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gem5 / public / gem5 / de06ab35efefe162a2e78f046ddbd7b27b99b016 / . / src / cpu / o3 / commit_impl.hh
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/*
* Copyright 2014 Google, Inc.
* Copyright (c) 2010-2014, 2017, 2020 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.
*/
#ifndef __CPU_O3_COMMIT_IMPL_HH__
#define __CPU_O3_COMMIT_IMPL_HH__
#include <algorithm>
#include <set>
#include <string>
#include "arch/utility.hh"
#include "base/loader/symtab.hh"
#include "base/logging.hh"
#include "config/the_isa.hh"
#include "cpu/checker/cpu.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/Drain.hh"
#include "debug/ExecFaulting.hh"
#include "debug/HtmCpu.hh"
#include "debug/O3PipeView.hh"
#include "params/DerivO3CPU.hh"
#include "sim/faults.hh"
#include "sim/full_system.hh"
template <class Impl>
void
DefaultCommit<Impl>::processTrapEvent(ThreadID tid)
{
// This will get reset by commit if it was switched out at the
// time of this event processing.
trapSquash[tid] = true;
}
template <class Impl>
DefaultCommit<Impl>::DefaultCommit(O3CPU *_cpu, const DerivO3CPUParams &params)
: commitPolicy(params.smtCommitPolicy),
cpu(_cpu),
iewToCommitDelay(params.iewToCommitDelay),
commitToIEWDelay(params.commitToIEWDelay),
renameToROBDelay(params.renameToROBDelay),
fetchToCommitDelay(params.commitToFetchDelay),
renameWidth(params.renameWidth),
commitWidth(params.commitWidth),
numThreads(params.numThreads),
drainPending(false),
drainImminent(false),
trapLatency(params.trapLatency),
canHandleInterrupts(true),
avoidQuiesceLiveLock(false),
stats(_cpu, this)
{
if (commitWidth > Impl::MaxWidth)
fatal("commitWidth (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxWidth in src/cpu/o3/impl.hh\n",
commitWidth, static_cast<int>(Impl::MaxWidth));
_status = Active;
_nextStatus = Inactive;
if (commitPolicy == CommitPolicy::RoundRobin) {
//Set-Up Priority List
for (ThreadID tid = 0; tid < numThreads; tid++) {
priority_list.push_back(tid);
}
}
for (ThreadID tid = 0; tid < Impl::MaxThreads; tid++) {
commitStatus[tid] = Idle;
changedROBNumEntries[tid] = false;
trapSquash[tid] = false;
tcSquash[tid] = false;
squashAfterInst[tid] = nullptr;
pc[tid].set(0);
youngestSeqNum[tid] = 0;
lastCommitedSeqNum[tid] = 0;
trapInFlight[tid] = false;
committedStores[tid] = false;
checkEmptyROB[tid] = false;
renameMap[tid] = nullptr;
htmStarts[tid] = 0;
htmStops[tid] = 0;
}
interrupt = NoFault;
}
template <class Impl>
std::string
DefaultCommit<Impl>::name() const
{
return cpu->name() + ".commit";
}
template <class Impl>
void
DefaultCommit<Impl>::regProbePoints()
{
ppCommit = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Commit");
ppCommitStall = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "CommitStall");
ppSquash = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Squash");
}
template <class Impl>
DefaultCommit<Impl>::CommitStats::CommitStats(O3CPU *cpu,
DefaultCommit *commit)
: Stats::Group(cpu, "commit"),
ADD_STAT(commitSquashedInsts, UNIT_COUNT,
"The number of squashed insts skipped by commit"),
ADD_STAT(commitNonSpecStalls, UNIT_COUNT,
"The number of times commit has been forced to stall to "
"communicate backwards"),
ADD_STAT(branchMispredicts, UNIT_COUNT,
"The number of times a branch was mispredicted"),
ADD_STAT(numCommittedDist, UNIT_COUNT,
"Number of insts commited each cycle"),
ADD_STAT(instsCommitted, UNIT_COUNT, "Number of instructions committed"),
ADD_STAT(opsCommitted, UNIT_COUNT,
"Number of ops (including micro ops) committed"),
