src/cpu/static_inst.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2017, 2020 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Copyright (c) 2003-2005 The Regents of The University of Michigan
  * Copyright (c) 2013 Advanced Micro Devices, Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #ifndef __CPU_STATIC_INST_HH__
 #define __CPU_STATIC_INST_HH__

 #include <bitset>
 #include <memory>
 #include <string>

 #include "arch/registers.hh"
 #include "arch/types.hh"
 #include "base/logging.hh"
 #include "base/refcnt.hh"
 #include "base/types.hh"
 #include "config/the_isa.hh"
 #include "cpu/op_class.hh"
 #include "cpu/reg_class.hh"
 #include "cpu/static_inst_fwd.hh"
 #include "cpu/thread_context.hh"
 #include "enums/StaticInstFlags.hh"
 #include "sim/byteswap.hh"

 // forward declarations
 class Packet;

 class ExecContext;

 namespace Loader
 {
 class SymbolTable;
 } // namespace Loader

 namespace Trace
 {
 class InstRecord;
 } // namespace Trace

 /**
  * Base, ISA-independent static instruction class.
  *
  * The main component of this class is the vector of flags and the
  * associated methods for reading them.  Any object that can rely
  * solely on these flags can process instructions without being
  * recompiled for multiple ISAs.
  */
 class StaticInst : public RefCounted, public StaticInstFlags
 {
   public:
     using RegIdArrayPtr = RegId (StaticInst:: *)[];

   private:
     /// See srcRegIdx().
     RegIdArrayPtr _srcRegIdxPtr = nullptr;

     /// See destRegIdx().
     RegIdArrayPtr _destRegIdxPtr = nullptr;

   protected:

     /// Flag values for this instruction.
     std::bitset<Num_Flags> flags;

     /// See opClass().
     OpClass _opClass;

     /// See numSrcRegs().
     int8_t _numSrcRegs;

     /// See numDestRegs().
     int8_t _numDestRegs;

     /// The following are used to track physical register usage
     /// for machines with separate int & FP reg files.
     //@{
     int8_t _numFPDestRegs;
     int8_t _numIntDestRegs;
     int8_t _numCCDestRegs;
     //@}

     /** To use in architectures with vector register file. */
     /** @{ */
     int8_t _numVecDestRegs;
     int8_t _numVecElemDestRegs;
     int8_t _numVecPredDestRegs;
     /** @} */

   public:

     /// @name Register information.
     /// The sum of numFPDestRegs(), numIntDestRegs(), numVecDestRegs(),
     /// numVecElemDestRegs() and numVecPredDestRegs() equals numDestRegs().
     /// The former two functions are used to track physical register usage for
     /// machines with separate int & FP reg files, the next three are for
     /// machines with vector and predicate register files.
     //@{
     /// Number of source registers.
     int8_t numSrcRegs()  const { return _numSrcRegs; }
     /// Number of destination registers.
     int8_t numDestRegs() const { return _numDestRegs; }
     /// Number of floating-point destination regs.
     int8_t numFPDestRegs()  const { return _numFPDestRegs; }
     /// Number of integer destination regs.
     int8_t numIntDestRegs() const { return _numIntDestRegs; }
     /// Number of vector destination regs.
     int8_t numVecDestRegs() const { return _numVecDestRegs; }
     /// Number of vector element destination regs.
     int8_t numVecElemDestRegs() const { return _numVecElemDestRegs; }
     /// Number of predicate destination regs.
     int8_t numVecPredDestRegs() const { return _numVecPredDestRegs; }
     /// Number of coprocesor destination regs.
     int8_t numCCDestRegs() const { return _numCCDestRegs; }
     //@}

     /// @name Flag accessors.
     /// These functions are used to access the values of the various
     /// instruction property flags.  See StaticInst::Flags for descriptions
     /// of the individual flags.
     //@{

     bool isNop()          const { return flags[IsNop]; }

     bool
     isMemRef() const
     {
         return flags[IsLoad] || flags[IsStore] || flags[IsAtomic];
     }
     bool isLoad()         const { return flags[IsLoad]; }
     bool isStore()        const { return flags[IsStore]; }
     bool isAtomic()       const { return flags[IsAtomic]; }
     bool isStoreConditional()     const { return flags[IsStoreConditional]; }
     bool isInstPrefetch() const { return flags[IsInstPrefetch]; }
     bool isDataPrefetch() const { return flags[IsDataPrefetch]; }
     bool isPrefetch()     const { return isInstPrefetch() ||
                                          isDataPrefetch(); }

