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llvm-6502/lib/CodeGen/SelectionDAG/ScheduleDAGList.cpp
Chris Lattner fc3549ee8c Don't advance the hazard recognizer when there are no hazards and no instructions 
to be emitted.

Don't add one to the latency of a completed instruction if the latency of the
op is 0.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@26718 91177308-0d34-0410-b5e6-96231b3b80d8
2006-03-12 09:01:41 +00:00

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//===---- ScheduleDAGList.cpp - Implement a list scheduler for isel DAG ---===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Evan Cheng and is distributed under the
// University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements bottom-up and top-down list schedulers, using standard
// algorithms. The basic approach uses a priority queue of available nodes to
// schedule. One at a time, nodes are taken from the priority queue (thus in
// priority order), checked for legality to schedule, and emitted if legal.
//
// Nodes may not be legal to schedule either due to structural hazards (e.g.
// pipeline or resource constraints) or because an input to the instruction has
// not completed execution.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sched"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/ADT/Statistic.h"
#include <climits>
#include <iostream>
#include <queue>
#include <set>
#include <vector>
#include "llvm/Support/CommandLine.h"
using namespace llvm;
namespace {
Statistic<> NumNoops ("scheduler", "Number of noops inserted");
Statistic<> NumStalls("scheduler", "Number of pipeline stalls");
/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
/// a group of nodes flagged together.
struct SUnit {
SDNode *Node; // Representative node.
std::vector<SDNode*> FlaggedNodes; // All nodes flagged to Node.
// Preds/Succs - The SUnits before/after us in the graph. The boolean value
// is true if the edge is a token chain edge, false if it is a value edge.
std::set<std::pair<SUnit*,bool> > Preds; // All sunit predecessors.
std::set<std::pair<SUnit*,bool> > Succs; // All sunit successors.
short NumPredsLeft; // # of preds not scheduled.
short NumSuccsLeft; // # of succs not scheduled.
short NumChainPredsLeft; // # of chain preds not scheduled.
short NumChainSuccsLeft; // # of chain succs not scheduled.
bool isTwoAddress : 1; // Is a two-address instruction.
bool isDefNUseOperand : 1; // Is a def&use operand.
bool isPending : 1; // True once pending.
bool isAvailable : 1; // True once available.
bool isScheduled : 1; // True once scheduled.
unsigned short Latency; // Node latency.
unsigned CycleBound; // Upper/lower cycle to be scheduled at.
unsigned Cycle; // Once scheduled, the cycle of the op.
unsigned NodeNum; // Entry # of node in the node vector.
SUnit(SDNode *node, unsigned nodenum)
: Node(node), NumPredsLeft(0), NumSuccsLeft(0),
NumChainPredsLeft(0), NumChainSuccsLeft(0),
isTwoAddress(false), isDefNUseOperand(false),
isPending(false), isAvailable(false), isScheduled(false),
Latency(0), CycleBound(0), Cycle(0), NodeNum(nodenum) {}
void dump(const SelectionDAG *G) const;
void dumpAll(const SelectionDAG *G) const;
};
}
void SUnit::dump(const SelectionDAG *G) const {
std::cerr << "SU: ";
Node->dump(G);
std::cerr << "\n";
if (FlaggedNodes.size() != 0) {
for (unsigned i = 0, e = FlaggedNodes.size(); i != e; i++) {
std::cerr << " ";
FlaggedNodes[i]->dump(G);
std::cerr << "\n";
}
}
}
void SUnit::dumpAll(const SelectionDAG *G) const {
dump(G);
std::cerr << " # preds left : " << NumPredsLeft << "\n";
std::cerr << " # succs left : " << NumSuccsLeft << "\n";
std::cerr << " # chain preds left : " << NumChainPredsLeft << "\n";
std::cerr << " # chain succs left : " << NumChainSuccsLeft << "\n";
std::cerr << " Latency : " << Latency << "\n";
if (Preds.size() != 0) {
std::cerr << " Predecessors:\n";
for (std::set<std::pair<SUnit*,bool> >::const_iterator I = Preds.begin(),
E = Preds.end(); I != E; ++I) {
if (I->second)
std::cerr << " ch ";
else
std::cerr << " val ";
I->first->dump(G);
}
}
if (Succs.size() != 0) {
std::cerr << " Successors:\n";
for (std::set<std::pair<SUnit*, bool> >::const_iterator I = Succs.begin(),
E = Succs.end(); I != E; ++I) {
if (I->second)
std::cerr << " ch ";
else
std::cerr << " val ";
I->first->dump(G);
}
}
std::cerr << "\n";
}
//===----------------------------------------------------------------------===//
/// SchedulingPriorityQueue - This interface is used to plug different
/// priorities computation algorithms into the list scheduler. It implements the
/// interface of a standard priority queue, where nodes are inserted in
/// arbitrary order and returned in priority order. The computation of the
/// priority and the representation of the queue are totally up to the
/// implementation to decide.
