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llvm-project/llvm/lib/Target/Hexagon/HexagonSubtarget.cpp

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//===- HexagonSubtarget.cpp - Hexagon Subtarget Information ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the Hexagon specific subclass of TargetSubtarget.
//
//===----------------------------------------------------------------------===//
#include "Hexagon.h"
#include "HexagonInstrInfo.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "MCTargetDesc/HexagonMCTargetDesc.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <cassert>
#include <map>
using namespace llvm;
#define DEBUG_TYPE "hexagon-subtarget"
#define GET_SUBTARGETINFO_CTOR
#define GET_SUBTARGETINFO_TARGET_DESC
#include "HexagonGenSubtargetInfo.inc"
static cl::opt<bool> EnableBSBSched("enable-bsb-sched",
cl::Hidden, cl::ZeroOrMore, cl::init(true));
static cl::opt<bool> EnableTCLatencySched("enable-tc-latency-sched",
cl::Hidden, cl::ZeroOrMore, cl::init(false));
static cl::opt<bool> EnableDotCurSched("enable-cur-sched",
cl::Hidden, cl::ZeroOrMore, cl::init(true),
cl::desc("Enable the scheduler to generate .cur"));
static cl::opt<bool> DisableHexagonMISched("disable-hexagon-misched",
cl::Hidden, cl::ZeroOrMore, cl::init(false),
cl::desc("Disable Hexagon MI Scheduling"));
static cl::opt<bool> EnableSubregLiveness("hexagon-subreg-liveness",
cl::Hidden, cl::ZeroOrMore, cl::init(true),
cl::desc("Enable subregister liveness tracking for Hexagon"));
static cl::opt<bool> OverrideLongCalls("hexagon-long-calls",
cl::Hidden, cl::ZeroOrMore, cl::init(false),
cl::desc("If present, forces/disables the use of long calls"));
static cl::opt<bool> EnablePredicatedCalls("hexagon-pred-calls",
cl::Hidden, cl::ZeroOrMore, cl::init(false),
cl::desc("Consider calls to be predicable"));
static cl::opt<bool> SchedPredsCloser("sched-preds-closer",
cl::Hidden, cl::ZeroOrMore, cl::init(true));
static cl::opt<bool> SchedRetvalOptimization("sched-retval-optimization",
cl::Hidden, cl::ZeroOrMore, cl::init(true));
static cl::opt<bool> EnableCheckBankConflict("hexagon-check-bank-conflict",
cl::Hidden, cl::ZeroOrMore, cl::init(true),
cl::desc("Enable checking for cache bank conflicts"));
HexagonSubtarget::HexagonSubtarget(const Triple &TT, StringRef CPU,
StringRef FS, const TargetMachine &TM)
: HexagonGenSubtargetInfo(TT, CPU, FS), OptLevel(TM.getOptLevel()),
CPUString(std::string(Hexagon_MC::selectHexagonCPU(CPU))),
TargetTriple(TT), InstrInfo(initializeSubtargetDependencies(CPU, FS)),
RegInfo(getHwMode()), TLInfo(TM, *this),
InstrItins(getInstrItineraryForCPU(CPUString)) {
Hexagon_MC::addArchSubtarget(this, FS);
// Beware of the default constructor of InstrItineraryData: it will
// reset all members to 0.
assert(InstrItins.Itineraries != nullptr && "InstrItins not initialized");
}
HexagonSubtarget &
HexagonSubtarget::initializeSubtargetDependencies(StringRef CPU, StringRef FS) {
Optional<Hexagon::ArchEnum> ArchVer =
Hexagon::GetCpu(Hexagon::CpuTable, CPUString);
if (ArchVer)
HexagonArchVersion = *ArchVer;
else
llvm_unreachable("Unrecognized Hexagon processor version");
UseHVX128BOps = false;
UseHVX64BOps = false;
UseAudioOps = false;
UseLongCalls = false;
UseBSBScheduling = hasV60Ops() && EnableBSBSched;
ParseSubtargetFeatures(CPUString, FS);
if (OverrideLongCalls.getPosition())
UseLongCalls = OverrideLongCalls;
if (isTinyCore()) {
// Tiny core has a single thread, so back-to-back scheduling is enabled by
// default.