     bool isInteger()      const { return flags[IsInteger]; }
     bool isFloating()     const { return flags[IsFloating]; }
     bool isVector()       const { return flags[IsVector]; }

     bool isControl()      const { return flags[IsControl]; }
     bool isCall()         const { return flags[IsCall]; }
     bool isReturn()       const { return flags[IsReturn]; }
     bool isDirectCtrl()   const { return flags[IsDirectControl]; }
     bool isIndirectCtrl() const { return flags[IsIndirectControl]; }
     bool isCondCtrl()     const { return flags[IsCondControl]; }
     bool isUncondCtrl()   const { return flags[IsUncondControl]; }

     bool isSerializing()  const { return flags[IsSerializing] ||
                                       flags[IsSerializeBefore] ||
                                       flags[IsSerializeAfter]; }
     bool isSerializeBefore() const { return flags[IsSerializeBefore]; }
     bool isSerializeAfter() const { return flags[IsSerializeAfter]; }
     bool isSquashAfter() const { return flags[IsSquashAfter]; }
     bool
     isFullMemBarrier() const
     {
         return flags[IsReadBarrier] && flags[IsWriteBarrier];
     }
     bool isReadBarrier() const { return flags[IsReadBarrier]; }
     bool isWriteBarrier() const { return flags[IsWriteBarrier]; }
     bool isNonSpeculative() const { return flags[IsNonSpeculative]; }
     bool isQuiesce() const { return flags[IsQuiesce]; }
     bool isUnverifiable() const { return flags[IsUnverifiable]; }
     bool isSyscall() const { return flags[IsSyscall]; }
     bool isMacroop() const { return flags[IsMacroop]; }
     bool isMicroop() const { return flags[IsMicroop]; }
     bool isDelayedCommit() const { return flags[IsDelayedCommit]; }
     bool isLastMicroop() const { return flags[IsLastMicroop]; }
     bool isFirstMicroop() const { return flags[IsFirstMicroop]; }
     // hardware transactional memory
     // HtmCmds must be identified as such in order
     // to provide them with necessary memory ordering semantics.
     bool isHtmStart() const { return flags[IsHtmStart]; }
     bool isHtmStop() const { return flags[IsHtmStop]; }
     bool isHtmCancel() const { return flags[IsHtmCancel]; }

     bool
     isHtmCmd() const
     {
         return isHtmStart() || isHtmStop() || isHtmCancel();
     }
     //@}

     void setFirstMicroop() { flags[IsFirstMicroop] = true; }
     void setLastMicroop() { flags[IsLastMicroop] = true; }
     void setDelayedCommit() { flags[IsDelayedCommit] = true; }
     void setFlag(Flags f) { flags[f] = true; }

     /// Operation class.  Used to select appropriate function unit in issue.
     OpClass opClass()     const { return _opClass; }


     /// Return logical index (architectural reg num) of i'th destination reg.
     /// Only the entries from 0 through numDestRegs()-1 are valid.
     const RegId &destRegIdx(int i) const { return (this->*_destRegIdxPtr)[i]; }

     void
     setDestRegIdx(int i, const RegId &val)
     {
         (this->*_destRegIdxPtr)[i] = val;
     }

     /// Return logical index (architectural reg num) of i'th source reg.
     /// Only the entries from 0 through numSrcRegs()-1 are valid.
     const RegId &srcRegIdx(int i) const { return (this->*_srcRegIdxPtr)[i]; }

     void
     setSrcRegIdx(int i, const RegId &val)
     {
         (this->*_srcRegIdxPtr)[i] = val;
     }

     /// Pointer to a statically allocated "null" instruction object.
     static StaticInstPtr nullStaticInstPtr;

     /// Pointer to a statically allocated generic "nop" instruction object.
     static StaticInstPtr nopStaticInstPtr;

     /// The binary machine instruction.
     const TheISA::ExtMachInst machInst;

     virtual uint64_t getEMI() const { return 0; }

   protected:

     /**
      * Set the pointers which point to the arrays of source and destination
      * register indices. These will be defined in derived classes which know
      * what size they need to be, and installed here so they can be accessed
      * with the base class accessors.
      */
     void
     setRegIdxArrays(RegIdArrayPtr src, RegIdArrayPtr dest)
     {
         _srcRegIdxPtr = src;
         _destRegIdxPtr = dest;
     }

