//===- llvm/MC/MCSubtargetInfo.h - Subtarget Information --------*- 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 describes the subtarget options of a Target machine.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCSUBTARGETINFO_H
#define LLVM_MC_MCSUBTARGETINFO_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/MC/MCInstrItineraries.h"
#include "llvm/MC/MCSchedule.h"
#include "llvm/MC/SubtargetFeature.h"
#include <cassert>
#include <cstdint>
#include <optional>
#include <string>
namespace llvm {
class MCInst;
//===----------------------------------------------------------------------===//
/// Used to provide key value pairs for feature and CPU bit flags.
struct SubtargetFeatureKV {
const char *Key; ///< K-V key string
const char *Desc; ///< Help descriptor
unsigned Value; ///< K-V integer value
FeatureBitArray Implies; ///< K-V bit mask
/// Compare routine for std::lower_bound
bool operator<(StringRef S) const {
return StringRef(Key) < S;
}
/// Compare routine for std::is_sorted.
bool operator<(const SubtargetFeatureKV &Other) const {
return StringRef(Key) < StringRef(Other.Key);
}
};
//===----------------------------------------------------------------------===//
/// Used to provide key value pairs for feature and CPU bit flags.
struct SubtargetSubTypeKV {
const char *Key; ///< K-V key string
FeatureBitArray Implies; ///< K-V bit mask
FeatureBitArray TuneImplies; ///< K-V bit mask
const MCSchedModel *SchedModel;
/// Compare routine for std::lower_bound
bool operator<(StringRef S) const {
return StringRef(Key) < S;
}
/// Compare routine for std::is_sorted.
bool operator<(const SubtargetSubTypeKV &Other) const {
return StringRef(Key) < StringRef(Other.Key);
}
};
//===----------------------------------------------------------------------===//
///
/// Generic base class for all target subtargets.
///
class MCSubtargetInfo {
Triple TargetTriple;
std::string CPU; // CPU being targeted.
std::string TuneCPU; // CPU being tuned for.
ArrayRef<SubtargetFeatureKV> ProcFeatures; // Processor feature list
ArrayRef<SubtargetSubTypeKV> ProcDesc; // Processor descriptions
// Scheduler machine model
const MCWriteProcResEntry *WriteProcResTable;
const MCWriteLatencyEntry *WriteLatencyTable;
const MCReadAdvanceEntry *ReadAdvanceTable;
const MCSchedModel *CPUSchedModel;
const InstrStage *Stages; // Instruction itinerary stages
const unsigned *OperandCycles; // Itinerary operand cycles
const unsigned *ForwardingPaths;
FeatureBitset FeatureBits; // Feature bits for current CPU + FS
std::string FeatureString; // Feature string
public:
MCSubtargetInfo(const MCSubtargetInfo &) = default;
MCSubtargetInfo(const Triple &TT, StringRef CPU, StringRef TuneCPU,
StringRef FS, ArrayRef<SubtargetFeatureKV> PF,
ArrayRef<SubtargetSubTypeKV> PD,
const MCWriteProcResEntry *WPR, const MCWriteLatencyEntry *WL,
const MCReadAdvanceEntry *RA, const InstrStage *IS,
const unsigned *OC, const unsigned *FP);
MCSubtargetInfo() = delete;
MCSubtargetInfo &operator=(const MCSubtargetInfo &) = delete;
MCSubtargetInfo &operator=(MCSubtargetInfo &&) = delete;
virtual ~MCSubtargetInfo() = default;
const Triple &getTargetTriple() const { return TargetTriple; }
StringRef getCPU() const { return CPU; }
StringRef getTuneCPU() const { return TuneCPU; }
const FeatureBitset& getFeatureBits() const { return FeatureBits; }
void setFeatureBits(const FeatureBitset &FeatureBits_) {
FeatureBits = FeatureBits_;
}
StringRef getFeatureString() const { return FeatureString; }
bool hasFeature(unsigned Feature) const {
return FeatureBits[Feature];
}
protected:
/// Initialize the scheduling model and feature bits.
///
/// FIXME: Find a way to stick this in the constructor, since it should only
/// be called during initialization.
void InitMCProcessorInfo(StringRef CPU, StringRef TuneCPU, StringRef FS);
public:
/// Set the features to the default for the given CPU and TuneCPU, with ano
/// appended feature string.
void setDefaultFeatures(StringRef CPU, StringRef TuneCPU, StringRef FS);
/// Toggle a feature and return the re-computed feature bits.
/// This version does not change the implied bits.
FeatureBitset ToggleFeature(uint64_t FB);
/// Toggle a feature and return the re-computed feature bits.
/// This version does not change the implied bits.
FeatureBitset ToggleFeature(const FeatureBitset& FB);
/// Toggle a set of features and return the re-computed feature bits.
/// This version will also change all implied bits.
FeatureBitset ToggleFeature(StringRef FS);
/// Apply a feature flag and return the re-computed feature bits, including
/// all feature bits implied by the flag.
FeatureBitset ApplyFeatureFlag(StringRef FS);
/// Set/clear additional feature bits, including all other bits they imply.
