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/*
* Copyright (c) 2014-2015 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:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. 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.
*
* 3. Neither the name of the copyright holder 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 HOLDER 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 __GLOBAL_MEMORY_PIPELINE_HH__
#define __GLOBAL_MEMORY_PIPELINE_HH__
#include <queue>
#include <string>
#include "base/statistics.hh"
#include "base/stats/group.hh"
#include "gpu-compute/misc.hh"
#include "params/ComputeUnit.hh"
#include "sim/stats.hh"
/*
* @file global_memory_pipeline.hh
*
* The global memory pipeline issues newly created global memory packets
* from the pipeline to DTLB. The exec() method of the memory packet issues
* the packet to the DTLB if there is space available in the return fifo.
* This stage also retires previously issued loads and stores that have
* returned from the memory sub-system.
*/
namespace gem5
{
class ComputeUnit;
class GlobalMemPipeline
{
public:
GlobalMemPipeline(const ComputeUnitParams &p, ComputeUnit &cu);
void init();
void exec();
/**
* Find the next ready response to service. In order to ensure
* that no waitcnts are violated, we pop the oldest (in program order)
* response, and only if it is marked as done. This is because waitcnt
* values expect memory operations to complete and decrement their
* counter values in program order.
*/
GPUDynInstPtr getNextReadyResp();
/**
* once a memory request is finished we remove it from the
* buffer.
*/
void completeRequest(GPUDynInstPtr gpuDynInst);
/**
* Issues a request to the pipeline (i.e., enqueue it
* in the request buffer).
*/
void issueRequest(GPUDynInstPtr gpuDynInst);
/**
* This method handles responses sent to this GM pipeline by the
* CU. Simply marks the reqeust as done in the ordered buffer to
* indicate that the requst is finished.
*/
void handleResponse(GPUDynInstPtr gpuDynInst);
bool
isGMReqFIFOWrRdy(uint32_t pendReqs=0) const
{
return (gmIssuedRequests.size() + pendReqs) < gmQueueSize;
}
const std::string &name() const { return _name; }
void
incLoadVRFBankConflictCycles(int num_cycles)
{
stats.loadVrfBankConflictCycles += num_cycles;
}
bool coalescerReady(GPUDynInstPtr mp) const;
bool outstandingReqsCheck(GPUDynInstPtr mp) const;
void acqCoalescerToken(GPUDynInstPtr mp);
private:
ComputeUnit &computeUnit;
const std::string _name;
int gmQueueSize;
int maxWaveRequests;
// Counters to track the inflight loads and stores
// so that we can provide the proper backpressure
// on the number of inflight memory operations.
int inflightStores;
int inflightLoads;
// The size of global memory.
int globalMemSize;
/*
* This buffer holds the memory responses in order data - the responses
* are ordered by their unique sequence number, which is monotonically
* increasing. When a memory request returns its "done" flag is set to
* true. During each tick the the GM pipeline will check if the oldest
* request is finished, and if so it will be removed from the queue.
*
* key: memory instruction's sequence ID
*
* value: pair holding the instruction pointer and a bool that
* is used to indicate whether or not the request has
* completed
*/
std::map<uint64_t, std::pair<GPUDynInstPtr, bool>> gmOrderedRespBuffer;
// Global Memory Request FIFO: all global memory requests
// are issued to this FIFO from the memory pipelines
std::queue<GPUDynInstPtr> gmIssuedRequests;
protected:
struct GlobalMemPipelineStats : public statistics::Group
{
GlobalMemPipelineStats(statistics::Group *parent);
// number of cycles of delaying the update of a VGPR that is the
// target of a load instruction (or the load component of an atomic)
// The delay is due to VRF bank conflicts
statistics::Scalar loadVrfBankConflictCycles;
} stats;
};
} // namespace gem5
#endif // __GLOBAL_MEMORY_PIPELINE_HH__