643 lines
20 KiB
C++
643 lines
20 KiB
C++
//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===//
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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 implements the ScheduleDAG class, which is a base class used by
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// scheduling implementation classes.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "pre-RA-sched"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
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#include "llvm/CodeGen/SelectionDAGNodes.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include <climits>
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using namespace llvm;
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#ifndef NDEBUG
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static cl::opt<bool> StressSchedOpt(
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"stress-sched", cl::Hidden, cl::init(false),
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cl::desc("Stress test instruction scheduling"));
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#endif
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void SchedulingPriorityQueue::anchor() { }
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ScheduleDAG::ScheduleDAG(MachineFunction &mf)
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: TM(mf.getTarget()),
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TII(TM.getInstrInfo()),
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TRI(TM.getRegisterInfo()),
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MF(mf), MRI(mf.getRegInfo()),
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EntrySU(), ExitSU() {
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#ifndef NDEBUG
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StressSched = StressSchedOpt;
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#endif
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}
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ScheduleDAG::~ScheduleDAG() {}
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/// Clear the DAG state (e.g. between scheduling regions).
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void ScheduleDAG::clearDAG() {
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SUnits.clear();
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EntrySU = SUnit();
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ExitSU = SUnit();
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}
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/// getInstrDesc helper to handle SDNodes.
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const MCInstrDesc *ScheduleDAG::getNodeDesc(const SDNode *Node) const {
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if (!Node || !Node->isMachineOpcode()) return NULL;
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return &TII->get(Node->getMachineOpcode());
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}
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/// addPred - This adds the specified edge as a pred of the current node if
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/// not already. It also adds the current node as a successor of the
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/// specified node.
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bool SUnit::addPred(const SDep &D, bool Required) {
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// If this node already has this depenence, don't add a redundant one.
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for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end();
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I != E; ++I) {
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// Zero-latency weak edges may be added purely for heuristic ordering. Don't
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// add them if another kind of edge already exists.
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if (!Required && I->getSUnit() == D.getSUnit())
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return false;
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if (I->overlaps(D)) {
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// Extend the latency if needed. Equivalent to removePred(I) + addPred(D).
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if (I->getLatency() < D.getLatency()) {
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SUnit *PredSU = I->getSUnit();
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// Find the corresponding successor in N.
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SDep ForwardD = *I;
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ForwardD.setSUnit(this);
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for (SmallVectorImpl<SDep>::iterator II = PredSU->Succs.begin(),
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EE = PredSU->Succs.end(); II != EE; ++II) {
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if (*II == ForwardD) {
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II->setLatency(D.getLatency());
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break;
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}
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}
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I->setLatency(D.getLatency());
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}
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return false;
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}
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}
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// Now add a corresponding succ to N.
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SDep P = D;
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P.setSUnit(this);
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SUnit *N = D.getSUnit();
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// Update the bookkeeping.
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if (D.getKind() == SDep::Data) {
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assert(NumPreds < UINT_MAX && "NumPreds will overflow!");
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assert(N->NumSuccs < UINT_MAX && "NumSuccs will overflow!");
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++NumPreds;
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++N->NumSuccs;
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}
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if (!N->isScheduled) {
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if (D.isWeak()) {
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++WeakPredsLeft;
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}
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else {
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assert(NumPredsLeft < UINT_MAX && "NumPredsLeft will overflow!");
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++NumPredsLeft;
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}
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}
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if (!isScheduled) {
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if (D.isWeak()) {
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++N->WeakSuccsLeft;
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}
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else {
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assert(N->NumSuccsLeft < UINT_MAX && "NumSuccsLeft will overflow!");
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++N->NumSuccsLeft;
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}
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}
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Preds.push_back(D);
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N->Succs.push_back(P);
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if (P.getLatency() != 0) {
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this->setDepthDirty();
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N->setHeightDirty();
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}
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return true;
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}
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/// removePred - This removes the specified edge as a pred of the current
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/// node if it exists. It also removes the current node as a successor of
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/// the specified node.
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void SUnit::removePred(const SDep &D) {
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// Find the matching predecessor.
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for (SmallVectorImpl<SDep>::iterator I = Preds.begin(), E = Preds.end();
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I != E; ++I)
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if (*I == D) {
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// Find the corresponding successor in N.
