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llvm-project/llvm/lib/Target/PowerPC/PPCHazardRecognizers.cpp

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//===-- PPCHazardRecognizers.cpp - PowerPC Hazard Recognizer Impls --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements hazard recognizers for scheduling on PowerPC processors.
//
//===----------------------------------------------------------------------===//
#include "PPCHazardRecognizers.h"
#include "PPC.h"
#include "PPCInstrInfo.h"
#include "PPCTargetMachine.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "pre-RA-sched"
bool PPCDispatchGroupSBHazardRecognizer::isLoadAfterStore(SUnit *SU) {
// FIXME: Move this.
if (isBCTRAfterSet(SU))
return true;
const MCInstrDesc *MCID = DAG->getInstrDesc(SU);
if (!MCID)
return false;
if (!MCID->mayLoad())
return false;
// SU is a load; for any predecessors in this dispatch group, that are stores,
// and with which we have an ordering dependency, return true.
for (unsigned i = 0, ie = (unsigned) SU->Preds.size(); i != ie; ++i) {
const MCInstrDesc *PredMCID = DAG->getInstrDesc(SU->Preds[i].getSUnit());
if (!PredMCID || !PredMCID->mayStore())
continue;
if (!SU->Preds[i].isNormalMemory() && !SU->Preds[i].isBarrier())
continue;
for (unsigned j = 0, je = CurGroup.size(); j != je; ++j)
if (SU->Preds[i].getSUnit() == CurGroup[j])
return true;
}
return false;
}
bool PPCDispatchGroupSBHazardRecognizer::isBCTRAfterSet(SUnit *SU) {
const MCInstrDesc *MCID = DAG->getInstrDesc(SU);
if (!MCID)
return false;
if (!MCID->isBranch())
return false;
// SU is a branch; for any predecessors in this dispatch group, with which we
// have a data dependence and set the counter register, return true.
for (unsigned i = 0, ie = (unsigned) SU->Preds.size(); i != ie; ++i) {
const MCInstrDesc *PredMCID = DAG->getInstrDesc(SU->Preds[i].getSUnit());
if (!PredMCID || PredMCID->getSchedClass() != PPC::Sched::IIC_SprMTSPR)
continue;
if (SU->Preds[i].isCtrl())
continue;
for (unsigned j = 0, je = CurGroup.size(); j != je; ++j)
if (SU->Preds[i].getSUnit() == CurGroup[j])
return true;
}
return false;
}
// FIXME: Remove this when we don't need this:
namespace llvm { namespace PPC { extern int getNonRecordFormOpcode(uint16_t); } }
// FIXME: A lot of code in PPCDispatchGroupSBHazardRecognizer is P7 specific.
bool PPCDispatchGroupSBHazardRecognizer::mustComeFirst(const MCInstrDesc *MCID,
unsigned &NSlots) {
// FIXME: Indirectly, this information is contained in the itinerary, and
// we should derive it from there instead of separately specifying it
// here.
unsigned IIC = MCID->getSchedClass();
switch (IIC) {
default:
NSlots = 1;
break;
case PPC::Sched::IIC_IntDivW:
case PPC::Sched::IIC_IntDivD:
case PPC::Sched::IIC_LdStLoadUpd:
case PPC::Sched::IIC_LdStLDU:
case PPC::Sched::IIC_LdStLFDU:
case PPC::Sched::IIC_LdStLFDUX:
case PPC::Sched::IIC_LdStLHA:
case PPC::Sched::IIC_LdStLHAU:
case PPC::Sched::IIC_LdStLWA:
case PPC::Sched::IIC_LdStSTDU:
case PPC::Sched::IIC_LdStSTFDU:
NSlots = 2;
break;
case PPC::Sched::IIC_LdStLoadUpdX:
case PPC::Sched::IIC_LdStLDUX:
case PPC::Sched::IIC_LdStLHAUX:
case PPC::Sched::IIC_LdStLWARX:
case PPC::Sched::IIC_LdStLDARX:
case PPC::Sched::IIC_LdStSTDUX:
case PPC::Sched::IIC_LdStSTDCX:
case PPC::Sched::IIC_LdStSTWCX:
case PPC::Sched::IIC_BrMCRX: // mtcr
// FIXME: Add sync/isync (here and in the itinerary).
