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Diffstat (limited to 'cpu/beta_cpu/commit_impl.hh')
| -rw-r--r-- | cpu/beta_cpu/commit_impl.hh | 509 |
1 files changed, 509 insertions, 0 deletions
diff --git a/cpu/beta_cpu/commit_impl.hh b/cpu/beta_cpu/commit_impl.hh new file mode 100644 index 000000000..3e97b980c --- /dev/null +++ b/cpu/beta_cpu/commit_impl.hh @@ -0,0 +1,509 @@ +// @todo: Bug when something reaches execute, and mispredicts, but is never +// put into the ROB because the ROB is full. Need rename stage to predict +// the free ROB entries better. + +#ifndef __COMMIT_IMPL_HH__ +#define __COMMIT_IMPL_HH__ + +#include "base/timebuf.hh" +#include "cpu/beta_cpu/commit.hh" +#include "cpu/exetrace.hh" + +template <class Impl> +SimpleCommit<Impl>::SimpleCommit(Params ¶ms) + : dcacheInterface(params.dcacheInterface), + iewToCommitDelay(params.iewToCommitDelay), + renameToROBDelay(params.renameToROBDelay), + renameWidth(params.renameWidth), + iewWidth(params.executeWidth), + commitWidth(params.commitWidth) +{ + _status = Idle; +} + +template <class Impl> +void +SimpleCommit<Impl>::regStats() +{ + commitCommittedInsts + .name(name() + ".commitCommittedInsts") + .desc("The number of committed instructions") + .prereq(commitCommittedInsts); + commitSquashedInsts + .name(name() + ".commitSquashedInsts") + .desc("The number of squashed insts skipped by commit") + .prereq(commitSquashedInsts); + commitSquashEvents + .name(name() + ".commitSquashEvents") + .desc("The number of times commit is told to squash") + .prereq(commitSquashEvents); + commitNonSpecStalls + .name(name() + ".commitNonSpecStalls") + .desc("The number of times commit has been forced to stall to " + "communicate backwards") + .prereq(commitNonSpecStalls); + commitCommittedBranches + .name(name() + ".commitCommittedBranches") + .desc("The number of committed branches") + .prereq(commitCommittedBranches); + commitCommittedLoads + .name(name() + ".commitCommittedLoads") + .desc("The number of committed loads") + .prereq(commitCommittedLoads); + commitCommittedMemRefs + .name(name() + ".commitCommittedMemRefs") + .desc("The number of committed memory references") + .prereq(commitCommittedMemRefs); + branchMispredicts + .name(name() + ".branchMispredicts") + .desc("The number of times a branch was mispredicted") + .prereq(branchMispredicts); + n_committed_dist + .init(0,commitWidth,1) + .name(name() + ".COM:committed_per_cycle") + .desc("Number of insts commited each cycle") + .flags(Stats::pdf) + ; +} + +template <class Impl> +void +SimpleCommit<Impl>::setCPU(FullCPU *cpu_ptr) +{ + DPRINTF(Commit, "Commit: Setting CPU pointer.\n"); + cpu = cpu_ptr; +} + +template <class Impl> +void +SimpleCommit<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr) +{ + DPRINTF(Commit, "Commit: Setting time buffer pointer.\n"); + 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 +SimpleCommit<Impl>::setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr) +{ + DPRINTF(Commit, "Commit: Setting rename queue pointer.\n"); + renameQueue = rq_ptr; + + // Setup wire to get instructions from rename (for the ROB). + fromRename = renameQueue->getWire(-renameToROBDelay); +} + +template <class Impl> +void +SimpleCommit<Impl>::setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr) +{ + DPRINTF(Commit, "Commit: Setting IEW queue pointer.\n"); + iewQueue = iq_ptr; + + // Setup wire to get instructions from IEW. + fromIEW = iewQueue->getWire(-iewToCommitDelay); +} + +template <class Impl> +void +SimpleCommit<Impl>::setROB(ROB *rob_ptr) +{ + DPRINTF(Commit, "Commit: Setting ROB pointer.\n"); + rob = rob_ptr; +} + +template <class Impl> +void +SimpleCommit<Impl>::tick() +{ + // If the ROB is currently in its squash sequence, then continue + // to squash. In this case, commit does not do anything. Otherwise + // run commit. + if (_status == ROBSquashing) { + if (rob->isDoneSquashing()) { + _status = Running; + } else { + rob->doSquash(); + + // Send back sequence number of tail of ROB, so other stages + // can squash younger instructions. Note that really the only + // stage that this is important for is the IEW stage; other + // stages can just clear all their state as long as selective + // replay isn't used. + toIEW->commitInfo.doneSeqNum = rob->readTailSeqNum(); + toIEW->commitInfo.robSquashing = true; + } + } else { + commit(); + } + + markCompletedInsts(); + + // Writeback number of free ROB entries here. + DPRINTF(Commit, "Commit: ROB has %d free entries.