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+//===---- ScheduleDAGInstrs.cpp - MachineInstr Rescheduling ---------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file This implements the ScheduleDAGInstrs class, which implements
+/// re-scheduling of MachineInstrs.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/ScheduleDAGInstrs.h"
+#include "llvm/ADT/IntEqClasses.h"
+#include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SparseSet.h"
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/CodeGen/LiveIntervals.h"
+#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBundle.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/PseudoSourceValue.h"
+#include "llvm/CodeGen/RegisterPressure.h"
+#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/ScheduleDFS.h"
+#include "llvm/CodeGen/SlotIndexes.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/CodeGen/TargetSubtargetInfo.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/Instruction.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/Type.h"
+#include "llvm/IR/Value.h"
+#include "llvm/MC/LaneBitmask.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <iterator>
+#include <string>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "machine-scheduler"
+
+static cl::opt<bool> EnableAASchedMI("enable-aa-sched-mi", cl::Hidden,
+ cl::ZeroOrMore, cl::init(false),
+ cl::desc("Enable use of AA during MI DAG construction"));
+
+static cl::opt<bool> UseTBAA("use-tbaa-in-sched-mi", cl::Hidden,
+ cl::init(true), cl::desc("Enable use of TBAA during MI DAG construction"));
+
+// Note: the two options below might be used in tuning compile time vs
+// output quality. Setting HugeRegion so large that it will never be
+// reached means best-effort, but may be slow.
+
+// When Stores and Loads maps (or NonAliasStores and NonAliasLoads)
+// together hold this many SUs, a reduction of maps will be done.
+static cl::opt<unsigned> HugeRegion("dag-maps-huge-region", cl::Hidden,
+ cl::init(1000), cl::desc("The limit to use while constructing the DAG "
+ "prior to scheduling, at which point a trade-off "
+ "is made to avoid excessive compile time."));
+
+static cl::opt<unsigned> ReductionSize(
+ "dag-maps-reduction-size", cl::Hidden,
+ cl::desc("A huge scheduling region will have maps reduced by this many "
+ "nodes at a time. Defaults to HugeRegion / 2."));
+
+static unsigned getReductionSize() {
+ // Always reduce a huge region with half of the elements, except
+ // when user sets this number explicitly.
+ if (ReductionSize.getNumOccurrences() == 0)
+ return HugeRegion / 2;
+ return ReductionSize;
+}
+
+static void dumpSUList(ScheduleDAGInstrs::SUList &L) {
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+ dbgs() << "{ ";
+ for (const SUnit *su : L) {
+ dbgs() << "SU(" << su->NodeNum << ")";
+ if (su != L.back())
+ dbgs() << ", ";
+ }
+ dbgs() << "}\n";
+#endif
+}
+
+ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
+ const MachineLoopInfo *mli,
+ bool RemoveKillFlags)
+ : ScheduleDAG(mf), MLI(mli), MFI(mf.getFrameInfo()),
+ RemoveKillFlags(RemoveKillFlags),
+ UnknownValue(UndefValue::get(
+ Type::getVoidTy(mf.getFunction().getContext()))), Topo(SUnits, &ExitSU) {
+ DbgValues.clear();
+
+ const TargetSubtargetInfo &ST = mf.getSubtarget();
+ SchedModel.init(&ST);
+}
+
+/// If this machine instr has memory reference information and it can be
+/// tracked to a normal reference to a known object, return the Value
+/// for that object. This function returns false the memory location is
+/// unknown or may alias anything.
+static bool getUnderlyingObjectsForInstr(const MachineInstr *MI,
+ const MachineFrameInfo &MFI,
+ UnderlyingObjectsVector &Objects,
+ const DataLayout &DL) {
+ auto allMMOsOkay = [&]() {
+ for (const MachineMemOperand *MMO : MI->memoperands()) {
+ // TODO: Figure out whether isAtomic is really necessary (see D57601).
+ if (MMO->isVolatile() || MMO->isAtomic())
+ return false;
+
+ if (const PseudoSourceValue *PSV = MMO->getPseudoValue()) {
+ // Function that contain tail calls don't have unique PseudoSourceValue
+ // objects. Two PseudoSourceValues might refer to the same or
+ // overlapping locations. The client code calling this function assumes
+ // this is not the case. So return a conservative answer of no known
+ // object.
+ if (MFI.hasTailCall())
+ return false;
+
+ // For now, ignore PseudoSourceValues which may alias LLVM IR values
+ // because the code that uses this function has no way to cope with
+ // such aliases.
+ if (PSV->isAliased(&MFI))
+ return false;
+
+ bool MayAlias = PSV->mayAlias(&MFI);
+ Objects.push_back(UnderlyingObjectsVector::value_type(PSV, MayAlias));
+ } else if (const Value *V = MMO->getValue()) {
+ SmallVector<Value *, 4> Objs;
+ if (!getUnderlyingObjectsForCodeGen(V, Objs, DL))
+ return false;
+
+ for (Value *V : Objs) {
+ assert(isIdentifiedObject(V));
+ Objects.push_back(UnderlyingObjectsVector::value_type(V, true));
+ }
+ } else
+ return false;
+ }
+ return true;
+ };
+
+ if (!allMMOsOkay()) {
+ Objects.clear();
+ return false;
+ }
+
+ return true;
+}
+
+void ScheduleDAGInstrs::startBlock(MachineBasicBlock *bb) {
+ BB = bb;
+}
+
+void ScheduleDAGInstrs::finishBlock() {
+ // Subclasses should no longer refer to the old block.
+ BB = nullptr;
+}
+
+void ScheduleDAGInstrs::enterRegion(MachineBasicBlock *bb,
+ MachineBasicBlock::iterator begin,
+ MachineBasicBlock::iterator end,
+ unsigned regioninstrs) {
+ assert(bb == BB && "startBlock should set BB");
+ RegionBegin = begin;
+ RegionEnd = end;
+ NumRegionInstrs = regioninstrs;
+}
+
+void ScheduleDAGInstrs::exitRegion() {
+ // Nothing to do.
+}
+
+void ScheduleDAGInstrs::addSchedBarrierDeps() {
+ MachineInstr *ExitMI = RegionEnd != BB->end() ? &*RegionEnd : nullptr;
+ ExitSU.setInstr(ExitMI);
+ // Add dependencies on the defs and uses of the instruction.
+ if (ExitMI) {
+ for (const MachineOperand &MO : ExitMI->operands()) {
+ if (!MO.isReg() || MO.isDef()) continue;
+ Register Reg = MO.getReg();
+ if (Register::isPhysicalRegister(Reg)) {
+ Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
+ } else if (Register::isVirtualRegister(Reg) && MO.readsReg()) {
+ addVRegUseDeps(&ExitSU, ExitMI->getOperandNo(&MO));
+ }
+ }
+ }
+ if (!ExitMI || (!ExitMI->isCall() && !ExitMI->isBarrier())) {
+ // For others, e.g. fallthrough, conditional branch, assume the exit
+ // uses all the registers that are livein to the successor blocks.
+ for (const MachineBasicBlock *Succ : BB->successors()) {
+ for (const auto &LI : Succ->liveins()) {
+ if (!Uses.contains(LI.PhysReg))
+ Uses.insert(PhysRegSUOper(&ExitSU, -1, LI.PhysReg));
+ }
+ }
+ }
+}
+
+/// MO is an operand of SU's instruction that defines a physical register. Adds
+/// data dependencies from SU to any uses of the physical register.
+void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU, unsigned OperIdx) {
+ const MachineOperand &MO = SU->getInstr()->getOperand(OperIdx);
+ assert(MO.isDef() && "expect physreg def");
+
+ // Ask the target if address-backscheduling is desirable, and if so how much.
+ const TargetSubtargetInfo &ST = MF.getSubtarget();
+
+ // Only use any non-zero latency for real defs/uses, in contrast to
+ // "fake" operands added by regalloc.
