728 lines
24 KiB
C++
728 lines
24 KiB
C++
/*
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* Copyright (c) 2004-2006 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Authors: Kevin Lim
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* Korey Sewell
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*/
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#ifndef __CPU_O3_LSQ_UNIT_HH__
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#define __CPU_O3_LSQ_UNIT_HH__
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#include <algorithm>
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#include <cstring>
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#include <map>
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#include <queue>
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#include "arch/faults.hh"
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#include "arch/locked_mem.hh"
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#include "config/full_system.hh"
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#include "config/the_isa.hh"
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#include "base/fast_alloc.hh"
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#include "base/hashmap.hh"
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#include "cpu/inst_seq.hh"
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#include "mem/packet.hh"
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#include "mem/port.hh"
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class DerivO3CPUParams;
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/**
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* Class that implements the actual LQ and SQ for each specific
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* thread. Both are circular queues; load entries are freed upon
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* committing, while store entries are freed once they writeback. The
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* LSQUnit tracks if there are memory ordering violations, and also
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* detects partial load to store forwarding cases (a store only has
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* part of a load's data) that requires the load to wait until the
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* store writes back. In the former case it holds onto the instruction
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* until the dependence unit looks at it, and in the latter it stalls
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* the LSQ until the store writes back. At that point the load is
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* replayed.
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*/
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template <class Impl>
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class LSQUnit {
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protected:
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typedef TheISA::IntReg IntReg;
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public:
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typedef typename Impl::O3CPU O3CPU;
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typedef typename Impl::DynInstPtr DynInstPtr;
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typedef typename Impl::CPUPol::IEW IEW;
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typedef typename Impl::CPUPol::LSQ LSQ;
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typedef typename Impl::CPUPol::IssueStruct IssueStruct;
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public:
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/** Constructs an LSQ unit. init() must be called prior to use. */
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LSQUnit();
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/** Initializes the LSQ unit with the specified number of entries. */
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void init(O3CPU *cpu_ptr, IEW *iew_ptr, DerivO3CPUParams *params,
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LSQ *lsq_ptr, unsigned maxLQEntries, unsigned maxSQEntries,
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unsigned id);
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/** Returns the name of the LSQ unit. */
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std::string name() const;
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/** Registers statistics. */
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void regStats();
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/** Sets the pointer to the dcache port. */
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void setDcachePort(Port *dcache_port);
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/** Switches out LSQ unit. */
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void switchOut();
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/** Takes over from another CPU's thread. */
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void takeOverFrom();
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/** Returns if the LSQ is switched out. */
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bool isSwitchedOut() { return switchedOut; }
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/** Ticks the LSQ unit, which in this case only resets the number of
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* used cache ports.
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* @todo: Move the number of used ports up to the LSQ level so it can
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* be shared by all LSQ units.
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*/
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void tick() { usedPorts = 0; }
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/** Inserts an instruction. */
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void insert(DynInstPtr &inst);
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/** Inserts a load instruction. */
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void insertLoad(DynInstPtr &load_inst);
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/** Inserts a store instruction. */
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void insertStore(DynInstPtr &store_inst);
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/** Executes a load instruction. */
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Fault executeLoad(DynInstPtr &inst);
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Fault executeLoad(int lq_idx) { panic("Not implemented"); return NoFault; }
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/** Executes a store instruction. */
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Fault executeStore(DynInstPtr &inst);
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/** Commits the head load. */
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void commitLoad();
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/** Commits loads older than a specific sequence number. */
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void commitLoads(InstSeqNum &youngest_inst);
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/** Commits stores older than a specific sequence number. */
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void commitStores(InstSeqNum &youngest_inst);
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/** Writes back stores. */
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void writebackStores();
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/** Completes the data access that has been returned from the
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* memory system. */
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void completeDataAccess(PacketPtr pkt);
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/** Clears all the entries in the LQ. */
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void clearLQ();
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/** Clears all the entries in the SQ. */
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void clearSQ();
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/** Resizes the LQ to a given size. */
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void resizeLQ(unsigned size);
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/** Resizes the SQ to a given size. */
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void resizeSQ(unsigned size);
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/** Squashes all instructions younger than a specific sequence number. */
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void squash(const InstSeqNum &squashed_num);
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/** Returns if there is a memory ordering violation. Value is reset upon
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* call to getMemDepViolator().
