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llvm-project/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp

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//===---- ScheduleDAGInstrs.cpp - MachineInstr Rescheduling ---------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements the ScheduleDAGInstrs class, which implements re-scheduling
// of MachineInstrs.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/ADT/IntEqClasses.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/CodeGen/ScheduleDFS.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Operator.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
#define DEBUG_TYPE "misched"
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), CanHandleTerminators(false),
TrackLaneMasks(false), AAForDep(nullptr), BarrierChain(nullptr),
UnknownValue(UndefValue::get(
Type::getVoidTy(mf.getFunction()->getContext()))),
FirstDbgValue(nullptr) {
DbgValues.clear();
const TargetSubtargetInfo &ST = mf.getSubtarget();
SchedModel.init(ST.getSchedModel(), &ST, TII);
}
/// getUnderlyingObjectFromInt - This is the function that does the work of
/// looking through basic ptrtoint+arithmetic+inttoptr sequences.
static const Value *getUnderlyingObjectFromInt(const Value *V) {
do {
if (const Operator *U = dyn_cast<Operator>(V)) {
// If we find a ptrtoint, we can transfer control back to the
// regular getUnderlyingObjectFromInt.
if (U->getOpcode() == Instruction::PtrToInt)
return U->getOperand(0);
// If we find an add of a constant, a multiplied value, or a phi, it's
// likely that the other operand will lead us to the base
// object. We don't have to worry about the case where the
// object address is somehow being computed by the multiply,
// because our callers only care when the result is an
// identifiable object.
if (U->getOpcode() != Instruction::Add ||
(!isa<ConstantInt>(U->getOperand(1)) &&
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
!isa<PHINode>(U->getOperand(1))))
return V;
V = U->getOperand(0);
} else {
return V;
}
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
} while (1);
}
/// getUnderlyingObjects - This is a wrapper around GetUnderlyingObjects
/// and adds support for basic ptrtoint+arithmetic+inttoptr sequences.
static void getUnderlyingObjects(const Value *V,
SmallVectorImpl<Value *> &Objects,
const DataLayout &DL) {
SmallPtrSet<const Value *, 16> Visited;
SmallVector<const Value *, 4> Working(1, V);
do {
V = Working.pop_back_val();
SmallVector<Value *, 4> Objs;
GetUnderlyingObjects(const_cast<Value *>(V), Objs, DL);
for (Value *V : Objs) {
if (!Visited.insert(V).second)
continue;
if (Operator::getOpcode(V) == Instruction::IntToPtr) {
const Value *O =
getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
if (O->getType()->isPointerTy()) {
Working.push_back(O);
continue;
}
}
Objects.push_back(const_cast<Value *>(V));
}
} while (!Working.empty());
}
/// getUnderlyingObjectsForInstr - 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.
static void getUnderlyingObjectsForInstr(const MachineInstr *MI,
const MachineFrameInfo &MFI,
UnderlyingObjectsVector &Objects,
const DataLayout &DL) {
auto allMMOsOkay = [&]() {
for (const MachineMemOperand *MMO : MI->memoperands()) {
if (MMO->isVolatile())
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;
getUnderlyingObjects(V, Objs, DL);
for (Value *V : Objs) {
if (!isIdentifiedObject(V))
return false;
Objects.push_back(UnderlyingObjectsVector::value_type(V, true));
}
} else
return false;
}
return true;
};
if (!allMMOsOkay())
Objects.clear();
}
void ScheduleDAGInstrs::startBlock(MachineBasicBlock *bb) {
BB = bb;
}
void ScheduleDAGInstrs::finishBlock() {
// Subclasses should no longer refer to the old block.
BB = nullptr;
}
/// Initialize the DAG and common scheduler state for the current scheduling
/// region. This does not actually create the DAG, only clears it. The
/// scheduling driver may call BuildSchedGraph multiple times per scheduling
/// region.
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;
}
/// Close the current scheduling region. Don't clear any state in case the
/// driver wants to refer to the previous scheduling region.
void ScheduleDAGInstrs::exitRegion() {
// Nothing to do.
