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+/*
+ * 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
+ */
+
+#include "cpu/o3/decode.hh"
+
+template<class Impl>
+DefaultDecode<Impl>::DefaultDecode(Params *params)
+ : renameToDecodeDelay(params->renameToDecodeDelay),
+ iewToDecodeDelay(params->iewToDecodeDelay),
+ commitToDecodeDelay(params->commitToDecodeDelay),
+ fetchToDecodeDelay(params->fetchToDecodeDelay),
+ decodeWidth(params->decodeWidth),
+ numThreads(params->numberOfThreads)
+{
+ _status = Inactive;
+
+ // Setup status, make sure stall signals are clear.
+ for (int i = 0; i < numThreads; ++i) {
+ decodeStatus[i] = Idle;
+
+ stalls[i].rename = false;
+ stalls[i].iew = false;
+ stalls[i].commit = false;
+
+ squashAfterDelaySlot[i] = false;
+ }
+
+ // @todo: Make into a parameter
+ skidBufferMax = (fetchToDecodeDelay * params->fetchWidth) + decodeWidth;
+}
+
+template <class Impl>
+std::string
+DefaultDecode<Impl>::name() const
+{
+ return cpu->name() + ".decode";
+}
+
+template <class Impl>
+void
+DefaultDecode<Impl>::regStats()
+{
+ decodeIdleCycles
+ .name(name() + ".DECODE:IdleCycles")
+ .desc("Number of cycles decode is idle")
+ .prereq(decodeIdleCycles);
+ decodeBlockedCycles
+ .name(name() + ".DECODE:BlockedCycles")
+ .desc("Number of cycles decode is blocked")
+ .prereq(decodeBlockedCycles);
+ decodeRunCycles
+ .name(name() + ".DECODE:RunCycles")
+ .desc("Number of cycles decode is running")
+ .prereq(decodeRunCycles);
+ decodeUnblockCycles
+ .name(name() + ".DECODE:UnblockCycles")
+ .desc("Number of cycles decode is unblocking")
+ .prereq(decodeUnblockCycles);
+ decodeSquashCycles
+ .name(name() + ".DECODE:SquashCycles")
+ .desc("Number of cycles decode is squashing")
+ .prereq(decodeSquashCycles);
+ decodeBranchResolved
+ .name(name() + ".DECODE:BranchResolved")
+ .desc("Number of times decode resolved a branch")
+ .prereq(decodeBranchResolved);
+ decodeBranchMispred
+ .name(name() + ".DECODE:BranchMispred")
+ .desc("Number of times decode detected a branch misprediction")
+ .prereq(decodeBranchMispred);
+ decodeControlMispred
+ .name(name() + ".DECODE:ControlMispred")
+ .desc("Number of times decode detected an instruction incorrectly"
+ " predicted as a control")
+ .prereq(decodeControlMispred);
+ decodeDecodedInsts
+ .name(name() + ".DECODE:DecodedInsts")
+ .desc("Number of instructions handled by decode")
+ .prereq(decodeDecodedInsts);
+ decodeSquashedInsts
+ .name(name() + ".DECODE:SquashedInsts")
+ .desc("Number of squashed instructions handled by decode")
+ .prereq(decodeSquashedInsts);
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::setCPU(O3CPU *cpu_ptr)
+{
+ DPRINTF(Decode, "Setting CPU pointer.\n");
+ cpu = cpu_ptr;
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr)
+{
+ DPRINTF(Decode, "Setting time buffer pointer.\n");
+ timeBuffer = tb_ptr;
+
+ // Setup wire to write information back to fetch.
+ toFetch = timeBuffer->getWire(0);
+
+ // Create wires to get information from proper places in time buffer.
+ fromRename = timeBuffer->getWire(-renameToDecodeDelay);
+ fromIEW = timeBuffer->getWire(-iewToDecodeDelay);
+ fromCommit = timeBuffer->getWire(-commitToDecodeDelay);
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr)
+{
+ DPRINTF(Decode, "Setting decode queue pointer.\n");
+ decodeQueue = dq_ptr;
+
+ // Setup wire to write information to proper place in decode queue.
