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gem5/src/cpu/o3/commit_impl.hh

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/*
* Copyright (c) 2010 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.
*
* Copyright (c) 2004-2006 The Regents of The University of Michigan
* All rights reserved.
*
* 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: Kevin Lim
* Korey Sewell
*/
#include <algorithm>
#include <string>
#include "arch/utility.hh"
#include "base/loader/symtab.hh"
#include "base/cp_annotate.hh"
#include "config/full_system.hh"
#include "config/the_isa.hh"
#include "config/use_checker.hh"
#include "cpu/o3/commit.hh"
#include "cpu/o3/thread_state.hh"
#include "cpu/base.hh"
#include "cpu/exetrace.hh"
#include "cpu/timebuf.hh"
#include "debug/Activity.hh"
#include "debug/Commit.hh"
#include "debug/CommitRate.hh"
#include "debug/ExecFaulting.hh"
#include "debug/O3PipeView.hh"
#include "params/DerivO3CPU.hh"
#include "sim/faults.hh"
#if USE_CHECKER
#include "cpu/checker/cpu.hh"
#endif
using namespace std;
template <class Impl>
DefaultCommit<Impl>::TrapEvent::TrapEvent(DefaultCommit<Impl> *_commit,
ThreadID _tid)
: Event(CPU_Tick_Pri, AutoDelete), commit(_commit), tid(_tid)
{
}
template <class Impl>
void
DefaultCommit<Impl>::TrapEvent::process()
{
// This will get reset by commit if it was switched out at the
// time of this event processing.
commit->trapSquash[tid] = true;
}
template <class Impl>
const char *
DefaultCommit<Impl>::TrapEvent::description() const
{
return "Trap";
}
template <class Impl>
DefaultCommit<Impl>::DefaultCommit(O3CPU *_cpu, DerivO3CPUParams *params)
: cpu(_cpu),
squashCounter(0),
iewToCommitDelay(params->iewToCommitDelay),
commitToIEWDelay(params->commitToIEWDelay),
renameToROBDelay(params->renameToROBDelay),
fetchToCommitDelay(params->commitToFetchDelay),
renameWidth(params->renameWidth),
commitWidth(params->commitWidth),
numThreads(params->numThreads),
drainPending(false),
switchedOut(false),
trapLatency(params->trapLatency)
{
_status = Active;
_nextStatus = Inactive;
std::string policy = params->smtCommitPolicy;
//Convert string to lowercase
std::transform(policy.begin(), policy.end(), policy.begin(),
(int(*)(int)) tolower);
//Assign commit policy
if (policy == "aggressive"){
commitPolicy = Aggressive;
DPRINTF(Commit,"Commit Policy set to Aggressive.\n");
} else if (policy == "roundrobin"){
commitPolicy = RoundRobin;
//Set-Up Priority List
for (ThreadID tid = 0; tid < numThreads; tid++) {
priority_list.push_back(tid);
}
DPRINTF(Commit,"Commit Policy set to Round Robin.\n");
} else if (policy == "oldestready"){
commitPolicy = OldestReady;
DPRINTF(Commit,"Commit Policy set to Oldest Ready.");
} else {
assert(0 && "Invalid SMT Commit Policy. Options Are: {Aggressive,"
"RoundRobin,OldestReady}");
}
for (ThreadID tid = 0; tid < numThreads; tid++) {
commitStatus[tid] = Idle;
changedROBNumEntries[tid] = false;
checkEmptyROB[tid] = false;
trapInFlight[tid] = false;
committedStores[tid] = false;
trapSquash[tid] = false;
tcSquash[tid] = false;
pc[tid].set(0);
lastCommitedSeqNum[tid] = 0;
}
#if FULL_SYSTEM
interrupt = NoFault;
#endif
}
template <class Impl>
std::string
DefaultCommit<Impl>::name() const
{
return cpu->name() + ".commit";
}
template <class Impl>
void
DefaultCommit<Impl>::regStats()
{
using namespace Stats;
commitCommittedInsts
.name(name() + ".commitCommittedInsts")
.desc("The number of committed instructions")
.prereq(commitCommittedInsts);
commitSquashedInsts
.name(name() + ".commitSquashedInsts")
.desc("The number of squashed insts skipped by commit")
.prereq(commitSquashedInsts);
commitSquashEvents
.name(name() + ".commitSquashEvents")
.desc("The number of times commit is told to squash")
.prereq(commitSquashEvents);
commitNonSpecStalls
.name(name() + ".commitNonSpecStalls")
.desc("The number of times commit has been forced to stall to "
"communicate backwards")
.prereq(commitNonSpecStalls);
branchMispredicts
.name(name() + ".branchMispredicts")
.desc("The number of times a branch was mispredicted")
.prereq(branchMispredicts);
numCommittedDist
.init(0,commitWidth,1)
.name(name() + ".committed_per_cycle")
.desc("Number of insts commited each cycle")
.flags(Stats::pdf)
;
statComInst
.init(cpu->numThreads)
.name(name() + ".count")
.desc("Number of instructions committed")
.flags(total)
;
statComSwp
.init(cpu->numThreads)
.name(name() + ".swp_count")
.desc("Number of s/w prefetches committed")
.flags(total)
;
statComRefs
.init(cpu->numThreads)
.name(name() + ".refs")
.desc("Number of memory references committed")
.flags(total)
;
statComLoads
.init(cpu->numThreads)
.name(name() + ".loads")
.desc("Number of loads committed")
.flags(total)
;
statComMembars
.init(cpu->numThreads)
.name(name() + ".membars")
.desc("Number of memory barriers committed")
.flags(total)
;
statComBranches
.init(cpu->numThreads)
.name(name() + ".branches")
.desc("Number of branches committed")
.flags(total)
;
statComFloating
.init(cpu->numThreads)
.name(name() + ".fp_insts")
.desc("Number of committed floating point instructions.")