+ const MCInstrDesc *DefMIDesc = &SU->getInstr()->getDesc();
+ bool ImplicitPseudoDef = (OperIdx >= DefMIDesc->getNumOperands() &&
+ !DefMIDesc->hasImplicitDefOfPhysReg(MO.getReg()));
+ for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
+ Alias.isValid(); ++Alias) {
+ if (!Uses.contains(*Alias))
+ continue;
+ for (Reg2SUnitsMap::iterator I = Uses.find(*Alias); I != Uses.end(); ++I) {
+ SUnit *UseSU = I->SU;
+ if (UseSU == SU)
+ continue;
+
+ // Adjust the dependence latency using operand def/use information,
+ // then allow the target to perform its own adjustments.
+ int UseOp = I->OpIdx;
+ MachineInstr *RegUse = nullptr;
+ SDep Dep;
+ if (UseOp < 0)
+ Dep = SDep(SU, SDep::Artificial);
+ else {
+ // Set the hasPhysRegDefs only for physreg defs that have a use within
+ // the scheduling region.
+ SU->hasPhysRegDefs = true;
+ Dep = SDep(SU, SDep::Data, *Alias);
+ RegUse = UseSU->getInstr();
+ }
+ const MCInstrDesc *UseMIDesc =
+ (RegUse ? &UseSU->getInstr()->getDesc() : nullptr);
+ bool ImplicitPseudoUse =
+ (UseMIDesc && UseOp >= ((int)UseMIDesc->getNumOperands()) &&
+ !UseMIDesc->hasImplicitUseOfPhysReg(*Alias));
+ if (!ImplicitPseudoDef && !ImplicitPseudoUse) {
+ Dep.setLatency(SchedModel.computeOperandLatency(SU->getInstr(), OperIdx,
+ RegUse, UseOp));
+ ST.adjustSchedDependency(SU, UseSU, Dep);
+ } else
+ Dep.setLatency(0);
+
+ UseSU->addPred(Dep);
+ }
+ }
+}
+
+/// Adds register dependencies (data, anti, and output) from this SUnit
+/// to following instructions in the same scheduling region that depend the
+/// physical register referenced at OperIdx.
+void ScheduleDAGInstrs::addPhysRegDeps(SUnit *SU, unsigned OperIdx) {
+ MachineInstr *MI = SU->getInstr();
+ MachineOperand &MO = MI->getOperand(OperIdx);
+ Register Reg = MO.getReg();
+ // We do not need to track any dependencies for constant registers.
+ if (MRI.isConstantPhysReg(Reg))
+ return;
+
+ // Optionally add output and anti dependencies. For anti
+ // dependencies we use a latency of 0 because for a multi-issue
+ // target we want to allow the defining instruction to issue
+ // in the same cycle as the using instruction.
+ // TODO: Using a latency of 1 here for output dependencies assumes
+ // there's no cost for reusing registers.
+ SDep::Kind Kind = MO.isUse() ? SDep::Anti : SDep::Output;
+ for (MCRegAliasIterator Alias(Reg, TRI, true); Alias.isValid(); ++Alias) {
+ if (!Defs.contains(*Alias))
+ continue;
+ for (Reg2SUnitsMap::iterator I = Defs.find(*Alias); I != Defs.end(); ++I) {
+ SUnit *DefSU = I->SU;
+ if (DefSU == &ExitSU)
+ continue;
+ if (DefSU != SU &&
+ (Kind != SDep::Output || !MO.isDead() ||
+ !DefSU->getInstr()->registerDefIsDead(*Alias))) {
+ if (Kind == SDep::Anti)
+ DefSU->addPred(SDep(SU, Kind, /*Reg=*/*Alias));
+ else {
+ SDep Dep(SU, Kind, /*Reg=*/*Alias);
+ Dep.setLatency(
+ SchedModel.computeOutputLatency(MI, OperIdx, DefSU->getInstr()));
+ DefSU->addPred(Dep);
+ }
+ }
+ }
+ }
+
+ if (!MO.isDef()) {
+ SU->hasPhysRegUses = true;
+ // Either insert a new Reg2SUnits entry with an empty SUnits list, or
+ // retrieve the existing SUnits list for this register's uses.
+ // Push this SUnit on the use list.
+ Uses.insert(PhysRegSUOper(SU, OperIdx, Reg));
+ if (RemoveKillFlags)
+ MO.setIsKill(false);
+ } else {
+ addPhysRegDataDeps(SU, OperIdx);
+
+ // Clear previous uses and defs of this register and its subergisters.
+ for (MCSubRegIterator SubReg(Reg, TRI, true); SubReg.isValid(); ++SubReg) {
+ if (Uses.contains(*SubReg))
+ Uses.eraseAll(*SubReg);
+ if (!MO.isDead())
+ Defs.eraseAll(*SubReg);
+ }
+ if (MO.isDead() && SU->isCall) {
+ // Calls will not be reordered because of chain dependencies (see
+ // below). Since call operands are dead, calls may continue to be added
+ // to the DefList making dependence checking quadratic in the size of
+ // the block. Instead, we leave only one call at the back of the
+ // DefList.
+ Reg2SUnitsMap::RangePair P = Defs.equal_range(Reg);
+ Reg2SUnitsMap::iterator B = P.first;
+ Reg2SUnitsMap::iterator I = P.second;
+ for (bool isBegin = I == B; !isBegin; /* empty */) {
+ isBegin = (--I) == B;
+ if (!I->SU->isCall)
+ break;
+ I = Defs.erase(I);
+ }
+ }
+
+ // Defs are pushed in the order they are visited and never reordered.
+ Defs.insert(PhysRegSUOper(SU, OperIdx, Reg));
+ }
+}
+
+LaneBitmask ScheduleDAGInstrs::getLaneMaskForMO(const MachineOperand &MO) const
+{
+ Register Reg = MO.getReg();
+ // No point in tracking lanemasks if we don't have interesting subregisters.
+ const TargetRegisterClass &RC = *MRI.getRegClass(Reg);
+ if (!RC.HasDisjunctSubRegs)
+ return LaneBitmask::getAll();
+
+ unsigned SubReg = MO.getSubReg();
+ if (SubReg == 0)
+ return RC.getLaneMask();
+ return TRI->getSubRegIndexLaneMask(SubReg);
+}
+
+bool ScheduleDAGInstrs::deadDefHasNoUse(const MachineOperand &MO) {
+ auto RegUse = CurrentVRegUses.find(MO.getReg());
+ if (RegUse == CurrentVRegUses.end())
+ return true;
+ return (RegUse->LaneMask & getLaneMaskForMO(MO)).none();
+}
+
+/// Adds register output and data dependencies from this SUnit to instructions
+/// that occur later in the same scheduling region if they read from or write to
+/// the virtual register defined at OperIdx.
+///
+/// TODO: Hoist loop induction variable increments. This has to be
+/// reevaluated. Generally, IV scheduling should be done before coalescing.
+void ScheduleDAGInstrs::addVRegDefDeps(SUnit *SU, unsigned OperIdx) {
+ MachineInstr *MI = SU->getInstr();
+ MachineOperand &MO = MI->getOperand(OperIdx);
+ Register Reg = MO.getReg();
+
+ LaneBitmask DefLaneMask;
+ LaneBitmask KillLaneMask;
+ if (TrackLaneMasks) {
+ bool IsKill = MO.getSubReg() == 0 || MO.isUndef();
+ DefLaneMask = getLaneMaskForMO(MO);
+ // If we have a <read-undef> flag, none of the lane values comes from an
+ // earlier instruction.
+ KillLaneMask = IsKill ? LaneBitmask::getAll() : DefLaneMask;
+
+ if (MO.getSubReg() != 0 && MO.isUndef()) {
+ // There may be other subregister defs on the same instruction of the same
+ // register in later operands. The lanes of other defs will now be live
+ // after this instruction, so these should not be treated as killed by the
+ // instruction even though they appear to be killed in this one operand.