+ toRename = decodeQueue->getWire(0);
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr)
+{
+ DPRINTF(Decode, "Setting fetch queue pointer.\n");
+ fetchQueue = fq_ptr;
+
+ // Setup wire to read information from fetch queue.
+ fromFetch = fetchQueue->getWire(-fetchToDecodeDelay);
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::setActiveThreads(std::list<unsigned> *at_ptr)
+{
+ DPRINTF(Decode, "Setting active threads list pointer.\n");
+ activeThreads = at_ptr;
+}
+
+template <class Impl>
+bool
+DefaultDecode<Impl>::drain()
+{
+ // Decode is done draining at any time.
+ cpu->signalDrained();
+ return true;
+}
+
+template <class Impl>
+void
+DefaultDecode<Impl>::takeOverFrom()
+{
+ _status = Inactive;
+
+ // Be sure to reset state and clear out any old instructions.
+ for (int i = 0; i < numThreads; ++i) {
+ decodeStatus[i] = Idle;
+
+ stalls[i].rename = false;
+ stalls[i].iew = false;
+ stalls[i].commit = false;
+ while (!insts[i].empty())
+ insts[i].pop();
+ while (!skidBuffer[i].empty())
+ skidBuffer[i].pop();
+ branchCount[i] = 0;
+ }
+ wroteToTimeBuffer = false;
+}
+
+template<class Impl>
+bool
+DefaultDecode<Impl>::checkStall(unsigned tid) const
+{
+ bool ret_val = false;
+
+ if (stalls[tid].rename) {
+ DPRINTF(Decode,"[tid:%i]: Stall fom Rename stage detected.\n", tid);
+ ret_val = true;
+ } else if (stalls[tid].iew) {
+ DPRINTF(Decode,"[tid:%i]: Stall fom IEW stage detected.\n", tid);
+ ret_val = true;
+ } else if (stalls[tid].commit) {
+ DPRINTF(Decode,"[tid:%i]: Stall fom Commit stage detected.\n", tid);
+ ret_val = true;
+ }
+
+ return ret_val;
+}
+
+template<class Impl>
+inline bool
+DefaultDecode<Impl>::fetchInstsValid()
+{
+ return fromFetch->size > 0;
+}
+
+template<class Impl>
+bool
+DefaultDecode<Impl>::block(unsigned tid)
+{
+ DPRINTF(Decode, "[tid:%u]: Blocking.\n", tid);
+
+ // Add the current inputs to the skid buffer so they can be
+ // reprocessed when this stage unblocks.
+ skidInsert(tid);
+
+ // If the decode status is blocked or unblocking then decode has not yet
+ // signalled fetch to unblock. In that case, there is no need to tell
+ // fetch to block.
+ if (decodeStatus[tid] != Blocked) {
+ // Set the status to Blocked.
+ decodeStatus[tid] = Blocked;
+
+ if (decodeStatus[tid] != Unblocking) {
+ toFetch->decodeBlock[tid] = true;
+ wroteToTimeBuffer = true;
+ }
+
+ return true;
+ }
+
+ return false;
+}
+
+template<class Impl>
+bool
+DefaultDecode<Impl>::unblock(unsigned tid)
+{
+ // Decode is done unblocking only if the skid buffer is empty.
+ if (skidBuffer[tid].empty()) {
+ DPRINTF(Decode, "[tid:%u]: Done unblocking.\n", tid);
+ toFetch->decodeUnblock[tid] = true;
+ wroteToTimeBuffer = true;
+
+ decodeStatus[tid] = Running;
+ return true;
+ }
+
+ DPRINTF(Decode, "[tid:%u]: Currently unblocking.\n", tid);
+
+ return false;
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::squash(DynInstPtr &inst, unsigned tid)
+{
+ DPRINTF(Decode, "[tid:%i]: Squashing due to incorrect branch prediction "
+ "detected at decode.\n", tid);
+
+ // Send back mispredict information.