.flags(total)
;
statComInteger
.init(cpu->numThreads)
.name(name()+".int_insts")
.desc("Number of committed integer instructions.")
.flags(total)
;
statComFunctionCalls
.init(cpu->numThreads)
.name(name()+".function_calls")
.desc("Number of function calls committed.")
.flags(total)
;
commitEligible
.init(cpu->numThreads)
.name(name() + ".bw_limited")
.desc("number of insts not committed due to BW limits")
.flags(total)
;
commitEligibleSamples
.name(name() + ".bw_lim_events")
.desc("number cycles where commit BW limit reached")
;
}
template <class Impl>
void
DefaultCommit<Impl>::setThreads(std::vector<Thread *> &threads)
{
thread = threads;
}
template <class Impl>
void
DefaultCommit<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr)
{
timeBuffer = tb_ptr;
// Setup wire to send information back to IEW.
toIEW = timeBuffer->getWire(0);
// Setup wire to read data from IEW (for the ROB).
robInfoFromIEW = timeBuffer->getWire(-iewToCommitDelay);
}
template <class Impl>
void
DefaultCommit<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr)
{
fetchQueue = fq_ptr;
// Setup wire to get instructions from rename (for the ROB).
fromFetch = fetchQueue->getWire(-fetchToCommitDelay);
}
template <class Impl>
void
DefaultCommit<Impl>::setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr)
{
renameQueue = rq_ptr;
// Setup wire to get instructions from rename (for the ROB).
fromRename = renameQueue->getWire(-renameToROBDelay);
}
template <class Impl>
void
DefaultCommit<Impl>::setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr)
{
iewQueue = iq_ptr;
// Setup wire to get instructions from IEW.
fromIEW = iewQueue->getWire(-iewToCommitDelay);
}
template <class Impl>
void
DefaultCommit<Impl>::setIEWStage(IEW *iew_stage)
{
iewStage = iew_stage;
}
template<class Impl>
void
DefaultCommit<Impl>::setActiveThreads(list<ThreadID> *at_ptr)
{
activeThreads = at_ptr;
}
template <class Impl>
void
DefaultCommit<Impl>::setRenameMap(RenameMap rm_ptr[])
{
for (ThreadID tid = 0; tid < numThreads; tid++)
renameMap[tid] = &rm_ptr[tid];
}
template <class Impl>
void
DefaultCommit<Impl>::setROB(ROB *rob_ptr)
{
rob = rob_ptr;
}
template <class Impl>
void
DefaultCommit<Impl>::initStage()
{
rob->setActiveThreads(activeThreads);
rob->resetEntries();
// Broadcast the number of free entries.
for (ThreadID tid = 0; tid < numThreads; tid++) {
toIEW->commitInfo[tid].usedROB = true;
toIEW->commitInfo[tid].freeROBEntries = rob->numFreeEntries(tid);
toIEW->commitInfo[tid].emptyROB = true;
}
// Commit must broadcast the number of free entries it has at the
// start of the simulation, so it starts as active.
cpu->activateStage(O3CPU::CommitIdx);
cpu->activityThisCycle();
trapLatency = cpu->ticks(trapLatency);
}
template <class Impl>
bool
DefaultCommit<Impl>::drain()
{
drainPending = true;
return false;
}
template <class Impl>
void
DefaultCommit<Impl>::switchOut()
{
switchedOut = true;
drainPending = false;
rob->switchOut();
}
template <class Impl>
void
DefaultCommit<Impl>::resume()
{
drainPending = false;
}
template <class Impl>
void
DefaultCommit<Impl>::takeOverFrom()
{
switchedOut = false;
_status = Active;
_nextStatus = Inactive;
for (ThreadID tid = 0; tid < numThreads; tid++) {
commitStatus[tid] = Idle;
changedROBNumEntries[tid] = false;
trapSquash[tid] = false;
tcSquash[tid] = false;
}
squashCounter = 0;
rob->takeOverFrom();
}
template <class Impl>
void
DefaultCommit<Impl>::updateStatus()
{
// reset ROB changed variable
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
changedROBNumEntries[tid] = false;
// Also check if any of the threads has a trap pending
if (commitStatus[tid] == TrapPending ||
commitStatus[tid] == FetchTrapPending) {
_nextStatus = Active;
}
}
if (_nextStatus == Inactive && _status == Active) {
DPRINTF(Activity, "Deactivating stage.\n");
cpu->deactivateStage(O3CPU::CommitIdx);
} else if (_nextStatus == Active && _status == Inactive) {
DPRINTF(Activity, "Activating stage.\n");
cpu->activateStage(O3CPU::CommitIdx);
}
_status = _nextStatus;
}
template <class Impl>
void
DefaultCommit<Impl>::setNextStatus()
{
int squashes = 0;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (commitStatus[tid] == ROBSquashing) {
squashes++;
}
}
squashCounter = squashes;
// If commit is currently squashing, then it will have activity for the
// next cycle. Set its next status as active.
