diff options
Diffstat (limited to 'src/cpu/o3/iew_impl.hh')
| -rw-r--r-- | src/cpu/o3/iew_impl.hh | 736 |
1 files changed, 736 insertions, 0 deletions
diff --git a/src/cpu/o3/iew_impl.hh b/src/cpu/o3/iew_impl.hh new file mode 100644 index 000000000..85217dd10 --- /dev/null +++ b/src/cpu/o3/iew_impl.hh @@ -0,0 +1,736 @@ +/* + * Copyright (c) 2004-2005 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. + */ + +// @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. +// Update the statuses for each stage. + +#include <queue> + +#include "base/timebuf.hh" +#include "cpu/o3/iew.hh" + +template<class Impl> +SimpleIEW<Impl>::WritebackEvent::WritebackEvent(DynInstPtr &_inst, + SimpleIEW<Impl> *_iew) + : Event(&mainEventQueue, CPU_Tick_Pri), inst(_inst), iewStage(_iew) +{ + this->setFlags(Event::AutoDelete); +} + +template<class Impl> +void +SimpleIEW<Impl>::WritebackEvent::process() +{ + DPRINTF(IEW, "IEW: WRITEBACK EVENT!!!!\n"); + + // Need to insert instruction into queue to commit + iewStage->instToCommit(inst); + // Need to execute second half of the instruction, do actual writing to + // registers and such + inst->execute(); +} + +template<class Impl> +const char * +SimpleIEW<Impl>::WritebackEvent::description() +{ + return "LSQ writeback event"; +} + +template<class Impl> +SimpleIEW<Impl>::SimpleIEW(Params ¶ms) + : // Just make this time buffer really big for now + issueToExecQueue(5, 5), + instQueue(params), + ldstQueue(params), + commitToIEWDelay(params.commitToIEWDelay), + renameToIEWDelay(params.renameToIEWDelay), + issueToExecuteDelay(params.issueToExecuteDelay), + issueReadWidth(params.issueWidth), + issueWidth(params.issueWidth), + executeWidth(params.executeWidth) +{ + DPRINTF(IEW, "IEW: executeIntWidth: %i.\n", params.executeIntWidth); + _status = Idle; + _issueStatus = Idle; + _exeStatus = Idle; + _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); + + ldstQueue.setIEW(this); +} + +template <class Impl> +void +SimpleIEW<Impl>::regStats() +{ + instQueue.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"); + +// iewWBInsts; + + 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"); + + iewExecutedInsts + .name(name() + ".iewExecutedInsts") + .desc("Number of executed instructions"); + + iewExecLoadInsts + .name(name() + ".iewExecLoadInsts") + .desc("Number of load instructions executed"); + + iewExecStoreInsts + .name(name() + ".iewExecStoreInsts") + .desc("Number of store instructions executed"); + + iewExecSquashedInsts + .name(name() + ".iewExecSquashedInsts") + .desc("Number of squashed instructions skipped in execute"); + + memOrderViolationEvents + .name(name() + ".memOrderViolationEvents") + .desc("Number of memory order violations"); + + predictedTakenIncorrect + .name(name() + ".predictedTakenIncorrect") + .desc("Number of branches that were predicted taken incorrectly"); +} + +template<class Impl> +void +SimpleIEW<Impl>::setCPU(FullCPU *cpu_ptr) +{ + DPRINTF(IEW, "IEW: Setting CPU pointer.\n"); + cpu = cpu_ptr; + + instQueue.setCPU(cpu_ptr); + ldstQueue.setCPU(cpu_ptr); +} + +template<class Impl> +void +SimpleIEW<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr) +{ + DPRINTF(IEW, "IEW: Setting time buffer pointer.\n"); + 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); + + // Instruction queue also needs main time buffer. + instQueue.setTimeBuffer(tb_ptr); +} + +template<class Impl> +void +SimpleIEW<Impl>::setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr) +{ + DPRINTF(IEW, "IEW: Setting rename queue pointer.\n"); + renameQueue = rq_ptr; + + // Setup wire to read information from rename queue. + fromRename = renameQueue->getWire(-renameToIEWDelay); +} + +template<class Impl> +void +SimpleIEW<Impl>::setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr) +{ + DPRINTF(IEW, "IEW: Setting IEW queue pointer.\n"); + iewQueue = iq_ptr; + + // Setup wire to write instructions to commit. + toCommit = iewQueue->getWire(0); +} + +template<class Impl> +void +SimpleIEW<Impl>::setRenameMap(RenameMap *rm_ptr) +{ + DPRINTF(IEW, "IEW: Setting rename map pointer.\n"); + renameMap = rm_ptr; +} + +template<class Impl> +void +SimpleIEW<Impl>::squash() +{ + DPRINTF(IEW, "IEW: Squashing all instructions.\n"); + _status = Squashing; + + // Tell the IQ to start squashing. + instQueue.squash(); + + // Tell the LDSTQ to start squashing. + ldstQueue.squash(fromCommit->commitInfo.doneSeqNum); +} + +template<class Impl> +void +SimpleIEW<Impl>::squashDueToBranch(DynInstPtr &inst) +{ + DPRINTF(IEW, "IEW: Squashing from a specific instruction, PC: %#x.