+ toFetch->decodeInfo[tid].branchMispredict = true;
+ toFetch->decodeInfo[tid].predIncorrect = true;
+ toFetch->decodeInfo[tid].doneSeqNum = inst->seqNum;
+ toFetch->decodeInfo[tid].squash = true;
+ toFetch->decodeInfo[tid].nextPC = inst->branchTarget();
+#if ISA_HAS_DELAY_SLOT
+ toFetch->decodeInfo[tid].branchTaken = inst->readNextNPC() !=
+ (inst->readNextPC() + sizeof(TheISA::MachInst));
+
+ toFetch->decodeInfo[tid].bdelayDoneSeqNum = bdelayDoneSeqNum[tid];
+ squashAfterDelaySlot[tid] = false;
+
+ InstSeqNum squash_seq_num = bdelayDoneSeqNum[tid];
+#else
+ toFetch->decodeInfo[tid].branchTaken =
+ inst->readNextPC() != (inst->readPC() + sizeof(TheISA::MachInst));
+
+ InstSeqNum squash_seq_num = inst->seqNum;
+#endif
+
+ // Might have to tell fetch to unblock.
+ if (decodeStatus[tid] == Blocked ||
+ decodeStatus[tid] == Unblocking) {
+ toFetch->decodeUnblock[tid] = 1;
+ }
+
+ // Set status to squashing.
+ decodeStatus[tid] = Squashing;
+
+ for (int i=0; i<fromFetch->size; i++) {
+ if (fromFetch->insts[i]->threadNumber == tid &&
+ fromFetch->insts[i]->seqNum > squash_seq_num) {
+ fromFetch->insts[i]->setSquashed();
+ }
+ }
+
+ // Clear the instruction list and skid buffer in case they have any
+ // insts in them.
+ while (!insts[tid].empty()) {
+
+#if ISA_HAS_DELAY_SLOT
+ if (insts[tid].front()->seqNum <= squash_seq_num) {
+ DPRINTF(Decode, "[tid:%i]: Cannot remove incoming decode "
+ "instructions before delay slot [sn:%i]. %i insts"
+ "left in decode.\n", tid, squash_seq_num,
+ insts[tid].size());
+ break;
+ }
+#endif
+ insts[tid].pop();
+ }
+
+ while (!skidBuffer[tid].empty()) {
+
+#if ISA_HAS_DELAY_SLOT
+ if (skidBuffer[tid].front()->seqNum <= squash_seq_num) {
+ DPRINTF(Decode, "[tid:%i]: Cannot remove skidBuffer "
+ "instructions before delay slot [sn:%i]. %i insts"
+ "left in decode.\n", tid, squash_seq_num,
+ insts[tid].size());
+ break;
+ }
+#endif
+ skidBuffer[tid].pop();
+ }
+
+ // Squash instructions up until this one
+ cpu->removeInstsUntil(squash_seq_num, tid);
+}
+
+template<class Impl>
+unsigned
+DefaultDecode<Impl>::squash(unsigned tid)
+{
+ DPRINTF(Decode, "[tid:%i]: Squashing.\n",tid);
+
+ if (decodeStatus[tid] == Blocked ||
+ decodeStatus[tid] == Unblocking) {
+#if !FULL_SYSTEM
+ // In syscall emulation, we can have both a block and a squash due
+ // to a syscall in the same cycle. This would cause both signals to
+ // be high. This shouldn't happen in full system.
+ // @todo: Determine if this still happens.
+ if (toFetch->decodeBlock[tid]) {
+ toFetch->decodeBlock[tid] = 0;
+ } else {
+ toFetch->decodeUnblock[tid] = 1;
+ }
+#else
+ toFetch->decodeUnblock[tid] = 1;
+#endif
+ }
+
+ // Set status to squashing.
+ decodeStatus[tid] = Squashing;
+
+ // Go through incoming instructions from fetch and squash them.
+ unsigned squash_count = 0;
+
+ for (int i=0; i<fromFetch->size; i++) {
+ if (fromFetch->insts[i]->threadNumber == tid) {
+ fromFetch->insts[i]->setSquashed();
+ squash_count++;
+ }
+ }
+
+ // Clear the instruction list and skid buffer in case they have any
+ // insts in them.
