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gem5/src/cpu/o3/iew_impl.hh
Rekai Gonzalez-Alberquilla ad296b068c cpu: Fix the O3 CPU Drain 
The drain did not wait until stages were ready again. Therefore, as a
result of messages in the TimeBuffer being drain, the state after the
drain was not consistent and asserts fired in some places when the
draining happened after a stage got blocked, but before the notification
arrived to the previous stages.

Change-Id: Ib50b3b40b7f745b62c1eba2931dec76860824c71
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
2016-09-22 10:49:10 +01:00

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/*
* Copyright (c) 2010-2013 ARM Limited
* Copyright (c) 2013 Advanced Micro Devices, Inc.
* 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
*/
#ifndef __CPU_O3_IEW_IMPL_IMPL_HH__
#define __CPU_O3_IEW_IMPL_IMPL_HH__
// @todo: Fix the instantaneous communication among all the stages within
// iew. There's a clear delay between issue and execute, yet backwards
// communication happens simultaneously.
#include <queue>
#include "arch/utility.hh"
#include "config/the_isa.hh"
#include "cpu/checker/cpu.hh"
#include "cpu/o3/fu_pool.hh"
#include "cpu/o3/iew.hh"
#include "cpu/timebuf.hh"
#include "debug/Activity.hh"
#include "debug/Drain.hh"
#include "debug/IEW.hh"
#include "debug/O3PipeView.hh"
#include "params/DerivO3CPU.hh"
using namespace std;
template<class Impl>
DefaultIEW<Impl>::DefaultIEW(O3CPU *_cpu, DerivO3CPUParams *params)
: issueToExecQueue(params->backComSize, params->forwardComSize),
cpu(_cpu),
instQueue(_cpu, this, params),
ldstQueue(_cpu, this, params),
fuPool(params->fuPool),
commitToIEWDelay(params->commitToIEWDelay),
renameToIEWDelay(params->renameToIEWDelay),
issueToExecuteDelay(params->issueToExecuteDelay),
dispatchWidth(params->dispatchWidth),
issueWidth(params->issueWidth),
wbWidth(params->wbWidth),
numThreads(params->numThreads)
{
if (dispatchWidth > Impl::MaxWidth)
fatal("dispatchWidth (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxWidth in src/cpu/o3/impl.hh\n",
dispatchWidth, static_cast<int>(Impl::MaxWidth));
if (issueWidth > Impl::MaxWidth)
fatal("issueWidth (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxWidth in src/cpu/o3/impl.hh\n",
issueWidth, static_cast<int>(Impl::MaxWidth));
if (wbWidth > Impl::MaxWidth)
fatal("wbWidth (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxWidth in src/cpu/o3/impl.hh\n",
wbWidth, static_cast<int>(Impl::MaxWidth));
_status = Active;
exeStatus = Running;
wbStatus = Idle;
// Setup wire to read instructions coming from issue.
fromIssue = issueToExecQueue.getWire(-issueToExecuteDelay);
// Instruction queue needs the queue between issue and execute.
instQueue.setIssueToExecuteQueue(&issueToExecQueue);
for (ThreadID tid = 0; tid < numThreads; tid++) {
dispatchStatus[tid] = Running;
fetchRedirect[tid] = false;
}
updateLSQNextCycle = false;
skidBufferMax = (renameToIEWDelay + 1) * params->renameWidth;
}
template <class Impl>
std::string
DefaultIEW<Impl>::name() const
{
return cpu->name() + ".iew";
}
template <class Impl>
void
DefaultIEW<Impl>::regProbePoints()
{
ppDispatch = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Dispatch");
ppMispredict = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Mispredict");
/**
* Probe point with dynamic instruction as the argument used to probe when
* an instruction starts to execute.
*/
ppExecute = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(),
"Execute");
/**
* Probe point with dynamic instruction as the argument used to probe when
* an instruction execution completes and it is marked ready to commit.
*/
ppToCommit = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(),
"ToCommit");
}
template <class Impl>
void
DefaultIEW<Impl>::regStats()
{
using namespace Stats;
instQueue.regStats();
ldstQueue.regStats();
iewIdleCycles
.name(name() + ".iewIdleCycles")
.desc("Number of cycles IEW is idle");
iewSquashCycles
.name(name() + ".iewSquashCycles")
.desc("Number of cycles IEW is squashing");
iewBlockCycles
.name(name() + ".iewBlockCycles")
.desc("Number of cycles IEW is blocking");
iewUnblockCycles
.name(name() + ".iewUnblockCycles")
.desc("Number of cycles IEW is unblocking");
iewDispatchedInsts
.name(name() + ".iewDispatchedInsts")
.desc("Number of instructions dispatched to IQ");
iewDispSquashedInsts
.name(name() + ".iewDispSquashedInsts")
.desc("Number of squashed instructions skipped by dispatch");
iewDispLoadInsts
.name(name() + ".iewDispLoadInsts")
.desc("Number of dispatched load instructions");
iewDispStoreInsts
.name(name() + ".iewDispStoreInsts")
.desc("Number of dispatched store instructions");
iewDispNonSpecInsts
.name(name() + ".iewDispNonSpecInsts")
.desc("Number of dispatched non-speculative instructions");
iewIQFullEvents
.name(name() + ".iewIQFullEvents")
.desc("Number of times the IQ has become full, causing a stall");
iewLSQFullEvents
.name(name() + ".iewLSQFullEvents")
.desc("Number of times the LSQ has become full, causing a stall");
memOrderViolationEvents
.name(name() + ".memOrderViolationEvents")