     /**
      * Base mnemonic (e.g., "add").  Used by generateDisassembly()
      * methods.  Also useful to readily identify instructions from
      * within the debugger when #cachedDisassembly has not been
      * initialized.
      */
     const char *mnemonic;

     /**
      * String representation of disassembly (lazily evaluated via
      * disassemble()).
      */
     mutable std::string *cachedDisassembly;

     /**
      * Internal function to generate disassembly string.
      */
     virtual std::string
     generateDisassembly(Addr pc, const Loader::SymbolTable *symtab) const = 0;

     /// Constructor.
     /// It's important to initialize everything here to a sane
     /// default, since the decoder generally only overrides
     /// the fields that are meaningful for the particular
     /// instruction.
     StaticInst(const char *_mnemonic, TheISA::ExtMachInst _machInst,
             OpClass __opClass)
         : _opClass(__opClass),
           _numSrcRegs(0), _numDestRegs(0), _numFPDestRegs(0),
           _numIntDestRegs(0), _numCCDestRegs(0), _numVecDestRegs(0),
           _numVecElemDestRegs(0), _numVecPredDestRegs(0), machInst(_machInst),
           mnemonic(_mnemonic), cachedDisassembly(0)
     { }

   public:
     virtual ~StaticInst();

     virtual Fault execute(ExecContext *xc,
                           Trace::InstRecord *traceData) const = 0;

     virtual Fault initiateAcc(ExecContext *xc,
                               Trace::InstRecord *traceData) const
     {
         panic("initiateAcc not defined!");
     }

     virtual Fault completeAcc(Packet *pkt, ExecContext *xc,
                               Trace::InstRecord *traceData) const
     {
         panic("completeAcc not defined!");
     }

     virtual void advancePC(TheISA::PCState &pcState) const = 0;

     /**
      * Return the microop that goes with a particular micropc. This should
      * only be defined/used in macroops which will contain microops
      */
     virtual StaticInstPtr fetchMicroop(MicroPC upc) const;

     /**
      * Return the target address for a PC-relative branch.
      * Invalid if not a PC-relative branch (i.e. isDirectCtrl()
      * should be true).
      */
     virtual TheISA::PCState branchTarget(const TheISA::PCState &pc) const;

     /**
      * Return the target address for an indirect branch (jump).  The
      * register value is read from the supplied thread context, so
      * the result is valid only if the thread context is about to
      * execute the branch in question.  Invalid if not an indirect
      * branch (i.e. isIndirectCtrl() should be true).
      */
     virtual TheISA::PCState branchTarget(ThreadContext *tc) const;

     /**
      * Return true if the instruction is a control transfer, and if so,
      * return the target address as well.
      */
     bool hasBranchTarget(const TheISA::PCState &pc, ThreadContext *tc,
                          TheISA::PCState &tgt) const;

     /**
      * Return string representation of disassembled instruction.
      * The default version of this function will call the internal
      * virtual generateDisassembly() function to get the string,
      * then cache it in #cachedDisassembly.  If the disassembly
      * should not be cached, this function should be overridden directly.
      */
     virtual const std::string &disassemble(Addr pc,
         const Loader::SymbolTable *symtab=nullptr) const;

     /**
      * Print a separator separated list of this instruction's set flag
      * names on the given stream.
      */
     void printFlags(std::ostream &outs, const std::string &separator) const;

     /// Return name of machine instruction
     std::string getName() { return mnemonic; }

   protected:
     template<typename T>
     size_t
     simpleAsBytes(void *buf, size_t max_size, const T &t)
     {
         size_t size = sizeof(T);
         if (size <= max_size)
             *reinterpret_cast<T *>(buf) = htole<T>(t);
         return size;
     }

   public:
     /**
      * Instruction classes can override this function to return a
      * a representation of themselves as a blob of bytes, generally assumed to
      * be that instructions ExtMachInst.
      *
      * buf is a buffer to hold the bytes.
      * max_size is the size allocated for that buffer by the caller.
      * The return value is how much data was actually put into the buffer,
      * zero if no data was put in the buffer, or the necessary size of the
      * buffer if there wasn't enough space.
      */
     virtual size_t asBytes(void *buf, size_t max_size) { return 0; }
 };

