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/*
* Copyright (c) 2013-2014 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.
*
* 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.
*
* Authors: Andrew Bardsley
*/
/**
* @file
*
* A simple instruction scoreboard for tracking dependencies in Execute.
*/
#ifndef __CPU_MINOR_SCOREBOARD_HH__
#define __CPU_MINOR_SCOREBOARD_HH__
#include "cpu/minor/cpu.hh"
#include "cpu/minor/dyn_inst.hh"
#include "cpu/minor/trace.hh"
namespace Minor
{
/** A scoreboard of register dependencies including, for each register:
* The number of in-flight instructions which will generate a result for
* this register */
class Scoreboard : public Named
{
public:
/** The number of registers in the Scoreboard. These
* are just the integer, CC and float registers packed
* together with integer regs in the range [0,NumIntRegs-1],
* CC regs in the range [NumIntRegs, NumIntRegs+NumCCRegs-1]
* and float regs in the range
* [NumIntRegs+NumCCRegs, NumFloatRegs+NumIntRegs+NumCCRegs-1] */
const unsigned numRegs;
/** Type to use when indexing numResults */
typedef unsigned short int Index;
/** Count of the number of in-flight instructions that
* have results for each register */
std::vector<Index> numResults;
/** Count of the number of results which can't be predicted */
std::vector<Index> numUnpredictableResults;
/** Index of the FU generating this result */
std::vector<int> fuIndices;
/** The estimated cycle number that the result will be presented.
* This can be offset from to allow forwarding to be simulated as
* long as instruction completion is *strictly* in order with
* respect to instructions with unpredictable result timing */
std::vector<Cycles> returnCycle;
/** The execute sequence number of the most recent inst to generate this
* register value */
std::vector<InstSeqNum> writingInst;
public:
Scoreboard(const std::string &name) :
Named(name),
numRegs(TheISA::NumIntRegs + TheISA::NumCCRegs +
TheISA::NumFloatRegs),
numResults(numRegs, 0),
numUnpredictableResults(numRegs, 0),
fuIndices(numRegs, 0),
returnCycle(numRegs, Cycles(0)),
writingInst(numRegs, 0)
{ }
public:
/** Sets scoreboard_index to the index into numResults of the
* given register index. Returns true if the given register
* is in the scoreboard and false if it isn't */
bool findIndex(const RegId& reg, Index &scoreboard_index);
/** Mark up an instruction's effects by incrementing
* numResults counts. If mark_unpredictable is true, the inst's
* destination registers are marked as being unpredictable without
* an estimated retire time */
void markupInstDests(MinorDynInstPtr inst, Cycles retire_time,
ThreadContext *thread_context, bool mark_unpredictable);
/** Clear down the dependencies for this instruction. clear_unpredictable
* must match mark_unpredictable for the same inst. */
void clearInstDests(MinorDynInstPtr inst, bool clear_unpredictable);
/** Returns the exec sequence number of the most recent inst on
* which the given inst depends. Useful for determining which
* inst must actually be committed before a dependent inst
* can call initiateAcc */
InstSeqNum execSeqNumToWaitFor(MinorDynInstPtr inst,
ThreadContext *thread_context);
/** Can this instruction be issued. Are any of its source registers
* due to be written by other marked-up instructions in flight */
bool canInstIssue(MinorDynInstPtr inst,
const std::vector<Cycles> *src_reg_relative_latencies,
const std::vector<bool> *cant_forward_from_fu_indices,
Cycles now, ThreadContext *thread_context);
/** MinorTraceIF interface */
void minorTrace() const;
};
}
#endif /* __CPU_MINOR_SCOREBOARD_HH__ */
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