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*/
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bool violation() { return memDepViolator; }
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/** Returns the memory ordering violator. */
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DynInstPtr getMemDepViolator();
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/** Returns if a load became blocked due to the memory system. */
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bool loadBlocked()
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{ return isLoadBlocked; }
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/** Clears the signal that a load became blocked. */
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void clearLoadBlocked()
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{ isLoadBlocked = false; }
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/** Returns if the blocked load was handled. */
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bool isLoadBlockedHandled()
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{ return loadBlockedHandled; }
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/** Records the blocked load as being handled. */
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void setLoadBlockedHandled()
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{ loadBlockedHandled = true; }
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/** Returns the number of free entries (min of free LQ and SQ entries). */
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unsigned numFreeEntries();
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/** Returns the number of loads ready to execute. */
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int numLoadsReady();
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/** Returns the number of loads in the LQ. */
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int numLoads() { return loads; }
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/** Returns the number of stores in the SQ. */
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int numStores() { return stores; }
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/** Returns if either the LQ or SQ is full. */
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bool isFull() { return lqFull() || sqFull(); }
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/** Returns if the LQ is full. */
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bool lqFull() { return loads >= (LQEntries - 1); }
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/** Returns if the SQ is full. */
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bool sqFull() { return stores >= (SQEntries - 1); }
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/** Returns the number of instructions in the LSQ. */
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unsigned getCount() { return loads + stores; }
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/** Returns if there are any stores to writeback. */
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bool hasStoresToWB() { return storesToWB; }
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/** Returns the number of stores to writeback. */
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int numStoresToWB() { return storesToWB; }
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/** Returns if the LSQ unit will writeback on this cycle. */
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bool willWB() { return storeQueue[storeWBIdx].canWB &&
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!storeQueue[storeWBIdx].completed &&
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!isStoreBlocked; }
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/** Handles doing the retry. */
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void recvRetry();
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private:
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/** Writes back the instruction, sending it to IEW. */
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void writeback(DynInstPtr &inst, PacketPtr pkt);
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/** Handles completing the send of a store to memory. */
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void storePostSend(PacketPtr pkt);
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/** Completes the store at the specified index. */
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void completeStore(int store_idx);
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/** Increments the given store index (circular queue). */
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inline void incrStIdx(int &store_idx);
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/** Decrements the given store index (circular queue). */
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inline void decrStIdx(int &store_idx);
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/** Increments the given load index (circular queue). */
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inline void incrLdIdx(int &load_idx);
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/** Decrements the given load index (circular queue). */
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inline void decrLdIdx(int &load_idx);
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public:
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/** Debugging function to dump instructions in the LSQ. */
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void dumpInsts();
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private:
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/** Pointer to the CPU. */
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O3CPU *cpu;
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/** Pointer to the IEW stage. */
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IEW *iewStage;
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/** Pointer to the LSQ. */
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LSQ *lsq;
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/** Pointer to the dcache port. Used only for sending. */
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Port *dcachePort;
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/** Derived class to hold any sender state the LSQ needs. */
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class LSQSenderState : public Packet::SenderState, public FastAlloc
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{
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public:
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/** Default constructor. */
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LSQSenderState()
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: noWB(false)
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{ }
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/** Instruction who initiated the access to memory. */
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DynInstPtr inst;
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/** Whether or not it is a load. */
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bool isLoad;
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/** The LQ/SQ index of the instruction. */
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int idx;
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/** Whether or not the instruction will need to writeback. */
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bool noWB;
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};
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/** Writeback event, specifically for when stores forward data to loads. */
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class WritebackEvent : public Event {
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public:
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/** Constructs a writeback event. */
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WritebackEvent(DynInstPtr &_inst, PacketPtr pkt, LSQUnit *lsq_ptr);
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/** Processes the writeback event. */
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void process();
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/** Returns the description of this event. */
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const char *description() const;
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private:
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/** Instruction whose results are being written back. */
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DynInstPtr inst;
