decode.hh revision 2733
112837Sgabeblack@google.com/* 212837Sgabeblack@google.com * Copyright (c) 2004-2006 The Regents of The University of Michigan 312837Sgabeblack@google.com * All rights reserved. 412837Sgabeblack@google.com * 512837Sgabeblack@google.com * Redistribution and use in source and binary forms, with or without 612837Sgabeblack@google.com * modification, are permitted provided that the following conditions are 712837Sgabeblack@google.com * met: redistributions of source code must retain the above copyright 812837Sgabeblack@google.com * notice, this list of conditions and the following disclaimer; 912837Sgabeblack@google.com * redistributions in binary form must reproduce the above copyright 1012837Sgabeblack@google.com * notice, this list of conditions and the following disclaimer in the 1112837Sgabeblack@google.com * documentation and/or other materials provided with the distribution; 1212837Sgabeblack@google.com * neither the name of the copyright holders nor the names of its 1312837Sgabeblack@google.com * contributors may be used to endorse or promote products derived from 1412837Sgabeblack@google.com * this software without specific prior written permission. 1512837Sgabeblack@google.com * 1612837Sgabeblack@google.com * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 1712837Sgabeblack@google.com * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 1812837Sgabeblack@google.com * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 1912837Sgabeblack@google.com * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 2012837Sgabeblack@google.com * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 2112837Sgabeblack@google.com * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 2212837Sgabeblack@google.com * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2312837Sgabeblack@google.com * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2412837Sgabeblack@google.com * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 2512837Sgabeblack@google.com * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 2612837Sgabeblack@google.com * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 2712837Sgabeblack@google.com * 2812837Sgabeblack@google.com * Authors: Kevin Lim 2912837Sgabeblack@google.com */ 3012837Sgabeblack@google.com 3113081Sgabeblack@google.com#ifndef __CPU_O3_DECODE_HH__ 3212837Sgabeblack@google.com#define __CPU_O3_DECODE_HH__ 3312862Sgabeblack@google.com 3412837Sgabeblack@google.com#include <queue> 3512862Sgabeblack@google.com 3612956Sgabeblack@google.com#include "base/statistics.hh" 3712862Sgabeblack@google.com#include "base/timebuf.hh" 3812837Sgabeblack@google.com 3912982Sgabeblack@google.com/** 4013038Sgabeblack@google.com * DefaultDecode class handles both single threaded and SMT 4112956Sgabeblack@google.com * decode. Its width is specified by the parameters; each cycles it 4212837Sgabeblack@google.com * tries to decode that many instructions. Because instructions are 4312861Sgabeblack@google.com * actually decoded when the StaticInst is created, this stage does 4412837Sgabeblack@google.com * not do much other than check any PC-relative branches. 4512949Sgabeblack@google.com */ 4612949Sgabeblack@google.comtemplate<class Impl> 4712837Sgabeblack@google.comclass DefaultDecode 4812837Sgabeblack@google.com{ 4912837Sgabeblack@google.com private: 5012837Sgabeblack@google.com // Typedefs from the Impl. 5112837Sgabeblack@google.com typedef typename Impl::O3CPU O3CPU; 5212837Sgabeblack@google.com typedef typename Impl::DynInstPtr DynInstPtr; 5312837Sgabeblack@google.com typedef typename Impl::Params Params; 5412837Sgabeblack@google.com typedef typename Impl::CPUPol CPUPol; 5512837Sgabeblack@google.com 5612837Sgabeblack@google.com // Typedefs from the CPU policy. 