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//===- ScheduleDAGRRList.cpp - Reg pressure reduction list scheduler ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This implements bottom-up and top-down register pressure reduction 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.
//
//===----------------------------------------------------------------------===//
#include "ScheduleDAGSDNodes.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/ISDOpcodes.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/CodeGen/SchedulerRegistry.h"
#include "llvm/CodeGen/SelectionDAGISel.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachineValueType.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <iterator>
#include <limits>
#include <memory>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "pre-RA-sched"
STATISTIC(NumBacktracks, "Number of times scheduler backtracked");
STATISTIC(NumUnfolds, "Number of nodes unfolded");
STATISTIC(NumDups, "Number of duplicated nodes");
STATISTIC(NumPRCopies, "Number of physical register copies");
static RegisterScheduler
burrListDAGScheduler("list-burr",
"Bottom-up register reduction list scheduling",
createBURRListDAGScheduler);
static RegisterScheduler
sourceListDAGScheduler("source",
"Similar to list-burr but schedules in source "
"order when possible",
createSourceListDAGScheduler);
static RegisterScheduler
hybridListDAGScheduler("list-hybrid",
"Bottom-up register pressure aware list scheduling "
"which tries to balance latency and register pressure",
createHybridListDAGScheduler);
static RegisterScheduler
ILPListDAGScheduler("list-ilp",
"Bottom-up register pressure aware list scheduling "
"which tries to balance ILP and register pressure",
createILPListDAGScheduler);
static cl::opt<bool> DisableSchedCycles(
"disable-sched-cycles", cl::Hidden, cl::init(false),
cl::desc("Disable cycle-level precision during preRA scheduling"));
// Temporary sched=list-ilp flags until the heuristics are robust.
// Some options are also available under sched=list-hybrid.
static cl::opt<bool> DisableSchedRegPressure(
"disable-sched-reg-pressure", cl::Hidden, cl::init(false),
cl::desc("Disable regpressure priority in sched=list-ilp"));
static cl::opt<bool> DisableSchedLiveUses(
"disable-sched-live-uses", cl::Hidden, cl::init(true),
cl::desc("Disable live use priority in sched=list-ilp"));
static cl::opt<bool> DisableSchedVRegCycle(
"disable-sched-vrcycle", cl::Hidden, cl::init(false),
cl::desc("Disable virtual register cycle interference checks"));
static cl::opt<bool> DisableSchedPhysRegJoin(
"disable-sched-physreg-join", cl::Hidden, cl::init(false),
cl::desc("Disable physreg def-use affinity"));
static cl::opt<bool> DisableSchedStalls(
"disable-sched-stalls", cl::Hidden, cl::init(true),
cl::desc("Disable no-stall priority in sched=list-ilp"));
static cl::opt<bool> DisableSchedCriticalPath(
"disable-sched-critical-path", cl::Hidden, cl::init(false),
cl::desc("Disable critical path priority in sched=list-ilp"));
static cl::opt<bool> DisableSchedHeight(
"disable-sched-height", cl::Hidden, cl::init(false),
cl::desc("Disable scheduled-height priority in sched=list-ilp"));
static cl::opt<bool> Disable2AddrHack(
"disable-2addr-hack", cl::Hidden, cl::init(true),
cl::desc("Disable scheduler's two-address hack"));
static cl::opt<int> MaxReorderWindow(
"max-sched-reorder", cl::Hidden, cl::init(6),
cl::desc("Number of instructions to allow ahead of the critical path "
"in sched=list-ilp"));
static cl::opt<unsigned> AvgIPC(
"sched-avg-ipc", cl::Hidden, cl::init(1),
cl::desc("Average inst/cycle whan no target itinerary exists."));
namespace {
//===----------------------------------------------------------------------===//
/// ScheduleDAGRRList - The actual register reduction list scheduler
/// implementation. This supports both top-down and bottom-up scheduling.
///
class ScheduleDAGRRList : public ScheduleDAGSDNodes {
private:
/// NeedLatency - True if the scheduler will make use of latency information.
bool NeedLatency;
/// 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.
std::vector<SUnit *> PendingQueue;
/// HazardRec - The hazard recognizer to use.
ScheduleHazardRecognizer *HazardRec;
/// CurCycle - The current scheduler state corresponds to this cycle.
unsigned CurCycle = 0;
/// MinAvailableCycle - Cycle of the soonest available instruction.
unsigned MinAvailableCycle;
/// IssueCount - Count instructions issued in this cycle
/// Currently valid only for bottom-up scheduling.
unsigned IssueCount;
/// LiveRegDefs - A set of physical registers and their definition
/// that are "live". These nodes must be scheduled before any other nodes that
/// modifies the registers can be scheduled.
unsigned NumLiveRegs;
std::unique_ptr<SUnit*[]> LiveRegDefs;
std::unique_ptr<SUnit*[]> LiveRegGens;
// Collect interferences between physical register use/defs.
// Each interference is an SUnit and set of physical registers.
SmallVector<SUnit*, 4> Interferences;
using LRegsMapT = DenseMap<SUnit *, SmallVector<unsigned, 4>>;
LRegsMapT LRegsMap;
/// Topo - A topological ordering for SUnits which permits fast IsReachable
/// and similar queries.
ScheduleDAGTopologicalSort Topo;
// Hack to keep track of the inverse of FindCallSeqStart without more crazy
// DAG crawling.
DenseMap<SUnit*, SUnit*> CallSeqEndForStart;
public:
ScheduleDAGRRList(MachineFunction &mf, bool needlatency,
SchedulingPriorityQueue *availqueue,
CodeGenOpt::Level OptLevel)
: ScheduleDAGSDNodes(mf),
NeedLatency(needlatency), AvailableQueue(availqueue),
Topo(SUnits, nullptr) {
const TargetSubtargetInfo &STI = mf.getSubtarget();
if (DisableSchedCycles || !NeedLatency)
HazardRec = new ScheduleHazardRecognizer();
else
HazardRec = STI.getInstrInfo()->CreateTargetHazardRecognizer(&STI, this);
}
~ScheduleDAGRRList() override {
delete HazardRec;
delete AvailableQueue;
}
void Schedule() override;
ScheduleHazardRecognizer *getHazardRec() { return HazardRec; }
/// IsReachable - Checks if SU is reachable from TargetSU.
bool IsReachable(const SUnit *SU, const SUnit *TargetSU) {
return Topo.IsReachable(SU, TargetSU);
}
/// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
/// create a cycle.
bool WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
return Topo.WillCreateCycle(SU, TargetSU);
}
/// AddPred - adds a predecessor edge to SUnit SU.
/// This returns true if this is a new predecessor.
/// Updates the topological ordering if required.
void AddPred(SUnit *SU, const SDep &D) {
Topo.AddPred(SU, D.getSUnit());
SU->addPred(D);
}
/// RemovePred - removes a predecessor edge from SUnit SU.
/// This returns true if an edge was removed.
/// Updates the topological ordering if required.
void RemovePred(SUnit *SU, const SDep &D) {
Topo.RemovePred(SU, D.getSUnit());
SU->removePred(D);
}
private:
bool isReady(SUnit *SU) {
return DisableSchedCycles || !AvailableQueue->hasReadyFilter() ||
AvailableQueue->isReady(SU);
}
void ReleasePred(SUnit *SU, const SDep *PredEdge);
void ReleasePredecessors(SUnit *SU);
void ReleasePending();
void AdvanceToCycle(unsigned NextCycle);
void AdvancePastStalls(SUnit *SU);
void EmitNode(SUnit *SU);
void ScheduleNodeBottomUp(SUnit*);
void CapturePred(SDep *PredEdge);
void UnscheduleNodeBottomUp(SUnit*);
void RestoreHazardCheckerBottomUp();
void BacktrackBottomUp(SUnit*, SUnit*);
SUnit *TryUnfoldSU(SUnit *);
SUnit *CopyAndMoveSuccessors(SUnit*);
void InsertCopiesAndMoveSuccs(SUnit*, unsigned,
const TargetRegisterClass*,
const TargetRegisterClass*,
SmallVectorImpl<SUnit*>&);
bool DelayForLiveRegsBottomUp(SUnit*, SmallVectorImpl<unsigned>&);
void releaseInterferences(unsigned Reg = 0);
SUnit *PickNodeToScheduleBottomUp();
void ListScheduleBottomUp();
/// CreateNewSUnit - Creates a new SUnit and returns a pointer to it.
/// Updates the topological ordering if required.
SUnit *CreateNewSUnit(SDNode *N) {
unsigned NumSUnits = SUnits.size();
SUnit *NewNode = newSUnit(N);
// Update the topological ordering.
if (NewNode->NodeNum >= NumSUnits)
Topo.InitDAGTopologicalSorting();
return NewNode;
}
/// CreateClone - Creates a new SUnit from an existing one.
/// Updates the topological ordering if required.
SUnit *CreateClone(SUnit *N) {
unsigned NumSUnits = SUnits.size();
SUnit *NewNode = Clone(N);
// Update the topological ordering.
if (NewNode->NodeNum >= NumSUnits)
Topo.InitDAGTopologicalSorting();
return NewNode;
}
/// forceUnitLatencies - Register-pressure-reducing scheduling doesn't
/// need actual latency information but the hybrid scheduler does.
bool forceUnitLatencies() const override {
return !NeedLatency;
}
};
} // end anonymous namespace
/// GetCostForDef - Looks up the register class and cost for a given definition.
/// Typically this just means looking up the representative register class,
/// but for untyped values (MVT::Untyped) it means inspecting the node's
/// opcode to determine what register class is being generated.
static void GetCostForDef(const ScheduleDAGSDNodes::RegDefIter &RegDefPos,
const TargetLowering *TLI,
const TargetInstrInfo *TII,
const TargetRegisterInfo *TRI,
unsigned &RegClass, unsigned &Cost,
const MachineFunction &MF) {
MVT VT = RegDefPos.GetValue();
// Special handling for untyped values. These values can only come from
// the expansion of custom DAG-to-DAG patterns.
if (VT == MVT::Untyped) {
const SDNode *Node = RegDefPos.GetNode();
// Special handling for CopyFromReg of untyped values.
if (!Node->isMachineOpcode() && Node->getOpcode() == ISD::CopyFromReg) {
unsigned Reg = cast<RegisterSDNode>(Node->getOperand(1))->getReg();
const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(Reg);
RegClass = RC->getID();
Cost = 1;
return;
}
unsigned Opcode = Node->getMachineOpcode();
if (Opcode == TargetOpcode::REG_SEQUENCE) {
unsigned DstRCIdx = cast<ConstantSDNode>(Node->getOperand(0))->getZExtValue();
const TargetRegisterClass *RC = TRI->getRegClass(DstRCIdx);
RegClass = RC->getID();
Cost = 1;
return;
}
unsigned Idx = RegDefPos.GetIdx();
const MCInstrDesc Desc = TII->get(Opcode);
const TargetRegisterClass *RC = TII->getRegClass(Desc, Idx, TRI, MF);
RegClass = RC->getID();
// FIXME: Cost arbitrarily set to 1 because there doesn't seem to be a
// better way to determine it.
