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DAG scheduling during isel. Most new functionality is currently guarded by -enable-sched-cycles and -enable-sched-hazard. Added InstrItineraryData::IssueWidth field, currently derived from ARM itineraries, but could be initialized differently on other targets. Added ScheduleHazardRecognizer::MaxLookAhead to indicate whether it is active, and if so how many cycles of state it holds. Added SchedulingPriorityQueue::HasReadyFilter to allowing gating entry into the scheduler's available queue. ScoreboardHazardRecognizer now accesses the ScheduleDAG in order to get information about it's SUnits, provides RecedeCycle for bottom-up scheduling, correctly computes scoreboard depth, tracks IssueCount, and considers potential stall cycles when checking for hazards. ScheduleDAGRRList now models machine cycles and hazards (under flags). It tracks MinAvailableCycle, drives the hazard recognizer and priority queue's ready filter, manages a new PendingQueue, properly accounts for stall cycles, etc. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122541 91177308-0d34-0410-b5e6-96231b3b80d8
240 lines
7.5 KiB
C++
240 lines
7.5 KiB
C++
//===----- ScoreboardHazardRecognizer.cpp - Scheduler Support -------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the ScoreboardHazardRecognizer class, which
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// encapsultes hazard-avoidance heuristics for scheduling, based on the
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// scheduling itineraries specified for the target.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE ::llvm::ScoreboardHazardRecognizer::DebugType
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#include "llvm/CodeGen/ScoreboardHazardRecognizer.h"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetInstrItineraries.h"
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using namespace llvm;
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#ifndef NDEBUG
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const char *ScoreboardHazardRecognizer::DebugType = "";
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#endif
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ScoreboardHazardRecognizer::
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ScoreboardHazardRecognizer(const InstrItineraryData *II,
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const ScheduleDAG *SchedDAG,
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const char *ParentDebugType) :
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ScheduleHazardRecognizer(), ItinData(II), DAG(SchedDAG), IssueWidth(0),
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IssueCount(0) {
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#ifndef NDEBUG
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DebugType = ParentDebugType;
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#endif
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// Determine the maximum depth of any itinerary. This determines the
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// depth of the scoreboard. We always make the scoreboard at least 1
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// cycle deep to avoid dealing with the boundary condition.
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unsigned ScoreboardDepth = 1;
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if (ItinData && !ItinData->isEmpty()) {
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IssueWidth = ItinData->IssueWidth;
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for (unsigned idx = 0; ; ++idx) {
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if (ItinData->isEndMarker(idx))
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break;
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const InstrStage *IS = ItinData->beginStage(idx);
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const InstrStage *E = ItinData->endStage(idx);
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unsigned CurCycle = 0;
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unsigned ItinDepth = 0;
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for (; IS != E; ++IS) {
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unsigned StageDepth = CurCycle + IS->getCycles();
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if (ItinDepth < StageDepth) ItinDepth = StageDepth;
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CurCycle += IS->getNextCycles();
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}
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// Find the next power-of-2 >= ItinDepth
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while (ItinDepth > ScoreboardDepth) {
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ScoreboardDepth *= 2;
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}
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}
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MaxLookAhead = ScoreboardDepth;
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}
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ReservedScoreboard.reset(ScoreboardDepth);
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RequiredScoreboard.reset(ScoreboardDepth);
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DEBUG(dbgs() << "Using scoreboard hazard recognizer: Depth = "
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<< ScoreboardDepth << '\n');
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}
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void ScoreboardHazardRecognizer::Reset() {
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IssueCount = 0;
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RequiredScoreboard.reset();
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ReservedScoreboard.reset();
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}
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void ScoreboardHazardRecognizer::Scoreboard::dump() const {
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dbgs() << "Scoreboard:\n";
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unsigned last = Depth - 1;
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while ((last > 0) && ((*this)[last] == 0))
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last--;
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for (unsigned i = 0; i <= last; i++) {
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unsigned FUs = (*this)[i];
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dbgs() << "\t";
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for (int j = 31; j >= 0; j--)
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dbgs() << ((FUs & (1 << j)) ? '1' : '0');
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dbgs() << '\n';
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}
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}
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bool ScoreboardHazardRecognizer::atIssueLimit() const {
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if (IssueWidth == 0)
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return false;
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return IssueCount == IssueWidth;
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}
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ScheduleHazardRecognizer::HazardType
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ScoreboardHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
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if (!ItinData || ItinData->isEmpty())
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return NoHazard;
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// Note that stalls will be negative for bottom-up scheduling.
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int cycle = Stalls;
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// Use the itinerary for the underlying instruction to check for
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// free FU's in the scoreboard at the appropriate future cycles.