5712837Sgabeblack@google.com typedef typename CPUPol::FetchStruct FetchStruct; 5812837Sgabeblack@google.com typedef typename CPUPol::DecodeStruct DecodeStruct; 5912862Sgabeblack@google.com typedef typename CPUPol::TimeStruct TimeStruct; 6012862Sgabeblack@google.com 6113081Sgabeblack@google.com public: 6213081Sgabeblack@google.com /** Overall decode stage status. Used to determine if the CPU can 6313081Sgabeblack@google.com * deschedule itself due to a lack of activity. 6413081Sgabeblack@google.com */ 6513081Sgabeblack@google.com enum DecodeStatus { 6613081Sgabeblack@google.com Active, 6712862Sgabeblack@google.com Inactive 6812862Sgabeblack@google.com }; 6912862Sgabeblack@google.com 7012949Sgabeblack@google.com /** Individual thread status. */ 7113081Sgabeblack@google.com enum ThreadStatus { 7213081Sgabeblack@google.com Running, 7313081Sgabeblack@google.com Idle, 7413081Sgabeblack@google.com StartSquash, 7513081Sgabeblack@google.com Squashing, 7613081Sgabeblack@google.com Blocked, 7713081Sgabeblack@google.com Unblocking 7813081Sgabeblack@google.com }; 7913081Sgabeblack@google.com 8013081Sgabeblack@google.com private: 8113081Sgabeblack@google.com /** Decode status. */ 8213182Sgabeblack@google.com DecodeStatus _status; 8313182Sgabeblack@google.com 8413182Sgabeblack@google.com /** Per-thread status. */ 8513182Sgabeblack@google.com ThreadStatus decodeStatus[Impl::MaxThreads]; 8613081Sgabeblack@google.com 8713077Sgabeblack@google.com public: 8813077Sgabeblack@google.com /** DefaultDecode constructor. */ 8912949Sgabeblack@google.com DefaultDecode(Params *params); 9012949Sgabeblack@google.com 9112949Sgabeblack@google.com /** Returns the name of decode. */ 9212949Sgabeblack@google.com std::string name() const; 9312862Sgabeblack@google.com 9412862Sgabeblack@google.com /** Registers statistics. */ 9512862Sgabeblack@google.com void regStats(); 9612862Sgabeblack@google.com 9712862Sgabeblack@google.com /** Sets CPU pointer. */ 9812837Sgabeblack@google.com void setCPU(O3CPU *cpu_ptr); 9912837Sgabeblack@google.com 10012837Sgabeblack@google.com /** Sets the main backwards communication time buffer pointer. */ 10112837Sgabeblack@google.com void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 10212837Sgabeblack@google.com 10312837Sgabeblack@google.com /** Sets pointer to time buffer used to communicate to the next stage. */ 10412837Sgabeblack@google.com void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr); 10512837Sgabeblack@google.com 10612837Sgabeblack@google.com /** Sets pointer to time buffer coming from fetch. */ 10712837Sgabeblack@google.com void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr); 10812837Sgabeblack@google.com 10912837Sgabeblack@google.com /** Sets pointer to list of active threads. */ 11012837Sgabeblack@google.com void setActiveThreads(std::list<unsigned> *at_ptr); 11112837Sgabeblack@google.com 11212837Sgabeblack@google.com /** Switches out the decode stage. */ 11312837Sgabeblack@google.com void switchOut(); 11412837Sgabeblack@google.com 11512837Sgabeblack@google.com /** Takes over from another CPU's thread. */ 11612837Sgabeblack@google.com void takeOverFrom(); 11712837Sgabeblack@google.com 11812837Sgabeblack@google.com /** Ticks decode, processing all input signals and decoding as many 11912837Sgabeblack@google.com * instructions as possible. 