338 lines
10 KiB
C++
338 lines
10 KiB
C++
//=-- SystemZHazardRecognizer.h - SystemZ Hazard Recognizer -----*- C++ -*-===//
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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 defines a hazard recognizer for the SystemZ scheduler.
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//
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// This class is used by the SystemZ scheduling strategy to maintain
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// the state during scheduling, and provide cost functions for
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// scheduling candidates. This includes:
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//
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// * Decoder grouping. A decoder group can maximally hold 3 uops, and
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// instructions that always begin a new group should be scheduled when
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// the current decoder group is empty.
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// * Processor resources usage. It is beneficial to balance the use of
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// resources.
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//
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// ===---------------------------------------------------------------------===//
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#include "SystemZHazardRecognizer.h"
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#include "llvm/ADT/Statistic.h"
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using namespace llvm;
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#define DEBUG_TYPE "misched"
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// This is the limit of processor resource usage at which the
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// scheduler should try to look for other instructions (not using the
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// critical resource).
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static cl::opt<int> ProcResCostLim("procres-cost-lim", cl::Hidden,
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cl::desc("The OOO window for processor "
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"resources during scheduling."),
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cl::init(8));
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SystemZHazardRecognizer::
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SystemZHazardRecognizer(const MachineSchedContext *C) : DAG(nullptr),
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SchedModel(nullptr) {}
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unsigned SystemZHazardRecognizer::
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getNumDecoderSlots(SUnit *SU) const {
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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if (!SC->isValid())
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return 0; // IMPLICIT_DEF / KILL -- will not make impact in output.
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if (SC->BeginGroup) {
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if (!SC->EndGroup)
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return 2; // Cracked instruction
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else
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return 3; // Expanded/group-alone instruction
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}
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return 1; // Normal instruction
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}
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unsigned SystemZHazardRecognizer::getCurrCycleIdx() {
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unsigned Idx = CurrGroupSize;
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if (GrpCount % 2)
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Idx += 3;
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return Idx;
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}
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ScheduleHazardRecognizer::HazardType SystemZHazardRecognizer::
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getHazardType(SUnit *m, int Stalls) {
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return (fitsIntoCurrentGroup(m) ? NoHazard : Hazard);
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}
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void SystemZHazardRecognizer::Reset() {
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CurrGroupSize = 0;
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clearProcResCounters();
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GrpCount = 0;
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LastFPdOpCycleIdx = UINT_MAX;
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DEBUG(CurGroupDbg = "";);
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}
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bool
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SystemZHazardRecognizer::fitsIntoCurrentGroup(SUnit *SU) const {
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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if (!SC->isValid())
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return true;
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// A cracked instruction only fits into schedule if the current
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// group is empty.
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if (SC->BeginGroup)
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return (CurrGroupSize == 0);
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// Since a full group is handled immediately in EmitInstruction(),
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// SU should fit into current group. NumSlots should be 1 or 0,
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// since it is not a cracked or expanded instruction.
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assert ((getNumDecoderSlots(SU) <= 1) && (CurrGroupSize < 3) &&
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"Expected normal instruction to fit in non-full group!");
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return true;
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}
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void SystemZHazardRecognizer::nextGroup(bool DbgOutput) {
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if (CurrGroupSize > 0) {
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DEBUG(dumpCurrGroup("Completed decode group"));
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DEBUG(CurGroupDbg = "";);
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GrpCount++;
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// Reset counter for next group.
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CurrGroupSize = 0;
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// Decrease counters for execution units by one.
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for (unsigned i = 0; i < SchedModel->getNumProcResourceKinds(); ++i)
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if (ProcResourceCounters[i] > 0)
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ProcResourceCounters[i]--;
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// Clear CriticalResourceIdx if it is now below the threshold.