Cost = 1;
} else {
RegClass = TLI->getRepRegClassFor(VT)->getID();
Cost = TLI->getRepRegClassCostFor(VT);
}
}
/// Schedule - Schedule the DAG using list scheduling.
void ScheduleDAGRRList::Schedule() {
LLVM_DEBUG(dbgs() << "********** List Scheduling " << printMBBReference(*BB)
<< " '" << BB->getName() << "' **********\n");
CurCycle = 0;
IssueCount = 0;
MinAvailableCycle =
DisableSchedCycles ? 0 : std::numeric_limits<unsigned>::max();
NumLiveRegs = 0;
// Allocate slots for each physical register, plus one for a special register
// to track the virtual resource of a calling sequence.
LiveRegDefs.reset(new SUnit*[TRI->getNumRegs() + 1]());
LiveRegGens.reset(new SUnit*[TRI->getNumRegs() + 1]());
CallSeqEndForStart.clear();
assert(Interferences.empty() && LRegsMap.empty() && "stale Interferences");
// Build the scheduling graph.
BuildSchedGraph(nullptr);
LLVM_DEBUG(dump());
Topo.InitDAGTopologicalSorting();
AvailableQueue->initNodes(SUnits);
HazardRec->Reset();
// Execute the actual scheduling loop.
ListScheduleBottomUp();
AvailableQueue->releaseState();
LLVM_DEBUG({
dbgs() << "*** Final schedule ***\n";
dumpSchedule();
dbgs() << '\n';
});
}
//===----------------------------------------------------------------------===//
// Bottom-Up Scheduling
//===----------------------------------------------------------------------===//
/// ReleasePred - Decrement the NumSuccsLeft count of a predecessor. Add it to
/// the AvailableQueue if the count reaches zero. Also update its cycle bound.
void ScheduleDAGRRList::ReleasePred(SUnit *SU, const SDep *PredEdge) {
SUnit *PredSU = PredEdge->getSUnit();
#ifndef NDEBUG
if (PredSU->NumSuccsLeft == 0) {
dbgs() << "*** Scheduling failed! ***\n";
dumpNode(*PredSU);
dbgs() << " has been released too many times!\n";
llvm_unreachable(nullptr);
}
#endif
--PredSU->NumSuccsLeft;
if (!forceUnitLatencies()) {
// Updating predecessor's height. This is now the cycle when the
// predecessor can be scheduled without causing a pipeline stall.
PredSU->setHeightToAtLeast(SU->getHeight() + PredEdge->getLatency());
}
// If all the node's successors are scheduled, this node is ready
// to be scheduled. Ignore the special EntrySU node.
if (PredSU->NumSuccsLeft == 0 && PredSU != &EntrySU) {
PredSU->isAvailable = true;
unsigned Height = PredSU->getHeight();
if (Height < MinAvailableCycle)
MinAvailableCycle = Height;
if (isReady(PredSU)) {
AvailableQueue->push(PredSU);
}
// CapturePred and others may have left the node in the pending queue, avoid
// adding it twice.
else if (!PredSU->isPending) {
PredSU->isPending = true;
PendingQueue.push_back(PredSU);
}
}
}
/// IsChainDependent - Test if Outer is reachable from Inner through
/// chain dependencies.
static bool IsChainDependent(SDNode *Outer, SDNode *Inner,
unsigned NestLevel,
const TargetInstrInfo *TII) {
SDNode *N = Outer;
while (true) {
if (N == Inner)
return true;
// For a TokenFactor, examine each operand. There may be multiple ways
// to get to the CALLSEQ_BEGIN, but we need to find the path with the
// most nesting in order to ensure that we find the corresponding match.
if (N->getOpcode() == ISD::TokenFactor) {
for (const SDValue &Op : N->op_values())
if (IsChainDependent(Op.getNode(), Inner, NestLevel, TII))
return true;
return false;
}
// Check for a lowered CALLSEQ_BEGIN or CALLSEQ_END.
if (N->isMachineOpcode()) {
if (N->getMachineOpcode() == TII->getCallFrameDestroyOpcode()) {
++NestLevel;
} else if (N->getMachineOpcode() == TII->getCallFrameSetupOpcode()) {
if (NestLevel == 0)
return false;
--NestLevel;
}
}
// Otherwise, find the chain and continue climbing.
for (const SDValue &Op : N->op_values())
if (Op.getValueType() == MVT::Other) {
N = Op.getNode();
goto found_chain_operand;
}
return false;
found_chain_operand:;
if (N->getOpcode() == ISD::EntryToken)
return false;
}
}
/// FindCallSeqStart - Starting from the (lowered) CALLSEQ_END node, locate
/// the corresponding (lowered) CALLSEQ_BEGIN node.
///
/// NestLevel and MaxNested are used in recursion to indcate the current level
/// of nesting of CALLSEQ_BEGIN and CALLSEQ_END pairs, as well as the maximum
/// level seen so far.
///
/// TODO: It would be better to give CALLSEQ_END an explicit operand to point
/// to the corresponding CALLSEQ_BEGIN to avoid needing to search for it.
static SDNode *
FindCallSeqStart(SDNode *N, unsigned &NestLevel, unsigned &MaxNest,
const TargetInstrInfo *TII) {
while (true) {
// For a TokenFactor, examine each operand. There may be multiple ways
// to get to the CALLSEQ_BEGIN, but we need to find the path with the
// most nesting in order to ensure that we find the corresponding match.
if (N->getOpcode() == ISD::TokenFactor) {
SDNode *Best = nullptr;
unsigned BestMaxNest = MaxNest;
for (const SDValue &Op : N->op_values()) {
unsigned MyNestLevel = NestLevel;
unsigned MyMaxNest = MaxNest;
if (SDNode *New = FindCallSeqStart(Op.getNode(),
MyNestLevel, MyMaxNest, TII))
if (!Best || (MyMaxNest > BestMaxNest)) {
Best = New;
BestMaxNest = MyMaxNest;
}
}
assert(Best);
MaxNest = BestMaxNest;
return Best;
}
// Check for a lowered CALLSEQ_BEGIN or CALLSEQ_END.
if (N->isMachineOpcode()) {
if (N->getMachineOpcode() == TII->getCallFrameDestroyOpcode()) {
++NestLevel;
MaxNest = std::max(MaxNest, NestLevel);
} else if (N->getMachineOpcode() == TII->getCallFrameSetupOpcode()) {
assert(NestLevel != 0);
--NestLevel;
if (NestLevel == 0)
return N;
}
}
// Otherwise, find the chain and continue climbing.
for (const SDValue &Op : N->op_values())
if (Op.getValueType() == MVT::Other) {
N = Op.getNode();
goto found_chain_operand;
}
return nullptr;
found_chain_operand:;
if (N->getOpcode() == ISD::EntryToken)
return nullptr;
}
}
/// Call ReleasePred for each predecessor, then update register live def/gen.
/// Always update LiveRegDefs for a register dependence even if the current SU
/// also defines the register. This effectively create one large live range
/// across a sequence of two-address node. This is important because the
/// entire chain must be scheduled together. Example:
///
/// flags = (3) add
/// flags = (2) addc flags
/// flags = (1) addc flags
///
/// results in
///
/// LiveRegDefs[flags] = 3
/// LiveRegGens[flags] = 1
///
/// If (2) addc is unscheduled, then (1) addc must also be unscheduled to avoid
/// interference on flags.
void ScheduleDAGRRList::ReleasePredecessors(SUnit *SU) {
// Bottom up: release predecessors
for (SDep &Pred : SU->Preds) {
ReleasePred(SU, &Pred);
if (Pred.isAssignedRegDep()) {
// This is a physical register dependency and it's impossible or
// expensive to copy the register. Make sure nothing that can
// clobber the register is scheduled between the predecessor and
// this node.
SUnit *RegDef = LiveRegDefs[Pred.getReg()]; (void)RegDef;
assert((!RegDef || RegDef == SU || RegDef == Pred.getSUnit()) &&
"interference on register dependence");
LiveRegDefs[Pred.getReg()] = Pred.getSUnit();
if (!LiveRegGens[Pred.getReg()]) {
++NumLiveRegs;
LiveRegGens[Pred.getReg()] = SU;
}
}
}
// If we're scheduling a lowered CALLSEQ_END, find the corresponding
// CALLSEQ_BEGIN. Inject an artificial physical register dependence between
// these nodes, to prevent other calls from being interscheduled with them.
unsigned CallResource = TRI->getNumRegs();
if (!LiveRegDefs[CallResource])
for (SDNode *Node = SU->getNode(); Node; Node = Node->getGluedNode())
if (Node->isMachineOpcode() &&
Node->getMachineOpcode() == TII->getCallFrameDestroyOpcode()) {
unsigned NestLevel = 0;
unsigned MaxNest = 0;
SDNode *N = FindCallSeqStart(Node, NestLevel, MaxNest, TII);
assert(N && "Must find call sequence start");
SUnit *Def = &SUnits[N->getNodeId()];
CallSeqEndForStart[Def] = SU;
++NumLiveRegs;
LiveRegDefs[CallResource] = Def;
LiveRegGens[CallResource] = SU;
break;
}
}
/// Check to see if any of the pending instructions are ready to issue. If
/// so, add them to the available queue.
void ScheduleDAGRRList::ReleasePending() {
if (DisableSchedCycles) {
assert(PendingQueue.empty() && "pending instrs not allowed in this mode");
return;
}
// If the available queue is empty, it is safe to reset MinAvailableCycle.
if (AvailableQueue->empty())
MinAvailableCycle = std::numeric_limits<unsigned>::max();
// 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) {
unsigned ReadyCycle = PendingQueue[i]->getHeight();
if (ReadyCycle < MinAvailableCycle)
MinAvailableCycle = ReadyCycle;
if (PendingQueue[i]->isAvailable) {
if (!isReady(PendingQueue[i]))
continue;
AvailableQueue->push(PendingQueue[i]);
}
PendingQueue[i]->isPending = false;
PendingQueue[i] = PendingQueue.back();
PendingQueue.pop_back();
--i; --e;
}
}
/// Move the scheduler state forward by the specified number of Cycles.
void ScheduleDAGRRList::AdvanceToCycle(unsigned NextCycle) {
if (NextCycle <= CurCycle)
return;
IssueCount = 0;
AvailableQueue->setCurCycle(NextCycle);
if (!HazardRec->isEnabled()) {
// Bypass lots of virtual calls in case of long latency.
CurCycle = NextCycle;
}
else {
for (; CurCycle != NextCycle; ++CurCycle) {
HazardRec->RecedeCycle();
}
}
// FIXME: Instead of visiting the pending Q each time, set a dirty flag on the
// available Q to release pending nodes at least once before popping.
ReleasePending();
}
/// Move the scheduler state forward until the specified node's dependents are
/// ready and can be scheduled with no resource conflicts.
void ScheduleDAGRRList::AdvancePastStalls(SUnit *SU) {
if (DisableSchedCycles)
return;
// FIXME: Nodes such as CopyFromReg probably should not advance the current
// cycle. Otherwise, we can wrongly mask real stalls. If the non-machine node
// has predecessors the cycle will be advanced when they are scheduled.