+ while (!insts[tid].empty()) {
+ insts[tid].pop();
+ }
+
+ while (!skidBuffer[tid].empty()) {
+ skidBuffer[tid].pop();
+ }
+
+ return squash_count;
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::skidInsert(unsigned tid)
+{
+ DynInstPtr inst = NULL;
+
+ while (!insts[tid].empty()) {
+ inst = insts[tid].front();
+
+ insts[tid].pop();
+
+ assert(tid == inst->threadNumber);
+
+ DPRINTF(Decode,"Inserting [sn:%lli] PC:%#x into decode skidBuffer %i\n",
+ inst->seqNum, inst->readPC(), inst->threadNumber);
+
+ skidBuffer[tid].push(inst);
+ }
+
+ // @todo: Eventually need to enforce this by not letting a thread
+ // fetch past its skidbuffer
+ assert(skidBuffer[tid].size() <= skidBufferMax);
+}
+
+template<class Impl>
+bool
+DefaultDecode<Impl>::skidsEmpty()
+{
+ std::list<unsigned>::iterator threads = (*activeThreads).begin();
+
+ while (threads != (*activeThreads).end()) {
+ if (!skidBuffer[*threads++].empty())
+ return false;
+ }
+
+ return true;
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::updateStatus()
+{
+ bool any_unblocking = false;
+
+ std::list<unsigned>::iterator threads = (*activeThreads).begin();
+
+ threads = (*activeThreads).begin();
+
+ while (threads != (*activeThreads).end()) {
+ unsigned tid = *threads++;
+
+ if (decodeStatus[tid] == Unblocking) {
+ any_unblocking = true;
+ break;
+ }
+ }
+
+ // Decode will have activity if it's unblocking.
+ if (any_unblocking) {
+ if (_status == Inactive) {
+ _status = Active;
+
+ DPRINTF(Activity, "Activating stage.\n");
+
+ cpu->activateStage(O3CPU::DecodeIdx);
+ }
+ } else {
+ // If it's not unblocking, then decode will not have any internal
+ // activity. Switch it to inactive.
+ if (_status == Active) {
+ _status = Inactive;
+ DPRINTF(Activity, "Deactivating stage.\n");
+
+ cpu->deactivateStage(O3CPU::DecodeIdx);
+ }
+ }
+}
+
+template <class Impl>
+void
+DefaultDecode<Impl>::sortInsts()
+{
+ int insts_from_fetch = fromFetch->size;
+#ifdef DEBUG
+ for (int i=0; i < numThreads; i++)
+ assert(insts[i].empty());
+#endif
+ for (int i = 0; i < insts_from_fetch; ++i) {
+ insts[fromFetch->insts[i]->threadNumber].push(fromFetch->insts[i]);
+ }
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::readStallSignals(unsigned tid)
+{
+ if (fromRename->renameBlock[tid]) {
+ stalls[tid].rename = true;
+ }
+
+ if (fromRename->renameUnblock[tid]) {
+ assert(stalls[tid].rename);
+ stalls[tid].rename = false;
+ }
+
+ if (fromIEW->iewBlock[tid]) {
+ stalls[tid].iew = true;
+ }
+
+ if (fromIEW->iewUnblock[tid]) {
+ assert(stalls[tid].iew);
+ stalls[tid].iew = false;
+ }
+
+ if (fromCommit->commitBlock[tid]) {
+ stalls[tid].commit = true;
+ }
+
+ if (fromCommit->commitUnblock[tid]) {
+ assert(stalls[tid].commit);
+ stalls[tid].commit = false;
+ }
+}
+
+template <class Impl>
+bool
+DefaultDecode<Impl>::checkSignalsAndUpdate(unsigned tid)
+{
+ // Check if there's a squash signal, squash if there is.
+ // Check stall signals, block if necessary.
+ // If status was blocked
+ // Check if stall conditions have passed
+ // if so then go to unblocking
+ // If status was Squashing
+ // check if squashing is not high. Switch to running this cycle.
+
+ // Update the per thread stall statuses.
+ readStallSignals(tid);
+
+ // Check squash signals from commit.
+ if (fromCommit->commitInfo[tid].squash) {
+
+ DPRINTF(Decode, "[tid:%u]: Squashing instructions due to squash "
+ "from commit.\n", tid);
+
+ squash(tid);
+
+ return true;
+ }
+
+ // Check ROB squash signals from commit.
+ if (fromCommit->commitInfo[tid].robSquashing) {
+ DPRINTF(Decode, "[tid:%u]: ROB is still squashing.\n", tid);
+
+ // Continue to squash.
