void SUnit::biasCriticalPath() {
if (NumPreds < 2)
return;
SUnit::pred_iterator BestI = Preds.begin();
unsigned MaxDepth = BestI->getSUnit()->getDepth();
for (SUnit::pred_iterator I = std::next(BestI), E = Preds.end(); I != E;
++I) {
if (I->getKind() == SDep::Data && I->getSUnit()->getDepth() > MaxDepth)
BestI = I;
}
if (BestI != Preds.begin())
std::swap(*Preds.begin(), *BestI);
}
/// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
/// create a cycle.
bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
if (IsReachable(TargetSU, SU))
return true;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I)
if (I->isAssignedRegDep() &&
IsReachable(TargetSU, I->getSUnit()))
return true;
return false;
}
unsigned
ResourcePriorityQueue::numberRCValPredInSU(SUnit *SU, unsigned RCId) {
unsigned NumberDeps = 0;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
if (I->isCtrl())
continue;
SUnit *PredSU = I->getSUnit();
const SDNode *ScegN = PredSU->getNode();
if (!ScegN)
continue;
// If value is passed to CopyToReg, it is probably
// live outside BB.
switch (ScegN->getOpcode()) {
default:
break;
case ISD::TokenFactor:
break;
case ISD::CopyFromReg:
NumberDeps++;
break;
case ISD::CopyToReg:
break;
case ISD::INLINEASM:
break;
}
if (!ScegN->isMachineOpcode())
continue;
for (unsigned i = 0, e = ScegN->getNumValues(); i != e; ++i) {
MVT VT = ScegN->getSimpleValueType(i);
if (TLI->isTypeLegal(VT)
&& (TLI->getRegClassFor(VT)->getID() == RCId)) {
NumberDeps++;
break;
}
}
}
return NumberDeps;
}
/// CriticalPathStep - Return the next SUnit after SU on the bottom-up
/// critical path.
static SDep *CriticalPathStep(SUnit *SU) {
SDep *Next = 0;
unsigned NextDepth = 0;
// Find the predecessor edge with the greatest depth.
for (SUnit::pred_iterator P = SU->Preds.begin(), PE = SU->Preds.end();
P != PE; ++P) {
SUnit *PredSU = P->getSUnit();
unsigned PredLatency = P->getLatency();
unsigned PredTotalLatency = PredSU->getDepth() + PredLatency;
// In the case of a latency tie, prefer an anti-dependency edge over
// other types of edges.
if (NextDepth < PredTotalLatency ||
(NextDepth == PredTotalLatency && P->getKind() == SDep::Anti)) {
NextDepth = PredTotalLatency;
Next = &*P;
}
}
return Next;
}
/// Main resource tracking point.
void ResourcePriorityQueue::scheduledNode(SUnit *SU) {
// Use NULL entry as an event marker to reset
// the DFA state.
if (!SU) {
ResourcesModel->clearResources();
Packet.clear();
return;
}
const SDNode *ScegN = SU->getNode();
// Update reg pressure tracking.
// First update current node.
if (ScegN->isMachineOpcode()) {
// Estimate generated regs.
for (unsigned i = 0, e = ScegN->getNumValues(); i != e; ++i) {
MVT VT = ScegN->getSimpleValueType(i);
if (TLI->isTypeLegal(VT)) {
const TargetRegisterClass *RC = TLI->getRegClassFor(VT);
if (RC)
RegPressure[RC->getID()] += numberRCValSuccInSU(SU, RC->getID());
}
}
// Estimate killed regs.
for (unsigned i = 0, e = ScegN->getNumOperands(); i != e; ++i) {
const SDValue &Op = ScegN->getOperand(i);
MVT VT = Op.getNode()->getSimpleValueType(Op.getResNo());
if (TLI->isTypeLegal(VT)) {
const TargetRegisterClass *RC = TLI->getRegClassFor(VT);
if (RC) {
if (RegPressure[RC->getID()] >
(numberRCValPredInSU(SU, RC->getID())))
RegPressure[RC->getID()] -= numberRCValPredInSU(SU, RC->getID());
else RegPressure[RC->getID()] = 0;
}
}
}
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
if (I->isCtrl() || (I->getSUnit()->NumRegDefsLeft == 0))
continue;
--I->getSUnit()->NumRegDefsLeft;
}
}
// Reserve resources for this SU.
reserveResources(SU);
// Adjust number of parallel live ranges.