// But given the crude nature of modeling latency though such nodes, we
// currently need to treat these nodes like real instructions.
// if (!SU->getNode() || !SU->getNode()->isMachineOpcode()) return;
unsigned ReadyCycle = SU->getHeight();
// Bump CurCycle to account for latency. We assume the latency of other
// available instructions may be hidden by the stall (not a full pipe stall).
// This updates the hazard recognizer's cycle before reserving resources for
// this instruction.
AdvanceToCycle(ReadyCycle);
// Calls are scheduled in their preceding cycle, so don't conflict with
// hazards from instructions after the call. EmitNode will reset the
// scoreboard state before emitting the call.
if (SU->isCall)
return;
// FIXME: For resource conflicts in very long non-pipelined stages, we
// should probably skip ahead here to avoid useless scoreboard checks.
int Stalls = 0;
while (true) {
ScheduleHazardRecognizer::HazardType HT =
HazardRec->getHazardType(SU, -Stalls);
if (HT == ScheduleHazardRecognizer::NoHazard)
break;
++Stalls;
}
AdvanceToCycle(CurCycle + Stalls);
}
/// Record this SUnit in the HazardRecognizer.
/// Does not update CurCycle.
void ScheduleDAGRRList::EmitNode(SUnit *SU) {
if (!HazardRec->isEnabled())
return;
// Check for phys reg copy.
if (!SU->getNode())
return;
switch (SU->getNode()->getOpcode()) {
default:
assert(SU->getNode()->isMachineOpcode() &&
"This target-independent node should not be scheduled.");
break;
case ISD::MERGE_VALUES:
case ISD::TokenFactor:
case ISD::LIFETIME_START:
case ISD::LIFETIME_END:
case ISD::CopyToReg:
case ISD::CopyFromReg:
case ISD::EH_LABEL:
// Noops don't affect the scoreboard state. Copies are likely to be
// removed.
return;
case ISD::INLINEASM:
case ISD::INLINEASM_BR:
// For inline asm, clear the pipeline state.
HazardRec->Reset();
return;
}
if (SU->isCall) {
// Calls are scheduled with their preceding instructions. For bottom-up
// scheduling, clear the pipeline state before emitting.
HazardRec->Reset();
}
HazardRec->EmitInstruction(SU);
}
static void resetVRegCycle(SUnit *SU);
/// 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 ScheduleDAGRRList::ScheduleNodeBottomUp(SUnit *SU) {
LLVM_DEBUG(dbgs() << "\n*** Scheduling [" << CurCycle << "]: ");
LLVM_DEBUG(dumpNode(*SU));
#ifndef NDEBUG
if (CurCycle < SU->getHeight())
LLVM_DEBUG(dbgs() << " Height [" << SU->getHeight()
<< "] pipeline stall!\n");
#endif
// FIXME: Do not modify node height. It may interfere with
// backtracking. Instead add a "ready cycle" to SUnit. Before scheduling the
// node its ready cycle can aid heuristics, and after scheduling it can
// indicate the scheduled cycle.
SU->setHeightToAtLeast(CurCycle);
// Reserve resources for the scheduled instruction.
EmitNode(SU);
Sequence.push_back(SU);
AvailableQueue->scheduledNode(SU);
// If HazardRec is disabled, and each inst counts as one cycle, then
// advance CurCycle before ReleasePredecessors to avoid useless pushes to
// PendingQueue for schedulers that implement HasReadyFilter.
if (!HazardRec->isEnabled() && AvgIPC < 2)
AdvanceToCycle(CurCycle + 1);
// Update liveness of predecessors before successors to avoid treating a
// two-address node as a live range def.
ReleasePredecessors(SU);
// Release all the implicit physical register defs that are live.
for (SDep &Succ : SU->Succs) {
// LiveRegDegs[Succ.getReg()] != SU when SU is a two-address node.
if (Succ.isAssignedRegDep() && LiveRegDefs[Succ.getReg()] == SU) {
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
--NumLiveRegs;
LiveRegDefs[Succ.getReg()] = nullptr;
LiveRegGens[Succ.getReg()] = nullptr;
releaseInterferences(Succ.getReg());
}
}
// Release the special call resource dependence, if this is the beginning
// of a call.
unsigned CallResource = TRI->getNumRegs();
if (LiveRegDefs[CallResource] == SU)
for (const SDNode *SUNode = SU->getNode(); SUNode;
SUNode = SUNode->getGluedNode()) {
if (SUNode->isMachineOpcode() &&
SUNode->getMachineOpcode() == TII->getCallFrameSetupOpcode()) {
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
--NumLiveRegs;
LiveRegDefs[CallResource] = nullptr;
LiveRegGens[CallResource] = nullptr;
releaseInterferences(CallResource);
}
}
resetVRegCycle(SU);
SU->isScheduled = true;
// Conditions under which the scheduler should eagerly advance the cycle:
// (1) No available instructions
// (2) All pipelines full, so available instructions must have hazards.
//
// If HazardRec is disabled, the cycle was pre-advanced before calling
// ReleasePredecessors. In that case, IssueCount should remain 0.
//
// Check AvailableQueue after ReleasePredecessors in case of zero latency.
if (HazardRec->isEnabled() || AvgIPC > 1) {
if (SU->getNode() && SU->getNode()->isMachineOpcode())
++IssueCount;
if ((HazardRec->isEnabled() && HazardRec->atIssueLimit())
|| (!HazardRec->isEnabled() && IssueCount == AvgIPC))
AdvanceToCycle(CurCycle + 1);
}
}
/// CapturePred - This does the opposite of ReleasePred. Since SU is being
/// unscheduled, increase the succ left count of its predecessors. Remove
/// them from AvailableQueue if necessary.
void ScheduleDAGRRList::CapturePred(SDep *PredEdge) {
SUnit *PredSU = PredEdge->getSUnit();
if (PredSU->isAvailable) {
PredSU->isAvailable = false;
if (!PredSU->isPending)
AvailableQueue->remove(PredSU);
}
assert(PredSU->NumSuccsLeft < std::numeric_limits<unsigned>::max() &&
"NumSuccsLeft will overflow!");
++PredSU->NumSuccsLeft;
}
/// UnscheduleNodeBottomUp - Remove the node from the schedule, update its and
/// its predecessor states to reflect the change.
void ScheduleDAGRRList::UnscheduleNodeBottomUp(SUnit *SU) {
LLVM_DEBUG(dbgs() << "*** Unscheduling [" << SU->getHeight() << "]: ");
LLVM_DEBUG(dumpNode(*SU));
for (SDep &Pred : SU->Preds) {
CapturePred(&Pred);
if (Pred.isAssignedRegDep() && SU == LiveRegGens[Pred.getReg()]){
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
assert(LiveRegDefs[Pred.getReg()] == Pred.getSUnit() &&
"Physical register dependency violated?");
--NumLiveRegs;
LiveRegDefs[Pred.getReg()] = nullptr;
LiveRegGens[Pred.getReg()] = nullptr;
releaseInterferences(Pred.getReg());
}
}
// Reclaim the special call resource dependence, if this is the beginning
// of a call.
unsigned CallResource = TRI->getNumRegs();
for (const SDNode *SUNode = SU->getNode(); SUNode;
SUNode = SUNode->getGluedNode()) {
if (SUNode->isMachineOpcode() &&
SUNode->getMachineOpcode() == TII->getCallFrameSetupOpcode()) {
SUnit *SeqEnd = CallSeqEndForStart[SU];
assert(SeqEnd && "Call sequence start/end must be known");
assert(!LiveRegDefs[CallResource]);
assert(!LiveRegGens[CallResource]);
++NumLiveRegs;
LiveRegDefs[CallResource] = SU;
LiveRegGens[CallResource] = SeqEnd;
}
}
// Release the special call resource dependence, if this is the end
// of a call.
if (LiveRegGens[CallResource] == SU)
for (const SDNode *SUNode = SU->getNode(); SUNode;
SUNode = SUNode->getGluedNode()) {
if (SUNode->isMachineOpcode() &&
SUNode->getMachineOpcode() == TII->getCallFrameDestroyOpcode()) {
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
assert(LiveRegDefs[CallResource]);
assert(LiveRegGens[CallResource]);
--NumLiveRegs;
LiveRegDefs[CallResource] = nullptr;
LiveRegGens[CallResource] = nullptr;
releaseInterferences(CallResource);
}
}
for (auto &Succ : SU->Succs) {
if (Succ.isAssignedRegDep()) {
auto Reg = Succ.getReg();
if (!LiveRegDefs[Reg])
++NumLiveRegs;
// This becomes the nearest def. Note that an earlier def may still be
// pending if this is a two-address node.
LiveRegDefs[Reg] = SU;
// Update LiveRegGen only if was empty before this unscheduling.
// This is to avoid incorrect updating LiveRegGen set in previous run.
if (!LiveRegGens[Reg]) {
// Find the successor with the lowest height.
LiveRegGens[Reg] = Succ.getSUnit();
for (auto &Succ2 : SU->Succs) {
if (Succ2.isAssignedRegDep() && Succ2.getReg() == Reg &&
Succ2.getSUnit()->getHeight() < LiveRegGens[Reg]->getHeight())
LiveRegGens[Reg] = Succ2.getSUnit();
}
}
}
}
if (SU->getHeight() < MinAvailableCycle)
MinAvailableCycle = SU->getHeight();
SU->setHeightDirty();
SU->isScheduled = false;
SU->isAvailable = true;
if (!DisableSchedCycles && AvailableQueue->hasReadyFilter()) {
// Don't make available until backtracking is complete.
SU->isPending = true;
PendingQueue.push_back(SU);
}
else {
AvailableQueue->push(SU);
}
AvailableQueue->unscheduledNode(SU);
}
/// After backtracking, the hazard checker needs to be restored to a state
/// corresponding the current cycle.
void ScheduleDAGRRList::RestoreHazardCheckerBottomUp() {
HazardRec->Reset();
unsigned LookAhead = std::min((unsigned)Sequence.size(),
HazardRec->getMaxLookAhead());
if (LookAhead == 0)
return;
std::vector<SUnit *>::const_iterator I = (Sequence.end() - LookAhead);
unsigned HazardCycle = (*I)->getHeight();
for (auto E = Sequence.end(); I != E; ++I) {
SUnit *SU = *I;
for (; SU->getHeight() > HazardCycle; ++HazardCycle) {
HazardRec->RecedeCycle();
}
EmitNode(SU);
}
}
/// BacktrackBottomUp - Backtrack scheduling to a previous cycle specified in
/// BTCycle in order to schedule a specific node.
void ScheduleDAGRRList::BacktrackBottomUp(SUnit *SU, SUnit *BtSU) {
SUnit *OldSU = Sequence.back();
while (true) {
Sequence.pop_back();
// FIXME: use ready cycle instead of height
CurCycle = OldSU->getHeight();
UnscheduleNodeBottomUp(OldSU);
AvailableQueue->setCurCycle(CurCycle);
if (OldSU == BtSU)
break;
OldSU = Sequence.back();
}
assert(!SU->isSucc(OldSU) && "Something is wrong!");
RestoreHazardCheckerBottomUp();
ReleasePending();
++NumBacktracks;
}
static bool isOperandOf(const SUnit *SU, SDNode *N) {
for (const SDNode *SUNode = SU->getNode(); SUNode;
SUNode = SUNode->getGluedNode()) {
if (SUNode->isOperandOf(N))
return true;
}
return false;
}
/// TryUnfold - Attempt to unfold
SUnit *ScheduleDAGRRList::TryUnfoldSU(SUnit *SU) {
SDNode *N = SU->getNode();
// Use while over if to ease fall through.