if (squashCounter) {
_nextStatus = Active;
}
}
template <class Impl>
bool
DefaultCommit<Impl>::changedROBEntries()
{
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (changedROBNumEntries[tid]) {
return true;
}
}
return false;
}
template <class Impl>
size_t
DefaultCommit<Impl>::numROBFreeEntries(ThreadID tid)
{
return rob->numFreeEntries(tid);
}
template <class Impl>
void
DefaultCommit<Impl>::generateTrapEvent(ThreadID tid)
{
DPRINTF(Commit, "Generating trap event for [tid:%i]\n", tid);
TrapEvent *trap = new TrapEvent(this, tid);
cpu->schedule(trap, curTick() + trapLatency);
trapInFlight[tid] = true;
thread[tid]->trapPending = true;
}
template <class Impl>
void
DefaultCommit<Impl>::generateTCEvent(ThreadID tid)
{
assert(!trapInFlight[tid]);
DPRINTF(Commit, "Generating TC squash event for [tid:%i]\n", tid);
tcSquash[tid] = true;
}
template <class Impl>
void
DefaultCommit<Impl>::squashAll(ThreadID tid)
{
// If we want to include the squashing instruction in the squash,
// then use one older sequence number.
// Hopefully this doesn't mess things up. Basically I want to squash
// all instructions of this thread.
InstSeqNum squashed_inst = rob->isEmpty() ?
lastCommitedSeqNum[tid] : rob->readHeadInst(tid)->seqNum - 1;
// All younger instructions will be squashed. Set the sequence
// number as the youngest instruction in the ROB (0 in this case.
// Hopefully nothing breaks.)
youngestSeqNum[tid] = lastCommitedSeqNum[tid];
rob->squash(squashed_inst, tid);
changedROBNumEntries[tid] = true;
// Send back the sequence number of the squashed instruction.
toIEW->commitInfo[tid].doneSeqNum = squashed_inst;
// Send back the squash signal to tell stages that they should
// squash.
toIEW->commitInfo[tid].squash = true;
// Send back the rob squashing signal so other stages know that
// the ROB is in the process of squashing.
toIEW->commitInfo[tid].robSquashing = true;
toIEW->commitInfo[tid].mispredictInst = NULL;
toIEW->commitInfo[tid].squashInst = NULL;
toIEW->commitInfo[tid].pc = pc[tid];
}
template <class Impl>
void
DefaultCommit<Impl>::squashFromTrap(ThreadID tid)
{
squashAll(tid);
DPRINTF(Commit, "Squashing from trap, restarting at PC %s\n", pc[tid]);
thread[tid]->trapPending = false;
thread[tid]->inSyscall = false;
trapInFlight[tid] = false;
trapSquash[tid] = false;
commitStatus[tid] = ROBSquashing;
cpu->activityThisCycle();
}
template <class Impl>
void
DefaultCommit<Impl>::squashFromTC(ThreadID tid)
{
squashAll(tid);
DPRINTF(Commit, "Squashing from TC, restarting at PC %s\n", pc[tid]);
thread[tid]->inSyscall = false;
assert(!thread[tid]->trapPending);
commitStatus[tid] = ROBSquashing;
cpu->activityThisCycle();
tcSquash[tid] = false;
}
template <class Impl>
void
DefaultCommit<Impl>::squashAfter(ThreadID tid, DynInstPtr &head_inst,
uint64_t squash_after_seq_num)
{
youngestSeqNum[tid] = squash_after_seq_num;
rob->squash(squash_after_seq_num, tid);
changedROBNumEntries[tid] = true;
// Send back the sequence number of the squashed instruction.
toIEW->commitInfo[tid].doneSeqNum = squash_after_seq_num;
toIEW->commitInfo[tid].squashInst = head_inst;
// Send back the squash signal to tell stages that they should squash.
toIEW->commitInfo[tid].squash = true;
// Send back the rob squashing signal so other stages know that
// the ROB is in the process of squashing.
