#include "llvm/Operator.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
#include "llvm/Target/TargetMachine.h"
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
const MachineLoopInfo &mli,
const MachineDominatorTree &mdt)
- : ScheduleDAG(mf), MLI(mli), MDT(mdt), LoopRegs(MLI, MDT) {}
+ : ScheduleDAG(mf), MLI(mli), MDT(mdt), LoopRegs(MLI, MDT) {
+ MFI = mf.getFrameInfo();
+}
/// Run - perform scheduling.
///
/// getUnderlyingObjectForInstr - 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. Otherwise return null.
-static const Value *getUnderlyingObjectForInstr(const MachineInstr *MI) {
+static const Value *getUnderlyingObjectForInstr(const MachineInstr *MI,
+ const MachineFrameInfo *MFI,
+ bool &MayAlias) {
+ MayAlias = true;
if (!MI->hasOneMemOperand() ||
- !MI->memoperands_begin()->getValue() ||
- MI->memoperands_begin()->isVolatile())
+ !(*MI->memoperands_begin())->getValue() ||
+ (*MI->memoperands_begin())->isVolatile())
return 0;
- const Value *V = MI->memoperands_begin()->getValue();
+ const Value *V = (*MI->memoperands_begin())->getValue();
if (!V)
return 0;
V = getUnderlyingObject(V);
- if (!isa<PseudoSourceValue>(V) && !isIdentifiedObject(V))
- return 0;
+ if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V)) {
+ // 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 0;
+
+ MayAlias = PSV->mayAlias(MFI);
+ return V;
+ }
- return V;
+ if (isIdentifiedObject(V))
+ return V;
+
+ return 0;
}
void ScheduleDAGInstrs::StartBlock(MachineBasicBlock *BB) {
}
}
-void ScheduleDAGInstrs::BuildSchedGraph() {
+void ScheduleDAGInstrs::BuildSchedGraph(AliasAnalysis *AA) {
// We'll be allocating one SUnit for each instruction, plus one for
// the region exit node.
SUnits.reserve(BB->size());
// We build scheduling units by walking a block's instruction list from bottom
// to top.
- // Remember where a generic side-effecting instruction is as we procede. If
- // ChainMMO is null, this is assumed to have arbitrary side-effects. If
- // ChainMMO is non-null, then Chain makes only a single memory reference.
- SUnit *Chain = 0;
- MachineMemOperand *ChainMMO = 0;
+ // Remember where a generic side-effecting instruction is as we procede.
+ SUnit *BarrierChain = 0, *AliasChain = 0;
- // Memory references to specific known memory locations are tracked so that
- // they can be given more precise dependencies.
- std::map<const Value *, SUnit *> MemDefs;
- std::map<const Value *, std::vector<SUnit *> > MemUses;
+ // Memory references to specific known memory locations are tracked
+ // so that they can be given more precise dependencies. We track
+ // separately the known memory locations that may alias and those
+ // that are known not to alias
+ std::map<const Value *, SUnit *> AliasMemDefs, NonAliasMemDefs;
+ std::map<const Value *, std::vector<SUnit *> > AliasMemUses, NonAliasMemUses;
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
SUnit *DefSU = DefList[i];
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
- !DefSU->getInstr()->registerDefIsDead(Reg)))
+ !DefSU->getInstr()->registerDefIsDead(*Alias)))
DefSU->addPred(SDep(SU, Kind, AOLatency, /*Reg=*/ *Alias));
}
}
}
// Add chain dependencies.
+ // Chain dependencies used to enforce memory order should have
+ // latency of 0 (except for true dependency of Store followed by
+ // aliased Load... we estimate that with a single cycle of latency
+ // assuming the hardware will bypass)
// Note that isStoreToStackSlot and isLoadFromStackSLot are not usable
// after stack slots are lowered to actual addresses.
// TODO: Use an AliasAnalysis and do real alias-analysis queries, and
// produce more precise dependence information.
- if (TID.isCall() || TID.hasUnmodeledSideEffects()) {
- new_chain:
- // This is the conservative case. Add dependencies on all memory
- // references.