///
namespace {
class SchedulingPriorityQueue {
public:
virtual ~SchedulingPriorityQueue() {}
virtual void initNodes(const std::vector<SUnit> &SUnits) = 0;
virtual void releaseState() = 0;
virtual bool empty() const = 0;
virtual void push(SUnit *U) = 0;
virtual void push_all(const std::vector<SUnit *> &Nodes) = 0;
virtual SUnit *pop() = 0;
/// ScheduledNode - As each node is scheduled, this method is invoked. This
/// allows the priority function to adjust the priority of node that have
/// already been emitted.
virtual void ScheduledNode(SUnit *Node) {}
};
}
namespace {
//===----------------------------------------------------------------------===//
/// ScheduleDAGList - The actual list scheduler implementation. This supports
/// both top-down and bottom-up scheduling.
///
class ScheduleDAGList : public ScheduleDAG {
private:
// SDNode to SUnit mapping (many to one).
std::map<SDNode*, SUnit*> SUnitMap;
// The schedule. Null SUnit*'s represent noop instructions.
std::vector<SUnit*> Sequence;
// The scheduling units.
std::vector<SUnit> SUnits;
/// isBottomUp - This is true if the scheduling problem is bottom-up, false if
/// it is top-down.
bool isBottomUp;
/// AvailableQueue - The priority queue to use for the available SUnits.
///
SchedulingPriorityQueue *AvailableQueue;
/// PendingQueue - This contains all of the instructions whose operands have
/// been issued, but their results are not ready yet (due to the latency of
/// the operation). Once the operands becomes available, the instruction is
/// added to the AvailableQueue. This keeps track of each SUnit and the
/// number of cycles left to execute before the operation is available.
std::vector<std::pair<unsigned, SUnit*> > PendingQueue;
/// HazardRec - The hazard recognizer to use.
HazardRecognizer *HazardRec;
public:
ScheduleDAGList(SelectionDAG &dag, MachineBasicBlock *bb,
const TargetMachine &tm, bool isbottomup,
SchedulingPriorityQueue *availqueue,
HazardRecognizer *HR)
: ScheduleDAG(dag, bb, tm), isBottomUp(isbottomup),
AvailableQueue(availqueue), HazardRec(HR) {
}
~ScheduleDAGList() {
delete HazardRec;
delete AvailableQueue;
}
void Schedule();
void dumpSchedule() const;
private:
SUnit *NewSUnit(SDNode *N);
void ReleasePred(SUnit *PredSU, bool isChain, unsigned CurCycle);
void ReleaseSucc(SUnit *SuccSU, bool isChain);
void ScheduleNodeBottomUp(SUnit *SU, unsigned CurCycle);
void ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle);
void ListScheduleTopDown();
void ListScheduleBottomUp();
void BuildSchedUnits();
void EmitSchedule();
};
} // end anonymous namespace
HazardRecognizer::~HazardRecognizer() {}
/// NewSUnit - Creates a new SUnit and return a ptr to it.
SUnit *ScheduleDAGList::NewSUnit(SDNode *N) {
SUnits.push_back(SUnit(N, SUnits.size()));
return &SUnits.back();
}
/// 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.
void ScheduleDAGList::BuildSchedUnits() {
// Reserve entries in the vector for each of the SUnits we are creating. This
// ensure that reallocation of the vector won't happen, so SUnit*'s won't get
// 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.
continue;
// If this node has already been processed, stop now.
if (SUnitMap[NI]) continue;
SUnit *NodeSUnit = NewSUnit(NI);
// See if anything is flagged to this node, if so, add them to flagged
// nodes. Nodes can have at most one flag input and one flag output. Flags
// are required the be the last operand and result of a node.
// Scan up, adding flagged preds to FlaggedNodes.
SDNode *N = NI;
while (N->getNumOperands() &&
N->getOperand(N->getNumOperands()-1).getValueType() == MVT::Flag) {
N = N->getOperand(N->getNumOperands()-1).Val;
NodeSUnit->FlaggedNodes.push_back(N);
SUnitMap[N] = NodeSUnit;
}
// Scan down, adding this node and any flagged succs to FlaggedNodes if they
// have a user of the flag operand.
N = NI;
while (N->getValueType(N->getNumValues()-1) == MVT::Flag) {
SDOperand FlagVal(N, N->getNumValues()-1);
// There are either zero or one users of the Flag result.
bool HasFlagUse = false;
for (SDNode::use_iterator UI = N->use_begin(), E = N->use_end();
UI != E; ++UI)
if (FlagVal.isOperand(*UI)) {
HasFlagUse = true;
NodeSUnit->FlaggedNodes.push_back(N);
SUnitMap[N] = NodeSUnit;
N = *UI;
break;
}
if (!HasFlagUse) break;
}
// Now all flagged nodes are in FlaggedNodes and N is the bottom-most node.