.desc("Number of memory order violations");
predictedTakenIncorrect
.name(name() + ".predictedTakenIncorrect")
.desc("Number of branches that were predicted taken incorrectly");
predictedNotTakenIncorrect
.name(name() + ".predictedNotTakenIncorrect")
.desc("Number of branches that were predicted not taken incorrectly");
branchMispredicts
.name(name() + ".branchMispredicts")
.desc("Number of branch mispredicts detected at execute");
branchMispredicts = predictedTakenIncorrect + predictedNotTakenIncorrect;
iewExecutedInsts
.name(name() + ".iewExecutedInsts")
.desc("Number of executed instructions");
iewExecLoadInsts
.init(cpu->numThreads)
.name(name() + ".iewExecLoadInsts")
.desc("Number of load instructions executed")
.flags(total);
iewExecSquashedInsts
.name(name() + ".iewExecSquashedInsts")
.desc("Number of squashed instructions skipped in execute");
iewExecutedSwp
.init(cpu->numThreads)
.name(name() + ".exec_swp")
.desc("number of swp insts executed")
.flags(total);
iewExecutedNop
.init(cpu->numThreads)
.name(name() + ".exec_nop")
.desc("number of nop insts executed")
.flags(total);
iewExecutedRefs
.init(cpu->numThreads)
.name(name() + ".exec_refs")
.desc("number of memory reference insts executed")
.flags(total);
iewExecutedBranches
.init(cpu->numThreads)
.name(name() + ".exec_branches")
.desc("Number of branches executed")
.flags(total);
iewExecStoreInsts
.name(name() + ".exec_stores")
.desc("Number of stores executed")
.flags(total);
iewExecStoreInsts = iewExecutedRefs - iewExecLoadInsts;
iewExecRate
.name(name() + ".exec_rate")
.desc("Inst execution rate")
.flags(total);
iewExecRate = iewExecutedInsts / cpu->numCycles;
iewInstsToCommit
.init(cpu->numThreads)
.name(name() + ".wb_sent")
.desc("cumulative count of insts sent to commit")
.flags(total);
writebackCount
.init(cpu->numThreads)
.name(name() + ".wb_count")
.desc("cumulative count of insts written-back")
.flags(total);
producerInst
.init(cpu->numThreads)
.name(name() + ".wb_producers")
.desc("num instructions producing a value")
.flags(total);
consumerInst
.init(cpu->numThreads)
.name(name() + ".wb_consumers")
.desc("num instructions consuming a value")
.flags(total);
wbFanout
.name(name() + ".wb_fanout")
.desc("average fanout of values written-back")
.flags(total);
wbFanout = producerInst / consumerInst;
wbRate
.name(name() + ".wb_rate")
.desc("insts written-back per cycle")
.flags(total);
wbRate = writebackCount / cpu->numCycles;
}
template<class Impl>
void
DefaultIEW<Impl>::startupStage()
{
for (ThreadID tid = 0; tid < numThreads; tid++) {
toRename->iewInfo[tid].usedIQ = true;
toRename->iewInfo[tid].freeIQEntries =
instQueue.numFreeEntries(tid);
toRename->iewInfo[tid].usedLSQ = true;
toRename->iewInfo[tid].freeLQEntries = ldstQueue.numFreeLoadEntries(tid);
toRename->iewInfo[tid].freeSQEntries = ldstQueue.numFreeStoreEntries(tid);
}
// Initialize the checker's dcache port here
if (cpu->checker) {
cpu->checker->setDcachePort(&cpu->getDataPort());
}
cpu->activateStage(O3CPU::IEWIdx);
}
template<class Impl>
void
DefaultIEW<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr)
{
timeBuffer = tb_ptr;
// Setup wire to read information from time buffer, from commit.
fromCommit = timeBuffer->getWire(-commitToIEWDelay);
// Setup wire to write information back to previous stages.
toRename = timeBuffer->getWire(0);
toFetch = timeBuffer->getWire(0);
// Instruction queue also needs main time buffer.
instQueue.setTimeBuffer(tb_ptr);
}
template<class Impl>
void
DefaultIEW<Impl>::setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr)
{
renameQueue = rq_ptr;
// Setup wire to read information from rename queue.
fromRename = renameQueue->getWire(-renameToIEWDelay);
}
template<class Impl>
void
DefaultIEW<Impl>::setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr)
{
iewQueue = iq_ptr;
// Setup wire to write instructions to commit.
toCommit = iewQueue->getWire(0);
}
template<class Impl>
void
DefaultIEW<Impl>::setActiveThreads(list<ThreadID> *at_ptr)
{
activeThreads = at_ptr;
ldstQueue.setActiveThreads(at_ptr);
instQueue.setActiveThreads(at_ptr);
}
template<class Impl>
void
DefaultIEW<Impl>::setScoreboard(Scoreboard *sb_ptr)
{
scoreboard = sb_ptr;
}
template <class Impl>
bool
DefaultIEW<Impl>::isDrained() const
{
bool drained = ldstQueue.isDrained() && instQueue.isDrained();
for (ThreadID tid = 0; tid < numThreads; tid++) {
if (!insts[tid].empty()) {
DPRINTF(Drain, "%i: Insts not empty.\n", tid);
drained = false;
}
if (!skidBuffer[tid].empty()) {
DPRINTF(Drain, "%i: Skid buffer not empty.\n", tid);
drained = false;
}
drained = drained && dispatchStatus[tid] == Running;
}
// Also check the FU pool as instructions are "stored" in FU
// completion events until they are done and not accounted for
// above
if (drained && !fuPool->isDrained()) {
DPRINTF(Drain, "FU pool still busy.\n");
drained = false;
}
return drained;
}
template <class Impl>
void
DefaultIEW<Impl>::drainSanityCheck() const
{
assert(isDrained());
instQueue.drainSanityCheck();
ldstQueue.drainSanityCheck();
}
template <class Impl>
void
DefaultIEW<Impl>::takeOverFrom()
{
// Reset all state.
