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If a node that defines a physical register that is expensive to copy. The

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scheduler will try a number of tricks in order to avoid generating the
copies. This may not be possible in case the node produces a chain value
that prevent movement. Try unfolding the load from the node before to allow
it to be moved / cloned.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42625 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2007-10-05 01:39:18 +00:00
parent 75b4e46b8a
commit f10c973797
3 changed files with 177 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
lib/CodeGen/SelectionDAG/ScheduleDAG.cpp
View File

@@ -68,6 +68,7 @@ SUnit *ScheduleDAG::Clone(SUnit *Old) {
return SU;
}
/// BuildSchedUnits - Build SUnits from the selection dag that we are input.
/// This SUnit graph is similar to the SelectionDAG, but represents flagged
/// together nodes with a single SUnit.
@@ -77,8 +78,6 @@ void ScheduleDAG::BuildSchedUnits() {
// invalidated.
SUnits.reserve(std::distance(DAG.allnodes_begin(), DAG.allnodes_end()));
const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
for (SelectionDAG::allnodes_iterator NI = DAG.allnodes_begin(),
E = DAG.allnodes_end(); NI != E; ++NI) {
if (isPassiveNode(NI)) // Leaf node, e.g. a TargetImmediate.
@@ -131,32 +130,8 @@ void ScheduleDAG::BuildSchedUnits() {
// Update the SUnit
NodeSUnit->Node = N;
SUnitMap[N].push_back(NodeSUnit);
// Compute the latency for the node. We use the sum of the latencies for
// all nodes flagged together into this SUnit.
if (InstrItins.isEmpty()) {
// No latency information.
NodeSUnit->Latency = 1;
} else {
NodeSUnit->Latency = 0;
if (N->isTargetOpcode()) {
unsigned SchedClass = TII->getSchedClass(N->getTargetOpcode());
InstrStage *S = InstrItins.begin(SchedClass);
InstrStage *E = InstrItins.end(SchedClass);
for (; S != E; ++S)
NodeSUnit->Latency += S->Cycles;
}
for (unsigned i = 0, e = NodeSUnit->FlaggedNodes.size(); i != e; ++i) {
SDNode *FNode = NodeSUnit->FlaggedNodes[i];
if (FNode->isTargetOpcode()) {
unsigned SchedClass = TII->getSchedClass(FNode->getTargetOpcode());
InstrStage *S = InstrItins.begin(SchedClass);
InstrStage *E = InstrItins.end(SchedClass);
for (; S != E; ++S)
NodeSUnit->Latency += S->Cycles;
}
}
}
ComputeLatency(NodeSUnit);
}
// Pass 2: add the preds, succs, etc.
@@ -214,6 +189,36 @@ void ScheduleDAG::BuildSchedUnits() {
return;
}
void ScheduleDAG::ComputeLatency(SUnit *SU) {
const InstrItineraryData &InstrItins = TM.getInstrItineraryData();
// Compute the latency for the node. We use the sum of the latencies for
// all nodes flagged together into this SUnit.
if (InstrItins.isEmpty()) {
// No latency information.
SU->Latency = 1;
} else {
SU->Latency = 0;
if (SU->Node->isTargetOpcode()) {
unsigned SchedClass = TII->getSchedClass(SU->Node->getTargetOpcode());
InstrStage *S = InstrItins.begin(SchedClass);
InstrStage *E = InstrItins.end(SchedClass);
for (; S != E; ++S)
SU->Latency += S->Cycles;
}
for (unsigned i = 0, e = SU->FlaggedNodes.size(); i != e; ++i) {
SDNode *FNode = SU->FlaggedNodes[i];
if (FNode->isTargetOpcode()) {
unsigned SchedClass = TII->getSchedClass(FNode->getTargetOpcode());
InstrStage *S = InstrItins.begin(SchedClass);
InstrStage *E = InstrItins.end(SchedClass);
for (; S != E; ++S)
SU->Latency += S->Cycles;
}
}
}
}
void ScheduleDAG::CalculateDepths() {
std::vector<std::pair<SUnit*, unsigned> > WorkList;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i)

165
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
View File

@@ -34,6 +34,7 @@
using namespace llvm;
STATISTIC(NumBacktracks, "Number of times scheduler backtraced");
STATISTIC(NumUnfolds, "Number of nodes unfolded");
STATISTIC(NumDups, "Number of duplicated nodes");
STATISTIC(NumCCCopies, "Number of cross class copies");
@@ -385,32 +386,145 @@ void ScheduleDAGRRList::BacktrackBottomUp(SUnit *SU, unsigned BtCycle,
++NumBacktracks;
}
/// isSafeToCopy - True if the SUnit for the given SDNode can safely cloned,
/// i.e. the node does not produce a flag, it does not read a flag and it does
/// not have an incoming chain.