12012837Sgabeblack@google.com */ 12112837Sgabeblack@google.com void tick(); 12212837Sgabeblack@google.com 12312837Sgabeblack@google.com /** Determines what to do based on decode's current status. 12412837Sgabeblack@google.com * @param status_change decode() sets this variable if there was a status 12512837Sgabeblack@google.com * change (ie switching from from blocking to unblocking). 12612837Sgabeblack@google.com * @param tid Thread id to decode instructions from. 12712837Sgabeblack@google.com */ 12812837Sgabeblack@google.com void decode(bool &status_change, unsigned tid); 12912837Sgabeblack@google.com 13012837Sgabeblack@google.com /** Processes instructions from fetch and passes them on to rename. 13112837Sgabeblack@google.com * Decoding of instructions actually happens when they are created in 13212837Sgabeblack@google.com * fetch, so this function mostly checks if PC-relative branches are 13312837Sgabeblack@google.com * correct. 13412837Sgabeblack@google.com */ 13512862Sgabeblack@google.com void decodeInsts(unsigned tid); 13612837Sgabeblack@google.com 13712837Sgabeblack@google.com private: 13813081Sgabeblack@google.com /** Inserts a thread's instructions into the skid buffer, to be decoded 13913081Sgabeblack@google.com * once decode unblocks. 14013081Sgabeblack@google.com */ 14113081Sgabeblack@google.com void skidInsert(unsigned tid); 14213081Sgabeblack@google.com 14313081Sgabeblack@google.com /** Returns if all of the skid buffers are empty. */ 14413081Sgabeblack@google.com bool skidsEmpty(); 14513081Sgabeblack@google.com 14613081Sgabeblack@google.com /** Updates overall decode status based on all of the threads' statuses. */ 14713081Sgabeblack@google.com void updateStatus(); 14813081Sgabeblack@google.com 14913081Sgabeblack@google.com /** Separates instructions from fetch into individual lists of instructions 15012837Sgabeblack@google.com * sorted by thread. 15112837Sgabeblack@google.com */ 15213038Sgabeblack@google.com void sortInsts(); 15313038Sgabeblack@google.com 15412837Sgabeblack@google.com /** Reads all stall signals from the backwards communication timebuffer. */ 15513038Sgabeblack@google.com void readStallSignals(unsigned tid); 15613038Sgabeblack@google.com 15713038Sgabeblack@google.com /** Checks all input signals and updates decode's status appropriately. */ 15813038Sgabeblack@google.com bool checkSignalsAndUpdate(unsigned tid); 15913081Sgabeblack@google.com 16013081Sgabeblack@google.com /** Checks all stall signals, and returns if any are true. */ 16113038Sgabeblack@google.com bool checkStall(unsigned tid) const; 16213038Sgabeblack@google.com 16312837Sgabeblack@google.com /** Returns if there any instructions from fetch on this cycle. */ 16412861Sgabeblack@google.com inline bool fetchInstsValid(); 16512861Sgabeblack@google.com 16612837Sgabeblack@google.com /** Switches decode to blocking, and signals back that decode has 16712837Sgabeblack@google.com * become blocked. 16812837Sgabeblack@google.com * @return Returns true if there is a status change. 16912837Sgabeblack@google.com */ 17012837Sgabeblack@google.com bool block(unsigned tid); 17112837Sgabeblack@google.com 17212837Sgabeblack@google.com /** Switches decode to unblocking if the skid buffer is empty, and 17312837Sgabeblack@google.com * signals back that decode has unblocked. 17412837Sgabeblack@google.com * @return Returns true if there is a status change. 17512837Sgabeblack@google.com */ 17612837Sgabeblack@google.com bool unblock(unsigned tid); 17712837Sgabeblack@google.com 17812837Sgabeblack@google.com /** Squashes if there is a PC-relative branch that was predicted 17912837Sgabeblack@google.com * incorrectly. Sends squash information back to fetch. 