toIEW->commitInfo[tid].robSquashing = true;
toIEW->commitInfo[tid].mispredictInst = NULL;
toIEW->commitInfo[tid].pc = pc[tid];
DPRINTF(Commit, "Executing squash after for [tid:%i] inst [sn:%lli]\n",
tid, squash_after_seq_num);
commitStatus[tid] = ROBSquashing;
}
template <class Impl>
void
DefaultCommit<Impl>::tick()
{
wroteToTimeBuffer = false;
_nextStatus = Inactive;
if (drainPending && rob->isEmpty() && !iewStage->hasStoresToWB()) {
cpu->signalDrained();
drainPending = false;
return;
}
if (activeThreads->empty())
return;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
// Check if any of the threads are done squashing. Change the
// status if they are done.
while (threads != end) {
ThreadID tid = *threads++;
// Clear the bit saying if the thread has committed stores
// this cycle.
committedStores[tid] = false;
if (commitStatus[tid] == ROBSquashing) {
if (rob->isDoneSquashing(tid)) {
commitStatus[tid] = Running;
} else {
DPRINTF(Commit,"[tid:%u]: Still Squashing, cannot commit any"
" insts this cycle.\n", tid);
rob->doSquash(tid);
toIEW->commitInfo[tid].robSquashing = true;
wroteToTimeBuffer = true;
}
}
}
commit();
markCompletedInsts();
threads = activeThreads->begin();
while (threads != end) {
ThreadID tid = *threads++;
if (!rob->isEmpty(tid) && rob->readHeadInst(tid)->readyToCommit()) {
// The ROB has more instructions it can commit. Its next status
// will be active.
_nextStatus = Active;
DynInstPtr inst = rob->readHeadInst(tid);
DPRINTF(Commit,"[tid:%i]: Instruction [sn:%lli] PC %s is head of"
" ROB and ready to commit\n",
tid, inst->seqNum, inst->pcState());
} else if (!rob->isEmpty(tid)) {
DynInstPtr inst = rob->readHeadInst(tid);
DPRINTF(Commit,"[tid:%i]: Can't commit, Instruction [sn:%lli] PC "
"%s is head of ROB and not ready\n",
tid, inst->seqNum, inst->pcState());
}
DPRINTF(Commit, "[tid:%i]: ROB has %d insts & %d free entries.\n",
tid, rob->countInsts(tid), rob->numFreeEntries(tid));
}
if (wroteToTimeBuffer) {
DPRINTF(Activity, "Activity This Cycle.\n");
cpu->activityThisCycle();
}
updateStatus();
}
#if FULL_SYSTEM
template <class Impl>
void
DefaultCommit<Impl>::handleInterrupt()
{
// Verify that we still have an interrupt to handle
if (!cpu->checkInterrupts(cpu->tcBase(0))) {
DPRINTF(Commit, "Pending interrupt is cleared by master before "
"it got handled. Restart fetching from the orig path.\n");
toIEW->commitInfo[0].clearInterrupt = true;
interrupt = NoFault;
return;
}
// Wait until all in flight instructions are finished before enterring
// the interrupt.
if (cpu->instList.empty()) {
// Squash or record that I need to squash this cycle if
// an interrupt needed to be handled.
DPRINTF(Commit, "Interrupt detected.\n");
// Clear the interrupt now that it's going to be handled
toIEW->commitInfo[0].clearInterrupt = true;
assert(!thread[0]->inSyscall);
thread[0]->inSyscall = true;
// CPU will handle interrupt.
cpu->processInterrupts(interrupt);
thread[0]->inSyscall = false;
commitStatus[0] = TrapPending;
// Generate trap squash event.
generateTrapEvent(0);
interrupt = NoFault;
} else {
DPRINTF(Commit, "Interrupt pending, waiting for ROB to empty.\n");
}
}
template <class Impl>
void
DefaultCommit<Impl>::propagateInterrupt()
{
if (commitStatus[0] == TrapPending || interrupt || trapSquash[0] ||
tcSquash[0])
return;
// Process interrupts if interrupts are enabled, not in PAL
// mode, and no other traps or external squashes are currently
// pending.
// @todo: Allow other threads to handle interrupts.
// Get any interrupt that happened
interrupt = cpu->getInterrupts();
// Tell fetch that there is an interrupt pending. This
// will make fetch wait until it sees a non PAL-mode PC,
// at which point it stops fetching instructions.
if (interrupt != NoFault)
toIEW->commitInfo[0].interruptPending = true;
}
#endif // FULL_SYSTEM
template <class Impl>
void
DefaultCommit<Impl>::commit()
{
#if FULL_SYSTEM
// Check for any interrupt that we've already squashed for and start processing it.
if (interrupt != NoFault)
handleInterrupt();
// Check if we have a interrupt and get read to handle it
if (cpu->checkInterrupts(cpu->tcBase(0)))
propagateInterrupt();
#endif // FULL_SYSTEM
////////////////////////////////////
// Check for any possible squashes, handle them first
////////////////////////////////////
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
// Not sure which one takes priority. I think if we have
// both, that's a bad sign.