SmallVector<SDNode *, 2> NewNodes;
if (!TII->unfoldMemoryOperand(*DAG, N, NewNodes))
return nullptr;
// unfolding an x86 DEC64m operation results in store, dec, load which
// can't be handled here so quit
if (NewNodes.size() == 3)
return nullptr;
assert(NewNodes.size() == 2 && "Expected a load folding node!");
N = NewNodes[1];
SDNode *LoadNode = NewNodes[0];
unsigned NumVals = N->getNumValues();
unsigned OldNumVals = SU->getNode()->getNumValues();
// LoadNode may already exist. This can happen when there is another
// load from the same location and producing the same type of value
// but it has different alignment or volatileness.
bool isNewLoad = true;
SUnit *LoadSU;
if (LoadNode->getNodeId() != -1) {
LoadSU = &SUnits[LoadNode->getNodeId()];
// If LoadSU has already been scheduled, we should clone it but
// this would negate the benefit to unfolding so just return SU.
if (LoadSU->isScheduled)
return SU;
isNewLoad = false;
} else {
LoadSU = CreateNewSUnit(LoadNode);
LoadNode->setNodeId(LoadSU->NodeNum);
InitNumRegDefsLeft(LoadSU);
computeLatency(LoadSU);
}
bool isNewN = true;
SUnit *NewSU;
// This can only happen when isNewLoad is false.
if (N->getNodeId() != -1) {
NewSU = &SUnits[N->getNodeId()];
// If NewSU has already been scheduled, we need to clone it, but this
// negates the benefit to unfolding so just return SU.
if (NewSU->isScheduled)
return SU;
isNewN = false;
} else {
NewSU = CreateNewSUnit(N);
N->setNodeId(NewSU->NodeNum);
const MCInstrDesc &MCID = TII->get(N->getMachineOpcode());
for (unsigned i = 0; i != MCID.getNumOperands(); ++i) {
if (MCID.getOperandConstraint(i, MCOI::TIED_TO) != -1) {
NewSU->isTwoAddress = true;
break;
}
}
if (MCID.isCommutable())
NewSU->isCommutable = true;
InitNumRegDefsLeft(NewSU);
computeLatency(NewSU);
}
LLVM_DEBUG(dbgs() << "Unfolding SU #" << SU->NodeNum << "\n");
// Now that we are committed to unfolding replace DAG Uses.
for (unsigned i = 0; i != NumVals; ++i)
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), i), SDValue(N, i));
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), OldNumVals - 1),
SDValue(LoadNode, 1));
// 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;
SmallVector<SDep, 4> NodeSuccs;
for (SDep &Pred : SU->Preds) {
if (Pred.isCtrl())
ChainPreds.push_back(Pred);
else if (isOperandOf(Pred.getSUnit(), LoadNode))
LoadPreds.push_back(Pred);
else
NodePreds.push_back(Pred);
}
for (SDep &Succ : SU->Succs) {
if (Succ.isCtrl())
ChainSuccs.push_back(Succ);
else
NodeSuccs.push_back(Succ);
}
// Now assign edges to the newly-created nodes.
for (const SDep &Pred : ChainPreds) {
RemovePred(SU, Pred);
if (isNewLoad)
AddPred(LoadSU, Pred);
}
for (const SDep &Pred : LoadPreds) {
RemovePred(SU, Pred);
if (isNewLoad)
AddPred(LoadSU, Pred);
}
for (const SDep &Pred : NodePreds) {
RemovePred(SU, Pred);
AddPred(NewSU, Pred);
}
for (SDep D : NodeSuccs) {
SUnit *SuccDep = D.getSUnit();
D.setSUnit(SU);
RemovePred(SuccDep, D);
D.setSUnit(NewSU);
AddPred(SuccDep, D);
// Balance register pressure.
if (AvailableQueue->tracksRegPressure() && SuccDep->isScheduled &&
!D.isCtrl() && NewSU->NumRegDefsLeft > 0)
--NewSU->NumRegDefsLeft;
}
for (SDep D : ChainSuccs) {
SUnit *SuccDep = D.getSUnit();
D.setSUnit(SU);
RemovePred(SuccDep, D);
if (isNewLoad) {
D.setSUnit(LoadSU);
AddPred(SuccDep, D);
}
}
// Add a data dependency to reflect that NewSU reads the value defined
// by LoadSU.
SDep D(LoadSU, SDep::Data, 0);
D.setLatency(LoadSU->Latency);
AddPred(NewSU, D);
if (isNewLoad)
AvailableQueue->addNode(LoadSU);
if (isNewN)
AvailableQueue->addNode(NewSU);
++NumUnfolds;
if (NewSU->NumSuccsLeft == 0)
NewSU->isAvailable = true;
return NewSU;
}
/// CopyAndMoveSuccessors - Clone the specified node and move its scheduled
/// successors to the newly created node.
SUnit *ScheduleDAGRRList::CopyAndMoveSuccessors(SUnit *SU) {
SDNode *N = SU->getNode();
if (!N)
return nullptr;
LLVM_DEBUG(dbgs() << "Considering duplicating the SU\n");
LLVM_DEBUG(dumpNode(*SU));
if (N->getGluedNode() &&
!TII->canCopyGluedNodeDuringSchedule(N)) {
LLVM_DEBUG(
dbgs()
<< "Giving up because it has incoming glue and the target does not "
"want to copy it\n");
return nullptr;
}
SUnit *NewSU;
bool TryUnfold = false;
for (unsigned i = 0, e = N->getNumValues(); i != e; ++i) {
MVT VT = N->getSimpleValueType(i);
if (VT == MVT::Glue) {
LLVM_DEBUG(dbgs() << "Giving up because it has outgoing glue\n");
return nullptr;
} else if (VT == MVT::Other)
TryUnfold = true;
}
for (const SDValue &Op : N->op_values()) {
MVT VT = Op.getNode()->getSimpleValueType(Op.getResNo());
if (VT == MVT::Glue && !TII->canCopyGluedNodeDuringSchedule(N)) {
LLVM_DEBUG(
dbgs() << "Giving up because it one of the operands is glue and "
"the target does not want to copy it\n");
return nullptr;
}
}
// If possible unfold instruction.
if (TryUnfold) {
SUnit *UnfoldSU = TryUnfoldSU(SU);
if (!UnfoldSU)
return nullptr;
SU = UnfoldSU;
N = SU->getNode();
// If this can be scheduled don't bother duplicating and just return
if (SU->NumSuccsLeft == 0)
return SU;
}
LLVM_DEBUG(dbgs() << " Duplicating SU #" << SU->NodeNum << "\n");
NewSU = CreateClone(SU);
// New SUnit has the exact same predecessors.
for (SDep &Pred : SU->Preds)
if (!Pred.isArtificial())
AddPred(NewSU, Pred);
// Only copy scheduled successors. Cut them from old node's successor
// list and move them over.
SmallVector<std::pair<SUnit *, SDep>, 4> DelDeps;
for (SDep &Succ : SU->Succs) {
if (Succ.isArtificial())
continue;
SUnit *SuccSU = Succ.getSUnit();
if (SuccSU->isScheduled) {
SDep D = Succ;
D.setSUnit(NewSU);
AddPred(SuccSU, D);
D.setSUnit(SU);
DelDeps.push_back(std::make_pair(SuccSU, D));
}
}
for (auto &DelDep : DelDeps)
RemovePred(DelDep.first, DelDep.second);
AvailableQueue->updateNode(SU);
AvailableQueue->addNode(NewSU);
++NumDups;
return NewSU;
}
/// InsertCopiesAndMoveSuccs - Insert register copies and move all
/// scheduled successors of the given SUnit to the last copy.
void ScheduleDAGRRList::InsertCopiesAndMoveSuccs(SUnit *SU, unsigned Reg,
const TargetRegisterClass *DestRC,
const TargetRegisterClass *SrcRC,
SmallVectorImpl<SUnit*> &Copies) {
SUnit *CopyFromSU = CreateNewSUnit(nullptr);
CopyFromSU->CopySrcRC = SrcRC;
CopyFromSU->CopyDstRC = DestRC;
SUnit *CopyToSU = CreateNewSUnit(nullptr);
CopyToSU->CopySrcRC = DestRC;
CopyToSU->CopyDstRC = SrcRC;
// Only copy scheduled successors. Cut them from old node's successor
// list and move them over.
SmallVector<std::pair<SUnit *, SDep>, 4> DelDeps;
for (SDep &Succ : SU->Succs) {
if (Succ.isArtificial())
continue;
SUnit *SuccSU = Succ.getSUnit();
if (SuccSU->isScheduled) {
SDep D = Succ;
D.setSUnit(CopyToSU);
AddPred(SuccSU, D);
DelDeps.push_back(std::make_pair(SuccSU, Succ));
}
else {
// Avoid scheduling the def-side copy before other successors. Otherwise
// we could introduce another physreg interference on the copy and
// continue inserting copies indefinitely.
AddPred(SuccSU, SDep(CopyFromSU, SDep::Artificial));
}
}
for (auto &DelDep : DelDeps)
RemovePred(DelDep.first, DelDep.second);
SDep FromDep(SU, SDep::Data, Reg);
FromDep.setLatency(SU->Latency);
AddPred(CopyFromSU, FromDep);
SDep ToDep(CopyFromSU, SDep::Data, 0);
ToDep.setLatency(CopyFromSU->Latency);
AddPred(CopyToSU, ToDep);
AvailableQueue->updateNode(SU);
AvailableQueue->addNode(CopyFromSU);
AvailableQueue->addNode(CopyToSU);
Copies.push_back(CopyFromSU);
Copies.push_back(CopyToSU);
++NumPRCopies;
}
/// getPhysicalRegisterVT - Returns the ValueType of the physical register
/// definition of the specified node.
/// FIXME: Move to SelectionDAG?
static MVT getPhysicalRegisterVT(SDNode *N, unsigned Reg,
const TargetInstrInfo *TII) {
unsigned NumRes;
if (N->getOpcode() == ISD::CopyFromReg) {
// CopyFromReg has: "chain, Val, glue" so operand 1 gives the type.