18012860Sgabeblack@google.com */ 18112860Sgabeblack@google.com void squash(DynInstPtr &inst, unsigned tid); 18212860Sgabeblack@google.com 18312962Sgabeblack@google.com public: 18412961Sgabeblack@google.com /** Squashes due to commit signalling a squash. Changes status to 18512860Sgabeblack@google.com * squashing and clears block/unblock signals as needed. 18612860Sgabeblack@google.com */ 18712860Sgabeblack@google.com unsigned squash(unsigned tid); 18812860Sgabeblack@google.com 18912860Sgabeblack@google.com private: 19012990Sgabeblack@google.com // Interfaces to objects outside of decode. 19112961Sgabeblack@google.com /** CPU interface. */ 19212860Sgabeblack@google.com O3CPU *cpu; 19312860Sgabeblack@google.com 19412860Sgabeblack@google.com /** Time buffer interface. */ 19512860Sgabeblack@google.com TimeBuffer<TimeStruct> *timeBuffer; 19612860Sgabeblack@google.com 19713061Sgabeblack@google.com /** Wire to get rename's output from backwards time buffer. */ 19813061Sgabeblack@google.com typename TimeBuffer<TimeStruct>::wire fromRename; 19913061Sgabeblack@google.com 20013061Sgabeblack@google.com /** Wire to get iew's information from backwards time buffer. */ 20113084Sgabeblack@google.com typename TimeBuffer<TimeStruct>::wire fromIEW; 20213084Sgabeblack@google.com 20313084Sgabeblack@google.com /** Wire to get commit's information from backwards time buffer. */ 20413084Sgabeblack@google.com typename TimeBuffer<TimeStruct>::wire fromCommit; 20513061Sgabeblack@google.com 20613061Sgabeblack@google.com /** Wire to write information heading to previous stages. */ 20712860Sgabeblack@google.com // Might not be the best name as not only fetch will read it. 20812860Sgabeblack@google.com typename TimeBuffer<TimeStruct>::wire toFetch; 20912860Sgabeblack@google.com 21012860Sgabeblack@google.com /** Decode instruction queue. */ 21112860Sgabeblack@google.com TimeBuffer<DecodeStruct> *decodeQueue; 21212861Sgabeblack@google.com 21312861Sgabeblack@google.com /** Wire used to write any information heading to rename. */ 21412861Sgabeblack@google.com typename TimeBuffer<DecodeStruct>::wire toRename; 21512861Sgabeblack@google.com 21612861Sgabeblack@google.com /** Fetch instruction queue interface. */ 21712861Sgabeblack@google.com TimeBuffer<FetchStruct> *fetchQueue; 21812860Sgabeblack@google.com 21912860Sgabeblack@google.com /** Wire to get fetch's output from fetch queue. */ 22012860Sgabeblack@google.com typename TimeBuffer<FetchStruct>::wire fromFetch; 22112860Sgabeblack@google.com 22212860Sgabeblack@google.com /** Queue of all instructions coming from fetch this cycle. */ 22312861Sgabeblack@google.com std::queue<DynInstPtr> insts[Impl::MaxThreads]; 22412860Sgabeblack@google.com 22512860Sgabeblack@google.com /** Skid buffer between fetch and decode. */ 22612860Sgabeblack@google.com std::queue<DynInstPtr> skidBuffer[Impl::MaxThreads]; 22712860Sgabeblack@google.com 22812860Sgabeblack@google.com /** Variable that tracks if decode has written to the time buffer this 22913212Sgabeblack@google.com * cycle. Used to tell CPU if there is activity this cycle. 