+ decodeStatus[tid] = Squashing;
+
+ return true;
+ }
+
+ if (checkStall(tid)) {
+ return block(tid);
+ }
+
+ if (decodeStatus[tid] == Blocked) {
+ DPRINTF(Decode, "[tid:%u]: Done blocking, switching to unblocking.\n",
+ tid);
+
+ decodeStatus[tid] = Unblocking;
+
+ unblock(tid);
+
+ return true;
+ }
+
+ if (decodeStatus[tid] == Squashing) {
+ // Switch status to running if decode isn't being told to block or
+ // squash this cycle.
+ DPRINTF(Decode, "[tid:%u]: Done squashing, switching to running.\n",
+ tid);
+
+ decodeStatus[tid] = Running;
+
+ return false;
+ }
+
+ // If we've reached this point, we have not gotten any signals that
+ // cause decode to change its status. Decode remains the same as before.
+ return false;
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::tick()
+{
+ wroteToTimeBuffer = false;
+
+ bool status_change = false;
+
+ toRenameIndex = 0;
+
+ std::list<unsigned>::iterator threads = (*activeThreads).begin();
+
+ sortInsts();
+
+ //Check stall and squash signals.
+ while (threads != (*activeThreads).end()) {
+ unsigned tid = *threads++;
+
+ DPRINTF(Decode,"Processing [tid:%i]\n",tid);
+ status_change = checkSignalsAndUpdate(tid) || status_change;
+
+ decode(status_change, tid);
+ }
+
+ if (status_change) {
+ updateStatus();
+ }
+
+ if (wroteToTimeBuffer) {
+ DPRINTF(Activity, "Activity this cycle.\n");
+
+ cpu->activityThisCycle();
+ }
+}
+
+template<class Impl>
+void
+DefaultDecode<Impl>::decode(bool &status_change, unsigned tid)
+{
+ // If status is Running or idle,
+ // call decodeInsts()
+ // If status is Unblocking,
+ // buffer any instructions coming from fetch
+ // continue trying to empty skid buffer
+ // check if stall conditions have passed
+
+ if (decodeStatus[tid] == Blocked) {
+ ++decodeBlockedCycles;
+ } else if (decodeStatus[tid] == Squashing) {
+ ++decodeSquashCycles;
+ }
+
+ // Decode should try to decode as many instructions as its bandwidth
+ // will allow, as long as it is not currently blocked.
+ if (decodeStatus[tid] == Running ||
+ decodeStatus[tid] == Idle) {
+ DPRINTF(Decode, "[tid:%u]: Not blocked, so attempting to run "
+ "stage.\n",tid);
+
+ decodeInsts(tid);
+ } else if (decodeStatus[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.
+ decodeInsts(tid);
+
+ if (fetchInstsValid()) {
+ // Add the current inputs to the skid buffer so they can be
+ // reprocessed when this stage unblocks.
+ skidInsert(tid);
+ }
+
+ status_change = unblock(tid) || status_change;
+ }
+}
+
+template <class Impl>
+void
+DefaultDecode<Impl>::decodeInsts(unsigned tid)
+{
+ // Instructions can come either from the skid buffer or the list of
+ // instructions coming from fetch, depending on decode's status.
+ int insts_available = decodeStatus[tid] == Unblocking ?
+ skidBuffer[tid].size() : insts[tid].size();
+
+ if (insts_available == 0) {
+ DPRINTF(Decode, "[tid:%u] Nothing to do, breaking out"
+ " early.\n",tid);
+ // Should I change the status to idle?
+ ++decodeIdleCycles;
+ return;
+ } else if (decodeStatus[tid] == Unblocking) {
+ DPRINTF(Decode, "[tid:%u] Unblocking, removing insts from skid "
+ "buffer.\n",tid);
+ ++decodeUnblockCycles;
+ } else if (decodeStatus[tid] == Running) {
+ ++decodeRunCycles;
+ }
+
+ DynInstPtr inst;
+
+ std::queue<DynInstPtr>
+ &insts_to_decode = decodeStatus[tid] == Unblocking ?
