src/cpu/static_inst.hh

/*
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 * to a hardware implementation of the functionality of the software
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 * Copyright (c) 2003-2005 The Regents of The University of Michigan
 * Copyright (c) 2013 Advanced Micro Devices, Inc.
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 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
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#ifndef __CPU_STATIC_INST_HH__
#define __CPU_STATIC_INST_HH__

#include <array>
#include <bitset>
#include <cstdint>
#include <memory>
#include <string>

#include "arch/generic/pcstate.hh"
#include "base/logging.hh"
#include "base/refcnt.hh"
#include "cpu/op_class.hh"
#include "cpu/reg_class.hh"
#include "cpu/static_inst_fwd.hh"
#include "enums/StaticInstFlags.hh"
#include "sim/byteswap.hh"

namespace gem5
{

// forward declarations
class Packet;

class ExecContext;
class ThreadContext;

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().
    uint8_t _numSrcRegs = 0;

    /// See numDestRegs().
    uint8_t _numDestRegs = 0;

    std::array<uint8_t, MiscRegClass + 1> _numTypedDestRegs = {};

  public:

    /// @name Register information.
    /// The sum of the different numDestRegs([type])-s equals numDestRegs().
    /// The per-type function is used to track physical register usage.
    //@{
    /// Number of source registers.
    uint8_t numSrcRegs()  const { return _numSrcRegs; }
    /// Number of destination registers.
    uint8_t numDestRegs() const { return _numDestRegs; }
    /// Number of destination registers of a particular type.
    uint8_t
    numDestRegs(RegClassType type) const
    {
        return _numTypedDestRegs[type];
    }
    //@}

    /// @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 isMatrix()       const { return flags[IsMatrix]; }

    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;

    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::unique_ptr<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, OpClass op_class)
        : _opClass(op_class), mnemonic(_mnemonic)
    {}

  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 *trace_data) const
    {
        panic("completeAcc not defined!");
    }

    virtual void advancePC(PCStateBase &pc_state) const = 0;
    virtual void advancePC(ThreadContext *tc) const;

    virtual std::unique_ptr<PCStateBase>
    buildRetPC(const PCStateBase &cur_pc, const PCStateBase &call_pc) const
    {
        panic("buildRetPC not defined!");
    }

    /**
     * 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 std::unique_ptr<PCStateBase> branchTarget(
            const PCStateBase &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 std::unique_ptr<PCStateBase> branchTarget(
            ThreadContext *tc) 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; }
};

} // namespace gem5

#endif // __CPU_STATIC_INST_HH__