ADD_STAT(memRefs, UNIT_COUNT, "Number of memory references committed"),
ADD_STAT(loads, UNIT_COUNT, "Number of loads committed"),
ADD_STAT(amos, UNIT_COUNT, "Number of atomic instructions committed"),
ADD_STAT(membars, UNIT_COUNT, "Number of memory barriers committed"),
ADD_STAT(branches, UNIT_COUNT, "Number of branches committed"),
ADD_STAT(vectorInstructions, UNIT_COUNT,
"Number of committed Vector instructions."),
ADD_STAT(floating, UNIT_COUNT,
"Number of committed floating point instructions."),
ADD_STAT(integer, UNIT_COUNT,
"Number of committed integer instructions."),
ADD_STAT(functionCalls, UNIT_COUNT,
"Number of function calls committed."),
ADD_STAT(committedInstType, UNIT_COUNT,
"Class of committed instruction"),
ADD_STAT(commitEligibleSamples, UNIT_CYCLE,
"number cycles where commit BW limit reached")
{
using namespace Stats;
commitSquashedInsts.prereq(commitSquashedInsts);
commitNonSpecStalls.prereq(commitNonSpecStalls);
branchMispredicts.prereq(branchMispredicts);
numCommittedDist
.init(0,commit->commitWidth,1)
.flags(Stats::pdf);
instsCommitted
.init(cpu->numThreads)
.flags(total);
opsCommitted
.init(cpu->numThreads)
.flags(total);
memRefs
.init(cpu->numThreads)
.flags(total);
loads
.init(cpu->numThreads)
.flags(total);
amos
.init(cpu->numThreads)
.flags(total);
membars
.init(cpu->numThreads)
.flags(total);
branches
.init(cpu->numThreads)
.flags(total);
vectorInstructions
.init(cpu->numThreads)
.flags(total);
floating
.init(cpu->numThreads)
.flags(total);
integer
.init(cpu->numThreads)
.flags(total);
functionCalls
.init(commit->numThreads)
.flags(total);
committedInstType
.init(commit->numThreads,Enums::Num_OpClass)
.flags(total | pdf | dist);
committedInstType.ysubnames(Enums::OpClassStrings);
}
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(std::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>::startupStage()
{
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();
}
template <class Impl>
void
DefaultCommit<Impl>::clearStates(ThreadID 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;
squashAfterInst[tid] = NULL;
}
template <class Impl>
void
DefaultCommit<Impl>::drain()
{
drainPending = true;
}
template <class Impl>
void
DefaultCommit<Impl>::drainResume()
{
drainPending = false;
drainImminent = false;
}
template <class Impl>
void
DefaultCommit<Impl>::drainSanityCheck() const
{
assert(isDrained());
rob->drainSanityCheck();
// hardware transactional memory
// cannot drain partially through a transaction
for (ThreadID tid = 0; tid < numThreads; tid++) {
if (executingHtmTransaction(tid)) {
panic("cannot drain partially through a HTM transaction");
}
}
}
template <class Impl>
bool
DefaultCommit<Impl>::isDrained() const
{
/* Make sure no one is executing microcode. There are two reasons
* for this:
* - Hardware virtualized CPUs can't switch into the middle of a
* microcode sequence.
* - The current fetch implementation will most likely get very
* confused if it tries to start fetching an instruction that
* is executing in the middle of a ucode sequence that changes
* address mappings. This can happen on for example x86.
*/
for (ThreadID tid = 0; tid < numThreads; tid++) {
if (pc[tid].microPC() != 0)
return false;
}
/* Make sure that all instructions have finished committing before
* declaring the system as drained. We want the pipeline to be
* completely empty when we declare the CPU to be drained. This
* makes debugging easier since CPU handover and restoring from a
* checkpoint with a different CPU should have the same timing.