_status = Active;
exeStatus = Running;
wbStatus = Idle;
instQueue.takeOverFrom();
ldstQueue.takeOverFrom();
fuPool->takeOverFrom();
startupStage();
cpu->activityThisCycle();
for (ThreadID tid = 0; tid < numThreads; tid++) {
dispatchStatus[tid] = Running;
fetchRedirect[tid] = false;
}
updateLSQNextCycle = false;
for (int i = 0; i < issueToExecQueue.getSize(); ++i) {
issueToExecQueue.advance();
}
}
template<class Impl>
void
DefaultIEW<Impl>::squash(ThreadID tid)
{
DPRINTF(IEW, "[tid:%i]: Squashing all instructions.\n", tid);
// Tell the IQ to start squashing.
instQueue.squash(tid);
// Tell the LDSTQ to start squashing.
ldstQueue.squash(fromCommit->commitInfo[tid].doneSeqNum, tid);
updatedQueues = true;
// Clear the skid buffer in case it has any data in it.
DPRINTF(IEW, "[tid:%i]: Removing skidbuffer instructions until [sn:%i].\n",
tid, fromCommit->commitInfo[tid].doneSeqNum);
while (!skidBuffer[tid].empty()) {
if (skidBuffer[tid].front()->isLoad()) {
toRename->iewInfo[tid].dispatchedToLQ++;
}
if (skidBuffer[tid].front()->isStore()) {
toRename->iewInfo[tid].dispatchedToSQ++;
}
toRename->iewInfo[tid].dispatched++;
skidBuffer[tid].pop();
}
emptyRenameInsts(tid);
}
template<class Impl>
void
DefaultIEW<Impl>::squashDueToBranch(DynInstPtr &inst, ThreadID tid)
{
DPRINTF(IEW, "[tid:%i]: Squashing from a specific instruction, PC: %s "
"[sn:%i].\n", tid, inst->pcState(), inst->seqNum);
if (!toCommit->squash[tid] ||
inst->seqNum < toCommit->squashedSeqNum[tid]) {
toCommit->squash[tid] = true;
toCommit->squashedSeqNum[tid] = inst->seqNum;
toCommit->branchTaken[tid] = inst->pcState().branching();
TheISA::PCState pc = inst->pcState();
TheISA::advancePC(pc, inst->staticInst);
toCommit->pc[tid] = pc;
toCommit->mispredictInst[tid] = inst;
toCommit->includeSquashInst[tid] = false;
wroteToTimeBuffer = true;
}
}
template<class Impl>
void
DefaultIEW<Impl>::squashDueToMemOrder(DynInstPtr &inst, ThreadID tid)
{
DPRINTF(IEW, "[tid:%i]: Memory violation, squashing violator and younger "
"insts, PC: %s [sn:%i].\n", tid, inst->pcState(), inst->seqNum);
// Need to include inst->seqNum in the following comparison to cover the
// corner case when a branch misprediction and a memory violation for the
// same instruction (e.g. load PC) are detected in the same cycle. In this
// case the memory violator should take precedence over the branch
// misprediction because it requires the violator itself to be included in
// the squash.
if (!toCommit->squash[tid] ||
inst->seqNum <= toCommit->squashedSeqNum[tid]) {
toCommit->squash[tid] = true;
toCommit->squashedSeqNum[tid] = inst->seqNum;
toCommit->pc[tid] = inst->pcState();
toCommit->mispredictInst[tid] = NULL;
// Must include the memory violator in the squash.
toCommit->includeSquashInst[tid] = true;
wroteToTimeBuffer = true;
}
}
template<class Impl>
void
DefaultIEW<Impl>::block(ThreadID tid)
{
DPRINTF(IEW, "[tid:%u]: Blocking.\n", tid);
if (dispatchStatus[tid] != Blocked &&
dispatchStatus[tid] != Unblocking) {
toRename->iewBlock[tid] = true;
wroteToTimeBuffer = true;
}
// Add the current inputs to the skid buffer so they can be
// reprocessed when this stage unblocks.
skidInsert(tid);
dispatchStatus[tid] = Blocked;
}
template<class Impl>
void
DefaultIEW<Impl>::unblock(ThreadID tid)
{
DPRINTF(IEW, "[tid:%i]: Reading instructions out of the skid "
"buffer %u.\n",tid, tid);
// If the skid bufffer is empty, signal back to previous stages to unblock.
// Also switch status to running.
if (skidBuffer[tid].empty()) {
toRename->iewUnblock[tid] = true;
wroteToTimeBuffer = true;
DPRINTF(IEW, "[tid:%i]: Done unblocking.\n",tid);
dispatchStatus[tid] = Running;
}
}
template<class Impl>
void
DefaultIEW<Impl>::wakeDependents(DynInstPtr &inst)
{
instQueue.wakeDependents(inst);
}
template<class Impl>
void
DefaultIEW<Impl>::rescheduleMemInst(DynInstPtr &inst)
{
instQueue.rescheduleMemInst(inst);
}
template<class Impl>
void
DefaultIEW<Impl>::replayMemInst(DynInstPtr &inst)
{
instQueue.replayMemInst(inst);
}
template<class Impl>
void
DefaultIEW<Impl>::blockMemInst(DynInstPtr& inst)
{
instQueue.blockMemInst(inst);
}
template<class Impl>
void
DefaultIEW<Impl>::cacheUnblocked()
{
instQueue.cacheUnblocked();
}
template<class Impl>
void
DefaultIEW<Impl>::instToCommit(DynInstPtr &inst)
{
// This function should not be called after writebackInsts in a
// single cycle. That will cause problems with an instruction
// being added to the queue to commit without being processed by
// writebackInsts prior to being sent to commit.
