { return type_; }
+  inline Instruction* instr() const { return instr_; }
+  inline int32_t operand() const { return operand_; }
+
+ protected:
+  SimInstructionBase() : operand_(-1), instr_(nullptr), type_(kUnsupported) {}
+  explicit SimInstructionBase(Instruction* instr) {}
+
+  int32_t operand_;
+  Instruction* instr_;
+  Type type_;
+
+ private:
+  DISALLOW_ASSIGN(SimInstructionBase);
+};
+
+class SimInstruction : public InstructionGetters<SimInstructionBase> {
+ public:
+  SimInstruction() {}
+
+  explicit SimInstruction(Instruction* instr) { *this = instr; }
+
+  SimInstruction& operator=(Instruction* instr) {
+    operand_ = *reinterpret_cast<const int32_t*>(instr);
+    instr_ = instr;
+    type_ = InstructionBase::InstructionType(EXTRA);
+    DCHECK(reinterpret_cast<void*>(&operand_) == this);
+    return *this;
+  }
+};
+
 class Simulator {
  public:
   friend class MipsDebugger;
@@ -299,8 +332,10 @@ class Simulator {
   inline int32_t SetDoubleHIW(double* addr);
   inline int32_t SetDoubleLOW(double* addr);
 
+  SimInstruction instr_;
+
   // Executing is handled based on the instruction type.
-  void DecodeTypeRegister(Instruction* instr);
+  void DecodeTypeRegister();
 
   // Functions called from DecodeTypeRegister.
   void DecodeTypeRegisterCOP1();
@@ -322,39 +357,34 @@ class Simulator {
 
   void DecodeTypeRegisterLRsType();
 
-  Instruction* currentInstr_;
-
-  inline Instruction* get_instr() const { return currentInstr_; }
-  inline void set_instr(Instruction* instr) { currentInstr_ = instr; }
-
-  inline int32_t rs_reg() const { return currentInstr_->RsValue(); }
+  inline int32_t rs_reg() const { return instr_.RsValue(); }
   inline int32_t rs() const { return get_register(rs_reg()); }
   inline uint32_t rs_u() const {
     return static_cast<uint32_t>(get_register(rs_reg()));
   }
-  inline int32_t rt_reg() const { return currentInstr_->RtValue(); }
+  inline int32_t rt_reg() const { return instr_.RtValue(); }
   inline int32_t rt() const { return get_register(rt_reg()); }
   inline uint32_t rt_u() const {
     return static_cast<uint32_t>(get_register(rt_reg()));
   }
-  inline int32_t rd_reg() const { return currentInstr_->RdValue(); }
-  inline int32_t fr_reg() const { return currentInstr_->FrValue(); }
-  inline int32_t fs_reg() const { return currentInstr_->FsValue(); }
-  inline int32_t ft_reg() const { return currentInstr_->FtValue(); }
-  inline int32_t fd_reg() const { return currentInstr_->FdValue(); }
-  inline int32_t sa() const { return currentInstr_->SaValue(); }
-  inline int32_t lsa_sa() const { return currentInstr_->LsaSaValue(); }
+  inline int32_t rd_reg() const { return instr_.RdValue(); }
+  inline int32_t fr_reg() const { return instr_.FrValue(); }
+  inline int32_t fs_reg() const { return instr_.FsValue(); }
+  inline int32_t ft_reg() const { return instr_.FtValue(); }
+  inline int32_t fd_reg() const { return instr_.FdValue(); }
+  inline int32_t sa() const { return instr_.SaValue(); }
+  inline int32_t lsa_sa() const { return instr_.LsaSaValue(); }
 
   inline void SetResult(int32_t rd_reg, int32_t alu_out) {
     set_register(rd_reg, alu_out);
     TraceRegWr(alu_out);
   }
 
-  void DecodeTypeImmediate(Instruction* instr);
-  void DecodeTypeJump(Instruction* instr);
+  void DecodeTypeImmediate();
+  void DecodeTypeJump();
 
   // Used for breakpoints and traps.
-  void SoftwareInterrupt(Instruction* instr);
+  void SoftwareInterrupt();
 
   // Compact branch guard.
   void CheckForbiddenSlot(int32_t current_pc) {