src/cpu/reg_class.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2016-2019 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Copyright (c) 2013 Advanced Micro Devices, Inc.
  * All rights reserved
  *.
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met: redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer;
  * redistributions in binary form must reproduce the above copyright
  * notice, this list of conditions and the following disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #ifndef __CPU__REG_CLASS_HH__
 #define __CPU__REG_CLASS_HH__

 #include <cassert>
 #include <cstddef>

 #include "arch/generic/types.hh"
 #include "arch/registers.hh"
 #include "config/the_isa.hh"

 /** Enumerate the classes of registers. */
 enum RegClass {
     IntRegClass,        ///< Integer register
     FloatRegClass,      ///< Floating-point register
     /** Vector Register. */
     VecRegClass,
     /** Vector Register Native Elem lane. */
     VecElemClass,
     VecPredRegClass,
     CCRegClass,         ///< Condition-code register
     MiscRegClass        ///< Control (misc) register
 };

 /** Number of register classes.
  * This value is not part of the enum, because putting it there makes the
  * compiler complain about unhandled cases in some switch statements.
  */
 const int NumRegClasses = MiscRegClass + 1;

 /** Register ID: describe an architectural register with its class and index.
  * This structure is used instead of just the register index to disambiguate
  * between different classes of registers. For example, a integer register with
  * index 3 is represented by Regid(IntRegClass, 3).
  */
 class RegId
 {
   protected:
     static const char* regClassStrings[];
     RegClass regClass;
     RegIndex regIdx;
     ElemIndex elemIdx;
     static constexpr size_t Scale = TheISA::NumVecElemPerVecReg;
     int numPinnedWrites;

     friend struct std::hash<RegId>;

   public:
     RegId() : RegId(IntRegClass, 0) {}

     RegId(RegClass reg_class, RegIndex reg_idx)
         : RegId(reg_class, reg_idx, ILLEGAL_ELEM_INDEX) {}

     explicit RegId(RegClass reg_class, RegIndex reg_idx, ElemIndex elem_idx)
         : regClass(reg_class), regIdx(reg_idx), elemIdx(elem_idx),
           numPinnedWrites(0)
     {
         if (elemIdx == ILLEGAL_ELEM_INDEX) {
             panic_if(regClass == VecElemClass,
                     "Creating vector physical index w/o element index");
         } else {
             panic_if(regClass != VecElemClass,
                     "Creating non-vector physical index w/ element index");
         }
     }

     bool
     operator==(const RegId& that) const
     {
         return regClass == that.classValue() && regIdx == that.index() &&
             elemIdx == that.elemIndex();
     }

     bool operator!=(const RegId& that) const { return !(*this==that); }

     /** Order operator.
      * The order is required to implement maps with key type RegId
      */
     bool
     operator<(const RegId& that) const
     {
         return regClass < that.classValue() ||
             (regClass == that.classValue() && (
                    regIdx < that.index() ||
                    (regIdx == that.index() && elemIdx < that.elemIndex())));
     }

     /**
      * Return true if this register can be renamed
      */
     bool
     isRenameable() const
     {
         return regClass != MiscRegClass;
     }

     /**
      * Check if this is the zero register.
      * Returns true if this register is a zero register (needs to have a
      * constant zero value throughout the execution).
      */

     inline bool
     isZeroReg() const
     {
         return regClass == IntRegClass && regIdx == TheISA::ZeroReg;
     }

     /** @return true if it is an integer physical register. */
     bool isIntReg() const { return regClass == IntRegClass; }

     /** @return true if it is a floating-point physical register. */
     bool isFloatReg() const { return regClass == FloatRegClass; }

     /** @Return true if it is a  condition-code physical register. */
     bool isVecReg() const { return regClass == VecRegClass; }

     /** @Return true if it is a  condition-code physical register. */
     bool isVecElem() const { return regClass == VecElemClass; }

     /** @Return true if it is a predicate physical register. */
     bool isVecPredReg() const { return regClass == VecPredRegClass; }

     /** @Return true if it is a  condition-code physical register. */
     bool isCCReg() const { return regClass == CCRegClass; }

     /** @Return true if it is a  condition-code physical register. */
     bool isMiscReg() const { return regClass == MiscRegClass; }

     /** Index accessors */
     /** @{ */
     const RegIndex& index() const { return regIdx; }
     RegIndex& index() { return regIdx; }