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const TargetInstrDesc *TID = DAG->getInstrDesc(SU);
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if (TID == NULL) {
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// Don't check hazards for non-machineinstr Nodes.
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return NoHazard;
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}
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unsigned idx = TID->getSchedClass();
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for (const InstrStage *IS = ItinData->beginStage(idx),
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*E = ItinData->endStage(idx); IS != E; ++IS) {
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// We must find one of the stage's units free for every cycle the
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// stage is occupied. FIXME it would be more accurate to find the
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// same unit free in all the cycles.
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for (unsigned int i = 0; i < IS->getCycles(); ++i) {
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int StageCycle = cycle + (int)i;
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if (StageCycle < 0)
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continue;
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if (StageCycle >= (int)RequiredScoreboard.getDepth()) {
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assert((StageCycle - Stalls) < (int)RequiredScoreboard.getDepth() &&
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"Scoreboard depth exceeded!");
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// This stage was stalled beyond pipeline depth, so cannot conflict.
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break;
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}
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unsigned freeUnits = IS->getUnits();
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switch (IS->getReservationKind()) {
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default:
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assert(0 && "Invalid FU reservation");
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case InstrStage::Required:
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// Required FUs conflict with both reserved and required ones
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freeUnits &= ~ReservedScoreboard[StageCycle];
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// FALLTHROUGH
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case InstrStage::Reserved:
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// Reserved FUs can conflict only with required ones.
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freeUnits &= ~RequiredScoreboard[StageCycle];
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break;
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}
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if (!freeUnits) {
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DEBUG(dbgs() << "*** Hazard in cycle " << (cycle + i) << ", ");
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DEBUG(dbgs() << "SU(" << SU->NodeNum << "): ");
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DEBUG(DAG->dumpNode(SU));
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return Hazard;
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}
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}
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// Advance the cycle to the next stage.
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cycle += IS->getNextCycles();
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}
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return NoHazard;
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}
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void ScoreboardHazardRecognizer::EmitInstruction(SUnit *SU) {
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if (!ItinData || ItinData->isEmpty())
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return;
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++IssueCount;
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unsigned cycle = 0;
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// Use the itinerary for the underlying instruction to reserve FU's
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// in the scoreboard at the appropriate future cycles.
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const TargetInstrDesc *TID = DAG->getInstrDesc(SU);
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assert(TID && "The scheduler must filter non-machineinstrs");
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unsigned idx = TID->getSchedClass();
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for (const InstrStage *IS = ItinData->beginStage(idx),
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*E = ItinData->endStage(idx); IS != E; ++IS) {
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// We must reserve one of the stage's units for every cycle the
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// stage is occupied. FIXME it would be more accurate to reserve
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// the same unit free in all the cycles.
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for (unsigned int i = 0; i < IS->getCycles(); ++i) {
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assert(((cycle + i) < RequiredScoreboard.getDepth()) &&
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"Scoreboard depth exceeded!");
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unsigned freeUnits = IS->getUnits();
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switch (IS->getReservationKind()) {
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default:
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assert(0 && "Invalid FU reservation");
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case InstrStage::Required:
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// Required FUs conflict with both reserved and required ones
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freeUnits &= ~ReservedScoreboard[cycle + i];
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// FALLTHROUGH
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case InstrStage::Reserved:
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// Reserved FUs can conflict only with required ones.
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freeUnits &= ~RequiredScoreboard[cycle + i];
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break;
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}
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// reduce to a single unit
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unsigned freeUnit = 0;
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do {
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freeUnit = freeUnits;
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freeUnits = freeUnit & (freeUnit - 1);
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} while (freeUnits);
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assert(freeUnit && "No function unit available!");
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if (IS->getReservationKind() == InstrStage::Required)
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RequiredScoreboard[cycle + i] |= freeUnit;
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else
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ReservedScoreboard[cycle + i] |= freeUnit;
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}
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// Advance the cycle to the next stage.
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cycle += IS->getNextCycles();
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}
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DEBUG(ReservedScoreboard.dump());
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DEBUG(RequiredScoreboard.dump());
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}
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void ScoreboardHazardRecognizer::AdvanceCycle() {
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IssueCount = 0;
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ReservedScoreboard[0] = 0; ReservedScoreboard.advance();
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RequiredScoreboard[0] = 0; RequiredScoreboard.advance();
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}
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void ScoreboardHazardRecognizer::RecedeCycle() {
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IssueCount = 0;
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ReservedScoreboard[ReservedScoreboard.getDepth()-1] = 0;
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ReservedScoreboard.recede();
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RequiredScoreboard[RequiredScoreboard.getDepth()-1] = 0;
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RequiredScoreboard.recede();
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}
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