}
/// addSchedBarrierDeps - Add dependencies from instructions in the current
/// list of instructions being scheduled to scheduling barrier by adding
/// the exit SU to the register defs and use list. This is because we want to
/// make sure instructions which define registers that are either used by
/// the terminator or are live-out are properly scheduled. This is
/// especially important when the definition latency of the return value(s)
/// are too high to be hidden by the branch or when the liveout registers
/// used by instructions in the fallthrough block.
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;
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
} else if (TargetRegisterInfo::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. Add
/// 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();
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();
}
Dep.setLatency(
SchedModel.computeOperandLatency(SU->getInstr(), OperIdx, RegUse,
UseOp));
ST.adjustSchedDependency(SU, UseSU, Dep);
UseSU->addPred(Dep);
}
}
}
/// addPhysRegDeps - Add 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);
unsigned 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 this register's use list
if (Uses.contains(Reg))
Uses.eraseAll(Reg);
if (!MO.isDead()) {
Defs.eraseAll(Reg);
} else if (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
{
unsigned 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 ~0u;
unsigned SubReg = MO.getSubReg();
if (SubReg == 0)
return RC.getLaneMask();
return TRI->getSubRegIndexLaneMask(SubReg);
}
/// addVRegDefDeps - Add 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);
unsigned 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 ? ~0u : DefLaneMask;
// Clear undef flag, we'll re-add it later once we know which subregister
// Def is first.
MO.setIsUndef(false);
} else {
DefLaneMask = ~0u;
KillLaneMask = ~0u;
}
if (MO.isDead()) {
assert(CurrentVRegUses.find(Reg) == CurrentVRegUses.end() &&
"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) == 0) {
++I;
continue;
}
if ((LaneMask & DefLaneMask) != 0) {
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 != 0) {
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) == 0)
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 != 0)
CurrentVRegDefs.insert(VReg2SUnit(Reg, NonOverlapMask, DefSU));
}
// If there was no CurrentVRegDefs entry for some lanes yet, create one.
if (LaneMask != 0)
CurrentVRegDefs.insert(VReg2SUnit(Reg, LaneMask, SU));
}
/// addVRegUseDeps - Add 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);
unsigned Reg = MO.getReg();
// Remember the use. Data dependencies will be added when we find the def.
LaneBitmask LaneMask = TrackLaneMasks ? getLaneMaskForMO(MO) : ~0u;
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) == 0)
continue;
if (V2SU.SU == SU)
continue;
V2SU.SU->addPred(SDep(SU, SDep::Anti, Reg));
}
}
/// Return 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(AliasAnalysis *AA, MachineInstr *MI) {
return MI->isCall() || MI->hasUnmodeledSideEffects() ||
(MI->hasOrderedMemoryRef() && !MI->isDereferenceableInvariantLoad(AA));
}
/// This returns true if the two MIs need a chain edge between them.
/// This is called on normal stores and loads.
static bool MIsNeedChainEdge(AliasAnalysis *AA, const MachineFrameInfo *MFI,
const DataLayout &DL, MachineInstr *MIa,
MachineInstr *MIb) {
const MachineFunction *MF = MIa->getParent()->getParent();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
assert ((MIa->mayStore() || MIb->mayStore()) &&
"Dependency checked between two loads");
// Let the target decide if memory accesses cannot possibly overlap.
if (TII->areMemAccessesTriviallyDisjoint(*MIa, *MIb, AA))
return false;
// To this point analysis is generic. From here on we do need AA.
if (!AA)
return true;
// FIXME: Need to handle multiple memory operands to support all targets.
if (!MIa->hasOneMemOperand() || !MIb->hasOneMemOperand())
return true;
MachineMemOperand *MMOa = *MIa->memoperands_begin();
MachineMemOperand *MMOb = *MIb->memoperands_begin();
if (!MMOa->getValue() || !MMOb->getValue())
return true;
// The following interface to AA is fashioned after DAGCombiner::isAlias
// and operates with MachineMemOperand offset with some important
// assumptions:
// - LLVM fundamentally assumes flat address spaces.