if (trapSquash[tid] == true) {
assert(!tcSquash[tid]);
squashFromTrap(tid);
} else if (tcSquash[tid] == true) {
assert(commitStatus[tid] != TrapPending);
squashFromTC(tid);
}
// Squashed sequence number must be older than youngest valid
// instruction in the ROB. This prevents squashes from younger
// instructions overriding squashes from older instructions.
if (fromIEW->squash[tid] &&
commitStatus[tid] != TrapPending &&
fromIEW->squashedSeqNum[tid] <= youngestSeqNum[tid]) {
if (fromIEW->mispredictInst[tid]) {
DPRINTF(Commit,
"[tid:%i]: Squashing due to branch mispred PC:%#x [sn:%i]\n",
tid,
fromIEW->mispredictInst[tid]->instAddr(),
fromIEW->squashedSeqNum[tid]);
} else {
DPRINTF(Commit,
"[tid:%i]: Squashing due to order violation [sn:%i]\n",
tid, fromIEW->squashedSeqNum[tid]);
}
DPRINTF(Commit, "[tid:%i]: Redirecting to PC %#x\n",
tid,
fromIEW->pc[tid].nextInstAddr());
commitStatus[tid] = ROBSquashing;
// If we want to include the squashing instruction in the squash,
// then use one older sequence number.
InstSeqNum squashed_inst = fromIEW->squashedSeqNum[tid];
if (fromIEW->includeSquashInst[tid] == true) {
squashed_inst--;
}
// All younger instructions will be squashed. Set the sequence
// number as the youngest instruction in the ROB.
youngestSeqNum[tid] = squashed_inst;
rob->squash(squashed_inst, tid);
changedROBNumEntries[tid] = true;
toIEW->commitInfo[tid].doneSeqNum = squashed_inst;
toIEW->commitInfo[tid].squash = true;
// Send back the rob squashing signal so other stages know that
// the ROB is in the process of squashing.
toIEW->commitInfo[tid].robSquashing = true;
toIEW->commitInfo[tid].mispredictInst =
fromIEW->mispredictInst[tid];
toIEW->commitInfo[tid].branchTaken =
fromIEW->branchTaken[tid];
toIEW->commitInfo[tid].squashInst = NULL;
toIEW->commitInfo[tid].pc = fromIEW->pc[tid];
if (toIEW->commitInfo[tid].mispredictInst) {
++branchMispredicts;
}
}
}
setNextStatus();
if (squashCounter != numThreads) {
// If we're not currently squashing, then get instructions.
getInsts();
// Try to commit any instructions.
commitInsts();
}
//Check for any activity
threads = activeThreads->begin();
while (threads != end) {
ThreadID tid = *threads++;
if (changedROBNumEntries[tid]) {
toIEW->commitInfo[tid].usedROB = true;
toIEW->commitInfo[tid].freeROBEntries = rob->numFreeEntries(tid);
wroteToTimeBuffer = true;
changedROBNumEntries[tid] = false;
if (rob->isEmpty(tid))
checkEmptyROB[tid] = true;
}
// ROB is only considered "empty" for previous stages if: a)
// ROB is empty, b) there are no outstanding stores, c) IEW
// stage has received any information regarding stores that
// committed.
// c) is checked by making sure to not consider the ROB empty
// on the same cycle as when stores have been committed.
// @todo: Make this handle multi-cycle communication between
// commit and IEW.
if (checkEmptyROB[tid] && rob->isEmpty(tid) &&
!iewStage->hasStoresToWB(tid) && !committedStores[tid]) {
checkEmptyROB[tid] = false;
toIEW->commitInfo[tid].usedROB = true;
toIEW->commitInfo[tid].emptyROB = true;
toIEW->commitInfo[tid].freeROBEntries = rob->numFreeEntries(tid);
wroteToTimeBuffer = true;
}
}
}
template <class Impl>
void
DefaultCommit<Impl>::commitInsts()
{
////////////////////////////////////
// Handle commit
// Note that commit will be handled prior to putting new
// instructions in the ROB so that the ROB only tries to commit
// instructions it has in this current cycle, and not instructions
// it is writing in during this cycle. Can't commit and squash
// things at the same time...
////////////////////////////////////
DPRINTF(Commit, "Trying to commit instructions in the ROB.\n");
unsigned num_committed = 0;
DynInstPtr head_inst;
// Commit as many instructions as possible until the commit bandwidth
// limit is reached, or it becomes impossible to commit any more.
while (num_committed < commitWidth) {
int commit_thread = getCommittingThread();
if (commit_thread == -1 || !rob->isHeadReady(commit_thread))
break;
head_inst = rob->readHeadInst(commit_thread);
ThreadID tid = head_inst->threadNumber;
assert(tid == commit_thread);
DPRINTF(Commit, "Trying to commit head instruction, [sn:%i] [tid:%i]\n",
head_inst->seqNum, tid);
// If the head instruction is squashed, it is ready to retire
// (be removed from the ROB) at any time.
if (head_inst->isSquashed()) {
DPRINTF(Commit, "Retiring squashed instruction from "
"ROB.\n");
rob->retireHead(commit_thread);
++commitSquashedInsts;
// Record that the number of ROB entries has changed.
changedROBNumEntries[tid] = true;
} else {
pc[tid] = head_inst->pcState();
// Increment the total number of non-speculative instructions
// executed.