if (!EnableBSBSched.getPosition())
UseBSBScheduling = false;
}
FeatureBitset Features = getFeatureBits();
if (HexagonDisableDuplex)
setFeatureBits(Features.reset(Hexagon::FeatureDuplex));
setFeatureBits(Hexagon_MC::completeHVXFeatures(Features));
return *this;
}
void HexagonSubtarget::UsrOverflowMutation::apply(ScheduleDAGInstrs *DAG) {
for (SUnit &SU : DAG->SUnits) {
if (!SU.isInstr())
continue;
SmallVector<SDep, 4> Erase;
for (auto &D : SU.Preds)
if (D.getKind() == SDep::Output && D.getReg() == Hexagon::USR_OVF)
Erase.push_back(D);
for (auto &E : Erase)
SU.removePred(E);
}
}
void HexagonSubtarget::HVXMemLatencyMutation::apply(ScheduleDAGInstrs *DAG) {
for (SUnit &SU : DAG->SUnits) {
// Update the latency of chain edges between v60 vector load or store
// instructions to be 1. These instruction cannot be scheduled in the
// same packet.
MachineInstr &MI1 = *SU.getInstr();
auto *QII = static_cast<const HexagonInstrInfo*>(DAG->TII);
bool IsStoreMI1 = MI1.mayStore();
bool IsLoadMI1 = MI1.mayLoad();
if (!QII->isHVXVec(MI1) || !(IsStoreMI1 || IsLoadMI1))
continue;
for (SDep &SI : SU.Succs) {
if (SI.getKind() != SDep::Order || SI.getLatency() != 0)
continue;
MachineInstr &MI2 = *SI.getSUnit()->getInstr();
if (!QII->isHVXVec(MI2))
continue;
if ((IsStoreMI1 && MI2.mayStore()) || (IsLoadMI1 && MI2.mayLoad())) {
SI.setLatency(1);
SU.setHeightDirty();
// Change the dependence in the opposite direction too.
for (SDep &PI : SI.getSUnit()->Preds) {
if (PI.getSUnit() != &SU || PI.getKind() != SDep::Order)
continue;
PI.setLatency(1);
SI.getSUnit()->setDepthDirty();
}
}
}
}
}
// Check if a call and subsequent A2_tfrpi instructions should maintain
// scheduling affinity. We are looking for the TFRI to be consumed in
// the next instruction. This should help reduce the instances of
// double register pairs being allocated and scheduled before a call
// when not used until after the call. This situation is exacerbated
// by the fact that we allocate the pair from the callee saves list,
// leading to excess spills and restores.
bool HexagonSubtarget::CallMutation::shouldTFRICallBind(
const HexagonInstrInfo &HII, const SUnit &Inst1,
const SUnit &Inst2) const {
if (Inst1.getInstr()->getOpcode() != Hexagon::A2_tfrpi)
return false;
// TypeXTYPE are 64 bit operations.
unsigned Type = HII.getType(*Inst2.getInstr());
return Type == HexagonII::TypeS_2op || Type == HexagonII::TypeS_3op ||
Type == HexagonII::TypeALU64 || Type == HexagonII::TypeM;
}
void HexagonSubtarget::CallMutation::apply(ScheduleDAGInstrs *DAGInstrs) {
ScheduleDAGMI *DAG = static_cast<ScheduleDAGMI*>(DAGInstrs);
SUnit* LastSequentialCall = nullptr;
// Map from virtual register to physical register from the copy.
DenseMap<unsigned, unsigned> VRegHoldingReg;
// Map from the physical register to the instruction that uses virtual
// register. This is used to create the barrier edge.
