NewSU->isCommutable = true;
ComputeLatency(NewSU);
- SDep ChainPred;
+ // Record all the edges to and from the old SU, by category.
+ SmallVector<SDep, 4> ChainPreds;
SmallVector<SDep, 4> ChainSuccs;
SmallVector<SDep, 4> LoadPreds;
SmallVector<SDep, 4> NodePreds;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
if (I->isCtrl())
- ChainPred = *I;
+ ChainPreds.push_back(*I);
else if (I->getSUnit()->getNode() &&
I->getSUnit()->getNode()->isOperandOf(LoadNode))
LoadPreds.push_back(*I);
NodeSuccs.push_back(*I);
}
- if (ChainPred.getSUnit()) {
- RemovePred(SU, ChainPred);
+ // Now assign edges to the newly-created nodes.
+ for (unsigned i = 0, e = ChainPreds.size(); i != e; ++i) {
+ const SDep &Pred = ChainPreds[i];
+ RemovePred(SU, Pred);
if (isNewLoad)
- AddPred(LoadSU, ChainPred);
+ AddPred(LoadSU, Pred);
}
for (unsigned i = 0, e = LoadPreds.size(); i != e; ++i) {
const SDep &Pred = LoadPreds[i];
RemovePred(SU, Pred);
- if (isNewLoad) {
+ if (isNewLoad)
AddPred(LoadSU, Pred);
- }
}
for (unsigned i = 0, e = NodePreds.size(); i != e; ++i) {
const SDep &Pred = NodePreds[i];
AddPred(SuccDep, D);
}
}
- if (isNewLoad) {
- AddPred(NewSU, SDep(LoadSU, SDep::Order, LoadSU->Latency));
- }
+
+ // Add a data dependency to reflect that NewSU reads the value defined
+ // by LoadSU.
+ AddPred(NewSU, SDep(LoadSU, SDep::Data, LoadSU->Latency));
if (isNewLoad)
AvailableQueue->addNode(LoadSU);
return N->getValueType(NumRes);
}
+/// CheckForLiveRegDef - Return true and update live register vector if the
+/// specified register def of the specified SUnit clobbers any "live" registers.
+static bool CheckForLiveRegDef(SUnit *SU, unsigned Reg,
+ std::vector<SUnit*> &LiveRegDefs,
+ SmallSet<unsigned, 4> &RegAdded,
+ SmallVector<unsigned, 4> &LRegs,
+ const TargetRegisterInfo *TRI) {
+ bool Added = false;
+ if (LiveRegDefs[Reg] && LiveRegDefs[Reg] != SU) {
+ if (RegAdded.insert(Reg)) {
+ LRegs.push_back(Reg);
+ Added = true;
+ }
+ }
+ for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias)
+ if (LiveRegDefs[*Alias] && LiveRegDefs[*Alias] != SU) {
+ if (RegAdded.insert(*Alias)) {
+ LRegs.push_back(*Alias);
+ Added = true;
+ }
+ }
+ return Added;
+}
+
/// DelayForLiveRegsBottomUp - Returns true if it is necessary to delay
/// scheduling of the given node to satisfy live physical register dependencies.
/// If the specific node is the last one that's available to schedule, do
// If this node would clobber any "live" register, then it's not ready.
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
- if (I->isAssignedRegDep()) {
- unsigned Reg = I->getReg();
- if (LiveRegDefs[Reg] && LiveRegDefs[Reg] != I->getSUnit()) {
- if (RegAdded.insert(Reg))
- LRegs.push_back(Reg);
- }
- for (const unsigned *Alias = TRI->getAliasSet(Reg);
- *Alias; ++Alias)
- if (LiveRegDefs[*Alias] && LiveRegDefs[*Alias] != I->getSUnit()) {
- if (RegAdded.insert(*Alias))
- LRegs.push_back(*Alias);
- }
- }
+ if (I->isAssignedRegDep())
+ CheckForLiveRegDef(I->getSUnit(), I->getReg(), LiveRegDefs,
+ RegAdded, LRegs, TRI);
}
for (SDNode *Node = SU->getNode(); Node; Node = Node->getFlaggedNode()) {
+ if (Node->getOpcode() == ISD::INLINEASM) {
+ // Inline asm can clobber physical defs.
+ unsigned NumOps = Node->getNumOperands();
+ if (Node->getOperand(NumOps-1).getValueType() == MVT::Flag)
+ --NumOps; // Ignore the flag operand.