// Update the SUnit
NodeSUnit->Node = N;
SUnitMap[N] = 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;
}
}
}
}
// Pass 2: add the preds, succs, etc.
for (unsigned su = 0, e = SUnits.size(); su != e; ++su) {
SUnit *SU = &SUnits[su];
SDNode *MainNode = SU->Node;
if (MainNode->isTargetOpcode() &&
TII->isTwoAddrInstr(MainNode->getTargetOpcode()))
SU->isTwoAddress = true;
// Find all predecessors and successors of the group.
// Temporarily add N to make code simpler.
SU->FlaggedNodes.push_back(MainNode);
for (unsigned n = 0, e = SU->FlaggedNodes.size(); n != e; ++n) {
SDNode *N = SU->FlaggedNodes[n];
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) {
SDNode *OpN = N->getOperand(i).Val;
if (isPassiveNode(OpN)) continue; // Not scheduled.
SUnit *OpSU = SUnitMap[OpN];
assert(OpSU && "Node has no SUnit!");
if (OpSU == SU) continue; // In the same group.
MVT::ValueType OpVT = N->getOperand(i).getValueType();
assert(OpVT != MVT::Flag && "Flagged nodes should be in same sunit!");
bool isChain = OpVT == MVT::Other;
if (SU->Preds.insert(std::make_pair(OpSU, isChain)).second) {
if (!isChain) {
SU->NumPredsLeft++;
} else {
SU->NumChainPredsLeft++;
}
}
if (OpSU->Succs.insert(std::make_pair(SU, isChain)).second) {
if (!isChain) {
OpSU->NumSuccsLeft++;
} else {
OpSU->NumChainSuccsLeft++;
}
}
}
}
// Remove MainNode from FlaggedNodes again.
SU->FlaggedNodes.pop_back();
}
return;
DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
SUnits[su].dumpAll(&DAG));
}
/// EmitSchedule - Emit the machine code in scheduled order.
void ScheduleDAGList::EmitSchedule() {
std::map<SDNode*, unsigned> VRBaseMap;
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
if (SUnit *SU = Sequence[i]) {
for (unsigned j = 0, ee = SU->FlaggedNodes.size(); j != ee; j++)
EmitNode(SU->FlaggedNodes[j], VRBaseMap);
EmitNode(SU->Node, VRBaseMap);
} else {
// Null SUnit* is a noop.
EmitNoop();
}
}
}
/// dump - dump the schedule.
void ScheduleDAGList::dumpSchedule() const {
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
if (SUnit *SU = Sequence[i])
SU->dump(&DAG);
else
std::cerr << "**** NOOP ****\n";
}
}
/// Schedule - Schedule the DAG using list scheduling.
void ScheduleDAGList::Schedule() {
DEBUG(std::cerr << "********** List Scheduling **********\n");
// Build scheduling units.
BuildSchedUnits();
AvailableQueue->initNodes(SUnits);
// Execute the actual scheduling loop Top-Down or Bottom-Up as appropriate.
if (isBottomUp)
ListScheduleBottomUp();
else
ListScheduleTopDown();
AvailableQueue->releaseState();
DEBUG(std::cerr << "*** Final schedule ***\n");
DEBUG(dumpSchedule());
DEBUG(std::cerr << "\n");
// Emit in scheduled order
EmitSchedule();
}
//===----------------------------------------------------------------------===//
// Bottom-Up Scheduling
//===----------------------------------------------------------------------===//
/// ReleasePred - Decrement the NumSuccsLeft count of a predecessor. Add it to
/// the Available queue is the count reaches zero. Also update its cycle bound.
void ScheduleDAGList::ReleasePred(SUnit *PredSU, bool isChain,
unsigned CurCycle) {
// FIXME: the distance between two nodes is not always == the predecessor's
// latency. For example, the reader can very well read the register written
// by the predecessor later than the issue cycle. It also depends on the
// interrupt model (drain vs. freeze).