*/
return rob->isEmpty() &&
interrupt == NoFault;
}
template <class Impl>
void
DefaultCommit<Impl>::takeOverFrom()
{
_status = Active;
_nextStatus = Inactive;
for (ThreadID tid = 0; tid < numThreads; tid++) {
commitStatus[tid] = Idle;
changedROBNumEntries[tid] = false;
trapSquash[tid] = false;
tcSquash[tid] = false;
squashAfterInst[tid] = NULL;
}
rob->takeOverFrom();
}
template <class Impl>
void
DefaultCommit<Impl>::deactivateThread(ThreadID tid)
{
std::list<ThreadID>::iterator thread_it = std::find(priority_list.begin(),
priority_list.end(), tid);
if (thread_it != priority_list.end()) {
priority_list.erase(thread_it);
}
}
template <class Impl>
bool
DefaultCommit<Impl>::executingHtmTransaction(ThreadID tid) const
{
if (tid == InvalidThreadID)
return false;
else
return (htmStarts[tid] > htmStops[tid]);
}
template <class Impl>
void
DefaultCommit<Impl>::resetHtmStartsStops(ThreadID tid)
{
if (tid != InvalidThreadID)
{
htmStarts[tid] = 0;
htmStops[tid] = 0;
}
}
template <class Impl>
void
DefaultCommit<Impl>::updateStatus()
{
// reset ROB changed variable
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::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>
bool
DefaultCommit<Impl>::changedROBEntries()
{
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::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, Fault inst_fault)
{
DPRINTF(Commit, "Generating trap event for [tid:%i]\n", tid);
EventFunctionWrapper *trap = new EventFunctionWrapper(
[this, tid]{ processTrapEvent(tid); },
"Trap", true, Event::CPU_Tick_Pri);
Cycles latency = std::dynamic_pointer_cast<SyscallRetryFault>(inst_fault) ?
cpu->syscallRetryLatency : trapLatency;
// hardware transactional memory
if (inst_fault != nullptr &&
std::dynamic_pointer_cast<GenericHtmFailureFault>(inst_fault)) {
// TODO
// latency = default abort/restore latency
// could also do some kind of exponential back off if desired
}
cpu->schedule(trap, cpu->clockEdge(latency));
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(tid) ?
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]->noSquashFromTC = 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]->noSquashFromTC = false;
assert(!thread[tid]->trapPending);
commitStatus[tid] = ROBSquashing;
cpu->activityThisCycle();
tcSquash[tid] = false;
}
template <class Impl>
void
DefaultCommit<Impl>::squashFromSquashAfter(ThreadID tid)
{
DPRINTF(Commit, "Squashing after squash after request, "
"restarting at PC %s\n", pc[tid]);
squashAll(tid);
// Make sure to inform the fetch stage of which instruction caused
// the squash. It'll try to re-fetch an instruction executing in
// microcode unless this is set.
toIEW->commitInfo[tid].squashInst = squashAfterInst[tid];
squashAfterInst[tid] = NULL;
commitStatus[tid] = ROBSquashing;
cpu->activityThisCycle();
}
template <class Impl>
void
DefaultCommit<Impl>::squashAfter(ThreadID tid, const DynInstPtr &head_inst)
{
DPRINTF(Commit, "Executing squash after for [tid:%i] inst [sn:%llu]\n",
tid, head_inst->seqNum);
assert(!squashAfterInst[tid] || squashAfterInst[tid] == head_inst);
commitStatus[tid] = SquashAfterPending;
squashAfterInst[tid] = head_inst;
}
template <class Impl>
void
DefaultCommit<Impl>::tick()
{
wroteToTimeBuffer = false;
_nextStatus = Inactive;
if (activeThreads->empty())
return;
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::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:%i] 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;
M5_VAR_USED const DynInstPtr &inst = rob->readHeadInst(tid);
DPRINTF(Commit,"[tid:%i] Instruction [sn:%llu] PC %s is head of"
" ROB and ready to commit\n",
tid, inst->seqNum, inst->pcState());
} else if (!rob->isEmpty(tid)) {
const DynInstPtr &inst = rob->readHeadInst(tid);
ppCommitStall->notify(inst);
DPRINTF(Commit,"[tid:%i] Can't commit, Instruction [sn:%llu] 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();
}
template <class Impl>
void
DefaultCommit<Impl>::handleInterrupt()
{
// Verify that we still have an interrupt to handle
if (!cpu->checkInterrupts(0)) {
DPRINTF(Commit, "Pending interrupt is cleared by requestor before "
"it got handled. Restart fetching from the orig path.\n");
toIEW->commitInfo[0].clearInterrupt = true;
interrupt = NoFault;
avoidQuiesceLiveLock = true;
return;
}
// Wait until all in flight instructions are finished before enterring
// the interrupt.