+
+ for (unsigned i = 2; i != NumOps;) {
+ unsigned Flags =
+ cast<ConstantSDNode>(Node->getOperand(i))->getZExtValue();
+ unsigned NumVals = (Flags & 0xffff) >> 3;
+
+ ++i; // Skip the ID value.
+ if ((Flags & 7) == 2 || (Flags & 7) == 6) {
+ // Check for def of register or earlyclobber register.
+ for (; NumVals; --NumVals, ++i) {
+ unsigned Reg = cast<RegisterSDNode>(Node->getOperand(i))->getReg();
+ if (TargetRegisterInfo::isPhysicalRegister(Reg))
+ CheckForLiveRegDef(SU, Reg, LiveRegDefs, RegAdded, LRegs, TRI);
+ }
+ } else
+ i += NumVals;
+ }
+ continue;
+ }
+
if (!Node->isMachineOpcode())
continue;
const TargetInstrDesc &TID = TII->get(Node->getMachineOpcode());
if (!TID.ImplicitDefs)
continue;
- for (const unsigned *Reg = TID.ImplicitDefs; *Reg; ++Reg) {
- if (LiveRegDefs[*Reg] && LiveRegDefs[*Reg] != SU) {
- if (RegAdded.insert(*Reg))
- LRegs.push_back(*Reg);
- }
- for (const unsigned *Alias = TRI->getAliasSet(*Reg);
- *Alias; ++Alias)
- if (LiveRegDefs[*Alias] && LiveRegDefs[*Alias] != SU) {
- if (RegAdded.insert(*Alias))
- LRegs.push_back(*Alias);
- }
- }
+ for (const unsigned *Reg = TID.ImplicitDefs; *Reg; ++Reg)
+ CheckForLiveRegDef(SU, *Reg, LiveRegDefs, RegAdded, LRegs, TRI);
}
return !LRegs.empty();
}
SUnits = &sunits;
// Add pseudo dependency edges for two-address nodes.
AddPseudoTwoAddrDeps();
+ // Reroute edges to nodes with multiple uses.
+ PrescheduleNodesWithMultipleUses();
// Calculate node priorities.
CalculateSethiUllmanNumbers();
}
// avoid spilling.
return 0;
if (Opc == TargetInstrInfo::EXTRACT_SUBREG ||
+ Opc == TargetInstrInfo::SUBREG_TO_REG ||
Opc == TargetInstrInfo::INSERT_SUBREG)
- // EXTRACT_SUBREG / INSERT_SUBREG should be close to its use to
- // facilitate coalescing.
+ // EXTRACT_SUBREG, INSERT_SUBREG, and SUBREG_TO_REG nodes should be
+ // close to their uses to facilitate coalescing.
return 0;
if (SU->NumSuccs == 0 && SU->NumPreds != 0)
// If SU does not have a register use, i.e. it doesn't produce a value
protected:
bool canClobber(const SUnit *SU, const SUnit *Op);
void AddPseudoTwoAddrDeps();
+ void PrescheduleNodesWithMultipleUses();
void CalculateSethiUllmanNumbers();
};
}
/// closestSucc - Returns the scheduled cycle of the successor which is
-/// closet to the current cycle.
+/// closest to the current cycle.