// First check the time slot that this instruction will write
// to. If there are free write ports at the time, then go ahead
// and write the instruction to that time. If there are not,
// keep looking back to see where's the first time there's a
// free slot.
while ((*iewQueue)[wbCycle].insts[wbNumInst]) {
++wbNumInst;
if (wbNumInst == wbWidth) {
++wbCycle;
wbNumInst = 0;
}
}
DPRINTF(IEW, "Current wb cycle: %i, width: %i, numInst: %i\nwbActual:%i\n",
wbCycle, wbWidth, wbNumInst, wbCycle * wbWidth + wbNumInst);
// Add finished instruction to queue to commit.
(*iewQueue)[wbCycle].insts[wbNumInst] = inst;
(*iewQueue)[wbCycle].size++;
}
template <class Impl>
unsigned
DefaultIEW<Impl>::validInstsFromRename()
{
unsigned inst_count = 0;
for (int i=0; i<fromRename->size; i++) {
if (!fromRename->insts[i]->isSquashed())
inst_count++;
}
return inst_count;
}
template<class Impl>
void
DefaultIEW<Impl>::skidInsert(ThreadID tid)
{
DynInstPtr inst = NULL;
while (!insts[tid].empty()) {
inst = insts[tid].front();
insts[tid].pop();
DPRINTF(IEW,"[tid:%i]: Inserting [sn:%lli] PC:%s into "
"dispatch skidBuffer %i\n",tid, inst->seqNum,
inst->pcState(),tid);
skidBuffer[tid].push(inst);
}
assert(skidBuffer[tid].size() <= skidBufferMax &&
"Skidbuffer Exceeded Max Size");
}
template<class Impl>
int
DefaultIEW<Impl>::skidCount()
{
int max=0;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
unsigned thread_count = skidBuffer[tid].size();
if (max < thread_count)
max = thread_count;
}
return max;
}
template<class Impl>
bool
DefaultIEW<Impl>::skidsEmpty()
{
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (!skidBuffer[tid].empty())
return false;
}
return true;
}
template <class Impl>
void
DefaultIEW<Impl>::updateStatus()
{
bool any_unblocking = false;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (dispatchStatus[tid] == Unblocking) {
any_unblocking = true;
break;
}
}
// If there are no ready instructions waiting to be scheduled by the IQ,
// and there's no stores waiting to write back, and dispatch is not
// unblocking, then there is no internal activity for the IEW stage.
instQueue.intInstQueueReads++;
if (_status == Active && !instQueue.hasReadyInsts() &&
!ldstQueue.willWB() && !any_unblocking) {
DPRINTF(IEW, "IEW switching to idle\n");
deactivateStage();
_status = Inactive;
} else if (_status == Inactive && (instQueue.hasReadyInsts() ||
ldstQueue.willWB() ||
any_unblocking)) {
// Otherwise there is internal activity. Set to active.
DPRINTF(IEW, "IEW switching to active\n");
activateStage();
_status = Active;
}
}
template <class Impl>
void
DefaultIEW<Impl>::resetEntries()
{
instQueue.resetEntries();
ldstQueue.resetEntries();
}
template <class Impl>
bool
DefaultIEW<Impl>::checkStall(ThreadID tid)
{
bool ret_val(false);
if (fromCommit->commitInfo[tid].robSquashing) {
DPRINTF(IEW,"[tid:%i]: Stall from Commit stage detected.\n",tid);
ret_val = true;
} else if (instQueue.isFull(tid)) {
DPRINTF(IEW,"[tid:%i]: Stall: IQ is full.\n",tid);
ret_val = true;
}
return ret_val;
}
template <class Impl>
void
DefaultIEW<Impl>::checkSignalsAndUpdate(ThreadID tid)
{
// Check if there's a squash signal, squash if there is
// Check stall signals, block if there is.
// If status was Blocked
// if so then go to unblocking
// If status was Squashing
// check if squashing is not high. Switch to running this cycle.
if (fromCommit->commitInfo[tid].squash) {
squash(tid);
if (dispatchStatus[tid] == Blocked ||
dispatchStatus[tid] == Unblocking) {
toRename->iewUnblock[tid] = true;
wroteToTimeBuffer = true;
}
dispatchStatus[tid] = Squashing;
fetchRedirect[tid] = false;
return;
}
if (fromCommit->commitInfo[tid].robSquashing) {
DPRINTF(IEW, "[tid:%i]: ROB is still squashing.\n", tid);
dispatchStatus[tid] = Squashing;
emptyRenameInsts(tid);
wroteToTimeBuffer = true;
}
if (checkStall(tid)) {
block(tid);
dispatchStatus[tid] = Blocked;
return;
}
if (dispatchStatus[tid] == Blocked) {
// Status from previous cycle was blocked, but there are no more stall
// conditions. Switch over to unblocking.
DPRINTF(IEW, "[tid:%i]: Done blocking, switching to unblocking.\n",
tid);
dispatchStatus[tid] = Unblocking;
unblock(tid);
return;
}
if (dispatchStatus[tid] == Squashing) {
// Switch status to running if rename isn't being told to block or
// squash this cycle.
