//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sched-instrs"
-#include "ScheduleDAGInstrs.h"
#include "llvm/Operator.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
+#include "llvm/CodeGen/RegisterPressure.h"
+#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/SmallPtrSet.h"
using namespace llvm;
+static cl::opt<bool> EnableAASchedMI("enable-aa-sched-mi", cl::Hidden,
+ cl::ZeroOrMore, cl::init(false),
+ cl::desc("Enable use of AA during MI GAD construction"));
+
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
const MachineLoopInfo &mli,
const MachineDominatorTree &mdt,
bool IsPostRAFlag,
LiveIntervals *lis)
: ScheduleDAG(mf), MLI(mli), MDT(mdt), MFI(mf.getFrameInfo()),
- InstrItins(mf.getTarget().getInstrItineraryData()), IsPostRA(IsPostRAFlag),
- LIS(lis), UnitLatencies(false), LoopRegs(MLI, MDT), FirstDbgValue(0) {
+ InstrItins(mf.getTarget().getInstrItineraryData()), LIS(lis),
+ IsPostRA(IsPostRAFlag), UnitLatencies(false), CanHandleTerminators(false),
+ LoopRegs(MDT), FirstDbgValue(0) {
assert((IsPostRA || LIS) && "PreRA scheduling requires LiveIntervals");
DbgValues.clear();
assert(!(IsPostRA && MRI.getNumVirtRegs()) &&
"Virtual registers must be removed prior to PostRA scheduling");
-}
-
-/// Run - perform scheduling.
-///
-void ScheduleDAGInstrs::Run(MachineBasicBlock *bb,
- MachineBasicBlock::iterator begin,
- MachineBasicBlock::iterator end,
- unsigned endcount) {
- BB = bb;
- Begin = begin;
- InsertPosIndex = endcount;
-
- // Check to see if the scheduler cares about latencies.
- UnitLatencies = ForceUnitLatencies();
- ScheduleDAG::Run(bb, end);
+ const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
+ SchedModel.init(*ST.getSchedModel(), &ST, TII);
}
/// getUnderlyingObjectFromInt - This is the function that does the work of
return 0;
}
-void ScheduleDAGInstrs::StartBlock(MachineBasicBlock *BB) {
+void ScheduleDAGInstrs::startBlock(MachineBasicBlock *bb) {
+ BB = bb;
LoopRegs.Deps.clear();
if (MachineLoop *ML = MLI.getLoopFor(BB))
if (BB == ML->getLoopLatch())
LoopRegs.VisitLoop(ML);
}
+void ScheduleDAGInstrs::finishBlock() {
+ // Subclasses should no longer refer to the old block.
+ BB = 0;
+}
+
/// Initialize the map with the number of registers.
-void ScheduleDAGInstrs::Reg2SUnitsMap::setRegLimit(unsigned Limit) {
+void Reg2SUnitsMap::setRegLimit(unsigned Limit) {
PhysRegSet.setUniverse(Limit);
SUnits.resize(Limit);
}
/// Clear the map without deallocating storage.
-void ScheduleDAGInstrs::Reg2SUnitsMap::clear() {
+void Reg2SUnitsMap::clear() {
for (const_iterator I = reg_begin(), E = reg_end(); I != E; ++I) {
SUnits[*I].clear();
}
PhysRegSet.clear();
}
-/// AddSchedBarrierDeps - Add dependencies from instructions in the current
+/// 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 endcount) {
+ assert(bb == BB && "startBlock should set BB");
+ RegionBegin = begin;
+ RegionEnd = end;
+ EndIndex = endcount;
+ MISUnitMap.clear();
+
+ // Check to see if the scheduler cares about latencies.