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SDep P = D;
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P.setSUnit(this);
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SUnit *N = D.getSUnit();
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SmallVectorImpl<SDep>::iterator Succ = std::find(N->Succs.begin(),
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N->Succs.end(), P);
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assert(Succ != N->Succs.end() && "Mismatching preds / succs lists!");
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N->Succs.erase(Succ);
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Preds.erase(I);
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// Update the bookkeeping.
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if (P.getKind() == SDep::Data) {
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assert(NumPreds > 0 && "NumPreds will underflow!");
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assert(N->NumSuccs > 0 && "NumSuccs will underflow!");
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--NumPreds;
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--N->NumSuccs;
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}
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if (!N->isScheduled) {
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if (D.isWeak())
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--WeakPredsLeft;
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else {
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assert(NumPredsLeft > 0 && "NumPredsLeft will underflow!");
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--NumPredsLeft;
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}
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}
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if (!isScheduled) {
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if (D.isWeak())
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--N->WeakSuccsLeft;
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else {
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assert(N->NumSuccsLeft > 0 && "NumSuccsLeft will underflow!");
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--N->NumSuccsLeft;
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}
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}
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if (P.getLatency() != 0) {
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this->setDepthDirty();
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N->setHeightDirty();
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}
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return;
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}
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}
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void SUnit::setDepthDirty() {
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if (!isDepthCurrent) return;
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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do {
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SUnit *SU = WorkList.pop_back_val();
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SU->isDepthCurrent = false;
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for (SUnit::const_succ_iterator I = SU->Succs.begin(),
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E = SU->Succs.end(); I != E; ++I) {
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SUnit *SuccSU = I->getSUnit();
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if (SuccSU->isDepthCurrent)
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WorkList.push_back(SuccSU);
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}
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} while (!WorkList.empty());
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}
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void SUnit::setHeightDirty() {
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if (!isHeightCurrent) return;
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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do {
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SUnit *SU = WorkList.pop_back_val();
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SU->isHeightCurrent = false;
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for (SUnit::const_pred_iterator I = SU->Preds.begin(),
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E = SU->Preds.end(); I != E; ++I) {
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SUnit *PredSU = I->getSUnit();
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if (PredSU->isHeightCurrent)
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WorkList.push_back(PredSU);
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}
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} while (!WorkList.empty());
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}
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/// setDepthToAtLeast - Update this node's successors to reflect the
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/// fact that this node's depth just increased.
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///
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void SUnit::setDepthToAtLeast(unsigned NewDepth) {
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if (NewDepth <= getDepth())
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return;
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setDepthDirty();
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Depth = NewDepth;
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isDepthCurrent = true;
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}
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/// setHeightToAtLeast - Update this node's predecessors to reflect the
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/// fact that this node's height just increased.
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///
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void SUnit::setHeightToAtLeast(unsigned NewHeight) {
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if (NewHeight <= getHeight())
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return;
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setHeightDirty();
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Height = NewHeight;
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isHeightCurrent = true;
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}
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/// ComputeDepth - Calculate the maximal path from the node to the exit.
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///
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void SUnit::ComputeDepth() {
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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do {
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SUnit *Cur = WorkList.back();
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bool Done = true;
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unsigned MaxPredDepth = 0;
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for (SUnit::const_pred_iterator I = Cur->Preds.begin(),
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E = Cur->Preds.end(); I != E; ++I) {
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SUnit *PredSU = I->getSUnit();
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if (PredSU->isDepthCurrent)
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MaxPredDepth = std::max(MaxPredDepth,
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PredSU->Depth + I->getLatency());
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else {
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Done = false;
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WorkList.push_back(PredSU);
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}
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}
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if (Done) {
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WorkList.pop_back();
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if (MaxPredDepth != Cur->Depth) {
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Cur->setDepthDirty();
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Cur->Depth = MaxPredDepth;
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}
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Cur->isDepthCurrent = true;
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}
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} while (!WorkList.empty());
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}
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/// ComputeHeight - Calculate the maximal path from the node to the entry.