if (canHandleInterrupts && 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]->noSquashFromTC);
thread[0]->noSquashFromTC = true;
if (cpu->checker) {
cpu->checker->handlePendingInt();
}
// CPU will handle interrupt. Note that we ignore the local copy of
// interrupt. This is because the local copy may no longer be the
// interrupt that the interrupt controller thinks is being handled.
cpu->processInterrupts(cpu->getInterrupts());
thread[0]->noSquashFromTC = false;
commitStatus[0] = TrapPending;
interrupt = NoFault;
// Generate trap squash event.
generateTrapEvent(0, interrupt);
avoidQuiesceLiveLock = false;
} else {
DPRINTF(Commit, "Interrupt pending: instruction is %sin "
"flight, ROB is %sempty\n",
canHandleInterrupts ? "not " : "",
cpu->instList.empty() ? "" : "not " );
}
}
template <class Impl>
void
DefaultCommit<Impl>::propagateInterrupt()
{
// Don't propagate intterupts if we are currently handling a trap or
// in draining and the last observable instruction has been committed.
if (commitStatus[0] == TrapPending || interrupt || trapSquash[0] ||
tcSquash[0] || drainImminent)
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;
}
template <class Impl>
void
DefaultCommit<Impl>::commit()
{
if (FullSystem) {
// Check if we have a interrupt and get read to handle it
if (cpu->checkInterrupts(0))
propagateInterrupt();
}
////////////////////////////////////
// Check for any possible squashes, handle them first
////////////////////////////////////
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::list<ThreadID>::iterator end = activeThreads->end();
int num_squashing_threads = 0;
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]) {
assert(!tcSquash[tid]);
squashFromTrap(tid);
// If the thread is trying to exit (i.e., an exit syscall was
// executed), this trapSquash was originated by the exit
// syscall earlier. In this case, schedule an exit event in
// the next cycle to fully terminate this thread
if (cpu->isThreadExiting(tid))
cpu->scheduleThreadExitEvent(tid);
} else if (tcSquash[tid]) {
assert(commitStatus[tid] != TrapPending);
squashFromTC(tid);
} else if (commitStatus[tid] == SquashAfterPending) {
// A squash from the previous cycle of the commit stage (i.e.,
// commitInsts() called squashAfter) is pending. Squash the
// thread now.
squashFromSquashAfter(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:%llu]\n",
tid,
fromIEW->mispredictInst[tid]->instAddr(),
fromIEW->squashedSeqNum[tid]);
} else {
DPRINTF(Commit,
"[tid:%i] Squashing due to order violation [sn:%llu]\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]) {
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 =
rob->findInst(tid, squashed_inst);
if (toIEW->commitInfo[tid].mispredictInst) {
if (toIEW->commitInfo[tid].mispredictInst->isUncondCtrl()) {
toIEW->commitInfo[tid].branchTaken = true;
}
++stats.branchMispredicts;
}
toIEW->commitInfo[tid].pc = fromIEW->pc[tid];
}
if (commitStatus[tid] == ROBSquashing) {
num_squashing_threads++;
}
}
// If commit is currently squashing, then it will have activity for the
// next cycle. Set its next status as active.
if (num_squashing_threads) {
_nextStatus = Active;
}
if (num_squashing_threads != 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) {
// hardware transactionally memory
// If executing within a transaction,
// need to handle interrupts specially
ThreadID commit_thread = getCommittingThread();
// Check for any interrupt that we've already squashed for
// and start processing it.