+ UnitLatencies = forceUnitLatencies();
+
+ ScheduleDAG::clearDAG();
+}
+
+/// 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
/// 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 = InsertPos != BB->end() ? &*InsertPos : 0;
+void ScheduleDAGInstrs::addSchedBarrierDeps() {
+ MachineInstr *ExitMI = RegionEnd != BB->end() ? &*RegionEnd : 0;
ExitSU.setInstr(ExitMI);
bool AllDepKnown = ExitMI &&
(ExitMI->isCall() || ExitMI->isBarrier());
if (Reg == 0) continue;
if (TRI->isPhysicalRegister(Reg))
- Uses[Reg].push_back(&ExitSU);
- else
+ Uses[Reg].push_back(PhysRegSUOper(&ExitSU, -1));
+ else {
assert(!IsPostRA && "Virtual register encountered after regalloc.");
+ addVRegUseDeps(&ExitSU, i);
+ }
}
} else {
// For others, e.g. fallthrough, conditional branch, assume the exit
// uses all the registers that are livein to the successor blocks.
- SmallSet<unsigned, 8> Seen;
+ assert(Uses.empty() && "Uses in set before adding deps?");
for (MachineBasicBlock::succ_iterator SI = BB->succ_begin(),
SE = BB->succ_end(); SI != SE; ++SI)
for (MachineBasicBlock::livein_iterator I = (*SI)->livein_begin(),
E = (*SI)->livein_end(); I != E; ++I) {
unsigned Reg = *I;
- if (Seen.insert(Reg))
- Uses[Reg].push_back(&ExitSU);
+ if (!Uses.contains(Reg))
+ Uses[Reg].push_back(PhysRegSUOper(&ExitSU, -1));
}
}
}
/// 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,
- const MachineOperand &MO) {
+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.
unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
unsigned DataLatency = SU->Latency;
- for (const unsigned *Alias = TRI->getOverlaps(MO.getReg()); *Alias; ++Alias) {
+ for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
+ Alias.isValid(); ++Alias) {
if (!Uses.contains(*Alias))
continue;
- std::vector<SUnit*> &UseList = Uses[*Alias];
+ std::vector<PhysRegSUOper> &UseList = Uses[*Alias];
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
- SUnit *UseSU = UseList[i];
+ SUnit *UseSU = UseList[i].SU;
if (UseSU == SU)
continue;
+ MachineInstr *UseMI = UseSU->getInstr();
+ int UseOp = UseList[i].OpIdx;
unsigned LDataLatency = DataLatency;
// Optionally add in a special extra latency for nodes that
// feed addresses.
// adjustSchedDependency for the targets that care about it.
if (SpecialAddressLatency != 0 && !UnitLatencies &&
UseSU != &ExitSU) {
- MachineInstr *UseMI = UseSU->getInstr();
const MCInstrDesc &UseMCID = UseMI->getDesc();
int RegUseIndex = UseMI->findRegisterUseOperandIdx(*Alias);
assert(RegUseIndex >= 0 && "UseMI doesn't use register!");
// Adjust the dependence latency using operand def/use
// information (if any), and then allow the target to
// perform its own adjustments.
- const SDep& dep = SDep(SU, SDep::Data, LDataLatency, *Alias);
+ SDep dep(SU, SDep::Data, LDataLatency, *Alias);
if (!UnitLatencies) {
- ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
- ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
+ MachineInstr *RegUse = UseOp < 0 ? 0 : UseMI;
+ dep.setLatency(
+ SchedModel.computeOperandLatency(SU->getInstr(), OperIdx,
+ RegUse, UseOp, /*FindMin=*/false));
+ dep.setMinLatency(
+ SchedModel.computeOperandLatency(SU->getInstr(), OperIdx,
+ RegUse, UseOp, /*FindMin=*/true));
+
+ ST.adjustSchedDependency(SU, UseSU, dep);
}
UseSU->addPred(dep);
}
// 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 (const unsigned *Alias = TRI->getOverlaps(MO.getReg()); *Alias; ++Alias) {
+ for (MCRegAliasIterator Alias(MO.getReg(), TRI, true);
+ Alias.isValid(); ++Alias) {
if (!Defs.contains(*Alias))
continue;
- std::vector<SUnit *> &DefList = Defs[*Alias];
+ std::vector<PhysRegSUOper> &DefList = Defs[*Alias];
for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
- SUnit *DefSU = DefList[i];
+ SUnit *DefSU = DefList[i].SU;
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
// 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[MO.getReg()].push_back(SU);
+ Uses[MO.getReg()].push_back(PhysRegSUOper(SU, OperIdx));
}
else {
- addPhysRegDataDeps(SU, MO);
+ addPhysRegDataDeps(SU, OperIdx);
// Either insert a new Reg2SUnits entry with an empty SUnits list, or
// retrieve the existing SUnits list for this register's defs.