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/** The packet that would have been sent to memory. */
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PacketPtr pkt;
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/** The pointer to the LSQ unit that issued the store. */
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LSQUnit<Impl> *lsqPtr;
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};
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public:
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struct SQEntry {
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/** Constructs an empty store queue entry. */
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SQEntry()
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: inst(NULL), req(NULL), size(0),
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canWB(0), committed(0), completed(0)
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{
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std::memset(data, 0, sizeof(data));
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}
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/** Constructs a store queue entry for a given instruction. */
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SQEntry(DynInstPtr &_inst)
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: inst(_inst), req(NULL), size(0),
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canWB(0), committed(0), completed(0)
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{
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std::memset(data, 0, sizeof(data));
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}
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/** The store instruction. */
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DynInstPtr inst;
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/** The request for the store. */
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RequestPtr req;
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/** The size of the store. */
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int size;
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/** The store data. */
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char data[sizeof(IntReg)];
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/** Whether or not the store can writeback. */
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bool canWB;
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/** Whether or not the store is committed. */
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bool committed;
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/** Whether or not the store is completed. */
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bool completed;
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};
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private:
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/** The LSQUnit thread id. */
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ThreadID lsqID;
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/** The store queue. */
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std::vector<SQEntry> storeQueue;
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/** The load queue. */
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std::vector<DynInstPtr> loadQueue;
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/** The number of LQ entries, plus a sentinel entry (circular queue).
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* @todo: Consider having var that records the true number of LQ entries.
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*/
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unsigned LQEntries;
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/** The number of SQ entries, plus a sentinel entry (circular queue).
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* @todo: Consider having var that records the true number of SQ entries.
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*/
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unsigned SQEntries;
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/** The number of load instructions in the LQ. */
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int loads;
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/** The number of store instructions in the SQ. */
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int stores;
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/** The number of store instructions in the SQ waiting to writeback. */
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int storesToWB;
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/** The index of the head instruction in the LQ. */
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int loadHead;
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/** The index of the tail instruction in the LQ. */
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int loadTail;
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/** The index of the head instruction in the SQ. */
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int storeHead;
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/** The index of the first instruction that may be ready to be
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* written back, and has not yet been written back.
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*/
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int storeWBIdx;
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/** The index of the tail instruction in the SQ. */
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int storeTail;
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/// @todo Consider moving to a more advanced model with write vs read ports
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/** The number of cache ports available each cycle. */
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int cachePorts;
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/** The number of used cache ports in this cycle. */
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int usedPorts;
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/** Is the LSQ switched out. */
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bool switchedOut;
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//list<InstSeqNum> mshrSeqNums;
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/** Wire to read information from the issue stage time queue. */
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typename TimeBuffer<IssueStruct>::wire fromIssue;
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/** Whether or not the LSQ is stalled. */
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bool stalled;
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/** The store that causes the stall due to partial store to load
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* forwarding.
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*/
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InstSeqNum stallingStoreIsn;
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/** The index of the above store. */
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int stallingLoadIdx;
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/** The packet that needs to be retried. */
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PacketPtr retryPkt;
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/** Whehter or not a store is blocked due to the memory system. */
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bool isStoreBlocked;
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/** Whether or not a load is blocked due to the memory system. */
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bool isLoadBlocked;
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/** Has the blocked load been handled. */
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bool loadBlockedHandled;
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/** The sequence number of the blocked load. */
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InstSeqNum blockedLoadSeqNum;
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/** The oldest load that caused a memory ordering violation. */
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DynInstPtr memDepViolator;
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// Will also need how many read/write ports the Dcache has. Or keep track
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// of that in stage that is one level up, and only call executeLoad/Store
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// the appropriate number of times.