static unsigned closestSucc(const SUnit *SU) {
unsigned MaxHeight = 0;
for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
static unsigned calcMaxScratches(const SUnit *SU) {
unsigned Scratches = 0;
for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
- I != E; ++I)
+ I != E; ++I) {
if (I->isCtrl()) continue; // ignore chain preds
- Scratches++;
+ Scratches++;
+ }
return Scratches;
}
unsigned NumDefs = TII->get(N->getMachineOpcode()).getNumDefs();
const unsigned *ImpDefs = TII->get(N->getMachineOpcode()).getImplicitDefs();
assert(ImpDefs && "Caller should check hasPhysRegDefs");
- const unsigned *SUImpDefs =
- TII->get(SU->getNode()->getMachineOpcode()).getImplicitDefs();
- if (!SUImpDefs)
- return false;
- for (unsigned i = NumDefs, e = N->getNumValues(); i != e; ++i) {
- MVT VT = N->getValueType(i);
- if (VT == MVT::Flag || VT == MVT::Other)
- continue;
- if (!N->hasAnyUseOfValue(i))
+ for (const SDNode *SUNode = SU->getNode(); SUNode;
+ SUNode = SUNode->getFlaggedNode()) {
+ if (!SUNode->isMachineOpcode())
continue;
- unsigned Reg = ImpDefs[i - NumDefs];
- for (;*SUImpDefs; ++SUImpDefs) {
- unsigned SUReg = *SUImpDefs;
- if (TRI->regsOverlap(Reg, SUReg))
- return true;
+ const unsigned *SUImpDefs =
+ TII->get(SUNode->getMachineOpcode()).getImplicitDefs();
+ if (!SUImpDefs)
+ return false;
+ for (unsigned i = NumDefs, e = N->getNumValues(); i != e; ++i) {
+ MVT VT = N->getValueType(i);
+ if (VT == MVT::Flag || VT == MVT::Other)
+ continue;
+ if (!N->hasAnyUseOfValue(i))
+ continue;
+ unsigned Reg = ImpDefs[i - NumDefs];
+ for (;*SUImpDefs; ++SUImpDefs) {
+ unsigned SUReg = *SUImpDefs;
+ if (TRI->regsOverlap(Reg, SUReg))
+ return true;
+ }
}
}
return false;
}
+/// PrescheduleNodesWithMultipleUses - Nodes with multiple uses
+/// are not handled well by the general register pressure reduction
+/// heuristics. When presented with code like this:
+///
+/// N
+/// / |
+/// / |
+/// U store
+/// |
+/// ...
+///
+/// the heuristics tend to push the store up, but since the
+/// operand of the store has another use (U), this would increase
+/// the length of that other use (the U->N edge).
+///
+/// This function transforms code like the above to route U's
+/// dependence through the store when possible, like this:
+///
+/// N
+/// ||
+/// ||
+/// store
+/// |
+/// U
+/// |
+/// ...
+///
+/// This results in the store being scheduled immediately
+/// after N, which shortens the U->N live range, reducing
+/// register pressure.
+///
+template<class SF>
+void RegReductionPriorityQueue<SF>::PrescheduleNodesWithMultipleUses() {
+ // Visit all the nodes in topological order, working top-down.
+ for (unsigned i = 0, e = SUnits->size(); i != e; ++i) {
+ SUnit *SU = &(*SUnits)[i];
+ // For now, only look at nodes with no data successors, such as stores.
+ // These are especially important, due to the heuristics in
+ // getNodePriority for nodes with no data successors.
+ if (SU->NumSuccs != 0)
+ continue;
+ // For now, only look at nodes with exactly one data predecessor.
+ if (SU->NumPreds != 1)
+ continue;
+ // Avoid prescheduling copies to virtual registers, which don't behave
+ // like other nodes from the perspective of scheduling heuristics.
+ if (SDNode *N = SU->getNode())
+ if (N->getOpcode() == ISD::CopyToReg &&
+ TargetRegisterInfo::isVirtualRegister
+ (cast<RegisterSDNode>(N->getOperand(1))->getReg()))
+ continue;
+
+ // Locate the single data predecessor.
+ SUnit *PredSU = 0;
+ for (SUnit::const_pred_iterator II = SU->Preds.begin(),
+ EE = SU->Preds.end(); II != EE; ++II)
+ if (!II->isCtrl()) {
+ PredSU = II->getSUnit();
+ break;
+ }
+ assert(PredSU);
+
+ // Don't rewrite edges that carry physregs, because that requires additional
+ // support infrastructure.
+ if (PredSU->hasPhysRegDefs)
+ continue;
+ // Short-circuit the case where SU is PredSU's only data successor.
+ if (PredSU->NumSuccs == 1)
+ continue;
+ // Avoid prescheduling to copies from virtual registers, which don't behave
+ // like other nodes from the perspective of scheduling // heuristics.
+ if (SDNode *N = SU->getNode())
+ if (N->getOpcode() == ISD::CopyFromReg &&
+ TargetRegisterInfo::isVirtualRegister
+ (cast<RegisterSDNode>(N->getOperand(1))->getReg()))
+ continue;
+
+ // Perform checks on the successors of PredSU.
+ for (SUnit::const_succ_iterator II = PredSU->Succs.begin(),
+ EE = PredSU->Succs.end(); II != EE; ++II) {
+ SUnit *PredSuccSU = II->getSUnit();
+ if (PredSuccSU == SU) continue;
+ // If PredSU has another successor with no data successors, for
+ // now don't attempt to choose either over the other.
+ if (PredSuccSU->NumSuccs == 0)
+ goto outer_loop_continue;
+ // Don't break physical register dependencies.