NumRes = 1;
} else {
const MCInstrDesc &MCID = TII->get(N->getMachineOpcode());
assert(MCID.ImplicitDefs && "Physical reg def must be in implicit def list!");
NumRes = MCID.getNumDefs();
for (const MCPhysReg *ImpDef = MCID.getImplicitDefs(); *ImpDef; ++ImpDef) {
if (Reg == *ImpDef)
break;
++NumRes;
}
}
return N->getSimpleValueType(NumRes);
}
/// CheckForLiveRegDef - Return true and update live register vector if the
/// specified register def of the specified SUnit clobbers any "live" registers.
static void CheckForLiveRegDef(SUnit *SU, unsigned Reg,
SUnit **LiveRegDefs,
SmallSet<unsigned, 4> &RegAdded,
SmallVectorImpl<unsigned> &LRegs,
const TargetRegisterInfo *TRI) {
for (MCRegAliasIterator AliasI(Reg, TRI, true); AliasI.isValid(); ++AliasI) {
// Check if Ref is live.
if (!LiveRegDefs[*AliasI]) continue;
// Allow multiple uses of the same def.
if (LiveRegDefs[*AliasI] == SU) continue;
// Add Reg to the set of interfering live regs.
if (RegAdded.insert(*AliasI).second) {
LRegs.push_back(*AliasI);
}
}
}
/// CheckForLiveRegDefMasked - Check for any live physregs that are clobbered
/// by RegMask, and add them to LRegs.
static void CheckForLiveRegDefMasked(SUnit *SU, const uint32_t *RegMask,
ArrayRef<SUnit*> LiveRegDefs,
SmallSet<unsigned, 4> &RegAdded,
SmallVectorImpl<unsigned> &LRegs) {
// Look at all live registers. Skip Reg0 and the special CallResource.
for (unsigned i = 1, e = LiveRegDefs.size()-1; i != e; ++i) {
if (!LiveRegDefs[i]) continue;
if (LiveRegDefs[i] == SU) continue;
if (!MachineOperand::clobbersPhysReg(RegMask, i)) continue;
if (RegAdded.insert(i).second)
LRegs.push_back(i);
}
}
/// getNodeRegMask - Returns the register mask attached to an SDNode, if any.
static const uint32_t *getNodeRegMask(const SDNode *N) {
for (const SDValue &Op : N->op_values())
if (const auto *RegOp = dyn_cast<RegisterMaskSDNode>(Op.getNode()))
return RegOp->getRegMask();
return nullptr;
}
/// 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
/// whatever is necessary (i.e. backtracking or cloning) to make it possible.
bool ScheduleDAGRRList::
DelayForLiveRegsBottomUp(SUnit *SU, SmallVectorImpl<unsigned> &LRegs) {
if (NumLiveRegs == 0)
return false;
SmallSet<unsigned, 4> RegAdded;
// If this node would clobber any "live" register, then it's not ready.
//
// If SU is the currently live definition of the same register that it uses,
// then we are free to schedule it.
for (SDep &Pred : SU->Preds) {
if (Pred.isAssignedRegDep() && LiveRegDefs[Pred.getReg()] != SU)
CheckForLiveRegDef(Pred.getSUnit(), Pred.getReg(), LiveRegDefs.get(),
RegAdded, LRegs, TRI);
}
for (SDNode *Node = SU->getNode(); Node; Node = Node->getGluedNode()) {
if (Node->getOpcode() == ISD::INLINEASM ||
Node->getOpcode() == ISD::INLINEASM_BR) {
// Inline asm can clobber physical defs.
unsigned NumOps = Node->getNumOperands();
if (Node->getOperand(NumOps-1).getValueType() == MVT::Glue)
--NumOps; // Ignore the glue operand.
for (unsigned i = InlineAsm::Op_FirstOperand; i != NumOps;) {
unsigned Flags =
cast<ConstantSDNode>(Node->getOperand(i))->getZExtValue();
unsigned NumVals = InlineAsm::getNumOperandRegisters(Flags);
++i; // Skip the ID value.
if (InlineAsm::isRegDefKind(Flags) ||
InlineAsm::isRegDefEarlyClobberKind(Flags) ||
InlineAsm::isClobberKind(Flags)) {
// 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.get(), RegAdded, LRegs, TRI);
}
} else
i += NumVals;
}
continue;
}
if (!Node->isMachineOpcode())
continue;
// If we're in the middle of scheduling a call, don't begin scheduling
// another call. Also, don't allow any physical registers to be live across
// the call.
if (Node->getMachineOpcode() == TII->getCallFrameDestroyOpcode()) {
// Check the special calling-sequence resource.
unsigned CallResource = TRI->getNumRegs();
if (LiveRegDefs[CallResource]) {
SDNode *Gen = LiveRegGens[CallResource]->getNode();
while (SDNode *Glued = Gen->getGluedNode())
Gen = Glued;
if (!IsChainDependent(Gen, Node, 0, TII) &&
RegAdded.insert(CallResource).second)
LRegs.push_back(CallResource);
}
}
if (const uint32_t *RegMask = getNodeRegMask(Node))
CheckForLiveRegDefMasked(SU, RegMask,
makeArrayRef(LiveRegDefs.get(), TRI->getNumRegs()),
RegAdded, LRegs);
const MCInstrDesc &MCID = TII->get(Node->getMachineOpcode());
if (MCID.hasOptionalDef()) {
// Most ARM instructions have an OptionalDef for CPSR, to model the S-bit.
// This operand can be either a def of CPSR, if the S bit is set; or a use
// of %noreg. When the OptionalDef is set to a valid register, we need to
// handle it in the same way as an ImplicitDef.
for (unsigned i = 0; i < MCID.getNumDefs(); ++i)
if (MCID.OpInfo[i].isOptionalDef()) {
const SDValue &OptionalDef = Node->getOperand(i - Node->getNumValues());
unsigned Reg = cast<RegisterSDNode>(OptionalDef)->getReg();
CheckForLiveRegDef(SU, Reg, LiveRegDefs.get(), RegAdded, LRegs, TRI);
}
}
if (!MCID.ImplicitDefs)
continue;
for (const MCPhysReg *Reg = MCID.getImplicitDefs(); *Reg; ++Reg)
CheckForLiveRegDef(SU, *Reg, LiveRegDefs.get(), RegAdded, LRegs, TRI);
}
return !LRegs.empty();
}
void ScheduleDAGRRList::releaseInterferences(unsigned Reg) {
// Add the nodes that aren't ready back onto the available list.
for (unsigned i = Interferences.size(); i > 0; --i) {
SUnit *SU = Interferences[i-1];
LRegsMapT::iterator LRegsPos = LRegsMap.find(SU);
if (Reg) {
SmallVectorImpl<unsigned> &LRegs = LRegsPos->second;
if (!is_contained(LRegs, Reg))
continue;
}
SU->isPending = false;
// The interfering node may no longer be available due to backtracking.
// Furthermore, it may have been made available again, in which case it is
// now already in the AvailableQueue.
if (SU->isAvailable && !SU->NodeQueueId) {
LLVM_DEBUG(dbgs() << " Repushing SU #" << SU->NodeNum << '\n');
AvailableQueue->push(SU);
}
if (i < Interferences.size())
Interferences[i-1] = Interferences.back();
Interferences.pop_back();
LRegsMap.erase(LRegsPos);
}
}
/// Return a node that can be scheduled in this cycle. Requirements:
/// (1) Ready: latency has been satisfied
/// (2) No Hazards: resources are available
/// (3) No Interferences: may unschedule to break register interferences.
SUnit *ScheduleDAGRRList::PickNodeToScheduleBottomUp() {
SUnit *CurSU = AvailableQueue->empty() ? nullptr : AvailableQueue->pop();
auto FindAvailableNode = [&]() {
while (CurSU) {
SmallVector<unsigned, 4> LRegs;
if (!DelayForLiveRegsBottomUp(CurSU, LRegs))
break;
LLVM_DEBUG(dbgs() << " Interfering reg ";
if (LRegs[0] == TRI->getNumRegs()) dbgs() << "CallResource";
else dbgs() << printReg(LRegs[0], TRI);
dbgs() << " SU #" << CurSU->NodeNum << '\n');
std::pair<LRegsMapT::iterator, bool> LRegsPair =
LRegsMap.insert(std::make_pair(CurSU, LRegs));
if (LRegsPair.second) {
CurSU->isPending = true; // This SU is not in AvailableQueue right now.
Interferences.push_back(CurSU);
}
else {
assert(CurSU->isPending && "Interferences are pending");
// Update the interference with current live regs.
LRegsPair.first->second = LRegs;
}
CurSU = AvailableQueue->pop();
}
};
FindAvailableNode();
if (CurSU)
return CurSU;
// All candidates are delayed due to live physical reg dependencies.
// Try backtracking, code duplication, or inserting cross class copies
// to resolve it.
for (SUnit *TrySU : Interferences) {
SmallVectorImpl<unsigned> &LRegs = LRegsMap[TrySU];
// Try unscheduling up to the point where it's safe to schedule
// this node.
SUnit *BtSU = nullptr;
unsigned LiveCycle = std::numeric_limits<unsigned>::max();
for (unsigned Reg : LRegs) {
if (LiveRegGens[Reg]->getHeight() < LiveCycle) {
BtSU = LiveRegGens[Reg];
LiveCycle = BtSU->getHeight();
}
}
if (!WillCreateCycle(TrySU, BtSU)) {
// BacktrackBottomUp mutates Interferences!
BacktrackBottomUp(TrySU, BtSU);
// Force the current node to be scheduled before the node that
// requires the physical reg dep.
if (BtSU->isAvailable) {
BtSU->isAvailable = false;
if (!BtSU->isPending)
AvailableQueue->remove(BtSU);
}
LLVM_DEBUG(dbgs() << "ARTIFICIAL edge from SU(" << BtSU->NodeNum
<< ") to SU(" << TrySU->NodeNum << ")\n");
AddPred(TrySU, SDep(BtSU, SDep::Artificial));
// If one or more successors has been unscheduled, then the current
// node is no longer available.
if (!TrySU->isAvailable || !TrySU->NodeQueueId) {
LLVM_DEBUG(dbgs() << "TrySU not available; choosing node from queue\n");
CurSU = AvailableQueue->pop();
} else {
LLVM_DEBUG(dbgs() << "TrySU available\n");
// Available and in AvailableQueue
AvailableQueue->remove(TrySU);
CurSU = TrySU;
}
FindAvailableNode();
// Interferences has been mutated. We must break.
break;
}
}
if (!CurSU) {
// Can't backtrack. If it's too expensive to copy the value, then try
// duplicate the nodes that produces these "too expensive to copy"
// values to break the dependency. In case even that doesn't work,
// insert cross class copies.
// If it's not too expensive, i.e. cost != -1, issue copies.
SUnit *TrySU = Interferences[0];
SmallVectorImpl<unsigned> &LRegs = LRegsMap[TrySU];
assert(LRegs.size() == 1 && "Can't handle this yet!");
unsigned Reg = LRegs[0];
SUnit *LRDef = LiveRegDefs[Reg];
MVT VT = getPhysicalRegisterVT(LRDef->getNode(), Reg, TII);
const TargetRegisterClass *RC =
TRI->getMinimalPhysRegClass(Reg, VT);
const TargetRegisterClass *DestRC = TRI->getCrossCopyRegClass(RC);
// If cross copy register class is the same as RC, then it must be possible
// copy the value directly. Do not try duplicate the def.
// If cross copy register class is not the same as RC, then it's possible to
// copy the value but it require cross register class copies and it is
// expensive.
// If cross copy register class is null, then it's not possible to copy
// the value at all.
