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llvm-6502/lib/CodeGen/ScheduleDAGInstrs.cpp
Evan Cheng ec6906ba47 Properly model the latency of register defs which are 1) function returns or 
2) live-outs.

Previously the post-RA schedulers completely ignore these dependencies since
returns, branches, etc. are all scheduling barriers. This patch model the
latencies between instructions being scheduled and the barriers. It also
handle calls by marking their register uses.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117193 91177308-0d34-0410-b5e6-96231b3b80d8
2010-10-23 02:10:46 +00:00

684 lines
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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.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sched-instrs"
#include "ScheduleDAGInstrs.h"
#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"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetSubtarget.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallSet.h"
using namespace llvm;
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineFunction &mf,
const MachineLoopInfo &mli,
const MachineDominatorTree &mdt)
: ScheduleDAG(mf), MLI(mli), MDT(mdt), MFI(mf.getFrameInfo()),
InstrItins(mf.getTarget().getInstrItineraryData()),
Defs(TRI->getNumRegs()), Uses(TRI->getNumRegs()), LoopRegs(MLI, MDT) {
DbgValueVec.clear();
}
/// Run - perform scheduling.
///
void ScheduleDAGInstrs::Run(MachineBasicBlock *bb,
MachineBasicBlock::iterator begin,
MachineBasicBlock::iterator end,
unsigned endcount) {
BB = bb;
Begin = begin;
InsertPosIndex = endcount;
ScheduleDAG::Run(bb, end);
}
/// 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 or a multiplied value, 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
// identifibale object.
if (U->getOpcode() != Instruction::Add ||
(!isa<ConstantInt>(U->getOperand(1)) &&
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul))
return V;
V = U->getOperand(0);
} else {
return V;
}
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
} while (1);
}
/// getUnderlyingObject - This is a wrapper around Value::getUnderlyingObject
/// and adds support for basic ptrtoint+arithmetic+inttoptr sequences.
static const Value *getUnderlyingObject(const Value *V) {
// First just call Value::getUnderlyingObject to let it do what it does.
do {
V = V->getUnderlyingObject();
// If it found an inttoptr, use special code to continue climing.
if (Operator::getOpcode(V) != Instruction::IntToPtr)
break;
const Value *O = getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
// If that succeeded in finding a pointer, continue the search.
if (!O->getType()->isPointerTy())
break;
V = O;
} while (1);
return V;
}
/// 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,
const MachineFrameInfo *MFI,
bool &MayAlias) {
MayAlias = true;
if (!MI->hasOneMemOperand() ||
!(*MI->memoperands_begin())->getValue() ||
(*MI->memoperands_begin())->isVolatile())
return 0;
const Value *V = (*MI->memoperands_begin())->getValue();
if (!V)
return 0;
V = getUnderlyingObject(V);
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;
}
if (isIdentifiedObject(V))
return V;
return 0;
}
void ScheduleDAGInstrs::StartBlock(MachineBasicBlock *BB) {
if (MachineLoop *ML = MLI.getLoopFor(BB))
if (BB == ML->getLoopLatch()) {
MachineBasicBlock *Header = ML->getHeader();
for (MachineBasicBlock::livein_iterator I = Header->livein_begin(),
E = Header->livein_end(); I != E; ++I)
LoopLiveInRegs.insert(*I);
LoopRegs.VisitLoop(ML);
}
}
/// 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 = InsertPos != BB->end() ? &*InsertPos : 0;
ExitSU.setInstr(ExitMI);
bool AllDepKnown = ExitMI &&
(ExitMI->getDesc().isCall() || ExitMI->getDesc().isBarrier());
if (ExitMI && AllDepKnown) {
// If it's a call or a barrier, add dependencies on the defs and uses of
// instruction.
for (unsigned i = 0, e = ExitMI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = ExitMI->getOperand(i);
if (!MO.isReg() || MO.isDef()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
assert(TRI->isPhysicalRegister(Reg) && "Virtual register encountered!");
Uses[Reg].push_back(&ExitSU);
}
} else {
// For others, e.g. fallthrough, conditional branch, assume the exit
// uses all the registers.
for (int i = 0, e = TRI->getNumRegs(); i != e; ++i)
Uses[i].push_back(&ExitSU);
}
}
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.
SUnit *BarrierChain = 0, *AliasChain = 0;
// 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;
// Keep track of dangling debug references to registers.
std::vector<std::pair<MachineInstr*, unsigned> >
DanglingDebugValue(TRI->getNumRegs(),
std::make_pair(static_cast<MachineInstr*>(0), 0));
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
// Ask the target if address-backscheduling is desirable, and if so how much.
const TargetSubtarget &ST = TM.getSubtarget<TargetSubtarget>();
unsigned SpecialAddressLatency = ST.getSpecialAddressLatency();
// Remove any stale debug info; sometimes BuildSchedGraph is called again
// without emitting the info from the previous call.