// - MachineOperand offset can *only* result from legalization and
// cannot affect queries other than the trivial case of overlap
// checking.
// - These offsets never wrap and never step outside
// of allocated objects.
// - There should never be any negative offsets here.
//
// FIXME: Modify API to hide this math from "user"
// FIXME: Even before we go to AA we can reason locally about some
// memory objects. It can save compile time, and possibly catch some
// corner cases not currently covered.
assert ((MMOa->getOffset() >= 0) && "Negative MachineMemOperand offset");
assert ((MMOb->getOffset() >= 0) && "Negative MachineMemOperand offset");
int64_t MinOffset = std::min(MMOa->getOffset(), MMOb->getOffset());
int64_t Overlapa = MMOa->getSize() + MMOa->getOffset() - MinOffset;
int64_t Overlapb = MMOb->getSize() + MMOb->getOffset() - MinOffset;
AliasResult AAResult =
AA->alias(MemoryLocation(MMOa->getValue(), Overlapa,
UseTBAA ? MMOa->getAAInfo() : AAMDNodes()),
MemoryLocation(MMOb->getValue(), Overlapb,
UseTBAA ? MMOb->getAAInfo() : AAMDNodes()));
return (AAResult != NoAlias);
}
/// Check whether two objects need a chain edge and add it if needed.
void ScheduleDAGInstrs::addChainDependency (SUnit *SUa, SUnit *SUb,
unsigned Latency) {
if (MIsNeedChainEdge(AAForDep, &MFI, MF.getDataLayout(), SUa->getInstr(),
SUb->getInstr())) {
SDep Dep(SUa, SDep::MayAliasMem);
Dep.setLatency(Latency);
SUb->addPred(Dep);
}
}
/// Create 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 : llvm::make_range(RegionBegin, RegionEnd)) {
if (MI.isDebugValue())
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;
/// 1 for loads, 0 for stores. (see comment in SUList)
unsigned TrueMemOrderLatency;
public:
Value2SUsMap(unsigned lat = 0) : NumNodes(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."); };
/// Add 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; }
/// Count the number of SUs in this map after a reduction.
void reComputeSize(void) {
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();
}
/// If RegPressure is non-null, compute register pressure as a side effect. The
/// DAG builder is an efficient place to do it because it already visits
/// operands.
void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *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*/);
// 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;
}
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);
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;
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
addPhysRegDeps(SU, j);
} else if (TargetRegisterInfo::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;
unsigned Reg = MO.getReg();
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
addPhysRegDeps(SU, j);
} else if (TargetRegisterInfo::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;
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);
continue;
}
// 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. An empty vector means the memory location is
// unknown, and may alias anything.
UnderlyingObjectsVector Objs;
getUnderlyingObjectsForInstr(&MI, MFI, Objs, MF.getDataLayout());
if (MI.mayStore()) {
if (Objs.empty()) {
// 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 (Objs.empty()) {
// 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) {
DEBUG(dbgs() << "Reducing Stores and Loads maps.\n";);
reduceHugeMemNodeMaps(Stores, Loads, getReductionSize());
}
if (NonAliasStores.size() + NonAliasLoads.size() >= HugeRegion) {
DEBUG(dbgs() << "Reducing NonAliasStores and NonAliasLoads maps.\n";);
reduceHugeMemNodeMaps(NonAliasStores, NonAliasLoads, getReductionSize());
}
}
if (DbgMI)
FirstDbgValue = DbgMI;
Defs.clear();
Uses.clear();
CurrentVRegDefs.clear();
CurrentVRegUses.clear();
}
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);
}
}
/// Reduce maps in FIFO order, by N SUs. This is better than turning
/// every Nth memory SU into BarrierChain in buildSchedGraph(), since
/// it avoids unnecessary edges between seen SUs above the new
/// BarrierChain, and those below it.