- if (Chain)
- Chain->addPred(SDep(SU, SDep::Order, SU->Latency));
- Chain = SU;
+#define STORE_LOAD_LATENCY 1
+ unsigned TrueMemOrderLatency = 0;
+ if (TID.isCall() || TID.hasUnmodeledSideEffects() ||
+ (MI->hasVolatileMemoryRef() &&
+ (!TID.mayLoad() || !MI->isInvariantLoad(AA)))) {
+ // 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 =
+ NonAliasMemDefs.begin(), E = NonAliasMemDefs.end(); I != E; ++I) {
+ I->second->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ }
+ for (std::map<const Value *, std::vector<SUnit *> >::iterator I =
+ NonAliasMemUses.begin(), E = NonAliasMemUses.end(); I != E; ++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;
+
+ // fall-through
+ new_alias_chain:
+ // Chain all possibly aliasing memory references though SU.
+ if (AliasChain)
+ AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ AliasChain = SU;
for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
- PendingLoads[k]->addPred(SDep(SU, SDep::Order, SU->Latency));
- PendingLoads.clear();
- for (std::map<const Value *, SUnit *>::iterator I = MemDefs.begin(),
- E = MemDefs.end(); I != E; ++I) {
- I->second->addPred(SDep(SU, SDep::Order, SU->Latency));
- I->second = SU;
+ PendingLoads[k]->addPred(SDep(SU, SDep::Order, 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));
}
for (std::map<const Value *, std::vector<SUnit *> >::iterator I =
- MemUses.begin(), E = MemUses.end(); I != E; ++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, SU->Latency));
- I->second.clear();
+ I->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency));
}
- // See if it is known to just have a single memory reference.
- MachineInstr *ChainMI = Chain->getInstr();
- const TargetInstrDesc &ChainTID = ChainMI->getDesc();
- if (!ChainTID.isCall() &&
- !ChainTID.hasUnmodeledSideEffects() &&
- ChainMI->hasOneMemOperand() &&
- !ChainMI->memoperands_begin()->isVolatile() &&
- ChainMI->memoperands_begin()->getValue())
- // We know that the Chain accesses one specific memory location.
- ChainMMO = &*ChainMI->memoperands_begin();
- else
- // Unknown memory accesses. Assume the worst.
- ChainMMO = 0;
+ PendingLoads.clear();
+ AliasMemDefs.clear();
+ AliasMemUses.clear();
} else if (TID.mayStore()) {
- if (const Value *V = getUnderlyingObjectForInstr(MI)) {
+ bool MayAlias = true;
+ TrueMemOrderLatency = STORE_LOAD_LATENCY;
+ if (const Value *V = getUnderlyingObjectForInstr(MI, MFI, MayAlias)) {
// A store to a specific PseudoSourceValue. Add precise dependencies.
- // Handle the def in MemDefs, if there is one.
- std::map<const Value *, SUnit *>::iterator I = MemDefs.find(V);
- if (I != MemDefs.end()) {
- I->second->addPred(SDep(SU, SDep::Order, SU->Latency, /*Reg=*/0,
+ // Record the def in MemDefs, first adding a dep if there is
+ // an existing def.
+ std::map<const Value *, SUnit *>::iterator I =
+ ((MayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
+ 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));
I->second = SU;
} else {
- MemDefs[V] = SU;
+ if (MayAlias)
+ AliasMemDefs[V] = SU;
+ else
+ NonAliasMemDefs[V] = SU;
}
// Handle the uses in MemUses, if there are any.
std::map<const Value *, std::vector<SUnit *> >::iterator J =
- MemUses.find(V);
- if (J != MemUses.end()) {
+ ((MayAlias) ? AliasMemUses.find(V) : NonAliasMemUses.find(V));
+ std::map<const Value *, std::vector<SUnit *> >::iterator JE =
+ ((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, SU->Latency, /*Reg=*/0,
- /*isNormalMemory=*/true));
+ J->second[i]->addPred(SDep(SU, SDep::Order, TrueMemOrderLatency,
+ /*Reg=*/0, /*isNormalMemory=*/true));
J->second.clear();
}
- // Add dependencies from all the PendingLoads, since without
- // memoperands we must assume they alias anything.