if (interrupt != NoFault) {
// If inside a transaction, postpone interrupts
if (executingHtmTransaction(commit_thread)) {
cpu->clearInterrupts(0);
toIEW->commitInfo[0].clearInterrupt = true;
interrupt = NoFault;
avoidQuiesceLiveLock = true;
} else {
handleInterrupt();
}
}
// ThreadID 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, [tid:%i] [sn:%llu]\n",
tid, head_inst->seqNum);
// 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);
++stats.commitSquashedInsts;
// Notify potential listeners that this instruction is squashed
ppSquash->notify(head_inst);
// 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;
stats.committedInstType[tid][head_inst->opClass()]++;
ppCommit->notify(head_inst);
// hardware transactional memory
// update nesting depth
if (head_inst->isHtmStart())
htmStarts[tid]++;
// sanity check
if (head_inst->inHtmTransactionalState()) {
assert(executingHtmTransaction(tid));
} else {
assert(!executingHtmTransaction(tid));
}
// update nesting depth
if (head_inst->isHtmStop())
htmStops[tid]++;
changedROBNumEntries[tid] = true;
// Set the doneSeqNum to the youngest committed instruction.
toIEW->commitInfo[tid].doneSeqNum = head_inst->seqNum;
if (tid == 0)
canHandleInterrupts = !head_inst->isDelayedCommit();
// at this point store conditionals should either have
// been completed or predicated false
assert(!head_inst->isStoreConditional() ||
head_inst->isCompleted() ||
!head_inst->readPredicate());
// Updates misc. registers.
head_inst->updateMiscRegs();
// Check instruction execution if it successfully commits and
// is not carrying a fault.
if (cpu->checker) {
cpu->checker->verify(head_inst);
}
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);
if (drainPending) {
if (pc[tid].microPC() == 0 && interrupt == NoFault &&
!thread[tid]->trapPending) {
// Last architectually committed instruction.
// Squash the pipeline, stall fetch, and use
// drainImminent to disable interrupts
DPRINTF(Drain, "Draining: %i:%s\n", tid, pc[tid]);
squashAfter(tid, head_inst);
cpu->commitDrained(tid);
drainImminent = true;
}
}
bool onInstBoundary = !head_inst->isMicroop() ||
head_inst->isLastMicroop() ||
!head_inst->isDelayedCommit();
if (onInstBoundary) {
int count = 0;
Addr oldpc;
// Make sure we're not currently updating state while
// handling PC events.
assert(!thread[tid]->noSquashFromTC &&
!thread[tid]->trapPending);
do {
oldpc = pc[tid].instAddr();
thread[tid]->pcEventQueue.service(
oldpc, thread[tid]->getTC());
count++;
} while (oldpc != pc[tid].instAddr());
if (count > 1) {
DPRINTF(Commit,
"PC skip function event, stopping commit\n");
break;
}
}
// Check if an instruction just enabled interrupts and we've
// previously had an interrupt pending that was not handled
// because interrupts were subsequently disabled before the
// pipeline reached a place to handle the interrupt. In that
// case squash now to make sure the interrupt is handled.
//
// If we don't do this, we might end up in a live lock situation
if (!interrupt && avoidQuiesceLiveLock &&
onInstBoundary && cpu->checkInterrupts(0))
squashAfter(tid, head_inst);
} else {
DPRINTF(Commit, "Unable to commit head instruction PC:%s "
"[tid:%i] [sn:%llu].\n",
head_inst->pcState(), tid ,head_inst->seqNum);
break;
}
}
}
DPRINTF(CommitRate, "%i\n", num_committed);
stats.numCommittedDist.sample(num_committed);
if (num_committed == commitWidth) {
stats.commitEligibleSamples++;
}
}
template <class Impl>
bool
DefaultCommit<Impl>::commitHead(const 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--;
// Make sure we are only trying to commit un-executed instructions we
// think are possible.