// Heuristic is simple - node with no data successors reduces
// number of live ranges. All others, increase it.
unsigned NumberNonControlDeps = 0;
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
adjustPriorityOfUnscheduledPreds(I->getSUnit());
if (!I->isCtrl())
NumberNonControlDeps++;
}
if (!NumberNonControlDeps) {
if (ParallelLiveRanges >= SU->NumPreds)
ParallelLiveRanges -= SU->NumPreds;
else
ParallelLiveRanges = 0;
}
else
ParallelLiveRanges += SU->NumRegDefsLeft;
// Track parallel live chains.
HorizontalVerticalBalance += (SU->Succs.size() - numberCtrlDepsInSU(SU));
HorizontalVerticalBalance -= (SU->Preds.size() - numberCtrlPredInSU(SU));
}
void PatmosPostRASchedStrategy::postprocessDAG(ScheduleDAGPostRA *dag)
{
DAG = dag;
SUnit *CFL = NULL;
// Find the inline asm statement, if any. Note that asm is a barrier,
// therefore there is at most one CFL or inline asm.
SUnit *Asm = NULL;
// Push up loads to ensure load delay slot across BBs
// TODO For some reasons, loads do not always have exit edges, and a latency
// of 1; find out why. Happens e.g. in coremark with 16k methods setup.
for (std::vector<SUnit>::reverse_iterator it = DAG->SUnits.rbegin(),
ie = DAG->SUnits.rend(); it != ie; it++) {
MachineInstr *MI = it->getInstr();
if (!MI) continue;
if (MI->mayLoad()) {
SDep Dep(&*it, SDep::Artificial);
Dep.setLatency(computeExitLatency(*it));
DAG->ExitSU.addPred(Dep);
}
}
// Find the branch/call/ret instruction if available
for (std::vector<SUnit>::reverse_iterator it = DAG->SUnits.rbegin(),
ie = DAG->SUnits.rend(); it != ie; it++)
{
MachineInstr *MI = it->getInstr();
if (!MI) continue;
if (isPatmosCFL(MI->getOpcode(), MI->getDesc().TSFlags)) {
CFL = &*it;
break;
}
if (MI->isInlineAsm()) {
Asm = &*it;
break;
}
}
const PatmosSubtarget *PST = PTM.getSubtargetImpl();
unsigned DelaySlot = CFL ? PST->getDelaySlotCycles(CFL->getInstr()) : 0;
if (CFL) {
// RET and CALL have implicit deps on the return values and call
// arguments. Remove all those edges to schedule them into the delay slot
// if the registers are not actually used by CALL and RET
if (CFL->getInstr()->isReturn() || CFL->getInstr()->isCall())
removeImplicitCFLDeps(*CFL);
// Add an artificial dep from CFL to exit for the delay slot
SDep DelayDep(CFL, SDep::Artificial);
DelayDep.setLatency(DelaySlot + 1);
DAG->ExitSU.addPred(DelayDep);
CFL->isScheduleLow = true;
if (PTM.getSubtargetImpl()->getCFLType() != PatmosSubtarget::CFL_DELAYED) {
// Push up single instructions that can be scheduled in the same
// cycle as the branch
unsigned LowCount = 0;
SUnit *LowSU = 0;
for (std::vector<SUnit>::reverse_iterator it = DAG->SUnits.rbegin(),
ie = DAG->SUnits.rend(); it != ie; it++) {
if (&*it == CFL) continue;
MachineInstr *MI = it->getInstr();
if (!MI) continue;
if (it->getHeight() <= DelaySlot) {
LowCount++;
if (PII.canIssueInSlot(MI, LowCount)) {
LowSU = &*it;
}
}
}
if (LowSU && LowCount == 1) {
SDep Dep(LowSU, SDep::Artificial);
Dep.setLatency(DelaySlot + 1);
DAG->ExitSU.addPred(Dep);
}
}
if (PTM.getSubtargetImpl()->getCFLType() == PatmosSubtarget::CFL_NON_DELAYED) {
// Add dependencies from all other instructions to exit
for (std::vector<SUnit>::reverse_iterator it = DAG->SUnits.rbegin(),
ie = DAG->SUnits.rend(); it != ie; it++) {
if (&*it == CFL) continue;
MachineInstr *MI = it->getInstr();
if (!MI) continue;
SDep Dep(&*it, SDep::Artificial);
Dep.setLatency(DelaySlot + 1);
DAG->ExitSU.addPred(Dep);
}
}
}
// Add an exit delay between loads and inline asm, in case asm is empty
if (Asm) {
std::vector<SUnit*> PredLoads;
for (SUnit::pred_iterator it = Asm->Preds.begin(), ie = Asm->Preds.end();
it != ie; it++)
{
if (!it->getSUnit()) continue;
MachineInstr *MI = it->getSUnit()->getInstr();
// Check for loads
if (!MI || !MI->mayLoad()) continue;
PredLoads.push_back(it->getSUnit());
}
for (std::vector<SUnit*>::iterator it = PredLoads.begin(),
ie = PredLoads.end(); it != ie; it++)
{
// Add a delay between loads and inline-asm, even if the operand is not
// used.