PredSU->CycleBound = std::max(PredSU->CycleBound, CurCycle + PredSU->Latency);
if (!isChain)
PredSU->NumSuccsLeft--;
else
PredSU->NumChainSuccsLeft--;
#ifndef NDEBUG
if (PredSU->NumSuccsLeft < 0 || PredSU->NumChainSuccsLeft < 0) {
std::cerr << "*** List scheduling failed! ***\n";
PredSU->dump(&DAG);
std::cerr << " has been released too many times!\n";
assert(0);
}
#endif
if ((PredSU->NumSuccsLeft + PredSU->NumChainSuccsLeft) == 0) {
// EntryToken has to go last! Special case it here.
if (PredSU->Node->getOpcode() != ISD::EntryToken) {
PredSU->isAvailable = true;
AvailableQueue->push(PredSU);
}
}
}
/// ScheduleNodeBottomUp - Add the node to the schedule. Decrement the pending
/// count of its predecessors. If a predecessor pending count is zero, add it to
/// the Available queue.
void ScheduleDAGList::ScheduleNodeBottomUp(SUnit *SU, unsigned CurCycle) {
DEBUG(std::cerr << "*** Scheduling [" << CurCycle << "]: ");
DEBUG(SU->dump(&DAG));
SU->Cycle = CurCycle;
Sequence.push_back(SU);
// Bottom up: release predecessors
for (std::set<std::pair<SUnit*, bool> >::iterator I = SU->Preds.begin(),
E = SU->Preds.end(); I != E; ++I) {
ReleasePred(I->first, I->second, CurCycle);
// FIXME: This is something used by the priority function that it should
// calculate directly.
if (!I->second)
SU->NumPredsLeft--;
}
}
/// isReady - True if node's lower cycle bound is less or equal to the current
/// scheduling cycle. Always true if all nodes have uniform latency 1.
static inline bool isReady(SUnit *SU, unsigned CurrCycle) {
return SU->CycleBound <= CurrCycle;
}
/// ListScheduleBottomUp - The main loop of list scheduling for bottom-up
/// schedulers.
void ScheduleDAGList::ListScheduleBottomUp() {
unsigned CurrCycle = 0;
// Add root to Available queue.
AvailableQueue->push(SUnitMap[DAG.getRoot().Val]);
// While Available queue is not empty, grab the node with the highest
// priority. If it is not ready put it back. Schedule the node.
std::vector<SUnit*> NotReady;
while (!AvailableQueue->empty()) {
SUnit *CurrNode = AvailableQueue->pop();
while (!isReady(CurrNode, CurrCycle)) {
NotReady.push_back(CurrNode);
CurrNode = AvailableQueue->pop();
}
// Add the nodes that aren't ready back onto the available list.
AvailableQueue->push_all(NotReady);
NotReady.clear();
ScheduleNodeBottomUp(CurrNode, CurrCycle);
CurrCycle++;
CurrNode->isScheduled = true;
AvailableQueue->ScheduledNode(CurrNode);
}
// Add entry node last
if (DAG.getEntryNode().Val != DAG.getRoot().Val) {
SUnit *Entry = SUnitMap[DAG.getEntryNode().Val];
Sequence.push_back(Entry);
}
// Reverse the order if it is bottom up.
std::reverse(Sequence.begin(), Sequence.end());
#ifndef NDEBUG
// Verify that all SUnits were scheduled.
bool AnyNotSched = false;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
if (SUnits[i].NumSuccsLeft != 0 || SUnits[i].NumChainSuccsLeft != 0) {
if (!AnyNotSched)
std::cerr << "*** List scheduling failed! ***\n";
SUnits[i].dump(&DAG);
std::cerr << "has not been scheduled!\n";
AnyNotSched = true;
}
}
assert(!AnyNotSched);
#endif
}
//===----------------------------------------------------------------------===//
// Top-Down Scheduling
//===----------------------------------------------------------------------===//
/// ReleaseSucc - Decrement the NumPredsLeft count of a successor. Add it to
/// the PendingQueue if the count reaches zero.
void ScheduleDAGList::ReleaseSucc(SUnit *SuccSU, bool isChain) {
if (!isChain)
SuccSU->NumPredsLeft--;
else
SuccSU->NumChainPredsLeft--;
assert(SuccSU->NumPredsLeft >= 0 && SuccSU->NumChainPredsLeft >= 0 &&
"List scheduling internal error");
if ((SuccSU->NumPredsLeft + SuccSU->NumChainPredsLeft) == 0) {
// Compute how many cycles it will be before this actually becomes
// available. This is the max of the start time of all predecessors plus
// their latencies.
unsigned AvailableCycle = 0;
for (std::set<std::pair<SUnit*, bool> >::iterator I = SuccSU->Preds.begin(),
E = SuccSU->Preds.end(); I != E; ++I) {
// If this is a token edge, we don't need to wait for the latency of the
// preceeding instruction (e.g. a long-latency load) unless there is also
// some other data dependence.
unsigned PredDoneCycle = I->first->Cycle;
if (!I->second)
PredDoneCycle += I->first->Latency;
else if (I->first->Latency)
PredDoneCycle += 1;
AvailableCycle = std::max(AvailableCycle, PredDoneCycle);
}
PendingQueue.push_back(std::make_pair(AvailableCycle, SuccSU));
SuccSU->isPending = true;
}
}
/// ScheduleNodeTopDown - Add the node to the schedule. Decrement the pending
/// count of its successors. If a successor pending count is zero, add it to
/// the Available queue.