     /** Index flattening.
      * Required to be able to use a vector for the register mapping.
      */
     inline RegIndex
     flatIndex() const
     {
         switch (regClass) {
           case IntRegClass:
           case FloatRegClass:
           case VecRegClass:
           case VecPredRegClass:
           case CCRegClass:
           case MiscRegClass:
             return regIdx;
           case VecElemClass:
             return Scale * regIdx + elemIdx;
         }
         panic("Trying to flatten a register without class!");
         return -1;
     }
     /** @} */

     /** Elem accessor */
     const RegIndex& elemIndex() const { return elemIdx; }
     /** Class accessor */
     const RegClass& classValue() const { return regClass; }
     /** Return a const char* with the register class name. */
     const char* className() const { return regClassStrings[regClass]; }

     int getNumPinnedWrites() const { return numPinnedWrites; }
     void setNumPinnedWrites(int num_writes) { numPinnedWrites = num_writes; }

     friend std::ostream&
     operator<<(std::ostream& os, const RegId& rid)
     {
         return os << rid.className() << "{" << rid.index() << "}";
     }
 };

 /** Physical register index type.
  * Although the Impl might be a better for this, but there are a few classes
  * that need this typedef yet are not templated on the Impl.
  */
 using PhysRegIndex = short int;

 /** Physical register ID.
  * Like a register ID but physical. The inheritance is private because the
  * only relationship between this types is functional, and it is done to
  * prevent code replication. */
 class PhysRegId : private RegId
 {
   private:
     PhysRegIndex flatIdx;
     int numPinnedWritesToComplete;
     bool pinned;

   public:
     explicit PhysRegId() : RegId(IntRegClass, -1), flatIdx(-1),
                            numPinnedWritesToComplete(0)
     {}

     /** Scalar PhysRegId constructor. */
     explicit PhysRegId(RegClass _regClass, PhysRegIndex _regIdx,
               PhysRegIndex _flatIdx)
         : RegId(_regClass, _regIdx), flatIdx(_flatIdx),
           numPinnedWritesToComplete(0), pinned(false)
     {}

     /** Vector PhysRegId constructor (w/ elemIndex). */
     explicit PhysRegId(RegClass _regClass, PhysRegIndex _regIdx,
               ElemIndex elem_idx, PhysRegIndex flat_idx)
         : RegId(_regClass, _regIdx, elem_idx), flatIdx(flat_idx),
           numPinnedWritesToComplete(0), pinned(false)
     {}

     /** Visible RegId methods */
     /** @{ */
     using RegId::index;
     using RegId::classValue;
     using RegId::isZeroReg;
     using RegId::className;
     using RegId::elemIndex;
      /** @} */
     /**
      * Explicit forward methods, to prevent comparisons of PhysRegId with
      * RegIds.
      */
     /** @{ */
     bool
     operator<(const PhysRegId& that) const
     {
         return RegId::operator<(that);
     }

     bool
     operator==(const PhysRegId& that) const
     {
         return RegId::operator==(that);
     }

     bool
     operator!=(const PhysRegId& that) const
     {
         return RegId::operator!=(that);
     }
     /** @} */

     /** @return true if it is an integer physical register. */
     bool isIntPhysReg() const { return isIntReg(); }

     /** @return true if it is a floating-point physical register. */
     bool isFloatPhysReg() const { return isFloatReg(); }

     /** @Return true if it is a  condition-code physical register. */
     bool isCCPhysReg() const { return isCCReg(); }

     /** @Return true if it is a vector physical register. */
     bool isVectorPhysReg() const { return isVecReg(); }

     /** @Return true if it is a vector element physical register. */
     bool isVectorPhysElem() const { return isVecElem(); }

     /** @return true if it is a vector predicate physical register. */
     bool isVecPredPhysReg() const { return isVecPredReg(); }

     /** @Return true if it is a  condition-code physical register. */
     bool isMiscPhysReg() const { return isMiscReg(); }

     /**
      * Returns true if this register is always associated to the same
      * architectural register.
      */
     bool isFixedMapping() const { return !isRenameable(); }