SUnit *NewDef = nullptr;
if (DestRC != RC) {
NewDef = CopyAndMoveSuccessors(LRDef);
if (!DestRC && !NewDef)
report_fatal_error("Can't handle live physical register dependency!");
}
if (!NewDef) {
// Issue copies, these can be expensive cross register class copies.
SmallVector<SUnit*, 2> Copies;
InsertCopiesAndMoveSuccs(LRDef, Reg, DestRC, RC, Copies);
LLVM_DEBUG(dbgs() << " Adding an edge from SU #" << TrySU->NodeNum
<< " to SU #" << Copies.front()->NodeNum << "\n");
AddPred(TrySU, SDep(Copies.front(), SDep::Artificial));
NewDef = Copies.back();
}
LLVM_DEBUG(dbgs() << " Adding an edge from SU #" << NewDef->NodeNum
<< " to SU #" << TrySU->NodeNum << "\n");
LiveRegDefs[Reg] = NewDef;
AddPred(NewDef, SDep(TrySU, SDep::Artificial));
TrySU->isAvailable = false;
CurSU = NewDef;
}
assert(CurSU && "Unable to resolve live physical register dependencies!");
return CurSU;
}
/// ListScheduleBottomUp - The main loop of list scheduling for bottom-up
/// schedulers.
void ScheduleDAGRRList::ListScheduleBottomUp() {
// Release any predecessors of the special Exit node.
ReleasePredecessors(&ExitSU);
// Add root to Available queue.
if (!SUnits.empty()) {
SUnit *RootSU = &SUnits[DAG->getRoot().getNode()->getNodeId()];
assert(RootSU->Succs.empty() && "Graph root shouldn't have successors!");
RootSU->isAvailable = true;
AvailableQueue->push(RootSU);
}
// While Available queue is not empty, grab the node with the highest
// priority. If it is not ready put it back. Schedule the node.
Sequence.reserve(SUnits.size());
while (!AvailableQueue->empty() || !Interferences.empty()) {
LLVM_DEBUG(dbgs() << "\nExamining Available:\n";
AvailableQueue->dump(this));
// Pick the best node to schedule taking all constraints into
// consideration.
SUnit *SU = PickNodeToScheduleBottomUp();
AdvancePastStalls(SU);
ScheduleNodeBottomUp(SU);
while (AvailableQueue->empty() && !PendingQueue.empty()) {
// Advance the cycle to free resources. Skip ahead to the next ready SU.
assert(MinAvailableCycle < std::numeric_limits<unsigned>::max() &&
"MinAvailableCycle uninitialized");
AdvanceToCycle(std::max(CurCycle + 1, MinAvailableCycle));
}
}
// Reverse the order if it is bottom up.
std::reverse(Sequence.begin(), Sequence.end());
#ifndef NDEBUG
VerifyScheduledSequence(/*isBottomUp=*/true);
#endif
}
namespace {
class RegReductionPQBase;
struct queue_sort {
bool isReady(SUnit* SU, unsigned CurCycle) const { return true; }
};
#ifndef NDEBUG
template<class SF>
struct reverse_sort : public queue_sort {
SF &SortFunc;
reverse_sort(SF &sf) : SortFunc(sf) {}
bool operator()(SUnit* left, SUnit* right) const {
// reverse left/right rather than simply !SortFunc(left, right)
// to expose different paths in the comparison logic.
return SortFunc(right, left);
}
};
#endif // NDEBUG
/// bu_ls_rr_sort - Priority function for bottom up register pressure
// reduction scheduler.
struct bu_ls_rr_sort : public queue_sort {
enum {
IsBottomUp = true,
HasReadyFilter = false
};
RegReductionPQBase *SPQ;
bu_ls_rr_sort(RegReductionPQBase *spq) : SPQ(spq) {}
bool operator()(SUnit* left, SUnit* right) const;
};
// src_ls_rr_sort - Priority function for source order scheduler.
struct src_ls_rr_sort : public queue_sort {
enum {
IsBottomUp = true,
HasReadyFilter = false
};
RegReductionPQBase *SPQ;
src_ls_rr_sort(RegReductionPQBase *spq) : SPQ(spq) {}
bool operator()(SUnit* left, SUnit* right) const;
};
// hybrid_ls_rr_sort - Priority function for hybrid scheduler.
struct hybrid_ls_rr_sort : public queue_sort {
enum {
IsBottomUp = true,
HasReadyFilter = false
};
RegReductionPQBase *SPQ;
hybrid_ls_rr_sort(RegReductionPQBase *spq) : SPQ(spq) {}
bool isReady(SUnit *SU, unsigned CurCycle) const;
bool operator()(SUnit* left, SUnit* right) const;
};
// ilp_ls_rr_sort - Priority function for ILP (instruction level parallelism)
// scheduler.
struct ilp_ls_rr_sort : public queue_sort {
enum {
IsBottomUp = true,
HasReadyFilter = false
};
RegReductionPQBase *SPQ;
ilp_ls_rr_sort(RegReductionPQBase *spq) : SPQ(spq) {}
bool isReady(SUnit *SU, unsigned CurCycle) const;
bool operator()(SUnit* left, SUnit* right) const;
};
class RegReductionPQBase : public SchedulingPriorityQueue {
protected:
std::vector<SUnit *> Queue;
unsigned CurQueueId = 0;
bool TracksRegPressure;
bool SrcOrder;
// SUnits - The SUnits for the current graph.
std::vector<SUnit> *SUnits;
MachineFunction &MF;
const TargetInstrInfo *TII;
const TargetRegisterInfo *TRI;
const TargetLowering *TLI;
ScheduleDAGRRList *scheduleDAG = nullptr;
// SethiUllmanNumbers - The SethiUllman number for each node.
std::vector<unsigned> SethiUllmanNumbers;
/// RegPressure - Tracking current reg pressure per register class.
std::vector<unsigned> RegPressure;
/// RegLimit - Tracking the number of allocatable registers per register
/// class.
std::vector<unsigned> RegLimit;
public:
RegReductionPQBase(MachineFunction &mf,
bool hasReadyFilter,
bool tracksrp,
bool srcorder,
const TargetInstrInfo *tii,
const TargetRegisterInfo *tri,
const TargetLowering *tli)
: SchedulingPriorityQueue(hasReadyFilter), TracksRegPressure(tracksrp),
SrcOrder(srcorder), MF(mf), TII(tii), TRI(tri), TLI(tli) {
if (TracksRegPressure) {
unsigned NumRC = TRI->getNumRegClasses();
RegLimit.resize(NumRC);
RegPressure.resize(NumRC);
std::fill(RegLimit.begin(), RegLimit.end(), 0);
std::fill(RegPressure.begin(), RegPressure.end(), 0);
for (const TargetRegisterClass *RC : TRI->regclasses())
RegLimit[RC->getID()] = tri->getRegPressureLimit(RC, MF);
}
}
void setScheduleDAG(ScheduleDAGRRList *scheduleDag) {
scheduleDAG = scheduleDag;
}
ScheduleHazardRecognizer* getHazardRec() {
return scheduleDAG->getHazardRec();
}
void initNodes(std::vector<SUnit> &sunits) override;
void addNode(const SUnit *SU) override;
void updateNode(const SUnit *SU) override;
void releaseState() override {
SUnits = nullptr;
SethiUllmanNumbers.clear();
std::fill(RegPressure.begin(), RegPressure.end(), 0);
}
unsigned getNodePriority(const SUnit *SU) const;
unsigned getNodeOrdering(const SUnit *SU) const {
if (!SU->getNode()) return 0;
return SU->getNode()->getIROrder();
}
bool empty() const override { return Queue.empty(); }
void push(SUnit *U) override {
assert(!U->NodeQueueId && "Node in the queue already");
U->NodeQueueId = ++CurQueueId;
Queue.push_back(U);
}
void remove(SUnit *SU) override {
assert(!Queue.empty() && "Queue is empty!");
assert(SU->NodeQueueId != 0 && "Not in queue!");
std::vector<SUnit *>::iterator I = llvm::find(Queue, SU);
if (I != std::prev(Queue.end()))
std::swap(*I, Queue.back());
Queue.pop_back();
SU->NodeQueueId = 0;
}
bool tracksRegPressure() const override { return TracksRegPressure; }
void dumpRegPressure() const;
bool HighRegPressure(const SUnit *SU) const;
bool MayReduceRegPressure(SUnit *SU) const;
int RegPressureDiff(SUnit *SU, unsigned &LiveUses) const;
void scheduledNode(SUnit *SU) override;
void unscheduledNode(SUnit *SU) override;
protected:
bool canClobber(const SUnit *SU, const SUnit *Op);
void AddPseudoTwoAddrDeps();
void PrescheduleNodesWithMultipleUses();
void CalculateSethiUllmanNumbers();
};
template<class SF>
static SUnit *popFromQueueImpl(std::vector<SUnit *> &Q, SF &Picker) {
std::vector<SUnit *>::iterator Best = Q.begin();
for (auto I = std::next(Q.begin()), E = Q.end(); I != E; ++I)
if (Picker(*Best, *I))
Best = I;
SUnit *V = *Best;
if (Best != std::prev(Q.end()))
std::swap(*Best, Q.back());
Q.pop_back();
return V;
}
template<class SF>
SUnit *popFromQueue(std::vector<SUnit *> &Q, SF &Picker, ScheduleDAG *DAG) {
#ifndef NDEBUG
if (DAG->StressSched) {
reverse_sort<SF> RPicker(Picker);
return popFromQueueImpl(Q, RPicker);
}
#endif
(void)DAG;
return popFromQueueImpl(Q, Picker);
}
//===----------------------------------------------------------------------===//
// RegReductionPriorityQueue Definition
//===----------------------------------------------------------------------===//
//
// This is a SchedulingPriorityQueue that schedules using Sethi Ullman numbers
// to reduce register pressure.
//
template<class SF>
class RegReductionPriorityQueue : public RegReductionPQBase {
SF Picker;
public:
RegReductionPriorityQueue(MachineFunction &mf,
bool tracksrp,
bool srcorder,
const TargetInstrInfo *tii,
const TargetRegisterInfo *tri,
const TargetLowering *tli)
: RegReductionPQBase(mf, SF::HasReadyFilter, tracksrp, srcorder,
tii, tri, tli),
Picker(this) {}
bool isBottomUp() const override { return SF::IsBottomUp; }
bool isReady(SUnit *U) const override {
return Picker.HasReadyFilter && Picker.isReady(U, getCurCycle());
}
SUnit *pop() override {
if (Queue.empty()) return nullptr;
SUnit *V = popFromQueue(Queue, Picker, scheduleDAG);
V->NodeQueueId = 0;
return V;
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void dump(ScheduleDAG *DAG) const override {
// Emulate pop() without clobbering NodeQueueIds.
std::vector<SUnit *> DumpQueue = Queue;
SF DumpPicker = Picker;
while (!DumpQueue.empty()) {
SUnit *SU = popFromQueue(DumpQueue, DumpPicker, scheduleDAG);
dbgs() << "Height " << SU->getHeight() << ": ";
DAG->dumpNode(*SU);
}
}
#endif
};
using BURegReductionPriorityQueue = RegReductionPriorityQueue<bu_ls_rr_sort>;
using SrcRegReductionPriorityQueue = RegReductionPriorityQueue<src_ls_rr_sort>;
using HybridBURRPriorityQueue = RegReductionPriorityQueue<hybrid_ls_rr_sort>;
using ILPBURRPriorityQueue = RegReductionPriorityQueue<ilp_ls_rr_sort>;
} // end anonymous namespace
//===----------------------------------------------------------------------===//
// Static Node Priority for Register Pressure Reduction
//===----------------------------------------------------------------------===//
// Check for special nodes that bypass scheduling heuristics.