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/** Total number of loads forwaded from LSQ stores. */
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Stats::Scalar lsqForwLoads;
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/** Total number of loads ignored due to invalid addresses. */
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Stats::Scalar invAddrLoads;
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/** Total number of squashed loads. */
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Stats::Scalar lsqSquashedLoads;
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/** Total number of responses from the memory system that are
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* ignored due to the instruction already being squashed. */
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Stats::Scalar lsqIgnoredResponses;
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/** Tota number of memory ordering violations. */
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Stats::Scalar lsqMemOrderViolation;
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/** Total number of squashed stores. */
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Stats::Scalar lsqSquashedStores;
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/** Total number of software prefetches ignored due to invalid addresses. */
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Stats::Scalar invAddrSwpfs;
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/** Ready loads blocked due to partial store-forwarding. */
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Stats::Scalar lsqBlockedLoads;
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/** Number of loads that were rescheduled. */
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Stats::Scalar lsqRescheduledLoads;
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/** Number of times the LSQ is blocked due to the cache. */
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Stats::Scalar lsqCacheBlocked;
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public:
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/** Executes the load at the given index. */
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template <class T>
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Fault read(Request *req, T &data, int load_idx);
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/** Executes the store at the given index. */
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template <class T>
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Fault write(Request *req, T &data, int store_idx);
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/** Returns the index of the head load instruction. */
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int getLoadHead() { return loadHead; }
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/** Returns the sequence number of the head load instruction. */
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InstSeqNum getLoadHeadSeqNum()
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{
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if (loadQueue[loadHead]) {
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return loadQueue[loadHead]->seqNum;
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} else {
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return 0;
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}
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}
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/** Returns the index of the head store instruction. */
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int getStoreHead() { return storeHead; }
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/** Returns the sequence number of the head store instruction. */
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InstSeqNum getStoreHeadSeqNum()
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{
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if (storeQueue[storeHead].inst) {
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return storeQueue[storeHead].inst->seqNum;
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} else {
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return 0;
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}
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}
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/** Returns whether or not the LSQ unit is stalled. */
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bool isStalled() { return stalled; }
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};
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template <class Impl>
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template <class T>
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Fault
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LSQUnit<Impl>::read(Request *req, T &data, int load_idx)
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{
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DynInstPtr load_inst = loadQueue[load_idx];
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assert(load_inst);
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assert(!load_inst->isExecuted());
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// Make sure this isn't an uncacheable access
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// A bit of a hackish way to get uncached accesses to work only if they're
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// at the head of the LSQ and are ready to commit (at the head of the ROB
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// too).
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if (req->isUncacheable() &&
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(load_idx != loadHead || !load_inst->isAtCommit())) {
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iewStage->rescheduleMemInst(load_inst);
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++lsqRescheduledLoads;
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// Must delete request now that it wasn't handed off to
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// memory. This is quite ugly. @todo: Figure out the proper
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// place to really handle request deletes.
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delete req;
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return TheISA::genMachineCheckFault();
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}
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// Check the SQ for any previous stores that might lead to forwarding
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int store_idx = load_inst->sqIdx;
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int store_size = 0;
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DPRINTF(LSQUnit, "Read called, load idx: %i, store idx: %i, "
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"storeHead: %i addr: %#x\n",
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load_idx, store_idx, storeHead, req->getPaddr());
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if (req->isLLSC()) {
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// Disable recording the result temporarily. Writing to misc
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// regs normally updates the result, but this is not the
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// desired behavior when handling store conditionals.