SDep Dep(*it, SDep::Artificial);
Dep.setLatency( computeExitLatency(**it) );
Asm->addPred(Dep);
}
}
// remove barriers between loads/stores with different memory type
removeTypedMemBarriers();
// remove any dependency between instructions with mutually exclusive
// predicates
removeExclusivePredDeps();
// TODO SWS and LWS do not have ST as implicit def edges
// TODO CALL has chain edges to all SWS/.. instructions, remove
// TODO remove edges from MUL to other MULs to overlap MUL and MFS for
// pipelined muls.
}
unsigned CriticalAntiDepBreaker::
BreakAntiDependencies(std::vector<SUnit>& SUnits,
MachineBasicBlock::iterator& Begin,
MachineBasicBlock::iterator& End,
unsigned InsertPosIndex) {
// The code below assumes that there is at least one instruction,
// so just duck out immediately if the block is empty.
if (SUnits.empty()) return 0;
// Find the node at the bottom of the critical path.
SUnit *Max = 0;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
SUnit *SU = &SUnits[i];
if (!Max || SU->getDepth() + SU->Latency > Max->getDepth() + Max->Latency)
Max = SU;
}
#ifndef NDEBUG
{
DEBUG(errs() << "Critical path has total latency "
<< (Max->getDepth() + Max->Latency) << "\n");
DEBUG(errs() << "Available regs:");
for (unsigned Reg = 0; Reg < TRI->getNumRegs(); ++Reg) {
if (KillIndices[Reg] == ~0u)
DEBUG(errs() << " " << TRI->getName(Reg));
}
DEBUG(errs() << '\n');
}
#endif
// Track progress along the critical path through the SUnit graph as we walk
// the instructions.
SUnit *CriticalPathSU = Max;
MachineInstr *CriticalPathMI = CriticalPathSU->getInstr();
// Consider this pattern:
// A = ...
// ... = A
// A = ...
// ... = A
// A = ...
// ... = A
// A = ...
// ... = A
// There are three anti-dependencies here, and without special care,
// we'd break all of them using the same register:
// A = ...
// ... = A
// B = ...
// ... = B
// B = ...
// ... = B
// B = ...
// ... = B
// because at each anti-dependence, B is the first register that
// isn't A which is free. This re-introduces anti-dependencies
// at all but one of the original anti-dependencies that we were
// trying to break. To avoid this, keep track of the most recent
// register that each register was replaced with, avoid
// using it to repair an anti-dependence on the same register.
// This lets us produce this:
// A = ...
// ... = A
// B = ...
// ... = B
// C = ...
// ... = C
// B = ...
// ... = B
// This still has an anti-dependence on B, but at least it isn't on the
// original critical path.
//
// TODO: If we tracked more than one register here, we could potentially
// fix that remaining critical edge too. This is a little more involved,
// because unlike the most recent register, less recent registers should
// still be considered, though only if no other registers are available.
unsigned LastNewReg[TargetRegisterInfo::FirstVirtualRegister] = {};
// Attempt to break anti-dependence edges on the critical path. Walk the
// instructions from the bottom up, tracking information about liveness
// as we go to help determine which registers are available.
unsigned Broken = 0;
unsigned Count = InsertPosIndex - 1;
for (MachineBasicBlock::iterator I = End, E = Begin;
I != E; --Count) {
MachineInstr *MI = --I;
// Check if this instruction has a dependence on the critical path that
// is an anti-dependence that we may be able to break. If it is, set
// AntiDepReg to the non-zero register associated with the anti-dependence.
//
// We limit our attention to the critical path as a heuristic to avoid
// breaking anti-dependence edges that aren't going to significantly
// impact the overall schedule. There are a limited number of registers
// and we want to save them for the important edges.