+ for (int I = OperIdx + 1, E = MI->getNumOperands(); I != E; ++I) {
+ const MachineOperand &OtherMO = MI->getOperand(I);
+ if (OtherMO.isReg() && OtherMO.isDef() && OtherMO.getReg() == Reg)
+ KillLaneMask &= ~getLaneMaskForMO(OtherMO);
+ }
+ }
+
+ // Clear undef flag, we'll re-add it later once we know which subregister
+ // Def is first.
+ MO.setIsUndef(false);
+ } else {
+ DefLaneMask = LaneBitmask::getAll();
+ KillLaneMask = LaneBitmask::getAll();
+ }
+
+ if (MO.isDead()) {
+ assert(deadDefHasNoUse(MO) && "Dead defs should have no uses");
+ } else {
+ // Add data dependence to all uses we found so far.
+ const TargetSubtargetInfo &ST = MF.getSubtarget();
+ for (VReg2SUnitOperIdxMultiMap::iterator I = CurrentVRegUses.find(Reg),
+ E = CurrentVRegUses.end(); I != E; /*empty*/) {
+ LaneBitmask LaneMask = I->LaneMask;
+ // Ignore uses of other lanes.
+ if ((LaneMask & KillLaneMask).none()) {
+ ++I;
+ continue;
+ }
+
+ if ((LaneMask & DefLaneMask).any()) {
+ SUnit *UseSU = I->SU;
+ MachineInstr *Use = UseSU->getInstr();
+ SDep Dep(SU, SDep::Data, Reg);
+ Dep.setLatency(SchedModel.computeOperandLatency(MI, OperIdx, Use,
+ I->OperandIndex));
+ ST.adjustSchedDependency(SU, UseSU, Dep);
+ UseSU->addPred(Dep);
+ }
+
+ LaneMask &= ~KillLaneMask;
+ // If we found a Def for all lanes of this use, remove it from the list.
+ if (LaneMask.any()) {
+ I->LaneMask = LaneMask;
+ ++I;
+ } else
+ I = CurrentVRegUses.erase(I);
+ }
+ }
+
+ // Shortcut: Singly defined vregs do not have output/anti dependencies.
+ if (MRI.hasOneDef(Reg))
+ return;
+
+ // Add output dependence to the next nearest defs of this vreg.
+ //
+ // Unless this definition is dead, the output dependence should be
+ // transitively redundant with antidependencies from this definition's
+ // uses. We're conservative for now until we have a way to guarantee the uses
+ // are not eliminated sometime during scheduling. The output dependence edge
+ // is also useful if output latency exceeds def-use latency.
+ LaneBitmask LaneMask = DefLaneMask;
+ for (VReg2SUnit &V2SU : make_range(CurrentVRegDefs.find(Reg),
+ CurrentVRegDefs.end())) {
+ // Ignore defs for other lanes.
+ if ((V2SU.LaneMask & LaneMask).none())
+ continue;
+ // Add an output dependence.
+ SUnit *DefSU = V2SU.SU;
+ // Ignore additional defs of the same lanes in one instruction. This can
+ // happen because lanemasks are shared for targets with too many
+ // subregisters. We also use some representration tricks/hacks where we
+ // add super-register defs/uses, to imply that although we only access parts
+ // of the reg we care about the full one.
+ if (DefSU == SU)
+ continue;
+ SDep Dep(SU, SDep::Output, Reg);
+ Dep.setLatency(
+ SchedModel.computeOutputLatency(MI, OperIdx, DefSU->getInstr()));
+ DefSU->addPred(Dep);
+
+ // Update current definition. This can get tricky if the def was about a
+ // bigger lanemask before. We then have to shrink it and create a new
+ // VReg2SUnit for the non-overlapping part.
+ LaneBitmask OverlapMask = V2SU.LaneMask & LaneMask;
+ LaneBitmask NonOverlapMask = V2SU.LaneMask & ~LaneMask;
+ V2SU.SU = SU;
+ V2SU.LaneMask = OverlapMask;
+ if (NonOverlapMask.any())
+ CurrentVRegDefs.insert(VReg2SUnit(Reg, NonOverlapMask, DefSU));
+ }
+ // If there was no CurrentVRegDefs entry for some lanes yet, create one.
+ if (LaneMask.any())
+ CurrentVRegDefs.insert(VReg2SUnit(Reg, LaneMask, SU));
+}
+
+/// Adds a register data dependency if the instruction that defines the
+/// virtual register used at OperIdx is mapped to an SUnit. Add a register
+/// antidependency from this SUnit to instructions that occur later in the same
+/// scheduling region if they write the virtual register.
+///
+/// TODO: Handle ExitSU "uses" properly.
+void ScheduleDAGInstrs::addVRegUseDeps(SUnit *SU, unsigned OperIdx) {
+ const MachineInstr *MI = SU->getInstr();
+ const MachineOperand &MO = MI->getOperand(OperIdx);
+ Register Reg = MO.getReg();
+
+ // Remember the use. Data dependencies will be added when we find the def.
+ LaneBitmask LaneMask = TrackLaneMasks ? getLaneMaskForMO(MO)
+ : LaneBitmask::getAll();
+ CurrentVRegUses.insert(VReg2SUnitOperIdx(Reg, LaneMask, OperIdx, SU));
+
+ // Add antidependences to the following defs of the vreg.
+ for (VReg2SUnit &V2SU : make_range(CurrentVRegDefs.find(Reg),
+ CurrentVRegDefs.end())) {
+ // Ignore defs for unrelated lanes.
+ LaneBitmask PrevDefLaneMask = V2SU.LaneMask;
+ if ((PrevDefLaneMask & LaneMask).none())
+ continue;
+ if (V2SU.SU == SU)
+ continue;
+
+ V2SU.SU->addPred(SDep(SU, SDep::Anti, Reg));
+ }
+}
+
+/// Returns true if MI is an instruction we are unable to reason about
+/// (like a call or something with unmodeled side effects).
+static inline bool isGlobalMemoryObject(AAResults *AA, MachineInstr *MI) {
+ return MI->isCall() || MI->hasUnmodeledSideEffects() ||
+ (MI->hasOrderedMemoryRef() && !MI->isDereferenceableInvariantLoad(AA));
+}
+
+void ScheduleDAGInstrs::addChainDependency (SUnit *SUa, SUnit *SUb,
+ unsigned Latency) {
+ if (SUa->getInstr()->mayAlias(AAForDep, *SUb->getInstr(), UseTBAA)) {
+ SDep Dep(SUa, SDep::MayAliasMem);
+ Dep.setLatency(Latency);
+ SUb->addPred(Dep);
+ }
+}
+
+/// Creates an SUnit for each real instruction, numbered in top-down
+/// topological order. The instruction order A < B, implies that no edge exists
+/// from B to A.
+///
+/// Map each real instruction to its SUnit.
+///
+/// After initSUnits, the SUnits vector cannot be resized and the scheduler may
+/// hang onto SUnit pointers. We may relax this in the future by using SUnit IDs
+/// instead of pointers.
+///
+/// MachineScheduler relies on initSUnits numbering the nodes by their order in
+/// the original instruction list.
+void ScheduleDAGInstrs::initSUnits() {
+ // We'll be allocating one SUnit for each real instruction in the region,
+ // which is contained within a basic block.
+ SUnits.reserve(NumRegionInstrs);
+
+ for (MachineInstr &MI : make_range(RegionBegin, RegionEnd)) {
+ if (MI.isDebugInstr())
+ continue;
+
+ SUnit *SU = newSUnit(&MI);
+ MISUnitMap[&MI] = SU;
+
+ SU->isCall = MI.isCall();
+ SU->isCommutable = MI.isCommutable();
+
+ // Assign the Latency field of SU using target-provided information.