FeatureBitset SetFeatureBitsTransitively(const FeatureBitset& FB);
FeatureBitset ClearFeatureBitsTransitively(const FeatureBitset &FB);
/// Check whether the subtarget features are enabled/disabled as per
/// the provided string, ignoring all other features.
bool checkFeatures(StringRef FS) const;
/// Get the machine model of a CPU.
const MCSchedModel &getSchedModelForCPU(StringRef CPU) const;
/// Get the machine model for this subtarget's CPU.
const MCSchedModel &getSchedModel() const { return *CPUSchedModel; }
/// Return an iterator at the first process resource consumed by the given
/// scheduling class.
const MCWriteProcResEntry *getWriteProcResBegin(
const MCSchedClassDesc *SC) const {
return &WriteProcResTable[SC->WriteProcResIdx];
}
const MCWriteProcResEntry *getWriteProcResEnd(
const MCSchedClassDesc *SC) const {
return getWriteProcResBegin(SC) + SC->NumWriteProcResEntries;
}
const MCWriteLatencyEntry *getWriteLatencyEntry(const MCSchedClassDesc *SC,
unsigned DefIdx) const {
assert(DefIdx < SC->NumWriteLatencyEntries &&
"MachineModel does not specify a WriteResource for DefIdx");
return &WriteLatencyTable[SC->WriteLatencyIdx + DefIdx];
}
int getReadAdvanceCycles(const MCSchedClassDesc *SC, unsigned UseIdx,
unsigned WriteResID) const {
// TODO: The number of read advance entries in a class can be significant
// (~50). Consider compressing the WriteID into a dense ID of those that are
// used by ReadAdvance and representing them as a bitset.
for (const MCReadAdvanceEntry *I = &ReadAdvanceTable[SC->ReadAdvanceIdx],
*E = I + SC->NumReadAdvanceEntries; I != E; ++I) {
if (I->UseIdx < UseIdx)
continue;
if (I->UseIdx > UseIdx)
break;
// Find the first WriteResIdx match, which has the highest cycle count.
if (!I->WriteResourceID || I->WriteResourceID == WriteResID) {
return I->Cycles;
}
}
return 0;
}
/// Return the set of ReadAdvance entries declared by the scheduling class
/// descriptor in input.
ArrayRef<MCReadAdvanceEntry>
getReadAdvanceEntries(const MCSchedClassDesc &SC) const {
if (!SC.NumReadAdvanceEntries)
return ArrayRef<MCReadAdvanceEntry>();
return ArrayRef<MCReadAdvanceEntry>(&ReadAdvanceTable[SC.ReadAdvanceIdx],
SC.NumReadAdvanceEntries);
}
/// Get scheduling itinerary of a CPU.
InstrItineraryData getInstrItineraryForCPU(StringRef CPU) const;
/// Initialize an InstrItineraryData instance.
void initInstrItins(InstrItineraryData &InstrItins) const;
/// Resolve a variant scheduling class for the given MCInst and CPU.
virtual unsigned resolveVariantSchedClass(unsigned SchedClass,
const MCInst *MI,
const MCInstrInfo *MCII,
unsigned CPUID) const {
return 0;
}
/// Check whether the CPU string is valid.
bool isCPUStringValid(StringRef CPU) const {
auto Found = llvm::lower_bound(ProcDesc, CPU);
return Found != ProcDesc.end() && StringRef(Found->Key) == CPU;
}
virtual unsigned getHwMode() const { return 0; }
/// Return the cache size in bytes for the given level of cache.
/// Level is zero-based, so a value of zero means the first level of
/// cache.
///
virtual std::optional<unsigned> getCacheSize(unsigned Level) const;
/// Return the cache associatvity for the given level of cache.
/// Level is zero-based, so a value of zero means the first level of
/// cache.
///
virtual std::optional<unsigned> getCacheAssociativity(unsigned Level) const;
/// Return the target cache line size in bytes at a given level.
///
virtual std::optional<unsigned> getCacheLineSize(unsigned Level) const;
/// Return the target cache line size in bytes. By default, return
/// the line size for the bottom-most level of cache. This provides
/// a more convenient interface for the common case where all cache
/// levels have the same line size. Return zero if there is no
/// cache model.
///
virtual unsigned getCacheLineSize() const {
std::optional<unsigned> Size = getCacheLineSize(0);
if (Size)
return *Size;
return 0;
}
/// Return the preferred prefetch distance in terms of instructions.
///
virtual unsigned getPrefetchDistance() const;
/// Return the maximum prefetch distance in terms of loop
/// iterations.
///
virtual unsigned getMaxPrefetchIterationsAhead() const;
/// \return True if prefetching should also be done for writes.
///
virtual bool enableWritePrefetching() const;
/// Return the minimum stride necessary to trigger software
/// prefetching.
///
virtual unsigned getMinPrefetchStride(unsigned NumMemAccesses,
unsigned NumStridedMemAccesses,
unsigned NumPrefetches,
bool HasCall) const;
/// \return if target want to issue a prefetch in address space \p AS.
virtual bool shouldPrefetchAddressSpace(unsigned AS) const;
};
} // end namespace llvm
#endif // LLVM_MC_MCSUBTARGETINFO_H