void ScheduleDAGList::ScheduleNodeTopDown(SUnit *SU, unsigned CurCycle) {
DEBUG(std::cerr << "*** Scheduling [" << CurCycle << "]: ");
DEBUG(SU->dump(&DAG));
Sequence.push_back(SU);
SU->Cycle = CurCycle;
// Bottom up: release successors.
for (std::set<std::pair<SUnit*, bool> >::iterator I = SU->Succs.begin(),
E = SU->Succs.end(); I != E; ++I)
ReleaseSucc(I->first, I->second);
}
/// ListScheduleTopDown - The main loop of list scheduling for top-down
/// schedulers.
void ScheduleDAGList::ListScheduleTopDown() {
unsigned CurCycle = 0;
SUnit *Entry = SUnitMap[DAG.getEntryNode().Val];
// All leaves to Available queue.
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
// It is available if it has no predecessors.
if (SUnits[i].Preds.size() == 0 && &SUnits[i] != Entry) {
AvailableQueue->push(&SUnits[i]);
SUnits[i].isAvailable = SUnits[i].isPending = true;
}
}
// Emit the entry node first.
ScheduleNodeTopDown(Entry, CurCycle);
HazardRec->EmitInstruction(Entry->Node);
// While Available queue is not empty, grab the node with the highest
// priority. If it is not ready put it back. Schedule the node.
std::vector<SUnit*> NotReady;
while (!AvailableQueue->empty() || !PendingQueue.empty()) {
// Check to see if any of the pending instructions are ready to issue. If
// so, add them to the available queue.
for (unsigned i = 0, e = PendingQueue.size(); i != e; ++i) {
if (PendingQueue[i].first == CurCycle) {
AvailableQueue->push(PendingQueue[i].second);
PendingQueue[i].second->isAvailable = true;
PendingQueue[i] = PendingQueue.back();
PendingQueue.pop_back();
--i; --e;
} else {
assert(PendingQueue[i].first > CurCycle && "Negative latency?");
}
}
// If there are no instructions available, don't try to issue anything, and
// don't advance the hazard recognizer.
if (AvailableQueue->empty()) {
++CurCycle;
continue;
}
SUnit *FoundSUnit = 0;
SDNode *FoundNode = 0;
bool HasNoopHazards = false;
while (!AvailableQueue->empty()) {
SUnit *CurSUnit = AvailableQueue->pop();
// Get the node represented by this SUnit.
FoundNode = CurSUnit->Node;
// If this is a pseudo op, like copyfromreg, look to see if there is a
// real target node flagged to it. If so, use the target node.
for (unsigned i = 0, e = CurSUnit->FlaggedNodes.size();
FoundNode->getOpcode() < ISD::BUILTIN_OP_END && i != e; ++i)
FoundNode = CurSUnit->FlaggedNodes[i];
HazardRecognizer::HazardType HT = HazardRec->getHazardType(FoundNode);
if (HT == HazardRecognizer::NoHazard) {
FoundSUnit = CurSUnit;
break;
}
// Remember if this is a noop hazard.
HasNoopHazards |= HT == HazardRecognizer::NoopHazard;
NotReady.push_back(CurSUnit);
}
// Add the nodes that aren't ready back onto the available list.
if (!NotReady.empty()) {
AvailableQueue->push_all(NotReady);
NotReady.clear();
}
// If we found a node to schedule, do it now.
if (FoundSUnit) {
ScheduleNodeTopDown(FoundSUnit, CurCycle);
HazardRec->EmitInstruction(FoundNode);
FoundSUnit->isScheduled = true;
AvailableQueue->ScheduledNode(FoundSUnit);
// If this is a pseudo-op node, we don't want to increment the current
// cycle.
if (FoundSUnit->Latency) // Don't increment CurCycle for pseudo-ops!
++CurCycle;
} else if (!HasNoopHazards) {
// Otherwise, we have a pipeline stall, but no other problem, just advance
// the current cycle and try again.
DEBUG(std::cerr << "*** Advancing cycle, no work to do\n");
HazardRec->AdvanceCycle();
++NumStalls;
++CurCycle;
} else {
// Otherwise, we have no instructions to issue and we have instructions
// that will fault if we don't do this right. This is the case for
// processors without pipeline interlocks and other cases.
DEBUG(std::cerr << "*** Emitting noop\n");
HazardRec->EmitNoop();
Sequence.push_back(0); // NULL SUnit* -> noop
++NumNoops;
++CurCycle;
}
}
#ifndef NDEBUG
// Verify that all SUnits were scheduled.
bool AnyNotSched = false;
for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
if (SUnits[i].NumPredsLeft != 0 || SUnits[i].NumChainPredsLeft != 0) {
if (!AnyNotSched)
std::cerr << "*** List scheduling failed! ***\n";
SUnits[i].dump(&DAG);
std::cerr << "has not been scheduled!\n";
AnyNotSched = true;
}
}
assert(!AnyNotSched);
#endif
}
//===----------------------------------------------------------------------===//
// RegReductionPriorityQueue Implementation
//===----------------------------------------------------------------------===//
//
// This is a SchedulingPriorityQueue that schedules using Sethi Ullman numbers
// to reduce register pressure.