DPRINTF(IEW, "[tid:%i]: Done squashing, switching to running.\n",
tid);
dispatchStatus[tid] = Running;
return;
}
}
template <class Impl>
void
DefaultIEW<Impl>::sortInsts()
{
int insts_from_rename = fromRename->size;
#ifdef DEBUG
for (ThreadID tid = 0; tid < numThreads; tid++)
assert(insts[tid].empty());
#endif
for (int i = 0; i < insts_from_rename; ++i) {
insts[fromRename->insts[i]->threadNumber].push(fromRename->insts[i]);
}
}
template <class Impl>
void
DefaultIEW<Impl>::emptyRenameInsts(ThreadID tid)
{
DPRINTF(IEW, "[tid:%i]: Removing incoming rename instructions\n", tid);
while (!insts[tid].empty()) {
if (insts[tid].front()->isLoad()) {
toRename->iewInfo[tid].dispatchedToLQ++;
}
if (insts[tid].front()->isStore()) {
toRename->iewInfo[tid].dispatchedToSQ++;
}
toRename->iewInfo[tid].dispatched++;
insts[tid].pop();
}
}
template <class Impl>
void
DefaultIEW<Impl>::wakeCPU()
{
cpu->wakeCPU();
}
template <class Impl>
void
DefaultIEW<Impl>::activityThisCycle()
{
DPRINTF(Activity, "Activity this cycle.\n");
cpu->activityThisCycle();
}
template <class Impl>
inline void
DefaultIEW<Impl>::activateStage()
{
DPRINTF(Activity, "Activating stage.\n");
cpu->activateStage(O3CPU::IEWIdx);
}
template <class Impl>
inline void
DefaultIEW<Impl>::deactivateStage()
{
DPRINTF(Activity, "Deactivating stage.\n");
cpu->deactivateStage(O3CPU::IEWIdx);
}
template<class Impl>
void
DefaultIEW<Impl>::dispatch(ThreadID tid)
{
// If status is Running or idle,
// call dispatchInsts()
// If status is Unblocking,
// buffer any instructions coming from rename
// continue trying to empty skid buffer
// check if stall conditions have passed
if (dispatchStatus[tid] == Blocked) {
++iewBlockCycles;
} else if (dispatchStatus[tid] == Squashing) {
++iewSquashCycles;
}
// Dispatch should try to dispatch as many instructions as its bandwidth
// will allow, as long as it is not currently blocked.
if (dispatchStatus[tid] == Running ||
dispatchStatus[tid] == Idle) {
DPRINTF(IEW, "[tid:%i] Not blocked, so attempting to run "
"dispatch.\n", tid);
dispatchInsts(tid);
} else if (dispatchStatus[tid] == Unblocking) {
// Make sure that the skid buffer has something in it if the
// status is unblocking.
assert(!skidsEmpty());
// If the status was unblocking, then instructions from the skid
// buffer were used. Remove those instructions and handle
// the rest of unblocking.
dispatchInsts(tid);
++iewUnblockCycles;
if (validInstsFromRename()) {
// Add the current inputs to the skid buffer so they can be
// reprocessed when this stage unblocks.
skidInsert(tid);
}
unblock(tid);
}
}
template <class Impl>
void
DefaultIEW<Impl>::dispatchInsts(ThreadID tid)
{
// Obtain instructions from skid buffer if unblocking, or queue from rename
// otherwise.
std::queue<DynInstPtr> &insts_to_dispatch =
dispatchStatus[tid] == Unblocking ?
skidBuffer[tid] : insts[tid];
int insts_to_add = insts_to_dispatch.size();
DynInstPtr inst;
bool add_to_iq = false;
int dis_num_inst = 0;
// Loop through the instructions, putting them in the instruction
// queue.
for ( ; dis_num_inst < insts_to_add &&
dis_num_inst < dispatchWidth;
++dis_num_inst)
{
inst = insts_to_dispatch.front();
if (dispatchStatus[tid] == Unblocking) {
DPRINTF(IEW, "[tid:%i]: Issue: Examining instruction from skid "
"buffer\n", tid);
}
// Make sure there's a valid instruction there.
assert(inst);
DPRINTF(IEW, "[tid:%i]: Issue: Adding PC %s [sn:%lli] [tid:%i] to "
"IQ.\n",
tid, inst->pcState(), inst->seqNum, inst->threadNumber);
// Be sure to mark these instructions as ready so that the
// commit stage can go ahead and execute them, and mark
// them as issued so the IQ doesn't reprocess them.
// Check for squashed instructions.
if (inst->isSquashed()) {
DPRINTF(IEW, "[tid:%i]: Issue: Squashed instruction encountered, "
"not adding to IQ.\n", tid);
++iewDispSquashedInsts;
insts_to_dispatch.pop();
//Tell Rename That An Instruction has been processed
if (inst->isLoad()) {
toRename->iewInfo[tid].dispatchedToLQ++;
}
if (inst->isStore()) {
toRename->iewInfo[tid].dispatchedToSQ++;
}
toRename->iewInfo[tid].dispatched++;
continue;
}
// Check for full conditions.
if (instQueue.isFull(tid)) {
DPRINTF(IEW, "[tid:%i]: Issue: IQ has become full.\n", tid);
// Call function to start blocking.
block(tid);
// Set unblock to false. Special case where we are using
// skidbuffer (unblocking) instructions but then we still
// get full in the IQ.
toRename->iewUnblock[tid] = false;
++iewIQFullEvents;
break;
}
// Check LSQ if inst is LD/ST
if ((inst->isLoad() && ldstQueue.lqFull(tid)) ||
(inst->isStore() && ldstQueue.sqFull(tid))) {
DPRINTF(IEW, "[tid:%i]: Issue: %s has become full.\n",tid,
inst->isLoad() ? "LQ" : "SQ");
// Call function to start blocking.
block(tid);
// Set unblock to false. Special case where we are using
// skidbuffer (unblocking) instructions but then we still
// get full in the IQ.
toRename->iewUnblock[tid] = false;
++iewLSQFullEvents;
break;
}
// Otherwise issue the instruction just fine.
if (inst->isLoad()) {
DPRINTF(IEW, "[tid:%i]: Issue: Memory instruction "
"encountered, adding to LSQ.\n", tid);
// Reserve a spot in the load store queue for this
// memory access.
ldstQueue.insertLoad(inst);
++iewDispLoadInsts;
add_to_iq = true;
toRename->iewInfo[tid].dispatchedToLQ++;
} else if (inst->isStore()) {
DPRINTF(IEW, "[tid:%i]: Issue: Memory instruction "
"encountered, adding to LSQ.\n", tid);
ldstQueue.insertStore(inst);
++iewDispStoreInsts;
if (inst->isStoreConditional()) {
// Store conditionals need to be set as "canCommit()"
// so that commit can process them when they reach the
// head of commit.