+ SU->Latency = SchedModel.computeInstrLatency(SU->getInstr());
+
+ // If this SUnit uses a reserved or unbuffered resource, mark it as such.
+ //
+ // Reserved resources block an instruction from issuing and stall the
+ // entire pipeline. These are identified by BufferSize=0.
+ //
+ // Unbuffered resources prevent execution of subsequent instructions that
+ // require the same resources. This is used for in-order execution pipelines
+ // within an out-of-order core. These are identified by BufferSize=1.
+ if (SchedModel.hasInstrSchedModel()) {
+ const MCSchedClassDesc *SC = getSchedClass(SU);
+ for (const MCWriteProcResEntry &PRE :
+ make_range(SchedModel.getWriteProcResBegin(SC),
+ SchedModel.getWriteProcResEnd(SC))) {
+ switch (SchedModel.getProcResource(PRE.ProcResourceIdx)->BufferSize) {
+ case 0:
+ SU->hasReservedResource = true;
+ break;
+ case 1:
+ SU->isUnbuffered = true;
+ break;
+ default:
+ break;
+ }
+ }
+ }
+ }
+}
+
+class ScheduleDAGInstrs::Value2SUsMap : public MapVector<ValueType, SUList> {
+ /// Current total number of SUs in map.
+ unsigned NumNodes = 0;
+
+ /// 1 for loads, 0 for stores. (see comment in SUList)
+ unsigned TrueMemOrderLatency;
+
+public:
+ Value2SUsMap(unsigned lat = 0) : TrueMemOrderLatency(lat) {}
+
+ /// To keep NumNodes up to date, insert() is used instead of
+ /// this operator w/ push_back().
+ ValueType &operator[](const SUList &Key) {
+ llvm_unreachable("Don't use. Use insert() instead."); };
+
+ /// Adds SU to the SUList of V. If Map grows huge, reduce its size by calling
+ /// reduce().
+ void inline insert(SUnit *SU, ValueType V) {
+ MapVector::operator[](V).push_back(SU);
+ NumNodes++;
+ }
+
+ /// Clears the list of SUs mapped to V.
+ void inline clearList(ValueType V) {
+ iterator Itr = find(V);
+ if (Itr != end()) {
+ assert(NumNodes >= Itr->second.size());
+ NumNodes -= Itr->second.size();
+
+ Itr->second.clear();
+ }
+ }
+
+ /// Clears map from all contents.
+ void clear() {
+ MapVector<ValueType, SUList>::clear();
+ NumNodes = 0;
+ }
+
+ unsigned inline size() const { return NumNodes; }
+
+ /// Counts the number of SUs in this map after a reduction.
+ void reComputeSize() {
+ NumNodes = 0;
+ for (auto &I : *this)
+ NumNodes += I.second.size();
+ }
+
+ unsigned inline getTrueMemOrderLatency() const {
+ return TrueMemOrderLatency;
+ }
+
+ void dump();
+};
+
+void ScheduleDAGInstrs::addChainDependencies(SUnit *SU,
+ Value2SUsMap &Val2SUsMap) {
+ for (auto &I : Val2SUsMap)
+ addChainDependencies(SU, I.second,
+ Val2SUsMap.getTrueMemOrderLatency());
+}
+
+void ScheduleDAGInstrs::addChainDependencies(SUnit *SU,
+ Value2SUsMap &Val2SUsMap,
+ ValueType V) {
+ Value2SUsMap::iterator Itr = Val2SUsMap.find(V);
+ if (Itr != Val2SUsMap.end())
+ addChainDependencies(SU, Itr->second,
+ Val2SUsMap.getTrueMemOrderLatency());
+}
+
+void ScheduleDAGInstrs::addBarrierChain(Value2SUsMap &map) {
+ assert(BarrierChain != nullptr);
+
+ for (auto &I : map) {
+ SUList &sus = I.second;
+ for (auto *SU : sus)
+ SU->addPredBarrier(BarrierChain);
+ }
+ map.clear();
+}
+
+void ScheduleDAGInstrs::insertBarrierChain(Value2SUsMap &map) {
+ assert(BarrierChain != nullptr);
+
+ // Go through all lists of SUs.
+ for (Value2SUsMap::iterator I = map.begin(), EE = map.end(); I != EE;) {
+ Value2SUsMap::iterator CurrItr = I++;
+ SUList &sus = CurrItr->second;
+ SUList::iterator SUItr = sus.begin(), SUEE = sus.end();
+ for (; SUItr != SUEE; ++SUItr) {
+ // Stop on BarrierChain or any instruction above it.
+ if ((*SUItr)->NodeNum <= BarrierChain->NodeNum)
+ break;
+
+ (*SUItr)->addPredBarrier(BarrierChain);
+ }
+
+ // Remove also the BarrierChain from list if present.
+ if (SUItr != SUEE && *SUItr == BarrierChain)
+ SUItr++;
+
+ // Remove all SUs that are now successors of BarrierChain.
+ if (SUItr != sus.begin())
+ sus.erase(sus.begin(), SUItr);
+ }
+
+ // Remove all entries with empty su lists.
+ map.remove_if([&](std::pair<ValueType, SUList> &mapEntry) {
+ return (mapEntry.second.empty()); });
+
+ // Recompute the size of the map (NumNodes).
+ map.reComputeSize();
+}
+
+void ScheduleDAGInstrs::buildSchedGraph(AAResults *AA,
+ RegPressureTracker *RPTracker,
+ PressureDiffs *PDiffs,
+ LiveIntervals *LIS,
+ bool TrackLaneMasks) {
+ const TargetSubtargetInfo &ST = MF.getSubtarget();
+ bool UseAA = EnableAASchedMI.getNumOccurrences() > 0 ? EnableAASchedMI
+ : ST.useAA();
+ AAForDep = UseAA ? AA : nullptr;
+
+ BarrierChain = nullptr;
+
+ this->TrackLaneMasks = TrackLaneMasks;
+ MISUnitMap.clear();
+ ScheduleDAG::clearDAG();
+
+ // Create an SUnit for each real instruction.
+ initSUnits();
+
+ if (PDiffs)
+ PDiffs->init(SUnits.size());
+
+ // We build scheduling units by walking a block's instruction list
+ // from bottom to top.
+
+ // Each MIs' memory operand(s) is analyzed to a list of underlying
+ // objects. The SU is then inserted in the SUList(s) mapped from the
+ // Value(s). Each Value thus gets mapped to lists of SUs depending
+ // on it, stores and loads kept separately. Two SUs are trivially
+ // non-aliasing if they both depend on only identified Values and do
+ // not share any common Value.
+ Value2SUsMap Stores, Loads(1 /*TrueMemOrderLatency*/);
+
+ // Certain memory accesses are known to not alias any SU in Stores
+ // or Loads, and have therefore their own 'NonAlias'
+ // domain. E.g. spill / reload instructions never alias LLVM I/R
+ // Values. It would be nice to assume that this type of memory
+ // accesses always have a proper memory operand modelling, and are
+ // therefore never unanalyzable, but this is conservatively not
+ // done.
+ Value2SUsMap NonAliasStores, NonAliasLoads(1 /*TrueMemOrderLatency*/);
+
+ // Track all instructions that may raise floating-point exceptions.
+ // These do not depend on one other (or normal loads or stores), but
+ // must not be rescheduled across global barriers. Note that we don't
+ // really need a "map" here since we don't track those MIs by value;
+ // using the same Value2SUsMap data type here is simply a matter of
+ // convenience.
+ Value2SUsMap FPExceptions;
+
+ // Remove any stale debug info; sometimes BuildSchedGraph is called again
+ // without emitting the info from the previous call.