//
namespace {
class RegReductionPriorityQueue;
/// Sorting functions for the Available queue.
struct ls_rr_sort : public std::binary_function<SUnit*, SUnit*, bool> {
RegReductionPriorityQueue *SPQ;
ls_rr_sort(RegReductionPriorityQueue *spq) : SPQ(spq) {}
ls_rr_sort(const ls_rr_sort &RHS) : SPQ(RHS.SPQ) {}
bool operator()(const SUnit* left, const SUnit* right) const;
};
} // end anonymous namespace
namespace {
class RegReductionPriorityQueue : public SchedulingPriorityQueue {
// SUnits - The SUnits for the current graph.
const std::vector<SUnit> *SUnits;
// SethiUllmanNumbers - The SethiUllman number for each node.
std::vector<int> SethiUllmanNumbers;
std::priority_queue<SUnit*, std::vector<SUnit*>, ls_rr_sort> Queue;
public:
RegReductionPriorityQueue() : Queue(ls_rr_sort(this)) {
}
void initNodes(const std::vector<SUnit> &sunits) {
SUnits = &sunits;
// Calculate node priorities.
CalculatePriorities();
}
void releaseState() {
SUnits = 0;
SethiUllmanNumbers.clear();
}
unsigned getSethiUllmanNumber(unsigned NodeNum) const {
assert(NodeNum < SethiUllmanNumbers.size());
return SethiUllmanNumbers[NodeNum];
}
bool empty() const { return Queue.empty(); }
void push(SUnit *U) {
Queue.push(U);
}
void push_all(const std::vector<SUnit *> &Nodes) {
for (unsigned i = 0, e = Nodes.size(); i != e; ++i)
Queue.push(Nodes[i]);
}
SUnit *pop() {
SUnit *V = Queue.top();
Queue.pop();
return V;
}
private:
void CalculatePriorities();
int CalcNodePriority(const SUnit *SU);
};
}
bool ls_rr_sort::operator()(const SUnit *left, const SUnit *right) const {
unsigned LeftNum = left->NodeNum;
unsigned RightNum = right->NodeNum;
int LBonus = (int)left ->isDefNUseOperand;
int RBonus = (int)right->isDefNUseOperand;
// Special tie breaker: if two nodes share a operand, the one that
// use it as a def&use operand is preferred.
if (left->isTwoAddress && !right->isTwoAddress) {
SDNode *DUNode = left->Node->getOperand(0).Val;
if (DUNode->isOperand(right->Node))
LBonus++;
}
if (!left->isTwoAddress && right->isTwoAddress) {
SDNode *DUNode = right->Node->getOperand(0).Val;
if (DUNode->isOperand(left->Node))
RBonus++;
}
// Priority1 is just the number of live range genned.
int LPriority1 = left ->NumPredsLeft - LBonus;
int RPriority1 = right->NumPredsLeft - RBonus;
int LPriority2 = SPQ->getSethiUllmanNumber(LeftNum) + LBonus;
int RPriority2 = SPQ->getSethiUllmanNumber(RightNum) + RBonus;
if (LPriority1 > RPriority1)
return true;
else if (LPriority1 == RPriority1)
if (LPriority2 < RPriority2)
return true;
else if (LPriority2 == RPriority2)
if (left->CycleBound > right->CycleBound)
return true;
return false;
}
/// CalcNodePriority - Priority is the Sethi Ullman number.
/// Smaller number is the higher priority.
int RegReductionPriorityQueue::CalcNodePriority(const SUnit *SU) {
int &SethiUllmanNumber = SethiUllmanNumbers[SU->NodeNum];
if (SethiUllmanNumber != INT_MIN)
return SethiUllmanNumber;
if (SU->Preds.size() == 0) {
SethiUllmanNumber = 1;
} else {
int Extra = 0;
for (std::set<std::pair<SUnit*, bool> >::const_iterator
I = SU->Preds.begin(), E = SU->Preds.end(); I != E; ++I) {
if (I->second) continue; // ignore chain preds.