NSlots = 4;
break;
}
// FIXME: record-form instructions need a different itinerary class.
if (NSlots == 1 && PPC::getNonRecordFormOpcode(MCID->getOpcode()) != -1)
NSlots = 2;
switch (IIC) {
default:
// All multi-slot instructions must come first.
return NSlots > 1;
case PPC::Sched::IIC_BrCR: // cr logicals
case PPC::Sched::IIC_SprMFCR:
case PPC::Sched::IIC_SprMFCRF:
case PPC::Sched::IIC_SprMTSPR:
return true;
}
}
ScheduleHazardRecognizer::HazardType
PPCDispatchGroupSBHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
if (Stalls == 0 && isLoadAfterStore(SU))
return NoopHazard;
return ScoreboardHazardRecognizer::getHazardType(SU, Stalls);
}
bool PPCDispatchGroupSBHazardRecognizer::ShouldPreferAnother(SUnit *SU) {
const MCInstrDesc *MCID = DAG->getInstrDesc(SU);
unsigned NSlots;
if (MCID && mustComeFirst(MCID, NSlots) && CurSlots)
return true;
return ScoreboardHazardRecognizer::ShouldPreferAnother(SU);
}
unsigned PPCDispatchGroupSBHazardRecognizer::PreEmitNoops(SUnit *SU) {
// We only need to fill out a maximum of 5 slots here: The 6th slot could
// only be a second branch, and otherwise the next instruction will start a
// new group.
if (isLoadAfterStore(SU) && CurSlots < 6) {
unsigned Directive =
DAG->MF.getSubtarget<PPCSubtarget>().getDarwinDirective();
// If we're using a special group-terminating nop, then we need only one.
// FIXME: the same for P9 as previous gen until POWER9 scheduling is ready
if (Directive == PPC::DIR_PWR6 || Directive == PPC::DIR_PWR7 ||
Directive == PPC::DIR_PWR8 || Directive == PPC::DIR_PWR9)
return 1;
return 5 - CurSlots;
}
return ScoreboardHazardRecognizer::PreEmitNoops(SU);
}
void PPCDispatchGroupSBHazardRecognizer::EmitInstruction(SUnit *SU) {
const MCInstrDesc *MCID = DAG->getInstrDesc(SU);
if (MCID) {
if (CurSlots == 5 || (MCID->isBranch() && CurBranches == 1)) {
CurGroup.clear();
CurSlots = CurBranches = 0;
} else {
LLVM_DEBUG(dbgs() << "**** Adding to dispatch group: ");
LLVM_DEBUG(DAG->dumpNode(*SU));
unsigned NSlots;
bool MustBeFirst = mustComeFirst(MCID, NSlots);
// If this instruction must come first, but does not, then it starts a
// new group.
if (MustBeFirst && CurSlots) {
CurSlots = CurBranches = 0;
CurGroup.clear();
}
CurSlots += NSlots;
CurGroup.push_back(SU);
if (MCID->isBranch())
++CurBranches;
}
}
return ScoreboardHazardRecognizer::EmitInstruction(SU);
}
void PPCDispatchGroupSBHazardRecognizer::AdvanceCycle() {
return ScoreboardHazardRecognizer::AdvanceCycle();
}
void PPCDispatchGroupSBHazardRecognizer::RecedeCycle() {
llvm_unreachable("Bottom-up scheduling not supported");
}
void PPCDispatchGroupSBHazardRecognizer::Reset() {
CurGroup.clear();
CurSlots = CurBranches = 0;
return ScoreboardHazardRecognizer::Reset();
}
void PPCDispatchGroupSBHazardRecognizer::EmitNoop() {
unsigned Directive =
DAG->MF.getSubtarget<PPCSubtarget>().getDarwinDirective();
// If the group has now filled all of its slots, or if we're using a special
// group-terminating nop, the group is complete.