     /** Flat index accessor */
     const PhysRegIndex& flatIndex() const { return flatIdx; }

     static PhysRegId
     elemId(PhysRegId* vid, ElemIndex elem)
     {
         assert(vid->isVectorPhysReg());
         return PhysRegId(VecElemClass, vid->index(), elem);
     }

     int getNumPinnedWrites() const { return numPinnedWrites; }

     void
     setNumPinnedWrites(int numWrites)
     {
         // An instruction with a pinned destination reg can get
         // squashed. The numPinnedWrites counter may be zero when
         // the squash happens but we need to know if the dest reg
         // was pinned originally in order to reset counters properly
         // for a possible re-rename using the same physical reg (which
         // may be required in case of a mem access order violation).
         pinned = (numWrites != 0);
         numPinnedWrites = numWrites;
     }

     void decrNumPinnedWrites() { --numPinnedWrites; }
     void incrNumPinnedWrites() { ++numPinnedWrites; }

     bool isPinned() const { return pinned; }

     int
     getNumPinnedWritesToComplete() const
     {
         return numPinnedWritesToComplete;
     }

     void
     setNumPinnedWritesToComplete(int numWrites)
     {
         numPinnedWritesToComplete = numWrites;
     }

     void decrNumPinnedWritesToComplete() { --numPinnedWritesToComplete; }
     void incrNumPinnedWritesToComplete() { ++numPinnedWritesToComplete; }
 };

 using PhysRegIdPtr = PhysRegId*;

 namespace std
 {
 template<>
 struct hash<RegId>
 {
     size_t
     operator()(const RegId& reg_id) const
     {
         // Extract unique integral values for the effective fields of a RegId.
         const size_t flat_index = static_cast<size_t>(reg_id.flatIndex());
         const size_t class_num = static_cast<size_t>(reg_id.regClass);

         const size_t shifted_class_num = class_num << (sizeof(RegIndex) << 3);

         // Concatenate the class_num to the end of the flat_index, in order to
         // maximize information retained.
         const size_t concatenated_hash = flat_index | shifted_class_num;

         // If RegIndex is larger than size_t, then class_num will not be
         // considered by this hash function, so we may wish to perform a
         // different operation to include that information in the hash.
         static_assert(sizeof(RegIndex) < sizeof(size_t),
             "sizeof(RegIndex) should be less than sizeof(size_t)");

         return concatenated_hash;
     }
 };
 }

 #endif // __CPU__REG_CLASS_HH__
	/*
	* Copyright (c) 2016-2019 ARM Limited
	* All rights reserved
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Copyright (c) 2013 Advanced Micro Devices, Inc.
	* All rights reserved
	*.
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are
	* met: redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer;
	* redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#ifndef __CPU__REG_CLASS_HH__
	#define __CPU__REG_CLASS_HH__

	#include <cassert>
	#include <cstddef>

	#include "arch/generic/types.hh"
	#include "arch/registers.hh"
	#include "config/the_isa.hh"

	/** Enumerate the classes of registers. */
	enum RegClass {
	IntRegClass, ///< Integer register
	FloatRegClass, ///< Floating-point register
	/** Vector Register. */
	VecRegClass,
	/** Vector Register Native Elem lane. */
	VecElemClass,
	VecPredRegClass,
	CCRegClass, ///< Condition-code register
	MiscRegClass ///< Control (misc) register
	};

	/** Number of register classes.
	* This value is not part of the enum, because putting it there makes the
	* compiler complain about unhandled cases in some switch statements.
	*/
	const int NumRegClasses = MiscRegClass + 1;

	/** Register ID: describe an architectural register with its class and index.
	* This structure is used instead of just the register index to disambiguate
	* between different classes of registers. For example, a integer register with
	* index 3 is represented by Regid(IntRegClass, 3).
	*/
	class RegId
	{
	protected:
	static const char* regClassStrings[];
	RegClass regClass;
	RegIndex regIdx;
	ElemIndex elemIdx;
	static constexpr size_t Scale = TheISA::NumVecElemPerVecReg;
	int numPinnedWrites;

	friend struct std::hash<RegId>;

	public:
	RegId() : RegId(IntRegClass, 0) {}

	RegId(RegClass reg_class, RegIndex reg_idx)
	: RegId(reg_class, reg_idx, ILLEGAL_ELEM_INDEX) {}

	explicit RegId(RegClass reg_class, RegIndex reg_idx, ElemIndex elem_idx)
	: regClass(reg_class), regIdx(reg_idx), elemIdx(elem_idx),
	numPinnedWrites(0)
	{
	if (elemIdx == ILLEGAL_ELEM_INDEX) {
	panic_if(regClass == VecElemClass,
	"Creating vector physical index w/o element index");
	} else {
	panic_if(regClass != VecElemClass,
	"Creating non-vector physical index w/ element index");
	}
	}