23013212Sgabeblack@google.com */ 23113212Sgabeblack@google.com bool wroteToTimeBuffer; 23213212Sgabeblack@google.com 23313212Sgabeblack@google.com /** Source of possible stalls. */ 23413212Sgabeblack@google.com struct Stalls { 23513212Sgabeblack@google.com bool rename; 23613212Sgabeblack@google.com bool iew; 23713212Sgabeblack@google.com bool commit; 23813212Sgabeblack@google.com }; 23912990Sgabeblack@google.com 24012961Sgabeblack@google.com /** Tracks which stages are telling decode to stall. */ 24112961Sgabeblack@google.com Stalls stalls[Impl::MaxThreads]; 24213097Sgabeblack@google.com 24312961Sgabeblack@google.com /** Rename to decode delay, in ticks. */ 24412961Sgabeblack@google.com unsigned renameToDecodeDelay; 24512961Sgabeblack@google.com 24612990Sgabeblack@google.com /** IEW to decode delay, in ticks. */ 24712961Sgabeblack@google.com unsigned iewToDecodeDelay; 24812860Sgabeblack@google.com 24912860Sgabeblack@google.com /** Commit to decode delay, in ticks. */ 25012860Sgabeblack@google.com unsigned commitToDecodeDelay; 25112860Sgabeblack@google.com 25212860Sgabeblack@google.com /** Fetch to decode delay, in ticks. */ 25313255Sgabeblack@google.com unsigned fetchToDecodeDelay; 25413255Sgabeblack@google.com 25512956Sgabeblack@google.com /** The width of decode, in instructions. */ 25612860Sgabeblack@google.com unsigned decodeWidth; 25712860Sgabeblack@google.com 25812860Sgabeblack@google.com /** Index of instructions being sent to rename. */ 25912860Sgabeblack@google.com unsigned toRenameIndex; 26012860Sgabeblack@google.com 26112956Sgabeblack@google.com /** number of Active Threads*/ 26212860Sgabeblack@google.com unsigned numThreads; 26312860Sgabeblack@google.com 26412860Sgabeblack@google.com /** List of active thread ids */ 26512860Sgabeblack@google.com std::list<unsigned> *activeThreads; 26612860Sgabeblack@google.com 26712982Sgabeblack@google.com /** Number of branches in flight. */ 26812860Sgabeblack@google.com unsigned branchCount[Impl::MaxThreads]; 26912860Sgabeblack@google.com 27012860Sgabeblack@google.com /** Maximum size of the skid buffer. */ 27112860Sgabeblack@google.com unsigned skidBufferMax; 27212860Sgabeblack@google.com 27312962Sgabeblack@google.com /** Stat for total number of idle cycles. */ 27412860Sgabeblack@google.com Stats::Scalar<> decodeIdleCycles; 27512860Sgabeblack@google.com /** Stat for total number of blocked cycles. */ 27612860Sgabeblack@google.com Stats::Scalar<> decodeBlockedCycles; 27712860Sgabeblack@google.com /** Stat for total number of normal running cycles. */ 27812860Sgabeblack@google.com Stats::Scalar<> decodeRunCycles; 27912962Sgabeblack@google.com /** Stat for total number of unblocking cycles. */ 28012860Sgabeblack@google.com Stats::Scalar<> decodeUnblockCycles; 28112860Sgabeblack@google.com /** Stat for total number of squashing cycles. */ 28212860Sgabeblack@google.com Stats::Scalar<> decodeSquashCycles; 28312860Sgabeblack@google.com /** Stat for number of times a branch is resolved at decode. */ 28412860Sgabeblack@google.com Stats::Scalar<> decodeBranchResolved; 28512861Sgabeblack@google.com /** Stat for number of times a branch mispredict is detected. */ 28612861Sgabeblack@google.com Stats::Scalar<> decodeBranchMispred; 28712860Sgabeblack@google.com /** Stat for number of times decode detected a non-control instruction 28812860Sgabeblack@google.com * incorrectly predicted as a branch. 28912860Sgabeblack@google.com */ 29012860Sgabeblack@google.com Stats::Scalar<> decodeControlMispred; 29112860Sgabeblack@google.com /** Stat for total number of decoded instructions. */ 29212962Sgabeblack@google.com Stats::Scalar<> decodeDecodedInsts; 29312860Sgabeblack@google.com /** Stat for total number of squashed instructions. */ 29412860Sgabeblack@google.com Stats::Scalar<> decodeSquashedInsts; 29512860Sgabeblack@google.com}; 29612860Sgabeblack@google.com 29712860Sgabeblack@google.com#endif // __CPU_O3_DECODE_HH__ 29812982Sgabeblack@google.com