- std::vector<SUnit *> &DefList = Defs[MO.getReg()];
+ std::vector<PhysRegSUOper> &DefList = Defs[MO.getReg()];
// If a def is going to wrap back around to the top of the loop,
// backschedule it.
// the block. Instead, we leave only one call at the back of the
// DefList.
if (SU->isCall) {
- while (!DefList.empty() && DefList.back()->isCall)
+ while (!DefList.empty() && DefList.back().SU->isCall)
DefList.pop_back();
}
// Defs are pushed in the order they are visited and never reordered.
- DefList.push_back(SU);
+ DefList.push_back(PhysRegSUOper(SU, OperIdx));
}
}
const MachineInstr *MI = SU->getInstr();
unsigned Reg = MI->getOperand(OperIdx).getReg();
- // SSA defs do not have output/anti dependencies.
+ // Singly defined vregs do not have output/anti dependencies.
// The current operand is a def, so we have at least one.
- if (llvm::next(MRI.def_begin(Reg)) == MRI.def_end())
+ // Check here if there are any others...
+ if (MRI.hasOneDef(Reg))
return;
// Add output dependence to the next nearest def of this vreg.
// 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.
- VReg2SUnitMap::iterator DefI = findVRegDef(Reg);
+ VReg2SUnitMap::iterator DefI = VRegDefs.find(Reg);
if (DefI == VRegDefs.end())
VRegDefs.insert(VReg2SUnit(Reg, SU));
else {
// Lookup this operand's reaching definition.
assert(LIS && "vreg dependencies requires LiveIntervals");
- SlotIndex UseIdx = LIS->getInstructionIndex(MI).getRegSlot();
- LiveInterval *LI = &LIS->getInterval(Reg);
- VNInfo *VNI = LI->getVNInfoBefore(UseIdx);
+ LiveRangeQuery LRQ(LIS->getInterval(Reg), LIS->getInstructionIndex(MI));
+ VNInfo *VNI = LRQ.valueIn();
+
// VNI will be valid because MachineOperand::readsReg() is checked by caller.
+ assert(VNI && "No value to read by operand");
MachineInstr *Def = LIS->getInstructionFromIndex(VNI->def);
// Phis and other noninstructions (after coalescing) have a NULL Def.
if (Def) {
// Create a data dependence.
//
// TODO: Handle "special" address latencies cleanly.
- const SDep &dep = SDep(DefSU, SDep::Data, DefSU->Latency, Reg);
+ SDep dep(DefSU, SDep::Data, DefSU->Latency, Reg);
if (!UnitLatencies) {
// Adjust the dependence latency using operand def/use information, then
// allow the target to perform its own adjustments.
- ComputeOperandLatency(DefSU, SU, const_cast<SDep &>(dep));
+ int DefOp = Def->findRegisterDefOperandIdx(Reg);
+ dep.setLatency(
+ SchedModel.computeOperandLatency(Def, DefOp, MI, OperIdx, false));
+ dep.setMinLatency(
+ SchedModel.computeOperandLatency(Def, DefOp, MI, OperIdx, true));
+
const TargetSubtargetInfo &ST = TM.getSubtarget<TargetSubtargetInfo>();
ST.adjustSchedDependency(DefSU, SU, const_cast<SDep &>(dep));
}
}
// Add antidependence to the following def of the vreg it uses.
- VReg2SUnitMap::iterator DefI = findVRegDef(Reg);
+ VReg2SUnitMap::iterator DefI = VRegDefs.find(Reg);
if (DefI != VRegDefs.end() && DefI->SU != SU)
DefI->SU->addPred(SDep(SU, SDep::Anti, 0, 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) {
+ if (MI->isCall() || MI->hasUnmodeledSideEffects() ||
+ (MI->hasOrderedMemoryRef() &&
+ (!MI->mayLoad() || !MI->isInvariantLoad(AA))))
+ return true;
+ return false;
+}
+
+// This MI might have either incomplete info, or known to be unsafe
+// to deal with (i.e. volatile object).