\n", + inst->PC); + // Perhaps leave the squashing up to the ROB stage to tell it when to + // squash? + _status = Squashing; + + // Tell rename to squash through the time buffer. + toCommit->squash = true; + // Also send PC update information back to prior stages. + toCommit->squashedSeqNum = inst->seqNum; + toCommit->mispredPC = inst->readPC(); + toCommit->nextPC = inst->readNextPC(); + toCommit->branchMispredict = true; + // Prediction was incorrect, so send back inverse. + toCommit->branchTaken = inst->readNextPC() != + (inst->readPC() + sizeof(TheISA::MachInst)); +} + +template<class Impl> +void +SimpleIEW<Impl>::squashDueToMem(DynInstPtr &inst) +{ + DPRINTF(IEW, "IEW: Squashing from a specific instruction, PC: %#x.\n", + inst->PC); + // Perhaps leave the squashing up to the ROB stage to tell it when to + // squash? + _status = Squashing; + + // Tell rename to squash through the time buffer. + toCommit->squash = true; + // Also send PC update information back to prior stages. + toCommit->squashedSeqNum = inst->seqNum; + toCommit->nextPC = inst->readNextPC(); +} + +template<class Impl> +void +SimpleIEW<Impl>::block() +{ + DPRINTF(IEW, "IEW: Blocking.\n"); + // Set the status to Blocked. + _status = Blocked; + + // Add the current inputs to the skid buffer so they can be + // reprocessed when this stage unblocks. + skidBuffer.push(*fromRename); + + // Note that this stage only signals previous stages to stall when + // it is the cause of the stall originates at this stage. Otherwise + // the previous stages are expected to check all possible stall signals. +} + +template<class Impl> +inline void +SimpleIEW<Impl>::unblock() +{ + // Check if there's information in the skid buffer. If there is, then + // set status to unblocking, otherwise set it directly to running. + DPRINTF(IEW, "IEW: Reading instructions out of the skid " + "buffer.\n"); + // Remove the now processed instructions from the skid buffer. + skidBuffer.pop(); + + // If there's still information in the skid buffer, then + // continue to tell previous stages to stall. They will be + // able to restart once the skid buffer is empty. + if (!skidBuffer.empty()) { + toRename->iewInfo.stall = true; + } else { + DPRINTF(IEW, "IEW: Stage is done unblocking.\n"); + _status = Running; + } +} + +template<class Impl> +void +SimpleIEW<Impl>::wakeDependents(DynInstPtr &inst) +{ + instQueue.wakeDependents(inst); +} + + +template<class Impl> +void +SimpleIEW<Impl>::instToCommit(DynInstPtr &inst) +{ + +} + +template <class Impl> +void +SimpleIEW<Impl>::dispatchInsts() +{ + //////////////////////////////////////// + // DISPATCH/ISSUE stage + //////////////////////////////////////// + + //Put into its own function? + //Add instructions to IQ if there are any instructions there + + // Check if there are any instructions coming from rename, and we're. + // not squashing. + if (fromRename->size > 0) { + int insts_to_add = fromRename->size; + + // Loop through the instructions, putting them in the instruction + // queue. + for (int inst_num = 0; inst_num < insts_to_add; ++inst_num) + { + DynInstPtr inst = fromRename->insts[inst_num]; + + // Make sure there's a valid instruction there. + assert(inst); + + DPRINTF(IEW, "IEW: Issue: Adding PC %#x to IQ.\n", + inst->readPC()); + + // 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. + if (inst->isSquashed()) { + ++iewDispSquashedInsts; + continue; + } else if (instQueue.isFull()) { + DPRINTF(IEW, "IEW: Issue: IQ has become full.\n"); + // Call function to start blocking. + block(); + // Tell previous stage to stall. + toRename->iewInfo.stall = true; + + ++iewIQFullEvents; + break; + } else if (inst->isLoad()) { + DPRINTF(IEW, "IEW: Issue: Memory instruction " + "encountered, adding to LDSTQ.\n"); + + // Reserve a spot in the load store queue for this + // memory access. + ldstQueue.insertLoad(inst); + + ++iewDispLoadInsts; + } else if (inst->isStore()) { + ldstQueue.insertStore(inst); + + ++iewDispStoreInsts; + } else if (inst->isNonSpeculative()) { + DPRINTF(IEW, "IEW: Issue: Nonspeculative instruction " + "encountered, skipping.\n"); + + // Same hack as with stores. + inst->setCanCommit(); + + // Specificall insert it as nonspeculative. + instQueue.insertNonSpec(inst); + + ++iewDispNonSpecInsts; + + continue; + } else if (inst->isNop()) { + DPRINTF(IEW, "IEW: Issue: Nop instruction encountered " + ", skipping.