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if (CriticalResourceIdx != UINT_MAX &&
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(ProcResourceCounters[CriticalResourceIdx] <=
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ProcResCostLim))
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CriticalResourceIdx = UINT_MAX;
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}
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DEBUG(if (DbgOutput)
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dumpProcResourceCounters(););
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}
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#ifndef NDEBUG // Debug output
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void SystemZHazardRecognizer::dumpSU(SUnit *SU, raw_ostream &OS) const {
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OS << "SU(" << SU->NodeNum << "):";
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OS << SchedModel->getInstrInfo()->getName(SU->getInstr()->getOpcode());
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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if (!SC->isValid())
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return;
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for (TargetSchedModel::ProcResIter
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PI = SchedModel->getWriteProcResBegin(SC),
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PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
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const MCProcResourceDesc &PRD =
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*SchedModel->getProcResource(PI->ProcResourceIdx);
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std::string FU(PRD.Name);
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// trim e.g. Z13_FXaUnit -> FXa
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FU = FU.substr(FU.find("_") + 1);
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FU.resize(FU.find("Unit"));
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OS << "/" << FU;
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if (PI->Cycles > 1)
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OS << "(" << PI->Cycles << "cyc)";
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}
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if (SC->NumMicroOps > 1)
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OS << "/" << SC->NumMicroOps << "uops";
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if (SC->BeginGroup && SC->EndGroup)
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OS << "/GroupsAlone";
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else if (SC->BeginGroup)
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OS << "/BeginsGroup";
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else if (SC->EndGroup)
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OS << "/EndsGroup";
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if (SU->isUnbuffered)
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OS << "/Unbuffered";
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}
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void SystemZHazardRecognizer::dumpCurrGroup(std::string Msg) const {
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dbgs() << "+++ " << Msg;
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dbgs() << ": ";
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if (CurGroupDbg.empty())
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dbgs() << " <empty>\n";
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else {
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dbgs() << "{ " << CurGroupDbg << " }";
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dbgs() << " (" << CurrGroupSize << " decoder slot"
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<< (CurrGroupSize > 1 ? "s":"")
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<< ")\n";
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}
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}
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void SystemZHazardRecognizer::dumpProcResourceCounters() const {
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bool any = false;
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for (unsigned i = 0; i < SchedModel->getNumProcResourceKinds(); ++i)
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if (ProcResourceCounters[i] > 0) {
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any = true;
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break;
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}
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if (!any)
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return;
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dbgs() << "+++ Resource counters:\n";
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for (unsigned i = 0; i < SchedModel->getNumProcResourceKinds(); ++i)
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if (ProcResourceCounters[i] > 0) {
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dbgs() << "+++ Extra schedule for execution unit "
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<< SchedModel->getProcResource(i)->Name
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<< ": " << ProcResourceCounters[i] << "\n";
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any = true;
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}
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}
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#endif //NDEBUG
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void SystemZHazardRecognizer::clearProcResCounters() {
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ProcResourceCounters.assign(SchedModel->getNumProcResourceKinds(), 0);
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CriticalResourceIdx = UINT_MAX;
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}
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// Update state with SU as the next scheduled unit.
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void SystemZHazardRecognizer::
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EmitInstruction(SUnit *SU) {
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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DEBUG( dumpCurrGroup("Decode group before emission"););
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// If scheduling an SU that must begin a new decoder group, move on
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// to next group.
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if (!fitsIntoCurrentGroup(SU))
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nextGroup();
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DEBUG( dbgs() << "+++ HazardRecognizer emitting "; dumpSU(SU, dbgs());
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dbgs() << "\n";
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raw_string_ostream cgd(CurGroupDbg);
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if (CurGroupDbg.length())
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cgd << ", ";
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dumpSU(SU, cgd););
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// After returning from a call, we don't know much about the state.
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if (SU->getInstr()->isCall()) {
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DEBUG (dbgs() << "+++ Clearing state after call.\n";);
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clearProcResCounters();
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LastFPdOpCycleIdx = UINT_MAX;
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CurrGroupSize += getNumDecoderSlots(SU);
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assert (CurrGroupSize <= 3);
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nextGroup();
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return;
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}
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// Increase counter for execution unit(s).