+ DbgValues.clear();
+ FirstDbgValue = nullptr;
+
+ assert(Defs.empty() && Uses.empty() &&
+ "Only BuildGraph should update Defs/Uses");
+ Defs.setUniverse(TRI->getNumRegs());
+ Uses.setUniverse(TRI->getNumRegs());
+
+ assert(CurrentVRegDefs.empty() && "nobody else should use CurrentVRegDefs");
+ assert(CurrentVRegUses.empty() && "nobody else should use CurrentVRegUses");
+ unsigned NumVirtRegs = MRI.getNumVirtRegs();
+ CurrentVRegDefs.setUniverse(NumVirtRegs);
+ CurrentVRegUses.setUniverse(NumVirtRegs);
+
+ // Model data dependencies between instructions being scheduled and the
+ // ExitSU.
+ addSchedBarrierDeps();
+
+ // Walk the list of instructions, from bottom moving up.
+ MachineInstr *DbgMI = nullptr;
+ for (MachineBasicBlock::iterator MII = RegionEnd, MIE = RegionBegin;
+ MII != MIE; --MII) {
+ MachineInstr &MI = *std::prev(MII);
+ if (DbgMI) {
+ DbgValues.push_back(std::make_pair(DbgMI, &MI));
+ DbgMI = nullptr;
+ }
+
+ if (MI.isDebugValue()) {
+ DbgMI = &MI;
+ continue;
+ }
+ if (MI.isDebugLabel())
+ continue;
+
+ SUnit *SU = MISUnitMap[&MI];
+ assert(SU && "No SUnit mapped to this MI");
+
+ if (RPTracker) {
+ RegisterOperands RegOpers;
+ RegOpers.collect(MI, *TRI, MRI, TrackLaneMasks, false);
+ if (TrackLaneMasks) {
+ SlotIndex SlotIdx = LIS->getInstructionIndex(MI);
+ RegOpers.adjustLaneLiveness(*LIS, MRI, SlotIdx);
+ }
+ if (PDiffs != nullptr)
+ PDiffs->addInstruction(SU->NodeNum, RegOpers, MRI);
+
+ if (RPTracker->getPos() == RegionEnd || &*RPTracker->getPos() != &MI)
+ RPTracker->recedeSkipDebugValues();
+ assert(&*RPTracker->getPos() == &MI && "RPTracker in sync");
+ RPTracker->recede(RegOpers);
+ }
+
+ assert(
+ (CanHandleTerminators || (!MI.isTerminator() && !MI.isPosition())) &&
+ "Cannot schedule terminators or labels!");
+
+ // Add register-based dependencies (data, anti, and output).
+ // For some instructions (calls, returns, inline-asm, etc.) there can
+ // be explicit uses and implicit defs, in which case the use will appear
+ // on the operand list before the def. Do two passes over the operand
+ // list to make sure that defs are processed before any uses.
+ bool HasVRegDef = false;
+ for (unsigned j = 0, n = MI.getNumOperands(); j != n; ++j) {
+ const MachineOperand &MO = MI.getOperand(j);
+ if (!MO.isReg() || !MO.isDef())
+ continue;
+ Register Reg = MO.getReg();
+ if (Register::isPhysicalRegister(Reg)) {
+ addPhysRegDeps(SU, j);
+ } else if (Register::isVirtualRegister(Reg)) {
+ HasVRegDef = true;
+ addVRegDefDeps(SU, j);
+ }
+ }
+ // Now process all uses.
+ for (unsigned j = 0, n = MI.getNumOperands(); j != n; ++j) {
+ const MachineOperand &MO = MI.getOperand(j);
+ // Only look at use operands.
+ // We do not need to check for MO.readsReg() here because subsequent
+ // subregister defs will get output dependence edges and need no
+ // additional use dependencies.
+ if (!MO.isReg() || !MO.isUse())
+ continue;
+ Register Reg = MO.getReg();
+ if (Register::isPhysicalRegister(Reg)) {
+ addPhysRegDeps(SU, j);
+ } else if (Register::isVirtualRegister(Reg) && MO.readsReg()) {
+ addVRegUseDeps(SU, j);
+ }
+ }
+
+ // If we haven't seen any uses in this scheduling region, create a
+ // dependence edge to ExitSU to model the live-out latency. This is required
+ // for vreg defs with no in-region use, and prefetches with no vreg def.
+ //
+ // FIXME: NumDataSuccs would be more precise than NumSuccs here. This
+ // check currently relies on being called before adding chain deps.
+ if (SU->NumSuccs == 0 && SU->Latency > 1 && (HasVRegDef || MI.mayLoad())) {
+ SDep Dep(SU, SDep::Artificial);
+ Dep.setLatency(SU->Latency - 1);
+ ExitSU.addPred(Dep);
+ }
+
+ // Add memory dependencies (Note: isStoreToStackSlot and
+ // isLoadFromStackSLot are not usable after stack slots are lowered to
+ // actual addresses).
+
+ // This is a barrier event that acts as a pivotal node in the DAG.
+ if (isGlobalMemoryObject(AA, &MI)) {
+
+ // Become the barrier chain.
+ if (BarrierChain)
+ BarrierChain->addPredBarrier(SU);
+ BarrierChain = SU;
+
+ LLVM_DEBUG(dbgs() << "Global memory object and new barrier chain: SU("
+ << BarrierChain->NodeNum << ").\n";);
+
+ // Add dependencies against everything below it and clear maps.
+ addBarrierChain(Stores);
+ addBarrierChain(Loads);
+ addBarrierChain(NonAliasStores);
+ addBarrierChain(NonAliasLoads);
+ addBarrierChain(FPExceptions);
+
+ continue;
+ }
+
+ // Instructions that may raise FP exceptions may not be moved
+ // across any global barriers.
+ if (MI.mayRaiseFPException()) {
+ if (BarrierChain)
+ BarrierChain->addPredBarrier(SU);
+
+ FPExceptions.insert(SU, UnknownValue);
+
+ if (FPExceptions.size() >= HugeRegion) {
+ LLVM_DEBUG(dbgs() << "Reducing FPExceptions map.\n";);
+ Value2SUsMap empty;
+ reduceHugeMemNodeMaps(FPExceptions, empty, getReductionSize());
+ }
+ }
+
+ // If it's not a store or a variant load, we're done.
+ if (!MI.mayStore() &&
+ !(MI.mayLoad() && !MI.isDereferenceableInvariantLoad(AA)))
+ continue;
+
+ // Always add dependecy edge to BarrierChain if present.
+ if (BarrierChain)
+ BarrierChain->addPredBarrier(SU);
+
+ // Find the underlying objects for MI. The Objs vector is either
+ // empty, or filled with the Values of memory locations which this
+ // SU depends on.
+ UnderlyingObjectsVector Objs;
+ bool ObjsFound = getUnderlyingObjectsForInstr(&MI, MFI, Objs,
+ MF.getDataLayout());
+
+ if (MI.mayStore()) {
+ if (!ObjsFound) {
+ // An unknown store depends on all stores and loads.
+ addChainDependencies(SU, Stores);
+ addChainDependencies(SU, NonAliasStores);
+ addChainDependencies(SU, Loads);
+ addChainDependencies(SU, NonAliasLoads);
+
+ // Map this store to 'UnknownValue'.
+ Stores.insert(SU, UnknownValue);
+ } else {
+ // Add precise dependencies against all previously seen memory
+ // accesses mapped to the same Value(s).
+ for (const UnderlyingObject &UnderlObj : Objs) {
+ ValueType V = UnderlObj.getValue();
+ bool ThisMayAlias = UnderlObj.mayAlias();
+
+ // Add dependencies to previous stores and loads mapped to V.
+ addChainDependencies(SU, (ThisMayAlias ? Stores : NonAliasStores), V);
+ addChainDependencies(SU, (ThisMayAlias ? Loads : NonAliasLoads), V);
+ }
+ // Update the store map after all chains have been added to avoid adding
+ // self-loop edge if multiple underlying objects are present.