static bool isSafeToCopy(SDNode *N) {
if (!N)
return true;
for (unsigned i = 0, e = N->getNumValues(); i != e; ++i)
if (N->getValueType(i) == MVT::Flag)
return false;
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
const SDOperand &Op = N->getOperand(i);
MVT::ValueType VT = Op.Val->getValueType(Op.ResNo);
if (VT == MVT::Other || VT == MVT::Flag)
return false;
}
return true;
}
/// CopyAndMoveSuccessors - Clone the specified node and move its scheduled
/// successors to the newly created node.
SUnit *ScheduleDAGRRList::CopyAndMoveSuccessors(SUnit *SU) {
DOUT << "Duplicating SU # " << SU->NodeNum << "\n";
if (SU->FlaggedNodes.size())
return NULL;
SUnit *NewSU = Clone(SU);
SDNode *N = SU->Node;
if (!N)
return NULL;
SUnit *NewSU;
for (unsigned i = 0, e = N->getNumValues(); i != e; ++i)
if (N->getValueType(i) == MVT::Flag)
return NULL;
bool TryUnfold = false;
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
const SDOperand &Op = N->getOperand(i);
MVT::ValueType VT = Op.Val->getValueType(Op.ResNo);
if (VT == MVT::Flag)
return NULL;
else if (VT == MVT::Other)
TryUnfold = true;
}
if (TryUnfold) {
SmallVector<SDNode*, 4> NewNodes;
if (!MRI->unfoldMemoryOperand(DAG, N, NewNodes))
return NULL;
DOUT << "Unfolding SU # " << SU->NodeNum << "\n";
assert(NewNodes.size() == 2 && "Expected a load folding node!");
N = NewNodes[1];
SDNode *LoadNode = NewNodes[0];
std::vector<SDNode*> Deleted;
unsigned NumVals = N->getNumValues();
unsigned OldNumVals = SU->Node->getNumValues();
for (unsigned i = 0; i != NumVals; ++i)
DAG.ReplaceAllUsesOfValueWith(SDOperand(SU->Node, i),
SDOperand(N, i), Deleted);
DAG.ReplaceAllUsesOfValueWith(SDOperand(SU->Node, OldNumVals-1),
SDOperand(LoadNode, 1), Deleted);
SUnit *LoadSU = NewSUnit(LoadNode);
SUnit *NewSU = NewSUnit(N);
SUnitMap[LoadNode].push_back(LoadSU);
SUnitMap[N].push_back(NewSU);
const TargetInstrDescriptor *TID = &TII->get(LoadNode->getTargetOpcode());
for (unsigned i = 0; i != TID->numOperands; ++i) {
if (TID->getOperandConstraint(i, TOI::TIED_TO) != -1) {
LoadSU->isTwoAddress = true;
break;
}
}
if (TID->Flags & M_COMMUTABLE)
LoadSU->isCommutable = true;
TID = &TII->get(N->getTargetOpcode());
for (unsigned i = 0; i != TID->numOperands; ++i) {
if (TID->getOperandConstraint(i, TOI::TIED_TO) != -1) {
NewSU->isTwoAddress = true;
break;
}
}
if (TID->Flags & M_COMMUTABLE)
NewSU->isCommutable = true;
// FIXME: Calculate height / depth and propagate the changes?