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load_inst->recordResult = false;
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TheISA::handleLockedRead(load_inst.get(), req);
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load_inst->recordResult = true;
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}
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while (store_idx != -1) {
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// End once we've reached the top of the LSQ
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if (store_idx == storeWBIdx) {
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break;
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}
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// Move the index to one younger
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if (--store_idx < 0)
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store_idx += SQEntries;
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assert(storeQueue[store_idx].inst);
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store_size = storeQueue[store_idx].size;
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if (store_size == 0)
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continue;
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else if (storeQueue[store_idx].inst->uncacheable())
|
|
continue;
|
|
|
|
assert(storeQueue[store_idx].inst->effAddrValid);
|
|
|
|
// Check if the store data is within the lower and upper bounds of
|
|
// addresses that the request needs.
|
|
bool store_has_lower_limit =
|
|
req->getVaddr() >= storeQueue[store_idx].inst->effAddr;
|
|
bool store_has_upper_limit =
|
|
(req->getVaddr() + req->getSize()) <=
|
|
(storeQueue[store_idx].inst->effAddr + store_size);
|
|
bool lower_load_has_store_part =
|
|
req->getVaddr() < (storeQueue[store_idx].inst->effAddr +
|
|
store_size);
|
|
bool upper_load_has_store_part =
|
|
(req->getVaddr() + req->getSize()) >
|
|
storeQueue[store_idx].inst->effAddr;
|
|
|
|
// If the store's data has all of the data needed, we can forward.
|
|
if ((store_has_lower_limit && store_has_upper_limit)) {
|
|
// Get shift amount for offset into the store's data.
|
|
int shift_amt = req->getVaddr() & (store_size - 1);
|
|
|
|
memcpy(&data, storeQueue[store_idx].data + shift_amt, sizeof(T));
|
|
|
|
assert(!load_inst->memData);
|
|
load_inst->memData = new uint8_t[64];
|
|
|
|
memcpy(load_inst->memData,
|
|
storeQueue[store_idx].data + shift_amt, req->getSize());
|
|
|
|
DPRINTF(LSQUnit, "Forwarding from store idx %i to load to "
|
|
"addr %#x, data %#x\n",
|
|
store_idx, req->getVaddr(), data);
|
|
|
|
PacketPtr data_pkt = new Packet(req, MemCmd::ReadReq,
|
|
Packet::Broadcast);
|
|
data_pkt->dataStatic(load_inst->memData);
|
|
|
|
WritebackEvent *wb = new WritebackEvent(load_inst, data_pkt, this);
|
|
|
|
// We'll say this has a 1 cycle load-store forwarding latency
|
|
// for now.
|
|
// @todo: Need to make this a parameter.
|
|
cpu->schedule(wb, curTick);
|
|
|
|
++lsqForwLoads;
|
|
return NoFault;
|
|
} else if ((store_has_lower_limit && lower_load_has_store_part) ||
|
|
(store_has_upper_limit && upper_load_has_store_part) ||
|
|
(lower_load_has_store_part && upper_load_has_store_part)) {
|
|
// This is the partial store-load forwarding case where a store
|
|
// has only part of the load's data.
|
|
|
|
// If it's already been written back, then don't worry about
|
|
// stalling on it.
|
|
if (storeQueue[store_idx].completed) {
|
|
panic("Should not check one of these");
|
|
continue;
|
|
}
|
|
|
|
// Must stall load and force it to retry, so long as it's the oldest
|
|
// load that needs to do so.
|
|
if (!stalled ||
|
|
(stalled &&
|
|
load_inst->seqNum <
|
|
loadQueue[stallingLoadIdx]->seqNum)) {
|
|
stalled = true;
|
|
stallingStoreIsn = storeQueue[store_idx].inst->seqNum;
|
|
stallingLoadIdx = load_idx;
|
|
}
|
|
|
|
// Tell IQ/mem dep unit that this instruction will need to be
|
|
// rescheduled eventually
|
|
iewStage->rescheduleMemInst(load_inst);
|
|
iewStage->decrWb(load_inst->seqNum);
|
|
load_inst->clearIssued();
|
|
++lsqRescheduledLoads;
|
|
|
|
// Do not generate a writeback event as this instruction is not
|
|
// complete.