+ if (SU->hasPhysRegClobbers && PredSuccSU->hasPhysRegDefs)
+ if (canClobberPhysRegDefs(PredSuccSU, SU, TII, TRI))
+ goto outer_loop_continue;
+ // Don't introduce graph cycles.
+ if (scheduleDAG->IsReachable(SU, PredSuccSU))
+ goto outer_loop_continue;
+ }
+
+ // Ok, the transformation is safe and the heuristics suggest it is
+ // profitable. Update the graph.
+ DOUT << "Prescheduling SU # " << SU->NodeNum
+ << " next to PredSU # " << PredSU->NodeNum
+ << " to guide scheduling in the presence of multiple uses\n";
+ for (unsigned i = 0; i != PredSU->Succs.size(); ++i) {
+ SDep Edge = PredSU->Succs[i];
+ assert(!Edge.isAssignedRegDep());
+ SUnit *SuccSU = Edge.getSUnit();
+ if (SuccSU != SU) {
+ Edge.setSUnit(PredSU);
+ scheduleDAG->RemovePred(SuccSU, Edge);
+ scheduleDAG->AddPred(SU, Edge);
+ Edge.setSUnit(SU);
+ scheduleDAG->AddPred(SuccSU, Edge);
+ --i;
+ }
+ }
+ outer_loop_continue:;
+ }
+}
+
/// AddPseudoTwoAddrDeps - If two nodes share an operand and one of them uses
/// it as a def&use operand. Add a pseudo control edge from it to the other
/// node (if it won't create a cycle) so the two-address one will be scheduled
if (SuccSU->getHeight() < SU->getHeight() &&
(SU->getHeight() - SuccSU->getHeight()) > 1)
continue;
+ // Skip past COPY_TO_REGCLASS nodes, so that the pseudo edge
+ // constrains whatever is using the copy, instead of the copy
+ // itself. In the case that the copy is coalesced, this
+ // preserves the intent of the pseudo two-address heurietics.
+ while (SuccSU->Succs.size() == 1 &&
+ SuccSU->getNode()->isMachineOpcode() &&
+ SuccSU->getNode()->getMachineOpcode() ==
+ TargetInstrInfo::COPY_TO_REGCLASS)
+ SuccSU = SuccSU->Succs.front().getSUnit();
+ // Don't constrain non-instruction nodes.
if (!SuccSU->getNode() || !SuccSU->getNode()->isMachineOpcode())
continue;
// Don't constrain nodes with physical register defs if the
// predecessor can clobber them.
- if (SuccSU->hasPhysRegDefs) {
+ if (SuccSU->hasPhysRegDefs && SU->hasPhysRegClobbers) {
if (canClobberPhysRegDefs(SuccSU, SU, TII, TRI))
continue;
}
- // Don't constrain extract_subreg / insert_subreg; these may be
- // coalesced away. We want them close to their uses.
+ // Don't constrain EXTRACT_SUBREG, INSERT_SUBREG, and SUBREG_TO_REG;
+ // these may be coalesced away. We want them close to their uses.
unsigned SuccOpc = SuccSU->getNode()->getMachineOpcode();
if (SuccOpc == TargetInstrInfo::EXTRACT_SUBREG ||
- SuccOpc == TargetInstrInfo::INSERT_SUBREG)
+ SuccOpc == TargetInstrInfo::INSERT_SUBREG ||
+ SuccOpc == TargetInstrInfo::SUBREG_TO_REG)
continue;
if ((!canClobber(SuccSU, DUSU) ||
(hasCopyToRegUse(SU) && !hasCopyToRegUse(SuccSU)) ||
//===----------------------------------------------------------------------===//
llvm::ScheduleDAGSDNodes *
-llvm::createBURRListDAGScheduler(SelectionDAGISel *IS, bool) {
+llvm::createBURRListDAGScheduler(SelectionDAGISel *IS, CodeGenOpt::Level) {
const TargetMachine &TM = IS->TM;
const TargetInstrInfo *TII = TM.getInstrInfo();
const TargetRegisterInfo *TRI = TM.getRegisterInfo();
}
llvm::ScheduleDAGSDNodes *
-llvm::createTDRRListDAGScheduler(SelectionDAGISel *IS, bool) {
+llvm::createTDRRListDAGScheduler(SelectionDAGISel *IS, CodeGenOpt::Level) {
const TargetMachine &TM = IS->TM;
const TargetInstrInfo *TII = TM.getInstrInfo();
const TargetRegisterInfo *TRI = TM.getRegisterInfo();
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