+static inline bool isUnsafeMemoryObject(MachineInstr *MI,
+ const MachineFrameInfo *MFI) {
+ if (!MI || MI->memoperands_empty())
+ return true;
+ // We purposefully do no check for hasOneMemOperand() here
+ // in hope to trigger an assert downstream in order to
+ // finish implementation.
+ if ((*MI->memoperands_begin())->isVolatile() ||
+ MI->hasUnmodeledSideEffects())
+ return true;
+
+ const Value *V = (*MI->memoperands_begin())->getValue();
+ if (!V)
+ return true;
+
+ V = getUnderlyingObject(V);
+ if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V)) {
+ // Similarly to getUnderlyingObjectForInstr:
+ // 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 true;
+ }
+ // Does this pointer refer to a distinct and identifiable object?
+ if (!isIdentifiedObject(V))
+ return true;
+
+ return false;
+}
+
+/// This returns true if the two MIs need a chain edge betwee them.
+/// If these are not even memory operations, we still may need
+/// chain deps between them. The question really is - could
+/// these two MIs be reordered during scheduling from memory dependency
+/// point of view.
+static bool MIsNeedChainEdge(AliasAnalysis *AA, const MachineFrameInfo *MFI,
+ MachineInstr *MIa,
+ MachineInstr *MIb) {
+ // Cover a trivial case - no edge is need to itself.
+ if (MIa == MIb)
+ return false;
+
+ if (isUnsafeMemoryObject(MIa, MFI) || isUnsafeMemoryObject(MIb, MFI))
+ return true;
+
+ // If we are dealing with two "normal" loads, we do not need an edge
+ // between them - they could be reordered.
+ if (!MIa->mayStore() && !MIb->mayStore())
+ return false;
+
+ // To this point analysis is generic. From here on we do need AA.
+ if (!AA)
+ return true;
+
+ MachineMemOperand *MMOa = *MIa->memoperands_begin();
+ MachineMemOperand *MMOb = *MIb->memoperands_begin();
+
+ // FIXME: Need to handle multiple memory operands to support all targets.
+ if (!MIa->hasOneMemOperand() || !MIb->hasOneMemOperand())
+ llvm_unreachable("Multiple memory operands.");
+
+ // 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;
+
+ AliasAnalysis::AliasResult AAResult = AA->alias(
+ AliasAnalysis::Location(MMOa->getValue(), Overlapa,
+ MMOa->getTBAAInfo()),
+ AliasAnalysis::Location(MMOb->getValue(), Overlapb,
+ MMOb->getTBAAInfo()));
+
+ return (AAResult != AliasAnalysis::NoAlias);
+}
+
+/// This recursive function iterates over chain deps of SUb looking for
+/// "latest" node that needs a chain edge to SUa.
+static unsigned
+iterateChainSucc(AliasAnalysis *AA, const MachineFrameInfo *MFI,
+ SUnit *SUa, SUnit *SUb, SUnit *ExitSU, unsigned *Depth,
+ SmallPtrSet<const SUnit*, 16> &Visited) {
+ if (!SUa || !SUb || SUb == ExitSU)
+ return *Depth;
+
+ // Remember visited nodes.
+ if (!Visited.insert(SUb))
+ return *Depth;
+ // If there is _some_ dependency already in place, do not
+ // descend any further.
+ // TODO: Need to make sure that if that dependency got eliminated or ignored
+ // for any reason in the future, we would not violate DAG topology.
+ // Currently it does not happen, but makes an implicit assumption about
+ // future implementation.
+ //
+ // Independently, if we encounter node that is some sort of global
+ // object (like a call) we already have full set of dependencies to it
+ // and we can stop descending.