// Currently this pushes TokenFactor nodes down, but may be used for other
// pseudo-ops as well.
//
// Return -1 to schedule right above left, 1 for left above right.
// Return 0 if no bias exists.
static int checkSpecialNodes(const SUnit *left, const SUnit *right) {
bool LSchedLow = left->isScheduleLow;
bool RSchedLow = right->isScheduleLow;
if (LSchedLow != RSchedLow)
return LSchedLow < RSchedLow ? 1 : -1;
return 0;
}
/// CalcNodeSethiUllmanNumber - Compute Sethi Ullman number.
/// Smaller number is the higher priority.
static unsigned
CalcNodeSethiUllmanNumber(const SUnit *SU, std::vector<unsigned> &SUNumbers) {
if (SUNumbers[SU->NodeNum] != 0)
return SUNumbers[SU->NodeNum];
// Use WorkList to avoid stack overflow on excessively large IRs.
struct WorkState {
WorkState(const SUnit *SU) : SU(SU) {}
const SUnit *SU;
unsigned PredsProcessed = 0;
};
SmallVector<WorkState, 16> WorkList;
WorkList.push_back(SU);
while (!WorkList.empty()) {
auto &Temp = WorkList.back();
auto *TempSU = Temp.SU;
bool AllPredsKnown = true;
// Try to find a non-evaluated pred and push it into the processing stack.
for (unsigned P = Temp.PredsProcessed; P < TempSU->Preds.size(); ++P) {
auto &Pred = TempSU->Preds[P];
if (Pred.isCtrl()) continue; // ignore chain preds
SUnit *PredSU = Pred.getSUnit();
if (SUNumbers[PredSU->NodeNum] == 0) {
#ifndef NDEBUG
// In debug mode, check that we don't have such element in the stack.
for (auto It : WorkList)
assert(It.SU != PredSU && "Trying to push an element twice?");
#endif
// Next time start processing this one starting from the next pred.
Temp.PredsProcessed = P + 1;
WorkList.push_back(PredSU);
AllPredsKnown = false;
break;
}
}
if (!AllPredsKnown)
continue;
// Once all preds are known, we can calculate the answer for this one.
unsigned SethiUllmanNumber = 0;
unsigned Extra = 0;
for (const SDep &Pred : TempSU->Preds) {
if (Pred.isCtrl()) continue; // ignore chain preds
SUnit *PredSU = Pred.getSUnit();
unsigned PredSethiUllman = SUNumbers[PredSU->NodeNum];
assert(PredSethiUllman > 0 && "We should have evaluated this pred!");
if (PredSethiUllman > SethiUllmanNumber) {
SethiUllmanNumber = PredSethiUllman;
Extra = 0;
} else if (PredSethiUllman == SethiUllmanNumber)
++Extra;
}
SethiUllmanNumber += Extra;
if (SethiUllmanNumber == 0)
SethiUllmanNumber = 1;
SUNumbers[TempSU->NodeNum] = SethiUllmanNumber;
WorkList.pop_back();
}
assert(SUNumbers[SU->NodeNum] > 0 && "SethiUllman should never be zero!");
return SUNumbers[SU->NodeNum];
}
/// CalculateSethiUllmanNumbers - Calculate Sethi-Ullman numbers of all
/// scheduling units.
void RegReductionPQBase::CalculateSethiUllmanNumbers() {
SethiUllmanNumbers.assign(SUnits->size(), 0);
for (const SUnit &SU : *SUnits)
CalcNodeSethiUllmanNumber(&SU, SethiUllmanNumbers);
}
void RegReductionPQBase::addNode(const SUnit *SU) {
unsigned SUSize = SethiUllmanNumbers.size();
if (SUnits->size() > SUSize)
SethiUllmanNumbers.resize(SUSize*2, 0);
CalcNodeSethiUllmanNumber(SU, SethiUllmanNumbers);
}
void RegReductionPQBase::updateNode(const SUnit *SU) {
SethiUllmanNumbers[SU->NodeNum] = 0;
CalcNodeSethiUllmanNumber(SU, SethiUllmanNumbers);
}
// Lower priority means schedule further down. For bottom-up scheduling, lower
// priority SUs are scheduled before higher priority SUs.
unsigned RegReductionPQBase::getNodePriority(const SUnit *SU) const {
assert(SU->NodeNum < SethiUllmanNumbers.size());
unsigned Opc = SU->getNode() ? SU->getNode()->getOpcode() : 0;
if (Opc == ISD::TokenFactor || Opc == ISD::CopyToReg)
// CopyToReg should be close to its uses to facilitate coalescing and
// avoid spilling.
return 0;
if (Opc == TargetOpcode::EXTRACT_SUBREG ||
Opc == TargetOpcode::SUBREG_TO_REG ||
Opc == TargetOpcode::INSERT_SUBREG)
// 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
// that would be consumed (e.g. store), then it terminates a chain of
// computation. Give it a large SethiUllman number so it will be
// scheduled right before its predecessors that it doesn't lengthen
// their live ranges.
return 0xffff;
if (SU->NumPreds == 0 && SU->NumSuccs != 0)
// If SU does not have a register def, schedule it close to its uses
// because it does not lengthen any live ranges.
return 0;
#if 1
return SethiUllmanNumbers[SU->NodeNum];
#else
unsigned Priority = SethiUllmanNumbers[SU->NodeNum];
if (SU->isCallOp) {
// FIXME: This assumes all of the defs are used as call operands.
int NP = (int)Priority - SU->getNode()->getNumValues();
return (NP > 0) ? NP : 0;
}
return Priority;
#endif
}
//===----------------------------------------------------------------------===//
// Register Pressure Tracking
//===----------------------------------------------------------------------===//
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void RegReductionPQBase::dumpRegPressure() const {
for (const TargetRegisterClass *RC : TRI->regclasses()) {
unsigned Id = RC->getID();
unsigned RP = RegPressure[Id];
if (!RP) continue;
LLVM_DEBUG(dbgs() << TRI->getRegClassName(RC) << ": " << RP << " / "
<< RegLimit[Id] << '\n');
}
}
#endif
bool RegReductionPQBase::HighRegPressure(const SUnit *SU) const {
if (!TLI)
return false;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl())
continue;
SUnit *PredSU = Pred.getSUnit();
// NumRegDefsLeft is zero when enough uses of this node have been scheduled
// to cover the number of registers defined (they are all live).
if (PredSU->NumRegDefsLeft == 0) {
continue;
}
for (ScheduleDAGSDNodes::RegDefIter RegDefPos(PredSU, scheduleDAG);
RegDefPos.IsValid(); RegDefPos.Advance()) {
unsigned RCId, Cost;
GetCostForDef(RegDefPos, TLI, TII, TRI, RCId, Cost, MF);
if ((RegPressure[RCId] + Cost) >= RegLimit[RCId])
return true;
}
}
return false;
}
bool RegReductionPQBase::MayReduceRegPressure(SUnit *SU) const {
const SDNode *N = SU->getNode();
if (!N->isMachineOpcode() || !SU->NumSuccs)
return false;
unsigned NumDefs = TII->get(N->getMachineOpcode()).getNumDefs();
for (unsigned i = 0; i != NumDefs; ++i) {
MVT VT = N->getSimpleValueType(i);
if (!N->hasAnyUseOfValue(i))
continue;
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
if (RegPressure[RCId] >= RegLimit[RCId])
return true;
}
return false;
}
// Compute the register pressure contribution by this instruction by count up
// for uses that are not live and down for defs. Only count register classes
// that are already under high pressure. As a side effect, compute the number of
// uses of registers that are already live.
//
// FIXME: This encompasses the logic in HighRegPressure and MayReduceRegPressure
// so could probably be factored.
int RegReductionPQBase::RegPressureDiff(SUnit *SU, unsigned &LiveUses) const {
LiveUses = 0;
int PDiff = 0;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl())
continue;
SUnit *PredSU = Pred.getSUnit();
// NumRegDefsLeft is zero when enough uses of this node have been scheduled
// to cover the number of registers defined (they are all live).
if (PredSU->NumRegDefsLeft == 0) {
if (PredSU->getNode()->isMachineOpcode())
++LiveUses;
continue;
}
for (ScheduleDAGSDNodes::RegDefIter RegDefPos(PredSU, scheduleDAG);
RegDefPos.IsValid(); RegDefPos.Advance()) {
MVT VT = RegDefPos.GetValue();
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
if (RegPressure[RCId] >= RegLimit[RCId])
++PDiff;
}
}
const SDNode *N = SU->getNode();
if (!N || !N->isMachineOpcode() || !SU->NumSuccs)
return PDiff;
unsigned NumDefs = TII->get(N->getMachineOpcode()).getNumDefs();
for (unsigned i = 0; i != NumDefs; ++i) {
MVT VT = N->getSimpleValueType(i);
if (!N->hasAnyUseOfValue(i))
continue;
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
if (RegPressure[RCId] >= RegLimit[RCId])
--PDiff;
}
return PDiff;
}
void RegReductionPQBase::scheduledNode(SUnit *SU) {
if (!TracksRegPressure)
return;
if (!SU->getNode())
return;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl())
continue;
SUnit *PredSU = Pred.getSUnit();
// NumRegDefsLeft is zero when enough uses of this node have been scheduled
// to cover the number of registers defined (they are all live).
if (PredSU->NumRegDefsLeft == 0) {
continue;
}
// FIXME: The ScheduleDAG currently loses information about which of a
// node's values is consumed by each dependence. Consequently, if the node
// defines multiple register classes, we don't know which to pressurize
// here. Instead the following loop consumes the register defs in an
// arbitrary order. At least it handles the common case of clustered loads
// to the same class. For precise liveness, each SDep needs to indicate the
// result number. But that tightly couples the ScheduleDAG with the
// SelectionDAG making updates tricky. A simpler hack would be to attach a
// value type or register class to SDep.
//
// The most important aspect of register tracking is balancing the increase
// here with the reduction further below. Note that this SU may use multiple
// defs in PredSU. The can't be determined here, but we've already
// compensated by reducing NumRegDefsLeft in PredSU during
// ScheduleDAGSDNodes::AddSchedEdges.
--PredSU->NumRegDefsLeft;
unsigned SkipRegDefs = PredSU->NumRegDefsLeft;
for (ScheduleDAGSDNodes::RegDefIter RegDefPos(PredSU, scheduleDAG);
RegDefPos.IsValid(); RegDefPos.Advance(), --SkipRegDefs) {
if (SkipRegDefs)
continue;
unsigned RCId, Cost;
GetCostForDef(RegDefPos, TLI, TII, TRI, RCId, Cost, MF);
RegPressure[RCId] += Cost;
break;
}
}
// We should have this assert, but there may be dead SDNodes that never
// materialize as SUnits, so they don't appear to generate liveness.