\n"); + + inst->setIssued(); + inst->setExecuted(); + inst->setCanCommit(); + + instQueue.advanceTail(inst); + + continue; + } else if (inst->isExecuted()) { + assert(0 && "Instruction shouldn't be executed.\n"); + DPRINTF(IEW, "IEW: Issue: Executed branch encountered, " + "skipping.\n"); + + inst->setIssued(); + inst->setCanCommit(); + + instQueue.advanceTail(inst); + + continue; + } + + // If the instruction queue is not full, then add the + // instruction. + instQueue.insert(fromRename->insts[inst_num]); + + ++iewDispatchedInsts; + } + } +} + +template <class Impl> +void +SimpleIEW<Impl>::executeInsts() +{ + //////////////////////////////////////// + //EXECUTE/WRITEBACK stage + //////////////////////////////////////// + + //Put into its own function? + //Similarly should probably have separate execution for int vs FP. + // Above comment is handled by the issue queue only issuing a valid + // mix of int/fp instructions. + //Actually okay to just have one execution, buuuuuut will need + //somewhere that defines the execution latency of all instructions. + // @todo: Move to the FU pool used in the current full cpu. + + int fu_usage = 0; + bool fetch_redirect = false; + int inst_slot = 0; + int time_slot = 0; + + // Execute/writeback any instructions that are available. + for (int inst_num = 0; + fu_usage < executeWidth && /* Haven't exceeded available FU's. */ + inst_num < issueWidth && + fromIssue->insts[inst_num]; + ++inst_num) { + + DPRINTF(IEW, "IEW: Execute: Executing instructions from IQ.\n"); + + // Get instruction from issue's queue. + DynInstPtr inst = fromIssue->insts[inst_num]; + + DPRINTF(IEW, "IEW: Execute: Processing PC %#x.\n", inst->readPC()); + + // Check if the instruction is squashed; if so then skip it + // and don't count it towards the FU usage. + if (inst->isSquashed()) { + DPRINTF(IEW, "IEW: Execute: Instruction was squashed.\n"); + + // Consider this instruction executed so that commit can go + // ahead and retire the instruction. + inst->setExecuted(); + + toCommit->insts[inst_num] = inst; + + ++iewExecSquashedInsts; + + continue; + } + + inst->setExecuted(); + + // If an instruction is executed, then count it towards FU usage. + ++fu_usage; + + // Execute instruction. + // Note that if the instruction faults, it will be handled + // at the commit stage. + if (inst->isMemRef()) { + DPRINTF(IEW, "IEW: Execute: Calculating address for memory " + "reference.\n"); + + // Tell the LDSTQ to execute this instruction (if it is a load). + if (inst->isLoad()) { + ldstQueue.executeLoad(inst); + + ++iewExecLoadInsts; + } else if (inst->isStore()) { + ldstQueue.executeStore(inst); + + ++iewExecStoreInsts; + } else { + panic("IEW: Unexpected memory type!\n"); + } + + } else { + inst->execute(); + + ++iewExecutedInsts; + } + + // 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. What happens if you run out of free spaces? + // For now naively assume that all instructions take one cycle. + // Otherwise would have to look into the time buffer based on the + // latency of the instruction. + (*iewQueue)[time_slot].insts[inst_slot]; + while ((*iewQueue)[time_slot].insts[inst_slot]) { + if (inst_slot < issueWidth) { + ++inst_slot; + } else { + ++time_slot; + inst_slot = 0; + } + + assert(time_slot < 5); + } + + // May actually have to work this out, especially with loads and stores + + // Add finished instruction to queue to commit. + (*iewQueue)[time_slot].insts[inst_slot] = inst; + (*iewQueue)[time_slot].size++; + + // Check if branch was correct. This check happens after the + // instruction is added to the queue because even if the branch + // is mispredicted, the branch instruction itself is still valid. + // Only handle this if there hasn't already been something that + // redirects fetch in this group of instructions. + if (!fetch_redirect) { + if (inst->mispredicted()) { + fetch_redirect = true; + + DPRINTF(IEW, "IEW: Execute: Branch mispredict detected.\n"); + DPRINTF(IEW, "IEW: Execute: Redirecting fetch to PC: %#x.\n", + inst->nextPC); + + // If incorrect, then signal the ROB that it must be squashed. + squashDueToBranch(inst); + + if (inst->predTaken()) { + predictedTakenIncorrect++; + } + } else if (ldstQueue.violation()) { + fetch_redirect = true; + + // Get the DynInst that caused the violation. + DynInstPtr violator = ldstQueue.getMemDepViolator(); + + DPRINTF(IEW, "IEW: LDSTQ detected a violation. Violator PC: " + "%#x, inst PC: %#x. Addr is: %#x.