 #endif // __CPU_STATIC_INST_HH__
	/*
	* Copyright (c) 2017, 2020 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Copyright (c) 2003-2005 The Regents of The University of Michigan
	* Copyright (c) 2013 Advanced Micro Devices, Inc.
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#ifndef __CPU_STATIC_INST_HH__
	#define __CPU_STATIC_INST_HH__

	#include <bitset>
	#include <memory>
	#include <string>

	#include "arch/registers.hh"
	#include "arch/types.hh"
	#include "base/logging.hh"
	#include "base/refcnt.hh"
	#include "base/types.hh"
	#include "config/the_isa.hh"
	#include "cpu/op_class.hh"
	#include "cpu/reg_class.hh"
	#include "cpu/static_inst_fwd.hh"
	#include "cpu/thread_context.hh"
	#include "enums/StaticInstFlags.hh"
	#include "sim/byteswap.hh"

	// forward declarations
	class Packet;

	class ExecContext;

	namespace Loader
	{
	class SymbolTable;
	} // namespace Loader

	namespace Trace
	{
	class InstRecord;
	} // namespace Trace

	/**
	* Base, ISA-independent static instruction class.
	*
	* The main component of this class is the vector of flags and the
	* associated methods for reading them. Any object that can rely
	* solely on these flags can process instructions without being
	* recompiled for multiple ISAs.
	*/
	class StaticInst : public RefCounted, public StaticInstFlags
	{
	public:
	using RegIdArrayPtr = RegId (StaticInst:: *)[];

	private:
	/// See srcRegIdx().
	RegIdArrayPtr _srcRegIdxPtr = nullptr;

	/// See destRegIdx().
	RegIdArrayPtr _destRegIdxPtr = nullptr;

	protected:

	/// Flag values for this instruction.
	std::bitset<Num_Flags> flags;

	/// See opClass().
	OpClass _opClass;

	/// See numSrcRegs().
	int8_t _numSrcRegs;

	/// See numDestRegs().
	int8_t _numDestRegs;

	/// The following are used to track physical register usage
	/// for machines with separate int & FP reg files.
	//@{
	int8_t _numFPDestRegs;
	int8_t _numIntDestRegs;
	int8_t _numCCDestRegs;
	//@}

	/** To use in architectures with vector register file. */
	/** @{ */
	int8_t _numVecDestRegs;
	int8_t _numVecElemDestRegs;
	int8_t _numVecPredDestRegs;
	/** @} */

	public:

	/// @name Register information.
	/// The sum of numFPDestRegs(), numIntDestRegs(), numVecDestRegs(),
	/// numVecElemDestRegs() and numVecPredDestRegs() equals numDestRegs().
	/// The former two functions are used to track physical register usage for
	/// machines with separate int & FP reg files, the next three are for
	/// machines with vector and predicate register files.
	//@{
	/// Number of source registers.
	int8_t numSrcRegs() const { return _numSrcRegs; }
	/// Number of destination registers.
	int8_t numDestRegs() const { return _numDestRegs; }
	/// Number of floating-point destination regs.
	int8_t numFPDestRegs() const { return _numFPDestRegs; }
	/// Number of integer destination regs.
	int8_t numIntDestRegs() const { return _numIntDestRegs; }
	/// Number of vector destination regs.
	int8_t numVecDestRegs() const { return _numVecDestRegs; }
	/// Number of vector element destination regs.
	int8_t numVecElemDestRegs() const { return _numVecElemDestRegs; }
	/// Number of predicate destination regs.
	int8_t numVecPredDestRegs() const { return _numVecPredDestRegs; }
	/// Number of coprocesor destination regs.
	int8_t numCCDestRegs() const { return _numCCDestRegs; }
	//@}

	/// @name Flag accessors.
	/// These functions are used to access the values of the various
	/// instruction property flags. See StaticInst::Flags for descriptions
	/// of the individual flags.
	//@{

	bool isNop() const { return flags[IsNop]; }

	bool
	isMemRef() const
	{
	return flags[IsLoad] \|\| flags[IsStore] \|\| flags[IsAtomic];
	}
	bool isLoad() const { return flags[IsLoad]; }
	bool isStore() const { return flags[IsStore]; }
	bool isAtomic() const { return flags[IsAtomic]; }
	bool isStoreConditional() const { return flags[IsStoreConditional]; }
	bool isInstPrefetch() const { return flags[IsInstPrefetch]; }
	bool isDataPrefetch() const { return flags[IsDataPrefetch]; }
	bool isPrefetch() const { return isInstPrefetch() \|\|
	isDataPrefetch(); }