+ for (const UnderlyingObject &UnderlObj : Objs) {
+ ValueType V = UnderlObj.getValue();
+ bool ThisMayAlias = UnderlObj.mayAlias();
+
+ // Map this store to V.
+ (ThisMayAlias ? Stores : NonAliasStores).insert(SU, V);
+ }
+ // The store may have dependencies to unanalyzable loads and
+ // stores.
+ addChainDependencies(SU, Loads, UnknownValue);
+ addChainDependencies(SU, Stores, UnknownValue);
+ }
+ } else { // SU is a load.
+ if (!ObjsFound) {
+ // An unknown load depends on all stores.
+ addChainDependencies(SU, Stores);
+ addChainDependencies(SU, NonAliasStores);
+
+ Loads.insert(SU, UnknownValue);
+ } else {
+ for (const UnderlyingObject &UnderlObj : Objs) {
+ ValueType V = UnderlObj.getValue();
+ bool ThisMayAlias = UnderlObj.mayAlias();
+
+ // Add precise dependencies against all previously seen stores
+ // mapping to the same Value(s).
+ addChainDependencies(SU, (ThisMayAlias ? Stores : NonAliasStores), V);
+
+ // Map this load to V.
+ (ThisMayAlias ? Loads : NonAliasLoads).insert(SU, V);
+ }
+ // The load may have dependencies to unanalyzable stores.
+ addChainDependencies(SU, Stores, UnknownValue);
+ }
+ }
+
+ // Reduce maps if they grow huge.
+ if (Stores.size() + Loads.size() >= HugeRegion) {
+ LLVM_DEBUG(dbgs() << "Reducing Stores and Loads maps.\n";);
+ reduceHugeMemNodeMaps(Stores, Loads, getReductionSize());
+ }
+ if (NonAliasStores.size() + NonAliasLoads.size() >= HugeRegion) {
+ LLVM_DEBUG(
+ dbgs() << "Reducing NonAliasStores and NonAliasLoads maps.\n";);
+ reduceHugeMemNodeMaps(NonAliasStores, NonAliasLoads, getReductionSize());
+ }
+ }
+
+ if (DbgMI)
+ FirstDbgValue = DbgMI;
+
+ Defs.clear();
+ Uses.clear();
+ CurrentVRegDefs.clear();
+ CurrentVRegUses.clear();
+
+ Topo.MarkDirty();
+}
+
+raw_ostream &llvm::operator<<(raw_ostream &OS, const PseudoSourceValue* PSV) {
+ PSV->printCustom(OS);
+ return OS;
+}
+
+void ScheduleDAGInstrs::Value2SUsMap::dump() {
+ for (auto &Itr : *this) {
+ if (Itr.first.is<const Value*>()) {
+ const Value *V = Itr.first.get<const Value*>();
+ if (isa<UndefValue>(V))
+ dbgs() << "Unknown";
+ else
+ V->printAsOperand(dbgs());
+ }
+ else if (Itr.first.is<const PseudoSourceValue*>())
+ dbgs() << Itr.first.get<const PseudoSourceValue*>();
+ else
+ llvm_unreachable("Unknown Value type.");
+
+ dbgs() << " : ";
+ dumpSUList(Itr.second);
+ }
+}
+
+void ScheduleDAGInstrs::reduceHugeMemNodeMaps(Value2SUsMap &stores,
+ Value2SUsMap &loads, unsigned N) {
+ LLVM_DEBUG(dbgs() << "Before reduction:\nStoring SUnits:\n"; stores.dump();
+ dbgs() << "Loading SUnits:\n"; loads.dump());
+
+ // Insert all SU's NodeNums into a vector and sort it.
+ std::vector<unsigned> NodeNums;
+ NodeNums.reserve(stores.size() + loads.size());
+ for (auto &I : stores)
+ for (auto *SU : I.second)
+ NodeNums.push_back(SU->NodeNum);
+ for (auto &I : loads)
+ for (auto *SU : I.second)
+ NodeNums.push_back(SU->NodeNum);
+ llvm::sort(NodeNums);
+
+ // The N last elements in NodeNums will be removed, and the SU with
+ // the lowest NodeNum of them will become the new BarrierChain to
+ // let the not yet seen SUs have a dependency to the removed SUs.
+ assert(N <= NodeNums.size());
+ SUnit *newBarrierChain = &SUnits[*(NodeNums.end() - N)];
+ if (BarrierChain) {
+ // The aliasing and non-aliasing maps reduce independently of each
+ // other, but share a common BarrierChain. Check if the
+ // newBarrierChain is above the former one. If it is not, it may
+ // introduce a loop to use newBarrierChain, so keep the old one.
+ if (newBarrierChain->NodeNum < BarrierChain->NodeNum) {
+ BarrierChain->addPredBarrier(newBarrierChain);
+ BarrierChain = newBarrierChain;
+ LLVM_DEBUG(dbgs() << "Inserting new barrier chain: SU("
+ << BarrierChain->NodeNum << ").\n";);
+ }
+ else
+ LLVM_DEBUG(dbgs() << "Keeping old barrier chain: SU("
+ << BarrierChain->NodeNum << ").\n";);
+ }
+ else
+ BarrierChain = newBarrierChain;
+
+ insertBarrierChain(stores);
+ insertBarrierChain(loads);
+
+ LLVM_DEBUG(dbgs() << "After reduction:\nStoring SUnits:\n"; stores.dump();
+ dbgs() << "Loading SUnits:\n"; loads.dump());
+}
+
+static void toggleKills(const MachineRegisterInfo &MRI, LivePhysRegs &LiveRegs,
+ MachineInstr &MI, bool addToLiveRegs) {
+ for (MachineOperand &MO : MI.operands()) {
+ if (!MO.isReg() || !MO.readsReg())
+ continue;
+ Register Reg = MO.getReg();
+ if (!Reg)
+ continue;
+
+ // Things that are available after the instruction are killed by it.
+ bool IsKill = LiveRegs.available(MRI, Reg);
+ MO.setIsKill(IsKill);
+ if (addToLiveRegs)
+ LiveRegs.addReg(Reg);
+ }
+}
+
+void ScheduleDAGInstrs::fixupKills(MachineBasicBlock &MBB) {
+ LLVM_DEBUG(dbgs() << "Fixup kills for " << printMBBReference(MBB) << '\n');
+
+ LiveRegs.init(*TRI);
+ LiveRegs.addLiveOuts(MBB);
+
+ // Examine block from end to start...
+ for (MachineInstr &MI : make_range(MBB.rbegin(), MBB.rend())) {
+ if (MI.isDebugInstr())
+ continue;
+
+ // Update liveness. Registers that are defed but not used in this
+ // instruction are now dead. Mark register and all subregs as they
+ // are completely defined.
+ for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
+ const MachineOperand &MO = *O;
+ if (MO.isReg()) {
+ if (!MO.isDef())
+ continue;
+ Register Reg = MO.getReg();
+ if (!Reg)
+ continue;
+ LiveRegs.removeReg(Reg);
+ } else if (MO.isRegMask()) {
+ LiveRegs.removeRegsInMask(MO);
+ }
+ }
+
+ // If there is a bundle header fix it up first.
+ if (!MI.isBundled()) {
+ toggleKills(MRI, LiveRegs, MI, true);
+ } else {
+ MachineBasicBlock::instr_iterator Bundle = MI.getIterator();
+ if (MI.isBundle())
+ toggleKills(MRI, LiveRegs, MI, false);
+
+ // Some targets make the (questionable) assumtion that the instructions
+ // inside the bundle are ordered and consequently only the last use of
+ // a register inside the bundle can kill it.