DbgValueVec.clear();
// Model data dependencies between instructions being scheduled and the
// ExitSU.
AddSchedBarrierDeps();
// Walk the list of instructions, from bottom moving up.
for (MachineBasicBlock::iterator MII = InsertPos, MIE = Begin;
MII != MIE; --MII) {
MachineInstr *MI = prior(MII);
// DBG_VALUE does not have SUnit's built, so just remember these for later
// reinsertion.
if (MI->isDebugValue()) {
if (MI->getNumOperands()==3 && MI->getOperand(0).isReg() &&
MI->getOperand(0).getReg())
DanglingDebugValue[MI->getOperand(0).getReg()] =
std::make_pair(MI, DbgValueVec.size());
DbgValueVec.push_back(MI);
continue;
}
const TargetInstrDesc &TID = MI->getDesc();
assert(!TID.isTerminator() && !MI->isLabel() &&
"Cannot schedule terminators or labels!");
// Create the SUnit for this MI.
SUnit *SU = NewSUnit(MI);
// Assign the Latency field of SU using target-provided information.
if (UnitLatencies)
SU->Latency = 1;
else
ComputeLatency(SU);
// Add register-based dependencies (data, anti, and output).
for (unsigned j = 0, n = MI->getNumOperands(); j != n; ++j) {
const MachineOperand &MO = MI->getOperand(j);
if (!MO.isReg()) continue;
unsigned Reg = MO.getReg();
if (Reg == 0) continue;
assert(TRI->isPhysicalRegister(Reg) && "Virtual register encountered!");
if (MO.isDef() && DanglingDebugValue[Reg].first!=0) {
SU->DbgInstrList.push_back(DanglingDebugValue[Reg].first);
DbgValueVec[DanglingDebugValue[Reg].second] = 0;
DanglingDebugValue[Reg] = std::make_pair((MachineInstr*)0, 0);
}
std::vector<SUnit *> &UseList = Uses[Reg];
std::vector<SUnit *> &DefList = Defs[Reg];
// 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;
unsigned AOLatency = (Kind == SDep::Anti) ? 0 : 1;
for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
SUnit *DefSU = DefList[i];
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
!DefSU->getInstr()->registerDefIsDead(Reg)))
DefSU->addPred(SDep(SU, Kind, AOLatency, /*Reg=*/Reg));
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
std::vector<SUnit *> &DefList = Defs[*Alias];
for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
SUnit *DefSU = DefList[i];
if (DefSU == &ExitSU)
continue;
if (DefSU != SU &&
(Kind != SDep::Output || !MO.isDead() ||
!DefSU->getInstr()->registerDefIsDead(*Alias)))
DefSU->addPred(SDep(SU, Kind, AOLatency, /*Reg=*/ *Alias));
}
}
if (MO.isDef()) {
// Add any data dependencies.
unsigned DataLatency = SU->Latency;
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU == SU)
continue;
unsigned LDataLatency = DataLatency;
// Optionally add in a special extra latency for nodes that
// feed addresses.
// TODO: Do this for register aliases too.
// TODO: Perhaps we should get rid of
// SpecialAddressLatency and just move this into
// adjustSchedDependency for the targets that care about it.
if (SpecialAddressLatency != 0 && !UnitLatencies &&
UseSU != &ExitSU) {
MachineInstr *UseMI = UseSU->getInstr();
const TargetInstrDesc &UseTID = UseMI->getDesc();
int RegUseIndex = UseMI->findRegisterUseOperandIdx(Reg);
assert(RegUseIndex >= 0 && "UseMI doesn's use register!");
if (RegUseIndex >= 0 &&
(UseTID.mayLoad() || UseTID.mayStore()) &&
(unsigned)RegUseIndex < UseTID.getNumOperands() &&
UseTID.OpInfo[RegUseIndex].isLookupPtrRegClass())
LDataLatency += SpecialAddressLatency;
}
// 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, Reg);
if (!UnitLatencies) {
ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
}
UseSU->addPred(dep);
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
std::vector<SUnit *> &UseList = Uses[*Alias];
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU == SU)
continue;
const SDep& dep = SDep(SU, SDep::Data, DataLatency, *Alias);
if (!UnitLatencies) {
ComputeOperandLatency(SU, UseSU, const_cast<SDep &>(dep));
ST.adjustSchedDependency(SU, UseSU, const_cast<SDep &>(dep));
}
UseSU->addPred(dep);
}
}
// If a def is going to wrap back around to the top of the loop,
// backschedule it.
if (!UnitLatencies && DefList.empty()) {
LoopDependencies::LoopDeps::iterator I = LoopRegs.Deps.find(Reg);
if (I != LoopRegs.Deps.end()) {
const MachineOperand *UseMO = I->second.first;
unsigned Count = I->second.second;
const MachineInstr *UseMI = UseMO->getParent();
unsigned UseMOIdx = UseMO - &UseMI->getOperand(0);
const TargetInstrDesc &UseTID = UseMI->getDesc();
// TODO: If we knew the total depth of the region here, we could
// handle the case where the whole loop is inside the region but
// is large enough that the isScheduleHigh trick isn't needed.
if (UseMOIdx < UseTID.getNumOperands()) {
// Currently, we only support scheduling regions consisting of
// single basic blocks. Check to see if the instruction is in
// the same region by checking to see if it has the same parent.
if (UseMI->getParent() != MI->getParent()) {
unsigned Latency = SU->Latency;
if (UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass())
Latency += SpecialAddressLatency;
// This is a wild guess as to the portion of the latency which
// will be overlapped by work done outside the current
// scheduling region.