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///
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void SUnit::ComputeHeight() {
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SmallVector<SUnit*, 8> WorkList;
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WorkList.push_back(this);
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do {
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SUnit *Cur = WorkList.back();
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bool Done = true;
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unsigned MaxSuccHeight = 0;
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for (SUnit::const_succ_iterator I = Cur->Succs.begin(),
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E = Cur->Succs.end(); I != E; ++I) {
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SUnit *SuccSU = I->getSUnit();
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if (SuccSU->isHeightCurrent)
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MaxSuccHeight = std::max(MaxSuccHeight,
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SuccSU->Height + I->getLatency());
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else {
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Done = false;
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WorkList.push_back(SuccSU);
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}
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}
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if (Done) {
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WorkList.pop_back();
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if (MaxSuccHeight != Cur->Height) {
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Cur->setHeightDirty();
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Cur->Height = MaxSuccHeight;
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}
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Cur->isHeightCurrent = true;
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}
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} while (!WorkList.empty());
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}
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void SUnit::biasCriticalPath() {
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if (NumPreds < 2)
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return;
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SUnit::pred_iterator BestI = Preds.begin();
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unsigned MaxDepth = BestI->getSUnit()->getDepth();
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for (SUnit::pred_iterator
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I = llvm::next(BestI), E = Preds.end(); I != E; ++I) {
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if (I->getKind() == SDep::Data && I->getSUnit()->getDepth() > MaxDepth)
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BestI = I;
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}
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if (BestI != Preds.begin())
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std::swap(*Preds.begin(), *BestI);
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
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/// a group of nodes flagged together.
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void SUnit::dump(const ScheduleDAG *G) const {
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dbgs() << "SU(" << NodeNum << "): ";
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G->dumpNode(this);
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}
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void SUnit::dumpAll(const ScheduleDAG *G) const {
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dump(G);
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dbgs() << " # preds left : " << NumPredsLeft << "\n";
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dbgs() << " # succs left : " << NumSuccsLeft << "\n";
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if (WeakPredsLeft)
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dbgs() << " # weak preds left : " << WeakPredsLeft << "\n";
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if (WeakSuccsLeft)
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dbgs() << " # weak succs left : " << WeakSuccsLeft << "\n";
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dbgs() << " # rdefs left : " << NumRegDefsLeft << "\n";
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dbgs() << " Latency : " << Latency << "\n";
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dbgs() << " Depth : " << getDepth() << "\n";
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dbgs() << " Height : " << getHeight() << "\n";
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if (Preds.size() != 0) {
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dbgs() << " Predecessors:\n";
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for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
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I != E; ++I) {
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dbgs() << " ";
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switch (I->getKind()) {
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case SDep::Data: dbgs() << "val "; break;
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case SDep::Anti: dbgs() << "anti"; break;
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case SDep::Output: dbgs() << "out "; break;
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case SDep::Order: dbgs() << "ch "; break;
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}
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dbgs() << "SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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dbgs() << " *";
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dbgs() << ": Latency=" << I->getLatency();
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if (I->isAssignedRegDep())
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dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
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dbgs() << "\n";
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}
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}
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if (Succs.size() != 0) {
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dbgs() << " Successors:\n";
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for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
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I != E; ++I) {
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dbgs() << " ";
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switch (I->getKind()) {
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case SDep::Data: dbgs() << "val "; break;
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case SDep::Anti: dbgs() << "anti"; break;
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case SDep::Output: dbgs() << "out "; break;
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case SDep::Order: dbgs() << "ch "; break;
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}
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dbgs() << "SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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dbgs() << " *";
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dbgs() << ": Latency=" << I->getLatency();
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if (I->isAssignedRegDep())
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dbgs() << " Reg=" << PrintReg(I->getReg(), G->TRI);
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dbgs() << "\n";
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}
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}
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dbgs() << "\n";
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}
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#endif
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#ifndef NDEBUG
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/// VerifyScheduledDAG - Verify that all SUnits were scheduled and that
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/// their state is consistent. Return the number of scheduled nodes.
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///
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unsigned ScheduleDAG::VerifyScheduledDAG(bool isBottomUp) {
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bool AnyNotSched = false;
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unsigned DeadNodes = 0;
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for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
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if (!SUnits[i].isScheduled) {
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if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
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++DeadNodes;
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continue;
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}
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if (!AnyNotSched)
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has not been scheduled!\n";
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AnyNotSched = true;
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}
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if (SUnits[i].isScheduled &&
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(isBottomUp ? SUnits[i].getHeight() : SUnits[i].getDepth()) >
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unsigned(INT_MAX)) {
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if (!AnyNotSched)
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has an unexpected "
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<< (isBottomUp ? "Height" : "Depth") << " value!\n";
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AnyNotSched = true;
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}
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if (isBottomUp) {
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if (SUnits[i].NumSuccsLeft != 0) {
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if (!AnyNotSched)
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has successors left!\n";
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AnyNotSched = true;
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}
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} else {
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if (SUnits[i].NumPredsLeft != 0) {
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if (!AnyNotSched)
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dbgs() << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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dbgs() << "has predecessors left!\n";
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AnyNotSched = true;
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}
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}
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}
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assert(!AnyNotSched);
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return SUnits.size() - DeadNodes;
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}
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#endif
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/// InitDAGTopologicalSorting - create the initial topological
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/// ordering from the DAG to be scheduled.