// Hack for now: it really shouldn't happen until after the
// commit is deemed to be successful, but this count is needed
// for syscalls.
thread[tid]->funcExeInst++;
// Try to commit the head instruction.
bool commit_success = commitHead(head_inst, num_committed);
if (commit_success) {
++num_committed;
changedROBNumEntries[tid] = true;
// Set the doneSeqNum to the youngest committed instruction.
toIEW->commitInfo[tid].doneSeqNum = head_inst->seqNum;
++commitCommittedInsts;
// To match the old model, don't count nops and instruction
// prefetches towards the total commit count.
if (!head_inst->isNop() && !head_inst->isInstPrefetch()) {
cpu->instDone(tid);
}
// Updates misc. registers.
head_inst->updateMiscRegs();
cpu->traceFunctions(pc[tid].instAddr());
TheISA::advancePC(pc[tid], head_inst->staticInst);
// Keep track of the last sequence number commited
lastCommitedSeqNum[tid] = head_inst->seqNum;
// If this is an instruction that doesn't play nicely with
// others squash everything and restart fetch
if (head_inst->isSquashAfter())
squashAfter(tid, head_inst, head_inst->seqNum);
int count = 0;
Addr oldpc;
// Debug statement. Checks to make sure we're not
// currently updating state while handling PC events.
assert(!thread[tid]->inSyscall && !thread[tid]->trapPending);
do {
oldpc = pc[tid].instAddr();
cpu->system->pcEventQueue.service(thread[tid]->getTC());
count++;
} while (oldpc != pc[tid].instAddr());
if (count > 1) {
DPRINTF(Commit,
"PC skip function event, stopping commit\n");
break;
}
} else {
DPRINTF(Commit, "Unable to commit head instruction PC:%s "
"[tid:%i] [sn:%i].\n",
head_inst->pcState(), tid ,head_inst->seqNum);
break;
}
}
}
DPRINTF(CommitRate, "%i\n", num_committed);
numCommittedDist.sample(num_committed);
if (num_committed == commitWidth) {
commitEligibleSamples++;
}
}
template <class Impl>
bool
DefaultCommit<Impl>::commitHead(DynInstPtr &head_inst, unsigned inst_num)
{
assert(head_inst);
ThreadID tid = head_inst->threadNumber;
// If the instruction is not executed yet, then it will need extra
// handling. Signal backwards that it should be executed.
if (!head_inst->isExecuted()) {
// Keep this number correct. We have not yet actually executed
// and committed this instruction.
thread[tid]->funcExeInst--;
if (head_inst->isNonSpeculative() ||
head_inst->isStoreConditional() ||
head_inst->isMemBarrier() ||
head_inst->isWriteBarrier()) {
DPRINTF(Commit, "Encountered a barrier or non-speculative "
"instruction [sn:%lli] at the head of the ROB, PC %s.\n",
head_inst->seqNum, head_inst->pcState());
if (inst_num > 0 || iewStage->hasStoresToWB(tid)) {
DPRINTF(Commit, "Waiting for all stores to writeback.\n");
return false;
}
toIEW->commitInfo[tid].nonSpecSeqNum = head_inst->seqNum;
// Change the instruction so it won't try to commit again until
// it is executed.
head_inst->clearCanCommit();
++commitNonSpecStalls;
return false;
} else if (head_inst->isLoad()) {
if (inst_num > 0 || iewStage->hasStoresToWB(tid)) {
DPRINTF(Commit, "Waiting for all stores to writeback.\n");
return false;
}
assert(head_inst->uncacheable());
DPRINTF(Commit, "[sn:%lli]: Uncached load, PC %s.\n",
head_inst->seqNum, head_inst->pcState());
// Send back the non-speculative instruction's sequence
// number. Tell the lsq to re-execute the load.
toIEW->commitInfo[tid].nonSpecSeqNum = head_inst->seqNum;
toIEW->commitInfo[tid].uncached = true;
toIEW->commitInfo[tid].uncachedLoad = head_inst;
head_inst->clearCanCommit();
return false;
} else {
panic("Trying to commit un-executed instruction "
"of unknown type!\n");
}
}
if (head_inst->isThreadSync()) {
// Not handled for now.
panic("Thread sync instructions are not handled yet.\n");
}
// Check if the instruction caused a fault. If so, trap.