	bool
	operator==(const RegId& that) const
	{
	return regClass == that.classValue() && regIdx == that.index() &&
	elemIdx == that.elemIndex();
	}

	bool operator!=(const RegId& that) const { return !(*this==that); }

	/** Order operator.
	* The order is required to implement maps with key type RegId
	*/
	bool
	operator<(const RegId& that) const
	{
	return regClass < that.classValue() \|\|
	(regClass == that.classValue() && (
	regIdx < that.index() \|\|
	(regIdx == that.index() && elemIdx < that.elemIndex())));
	}

	/**
	* Return true if this register can be renamed
	*/
	bool
	isRenameable() const
	{
	return regClass != MiscRegClass;
	}

	/**
	* Check if this is the zero register.
	* Returns true if this register is a zero register (needs to have a
	* constant zero value throughout the execution).
	*/

	inline bool
	isZeroReg() const
	{
	return regClass == IntRegClass && regIdx == TheISA::ZeroReg;
	}

	/** @return true if it is an integer physical register. */
	bool isIntReg() const { return regClass == IntRegClass; }

	/** @return true if it is a floating-point physical register. */
	bool isFloatReg() const { return regClass == FloatRegClass; }

	/** @Return true if it is a condition-code physical register. */
	bool isVecReg() const { return regClass == VecRegClass; }

	/** @Return true if it is a condition-code physical register. */
	bool isVecElem() const { return regClass == VecElemClass; }

	/** @Return true if it is a predicate physical register. */
	bool isVecPredReg() const { return regClass == VecPredRegClass; }

	/** @Return true if it is a condition-code physical register. */
	bool isCCReg() const { return regClass == CCRegClass; }

	/** @Return true if it is a condition-code physical register. */
	bool isMiscReg() const { return regClass == MiscRegClass; }

	/** Index accessors */
	/** @{ */
	const RegIndex& index() const { return regIdx; }
	RegIndex& index() { return regIdx; }

	/** Index flattening.
	* Required to be able to use a vector for the register mapping.
	*/
	inline RegIndex
	flatIndex() const
	{
	switch (regClass) {
	case IntRegClass:
	case FloatRegClass:
	case VecRegClass:
	case VecPredRegClass:
	case CCRegClass:
	case MiscRegClass:
	return regIdx;
	case VecElemClass:
	return Scale * regIdx + elemIdx;
	}
	panic("Trying to flatten a register without class!");
	return -1;
	}
	/** @} */

	/** Elem accessor */
	const RegIndex& elemIndex() const { return elemIdx; }
	/** Class accessor */
	const RegClass& classValue() const { return regClass; }
	/** Return a const char* with the register class name. */
	const char* className() const { return regClassStrings[regClass]; }

	int getNumPinnedWrites() const { return numPinnedWrites; }
	void setNumPinnedWrites(int num_writes) { numPinnedWrites = num_writes; }

	friend std::ostream&
	operator<<(std::ostream& os, const RegId& rid)
	{
	return os << rid.className() << "{" << rid.index() << "}";
	}
	};

	/** Physical register index type.
	* Although the Impl might be a better for this, but there are a few classes
	* that need this typedef yet are not templated on the Impl.
	*/
	using PhysRegIndex = short int;

	/** Physical register ID.
	* Like a register ID but physical. The inheritance is private because the
	* only relationship between this types is functional, and it is done to
	* prevent code replication. */
	class PhysRegId : private RegId
	{
	private:
	PhysRegIndex flatIdx;
	int numPinnedWritesToComplete;
	bool pinned;

	public:
	explicit PhysRegId() : RegId(IntRegClass, -1), flatIdx(-1),
	numPinnedWritesToComplete(0)
	{}

	/** Scalar PhysRegId constructor. */
	explicit PhysRegId(RegClass _regClass, PhysRegIndex _regIdx,
	PhysRegIndex _flatIdx)
	: RegId(_regClass, _regIdx), flatIdx(_flatIdx),
	numPinnedWritesToComplete(0), pinned(false)
	{}