// FIXME: the same for P9 as previous gen until POWER9 scheduling is ready
if (Directive == PPC::DIR_PWR6 || Directive == PPC::DIR_PWR7 ||
Directive == PPC::DIR_PWR8 || Directive == PPC::DIR_PWR9 ||
CurSlots == 6) {
CurGroup.clear();
CurSlots = CurBranches = 0;
} else {
CurGroup.push_back(nullptr);
++CurSlots;
}
}
//===----------------------------------------------------------------------===//
// PowerPC 970 Hazard Recognizer
//
// This models the dispatch group formation of the PPC970 processor. Dispatch
// groups are bundles of up to five instructions that can contain various mixes
// of instructions. The PPC970 can dispatch a peak of 4 non-branch and one
// branch instruction per-cycle.
//
// There are a number of restrictions to dispatch group formation: some
// instructions can only be issued in the first slot of a dispatch group, & some
// instructions fill an entire dispatch group. Additionally, only branches can
// issue in the 5th (last) slot.
//
// Finally, there are a number of "structural" hazards on the PPC970. These
// conditions cause large performance penalties due to misprediction, recovery,
// and replay logic that has to happen. These cases include setting a CTR and
// branching through it in the same dispatch group, and storing to an address,
// then loading from the same address within a dispatch group. To avoid these
// conditions, we insert no-op instructions when appropriate.
//
// FIXME: This is missing some significant cases:
// 1. Modeling of microcoded instructions.
// 2. Handling of serialized operations.
// 3. Handling of the esoteric cases in "Resource-based Instruction Grouping".
//
PPCHazardRecognizer970::PPCHazardRecognizer970(const ScheduleDAG &DAG)
: DAG(DAG) {
EndDispatchGroup();
}
void PPCHazardRecognizer970::EndDispatchGroup() {
LLVM_DEBUG(errs() << "=== Start of dispatch group\n");
NumIssued = 0;
// Structural hazard info.
HasCTRSet = false;
NumStores = 0;
}
PPCII::PPC970_Unit
PPCHazardRecognizer970::GetInstrType(unsigned Opcode,
bool &isFirst, bool &isSingle,
bool &isCracked,
bool &isLoad, bool &isStore) {
const MCInstrDesc &MCID = DAG.TII->get(Opcode);
isLoad = MCID.mayLoad();
isStore = MCID.mayStore();
uint64_t TSFlags = MCID.TSFlags;
isFirst = TSFlags & PPCII::PPC970_First;
isSingle = TSFlags & PPCII::PPC970_Single;
isCracked = TSFlags & PPCII::PPC970_Cracked;
return (PPCII::PPC970_Unit)(TSFlags & PPCII::PPC970_Mask);
}
/// isLoadOfStoredAddress - If we have a load from the previously stored pointer
/// as indicated by StorePtr1/StorePtr2/StoreSize, return true.
bool PPCHazardRecognizer970::
isLoadOfStoredAddress(uint64_t LoadSize, int64_t LoadOffset,
const Value *LoadValue) const {
for (unsigned i = 0, e = NumStores; i != e; ++i) {
// Handle exact and commuted addresses.
if (LoadValue == StoreValue[i] && LoadOffset == StoreOffset[i])
return true;
// Okay, we don't have an exact match, if this is an indexed offset, see if
// we have overlap (which happens during fp->int conversion for example).
if (StoreValue[i] == LoadValue) {
// Okay the base pointers match, so we have [c1+r] vs [c2+r]. Check
// to see if the load and store actually overlap.
if (StoreOffset[i] < LoadOffset) {
if (int64_t(StoreOffset[i]+StoreSize[i]) > LoadOffset) return true;
} else {
if (int64_t(LoadOffset+LoadSize) > StoreOffset[i]) return true;
}
}
}
return false;
}
/// getHazardType - We return hazard for any non-branch instruction that would
/// terminate the dispatch group. We turn NoopHazard for any
/// instructions that wouldn't terminate the dispatch group that would cause a
/// pipeline flush.