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///
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/// The idea of the algorithm is taken from
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/// "Online algorithms for managing the topological order of
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/// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
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/// This is the MNR algorithm, which was first introduced by
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/// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
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/// "Maintaining a topological order under edge insertions".
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///
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/// Short description of the algorithm:
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///
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/// Topological ordering, ord, of a DAG maps each node to a topological
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/// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
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///
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/// This means that if there is a path from the node X to the node Z,
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/// then ord(X) < ord(Z).
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///
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/// This property can be used to check for reachability of nodes:
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/// if Z is reachable from X, then an insertion of the edge Z->X would
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/// create a cycle.
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///
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/// The algorithm first computes a topological ordering for the DAG by
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/// initializing the Index2Node and Node2Index arrays and then tries to keep
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/// the ordering up-to-date after edge insertions by reordering the DAG.
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///
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/// On insertion of the edge X->Y, the algorithm first marks by calling DFS
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/// the nodes reachable from Y, and then shifts them using Shift to lie
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/// immediately after X in Index2Node.
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void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
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unsigned DAGSize = SUnits.size();
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std::vector<SUnit*> WorkList;
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WorkList.reserve(DAGSize);
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Index2Node.resize(DAGSize);
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Node2Index.resize(DAGSize);
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// Initialize the data structures.
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if (ExitSU)
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WorkList.push_back(ExitSU);
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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int NodeNum = SU->NodeNum;
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unsigned Degree = SU->Succs.size();
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// Temporarily use the Node2Index array as scratch space for degree counts.
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Node2Index[NodeNum] = Degree;
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// Is it a node without dependencies?
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if (Degree == 0) {
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assert(SU->Succs.empty() && "SUnit should have no successors");
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// Collect leaf nodes.
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WorkList.push_back(SU);
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}
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}
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int Id = DAGSize;
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while (!WorkList.empty()) {
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SUnit *SU = WorkList.back();
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WorkList.pop_back();
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if (SU->NodeNum < DAGSize)
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Allocate(SU->NodeNum, --Id);
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
|
|
I != E; ++I) {
|
|
SUnit *SU = I->getSUnit();
|
|
if (SU->NodeNum < DAGSize && !--Node2Index[SU->NodeNum])
|
|
// If all dependencies of the node are processed already,
|
|
// then the node can be computed now.
|
|
WorkList.push_back(SU);
|
|
}
|
|
}
|
|
|
|
Visited.resize(DAGSize);
|
|
|
|
#ifndef NDEBUG
|
|
// Check correctness of the ordering
|
|
for (unsigned i = 0, e = DAGSize; i != e; ++i) {
|
|
SUnit *SU = &SUnits[i];
|
|
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
|
|
I != E; ++I) {
|
|
assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
|
|
"Wrong topological sorting");
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/// AddPred - Updates the topological ordering to accommodate an edge
|
|
/// to be added from SUnit X to SUnit Y.
|
|
void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
|
|
int UpperBound, LowerBound;
|
|
LowerBound = Node2Index[Y->NodeNum];
|
|
UpperBound = Node2Index[X->NodeNum];
|
|
bool HasLoop = false;
|
|
// Is Ord(X) < Ord(Y) ?
|
|
if (LowerBound < UpperBound) {
|
|
// Update the topological order.
|
|
Visited.reset();
|
|
DFS(Y, UpperBound, HasLoop);
|
|
assert(!HasLoop && "Inserted edge creates a loop!");
|
|
// Recompute topological indexes.
|
|
Shift(Visited, LowerBound, UpperBound);
|
|
}
|
|
}
|
|
|
|
/// RemovePred - Updates the topological ordering to accommodate an
|
|
/// an edge to be removed from the specified node N from the predecessors
|
|
/// of the current node M.