	bool isInteger() const { return flags[IsInteger]; }
	bool isFloating() const { return flags[IsFloating]; }
	bool isVector() const { return flags[IsVector]; }

	bool isControl() const { return flags[IsControl]; }
	bool isCall() const { return flags[IsCall]; }
	bool isReturn() const { return flags[IsReturn]; }
	bool isDirectCtrl() const { return flags[IsDirectControl]; }
	bool isIndirectCtrl() const { return flags[IsIndirectControl]; }
	bool isCondCtrl() const { return flags[IsCondControl]; }
	bool isUncondCtrl() const { return flags[IsUncondControl]; }

	bool isSerializing() const { return flags[IsSerializing] \|\|
	flags[IsSerializeBefore] \|\|
	flags[IsSerializeAfter]; }
	bool isSerializeBefore() const { return flags[IsSerializeBefore]; }
	bool isSerializeAfter() const { return flags[IsSerializeAfter]; }
	bool isSquashAfter() const { return flags[IsSquashAfter]; }
	bool
	isFullMemBarrier() const
	{
	return flags[IsReadBarrier] && flags[IsWriteBarrier];
	}
	bool isReadBarrier() const { return flags[IsReadBarrier]; }
	bool isWriteBarrier() const { return flags[IsWriteBarrier]; }
	bool isNonSpeculative() const { return flags[IsNonSpeculative]; }
	bool isQuiesce() const { return flags[IsQuiesce]; }
	bool isUnverifiable() const { return flags[IsUnverifiable]; }
	bool isSyscall() const { return flags[IsSyscall]; }
	bool isMacroop() const { return flags[IsMacroop]; }
	bool isMicroop() const { return flags[IsMicroop]; }
	bool isDelayedCommit() const { return flags[IsDelayedCommit]; }
	bool isLastMicroop() const { return flags[IsLastMicroop]; }
	bool isFirstMicroop() const { return flags[IsFirstMicroop]; }
	// hardware transactional memory
	// HtmCmds must be identified as such in order
	// to provide them with necessary memory ordering semantics.
	bool isHtmStart() const { return flags[IsHtmStart]; }
	bool isHtmStop() const { return flags[IsHtmStop]; }
	bool isHtmCancel() const { return flags[IsHtmCancel]; }

	bool
	isHtmCmd() const
	{
	return isHtmStart() \|\| isHtmStop() \|\| isHtmCancel();
	}
	//@}

	void setFirstMicroop() { flags[IsFirstMicroop] = true; }
	void setLastMicroop() { flags[IsLastMicroop] = true; }
	void setDelayedCommit() { flags[IsDelayedCommit] = true; }
	void setFlag(Flags f) { flags[f] = true; }

	/// Operation class. Used to select appropriate function unit in issue.
	OpClass opClass() const { return _opClass; }


	/// Return logical index (architectural reg num) of i'th destination reg.
	/// Only the entries from 0 through numDestRegs()-1 are valid.
	const RegId &destRegIdx(int i) const { return (this->*_destRegIdxPtr)[i]; }

	void
	setDestRegIdx(int i, const RegId &val)
	{
	(this->*_destRegIdxPtr)[i] = val;
	}

	/// Return logical index (architectural reg num) of i'th source reg.
	/// Only the entries from 0 through numSrcRegs()-1 are valid.
	const RegId &srcRegIdx(int i) const { return (this->*_srcRegIdxPtr)[i]; }

	void
	setSrcRegIdx(int i, const RegId &val)
	{
	(this->*_srcRegIdxPtr)[i] = val;
	}

	/// Pointer to a statically allocated "null" instruction object.
	static StaticInstPtr nullStaticInstPtr;

	/// Pointer to a statically allocated generic "nop" instruction object.
	static StaticInstPtr nopStaticInstPtr;

	/// The binary machine instruction.
	const TheISA::ExtMachInst machInst;

	virtual uint64_t getEMI() const { return 0; }

	protected:

	/**
	* Set the pointers which point to the arrays of source and destination
	* register indices. These will be defined in derived classes which know
	* what size they need to be, and installed here so they can be accessed
	* with the base class accessors.
	*/
	void
	setRegIdxArrays(RegIdArrayPtr src, RegIdArrayPtr dest)
	{
	_srcRegIdxPtr = src;
	_destRegIdxPtr = dest;
	}