ScheduleHazardRecognizer::HazardType PPCHazardRecognizer970::
getHazardType(SUnit *SU, int Stalls) {
assert(Stalls == 0 && "PPC hazards don't support scoreboard lookahead");
MachineInstr *MI = SU->getInstr();
if (MI->isDebugInstr())
return NoHazard;
unsigned Opcode = MI->getOpcode();
bool isFirst, isSingle, isCracked, isLoad, isStore;
PPCII::PPC970_Unit InstrType =
GetInstrType(Opcode, isFirst, isSingle, isCracked,
isLoad, isStore);
if (InstrType == PPCII::PPC970_Pseudo) return NoHazard;
// We can only issue a PPC970_First/PPC970_Single instruction (such as
// crand/mtspr/etc) if this is the first cycle of the dispatch group.
if (NumIssued != 0 && (isFirst || isSingle))
return Hazard;
// If this instruction is cracked into two ops by the decoder, we know that
// it is not a branch and that it cannot issue if 3 other instructions are
// already in the dispatch group.
if (isCracked && NumIssued > 2)
return Hazard;
switch (InstrType) {
default: llvm_unreachable("Unknown instruction type!");
case PPCII::PPC970_FXU:
case PPCII::PPC970_LSU:
case PPCII::PPC970_FPU:
case PPCII::PPC970_VALU:
case PPCII::PPC970_VPERM:
// We can only issue a branch as the last instruction in a group.
if (NumIssued == 4) return Hazard;
break;
case PPCII::PPC970_CRU:
// We can only issue a CR instruction in the first two slots.
if (NumIssued >= 2) return Hazard;
break;
case PPCII::PPC970_BRU:
break;
}
// Do not allow MTCTR and BCTRL to be in the same dispatch group.
if (HasCTRSet && Opcode == PPC::BCTRL)
return NoopHazard;
// If this is a load following a store, make sure it's not to the same or
// overlapping address.
if (isLoad && NumStores && !MI->memoperands_empty()) {
MachineMemOperand *MO = *MI->memoperands_begin();
if (isLoadOfStoredAddress(MO->getSize(),
MO->getOffset(), MO->getValue()))
return NoopHazard;
}
return NoHazard;
}
void PPCHazardRecognizer970::EmitInstruction(SUnit *SU) {
MachineInstr *MI = SU->getInstr();
if (MI->isDebugInstr())
return;
unsigned Opcode = MI->getOpcode();
bool isFirst, isSingle, isCracked, isLoad, isStore;
PPCII::PPC970_Unit InstrType =
GetInstrType(Opcode, isFirst, isSingle, isCracked,
isLoad, isStore);
if (InstrType == PPCII::PPC970_Pseudo) return;
// Update structural hazard information.
if (Opcode == PPC::MTCTR || Opcode == PPC::MTCTR8) HasCTRSet = true;
// Track the address stored to.
if (isStore && NumStores < 4 && !MI->memoperands_empty()) {
MachineMemOperand *MO = *MI->memoperands_begin();
StoreSize[NumStores] = MO->getSize();
StoreOffset[NumStores] = MO->getOffset();
StoreValue[NumStores] = MO->getValue();
++NumStores;
}
if (InstrType == PPCII::PPC970_BRU || isSingle)
NumIssued = 4; // Terminate a d-group.
++NumIssued;
// If this instruction is cracked into two ops by the decoder, remember that
// we issued two pieces.
if (isCracked)
++NumIssued;
if (NumIssued == 5)
EndDispatchGroup();
}
void PPCHazardRecognizer970::AdvanceCycle() {
assert(NumIssued < 5 && "Illegal dispatch group!");
++NumIssued;
if (NumIssued == 5)
EndDispatchGroup();
}
void PPCHazardRecognizer970::Reset() {
EndDispatchGroup();
}
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