// @todo: This is somewhat specific to Alpha.
inst->setCanCommit();
instQueue.insertNonSpec(inst);
add_to_iq = false;
++iewDispNonSpecInsts;
} else {
add_to_iq = true;
}
toRename->iewInfo[tid].dispatchedToSQ++;
} else if (inst->isMemBarrier() || inst->isWriteBarrier()) {
// Same as non-speculative stores.
inst->setCanCommit();
instQueue.insertBarrier(inst);
add_to_iq = false;
} else if (inst->isNop()) {
DPRINTF(IEW, "[tid:%i]: Issue: Nop instruction encountered, "
"skipping.\n", tid);
inst->setIssued();
inst->setExecuted();
inst->setCanCommit();
instQueue.recordProducer(inst);
iewExecutedNop[tid]++;
add_to_iq = false;
} else {
assert(!inst->isExecuted());
add_to_iq = true;
}
if (inst->isNonSpeculative()) {
DPRINTF(IEW, "[tid:%i]: Issue: Nonspeculative instruction "
"encountered, skipping.\n", tid);
// Same as non-speculative stores.
inst->setCanCommit();
// Specifically insert it as nonspeculative.
instQueue.insertNonSpec(inst);
++iewDispNonSpecInsts;
add_to_iq = false;
}
// If the instruction queue is not full, then add the
// instruction.
if (add_to_iq) {
instQueue.insert(inst);
}
insts_to_dispatch.pop();
toRename->iewInfo[tid].dispatched++;
++iewDispatchedInsts;
#if TRACING_ON
inst->dispatchTick = curTick() - inst->fetchTick;
#endif
ppDispatch->notify(inst);
}
if (!insts_to_dispatch.empty()) {
DPRINTF(IEW,"[tid:%i]: Issue: Bandwidth Full. Blocking.\n", tid);
block(tid);
toRename->iewUnblock[tid] = false;
}
if (dispatchStatus[tid] == Idle && dis_num_inst) {
dispatchStatus[tid] = Running;
updatedQueues = true;
}
dis_num_inst = 0;
}
template <class Impl>
void
DefaultIEW<Impl>::printAvailableInsts()
{
int inst = 0;
std::cout << "Available Instructions: ";
while (fromIssue->insts[inst]) {
if (inst%3==0) std::cout << "\n\t";
std::cout << "PC: " << fromIssue->insts[inst]->pcState()
<< " TN: " << fromIssue->insts[inst]->threadNumber
<< " SN: " << fromIssue->insts[inst]->seqNum << " | ";
inst++;
}
std::cout << "\n";
}
template <class Impl>
void
DefaultIEW<Impl>::executeInsts()
{
wbNumInst = 0;
wbCycle = 0;
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
fetchRedirect[tid] = false;
}
// Uncomment this if you want to see all available instructions.
// @todo This doesn't actually work anymore, we should fix it.
// printAvailableInsts();
// Execute/writeback any instructions that are available.
int insts_to_execute = fromIssue->size;
int inst_num = 0;
for (; inst_num < insts_to_execute;
++inst_num) {
DPRINTF(IEW, "Execute: Executing instructions from IQ.\n");
DynInstPtr inst = instQueue.getInstToExecute();
DPRINTF(IEW, "Execute: Processing PC %s, [tid:%i] [sn:%i].\n",
inst->pcState(), inst->threadNumber,inst->seqNum);
// Notify potential listeners that this instruction has started
// executing
ppExecute->notify(inst);
// Check if the instruction is squashed; if so then skip it
if (inst->isSquashed()) {
DPRINTF(IEW, "Execute: Instruction was squashed. PC: %s, [tid:%i]"
" [sn:%i]\n", inst->pcState(), inst->threadNumber,
inst->seqNum);
// Consider this instruction executed so that commit can go
// ahead and retire the instruction.
inst->setExecuted();
// Not sure if I should set this here or just let commit try to
// commit any squashed instructions. I like the latter a bit more.
inst->setCanCommit();
++iewExecSquashedInsts;
continue;
}
Fault fault = NoFault;
// Execute instruction.
// Note that if the instruction faults, it will be handled
// at the commit stage.
if (inst->isMemRef()) {
DPRINTF(IEW, "Execute: Calculating address for memory "
"reference.\n");
// Tell the LDSTQ to execute this instruction (if it is a load).
if (inst->isLoad()) {
// Loads will mark themselves as executed, and their writeback
// event adds the instruction to the queue to commit
fault = ldstQueue.executeLoad(inst);
if (inst->isTranslationDelayed() &&
fault == NoFault) {
// A hw page table walk is currently going on; the
// instruction must be deferred.
DPRINTF(IEW, "Execute: Delayed translation, deferring "
"load.\n");
instQueue.deferMemInst(inst);
continue;
}
if (inst->isDataPrefetch() || inst->isInstPrefetch()) {
inst->fault = NoFault;
}
} else if (inst->isStore()) {
fault = ldstQueue.executeStore(inst);
if (inst->isTranslationDelayed() &&
fault == NoFault) {
// A hw page table walk is currently going on; the
// instruction must be deferred.