assert(head_inst->isNonSpeculative() || head_inst->isStoreConditional()
|| head_inst->isReadBarrier() || head_inst->isWriteBarrier()
|| head_inst->isAtomic()
|| (head_inst->isLoad() && head_inst->strictlyOrdered()));
DPRINTF(Commit,
"Encountered a barrier or non-speculative "
"instruction [tid:%i] [sn:%llu] "
"at the head of the ROB, PC %s.\n",
tid, head_inst->seqNum, head_inst->pcState());
if (inst_num > 0 || iewStage->hasStoresToWB(tid)) {
DPRINTF(Commit,
"[tid:%i] [sn:%llu] "
"Waiting for all stores to writeback.\n",
tid, head_inst->seqNum);
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();
if (head_inst->isLoad() && head_inst->strictlyOrdered()) {
DPRINTF(Commit, "[tid:%i] [sn:%llu] "
"Strictly ordered load, PC %s.\n",
tid, head_inst->seqNum, head_inst->pcState());
toIEW->commitInfo[tid].strictlyOrdered = true;
toIEW->commitInfo[tid].strictlyOrderedLoad = head_inst;
} else {
++stats.commitNonSpecStalls;
}
return false;
}
// Check if the instruction caused a fault. If so, trap.
Fault inst_fault = head_inst->getFault();
// hardware transactional memory
// if a fault occurred within a HTM transaction
// ensure that the transaction aborts
if (inst_fault != NoFault && head_inst->inHtmTransactionalState()) {
// There exists a generic HTM fault common to all ISAs
if (!std::dynamic_pointer_cast<GenericHtmFailureFault>(inst_fault)) {
DPRINTF(HtmCpu, "%s - fault (%s) encountered within transaction"
" - converting to GenericHtmFailureFault\n",
head_inst->staticInst->getName(), inst_fault->name());
inst_fault = std::make_shared<GenericHtmFailureFault>(
head_inst->getHtmTransactionUid(),
HtmFailureFaultCause::EXCEPTION);
}
// If this point is reached and the fault inherits from the HTM fault,
// then there is no need to raise a new fault
}
// Stores mark themselves as completed.
if (!head_inst->isStore() && inst_fault == NoFault) {
head_inst->setCompleted();
}
if (inst_fault != NoFault) {
DPRINTF(Commit, "Inst [tid:%i] [sn:%llu] PC %s has a fault\n",
tid, head_inst->seqNum, head_inst->pcState());
if (iewStage->hasStoresToWB(tid) || inst_num > 0) {
DPRINTF(Commit,
"[tid:%i] [sn:%llu] "
"Stores outstanding, fault must wait.\n",
tid, head_inst->seqNum);
return false;
}
head_inst->setCompleted();
// If instruction has faulted, let the checker execute it and
// check if it sees the same fault and control flow.
if (cpu->checker) {
// Need to check the instruction before its fault is processed
cpu->checker->verify(head_inst);
}
assert(!thread[tid]->noSquashFromTC);
// Mark that we're in state update mode so that the trap's
// execution doesn't generate extra squashes.
thread[tid]->noSquashFromTC = 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->notAnInst() ?
StaticInst::nullStaticInstPtr :
head_inst->staticInst);
// Exit state update mode to avoid accidental updating.
thread[tid]->noSquashFromTC = false;
commitStatus[tid] = TrapPending;
DPRINTF(Commit,
"[tid:%i] [sn:%llu] Committing instruction with fault\n",
tid, head_inst->seqNum);
if (head_inst->traceData) {
// We ignore ReExecution "faults" here as they are not real
// (architectural) faults but signal flush/replays.
if (DTRACE(ExecFaulting)
&& dynamic_cast<ReExec*>(inst_fault.get()) == nullptr) {
head_inst->traceData->setFaulting(true);
head_inst->traceData->setFetchSeq(head_inst->seqNum);
head_inst->traceData->setCPSeq(thread[tid]->numOp);
head_inst->traceData->dump();
}
delete head_inst->traceData;
head_inst->traceData = NULL;
}
// Generate trap squash event.