Latency -= std::min(Latency, Count);
// Add the artifical edge.
ExitSU.addPred(SDep(SU, SDep::Order, Latency,
/*Reg=*/0, /*isNormalMemory=*/false,
/*isMustAlias=*/false,
/*isArtificial=*/true));
} else if (SpecialAddressLatency > 0 &&
UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass()) {
// The entire loop body is within the current scheduling region
// and the latency of this operation is assumed to be greater
// than the latency of the loop.
// TODO: Recursively mark data-edge predecessors as
// isScheduleHigh too.
SU->isScheduleHigh = true;
}
}
LoopRegs.Deps.erase(I);
}
}
UseList.clear();
if (!MO.isDead())
DefList.clear();
DefList.push_back(SU);
} else {
UseList.push_back(SU);
}
}
// 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.
#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, 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 =
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));
}
PendingLoads.clear();
AliasMemDefs.clear();
AliasMemUses.clear();
} else if (TID.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
// 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 {
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 =
((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, TrueMemOrderLatency,
/*Reg=*/0, /*isNormalMemory=*/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));
// 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_alias_chain;
}
if (!ExitSU.isPred(SU))
// Push store's up a bit to avoid them getting in between cmp
// and branches.
ExitSU.addPred(SDep(SU, SDep::Order, 0,
/*Reg=*/0, /*isNormalMemory=*/false,
/*isMustAlias=*/false,
/*isArtificial=*/true));
} else if (TID.mayLoad()) {
bool MayAlias = true;
TrueMemOrderLatency = 0;
if (MI->isInvariantLoad(AA)) {
// Invariant load, no chain dependencies needed!
} else {
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));
}
}
}
for (int i = 0, e = TRI->getNumRegs(); i != e; ++i) {
Defs[i].clear();
Uses[i].clear();
}
PendingLoads.clear();
}
void ScheduleDAGInstrs::FinishBlock() {
// Nothing to do.
}
void ScheduleDAGInstrs::ComputeLatency(SUnit *SU) {
// Compute the latency for the node.
if (!InstrItins || InstrItins->isEmpty()) {
SU->Latency = 1;
// Simplistic target-independent heuristic: assume that loads take
// extra time.
if (SU->getInstr()->getDesc().mayLoad())
SU->Latency += 2;
} else
SU->Latency =
InstrItins->getStageLatency(SU->getInstr()->getDesc().getSchedClass());
}
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.
DefIdx = DefMI->findRegisterDefOperandIdx(Reg, false, true, TRI);
}
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 {
SU->getInstr()->dump();
}
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);
return oss.str();
}
// EmitSchedule - Emit the machine code in scheduled order.
MachineBasicBlock *ScheduleDAGInstrs::EmitSchedule() {
// For MachineInstr-based scheduling, we're rescheduling the instructions in
// the block, so start by removing them from the block.
while (Begin != InsertPos) {
MachineBasicBlock::iterator I = Begin;
++Begin;
BB->remove(I);
}
// First reinsert any remaining debug_values; these are either constants,
// or refer to live-in registers. The beginning of the block is the right
// place for the latter. The former might reasonably be placed elsewhere
// using some kind of ordering algorithm, but right now it doesn't matter.
for (int i = DbgValueVec.size()-1; i>=0; --i)
if (DbgValueVec[i])
BB->insert(InsertPos, DbgValueVec[i]);
// Then re-insert them according to the given schedule.
for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
SUnit *SU = Sequence[i];
if (!SU) {
// Null SUnit* is a noop.
EmitNoop();
continue;
}
BB->insert(InsertPos, SU->getInstr());
for (unsigned i = 0, e = SU->DbgInstrList.size() ; i < e ; ++i)
BB->insert(InsertPos, SU->DbgInstrList[i]);
}
// Update the Begin iterator, as the first instruction in the block
// may have been scheduled later.
if (!DbgValueVec.empty()) {
for (int i = DbgValueVec.size()-1; i>=0; --i)
if (DbgValueVec[i]!=0) {
Begin = DbgValueVec[DbgValueVec.size()-1];
break;
}
} else if (!Sequence.empty())
Begin = Sequence[0]->getInstr();
DbgValueVec.clear();
return BB;
}
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