//
// TODO: Instructions with multiple defs could have multiple
// anti-dependencies. The current code here only knows how to break one
// edge per instruction. Note that we'd have to be able to break all of
// the anti-dependencies in an instruction in order to be effective.
unsigned AntiDepReg = 0;
if (MI == CriticalPathMI) {
if (SDep *Edge = CriticalPathStep(CriticalPathSU)) {
SUnit *NextSU = Edge->getSUnit();
// Only consider anti-dependence edges.
if (Edge->getKind() == SDep::Anti) {
AntiDepReg = Edge->getReg();
assert(AntiDepReg != 0 && "Anti-dependence on reg0?");
if (!AllocatableSet.test(AntiDepReg))
// Don't break anti-dependencies on non-allocatable registers.
AntiDepReg = 0;
else if (KeepRegs.count(AntiDepReg))
// Don't break anti-dependencies if an use down below requires
// this exact register.
AntiDepReg = 0;
else {
// If the SUnit has other dependencies on the SUnit that it
// anti-depends on, don't bother breaking the anti-dependency
// since those edges would prevent such units from being
// scheduled past each other regardless.
//
// Also, if there are dependencies on other SUnits with the
// same register as the anti-dependency, don't attempt to
// break it.
for (SUnit::pred_iterator P = CriticalPathSU->Preds.begin(),
PE = CriticalPathSU->Preds.end(); P != PE; ++P)
if (P->getSUnit() == NextSU ?
(P->getKind() != SDep::Anti || P->getReg() != AntiDepReg) :
(P->getKind() == SDep::Data && P->getReg() == AntiDepReg)) {
AntiDepReg = 0;
break;
}
}
}
CriticalPathSU = NextSU;
CriticalPathMI = CriticalPathSU->getInstr();
} else {
// We've reached the end of the critical path.
CriticalPathSU = 0;
CriticalPathMI = 0;
}
}
PrescanInstruction(MI);
if (MI->getDesc().hasExtraDefRegAllocReq())
// If this instruction's defs have special allocation requirement, don't
// break this anti-dependency.
AntiDepReg = 0;
else if (AntiDepReg) {
// If this instruction has a use of AntiDepReg, breaking it
// is invalid.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (MO.isUse() && AntiDepReg == Reg) {
AntiDepReg = 0;
break;
}
}
}
// Determine AntiDepReg's register class, if it is live and is
// consistently used within a single class.
const TargetRegisterClass *RC = AntiDepReg != 0 ? Classes[AntiDepReg] : 0;
assert((AntiDepReg == 0 || RC != NULL) &&
"Register should be live if it's causing an anti-dependence!");
if (RC == reinterpret_cast<TargetRegisterClass *>(-1))
AntiDepReg = 0;
// Look for a suitable register to use to break the anti-depenence.
//
// TODO: Instead of picking the first free register, consider which might
// be the best.
if (AntiDepReg != 0) {
if (unsigned NewReg = findSuitableFreeRegister(AntiDepReg,
LastNewReg[AntiDepReg],
RC)) {
DEBUG(errs() << "Breaking anti-dependence edge on "
<< TRI->getName(AntiDepReg)
<< " with " << RegRefs.count(AntiDepReg) << " references"
<< " using " << TRI->getName(NewReg) << "!\n");
// Update the references to the old register to refer to the new
// register.
std::pair<std::multimap<unsigned, MachineOperand *>::iterator,
std::multimap<unsigned, MachineOperand *>::iterator>
Range = RegRefs.equal_range(AntiDepReg);
for (std::multimap<unsigned, MachineOperand *>::iterator
Q = Range.first, QE = Range.second; Q != QE; ++Q)
Q->second->setReg(NewReg);
// We just went back in time and modified history; the
// liveness information for the anti-depenence reg is now
// inconsistent. Set the state as if it were dead.
Classes[NewReg] = Classes[AntiDepReg];
DefIndices[NewReg] = DefIndices[AntiDepReg];
KillIndices[NewReg] = KillIndices[AntiDepReg];
assert(((KillIndices[NewReg] == ~0u) !=
(DefIndices[NewReg] == ~0u)) &&
"Kill and Def maps aren't consistent for NewReg!");
Classes[AntiDepReg] = 0;
DefIndices[AntiDepReg] = KillIndices[AntiDepReg];
KillIndices[AntiDepReg] = ~0u;
assert(((KillIndices[AntiDepReg] == ~0u) !=
(DefIndices[AntiDepReg] == ~0u)) &&
"Kill and Def maps aren't consistent for AntiDepReg!");
RegRefs.erase(AntiDepReg);
LastNewReg[AntiDepReg] = NewReg;
++Broken;
}
}
ScanInstruction(MI, Count);
}
return Broken;
}