+ skidBuffer[tid] : insts[tid];
+
+ DPRINTF(Decode, "[tid:%u]: Sending instruction to rename.\n",tid);
+
+ while (insts_available > 0 && toRenameIndex < decodeWidth) {
+ assert(!insts_to_decode.empty());
+
+ inst = insts_to_decode.front();
+
+ insts_to_decode.pop();
+
+ DPRINTF(Decode, "[tid:%u]: Processing instruction [sn:%lli] with "
+ "PC %#x\n",
+ tid, inst->seqNum, inst->readPC());
+
+ if (inst->isSquashed()) {
+ DPRINTF(Decode, "[tid:%u]: Instruction %i with PC %#x is "
+ "squashed, skipping.\n",
+ tid, inst->seqNum, inst->readPC());
+
+ ++decodeSquashedInsts;
+
+ --insts_available;
+
+ continue;
+ }
+
+ // Also check if instructions have no source registers. Mark
+ // them as ready to issue at any time. Not sure if this check
+ // should exist here or at a later stage; however it doesn't matter
+ // too much for function correctness.
+ if (inst->numSrcRegs() == 0) {
+ inst->setCanIssue();
+ }
+
+ // This current instruction is valid, so add it into the decode
+ // queue. The next instruction may not be valid, so check to
+ // see if branches were predicted correctly.
+ toRename->insts[toRenameIndex] = inst;
+
+ ++(toRename->size);
+ ++toRenameIndex;
+ ++decodeDecodedInsts;
+ --insts_available;
+
+ // Ensure that if it was predicted as a branch, it really is a
+ // branch.
+ if (inst->predTaken() && !inst->isControl()) {
+ DPRINTF(Decode, "PredPC : %#x != NextPC: %#x\n",inst->predPC,
+ inst->nextPC + 4);
+
+ panic("Instruction predicted as a branch!");
+
+ ++decodeControlMispred;
+
+ // Might want to set some sort of boolean and just do
+ // a check at the end
+ squash(inst, inst->threadNumber);
+
+ break;
+ }
+
+ // Go ahead and compute any PC-relative branches.
+ if (inst->isDirectCtrl() && inst->isUncondCtrl()) {
+ ++decodeBranchResolved;
+
+ if (inst->branchTarget() != inst->readPredTarg()) {
+ ++decodeBranchMispred;
+
+ // Might want to set some sort of boolean and just do
+ // a check at the end
+#if !ISA_HAS_DELAY_SLOT
+ squash(inst, inst->threadNumber);
+ inst->setPredTarg(inst->branchTarget());
+ break;
+#else
+ // If mispredicted as taken, then ignore delay slot
+ // instruction... else keep delay slot and squash
+ // after it is sent to rename
+ if (inst->predTaken() && inst->isCondDelaySlot()) {
+ DPRINTF(Decode, "[tid:%i]: Conditional delay slot inst."
+ "[sn:%i] PC %#x mispredicted as taken.\n", tid,
+ inst->seqNum, inst->PC);
+ bdelayDoneSeqNum[tid] = inst->seqNum;
+ squash(inst, inst->threadNumber);
+ inst->setPredTarg(inst->branchTarget());
+ break;
+ } else {
+ DPRINTF(Decode, "[tid:%i]: Misprediction detected at "
+ "[sn:%i] PC %#x, will squash after delay slot "
+ "inst. is sent to Rename\n",
+ tid, inst->seqNum, inst->PC);
+ bdelayDoneSeqNum[tid] = inst->seqNum + 1;
+ squashAfterDelaySlot[tid] = true;
+ squashInst[tid] = inst;
+ continue;
+ }
+#endif
+ }
+ }
+
+ if (squashAfterDelaySlot[tid]) {
+ assert(!inst->isSquashed());
+ squash(squashInst[tid], squashInst[tid]->threadNumber);
+ squashInst[tid]->setPredTarg(squashInst[tid]->branchTarget());
+ assert(!inst->isSquashed());
+ break;
+ }
+ }
+
+ // If we didn't process all instructions, then we will need to block
+ // and put all those instructions into the skid buffer.
+ if (!insts_to_decode.empty()) {
+ block(tid);
+ }
+
+ // Record that decode has written to the time buffer for activity
+ // tracking.
+ if (toRenameIndex) {
+ wroteToTimeBuffer = true;
+ }
+}