\n", + rob->numFreeEntries()); + toIEW->commitInfo.freeROBEntries = rob->numFreeEntries(); +} + +template <class Impl> +void +SimpleCommit<Impl>::commit() +{ + ////////////////////////////////////// + // Check for interrupts + ////////////////////////////////////// + + // Process interrupts if interrupts are enabled and not in PAL mode. + // Take the PC from commit and write it to the IPR, then squash. The + // interrupt completing will take care of restoring the PC from that value + // in the IPR. Look at IPR[EXC_ADDR]; + // hwrei() is what resets the PC to the place where instruction execution + // beings again. +#ifdef FULL_SYSTEM + if (ISA::check_interrupts && + cpu->check_interrupts() && + !xc->inPalMode()) { + // Will need to squash all instructions currently in flight and have + // the interrupt handler restart at the last non-committed inst. + // Most of that can be handled through the trap() function. The + // processInterrupts() function really just checks for interrupts + // and then calls trap() if there is an interrupt present. + + // CPU will handle implementation of the interrupt. + cpu->processInterrupts(); + } +#endif // FULL_SYSTEM + + //////////////////////////////////// + // Check for squash signal, handle that first + //////////////////////////////////// + + // Want to mainly check if the IEW stage is telling the ROB to squash. + // Should I also check if the commit stage is telling the ROB to squah? + // This might be necessary to keep the same timing between the IQ and + // the ROB... + if (fromIEW->squash) { + DPRINTF(Commit, "Commit: Squashing instructions in the ROB.\n"); + + _status = ROBSquashing; + + InstSeqNum squashed_inst = fromIEW->squashedSeqNum; + + rob->squash(squashed_inst); + + // Send back the sequence number of the squashed instruction. + toIEW->commitInfo.doneSeqNum = squashed_inst; + + // Send back the squash signal to tell stages that they should squash. + toIEW->commitInfo.squash = true; + + // Send back the rob squashing signal so other stages know that the + // ROB is in the process of squashing. + toIEW->commitInfo.robSquashing = true; + + toIEW->commitInfo.branchMispredict = fromIEW->branchMispredict; + + toIEW->commitInfo.branchTaken = fromIEW->branchTaken; + + toIEW->commitInfo.nextPC = fromIEW->nextPC; + + toIEW->commitInfo.mispredPC = fromIEW->mispredPC; + + toIEW->commitInfo.globalHist = fromIEW->globalHist; + + if (toIEW->commitInfo.branchMispredict) { + ++branchMispredicts; + } + } + + if (_status != ROBSquashing) { + // If we're not currently squashing, then get instructions. + getInsts(); + + // Try to commit any instructions. + commitInsts(); + } + + // If the ROB is empty, we can set this stage to idle. Use this + // in the future when the Idle status will actually be utilized. +#if 0 + if (rob->isEmpty()) { + DPRINTF(Commit, "Commit: ROB is empty. Status changed to idle.\n"); + _status = Idle; + // Schedule an event so that commit will actually wake up + // once something gets put in the ROB. + } +#endif +} + +// Loop that goes through as many instructions in the ROB as possible and +// tries to commit them. The actual work for committing is done by the +// commitHead() function. +template <class Impl> +void +SimpleCommit<Impl>::commitInsts() +{ + //////////////////////////////////// + // Handle commit + // Note that commit will be handled prior to 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... + //////////////////////////////////// + + DynInstPtr head_inst = rob->readHeadInst(); + + unsigned num_committed = 0; + + // Commit as many instructions as possible until the commit bandwidth + // limit is reached, or it becomes impossible to commit any more. + while (!rob->isEmpty() && + head_inst->readyToCommit() && + num_committed < commitWidth) + { + DPRINTF(Commit, "Commit: Trying to commit head instruction.\n"); + + // If the head instruction is squashed, it is ready to retire at any + // time. However, we need to avoid updating any other state + // incorrectly if it's already been squashed. + if (head_inst->isSquashed()) { + // Hack to avoid the instruction being retired (and deleted) if + // it hasn't been through the IEW stage yet. + if (!head_inst->isExecuted()) { + break; + } + + DPRINTF(Commit, "Commit: Retiring squashed instruction from " + "ROB.\n"); + + // Tell ROB to retire head instruction. This retires the head + // inst in the ROB without affecting any other stages. + rob->retireHead(); + + ++commitSquashedInsts; + + } else { + // 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. + cpu->funcExeInst++; + + // Try to commit the head instruction. + bool commit_success = commitHead(head_inst, num_committed); + + // Update what instruction we are looking at if the commit worked. + if (commit_success) { + ++num_committed; + + // Send back which instruction has been committed. + // @todo: Update this later when a wider pipeline is used. + // Hmm, can't really give a pointer here...perhaps the + // sequence number instead (copy). + toIEW->commitInfo.doneSeqNum = head_inst->seqNum; + + ++commitCommittedInsts; + + if (!head_inst->isNop()) { + cpu->instDone(); + } + } else { + break; + } + } + + // Update the pointer to read the next instruction in the ROB. + head_inst = rob->readHeadInst(); + } + + DPRINTF(CommitRate, "%i\n", num_committed); + n_committed_dist.sample(num_committed); +} + +template <class Impl> +bool +SimpleCommit<Impl>::commitHead(DynInstPtr &head_inst, unsigned inst_num) +{ + // Make sure instruction is valid + assert(head_inst); + + // If the instruction is not executed yet, then it is a non-speculative + // or store inst. 