+ if (SUa->isSucc(SUb) ||
+ isGlobalMemoryObject(AA, SUb->getInstr()))
+ return *Depth;
+
+ // If we do need an edge, or we have exceeded depth budget,
+ // add that edge to the predecessors chain of SUb,
+ // and stop descending.
+ if (*Depth > 200 ||
+ MIsNeedChainEdge(AA, MFI, SUa->getInstr(), SUb->getInstr())) {
+ SUb->addPred(SDep(SUa, SDep::Order, /*Latency=*/0, /*Reg=*/0,
+ /*isNormalMemory=*/true));
+ return *Depth;
+ }
+ // Track current depth.
+ (*Depth)++;
+ // Iterate over chain dependencies only.
+ for (SUnit::const_succ_iterator I = SUb->Succs.begin(), E = SUb->Succs.end();
+ I != E; ++I)
+ if (I->isCtrl())
+ iterateChainSucc (AA, MFI, SUa, I->getSUnit(), ExitSU, Depth, Visited);
+ return *Depth;
+}
+
+/// This function assumes that "downward" from SU there exist
+/// tail/leaf of already constructed DAG. It iterates downward and
+/// checks whether SU can be aliasing any node dominated
+/// by it.
+static void adjustChainDeps(AliasAnalysis *AA, const MachineFrameInfo *MFI,
+ SUnit *SU, SUnit *ExitSU, std::set<SUnit *> &CheckList,
+ unsigned LatencyToLoad) {
+ if (!SU)
+ return;
+
+ SmallPtrSet<const SUnit*, 16> Visited;
+ unsigned Depth = 0;
+
+ for (std::set<SUnit *>::iterator I = CheckList.begin(), IE = CheckList.end();
+ I != IE; ++I) {
+ if (SU == *I)
+ continue;
+ if (MIsNeedChainEdge(AA, MFI, SU->getInstr(), (*I)->getInstr())) {
+ unsigned Latency = ((*I)->getInstr()->mayLoad()) ? LatencyToLoad : 0;
+ (*I)->addPred(SDep(SU, SDep::Order, Latency, /*Reg=*/0,
+ /*isNormalMemory=*/true));
+ }
+ // Now go through all the chain successors and iterate from them.
+ // Keep track of visited nodes.
+ for (SUnit::const_succ_iterator J = (*I)->Succs.begin(),
+ JE = (*I)->Succs.end(); J != JE; ++J)
+ if (J->isCtrl())
+ iterateChainSucc (AA, MFI, SU, J->getSUnit(),
+ ExitSU, &Depth, Visited);
+ }
+}
+
+/// Check whether two objects need a chain edge, if so, add it
+/// otherwise remember the rejected SU.
+static inline
+void addChainDependency (AliasAnalysis *AA, const MachineFrameInfo *MFI,
+ SUnit *SUa, SUnit *SUb,
+ std::set<SUnit *> &RejectList,
+ unsigned TrueMemOrderLatency = 0,
+ bool isNormalMemory = false) {
+ // If this is a false dependency,
+ // do not add the edge, but rememeber the rejected node.
+ if (!EnableAASchedMI ||
+ MIsNeedChainEdge(AA, MFI, SUa->getInstr(), SUb->getInstr()))
+ SUb->addPred(SDep(SUa, SDep::Order, TrueMemOrderLatency, /*Reg=*/0,
+ isNormalMemory));
+ else {
+ // Duplicate entries should be ignored.
+ RejectList.insert(SUb);
+ DEBUG(dbgs() << "\tReject chain dep between SU("
+ << SUa->NodeNum << ") and SU("
+ << SUb->NodeNum << ")\n");
+ }
+}
+
/// Create an SUnit for each real instruction, numbered in top-down toplological
/// 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 is 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.