generateTrapEvent(tid, inst_fault);
return false;
}
updateComInstStats(head_inst);
DPRINTF(Commit,
"[tid:%i] [sn:%llu] Committing instruction with PC %s\n",
tid, head_inst->seqNum, head_inst->pcState());
if (head_inst->traceData) {
head_inst->traceData->setFetchSeq(head_inst->seqNum);
head_inst->traceData->setCPSeq(thread[tid]->numOp);
head_inst->traceData->dump();
delete head_inst->traceData;
head_inst->traceData = NULL;
}
if (head_inst->isReturn()) {
DPRINTF(Commit,
"[tid:%i] [sn:%llu] Return Instruction Committed PC %s \n",
tid, head_inst->seqNum, head_inst->pcState());
}
// Update the commit rename map
for (int i = 0; i < head_inst->numDestRegs(); i++) {
renameMap[tid]->setEntry(head_inst->regs.flattenedDestIdx(i),
head_inst->regs.renamedDestIdx(i));
}
// hardware transactional memory
// the HTM UID is purely for correctness and debugging purposes
if (head_inst->isHtmStart())
iewStage->setLastRetiredHtmUid(tid, head_inst->getHtmTransactionUid());
// Finally clear the head ROB entry.
rob->retireHead(tid);
#if TRACING_ON
if (DTRACE(O3PipeView)) {
head_inst->commitTick = curTick() - head_inst->fetchTick;
}
#endif
// If this was a store, record it for this cycle.
if (head_inst->isStore() || head_inst->isAtomic())
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) {
const DynInstPtr &inst = fromRename->insts[inst_num];
ThreadID tid = inst->threadNumber;
if (!inst->isSquashed() &&
commitStatus[tid] != ROBSquashing &&
commitStatus[tid] != TrapPending) {
changedROBNumEntries[tid] = true;
DPRINTF(Commit, "[tid:%i] [sn:%llu] Inserting PC %s into ROB.\n",
inst->seqNum, tid, inst->pcState());
rob->insertInst(inst);
assert(rob->getThreadEntries(tid) <= rob->getMaxEntries(tid));
youngestSeqNum[tid] = inst->seqNum;
} else {
DPRINTF(Commit, "[tid:%i] [sn:%llu] "
"Instruction PC %s was squashed, skipping.\n",
inst->seqNum, tid, inst->pcState());
}
}
}
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; ++inst_num) {
assert(fromIEW->insts[inst_num]);
if (!fromIEW->insts[inst_num]->isSquashed()) {
DPRINTF(Commit, "[tid:%i] Marking PC %s, [sn:%llu] 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>
void
DefaultCommit<Impl>::updateComInstStats(const DynInstPtr &inst)
{
ThreadID tid = inst->threadNumber;
if (!inst->isMicroop() || inst->isLastMicroop())
stats.instsCommitted[tid]++;
stats.opsCommitted[tid]++;
// To match the old model, don't count nops and instruction
// prefetches towards the total commit count.
if (!inst->isNop() && !inst->isInstPrefetch()) {
cpu->instDone(tid, inst);
}
//
// Control Instructions
//
if (inst->isControl())
stats.branches[tid]++;
//
// Memory references
//
if (inst->isMemRef()) {
stats.memRefs[tid]++;
if (inst->isLoad()) {
stats.loads[tid]++;
}
if (inst->isAtomic()) {
stats.amos[tid]++;
}
}
if (inst->isFullMemBarrier()) {
stats.membars[tid]++;
}
// Integer Instruction
if (inst->isInteger())
stats.integer[tid]++;
// Floating Point Instruction
if (inst->isFloating())
stats.floating[tid]++;
// Vector Instruction
if (inst->isVector())
stats.vectorInstructions[tid]++;
// Function Calls
if (inst->isCall())
stats.functionCalls[tid]++;
}
////////////////////////////////////////
// //
// SMT COMMIT POLICY MAINTAINED HERE //
// //
////////////////////////////////////////
template <class Impl>
ThreadID
DefaultCommit<Impl>::getCommittingThread()
{
if (numThreads > 1) {
switch (commitPolicy) {
case CommitPolicy::Aggressive:
//If Policy is Aggressive, commit will call
//this function multiple times per
//cycle
return oldestReady();
case CommitPolicy::RoundRobin:
return roundRobin();
case CommitPolicy::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()
{
std::list<ThreadID>::iterator pri_iter = priority_list.begin();
std::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;
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::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)) {
const 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;
}
}
#endif//__CPU_O3_COMMIT_IMPL_HH__