Fault inst_fault = head_inst->getFault();
// Stores mark themselves as completed.
if (!head_inst->isStore() && inst_fault == NoFault) {
head_inst->setCompleted();
}
#if USE_CHECKER
// Use checker prior to updating anything due to traps or PC
// based events.
if (cpu->checker) {
cpu->checker->verify(head_inst);
}
#endif
if (inst_fault != NoFault) {
DPRINTF(Commit, "Inst [sn:%lli] PC %s has a fault\n",
head_inst->seqNum, head_inst->pcState());
if (iewStage->hasStoresToWB(tid) || inst_num > 0) {
DPRINTF(Commit, "Stores outstanding, fault must wait.\n");
return false;
}
head_inst->setCompleted();
#if USE_CHECKER
if (cpu->checker && head_inst->isStore()) {
cpu->checker->verify(head_inst);
}
#endif
assert(!thread[tid]->inSyscall);
// Mark that we're in state update mode so that the trap's
// execution doesn't generate extra squashes.
thread[tid]->inSyscall = true;
// Execute the trap. Although it's slightly unrealistic in
// terms of timing (as it doesn't wait for the full timing of
// the trap event to complete before updating state), it's
// needed to update the state as soon as possible. This
// prevents external agents from changing any specific state
// that the trap need.
cpu->trap(inst_fault, tid, head_inst->staticInst);
// Exit state update mode to avoid accidental updating.
thread[tid]->inSyscall = false;
commitStatus[tid] = TrapPending;
DPRINTF(Commit, "Committing instruction with fault [sn:%lli]\n",
head_inst->seqNum);
if (head_inst->traceData) {
if (DTRACE(ExecFaulting)) {
head_inst->traceData->setFetchSeq(head_inst->seqNum);
head_inst->traceData->setCPSeq(thread[tid]->numInst);
head_inst->traceData->dump();
}
delete head_inst->traceData;
head_inst->traceData = NULL;
}
// Generate trap squash event.
generateTrapEvent(tid);
return false;
}
updateComInstStats(head_inst);
#if FULL_SYSTEM
if (thread[tid]->profile) {
thread[tid]->profilePC = head_inst->instAddr();
ProfileNode *node = thread[tid]->profile->consume(thread[tid]->getTC(),
head_inst->staticInst);
if (node)
thread[tid]->profileNode = node;
}
if (CPA::available()) {
if (head_inst->isControl()) {
ThreadContext *tc = thread[tid]->getTC();
CPA::cpa()->swAutoBegin(tc, head_inst->nextInstAddr());
}
}
#endif
DPRINTF(Commit, "Committing instruction with [sn:%lli] PC %s\n",
head_inst->seqNum, head_inst->pcState());
if (head_inst->traceData) {
head_inst->traceData->setFetchSeq(head_inst->seqNum);
head_inst->traceData->setCPSeq(thread[tid]->numInst);
head_inst->traceData->dump();
delete head_inst->traceData;
head_inst->traceData = NULL;
}
// Update the commit rename map
for (int i = 0; i < head_inst->numDestRegs(); i++) {
renameMap[tid]->setEntry(head_inst->flattenedDestRegIdx(i),
head_inst->renamedDestRegIdx(i));
}
// Finally clear the head ROB entry.
rob->retireHead(tid);
#if TRACING_ON
// Print info needed by the pipeline activity viewer.
DPRINTFR(O3PipeView, "O3PipeView:fetch:%llu:0x%08llx:%d:%llu:%s\n",
head_inst->fetchTick,
head_inst->instAddr(),
head_inst->microPC(),
head_inst->seqNum,
head_inst->staticInst->disassemble(head_inst->instAddr()));
DPRINTFR(O3PipeView, "O3PipeView:decode:%llu\n", head_inst->decodeTick);
DPRINTFR(O3PipeView, "O3PipeView:rename:%llu\n", head_inst->renameTick);
DPRINTFR(O3PipeView, "O3PipeView:dispatch:%llu\n", head_inst->dispatchTick);
DPRINTFR(O3PipeView, "O3PipeView:issue:%llu\n", head_inst->issueTick);
DPRINTFR(O3PipeView, "O3PipeView:complete:%llu\n", head_inst->completeTick);
DPRINTFR(O3PipeView, "O3PipeView:retire:%llu\n", curTick());
#endif
// If this was a store, record it for this cycle.
if (head_inst->isStore())
committedStores[tid] = true;
// Return true to indicate that we have committed an instruction.
return true;
}
template <class Impl>
void
DefaultCommit<Impl>::getInsts()
{
DPRINTF(Commit, "Getting instructions from Rename stage.\n");
// Read any renamed instructions and place them into the ROB.