|
|
void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
|
|
// InitDAGTopologicalSorting();
|
|
}
|
|
|
|
/// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
|
|
/// all nodes affected by the edge insertion. These nodes will later get new
|
|
/// topological indexes by means of the Shift method.
|
|
void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
|
|
bool &HasLoop) {
|
|
std::vector<const SUnit*> WorkList;
|
|
WorkList.reserve(SUnits.size());
|
|
|
|
WorkList.push_back(SU);
|
|
do {
|
|
SU = WorkList.back();
|
|
WorkList.pop_back();
|
|
Visited.set(SU->NodeNum);
|
|
for (int I = SU->Succs.size()-1; I >= 0; --I) {
|
|
unsigned s = SU->Succs[I].getSUnit()->NodeNum;
|
|
// Edges to non-SUnits are allowed but ignored (e.g. ExitSU).
|
|
if (s >= Node2Index.size())
|
|
continue;
|
|
if (Node2Index[s] == UpperBound) {
|
|
HasLoop = true;
|
|
return;
|
|
}
|
|
// Visit successors if not already and in affected region.
|
|
if (!Visited.test(s) && Node2Index[s] < UpperBound) {
|
|
WorkList.push_back(SU->Succs[I].getSUnit());
|
|
}
|
|
}
|
|
} while (!WorkList.empty());
|
|
}
|
|
|
|
/// Shift - Renumber the nodes so that the topological ordering is
|
|
/// preserved.
|
|
void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
|
|
int UpperBound) {
|
|
std::vector<int> L;
|
|
int shift = 0;
|
|
int i;
|
|
|
|
for (i = LowerBound; i <= UpperBound; ++i) {
|
|
// w is node at topological index i.
|
|
int w = Index2Node[i];
|
|
if (Visited.test(w)) {
|
|
// Unmark.
|
|
Visited.reset(w);
|
|
L.push_back(w);
|
|
shift = shift + 1;
|
|
} else {
|
|
Allocate(w, i - shift);
|
|
}
|
|
}
|
|
|
|
for (unsigned j = 0; j < L.size(); ++j) {
|
|
Allocate(L[j], i - shift);
|
|
i = i + 1;
|
|
}
|
|
}
|
|
|
|
|
|
/// WillCreateCycle - Returns true if adding an edge to TargetSU from SU will
|
|
/// create a cycle. If so, it is not safe to call AddPred(TargetSU, SU).
|
|
bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *TargetSU, SUnit *SU) {
|
|
// Is SU reachable from TargetSU via successor edges?
|
|
if (IsReachable(SU, TargetSU))
|
|
return true;
|
|
for (SUnit::pred_iterator
|
|
I = TargetSU->Preds.begin(), E = TargetSU->Preds.end(); I != E; ++I)
|
|
if (I->isAssignedRegDep() &&
|
|
IsReachable(SU, I->getSUnit()))
|
|
return true;
|
|
return false;
|
|
}
|
|
|
|
/// IsReachable - Checks if SU is reachable from TargetSU.
|
|
bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
|
|
const SUnit *TargetSU) {
|
|
// If insertion of the edge SU->TargetSU would create a cycle
|
|
// then there is a path from TargetSU to SU.
|
|
int UpperBound, LowerBound;
|
|
LowerBound = Node2Index[TargetSU->NodeNum];
|
|
UpperBound = Node2Index[SU->NodeNum];
|
|
bool HasLoop = false;
|
|
// Is Ord(TargetSU) < Ord(SU) ?
|
|
if (LowerBound < UpperBound) {
|
|
Visited.reset();
|
|
// There may be a path from TargetSU to SU. Check for it.
|
|
DFS(TargetSU, UpperBound, HasLoop);
|
|
}
|
|
return HasLoop;
|
|
}
|
|
|
|
/// Allocate - assign the topological index to the node n.
|
|
void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
|
|
Node2Index[n] = index;
|
|
Index2Node[index] = n;
|
|
}
|
|
|
|
ScheduleDAGTopologicalSort::
|
|
ScheduleDAGTopologicalSort(std::vector<SUnit> &sunits, SUnit *exitsu)
|
|
: SUnits(sunits), ExitSU(exitsu) {}
|
|
|
|
ScheduleHazardRecognizer::~ScheduleHazardRecognizer() {}
|