void ScheduleDAGInstrs::reduceHugeMemNodeMaps(Value2SUsMap &stores,
Value2SUsMap &loads, unsigned N) {
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);
std::sort(NodeNums.begin(), NodeNums.end());
// 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;
DEBUG(dbgs() << "Inserting new barrier chain: SU("
<< BarrierChain->NodeNum << ").\n";);
}
else
DEBUG(dbgs() << "Keeping old barrier chain: SU("
<< BarrierChain->NodeNum << ").\n";);
}
else
BarrierChain = newBarrierChain;
insertBarrierChain(stores);
insertBarrierChain(loads);
DEBUG(dbgs() << "After reduction:\nStoring SUnits:\n";
stores.dump();
dbgs() << "Loading SUnits:\n";
loads.dump());
}
/// \brief Initialize register live-range state for updating kills.
void ScheduleDAGInstrs::startBlockForKills(MachineBasicBlock *BB) {
// Start with no live registers.
LiveRegs.reset();
// Examine the live-in regs of all successors.
for (const MachineBasicBlock *Succ : BB->successors()) {
for (const auto &LI : Succ->liveins()) {
// Repeat, for reg and all subregs.
for (MCSubRegIterator SubRegs(LI.PhysReg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
/// \brief If we change a kill flag on the bundle instruction implicit register
/// operands, then we also need to propagate that to any instructions inside
/// the bundle which had the same kill state.
static void toggleBundleKillFlag(MachineInstr *MI, unsigned Reg,
bool NewKillState,
const TargetRegisterInfo *TRI) {
if (MI->getOpcode() != TargetOpcode::BUNDLE)
return;
// Walk backwards from the last instruction in the bundle to the first.
// Once we set a kill flag on an instruction, we bail out, as otherwise we
// might set it on too many operands. We will clear as many flags as we
// can though.
MachineBasicBlock::instr_iterator Begin = MI->getIterator();
MachineBasicBlock::instr_iterator End = getBundleEnd(Begin);
while (Begin != End) {
if (NewKillState) {
if ((--End)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
return;
} else
(--End)->clearRegisterKills(Reg, TRI);
}
}
bool ScheduleDAGInstrs::toggleKillFlag(MachineInstr *MI, MachineOperand &MO) {
// Setting kill flag...
if (!MO.isKill()) {
MO.setIsKill(true);
toggleBundleKillFlag(MI, MO.getReg(), true, TRI);
return false;
}
// If MO itself is live, clear the kill flag...
if (LiveRegs.test(MO.getReg())) {
MO.setIsKill(false);
toggleBundleKillFlag(MI, MO.getReg(), false, TRI);
return false;
}
// If any subreg of MO is live, then create an imp-def for that
// subreg and keep MO marked as killed.
MO.setIsKill(false);
toggleBundleKillFlag(MI, MO.getReg(), false, TRI);
bool AllDead = true;
const unsigned SuperReg = MO.getReg();
MachineInstrBuilder MIB(MF, MI);
for (MCSubRegIterator SubRegs(SuperReg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
MIB.addReg(*SubRegs, RegState::ImplicitDefine);
AllDead = false;
}
}
if(AllDead) {
MO.setIsKill(true);
toggleBundleKillFlag(MI, MO.getReg(), true, TRI);
}
return false;
}
// FIXME: Reuse the LivePhysRegs utility for this.
void ScheduleDAGInstrs::fixupKills(MachineBasicBlock *MBB) {
DEBUG(dbgs() << "Fixup kills for BB#" << MBB->getNumber() << '\n');
LiveRegs.resize(TRI->getNumRegs());
BitVector killedRegs(TRI->getNumRegs());
startBlockForKills(MBB);
// Examine block from end to start...
unsigned Count = MBB->size();
for (MachineBasicBlock::iterator I = MBB->end(), E = MBB->begin();
I != E; --Count) {
MachineInstr &MI = *--I;
if (MI.isDebugValue())
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 (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (MO.isRegMask())
LiveRegs.clearBitsNotInMask(MO.getRegMask());
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
if (!MO.isDef()) continue;
// Ignore two-addr defs.
if (MI.isRegTiedToUseOperand(i)) continue;
// Repeat for reg and all subregs.