- for (unsigned k = 0, m = PendingLoads.size(); k != m; ++k)
- PendingLoads[k]->addPred(SDep(SU, SDep::Order, SU->Latency));
- // Add a general dependence too, if needed.
- if (Chain)
- Chain->addPred(SDep(SU, SDep::Order, SU->Latency));
- } else
+ 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));
+ // Add dependence on alias chain, if needed.
+ if (AliasChain)
+ AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ }
+ // Add dependence on barrier chain, if needed.
+ if (BarrierChain)
+ BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ } else {
// Treat all other stores conservatively.
- goto new_chain;
+ goto new_alias_chain;
+ }
} else if (TID.mayLoad()) {
- if (TII->isInvariantLoad(MI)) {
+ bool MayAlias = true;
+ TrueMemOrderLatency = 0;
+ if (MI->isInvariantLoad(AA)) {
// Invariant load, no chain dependencies needed!
- } else if (const Value *V = getUnderlyingObjectForInstr(MI)) {
- // A load from a specific PseudoSourceValue. Add precise dependencies.
- std::map<const Value *, SUnit *>::iterator I = MemDefs.find(V);
- if (I != MemDefs.end())
- I->second->addPred(SDep(SU, SDep::Order, SU->Latency, /*Reg=*/0,
- /*isNormalMemory=*/true));
- MemUses[V].push_back(SU);
-
- // Add a general dependence too, if needed.
- if (Chain && (!ChainMMO ||
- (ChainMMO->isStore() || ChainMMO->isVolatile())))
- Chain->addPred(SDep(SU, SDep::Order, SU->Latency));
- } else if (MI->hasVolatileMemoryRef()) {
- // Treat volatile loads conservatively. Note that this includes
- // cases where memoperand information is unavailable.
- goto new_chain;
} else {
- // A normal load. Depend on the general chain, as well as on
- // all stores. In the absense of MachineMemOperand information,
- // we can't even assume that the load doesn't alias well-behaved
- // memory locations.
- if (Chain)
- Chain->addPred(SDep(SU, SDep::Order, SU->Latency));
- for (std::map<const Value *, SUnit *>::iterator I = MemDefs.begin(),
- E = MemDefs.end(); I != E; ++I)
- I->second->addPred(SDep(SU, SDep::Order, SU->Latency));
- PendingLoads.push_back(SU);
- }
+ if (const Value *V =
+ getUnderlyingObjectForInstr(MI, MFI, MayAlias)) {
+ // A load from a specific PseudoSourceValue. Add precise dependencies.
+ std::map<const Value *, SUnit *>::iterator I =
+ ((MayAlias) ? AliasMemDefs.find(V) : NonAliasMemDefs.find(V));
+ 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));
+ if (MayAlias)
+ AliasMemUses[V].push_back(SU);
+ else
+ NonAliasMemUses[V].push_back(SU);
+ } else {
+ // A load with no underlying object. Depend on all
+ // 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));
+
+ PendingLoads.push_back(SU);
+ MayAlias = true;
+ }
+
+ // Add dependencies on alias and barrier chains, if needed.
+ if (MayAlias && AliasChain)
+ AliasChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ if (BarrierChain)
+ BarrierChain->addPred(SDep(SU, SDep::Order, /*Latency=*/0));
+ }
}
}
}
// EmitSchedule - Emit the machine code in scheduled order.
-MachineBasicBlock *ScheduleDAGInstrs::EmitSchedule() {
+MachineBasicBlock *ScheduleDAGInstrs::
+EmitSchedule(DenseMap<MachineBasicBlock*, MachineBasicBlock*> *EM) {
// For MachineInstr-based scheduling, we're rescheduling the instructions in
// the block, so start by removing them from the block.
while (Begin != InsertPos) {