include/llvm/MC/MCSubtargetInfo.h - llvm-project/llvm - Git at Google

 //===- 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/MC/MCInstrItineraries.h"
 #include "llvm/MC/MCSchedule.h"
 #include "llvm/TargetParser/SubtargetFeature.h"
 #include "llvm/TargetParser/Triple.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;
   }

   /// Return processor descriptions.
   ArrayRef<SubtargetSubTypeKV> getAllProcessorDescriptions() const {
     return ProcDesc;
   }

   /// Return processor features.
   ArrayRef<SubtargetFeatureKV> getAllProcessorFeatures() const {
     return ProcFeatures;
   }

   /// HwMode IDs are stored and accessed in a bit set format, enabling
   /// users to efficiently retrieve specific IDs, such as the RegInfo
   /// HwMode ID, from the set as required. Using this approach, various
   /// types of HwMode IDs can be added to a subtarget to manage different
   /// attributes within that subtarget, significantly enhancing the
   /// scalability and usability of HwMode. Moreover, to ensure compatibility,
   /// this method also supports controlling multiple attributes with a single
   /// HwMode ID, just as was done previously.
   enum HwModeType {
     HwMode_Default,   // Return the smallest HwMode ID of current subtarget.
     HwMode_ValueType, // Return the HwMode ID that controls the ValueType.
     HwMode_RegInfo,   // Return the HwMode ID that controls the RegSizeInfo and
                       // SubRegRange.
     HwMode_EncodingInfo // Return the HwMode ID that controls the EncodingInfo.
   };

   /// Return a bit set containing all HwMode IDs of the current subtarget.
   virtual unsigned getHwModeSet() const { return 0; }

   /// HwMode ID corresponding to the 'type' parameter is retrieved from the
   /// HwMode bit set of the current subtarget. It’s important to note that if
   /// the current subtarget possesses two HwMode IDs and both control a single
   /// attribute (such as RegInfo), this interface will result in an error.
   virtual unsigned getHwMode(enum HwModeType type = HwMode_Default) 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
	//===- 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/MC/MCInstrItineraries.h"
	#include "llvm/MC/MCSchedule.h"
	#include "llvm/TargetParser/SubtargetFeature.h"
	#include "llvm/TargetParser/Triple.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;
	}

	/// Return processor descriptions.
	ArrayRef<SubtargetSubTypeKV> getAllProcessorDescriptions() const {
	return ProcDesc;
	}

	/// Return processor features.
	ArrayRef<SubtargetFeatureKV> getAllProcessorFeatures() const {
	return ProcFeatures;
	}

	/// HwMode IDs are stored and accessed in a bit set format, enabling
	/// users to efficiently retrieve specific IDs, such as the RegInfo
	/// HwMode ID, from the set as required. Using this approach, various
	/// types of HwMode IDs can be added to a subtarget to manage different
	/// attributes within that subtarget, significantly enhancing the
	/// scalability and usability of HwMode. Moreover, to ensure compatibility,
	/// this method also supports controlling multiple attributes with a single
	/// HwMode ID, just as was done previously.
	enum HwModeType {
	HwMode_Default, // Return the smallest HwMode ID of current subtarget.
	HwMode_ValueType, // Return the HwMode ID that controls the ValueType.
	HwMode_RegInfo, // Return the HwMode ID that controls the RegSizeInfo and
	// SubRegRange.
	HwMode_EncodingInfo // Return the HwMode ID that controls the EncodingInfo.
	};

	/// Return a bit set containing all HwMode IDs of the current subtarget.
	virtual unsigned getHwModeSet() const { return 0; }

	/// HwMode ID corresponding to the 'type' parameter is retrieved from the
	/// HwMode bit set of the current subtarget. It’s important to note that if
	/// the current subtarget possesses two HwMode IDs and both control a single
	/// attribute (such as RegInfo), this interface will result in an error.
	virtual unsigned getHwMode(enum HwModeType type = HwMode_Default) 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