DPRINTF(IEW, "Execute: Delayed translation, deferring "
"store.\n");
instQueue.deferMemInst(inst);
continue;
}
// If the store had a fault then it may not have a mem req
if (fault != NoFault || !inst->readPredicate() ||
!inst->isStoreConditional()) {
// If the instruction faulted, then we need to send it along
// to commit without the instruction completing.
// Send this instruction to commit, also make sure iew stage
// realizes there is activity.
inst->setExecuted();
instToCommit(inst);
activityThisCycle();
}
// Store conditionals will mark themselves as
// executed, and their writeback event will add the
// instruction to the queue to commit.
} else {
panic("Unexpected memory type!\n");
}
} else {
// If the instruction has already faulted, then skip executing it.
// Such case can happen when it faulted during ITLB translation.
// If we execute the instruction (even if it's a nop) the fault
// will be replaced and we will lose it.
if (inst->getFault() == NoFault) {
inst->execute();
if (!inst->readPredicate())
inst->forwardOldRegs();
}
inst->setExecuted();
instToCommit(inst);
}
updateExeInstStats(inst);
// Check if branch prediction was correct, if not then we need
// to tell commit to squash in flight instructions. Only
// handle this if there hasn't already been something that
// redirects fetch in this group of instructions.
// This probably needs to prioritize the redirects if a different
// scheduler is used. Currently the scheduler schedules the oldest
// instruction first, so the branch resolution order will be correct.
ThreadID tid = inst->threadNumber;
if (!fetchRedirect[tid] ||
!toCommit->squash[tid] ||
toCommit->squashedSeqNum[tid] > inst->seqNum) {
// Prevent testing for misprediction on load instructions,
// that have not been executed.
bool loadNotExecuted = !inst->isExecuted() && inst->isLoad();
if (inst->mispredicted() && !loadNotExecuted) {
fetchRedirect[tid] = true;
DPRINTF(IEW, "Execute: Branch mispredict detected.\n");
DPRINTF(IEW, "Predicted target was PC: %s.\n",
inst->readPredTarg());
DPRINTF(IEW, "Execute: Redirecting fetch to PC: %s.\n",
inst->pcState());
// If incorrect, then signal the ROB that it must be squashed.
squashDueToBranch(inst, tid);
ppMispredict->notify(inst);
if (inst->readPredTaken()) {
predictedTakenIncorrect++;
} else {
predictedNotTakenIncorrect++;
}
} else if (ldstQueue.violation(tid)) {
assert(inst->isMemRef());
// If there was an ordering violation, then get the
// DynInst that caused the violation. Note that this
// clears the violation signal.
DynInstPtr violator;
violator = ldstQueue.getMemDepViolator(tid);
DPRINTF(IEW, "LDSTQ detected a violation. Violator PC: %s "
"[sn:%lli], inst PC: %s [sn:%lli]. Addr is: %#x.\n",
violator->pcState(), violator->seqNum,
inst->pcState(), inst->seqNum, inst->physEffAddrLow);
fetchRedirect[tid] = true;
// Tell the instruction queue that a violation has occured.
instQueue.violation(inst, violator);
// Squash.
squashDueToMemOrder(violator, tid);
++memOrderViolationEvents;
}
} else {
// Reset any state associated with redirects that will not
// be used.
if (ldstQueue.violation(tid)) {
assert(inst->isMemRef());
DynInstPtr violator = ldstQueue.getMemDepViolator(tid);
DPRINTF(IEW, "LDSTQ detected a violation. Violator PC: "
"%s, inst PC: %s. Addr is: %#x.\n",
violator->pcState(), inst->pcState(),
inst->physEffAddrLow);
DPRINTF(IEW, "Violation will not be handled because "
"already squashing\n");
++memOrderViolationEvents;
}
}
}
// Update and record activity if we processed any instructions.
if (inst_num) {
if (exeStatus == Idle) {
exeStatus = Running;
}
updatedQueues = true;
cpu->activityThisCycle();
}
// Need to reset this in case a writeback event needs to write into the
// iew queue. That way the writeback event will write into the correct
// spot in the queue.
wbNumInst = 0;
}
template <class Impl>
void
DefaultIEW<Impl>::writebackInsts()
{
// Loop through the head of the time buffer and wake any
// dependents. These instructions are about to write back. Also
// mark scoreboard that this instruction is finally complete.
// Either have IEW have direct access to scoreboard, or have this
// as part of backwards communication.
for (int inst_num = 0; inst_num < wbWidth &&
toCommit->insts[inst_num]; inst_num++) {
DynInstPtr inst = toCommit->insts[inst_num];
ThreadID tid = inst->threadNumber;
DPRINTF(IEW, "Sending instructions to commit, [sn:%lli] PC %s.\n",
inst->seqNum, inst->pcState());
iewInstsToCommit[tid]++;
// Notify potential listeners that execution is complete for this
// instruction.
ppToCommit->notify(inst);
// Some instructions will be sent to commit without having
// executed because they need commit to handle them.
// E.g. Strictly ordered loads have not actually executed when they
// are first sent to commit. Instead commit must tell the LSQ
// when it's ready to execute the strictly ordered load.
if (!inst->isSquashed() && inst->isExecuted() && inst->getFault() == NoFault) {
int dependents = instQueue.wakeDependents(inst);
for (int i = 0; i < inst->numDestRegs(); i++) {
//mark as Ready
DPRINTF(IEW,"Setting Destination Register %i\n",
inst->renamedDestRegIdx(i));
scoreboard->setReg(inst->renamedDestRegIdx(i));
}
if (dependents) {
producerInst[tid]++;
consumerInst[tid]+= dependents;
}
writebackCount[tid]++;
}
}
}
template<class Impl>
void
DefaultIEW<Impl>::tick()
{
wbNumInst = 0;
wbCycle = 0;
wroteToTimeBuffer = false;
updatedQueues = false;
sortInsts();
// Free function units marked as being freed this cycle.
fuPool->processFreeUnits();
list<ThreadID>::iterator threads = activeThreads->begin();
list<ThreadID>::iterator end = activeThreads->end();
// Check stall and squash signals, dispatch any instructions.
while (threads != end) {
ThreadID tid = *threads++;
DPRINTF(IEW,"Issue: Processing [tid:%i]\n",tid);
checkSignalsAndUpdate(tid);
dispatch(tid);
}
if (exeStatus != Squashing) {
executeInsts();
writebackInsts();
// Have the instruction queue try to schedule any ready instructions.