DenseMap<unsigned, SUnit *> LastVRegUse;
auto &TRI = *DAG->MF.getSubtarget().getRegisterInfo();
auto &HII = *DAG->MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
// Currently we only catch the situation when compare gets scheduled
// before preceding call.
for (unsigned su = 0, e = DAG->SUnits.size(); su != e; ++su) {
// Remember the call.
if (DAG->SUnits[su].getInstr()->isCall())
LastSequentialCall = &DAG->SUnits[su];
// Look for a compare that defines a predicate.
else if (DAG->SUnits[su].getInstr()->isCompare() && LastSequentialCall)
DAG->addEdge(&DAG->SUnits[su], SDep(LastSequentialCall, SDep::Barrier));
// Look for call and tfri* instructions.
else if (SchedPredsCloser && LastSequentialCall && su > 1 && su < e-1 &&
shouldTFRICallBind(HII, DAG->SUnits[su], DAG->SUnits[su+1]))
DAG->addEdge(&DAG->SUnits[su], SDep(&DAG->SUnits[su-1], SDep::Barrier));
// Prevent redundant register copies due to reads and writes of physical
// registers. The original motivation for this was the code generated
// between two calls, which are caused both the return value and the
// argument for the next call being in %r0.
// Example:
// 1: <call1>
// 2: %vreg = COPY %r0
// 3: <use of %vreg>
// 4: %r0 = ...
// 5: <call2>
// The scheduler would often swap 3 and 4, so an additional register is
// needed. This code inserts a Barrier dependence between 3 & 4 to prevent
// this.
// The code below checks for all the physical registers, not just R0/D0/V0.
else if (SchedRetvalOptimization) {
const MachineInstr *MI = DAG->SUnits[su].getInstr();
if (MI->isCopy() &&
Register::isPhysicalRegister(MI->getOperand(1).getReg())) {
// %vregX = COPY %r0
VRegHoldingReg[MI->getOperand(0).getReg()] = MI->getOperand(1).getReg();
LastVRegUse.erase(MI->getOperand(1).getReg());
} else {
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
if (MO.isUse() && !MI->isCopy() &&
VRegHoldingReg.count(MO.getReg())) {
// <use of %vregX>
LastVRegUse[VRegHoldingReg[MO.getReg()]] = &DAG->SUnits[su];
} else if (MO.isDef() && Register::isPhysicalRegister(MO.getReg())) {
for (MCRegAliasIterator AI(MO.getReg(), &TRI, true); AI.isValid();
++AI) {
if (LastVRegUse.count(*AI) &&
LastVRegUse[*AI] != &DAG->SUnits[su])
// %r0 = ...
DAG->addEdge(&DAG->SUnits[su], SDep(LastVRegUse[*AI], SDep::Barrier));
LastVRegUse.erase(*AI);
}
}
}
}
}
}
}
void HexagonSubtarget::BankConflictMutation::apply(ScheduleDAGInstrs *DAG) {
if (!EnableCheckBankConflict)
return;
const auto &HII = static_cast<const HexagonInstrInfo&>(*DAG->TII);
// Create artificial edges between loads that could likely cause a bank
// conflict. Since such loads would normally not have any dependency
// between them, we cannot rely on existing edges.
for (unsigned i = 0, e = DAG->SUnits.size(); i != e; ++i) {
SUnit &S0 = DAG->SUnits[i];
MachineInstr &L0 = *S0.getInstr();
if (!L0.mayLoad() || L0.mayStore() ||
HII.getAddrMode(L0) != HexagonII::BaseImmOffset)
continue;
int64_t Offset0;
unsigned Size0;
MachineOperand *BaseOp0 = HII.getBaseAndOffset(L0, Offset0, Size0);
// Is the access size is longer than the L1 cache line, skip the check.
if (BaseOp0 == nullptr || !BaseOp0->isReg() || Size0 >= 32)
continue;
// Scan only up to 32 instructions ahead (to avoid n^2 complexity).