+/// 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(BB->size());
- for (MachineBasicBlock::iterator I = Begin; I != InsertPos; ++I) {
+ for (MachineBasicBlock::iterator I = RegionBegin; I != RegionEnd; ++I) {
MachineInstr *MI = I;
if (MI->isDebugValue())
continue;
- SUnit *SU = NewSUnit(MI);
+ SUnit *SU = newSUnit(MI);
MISUnitMap[MI] = SU;
SU->isCall = MI->isCall();
if (UnitLatencies)
SU->Latency = 1;
else
- ComputeLatency(SU);
+ computeLatency(SU);
}
}
-void ScheduleDAGInstrs::BuildSchedGraph(AliasAnalysis *AA) {
+/// 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) {
// Create an SUnit for each real instruction.
initSUnits();
// that are known not to alias
std::map<const Value *, SUnit *> AliasMemDefs, NonAliasMemDefs;
std::map<const Value *, std::vector<SUnit *> > AliasMemUses, NonAliasMemUses;
+ std::set<SUnit*> RejectMemNodes;
// Remove any stale debug info; sometimes BuildSchedGraph is called again
// without emitting the info from the previous call.
// Model data dependencies between instructions being scheduled and the
// ExitSU.
- AddSchedBarrierDeps();
+ addSchedBarrierDeps();
// Walk the list of instructions, from bottom moving up.
MachineInstr *PrevMI = NULL;
- for (MachineBasicBlock::iterator MII = InsertPos, MIE = Begin;
+ for (MachineBasicBlock::iterator MII = RegionEnd, MIE = RegionBegin;
MII != MIE; --MII) {
MachineInstr *MI = prior(MII);
if (MI && PrevMI) {
PrevMI = MI;
continue;
}
+ if (RPTracker) {
+ RPTracker->recede();
+ assert(RPTracker->getPos() == prior(MII) && "RPTracker can't find MI");
+ }
- assert(!MI->isTerminator() && !MI->isLabel() &&
+ assert((!MI->isTerminator() || CanHandleTerminators) && !MI->isLabel() &&
"Cannot schedule terminators or labels!");
SUnit *SU = MISUnitMap[MI];
// after stack slots are lowered to actual addresses.
// TODO: Use an AliasAnalysis and do real alias-analysis queries, and
// produce more precise dependence information.
-#define STORE_LOAD_LATENCY 1
- unsigned TrueMemOrderLatency = 0;
- if (MI->isCall() || MI->hasUnmodeledSideEffects() ||
- (MI->hasVolatileMemoryRef() &&
- (!MI->mayLoad() || !MI->isInvariantLoad(AA)))) {
+ unsigned TrueMemOrderLatency = MI->mayStore() ? 1 : 0;
+ if (isGlobalMemoryObject(AA, MI)) {
// Be conservative with these and add dependencies on all memory
// references, even those that are known to not alias.
for (std::map<const Value *, SUnit *>::iterator I =
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
I->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
}
- NonAliasMemDefs.clear();
- NonAliasMemUses.clear();
// Add SU to the barrier chain.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
BarrierChain = SU;
+ // This is a barrier event that acts as a pivotal node in the DAG,
+ // so it is safe to clear list of exposed nodes.
+ adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
+ TrueMemOrderLatency);
+ RejectMemNodes.clear();
+ NonAliasMemDefs.clear();
+ NonAliasMemUses.clear();
// fall-through
new_alias_chain:
// Chain all possibly aliasing memory references though SU.
- if (AliasChain)
- AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ if (AliasChain) {
+ unsigned ChainLatency = 0;
+ if (AliasChain->getInstr()->mayLoad())
+ ChainLatency = TrueMemOrderLatency;
+ addChainDependency(AA, MFI, SU, AliasChain, RejectMemNodes,
+ ChainLatency);
+ }
AliasChain = SU;
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
- PendingLoads[k]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
+ addChainDependency(AA, MFI, SU, PendingLoads[k], RejectMemNodes,
+ TrueMemOrderLatency);
for (std::map<const Value *, SUnit *>::iterator I = AliasMemDefs.begin(),
- E = AliasMemDefs.end(); I != E; ++I) {
- I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
- }
+ E = AliasMemDefs.end(); I != E; ++I)
+ addChainDependency(AA, MFI, SU, I->second, RejectMemNodes);
for (std::map<const Value *, std::vector<SUnit *> >::iterator I =
AliasMemUses.begin(), E = AliasMemUses.end(); I != E; ++I) {
for (unsigned i = 0, e = I->second.size(); i != e; ++i)
- I->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
+ addChainDependency(AA, MFI, SU, I->second[i], RejectMemNodes,
+ TrueMemOrderLatency);
}
+ adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
+ TrueMemOrderLatency);
PendingLoads.clear();
AliasMemDefs.clear();
AliasMemUses.clear();
} else if (MI->mayStore()) {
bool MayAlias = true;
- TrueMemOrderLatency = STORE_LOAD_LATENCY;
if (const Value *V = getUnderlyingObjectForInstr(MI, MFI, MayAlias)) {
// A store to a specific PseudoSourceValue. Add precise dependencies.