// (In actuality, this scheduling is for instructions that will
// be executed next cycle.)
instQueue.scheduleReadyInsts();
// Also should advance its own time buffers if the stage ran.
// Not the best place for it, but this works (hopefully).
issueToExecQueue.advance();
}
bool broadcast_free_entries = false;
if (updatedQueues || exeStatus == Running || updateLSQNextCycle) {
exeStatus = Idle;
updateLSQNextCycle = false;
broadcast_free_entries = true;
}
// Writeback any stores using any leftover bandwidth.
ldstQueue.writebackStores();
// Check the committed load/store signals to see if there's a load
// or store to commit. Also check if it's being told to execute a
// nonspeculative instruction.
// This is pretty inefficient...
threads = activeThreads->begin();
while (threads != end) {
ThreadID tid = (*threads++);
DPRINTF(IEW,"Processing [tid:%i]\n",tid);
// Update structures based on instructions committed.
if (fromCommit->commitInfo[tid].doneSeqNum != 0 &&
!fromCommit->commitInfo[tid].squash &&
!fromCommit->commitInfo[tid].robSquashing) {
ldstQueue.commitStores(fromCommit->commitInfo[tid].doneSeqNum,tid);
ldstQueue.commitLoads(fromCommit->commitInfo[tid].doneSeqNum,tid);
updateLSQNextCycle = true;
instQueue.commit(fromCommit->commitInfo[tid].doneSeqNum,tid);
}
if (fromCommit->commitInfo[tid].nonSpecSeqNum != 0) {
//DPRINTF(IEW,"NonspecInst from thread %i",tid);
if (fromCommit->commitInfo[tid].strictlyOrdered) {
instQueue.replayMemInst(
fromCommit->commitInfo[tid].strictlyOrderedLoad);
fromCommit->commitInfo[tid].strictlyOrderedLoad->setAtCommit();
} else {
instQueue.scheduleNonSpec(
fromCommit->commitInfo[tid].nonSpecSeqNum);
}
}
if (broadcast_free_entries) {
toFetch->iewInfo[tid].iqCount =
instQueue.getCount(tid);
toFetch->iewInfo[tid].ldstqCount =
ldstQueue.getCount(tid);
toRename->iewInfo[tid].usedIQ = true;
toRename->iewInfo[tid].freeIQEntries =
instQueue.numFreeEntries(tid);
toRename->iewInfo[tid].usedLSQ = true;
toRename->iewInfo[tid].freeLQEntries =
ldstQueue.numFreeLoadEntries(tid);
toRename->iewInfo[tid].freeSQEntries =
ldstQueue.numFreeStoreEntries(tid);
wroteToTimeBuffer = true;
}
DPRINTF(IEW, "[tid:%i], Dispatch dispatched %i instructions.\n",
tid, toRename->iewInfo[tid].dispatched);
}
DPRINTF(IEW, "IQ has %i free entries (Can schedule: %i). "
"LQ has %i free entries. SQ has %i free entries.\n",
instQueue.numFreeEntries(), instQueue.hasReadyInsts(),
ldstQueue.numFreeLoadEntries(), ldstQueue.numFreeStoreEntries());
updateStatus();
if (wroteToTimeBuffer) {
DPRINTF(Activity, "Activity this cycle.\n");
cpu->activityThisCycle();
}
}
template <class Impl>
void
DefaultIEW<Impl>::updateExeInstStats(DynInstPtr &inst)
{
ThreadID tid = inst->threadNumber;
iewExecutedInsts++;
#if TRACING_ON
if (DTRACE(O3PipeView)) {
inst->completeTick = curTick() - inst->fetchTick;
}
#endif
//
// Control operations
//
if (inst->isControl())
iewExecutedBranches[tid]++;
//
// Memory operations
//
if (inst->isMemRef()) {
iewExecutedRefs[tid]++;
if (inst->isLoad()) {
iewExecLoadInsts[tid]++;
}
}
}
template <class Impl>
void
DefaultIEW<Impl>::checkMisprediction(DynInstPtr &inst)
{
ThreadID tid = inst->threadNumber;
if (!fetchRedirect[tid] ||
!toCommit->squash[tid] ||
toCommit->squashedSeqNum[tid] > inst->seqNum) {
if (inst->mispredicted()) {
fetchRedirect[tid] = true;
DPRINTF(IEW, "Execute: Branch mispredict detected.\n");
DPRINTF(IEW, "Predicted target was PC:%#x, NPC:%#x.\n",
inst->predInstAddr(), inst->predNextInstAddr());
DPRINTF(IEW, "Execute: Redirecting fetch to PC: %#x,"
" NPC: %#x.\n", inst->nextInstAddr(),
inst->nextInstAddr());
// If incorrect, then signal the ROB that it must be squashed.
squashDueToBranch(inst, tid);
if (inst->readPredTaken()) {
predictedTakenIncorrect++;
} else {
predictedNotTakenIncorrect++;
}
}
}
}
#endif//__CPU_O3_IEW_IMPL_IMPL_HH__
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