for (unsigned j = i+1, m = std::min(i+32, e); j != m; ++j) {
SUnit &S1 = DAG->SUnits[j];
MachineInstr &L1 = *S1.getInstr();
if (!L1.mayLoad() || L1.mayStore() ||
HII.getAddrMode(L1) != HexagonII::BaseImmOffset)
continue;
int64_t Offset1;
unsigned Size1;
MachineOperand *BaseOp1 = HII.getBaseAndOffset(L1, Offset1, Size1);
if (BaseOp1 == nullptr || !BaseOp1->isReg() || Size1 >= 32 ||
BaseOp0->getReg() != BaseOp1->getReg())
continue;
// Check bits 3 and 4 of the offset: if they differ, a bank conflict
// is unlikely.
if (((Offset0 ^ Offset1) & 0x18) != 0)
continue;
// Bits 3 and 4 are the same, add an artificial edge and set extra
// latency.
SDep A(&S0, SDep::Artificial);
A.setLatency(1);
S1.addPred(A, true);
}
}
}
/// Enable use of alias analysis during code generation (during MI
/// scheduling, DAGCombine, etc.).
bool HexagonSubtarget::useAA() const {
if (OptLevel != CodeGenOpt::None)
return true;
return false;
}
/// Perform target specific adjustments to the latency of a schedule
/// dependency.
void HexagonSubtarget::adjustSchedDependency(SUnit *Src, int SrcOpIdx,
SUnit *Dst, int DstOpIdx,
SDep &Dep) const {
if (!Src->isInstr() || !Dst->isInstr())
return;
MachineInstr *SrcInst = Src->getInstr();
MachineInstr *DstInst = Dst->getInstr();
const HexagonInstrInfo *QII = getInstrInfo();
// Instructions with .new operands have zero latency.
SmallSet<SUnit *, 4> ExclSrc;
SmallSet<SUnit *, 4> ExclDst;
if (QII->canExecuteInBundle(*SrcInst, *DstInst) &&
isBestZeroLatency(Src, Dst, QII, ExclSrc, ExclDst)) {
Dep.setLatency(0);
return;
}
if (!hasV60Ops())
return;
// Set the latency for a copy to zero since we hope that is will get removed.
if (DstInst->isCopy())
Dep.setLatency(0);
// If it's a REG_SEQUENCE/COPY, use its destination instruction to determine
// the correct latency.
if ((DstInst->isRegSequence() || DstInst->isCopy()) && Dst->NumSuccs == 1) {
Register DReg = DstInst->getOperand(0).getReg();
MachineInstr *DDst = Dst->Succs[0].getSUnit()->getInstr();
unsigned UseIdx = -1;
for (unsigned OpNum = 0; OpNum < DDst->getNumOperands(); OpNum++) {
const MachineOperand &MO = DDst->getOperand(OpNum);
if (MO.isReg() && MO.getReg() && MO.isUse() && MO.getReg() == DReg) {
UseIdx = OpNum;
break;
}
}
int DLatency = (InstrInfo.getOperandLatency(&InstrItins, *SrcInst,
0, *DDst, UseIdx));
DLatency = std::max(DLatency, 0);
Dep.setLatency((unsigned)DLatency);
}
// Try to schedule uses near definitions to generate .cur.