//assert(SU->NumRegDefsLeft == 0 && "not all regdefs have scheduled uses");
int SkipRegDefs = (int)SU->NumRegDefsLeft;
for (ScheduleDAGSDNodes::RegDefIter RegDefPos(SU, scheduleDAG);
RegDefPos.IsValid(); RegDefPos.Advance(), --SkipRegDefs) {
if (SkipRegDefs > 0)
continue;
unsigned RCId, Cost;
GetCostForDef(RegDefPos, TLI, TII, TRI, RCId, Cost, MF);
if (RegPressure[RCId] < Cost) {
// Register pressure tracking is imprecise. This can happen. But we try
// hard not to let it happen because it likely results in poor scheduling.
LLVM_DEBUG(dbgs() << " SU(" << SU->NodeNum
<< ") has too many regdefs\n");
RegPressure[RCId] = 0;
}
else {
RegPressure[RCId] -= Cost;
}
}
LLVM_DEBUG(dumpRegPressure());
}
void RegReductionPQBase::unscheduledNode(SUnit *SU) {
if (!TracksRegPressure)
return;
const SDNode *N = SU->getNode();
if (!N) return;
if (!N->isMachineOpcode()) {
if (N->getOpcode() != ISD::CopyToReg)
return;
} else {
unsigned Opc = N->getMachineOpcode();
if (Opc == TargetOpcode::EXTRACT_SUBREG ||
Opc == TargetOpcode::INSERT_SUBREG ||
Opc == TargetOpcode::SUBREG_TO_REG ||
Opc == TargetOpcode::REG_SEQUENCE ||
Opc == TargetOpcode::IMPLICIT_DEF)
return;
}
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl())
continue;
SUnit *PredSU = Pred.getSUnit();
// NumSuccsLeft counts all deps. Don't compare it with NumSuccs which only
// counts data deps.
if (PredSU->NumSuccsLeft != PredSU->Succs.size())
continue;
const SDNode *PN = PredSU->getNode();
if (!PN->isMachineOpcode()) {
if (PN->getOpcode() == ISD::CopyFromReg) {
MVT VT = PN->getSimpleValueType(0);
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
RegPressure[RCId] += TLI->getRepRegClassCostFor(VT);
}
continue;
}
unsigned POpc = PN->getMachineOpcode();
if (POpc == TargetOpcode::IMPLICIT_DEF)
continue;
if (POpc == TargetOpcode::EXTRACT_SUBREG ||
POpc == TargetOpcode::INSERT_SUBREG ||
POpc == TargetOpcode::SUBREG_TO_REG) {
MVT VT = PN->getSimpleValueType(0);
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
RegPressure[RCId] += TLI->getRepRegClassCostFor(VT);
continue;
}
unsigned NumDefs = TII->get(PN->getMachineOpcode()).getNumDefs();
for (unsigned i = 0; i != NumDefs; ++i) {
MVT VT = PN->getSimpleValueType(i);
if (!PN->hasAnyUseOfValue(i))
continue;
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
if (RegPressure[RCId] < TLI->getRepRegClassCostFor(VT))
// Register pressure tracking is imprecise. This can happen.
RegPressure[RCId] = 0;
else
RegPressure[RCId] -= TLI->getRepRegClassCostFor(VT);
}
}
// Check for isMachineOpcode() as PrescheduleNodesWithMultipleUses()
// may transfer data dependencies to CopyToReg.
if (SU->NumSuccs && N->isMachineOpcode()) {
unsigned NumDefs = TII->get(N->getMachineOpcode()).getNumDefs();
for (unsigned i = NumDefs, e = N->getNumValues(); i != e; ++i) {
MVT VT = N->getSimpleValueType(i);
if (VT == MVT::Glue || VT == MVT::Other)
continue;
if (!N->hasAnyUseOfValue(i))
continue;
unsigned RCId = TLI->getRepRegClassFor(VT)->getID();
RegPressure[RCId] += TLI->getRepRegClassCostFor(VT);
}
}
LLVM_DEBUG(dumpRegPressure());
}
//===----------------------------------------------------------------------===//
// Dynamic Node Priority for Register Pressure Reduction
//===----------------------------------------------------------------------===//
/// closestSucc - Returns the scheduled cycle of the successor which is
/// closest to the current cycle.
static unsigned closestSucc(const SUnit *SU) {
unsigned MaxHeight = 0;
for (const SDep &Succ : SU->Succs) {
if (Succ.isCtrl()) continue; // ignore chain succs
unsigned Height = Succ.getSUnit()->getHeight();
// If there are bunch of CopyToRegs stacked up, they should be considered
// to be at the same position.
if (Succ.getSUnit()->getNode() &&
Succ.getSUnit()->getNode()->getOpcode() == ISD::CopyToReg)
Height = closestSucc(Succ.getSUnit())+1;
if (Height > MaxHeight)
MaxHeight = Height;
}
return MaxHeight;
}
/// calcMaxScratches - Returns an cost estimate of the worse case requirement
/// for scratch registers, i.e. number of data dependencies.
static unsigned calcMaxScratches(const SUnit *SU) {
unsigned Scratches = 0;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl()) continue; // ignore chain preds
Scratches++;
}
return Scratches;
}
/// hasOnlyLiveInOpers - Return true if SU has only value predecessors that are
/// CopyFromReg from a virtual register.
static bool hasOnlyLiveInOpers(const SUnit *SU) {
bool RetVal = false;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl()) continue;
const SUnit *PredSU = Pred.getSUnit();
if (PredSU->getNode() &&
PredSU->getNode()->getOpcode() == ISD::CopyFromReg) {
unsigned Reg =
cast<RegisterSDNode>(PredSU->getNode()->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
RetVal = true;
continue;
}
}
return false;
}
return RetVal;
}
/// hasOnlyLiveOutUses - Return true if SU has only value successors that are
/// CopyToReg to a virtual register. This SU def is probably a liveout and
/// it has no other use. It should be scheduled closer to the terminator.
static bool hasOnlyLiveOutUses(const SUnit *SU) {
bool RetVal = false;
for (const SDep &Succ : SU->Succs) {
if (Succ.isCtrl()) continue;
const SUnit *SuccSU = Succ.getSUnit();
if (SuccSU->getNode() && SuccSU->getNode()->getOpcode() == ISD::CopyToReg) {
unsigned Reg =
cast<RegisterSDNode>(SuccSU->getNode()->getOperand(1))->getReg();
if (TargetRegisterInfo::isVirtualRegister(Reg)) {
RetVal = true;
continue;
}
}
return false;
}
return RetVal;
}
// Set isVRegCycle for a node with only live in opers and live out uses. Also
// set isVRegCycle for its CopyFromReg operands.
//
// This is only relevant for single-block loops, in which case the VRegCycle
// node is likely an induction variable in which the operand and target virtual
// registers should be coalesced (e.g. pre/post increment values). Setting the
// isVRegCycle flag helps the scheduler prioritize other uses of the same
// CopyFromReg so that this node becomes the virtual register "kill". This
// avoids interference between the values live in and out of the block and
// eliminates a copy inside the loop.
static void initVRegCycle(SUnit *SU) {
if (DisableSchedVRegCycle)
return;
if (!hasOnlyLiveInOpers(SU) || !hasOnlyLiveOutUses(SU))
return;
LLVM_DEBUG(dbgs() << "VRegCycle: SU(" << SU->NodeNum << ")\n");
SU->isVRegCycle = true;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl()) continue;
Pred.getSUnit()->isVRegCycle = true;
}
}
// After scheduling the definition of a VRegCycle, clear the isVRegCycle flag of
// CopyFromReg operands. We should no longer penalize other uses of this VReg.
static void resetVRegCycle(SUnit *SU) {
if (!SU->isVRegCycle)
return;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl()) continue; // ignore chain preds
SUnit *PredSU = Pred.getSUnit();
if (PredSU->isVRegCycle) {
assert(PredSU->getNode()->getOpcode() == ISD::CopyFromReg &&
"VRegCycle def must be CopyFromReg");
Pred.getSUnit()->isVRegCycle = false;
}
}
}
// Return true if this SUnit uses a CopyFromReg node marked as a VRegCycle. This
// means a node that defines the VRegCycle has not been scheduled yet.
static bool hasVRegCycleUse(const SUnit *SU) {
// If this SU also defines the VReg, don't hoist it as a "use".
if (SU->isVRegCycle)
return false;
for (const SDep &Pred : SU->Preds) {
if (Pred.isCtrl()) continue; // ignore chain preds
if (Pred.getSUnit()->isVRegCycle &&
Pred.getSUnit()->getNode()->getOpcode() == ISD::CopyFromReg) {
LLVM_DEBUG(dbgs() << " VReg cycle use: SU (" << SU->NodeNum << ")\n");
return true;
}
}
return false;
}
// Check for either a dependence (latency) or resource (hazard) stall.
//
// Note: The ScheduleHazardRecognizer interface requires a non-const SU.
static bool BUHasStall(SUnit *SU, int Height, RegReductionPQBase *SPQ) {
if ((int)SPQ->getCurCycle() < Height) return true;
if (SPQ->getHazardRec()->getHazardType(SU, 0)
!= ScheduleHazardRecognizer::NoHazard)
return true;
return false;
}
// Return -1 if left has higher priority, 1 if right has higher priority.
// Return 0 if latency-based priority is equivalent.
static int BUCompareLatency(SUnit *left, SUnit *right, bool checkPref,
RegReductionPQBase *SPQ) {
// Scheduling an instruction that uses a VReg whose postincrement has not yet
// been scheduled will induce a copy. Model this as an extra cycle of latency.
int LPenalty = hasVRegCycleUse(left) ? 1 : 0;
int RPenalty = hasVRegCycleUse(right) ? 1 : 0;
int LHeight = (int)left->getHeight() + LPenalty;
int RHeight = (int)right->getHeight() + RPenalty;
bool LStall = (!checkPref || left->SchedulingPref == Sched::ILP) &&
BUHasStall(left, LHeight, SPQ);
bool RStall = (!checkPref || right->SchedulingPref == Sched::ILP) &&
BUHasStall(right, RHeight, SPQ);
// If scheduling one of the node will cause a pipeline stall, delay it.
// If scheduling either one of the node will cause a pipeline stall, sort
// them according to their height.
if (LStall) {
if (!RStall)
return 1;
if (LHeight != RHeight)
return LHeight > RHeight ? 1 : -1;
} else if (RStall)
return -1;
// If either node is scheduling for latency, sort them by height/depth
// and latency.
if (!checkPref || (left->SchedulingPref == Sched::ILP ||
right->SchedulingPref == Sched::ILP)) {
// If neither instruction stalls (!LStall && !RStall) and HazardRecognizer
// is enabled, grouping instructions by cycle, then its height is already
// covered so only its depth matters. We also reach this point if both stall
// but have the same height.
if (!SPQ->getHazardRec()->isEnabled()) {
if (LHeight != RHeight)
return LHeight > RHeight ? 1 : -1;
}