|
|
DPRINTF(LSQUnit, "Load-store forwarding mis-match. "
|
|
"Store idx %i to load addr %#x\n",
|
|
store_idx, req->getVaddr());
|
|
|
|
// Must delete request now that it wasn't handed off to
|
|
// memory. This is quite ugly. @todo: Figure out the
|
|
// proper place to really handle request deletes.
|
|
delete req;
|
|
|
|
return NoFault;
|
|
}
|
|
}
|
|
|
|
// If there's no forwarding case, then go access memory
|
|
DPRINTF(LSQUnit, "Doing memory access for inst [sn:%lli] PC %#x\n",
|
|
load_inst->seqNum, load_inst->readPC());
|
|
|
|
assert(!load_inst->memData);
|
|
load_inst->memData = new uint8_t[64];
|
|
|
|
++usedPorts;
|
|
|
|
// if we the cache is not blocked, do cache access
|
|
if (!lsq->cacheBlocked()) {
|
|
PacketPtr data_pkt =
|
|
new Packet(req,
|
|
(req->isLLSC() ?
|
|
MemCmd::LoadLockedReq : MemCmd::ReadReq),
|
|
Packet::Broadcast);
|
|
data_pkt->dataStatic(load_inst->memData);
|
|
|
|
LSQSenderState *state = new LSQSenderState;
|
|
state->isLoad = true;
|
|
state->idx = load_idx;
|
|
state->inst = load_inst;
|
|
data_pkt->senderState = state;
|
|
|
|
if (!dcachePort->sendTiming(data_pkt)) {
|
|
// Delete state and data packet because a load retry
|
|
// initiates a pipeline restart; it does not retry.
|
|
delete state;
|
|
delete data_pkt->req;
|
|
delete data_pkt;
|
|
|
|
req = NULL;
|
|
|
|
// If the access didn't succeed, tell the LSQ by setting
|
|
// the retry thread id.
|
|
lsq->setRetryTid(lsqID);
|
|
}
|
|
}
|
|
|
|
// If the cache was blocked, or has become blocked due to the access,
|
|
// handle it.
|
|
if (lsq->cacheBlocked()) {
|
|
if (req)
|
|
delete req;
|
|
|
|
++lsqCacheBlocked;
|
|
|
|
iewStage->decrWb(load_inst->seqNum);
|
|
// There's an older load that's already going to squash.
|
|
if (isLoadBlocked && blockedLoadSeqNum < load_inst->seqNum)
|
|
return NoFault;
|
|
|
|
// Record that the load was blocked due to memory. This
|
|
// load will squash all instructions after it, be
|
|
// refetched, and re-executed.
|
|
isLoadBlocked = true;
|
|
loadBlockedHandled = false;
|
|
blockedLoadSeqNum = load_inst->seqNum;
|
|
// No fault occurred, even though the interface is blocked.
|
|
return NoFault;
|
|
}
|
|
|
|
return NoFault;
|
|
}
|
|
|
|
template <class Impl>
|
|
template <class T>
|
|
Fault
|
|
LSQUnit<Impl>::write(Request *req, T &data, int store_idx)
|
|
{
|
|
assert(storeQueue[store_idx].inst);
|
|
|
|
DPRINTF(LSQUnit, "Doing write to store idx %i, addr %#x data %#x"
|
|
" | storeHead:%i [sn:%i]\n",
|
|
store_idx, req->getPaddr(), data, storeHead,
|
|
storeQueue[store_idx].inst->seqNum);
|
|
|
|
storeQueue[store_idx].req = req;
|
|
storeQueue[store_idx].size = sizeof(T);
|
|
assert(sizeof(T) <= sizeof(storeQueue[store_idx].data));
|
|
|
|
T gData = htog(data);
|
|
memcpy(storeQueue[store_idx].data, &gData, sizeof(T));
|
|
|
|
// This function only writes the data to the store queue, so no fault
|
|
// can happen here.
|
|
return NoFault;
|
|
}
|
|
|
|
#endif // __CPU_O3_LSQ_UNIT_HH__
|