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//=-- SystemZHazardRecognizer.h - SystemZ Hazard Recognizer -----*- C++ -*-===//
//
// 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 declares a hazard recognizer for the SystemZ scheduler.
//
// This class is used by the SystemZ scheduling strategy to maintain
// the state during scheduling, and provide cost functions for
// scheduling candidates. This includes:
//
// * Decoder grouping. A decoder group can maximally hold 3 uops, and
// instructions that always begin a new group should be scheduled when
// the current decoder group is empty.
// * Processor resources usage. It is beneficial to balance the use of
// resources.
//
// A goal is to consider all instructions, also those outside of any
// scheduling region. Such instructions are "advanced" past and include
// single instructions before a scheduling region, branches etc.
//
// A block that has only one predecessor continues scheduling with the state
// of it (which may be updated by emitting branches).
//
// ===---------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZHAZARDRECOGNIZER_H
#define LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZHAZARDRECOGNIZER_H
#include "SystemZSubtarget.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Support/raw_ostream.h"
#include <string>
namespace llvm {
/// SystemZHazardRecognizer maintains the state for one MBB during scheduling.
class SystemZHazardRecognizer : public ScheduleHazardRecognizer {
const SystemZInstrInfo *TII;
const TargetSchedModel *SchedModel;
/// Keep track of the number of decoder slots used in the current
/// decoder group.
unsigned CurrGroupSize;
/// True if an instruction with four reg operands have been scheduled into
/// the current decoder group.
bool CurrGroupHas4RegOps;
/// The tracking of resources here are quite similar to the common
/// code use of a critical resource. However, z13 differs in the way
/// that it has two processor sides which may be interesting to
/// model in the future (a work in progress).
/// Counters for the number of uops scheduled per processor
/// resource.
SmallVector<int, 0> ProcResourceCounters;
/// This is the resource with the greatest queue, which the
/// scheduler tries to avoid.
unsigned CriticalResourceIdx;
/// Return the number of decoder slots MI requires.
inline unsigned getNumDecoderSlots(SUnit *SU) const;
/// Return true if MI fits into current decoder group.
bool fitsIntoCurrentGroup(SUnit *SU) const;
/// Return true if this instruction has four register operands.
bool has4RegOps(const MachineInstr *MI) const;
/// Two decoder groups per cycle are formed (for z13), meaning 2x3
/// instructions. This function returns a number between 0 and 5,
/// representing the current decoder slot of the current cycle. If an SU
/// is passed which will begin a new decoder group, the returned value is
/// the cycle index of the next group.
unsigned getCurrCycleIdx(SUnit *SU = nullptr) const;
/// LastFPdOpCycleIdx stores the numbeer returned by getCurrCycleIdx()
/// when a stalling operation is scheduled (which uses the FPd resource).
unsigned LastFPdOpCycleIdx;
/// A counter of decoder groups scheduled.
unsigned GrpCount;
unsigned getCurrGroupSize() {return CurrGroupSize;};
/// Start next decoder group.
void nextGroup();
/// Clear all counters for processor resources.
void clearProcResCounters();
/// With the goal of alternating processor sides for stalling (FPd)
/// ops, return true if it seems good to schedule an FPd op next.
bool isFPdOpPreferred_distance(SUnit *SU) const;
/// Last emitted instruction or nullptr.
MachineInstr *LastEmittedMI;
public:
SystemZHazardRecognizer(const SystemZInstrInfo *tii,
const TargetSchedModel *SM)
: TII(tii), SchedModel(SM) {
Reset();
}
HazardType getHazardType(SUnit *m, int Stalls = 0) override;
void Reset() override;
void EmitInstruction(SUnit *SU) override;
/// Resolves and cache a resolved scheduling class for an SUnit.
const MCSchedClassDesc *getSchedClass(SUnit *SU) const {
if (!SU->SchedClass && SchedModel->hasInstrSchedModel())
SU->SchedClass = SchedModel->resolveSchedClass(SU->getInstr());
return SU->SchedClass;
}
/// Wrap a non-scheduled instruction in an SU and emit it.
void emitInstruction(MachineInstr *MI, bool TakenBranch = false);
// Cost functions used by SystemZPostRASchedStrategy while
// evaluating candidates.
/// Return the cost of decoder grouping for SU. If SU must start a
/// new decoder group, this is negative if this fits the schedule or
/// positive if it would mean ending a group prematurely. For normal
/// instructions this returns 0.
int groupingCost(SUnit *SU) const;
/// Return the cost of SU in regards to processor resources usage.
/// A positive value means it would be better to wait with SU, while
/// a negative value means it would be good to schedule SU next.
int resourcesCost(SUnit *SU);
#ifndef NDEBUG
// Debug dumping.
std::string CurGroupDbg; // current group as text
void dumpSU(SUnit *SU, raw_ostream &OS) const;
void dumpCurrGroup(std::string Msg = "") const;
void dumpProcResourceCounters() const;
void dumpState() const;
#endif
MachineBasicBlock::iterator getLastEmittedMI() { return LastEmittedMI; }
/// Copy counters from end of single predecessor.
void copyState(SystemZHazardRecognizer *Incoming);
};
} // namespace llvm
#endif /* LLVM_LIB_TARGET_SYSTEMZ_SYSTEMZHAZARDRECOGNIZER_H */
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