+ MachineBasicBlock::instr_iterator I = std::next(Bundle);
+ while (I->isBundledWithSucc())
+ ++I;
+ do {
+ if (!I->isDebugInstr())
+ toggleKills(MRI, LiveRegs, *I, true);
+ --I;
+ } while (I != Bundle);
+ }
+ }
+}
+
+void ScheduleDAGInstrs::dumpNode(const SUnit &SU) const {
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+ dumpNodeName(SU);
+ dbgs() << ": ";
+ SU.getInstr()->dump();
+#endif
+}
+
+void ScheduleDAGInstrs::dump() const {
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+ if (EntrySU.getInstr() != nullptr)
+ dumpNodeAll(EntrySU);
+ for (const SUnit &SU : SUnits)
+ dumpNodeAll(SU);
+ if (ExitSU.getInstr() != nullptr)
+ dumpNodeAll(ExitSU);
+#endif
+}
+
+std::string ScheduleDAGInstrs::getGraphNodeLabel(const SUnit *SU) const {
+ std::string s;
+ raw_string_ostream oss(s);
+ if (SU == &EntrySU)
+ oss << "<entry>";
+ else if (SU == &ExitSU)
+ oss << "<exit>";
+ else
+ SU->getInstr()->print(oss, /*SkipOpers=*/true);
+ return oss.str();
+}
+
+/// Return the basic block label. It is not necessarilly unique because a block
+/// contains multiple scheduling regions. But it is fine for visualization.
+std::string ScheduleDAGInstrs::getDAGName() const {
+ return "dag." + BB->getFullName();
+}
+
+bool ScheduleDAGInstrs::canAddEdge(SUnit *SuccSU, SUnit *PredSU) {
+ return SuccSU == &ExitSU || !Topo.IsReachable(PredSU, SuccSU);
+}
+
+bool ScheduleDAGInstrs::addEdge(SUnit *SuccSU, const SDep &PredDep) {
+ if (SuccSU != &ExitSU) {
+ // Do not use WillCreateCycle, it assumes SD scheduling.
+ // If Pred is reachable from Succ, then the edge creates a cycle.
+ if (Topo.IsReachable(PredDep.getSUnit(), SuccSU))
+ return false;
+ Topo.AddPredQueued(SuccSU, PredDep.getSUnit());
+ }
+ SuccSU->addPred(PredDep, /*Required=*/!PredDep.isArtificial());
+ // Return true regardless of whether a new edge needed to be inserted.
+ return true;
+}
+
+//===----------------------------------------------------------------------===//
+// SchedDFSResult Implementation
+//===----------------------------------------------------------------------===//
+
+namespace llvm {
+
+/// Internal state used to compute SchedDFSResult.
+class SchedDFSImpl {
+ SchedDFSResult &R;
+
+ /// Join DAG nodes into equivalence classes by their subtree.
+ IntEqClasses SubtreeClasses;
+ /// List PredSU, SuccSU pairs that represent data edges between subtrees.
+ std::vector<std::pair<const SUnit *, const SUnit*>> ConnectionPairs;
+
+ struct RootData {
+ unsigned NodeID;
+ unsigned ParentNodeID; ///< Parent node (member of the parent subtree).
+ unsigned SubInstrCount = 0; ///< Instr count in this tree only, not
+ /// children.
+
+ RootData(unsigned id): NodeID(id),
+ ParentNodeID(SchedDFSResult::InvalidSubtreeID) {}
+
+ unsigned getSparseSetIndex() const { return NodeID; }
+ };
+
+ SparseSet<RootData> RootSet;
+
+public:
+ SchedDFSImpl(SchedDFSResult &r): R(r), SubtreeClasses(R.DFSNodeData.size()) {
+ RootSet.setUniverse(R.DFSNodeData.size());
+ }
+
+ /// Returns true if this node been visited by the DFS traversal.
+ ///
+ /// During visitPostorderNode the Node's SubtreeID is assigned to the Node
+ /// ID. Later, SubtreeID is updated but remains valid.
+ bool isVisited(const SUnit *SU) const {
+ return R.DFSNodeData[SU->NodeNum].SubtreeID
+ != SchedDFSResult::InvalidSubtreeID;
+ }
+
+ /// Initializes this node's instruction count. We don't need to flag the node
+ /// visited until visitPostorder because the DAG cannot have cycles.
+ void visitPreorder(const SUnit *SU) {
+ R.DFSNodeData[SU->NodeNum].InstrCount =
+ SU->getInstr()->isTransient() ? 0 : 1;
+ }
+
+ /// Called once for each node after all predecessors are visited. Revisit this
+ /// node's predecessors and potentially join them now that we know the ILP of
+ /// the other predecessors.
+ void visitPostorderNode(const SUnit *SU) {
+ // Mark this node as the root of a subtree. It may be joined with its
+ // successors later.
+ R.DFSNodeData[SU->NodeNum].SubtreeID = SU->NodeNum;
+ RootData RData(SU->NodeNum);
+ RData.SubInstrCount = SU->getInstr()->isTransient() ? 0 : 1;
+
+ // If any predecessors are still in their own subtree, they either cannot be
+ // joined or are large enough to remain separate. If this parent node's
+ // total instruction count is not greater than a child subtree by at least
+ // the subtree limit, then try to join it now since splitting subtrees is
+ // only useful if multiple high-pressure paths are possible.
+ unsigned InstrCount = R.DFSNodeData[SU->NodeNum].InstrCount;
+ for (const SDep &PredDep : SU->Preds) {
+ if (PredDep.getKind() != SDep::Data)
+ continue;
+ unsigned PredNum = PredDep.getSUnit()->NodeNum;
+ if ((InstrCount - R.DFSNodeData[PredNum].InstrCount) < R.SubtreeLimit)
+ joinPredSubtree(PredDep, SU, /*CheckLimit=*/false);
+
+ // Either link or merge the TreeData entry from the child to the parent.
+ if (R.DFSNodeData[PredNum].SubtreeID == PredNum) {
+ // If the predecessor's parent is invalid, this is a tree edge and the
+ // current node is the parent.
+ if (RootSet[PredNum].ParentNodeID == SchedDFSResult::InvalidSubtreeID)
+ RootSet[PredNum].ParentNodeID = SU->NodeNum;
+ }
+ else if (RootSet.count(PredNum)) {
+ // The predecessor is not a root, but is still in the root set. This
+ // must be the new parent that it was just joined to. Note that
+ // RootSet[PredNum].ParentNodeID may either be invalid or may still be
+ // set to the original parent.
+ RData.SubInstrCount += RootSet[PredNum].SubInstrCount;
+ RootSet.erase(PredNum);
+ }
+ }
+ RootSet[SU->NodeNum] = RData;
+ }
+
+ /// Called once for each tree edge after calling visitPostOrderNode on
+ /// the predecessor. Increment the parent node's instruction count and
+ /// preemptively join this subtree to its parent's if it is small enough.
+ void visitPostorderEdge(const SDep &PredDep, const SUnit *Succ) {
+ R.DFSNodeData[Succ->NodeNum].InstrCount
+ += R.DFSNodeData[PredDep.getSUnit()->NodeNum].InstrCount;
+ joinPredSubtree(PredDep, Succ);
+ }
+
+ /// Adds a connection for cross edges.
+ void visitCrossEdge(const SDep &PredDep, const SUnit *Succ) {
+ ConnectionPairs.push_back(std::make_pair(PredDep.getSUnit(), Succ));
+ }
+
+ /// Sets each node's subtree ID to the representative ID and record
+ /// connections between trees.
+ void finalize() {
+ SubtreeClasses.compress();
+ R.DFSTreeData.resize(SubtreeClasses.getNumClasses());
+ assert(SubtreeClasses.getNumClasses() == RootSet.size()
+ && "number of roots should match trees");
+ for (const RootData &Root : RootSet) {
+ unsigned TreeID = SubtreeClasses[Root.NodeID];
+ if (Root.ParentNodeID != SchedDFSResult::InvalidSubtreeID)
+ R.DFSTreeData[TreeID].ParentTreeID = SubtreeClasses[Root.ParentNodeID];
+ R.DFSTreeData[TreeID].SubInstrCount = Root.SubInstrCount;
+ // Note that SubInstrCount may be greater than InstrCount if we joined
+ // subtrees across a cross edge. InstrCount will be attributed to the
+ // original parent, while SubInstrCount will be attributed to the joined
+ // parent.