SUnit *PredSU = I->first;
int PredSethiUllman = CalcNodePriority(PredSU);
if (PredSethiUllman > SethiUllmanNumber) {
SethiUllmanNumber = PredSethiUllman;
Extra = 0;
} else if (PredSethiUllman == SethiUllmanNumber)
Extra++;
}
if (SU->Node->getOpcode() != ISD::TokenFactor)
SethiUllmanNumber += Extra;
else
SethiUllmanNumber = (Extra == 1) ? 0 : Extra-1;
}
return SethiUllmanNumber;
}
/// CalculatePriorities - Calculate priorities of all scheduling units.
void RegReductionPriorityQueue::CalculatePriorities() {
SethiUllmanNumbers.assign(SUnits->size(), INT_MIN);
for (unsigned i = 0, e = SUnits->size(); i != e; ++i)
CalcNodePriority(&(*SUnits)[i]);
}
//===----------------------------------------------------------------------===//
// LatencyPriorityQueue Implementation
//===----------------------------------------------------------------------===//
//
// This is a SchedulingPriorityQueue that schedules using latency information to
// reduce the length of the critical path through the basic block.
//
namespace {
class LatencyPriorityQueue;
/// Sorting functions for the Available queue.
struct latency_sort : public std::binary_function<SUnit*, SUnit*, bool> {
LatencyPriorityQueue *PQ;
latency_sort(LatencyPriorityQueue *pq) : PQ(pq) {}
latency_sort(const latency_sort &RHS) : PQ(RHS.PQ) {}
bool operator()(const SUnit* left, const SUnit* right) const;
};
} // end anonymous namespace
namespace {
class LatencyPriorityQueue : public SchedulingPriorityQueue {
// SUnits - The SUnits for the current graph.
const std::vector<SUnit> *SUnits;
// Latencies - The latency (max of latency from this node to the bb exit)
// for each node.
std::vector<int> Latencies;
/// NumNodesSolelyBlocking - This vector contains, for every node in the
/// Queue, the number of nodes that the node is the sole unscheduled
/// predecessor for. This is used as a tie-breaker heuristic for better
/// mobility.
std::vector<unsigned> NumNodesSolelyBlocking;
std::priority_queue<SUnit*, std::vector<SUnit*>, latency_sort> Queue;
public:
LatencyPriorityQueue() : Queue(latency_sort(this)) {
}
void initNodes(const std::vector<SUnit> &sunits) {
SUnits = &sunits;
// Calculate node priorities.
CalculatePriorities();
}
void releaseState() {
SUnits = 0;
Latencies.clear();
}
unsigned getLatency(unsigned NodeNum) const {
assert(NodeNum < Latencies.size());
return Latencies[NodeNum];
}
unsigned getNumSolelyBlockNodes(unsigned NodeNum) const {
assert(NodeNum < NumNodesSolelyBlocking.size());
return NumNodesSolelyBlocking[NodeNum];
}
bool empty() const { return Queue.empty(); }
virtual void push(SUnit *U) {
push_impl(U);
}
void push_impl(SUnit *U);
void push_all(const std::vector<SUnit *> &Nodes) {
for (unsigned i = 0, e = Nodes.size(); i != e; ++i)
push_impl(Nodes[i]);
}
SUnit *pop() {
SUnit *V = Queue.top();
Queue.pop();
return V;
}
// ScheduledNode - As nodes are scheduled, we look to see if there are any
// successor nodes that have a single unscheduled predecessor. If so, that
// single predecessor has a higher priority, since scheduling it will make
// the node available.
void ScheduledNode(SUnit *Node);
private:
void CalculatePriorities();
int CalcLatency(const SUnit &SU);
void AdjustPriorityOfUnscheduledPreds(SUnit *SU);
/// RemoveFromPriorityQueue - This is a really inefficient way to remove a
/// node from a priority queue. We should roll our own heap to make this
/// better or something.
void RemoveFromPriorityQueue(SUnit *SU) {
std::vector<SUnit*> Temp;
assert(!Queue.empty() && "Not in queue!");
while (Queue.top() != SU) {
Temp.push_back(Queue.top());
Queue.pop();
assert(!Queue.empty() && "Not in queue!");
}
// Remove the node from the PQ.
Queue.pop();
// Add all the other nodes back.
for (unsigned i = 0, e = Temp.size(); i != e; ++i)
Queue.push(Temp[i]);
}
};
}
bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
unsigned LHSNum = LHS->NodeNum;
unsigned RHSNum = RHS->NodeNum;
// The most important heuristic is scheduling the critical path.
unsigned LHSLatency = PQ->getLatency(LHSNum);
unsigned RHSLatency = PQ->getLatency(RHSNum);
if (LHSLatency < RHSLatency) return true;
if (LHSLatency > RHSLatency) return false;
// After that, if two nodes have identical latencies, look to see if one will
// unblock more other nodes than the other.
unsigned LHSBlocked = PQ->getNumSolelyBlockNodes(LHSNum);
unsigned RHSBlocked = PQ->getNumSolelyBlockNodes(RHSNum);
if (LHSBlocked < RHSBlocked) return true;
if (LHSBlocked > RHSBlocked) return false;
// Finally, just to provide a stable ordering, use the node number as a
// deciding factor.
return LHSNum < RHSNum;
}
/// CalcNodePriority - Calculate the maximal path from the node to the exit.