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. + cpu->funcExeInst--; + + if (head_inst->isStore() || head_inst->isNonSpeculative()) { + DPRINTF(Commit, "Commit: Encountered a store or non-speculative " + "instruction at the head of the ROB, PC %#x.\n", + head_inst->readPC()); + + toIEW->commitInfo.nonSpecSeqNum = head_inst->seqNum; + + // Change the instruction so it won't try to commit again until + // it is executed. + head_inst->clearCanCommit(); + + ++commitNonSpecStalls; + + return false; + } else { + panic("Commit: Trying to commit un-executed instruction " + "of unknown type!\n"); + } + } + + // Now check if it's one of the special trap or barrier or + // serializing instructions. + if (head_inst->isThreadSync() || + head_inst->isSerializing() || + head_inst->isMemBarrier() || + head_inst->isWriteBarrier() ) + { + // Not handled for now. Mem barriers and write barriers are safe + // to simply let commit as memory accesses only happen once they + // reach the head of commit. Not sure about the other two. + panic("Serializing or barrier instructions" + " are not handled yet.\n"); + } + + // Check if the instruction caused a fault. If so, trap. + if (head_inst->getFault() != No_Fault) { + if (!head_inst->isNop()) { +#ifdef FULL_SYSTEM + cpu->trap(fault); +#else // !FULL_SYSTEM + panic("fault (%d) detected @ PC %08p", head_inst->getFault(), + head_inst->PC); +#endif // FULL_SYSTEM + } + } + + // Check if we're really ready to commit. If not then return false. + // I'm pretty sure all instructions should be able to commit if they've + // reached this far. For now leave this in as a check. + if(!rob->isHeadReady()) { + panic("Commit: Unable to commit head instruction!\n"); + return false; + } + + // If it's a branch, then send back branch prediction update info + // to the fetch stage. + // This should be handled in the iew stage if a mispredict happens... + + if (head_inst->isControl()) { + +#if 0 + toIEW->nextPC = head_inst->readPC(); + //Maybe switch over to BTB incorrect. + toIEW->btbMissed = head_inst->btbMiss(); + toIEW->target = head_inst->nextPC; + //Maybe also include global history information. + //This simple version will have no branch prediction however. +#endif + + ++commitCommittedBranches; + } + + +#if 0 + // Check if the instruction has a destination register. + // If so add the previous physical register of its logical register's + // destination to the free list through the time buffer. + for (int i = 0; i < head_inst->numDestRegs(); i++) + { + toIEW->commitInfo.freeRegs.push_back(head_inst->prevDestRegIdx(i)); + } +#endif + + // Explicit communication back to the LDSTQ that a load has been committed + // and can be removed from the LDSTQ. Stores don't need this because + // the LDSTQ will already have been told that a store has reached the head + // of the ROB. Consider including communication if it's a store as well + // to keep things orthagonal. + if (head_inst->isMemRef()) { + ++commitCommittedMemRefs; + if (head_inst->isLoad()) { + toIEW->commitInfo.commitIsLoad = true; + ++commitCommittedLoads; + } + } + + // Now that the instruction is going to be committed, finalize its + // trace data. + if (head_inst->traceData) { + head_inst->traceData->finalize(); + } + + //Finally clear the head ROB entry. + rob->retireHead(); + + // Return true to indicate that we have committed an instruction. + return true; +} + +template <class Impl> +void +SimpleCommit<Impl>::getInsts() +{ + ////////////////////////////////////// + // Handle ROB functions + ////////////////////////////////////// + + // Read any issued instructions and place them into the ROB. Do this + // prior to squashing to avoid having instructions in the ROB that + // don't get squashed properly. + int insts_to_process = min((int)renameWidth, fromRename->size); + + for (int inst_num = 0; + inst_num < insts_to_process; + ++inst_num) + { + if (!fromRename->insts[inst_num]->isSquashed()) { + DPRINTF(Commit, "Commit: Inserting PC %#x into ROB.\n", + fromRename->insts[inst_num]->readPC()); + rob->insertInst(fromRename->insts[inst_num]); + } else { + DPRINTF(Commit, "Commit: Instruction %i PC %#x was " + "squashed, skipping.\n", + fromRename->insts[inst_num]->seqNum, + fromRename->insts[inst_num]->readPC()); + } + } +} + +template <class Impl> +void +SimpleCommit<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 < iewWidth && fromIEW->insts[inst_num]; + ++inst_num) + { + DPRINTF(Commit, "Commit: Marking PC %#x, SN %i ready within ROB.\n", + fromIEW->insts[inst_num]->readPC(), + fromIEW->insts[inst_num]->seqNum); + + // Mark the instruction as ready to commit. + fromIEW->insts[inst_num]->setCanCommit(); + } +} + +template <class Impl> +uint64_t +SimpleCommit<Impl>::readCommitPC() +{ + return rob->readHeadPC(); +} + +#endif // __COMMIT_IMPL_HH__ |