ExclSrc.clear();
ExclDst.clear();
if (EnableDotCurSched && QII->isToBeScheduledASAP(*SrcInst, *DstInst) &&
isBestZeroLatency(Src, Dst, QII, ExclSrc, ExclDst)) {
Dep.setLatency(0);
return;
}
updateLatency(*SrcInst, *DstInst, Dep);
}
void HexagonSubtarget::getPostRAMutations(
std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
Mutations.push_back(std::make_unique<UsrOverflowMutation>());
Mutations.push_back(std::make_unique<HVXMemLatencyMutation>());
Mutations.push_back(std::make_unique<BankConflictMutation>());
}
void HexagonSubtarget::getSMSMutations(
std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
Mutations.push_back(std::make_unique<UsrOverflowMutation>());
Mutations.push_back(std::make_unique<HVXMemLatencyMutation>());
}
// Pin the vtable to this file.
void HexagonSubtarget::anchor() {}
bool HexagonSubtarget::enableMachineScheduler() const {
if (DisableHexagonMISched.getNumOccurrences())
return !DisableHexagonMISched;
return true;
}
bool HexagonSubtarget::usePredicatedCalls() const {
return EnablePredicatedCalls;
}
void HexagonSubtarget::updateLatency(MachineInstr &SrcInst,
MachineInstr &DstInst, SDep &Dep) const {
if (Dep.isArtificial()) {
Dep.setLatency(1);
return;
}
if (!hasV60Ops())
return;
auto &QII = static_cast<const HexagonInstrInfo&>(*getInstrInfo());
// BSB scheduling.
if (QII.isHVXVec(SrcInst) || useBSBScheduling())
Dep.setLatency((Dep.getLatency() + 1) >> 1);
}
void HexagonSubtarget::restoreLatency(SUnit *Src, SUnit *Dst) const {
MachineInstr *SrcI = Src->getInstr();
for (auto &I : Src->Succs) {
if (!I.isAssignedRegDep() || I.getSUnit() != Dst)
continue;
unsigned DepR = I.getReg();
int DefIdx = -1;
for (unsigned OpNum = 0; OpNum < SrcI->getNumOperands(); OpNum++) {
const MachineOperand &MO = SrcI->getOperand(OpNum);
bool IsSameOrSubReg = false;
if (MO.isReg()) {
unsigned MOReg = MO.getReg();
if (Register::isVirtualRegister(DepR)) {
IsSameOrSubReg = (MOReg == DepR);
} else {
IsSameOrSubReg = getRegisterInfo()->isSubRegisterEq(DepR, MOReg);
}
if (MO.isDef() && IsSameOrSubReg)
DefIdx = OpNum;
}
}
assert(DefIdx >= 0 && "Def Reg not found in Src MI");
MachineInstr *DstI = Dst->getInstr();
SDep T = I;
for (unsigned OpNum = 0; OpNum < DstI->getNumOperands(); OpNum++) {
const MachineOperand &MO = DstI->getOperand(OpNum);
if (MO.isReg() && MO.isUse() && MO.getReg() == DepR) {
int Latency = (InstrInfo.getOperandLatency(&InstrItins, *SrcI,
DefIdx, *DstI, OpNum));
// For some instructions (ex: COPY), we might end up with < 0 latency
// as they don't have any Itinerary class associated with them.
Latency = std::max(Latency, 0);
I.setLatency(Latency);
updateLatency(*SrcI, *DstI, I);
}
}
// Update the latency of opposite edge too.
T.setSUnit(Src);
auto F = std::find(Dst->Preds.begin(), Dst->Preds.end(), T);
assert(F != Dst->Preds.end());
F->setLatency(I.getLatency());
}
}
/// Change the latency between the two SUnits.
void HexagonSubtarget::changeLatency(SUnit *Src, SUnit *Dst, unsigned Lat)
const {
for (auto &I : Src->Succs) {
if (!I.isAssignedRegDep() || I.getSUnit() != Dst)
continue;
SDep T = I;
I.setLatency(Lat);
// Update the latency of opposite edge too.