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for (TargetSchedModel::ProcResIter
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PI = SchedModel->getWriteProcResBegin(SC),
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PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI) {
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// Don't handle FPd together with the other resources.
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if (SchedModel->getProcResource(PI->ProcResourceIdx)->BufferSize == 1)
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continue;
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int &CurrCounter =
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ProcResourceCounters[PI->ProcResourceIdx];
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CurrCounter += PI->Cycles;
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// Check if this is now the new critical resource.
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if ((CurrCounter > ProcResCostLim) &&
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(CriticalResourceIdx == UINT_MAX ||
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(PI->ProcResourceIdx != CriticalResourceIdx &&
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CurrCounter >
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ProcResourceCounters[CriticalResourceIdx]))) {
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DEBUG( dbgs() << "+++ New critical resource: "
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<< SchedModel->getProcResource(PI->ProcResourceIdx)->Name
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<< "\n";);
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CriticalResourceIdx = PI->ProcResourceIdx;
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}
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}
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// Make note of an instruction that uses a blocking resource (FPd).
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if (SU->isUnbuffered) {
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LastFPdOpCycleIdx = getCurrCycleIdx();
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DEBUG (dbgs() << "+++ Last FPd cycle index: "
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<< LastFPdOpCycleIdx << "\n";);
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}
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// Insert SU into current group by increasing number of slots used
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// in current group.
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CurrGroupSize += getNumDecoderSlots(SU);
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assert (CurrGroupSize <= 3);
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// Check if current group is now full/ended. If so, move on to next
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// group to be ready to evaluate more candidates.
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if (CurrGroupSize == 3 || SC->EndGroup)
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nextGroup();
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}
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int SystemZHazardRecognizer::groupingCost(SUnit *SU) const {
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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if (!SC->isValid())
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return 0;
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// If SU begins new group, it can either break a current group early
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// or fit naturally if current group is empty (negative cost).
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if (SC->BeginGroup) {
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if (CurrGroupSize)
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return 3 - CurrGroupSize;
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return -1;
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}
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// Similarly, a group-ending SU may either fit well (last in group), or
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// end the group prematurely.
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if (SC->EndGroup) {
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unsigned resultingGroupSize =
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(CurrGroupSize + getNumDecoderSlots(SU));
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if (resultingGroupSize < 3)
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return (3 - resultingGroupSize);
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return -1;
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}
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// Most instructions can be placed in any decoder slot.
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return 0;
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}
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bool SystemZHazardRecognizer::isFPdOpPreferred_distance(const SUnit *SU) {
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assert (SU->isUnbuffered);
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// If this is the first FPd op, it should be scheduled high.
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if (LastFPdOpCycleIdx == UINT_MAX)
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return true;
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// If this is not the first PFd op, it should go into the other side
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// of the processor to use the other FPd unit there. This should
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// generally happen if two FPd ops are placed with 2 other
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// instructions between them (modulo 6).
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if (LastFPdOpCycleIdx > getCurrCycleIdx())
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return ((LastFPdOpCycleIdx - getCurrCycleIdx()) == 3);
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return ((getCurrCycleIdx() - LastFPdOpCycleIdx) == 3);
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}
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int SystemZHazardRecognizer::
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resourcesCost(SUnit *SU) {
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int Cost = 0;
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const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
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if (!SC->isValid())
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return 0;
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// For a FPd op, either return min or max value as indicated by the
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// distance to any prior FPd op.
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if (SU->isUnbuffered)
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Cost = (isFPdOpPreferred_distance(SU) ? INT_MIN : INT_MAX);
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// For other instructions, give a cost to the use of the critical resource.
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else if (CriticalResourceIdx != UINT_MAX) {
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for (TargetSchedModel::ProcResIter
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PI = SchedModel->getWriteProcResBegin(SC),
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PE = SchedModel->getWriteProcResEnd(SC); PI != PE; ++PI)
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if (PI->ProcResourceIdx == CriticalResourceIdx)
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Cost = PI->Cycles;
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}
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return Cost;
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}
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