+ }
+ R.SubtreeConnections.resize(SubtreeClasses.getNumClasses());
+ R.SubtreeConnectLevels.resize(SubtreeClasses.getNumClasses());
+ LLVM_DEBUG(dbgs() << R.getNumSubtrees() << " subtrees:\n");
+ for (unsigned Idx = 0, End = R.DFSNodeData.size(); Idx != End; ++Idx) {
+ R.DFSNodeData[Idx].SubtreeID = SubtreeClasses[Idx];
+ LLVM_DEBUG(dbgs() << " SU(" << Idx << ") in tree "
+ << R.DFSNodeData[Idx].SubtreeID << '\n');
+ }
+ for (const std::pair<const SUnit*, const SUnit*> &P : ConnectionPairs) {
+ unsigned PredTree = SubtreeClasses[P.first->NodeNum];
+ unsigned SuccTree = SubtreeClasses[P.second->NodeNum];
+ if (PredTree == SuccTree)
+ continue;
+ unsigned Depth = P.first->getDepth();
+ addConnection(PredTree, SuccTree, Depth);
+ addConnection(SuccTree, PredTree, Depth);
+ }
+ }
+
+protected:
+ /// Joins the predecessor subtree with the successor that is its DFS parent.
+ /// Applies some heuristics before joining.
+ bool joinPredSubtree(const SDep &PredDep, const SUnit *Succ,
+ bool CheckLimit = true) {
+ assert(PredDep.getKind() == SDep::Data && "Subtrees are for data edges");
+
+ // Check if the predecessor is already joined.
+ const SUnit *PredSU = PredDep.getSUnit();
+ unsigned PredNum = PredSU->NodeNum;
+ if (R.DFSNodeData[PredNum].SubtreeID != PredNum)
+ return false;
+
+ // Four is the magic number of successors before a node is considered a
+ // pinch point.
+ unsigned NumDataSucs = 0;
+ for (const SDep &SuccDep : PredSU->Succs) {
+ if (SuccDep.getKind() == SDep::Data) {
+ if (++NumDataSucs >= 4)
+ return false;
+ }
+ }
+ if (CheckLimit && R.DFSNodeData[PredNum].InstrCount > R.SubtreeLimit)
+ return false;
+ R.DFSNodeData[PredNum].SubtreeID = Succ->NodeNum;
+ SubtreeClasses.join(Succ->NodeNum, PredNum);
+ return true;
+ }
+
+ /// Called by finalize() to record a connection between trees.
+ void addConnection(unsigned FromTree, unsigned ToTree, unsigned Depth) {
+ if (!Depth)
+ return;
+
+ do {
+ SmallVectorImpl<SchedDFSResult::Connection> &Connections =
+ R.SubtreeConnections[FromTree];
+ for (SchedDFSResult::Connection &C : Connections) {
+ if (C.TreeID == ToTree) {
+ C.Level = std::max(C.Level, Depth);
+ return;
+ }
+ }
+ Connections.push_back(SchedDFSResult::Connection(ToTree, Depth));
+ FromTree = R.DFSTreeData[FromTree].ParentTreeID;
+ } while (FromTree != SchedDFSResult::InvalidSubtreeID);
+ }
+};
+
+} // end namespace llvm
+
+namespace {
+
+/// Manage the stack used by a reverse depth-first search over the DAG.
+class SchedDAGReverseDFS {
+ std::vector<std::pair<const SUnit *, SUnit::const_pred_iterator>> DFSStack;
+
+public:
+ bool isComplete() const { return DFSStack.empty(); }
+
+ void follow(const SUnit *SU) {
+ DFSStack.push_back(std::make_pair(SU, SU->Preds.begin()));
+ }
+ void advance() { ++DFSStack.back().second; }
+
+ const SDep *backtrack() {
+ DFSStack.pop_back();
+ return DFSStack.empty() ? nullptr : std::prev(DFSStack.back().second);
+ }
+
+ const SUnit *getCurr() const { return DFSStack.back().first; }
+
+ SUnit::const_pred_iterator getPred() const { return DFSStack.back().second; }
+
+ SUnit::const_pred_iterator getPredEnd() const {
+ return getCurr()->Preds.end();
+ }
+};
+
+} // end anonymous namespace
+
+static bool hasDataSucc(const SUnit *SU) {
+ for (const SDep &SuccDep : SU->Succs) {
+ if (SuccDep.getKind() == SDep::Data &&
+ !SuccDep.getSUnit()->isBoundaryNode())
+ return true;
+ }
+ return false;
+}
+
+/// Computes an ILP metric for all nodes in the subDAG reachable via depth-first
+/// search from this root.
+void SchedDFSResult::compute(ArrayRef<SUnit> SUnits) {
+ if (!IsBottomUp)
+ llvm_unreachable("Top-down ILP metric is unimplemented");
+
+ SchedDFSImpl Impl(*this);
+ for (const SUnit &SU : SUnits) {
+ if (Impl.isVisited(&SU) || hasDataSucc(&SU))
+ continue;
+
+ SchedDAGReverseDFS DFS;
+ Impl.visitPreorder(&SU);
+ DFS.follow(&SU);
+ while (true) {
+ // Traverse the leftmost path as far as possible.
+ while (DFS.getPred() != DFS.getPredEnd()) {
+ const SDep &PredDep = *DFS.getPred();
+ DFS.advance();
+ // Ignore non-data edges.
+ if (PredDep.getKind() != SDep::Data
+ || PredDep.getSUnit()->isBoundaryNode()) {
+ continue;
+ }
+ // An already visited edge is a cross edge, assuming an acyclic DAG.
+ if (Impl.isVisited(PredDep.getSUnit())) {
+ Impl.visitCrossEdge(PredDep, DFS.getCurr());
+ continue;
+ }
+ Impl.visitPreorder(PredDep.getSUnit());
+ DFS.follow(PredDep.getSUnit());
+ }
+ // Visit the top of the stack in postorder and backtrack.
+ const SUnit *Child = DFS.getCurr();
+ const SDep *PredDep = DFS.backtrack();
+ Impl.visitPostorderNode(Child);
+ if (PredDep)
+ Impl.visitPostorderEdge(*PredDep, DFS.getCurr());
+ if (DFS.isComplete())
+ break;
+ }
+ }
+ Impl.finalize();
+}
+
+/// The root of the given SubtreeID was just scheduled. For all subtrees
+/// connected to this tree, record the depth of the connection so that the
+/// nearest connected subtrees can be prioritized.
+void SchedDFSResult::scheduleTree(unsigned SubtreeID) {
+ for (const Connection &C : SubtreeConnections[SubtreeID]) {
+ SubtreeConnectLevels[C.TreeID] =
+ std::max(SubtreeConnectLevels[C.TreeID], C.Level);
+ LLVM_DEBUG(dbgs() << " Tree: " << C.TreeID << " @"
+ << SubtreeConnectLevels[C.TreeID] << '\n');
+ }
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void ILPValue::print(raw_ostream &OS) const {
+ OS << InstrCount << " / " << Length << " = ";
+ if (!Length)
+ OS << "BADILP";
+ else
+ OS << format("%g", ((double)InstrCount / Length));
+}
+
+LLVM_DUMP_METHOD void ILPValue::dump() const {
+ dbgs() << *this << '\n';
+}
+
+namespace llvm {
+
+LLVM_DUMP_METHOD
+raw_ostream &operator<<(raw_ostream &OS, const ILPValue &Val) {
+ Val.print(OS);
+ return OS;
+}
+
+} // end namespace llvm
+
+#endif
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