\n", + violator->readPC(), inst->readPC(), inst->physEffAddr); + + // Tell the instruction queue that a violation has occured. + instQueue.violation(inst, violator); + + // Squash. + squashDueToMem(inst); + + ++memOrderViolationEvents; + } + } + } +} + +template<class Impl> +void +SimpleIEW<Impl>::tick() +{ + // Considering putting all the state-determining stuff in this section. + + // Try to fill up issue queue with as many instructions as bandwidth + // allows. + // Decode should try to execute as many instructions as its bandwidth + // will allow, as long as it is not currently blocked. + + // Check if the stage is in a running status. + if (_status != Blocked && _status != Squashing) { + DPRINTF(IEW, "IEW: Status is not blocked, attempting to run " + "stage.\n"); + iew(); + + // If it's currently unblocking, check to see if it should switch + // to running. + if (_status == Unblocking) { + unblock(); + + ++iewUnblockCycles; + } + } else if (_status == Squashing) { + + DPRINTF(IEW, "IEW: Still squashing.\n"); + + // Check if stage should remain squashing. Stop squashing if the + // squash signal clears. + if (!fromCommit->commitInfo.squash && + !fromCommit->commitInfo.robSquashing) { + DPRINTF(IEW, "IEW: Done squashing, changing status to " + "running.\n"); + + _status = Running; + instQueue.stopSquash(); + } else { + instQueue.doSquash(); + } + + ++iewSquashCycles; + } else if (_status == Blocked) { + // Continue to tell previous stage to stall. + toRename->iewInfo.stall = true; + + // Check if possible stall conditions have cleared. + if (!fromCommit->commitInfo.stall && + !instQueue.isFull()) { + DPRINTF(IEW, "IEW: Stall signals cleared, going to unblock.\n"); + _status = Unblocking; + } + + // If there's still instructions coming from rename, continue to + // put them on the skid buffer. + if (fromRename->size == 0) { + block(); + } + + if (fromCommit->commitInfo.squash || + fromCommit->commitInfo.robSquashing) { + squash(); + } + + ++iewBlockCycles; + } + + // @todo: Maybe put these at the beginning, so if it's idle it can + // return early. + // Write back number of free IQ entries here. + toRename->iewInfo.freeIQEntries = instQueue.numFreeEntries(); + + 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... + if (!fromCommit->commitInfo.squash && + !fromCommit->commitInfo.robSquashing) { + ldstQueue.commitStores(fromCommit->commitInfo.doneSeqNum); + ldstQueue.commitLoads(fromCommit->commitInfo.doneSeqNum); + } + + if (fromCommit->commitInfo.nonSpecSeqNum != 0) { + instQueue.scheduleNonSpec(fromCommit->commitInfo.nonSpecSeqNum); + } + + DPRINTF(IEW, "IEW: IQ has %i free entries.\n", + instQueue.numFreeEntries()); +} + +template<class Impl> +void +SimpleIEW<Impl>::iew() +{ + // Might want to put all state checks in the tick() function. + // Check if being told to stall from commit. + if (fromCommit->commitInfo.stall) { + block(); + return; + } else if (fromCommit->commitInfo.squash || + fromCommit->commitInfo.robSquashing) { + // Also check if commit is telling this stage to squash. + squash(); + return; + } + + dispatchInsts(); + + // Have the instruction queue try to schedule any ready instructions. + instQueue.scheduleReadyInsts(); + + executeInsts(); + + // Loop through the head of the time buffer and wake any dependents. + // These instructions are about to write back. In the simple model + // this loop can really happen within the previous loop, but when + // instructions have actual latencies, this loop must be separate. + // Also mark scoreboard that this instruction is finally complete. + // Either have IEW have direct access to rename map, or have this as + // part of backwards communication. + for (int inst_num = 0; inst_num < issueWidth && + toCommit->insts[inst_num]; inst_num++) + { + DynInstPtr inst = toCommit->insts[inst_num]; + + DPRINTF(IEW, "IEW: Sending instructions to commit, PC %#x.\n", + inst->readPC()); + + if(!inst->isSquashed()) { + instQueue.wakeDependents(inst); + + for (int i = 0; i < inst->numDestRegs(); i++) + { + renameMap->markAsReady(inst->renamedDestRegIdx(i)); + } + } + } + + // Also should advance its own time buffers if the stage ran. + // Not the best place for it, but this works (hopefully). + issueToExecQueue.advance(); +} + +#if !FULL_SYSTEM +template<class Impl> +void +SimpleIEW<Impl>::lsqWriteback() +{ + ldstQueue.writebackAllInsts(); +} +#endif |