int insts_to_process = std::min((int)renameWidth, fromRename->size);
for (int inst_num = 0; inst_num < insts_to_process; ++inst_num) {
DynInstPtr inst;
inst = fromRename->insts[inst_num];
ThreadID tid = inst->threadNumber;
if (!inst->isSquashed() &&
commitStatus[tid] != ROBSquashing &&
commitStatus[tid] != TrapPending) {
changedROBNumEntries[tid] = true;
DPRINTF(Commit, "Inserting PC %s [sn:%i] [tid:%i] into ROB.\n",
inst->pcState(), inst->seqNum, tid);
rob->insertInst(inst);
assert(rob->getThreadEntries(tid) <= rob->getMaxEntries(tid));
youngestSeqNum[tid] = inst->seqNum;
} else {
DPRINTF(Commit, "Instruction PC %s [sn:%i] [tid:%i] was "
"squashed, skipping.\n",
inst->pcState(), inst->seqNum, tid);
}
}
}
template <class Impl>
void
DefaultCommit<Impl>::skidInsert()
{
DPRINTF(Commit, "Attempting to any instructions from rename into "
"skidBuffer.\n");
for (int inst_num = 0; inst_num < fromRename->size; ++inst_num) {
DynInstPtr inst = fromRename->insts[inst_num];
if (!inst->isSquashed()) {
DPRINTF(Commit, "Inserting PC %s [sn:%i] [tid:%i] into ",
"skidBuffer.\n", inst->pcState(), inst->seqNum,
inst->threadNumber);
skidBuffer.push(inst);
} else {
DPRINTF(Commit, "Instruction PC %s [sn:%i] [tid:%i] was "
"squashed, skipping.\n",
inst->pcState(), inst->seqNum, inst->threadNumber);
}
}
}
template <class Impl>
void
DefaultCommit<Impl>::markCompletedInsts()
{
// Grab completed insts out of the IEW instruction queue, and mark
// instructions completed within the ROB.
for (int inst_num = 0;
inst_num < fromIEW->size && fromIEW->insts[inst_num];
++inst_num)
{
if (!fromIEW->insts[inst_num]->isSquashed()) {
DPRINTF(Commit, "[tid:%i]: Marking PC %s, [sn:%lli] ready "
"within ROB.\n",
fromIEW->insts[inst_num]->threadNumber,
fromIEW->insts[inst_num]->pcState(),
fromIEW->insts[inst_num]->seqNum);
// Mark the instruction as ready to commit.
fromIEW->insts[inst_num]->setCanCommit();
}
}
}
template <class Impl>
bool
DefaultCommit<Impl>::robDoneSquashing()
{
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (!rob->isDoneSquashing(tid))
return false;
}
return true;
}
template <class Impl>
void
DefaultCommit<Impl>::updateComInstStats(DynInstPtr &inst)
{
ThreadID tid = inst->threadNumber;
//
// Pick off the software prefetches
//
#ifdef TARGET_ALPHA
if (inst->isDataPrefetch()) {
statComSwp[tid]++;
} else {
statComInst[tid]++;
}
#else
statComInst[tid]++;
#endif
//
// Control Instructions
//
if (inst->isControl())
statComBranches[tid]++;
//
// Memory references
//
if (inst->isMemRef()) {
statComRefs[tid]++;
if (inst->isLoad()) {
statComLoads[tid]++;
}
}
if (inst->isMemBarrier()) {
statComMembars[tid]++;
}
// Integer Instruction
if (inst->isInteger())
statComInteger[tid]++;
// Floating Point Instruction
if (inst->isFloating())
statComFloating[tid]++;
// Function Calls
if (inst->isCall())
statComFunctionCalls[tid]++;
}
////////////////////////////////////////
// //
// SMT COMMIT POLICY MAINTAINED HERE //
// //
////////////////////////////////////////
template <class Impl>
ThreadID
DefaultCommit<Impl>::getCommittingThread()
{
if (numThreads > 1) {
switch (commitPolicy) {
case Aggressive:
//If Policy is Aggressive, commit will call
//this function multiple times per
//cycle
return oldestReady();
case RoundRobin:
return roundRobin();
case OldestReady:
return oldestReady();
default:
return InvalidThreadID;
}
} else {
assert(!activeThreads->empty());
ThreadID tid = activeThreads->front();
if (commitStatus[tid] == Running ||
commitStatus[tid] == Idle ||
commitStatus[tid] == FetchTrapPending) {
return tid;
} else {
return InvalidThreadID;
}
}
}
template<class Impl>
ThreadID
DefaultCommit<Impl>::roundRobin()
{
list<ThreadID>::iterator pri_iter = priority_list.begin();
list<ThreadID>::iterator end = priority_list.end();
while (pri_iter != end) {
ThreadID tid = *pri_iter;
if (commitStatus[tid] == Running ||
commitStatus[tid] == Idle ||
commitStatus[tid] == FetchTrapPending) {
if (rob->isHeadReady(tid)) {
priority_list.erase(pri_iter);
priority_list.push_back(tid);
return tid;
}
}
pri_iter++;
}
return InvalidThreadID;
}
template<class Impl>
ThreadID
DefaultCommit<Impl>::oldestReady()
{
unsigned oldest = 0;
bool first = true;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (!rob->isEmpty(tid) &&
(commitStatus[tid] == Running ||
commitStatus[tid] == Idle ||
commitStatus[tid] == FetchTrapPending)) {
if (rob->isHeadReady(tid)) {
DynInstPtr head_inst = rob->readHeadInst(tid);
if (first) {
oldest = tid;
first = false;
} else if (head_inst->seqNum < oldest) {
oldest = tid;
}
}
}
}
if (!first) {
return oldest;
} else {
return InvalidThreadID;
}
}
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