///
int LatencyPriorityQueue::CalcLatency(const SUnit &SU) {
int &Latency = Latencies[SU.NodeNum];
if (Latency != -1)
return Latency;
int MaxSuccLatency = 0;
for (std::set<std::pair<SUnit*, bool> >::const_iterator I = SU.Succs.begin(),
E = SU.Succs.end(); I != E; ++I)
MaxSuccLatency = std::max(MaxSuccLatency, CalcLatency(*I->first));
return Latency = MaxSuccLatency + SU.Latency;
}
/// CalculatePriorities - Calculate priorities of all scheduling units.
void LatencyPriorityQueue::CalculatePriorities() {
Latencies.assign(SUnits->size(), -1);
NumNodesSolelyBlocking.assign(SUnits->size(), 0);
for (unsigned i = 0, e = SUnits->size(); i != e; ++i)
CalcLatency((*SUnits)[i]);
}
/// getSingleUnscheduledPred - If there is exactly one unscheduled predecessor
/// of SU, return it, otherwise return null.
static SUnit *getSingleUnscheduledPred(SUnit *SU) {
SUnit *OnlyAvailablePred = 0;
for (std::set<std::pair<SUnit*, bool> >::const_iterator I = SU->Preds.begin(),
E = SU->Preds.end(); I != E; ++I)
if (!I->first->isScheduled) {
// We found an available, but not scheduled, predecessor. If it's the
// only one we have found, keep track of it... otherwise give up.
if (OnlyAvailablePred && OnlyAvailablePred != I->first)
return 0;
OnlyAvailablePred = I->first;
}
return OnlyAvailablePred;
}
void LatencyPriorityQueue::push_impl(SUnit *SU) {
// Look at all of the successors of this node. Count the number of nodes that
// this node is the sole unscheduled node for.
unsigned NumNodesBlocking = 0;
for (std::set<std::pair<SUnit*, bool> >::const_iterator I = SU->Succs.begin(),
E = SU->Succs.end(); I != E; ++I)
if (getSingleUnscheduledPred(I->first) == SU)
++NumNodesBlocking;
NumNodesSolelyBlocking[SU->NodeNum] = NumNodesBlocking;
Queue.push(SU);
}
// ScheduledNode - As nodes are scheduled, we look to see if there are any
// successor nodes that have a single unscheduled predecessor. If so, that
// single predecessor has a higher priority, since scheduling it will make
// the node available.
void LatencyPriorityQueue::ScheduledNode(SUnit *SU) {
for (std::set<std::pair<SUnit*, bool> >::const_iterator I = SU->Succs.begin(),
E = SU->Succs.end(); I != E; ++I)
AdjustPriorityOfUnscheduledPreds(I->first);
}
/// AdjustPriorityOfUnscheduledPreds - One of the predecessors of SU was just
/// scheduled. If SU is not itself available, then there is at least one
/// predecessor node that has not been scheduled yet. If SU has exactly ONE
/// unscheduled predecessor, we want to increase its priority: it getting
/// scheduled will make this node available, so it is better than some other
/// node of the same priority that will not make a node available.
void LatencyPriorityQueue::AdjustPriorityOfUnscheduledPreds(SUnit *SU) {
if (SU->isPending) return; // All preds scheduled.
SUnit *OnlyAvailablePred = getSingleUnscheduledPred(SU);
if (OnlyAvailablePred == 0 || !OnlyAvailablePred->isAvailable) return;
// Okay, we found a single predecessor that is available, but not scheduled.
// Since it is available, it must be in the priority queue. First remove it.
RemoveFromPriorityQueue(OnlyAvailablePred);
// Reinsert the node into the priority queue, which recomputes its
// NumNodesSolelyBlocking value.
push(OnlyAvailablePred);
}
//===----------------------------------------------------------------------===//
// Public Constructor Functions
//===----------------------------------------------------------------------===//
llvm::ScheduleDAG* llvm::createBURRListDAGScheduler(SelectionDAG &DAG,
MachineBasicBlock *BB) {
return new ScheduleDAGList(DAG, BB, DAG.getTarget(), true,
new RegReductionPriorityQueue(),
new HazardRecognizer());
}
/// createTDListDAGScheduler - This creates a top-down list scheduler with the
/// specified hazard recognizer.
ScheduleDAG* llvm::createTDListDAGScheduler(SelectionDAG &DAG,
MachineBasicBlock *BB,
HazardRecognizer *HR) {
return new ScheduleDAGList(DAG, BB, DAG.getTarget(), false,
new LatencyPriorityQueue(),
HR);
}
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