	/**
	* Base mnemonic (e.g., "add"). Used by generateDisassembly()
	* methods. Also useful to readily identify instructions from
	* within the debugger when #cachedDisassembly has not been
	* initialized.
	*/
	const char *mnemonic;

	/**
	* String representation of disassembly (lazily evaluated via
	* disassemble()).
	*/
	mutable std::string *cachedDisassembly;

	/**
	* Internal function to generate disassembly string.
	*/
	virtual std::string
	generateDisassembly(Addr pc, const Loader::SymbolTable *symtab) const = 0;

	/// Constructor.
	/// It's important to initialize everything here to a sane
	/// default, since the decoder generally only overrides
	/// the fields that are meaningful for the particular
	/// instruction.
	StaticInst(const char *_mnemonic, TheISA::ExtMachInst _machInst,
	OpClass __opClass)
	: _opClass(__opClass),
	_numSrcRegs(0), _numDestRegs(0), _numFPDestRegs(0),
	_numIntDestRegs(0), _numCCDestRegs(0), _numVecDestRegs(0),
	_numVecElemDestRegs(0), _numVecPredDestRegs(0), machInst(_machInst),
	mnemonic(_mnemonic), cachedDisassembly(0)
	{ }

	public:
	virtual ~StaticInst();

	virtual Fault execute(ExecContext *xc,
	Trace::InstRecord *traceData) const = 0;

	virtual Fault initiateAcc(ExecContext *xc,
	Trace::InstRecord *traceData) const
	{
	panic("initiateAcc not defined!");
	}

	virtual Fault completeAcc(Packet pkt, ExecContext xc,
	Trace::InstRecord *traceData) const
	{
	panic("completeAcc not defined!");
	}

	virtual void advancePC(TheISA::PCState &pcState) const = 0;

	/**
	* Return the microop that goes with a particular micropc. This should
	* only be defined/used in macroops which will contain microops
	*/
	virtual StaticInstPtr fetchMicroop(MicroPC upc) const;

	/**
	* Return the target address for a PC-relative branch.
	* Invalid if not a PC-relative branch (i.e. isDirectCtrl()
	* should be true).
	*/
	virtual TheISA::PCState branchTarget(const TheISA::PCState &pc) const;

	/**
	* Return the target address for an indirect branch (jump). The
	* register value is read from the supplied thread context, so
	* the result is valid only if the thread context is about to
	* execute the branch in question. Invalid if not an indirect
	* branch (i.e. isIndirectCtrl() should be true).
	*/
	virtual TheISA::PCState branchTarget(ThreadContext *tc) const;

	/**
	* Return true if the instruction is a control transfer, and if so,
	* return the target address as well.
	*/
	bool hasBranchTarget(const TheISA::PCState &pc, ThreadContext *tc,
	TheISA::PCState &tgt) const;

	/**
	* Return string representation of disassembled instruction.
	* The default version of this function will call the internal
	* virtual generateDisassembly() function to get the string,
	* then cache it in #cachedDisassembly. If the disassembly
	* should not be cached, this function should be overridden directly.
	*/
	virtual const std::string &disassemble(Addr pc,
	const Loader::SymbolTable *symtab=nullptr) const;

	/**
	* Print a separator separated list of this instruction's set flag
	* names on the given stream.
	*/
	void printFlags(std::ostream &outs, const std::string &separator) const;

	/// Return name of machine instruction
	std::string getName() { return mnemonic; }

	protected:
	template<typename T>
	size_t
	simpleAsBytes(void *buf, size_t max_size, const T &t)
	{
	size_t size = sizeof(T);
	if (size <= max_size)
	reinterpret_cast<T >(buf) = htole<T>(t);
	return size;
	}

	public:
	/**
	* Instruction classes can override this function to return a
	* a representation of themselves as a blob of bytes, generally assumed to
	* be that instructions ExtMachInst.
	*
	* buf is a buffer to hold the bytes.
	* max_size is the size allocated for that buffer by the caller.
	* The return value is how much data was actually put into the buffer,
	* zero if no data was put in the buffer, or the necessary size of the
	* buffer if there wasn't enough space.
	*/
	virtual size_t asBytes(void *buf, size_t max_size) { return 0; }
	};

	#endif // __CPU_STATIC_INST_HH__