// Record the def in MemDefs, first adding a dep if there is
std::map<const Value *, SUnit *>::iterator IE =
((MayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE) {
- I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0, /*Reg=*/0,
- /*isNormalMemory=*/true));
+ addChainDependency(AA, MFI, SU, I->second, RejectMemNodes,
+ 0, true);
I->second = SU;
} else {
if (MayAlias)
((MayAlias) ? AliasMemUses.end() : NonAliasMemUses.end());
if (J != JE) {
for (unsigned i = 0, e = J->second.size(); i != e; ++i)
- J->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency,
- /*Reg=*/0, /*isNormalMemory=*/true));
+ addChainDependency(AA, MFI, SU, J->second[i], RejectMemNodes,
+ TrueMemOrderLatency, true);
J->second.clear();
}
if (MayAlias) {
// Add dependencies from all the PendingLoads, i.e. loads
// with no underlying object.
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
- PendingLoads[k]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
+ addChainDependency(AA, MFI, SU, PendingLoads[k], RejectMemNodes,
+ TrueMemOrderLatency);
// Add dependence on alias chain, if needed.
if (AliasChain)
- AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ addChainDependency(AA, MFI, SU, AliasChain, RejectMemNodes);
+ // But we also should check dependent instructions for the
+ // SU in question.
+ adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes,
+ TrueMemOrderLatency);
}
// Add dependence on barrier chain, if needed.
+ // There is no point to check aliasing on barrier event. Even if
+ // SU and barrier _could_ be reordered, they should not. In addition,
+ // we have lost all RejectMemNodes below barrier.
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
} else {
/*isArtificial=*/true));
} else if (MI->mayLoad()) {
bool MayAlias = true;
- TrueMemOrderLatency = 0;
if (MI->isInvariantLoad(AA)) {
// Invariant load, no chain dependencies needed!
} else {
std::map<const Value *, SUnit *>::iterator IE =
((MayAlias) ? AliasMemDefs.end() : NonAliasMemDefs.end());
if (I != IE)
- I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0, /*Reg=*/0,
- /*isNormalMemory=*/true));
+ addChainDependency(AA, MFI, SU, I->second, RejectMemNodes, 0, true);
if (MayAlias)
AliasMemUses[V].push_back(SU);
else
// potentially aliasing stores.
for (std::map<const Value *, SUnit *>::iterator I =
AliasMemDefs.begin(), E = AliasMemDefs.end(); I != E; ++I)
- I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ addChainDependency(AA, MFI, SU, I->second, RejectMemNodes);
PendingLoads.push_back(SU);
MayAlias = true;
}
-
+ if (MayAlias)
+ adjustChainDeps(AA, MFI, SU, &ExitSU, RejectMemNodes, /*Latency=*/0);
// Add dependencies on alias and barrier chains, if needed.
if (MayAlias && AliasChain)
- AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ addChainDependency(AA, MFI, SU, AliasChain, RejectMemNodes);
if (BarrierChain)
BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
}
Uses.clear();
VRegDefs.clear();
PendingLoads.clear();
- MISUnitMap.clear();
}
-void ScheduleDAGInstrs::FinishBlock() {
- // Nothing to do.
-}
-
-void ScheduleDAGInstrs::ComputeLatency(SUnit *SU) {
- // Compute the latency for the node.
- if (!InstrItins || InstrItins->isEmpty()) {
+void ScheduleDAGInstrs::computeLatency(SUnit *SU) {
+ // Compute the latency for the node. We only provide a default for missing
+ // itineraries. Empty itineraries still have latency properties.
