free_list.hh

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/*
 * Copyright (c) 2004-2005 The Regents of The University of Michigan
 * Copyright (c) 2013 Advanced Micro Devices, Inc.
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 * 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
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 * 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
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 * Authors: Kevin Lim
 */

#ifndef __CPU_O3_FREE_LIST_HH__
#define __CPU_O3_FREE_LIST_HH__

#include <iostream>
#include <queue>

#include "base/misc.hh"
#include "base/trace.hh"
#include "cpu/o3/comm.hh"
#include "cpu/o3/regfile.hh"
#include "debug/FreeList.hh"

class SimpleFreeList
{
  private:

    std::queue<PhysRegIndex> freeRegs;

  public:

    SimpleFreeList() {};

    void addReg(PhysRegIndex reg) { freeRegs.push(reg); }

    PhysRegIndex getReg()
    {
        assert(!freeRegs.empty());
        PhysRegIndex free_reg = freeRegs.front();
        freeRegs.pop();
        return free_reg;
    }

    unsigned numFreeRegs() const { return freeRegs.size(); }

    bool hasFreeRegs() const { return !freeRegs.empty(); }
};


class UnifiedFreeList
{
  private:

    const std::string _name;

    SimpleFreeList intList;

    SimpleFreeList floatList;

    SimpleFreeList ccList;

    PhysRegFile *regFile;

    /*
     * We give UnifiedRenameMap internal access so it can get at the
     * internal per-class free lists and associate those with its
     * per-class rename maps. See UnifiedRenameMap::init().
     */
    friend class UnifiedRenameMap;

  public:
    UnifiedFreeList(const std::string &_my_name, PhysRegFile *_regFile);

    std::string name() const { return _name; };

    SimpleFreeList *getCCList() { return &ccList; }

    PhysRegIndex getIntReg() { return intList.getReg(); }

    PhysRegIndex getFloatReg() { return floatList.getReg(); }

    PhysRegIndex getCCReg() { return ccList.getReg(); }

    void addReg(PhysRegIndex freed_reg);

    void addIntReg(PhysRegIndex freed_reg) { intList.addReg(freed_reg); }

    void addFloatReg(PhysRegIndex freed_reg) { floatList.addReg(freed_reg); }

    void addCCReg(PhysRegIndex freed_reg) { ccList.addReg(freed_reg); }

    bool hasFreeIntRegs() const { return intList.hasFreeRegs(); }

    bool hasFreeFloatRegs() const { return floatList.hasFreeRegs(); }

    bool hasFreeCCRegs() const { return ccList.hasFreeRegs(); }

    unsigned numFreeIntRegs() const { return intList.numFreeRegs(); }

    unsigned numFreeFloatRegs() const { return floatList.numFreeRegs(); }

    unsigned numFreeCCRegs() const { return ccList.numFreeRegs(); }
};

inline void
UnifiedFreeList::addReg(PhysRegIndex freed_reg)
{
    DPRINTF(FreeList,"Freeing register %i.\n", freed_reg);
    //Might want to add in a check for whether or not this register is
    //already in there.  A bit vector or something similar would be useful.
    if (regFile->isIntPhysReg(freed_reg)) {
        intList.addReg(freed_reg);
    } else if (regFile->isFloatPhysReg(freed_reg)) {
        floatList.addReg(freed_reg);
    } else {
        assert(regFile->isCCPhysReg(freed_reg));
        ccList.addReg(freed_reg);
    }

    // These assert conditions ensure that the number of free
    // registers are not more than the # of total Physical  Registers.
    // If this were false, it would mean that registers
    // have been freed twice, overflowing the free register
    // pool and potentially crashing SMT workloads.
    // ----
    // Comment out for now so as to not potentially break
    // CMP and single-threaded workloads
    // ----
    // assert(freeIntRegs.size() <= numPhysicalIntRegs);
    // assert(freeFloatRegs.size() <= numPhysicalFloatRegs);
}


#endif // __CPU_O3_FREE_LIST_HH__