T.setSUnit(Src);
auto F = std::find(Dst->Preds.begin(), Dst->Preds.end(), T);
assert(F != Dst->Preds.end());
F->setLatency(Lat);
}
}
/// If the SUnit has a zero latency edge, return the other SUnit.
static SUnit *getZeroLatency(SUnit *N, SmallVector<SDep, 4> &Deps) {
for (auto &I : Deps)
if (I.isAssignedRegDep() && I.getLatency() == 0 &&
!I.getSUnit()->getInstr()->isPseudo())
return I.getSUnit();
return nullptr;
}
// Return true if these are the best two instructions to schedule
// together with a zero latency. Only one dependence should have a zero
// latency. If there are multiple choices, choose the best, and change
// the others, if needed.
bool HexagonSubtarget::isBestZeroLatency(SUnit *Src, SUnit *Dst,
const HexagonInstrInfo *TII, SmallSet<SUnit*, 4> &ExclSrc,
SmallSet<SUnit*, 4> &ExclDst) const {
MachineInstr &SrcInst = *Src->getInstr();
MachineInstr &DstInst = *Dst->getInstr();
// Ignore Boundary SU nodes as these have null instructions.
if (Dst->isBoundaryNode())
return false;
if (SrcInst.isPHI() || DstInst.isPHI())
return false;
if (!TII->isToBeScheduledASAP(SrcInst, DstInst) &&
!TII->canExecuteInBundle(SrcInst, DstInst))
return false;
// The architecture doesn't allow three dependent instructions in the same
// packet. So, if the destination has a zero latency successor, then it's
// not a candidate for a zero latency predecessor.
if (getZeroLatency(Dst, Dst->Succs) != nullptr)
return false;
// Check if the Dst instruction is the best candidate first.
SUnit *Best = nullptr;
SUnit *DstBest = nullptr;
SUnit *SrcBest = getZeroLatency(Dst, Dst->Preds);
if (SrcBest == nullptr || Src->NodeNum >= SrcBest->NodeNum) {
// Check that Src doesn't have a better candidate.
DstBest = getZeroLatency(Src, Src->Succs);
if (DstBest == nullptr || Dst->NodeNum <= DstBest->NodeNum)
Best = Dst;
}
if (Best != Dst)
return false;
// The caller frequently adds the same dependence twice. If so, then
// return true for this case too.
if ((Src == SrcBest && Dst == DstBest ) ||
(SrcBest == nullptr && Dst == DstBest) ||
(Src == SrcBest && Dst == nullptr))
return true;
// Reassign the latency for the previous bests, which requires setting
// the dependence edge in both directions.
if (SrcBest != nullptr) {
if (!hasV60Ops())
changeLatency(SrcBest, Dst, 1);
else
restoreLatency(SrcBest, Dst);
}
if (DstBest != nullptr) {
if (!hasV60Ops())
changeLatency(Src, DstBest, 1);
else
restoreLatency(Src, DstBest);
}
// Attempt to find another opprotunity for zero latency in a different
// dependence.
if (SrcBest && DstBest)
// If there is an edge from SrcBest to DstBst, then try to change that
// to 0 now.
changeLatency(SrcBest, DstBest, 0);
else if (DstBest) {
// Check if the previous best destination instruction has a new zero
// latency dependence opportunity.
ExclSrc.insert(Src);
for (auto &I : DstBest->Preds)
if (ExclSrc.count(I.getSUnit()) == 0 &&
isBestZeroLatency(I.getSUnit(), DstBest, TII, ExclSrc, ExclDst))
changeLatency(I.getSUnit(), DstBest, 0);
} else if (SrcBest) {
// Check if previous best source instruction has a new zero latency
// dependence opportunity.
ExclDst.insert(Dst);
for (auto &I : SrcBest->Succs)
if (ExclDst.count(I.getSUnit()) == 0 &&
isBestZeroLatency(SrcBest, I.getSUnit(), TII, ExclSrc, ExclDst))
changeLatency(SrcBest, I.getSUnit(), 0);
}
return true;
}
unsigned HexagonSubtarget::getL1CacheLineSize() const {
return 32;
}
unsigned HexagonSubtarget::getL1PrefetchDistance() const {
return 32;
}
bool HexagonSubtarget::enableSubRegLiveness() const {
return EnableSubregLiveness;
}
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