+ if (!InstrItins) {
SU->Latency = 1;
// Simplistic target-independent heuristic: assume that loads take
}
}
-void ScheduleDAGInstrs::ComputeOperandLatency(SUnit *Def, SUnit *Use,
- SDep& dep) const {
- if (!InstrItins || InstrItins->isEmpty())
- return;
-
- // For a data dependency with a known register...
- if ((dep.getKind() != SDep::Data) || (dep.getReg() == 0))
- return;
-
- const unsigned Reg = dep.getReg();
-
- // ... find the definition of the register in the defining
- // instruction
- MachineInstr *DefMI = Def->getInstr();
- int DefIdx = DefMI->findRegisterDefOperandIdx(Reg);
- if (DefIdx != -1) {
- const MachineOperand &MO = DefMI->getOperand(DefIdx);
- if (MO.isReg() && MO.isImplicit() &&
- DefIdx >= (int)DefMI->getDesc().getNumOperands()) {
- // This is an implicit def, getOperandLatency() won't return the correct
- // latency. e.g.
- // %D6<def>, %D7<def> = VLD1q16 %R2<kill>, 0, ..., %Q3<imp-def>
- // %Q1<def> = VMULv8i16 %Q1<kill>, %Q3<kill>, ...
- // What we want is to compute latency between def of %D6/%D7 and use of
- // %Q3 instead.
- unsigned Op2 = DefMI->findRegisterDefOperandIdx(Reg, false, true, TRI);
- if (DefMI->getOperand(Op2).isReg())
- DefIdx = Op2;
- }
- MachineInstr *UseMI = Use->getInstr();
- // For all uses of the register, calculate the maxmimum latency
- int Latency = -1;
- if (UseMI) {
- for (unsigned i = 0, e = UseMI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = UseMI->getOperand(i);
- if (!MO.isReg() || !MO.isUse())
- continue;
- unsigned MOReg = MO.getReg();
- if (MOReg != Reg)
- continue;
-
- int UseCycle = TII->getOperandLatency(InstrItins, DefMI, DefIdx,
- UseMI, i);
- Latency = std::max(Latency, UseCycle);
- }
- } else {
- // UseMI is null, then it must be a scheduling barrier.
- if (!InstrItins || InstrItins->isEmpty())
- return;
- unsigned DefClass = DefMI->getDesc().getSchedClass();
- Latency = InstrItins->getOperandCycle(DefClass, DefIdx);
- }
-
- // If we found a latency, then replace the existing dependence latency.
- if (Latency >= 0)
- dep.setLatency(Latency);
- }
-}
-
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 {
return oss.str();
}
-// EmitSchedule - Emit the machine code in scheduled order.
-MachineBasicBlock *ScheduleDAGInstrs::EmitSchedule() {
- Begin = InsertPos;
-
- // If first instruction was a DBG_VALUE then put it back.
- if (FirstDbgValue)
- BB->splice(InsertPos, BB, FirstDbgValue);
-
- // Then re-insert them according to the given schedule.
- for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
- if (SUnit *SU = Sequence[i])
- BB->splice(InsertPos, BB, SU->getInstr());
- else
- // Null SUnit* is a noop.
- EmitNoop();
-
- // Update the Begin iterator, as the first instruction in the block
- // may have been scheduled later.
- if (i == 0)
- Begin = prior(InsertPos);
- }
-
- // Reinsert any remaining debug_values.
- for (std::vector<std::pair<MachineInstr *, MachineInstr *> >::iterator
- DI = DbgValues.end(), DE = DbgValues.begin(); DI != DE; --DI) {
- std::pair<MachineInstr *, MachineInstr *> P = *prior(DI);
- MachineInstr *DbgValue = P.first;
- MachineBasicBlock::iterator OrigPrivMI = P.second;
- BB->splice(++OrigPrivMI, BB, DbgValue);
- }
- DbgValues.clear();
- FirstDbgValue = NULL;
- return BB;
+/// 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();
}