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.reset(*SubRegs);
}
// Examine all used registers and set/clear kill flag. When a
// register is used multiple times we only set the kill flag on
// the first use. Don't set kill flags on undef operands.
killedRegs.reset();
// toggleKillFlag can append new operands (implicit defs), so using
// a range-based loop is not safe. The new operands will be appended
// at the end of the operand list and they don't need to be visited,
// so iterating until the currently last operand is ok.
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
bool kill = false;
if (!killedRegs.test(Reg)) {
kill = true;
// A register is not killed if any subregs are live...
for (MCSubRegIterator SubRegs(Reg, TRI); SubRegs.isValid(); ++SubRegs) {
if (LiveRegs.test(*SubRegs)) {
kill = false;
break;
}
}
// If subreg is not live, then register is killed if it became
// live in this instruction
if (kill)
kill = !LiveRegs.test(Reg);
}
if (MO.isKill() != kill) {
DEBUG(dbgs() << "Fixing " << MO << " in ");
toggleKillFlag(&MI, MO);
DEBUG(MI.dump());
DEBUG({
if (MI.getOpcode() == TargetOpcode::BUNDLE) {
MachineBasicBlock::instr_iterator Begin = MI.getIterator();
MachineBasicBlock::instr_iterator End = getBundleEnd(Begin);
while (++Begin != End)
DEBUG(Begin->dump());
}
});
}
killedRegs.set(Reg);
}
// Mark any used register (that is not using undef) and subregs as
// now live...
for (const MachineOperand &MO : MI.operands()) {
if (!MO.isReg() || !MO.isUse() || MO.isUndef()) continue;
unsigned Reg = MO.getReg();
if ((Reg == 0) || MRI.isReserved(Reg)) continue;
for (MCSubRegIterator SubRegs(Reg, TRI, /*IncludeSelf=*/true);
SubRegs.isValid(); ++SubRegs)
LiveRegs.set(*SubRegs);
}
}
}
void ScheduleDAGInstrs::dumpNode(const SUnit *SU) const {
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
SU->getInstr()->dump();
#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();
}
//===----------------------------------------------------------------------===//
// SchedDFSResult Implementation
//===----------------------------------------------------------------------===//
namespace llvm {
/// \brief 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; // Instr count in this tree only, not children.
RootData(unsigned id): NodeID(id),
ParentNodeID(SchedDFSResult::InvalidSubtreeID),
SubInstrCount(0) {}
unsigned getSparseSetIndex() const { return NodeID; }
};
SparseSet<RootData> RootSet;
public:
SchedDFSImpl(SchedDFSResult &r): R(r), SubtreeClasses(R.DFSNodeData.size()) {
RootSet.setUniverse(R.DFSNodeData.size());
}
/// Return 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;
}
/// Initialize 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);
}
/// Add a connection for cross edges.
void visitCrossEdge(const SDep &PredDep, const SUnit *Succ) {
ConnectionPairs.push_back(std::make_pair(PredDep.getSUnit(), Succ));
}
/// Set 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());
DEBUG(dbgs() << R.getNumSubtrees() << " subtrees:\n");
for (unsigned Idx = 0, End = R.DFSNodeData.size(); Idx != End; ++Idx) {
R.DFSNodeData[Idx].SubtreeID = SubtreeClasses[Idx];
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:
/// Join the predecessor subtree with the successor that is its DFS
/// parent. Apply 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);
}
};
} // namespace llvm
namespace {
/// \brief 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();
}
};
} // anonymous
static bool hasDataSucc(const SUnit *SU) {
for (const SDep &SuccDep : SU->Succs) {
if (SuccDep.getKind() == SDep::Data &&
!SuccDep.getSUnit()->isBoundaryNode())
return true;
}
return false;
}
/// Compute 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 unimplemnted");
SchedDFSImpl Impl(*this);
for (const SUnit &SU : SUnits) {
if (Impl.isVisited(&SU) || hasDataSucc(&SU))
continue;
SchedDAGReverseDFS DFS;
Impl.visitPreorder(&SU);
DFS.follow(&SU);
for (;;) {
// 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);
DEBUG(dbgs() << " Tree: " << C.TreeID
<< " @" << SubtreeConnectLevels[C.TreeID] << '\n');
}
}
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;
}
} // namespace llvm
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