LoadSU->Depth = NewSU->Depth = SU->Depth;
LoadSU->Height = NewSU->Height = SU->Height;
ComputeLatency(LoadSU);
ComputeLatency(NewSU);
SUnit *ChainPred = NULL;
SmallVector<SDep, 4> ChainSuccs;
SmallVector<SDep, 4> LoadPreds;
SmallVector<SDep, 4> NodePreds;
SmallVector<SDep, 4> NodeSuccs;
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
I != E; ++I) {
if (I->isCtrl)
ChainPred = I->Dep;
else if (I->Dep->Node && I->Dep->Node->isOperand(LoadNode))
LoadPreds.push_back(SDep(I->Dep, I->Reg, I->Cost, false, false));
else
NodePreds.push_back(SDep(I->Dep, I->Reg, I->Cost, false, false));
}
for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
if (I->isCtrl)
ChainSuccs.push_back(SDep(I->Dep, I->Reg, I->Cost,
I->isCtrl, I->isSpecial));
else
NodeSuccs.push_back(SDep(I->Dep, I->Reg, I->Cost,
I->isCtrl, I->isSpecial));
}
SU->removePred(ChainPred, true, false);
LoadSU->addPred(ChainPred, true, false);
for (unsigned i = 0, e = LoadPreds.size(); i != e; ++i) {
SDep *Pred = &LoadPreds[i];
SU->removePred(Pred->Dep, Pred->isCtrl, Pred->isSpecial);
LoadSU->addPred(Pred->Dep, Pred->isCtrl, Pred->isSpecial,
Pred->Reg, Pred->Cost);
}
for (unsigned i = 0, e = NodePreds.size(); i != e; ++i) {
SDep *Pred = &NodePreds[i];
SU->removePred(Pred->Dep, Pred->isCtrl, Pred->isSpecial);
NewSU->addPred(Pred->Dep, Pred->isCtrl, Pred->isSpecial,
Pred->Reg, Pred->Cost);
}
for (unsigned i = 0, e = NodeSuccs.size(); i != e; ++i) {
SDep *Succ = &NodeSuccs[i];
Succ->Dep->removePred(SU, Succ->isCtrl, Succ->isSpecial);
Succ->Dep->addPred(NewSU, Succ->isCtrl, Succ->isSpecial,
Succ->Reg, Succ->Cost);
}
for (unsigned i = 0, e = ChainSuccs.size(); i != e; ++i) {
SDep *Succ = &ChainSuccs[i];
Succ->Dep->removePred(SU, Succ->isCtrl, Succ->isSpecial);
Succ->Dep->addPred(LoadSU, Succ->isCtrl, Succ->isSpecial,
Succ->Reg, Succ->Cost);
}
NewSU->addPred(LoadSU, false, false);
AvailableQueue->addNode(LoadSU);
AvailableQueue->addNode(NewSU);
++NumUnfolds;
if (NewSU->NumSuccsLeft == 0) {
NewSU->isAvailable = true;
return NewSU;
} else
SU = NewSU;
}
DOUT << "Duplicating SU # " << SU->NodeNum << "\n";
NewSU = Clone(SU);
// New SUnit has the exact same predecessors.
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
@@ -452,6 +566,7 @@ void ScheduleDAGRRList::InsertCCCopiesAndMoveSuccs(SUnit *SU, unsigned Reg,
const TargetRegisterClass *DestRC,
const TargetRegisterClass *SrcRC,
SmallVector<SUnit*, 2> &Copies) {
abort();
SUnit *CopyFromSU = NewSUnit(NULL);
CopyFromSU->CopySrcRC = SrcRC;
CopyFromSU->CopyDstRC = DestRC;
@@ -640,10 +755,8 @@ void ScheduleDAGRRList::ListScheduleBottomUp() {
assert(LRegs.size() == 1 && "Can't handle this yet!");
unsigned Reg = LRegs[0];
SUnit *LRDef = LiveRegDefs[Reg];
SUnit *NewDef;
if (isSafeToCopy(LRDef->Node))
NewDef = CopyAndMoveSuccessors(LRDef);
else {
SUnit *NewDef = CopyAndMoveSuccessors(LRDef);
if (!NewDef) {
// Issue expensive cross register class copies.
MVT::ValueType VT = getPhysicalRegisterVT(LRDef->Node, Reg, TII);
const TargetRegisterClass *RC =