	/** Vector PhysRegId constructor (w/ elemIndex). */
	explicit PhysRegId(RegClass _regClass, PhysRegIndex _regIdx,
	ElemIndex elem_idx, PhysRegIndex flat_idx)
	: RegId(_regClass, _regIdx, elem_idx), flatIdx(flat_idx),
	numPinnedWritesToComplete(0), pinned(false)
	{}

	/** Visible RegId methods */
	/** @{ */
	using RegId::index;
	using RegId::classValue;
	using RegId::isZeroReg;
	using RegId::className;
	using RegId::elemIndex;
	/** @} */
	/**
	* Explicit forward methods, to prevent comparisons of PhysRegId with
	* RegIds.
	*/
	/** @{ */
	bool
	operator<(const PhysRegId& that) const
	{
	return RegId::operator<(that);
	}

	bool
	operator==(const PhysRegId& that) const
	{
	return RegId::operator==(that);
	}

	bool
	operator!=(const PhysRegId& that) const
	{
	return RegId::operator!=(that);
	}
	/** @} */

	/** @return true if it is an integer physical register. */
	bool isIntPhysReg() const { return isIntReg(); }

	/** @return true if it is a floating-point physical register. */
	bool isFloatPhysReg() const { return isFloatReg(); }

	/** @Return true if it is a condition-code physical register. */
	bool isCCPhysReg() const { return isCCReg(); }

	/** @Return true if it is a vector physical register. */
	bool isVectorPhysReg() const { return isVecReg(); }

	/** @Return true if it is a vector element physical register. */
	bool isVectorPhysElem() const { return isVecElem(); }

	/** @return true if it is a vector predicate physical register. */
	bool isVecPredPhysReg() const { return isVecPredReg(); }

	/** @Return true if it is a condition-code physical register. */
	bool isMiscPhysReg() const { return isMiscReg(); }

	/**
	* Returns true if this register is always associated to the same
	* architectural register.
	*/
	bool isFixedMapping() const { return !isRenameable(); }

	/** Flat index accessor */
	const PhysRegIndex& flatIndex() const { return flatIdx; }

	static PhysRegId
	elemId(PhysRegId* vid, ElemIndex elem)
	{
	assert(vid->isVectorPhysReg());
	return PhysRegId(VecElemClass, vid->index(), elem);
	}

	int getNumPinnedWrites() const { return numPinnedWrites; }

	void
	setNumPinnedWrites(int numWrites)
	{
	// An instruction with a pinned destination reg can get
	// squashed. The numPinnedWrites counter may be zero when
	// the squash happens but we need to know if the dest reg
	// was pinned originally in order to reset counters properly
	// for a possible re-rename using the same physical reg (which
	// may be required in case of a mem access order violation).
	pinned = (numWrites != 0);
	numPinnedWrites = numWrites;
	}

	void decrNumPinnedWrites() { --numPinnedWrites; }
	void incrNumPinnedWrites() { ++numPinnedWrites; }

	bool isPinned() const { return pinned; }

	int
	getNumPinnedWritesToComplete() const
	{
	return numPinnedWritesToComplete;
	}

	void
	setNumPinnedWritesToComplete(int numWrites)
	{
	numPinnedWritesToComplete = numWrites;
	}

	void decrNumPinnedWritesToComplete() { --numPinnedWritesToComplete; }
	void incrNumPinnedWritesToComplete() { ++numPinnedWritesToComplete; }
	};

	using PhysRegIdPtr = PhysRegId*;

	namespace std
	{
	template<>
	struct hash<RegId>
	{
	size_t
	operator()(const RegId& reg_id) const
	{
	// Extract unique integral values for the effective fields of a RegId.
	const size_t flat_index = static_cast<size_t>(reg_id.flatIndex());
	const size_t class_num = static_cast<size_t>(reg_id.regClass);

	const size_t shifted_class_num = class_num << (sizeof(RegIndex) << 3);

	// Concatenate the class_num to the end of the flat_index, in order to
	// maximize information retained.
	const size_t concatenated_hash = flat_index \| shifted_class_num;

	// If RegIndex is larger than size_t, then class_num will not be
	// considered by this hash function, so we may wish to perform a
	// different operation to include that information in the hash.
	static_assert(sizeof(RegIndex) < sizeof(size_t),
	"sizeof(RegIndex) should be less than sizeof(size_t)");

	return concatenated_hash;
	}
	};
	}

	#endif // __CPU__REG_CLASS_HH__