| /* |
| * Copyright (c) 2003-2005 The Regents of The University of Michigan |
| * 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. |
| * |
| * Authors: Steve Reinhardt |
| * Nathan Binkert |
| */ |
| |
| #ifndef __BASE_BITFIELD_HH__ |
| #define __BASE_BITFIELD_HH__ |
| |
| #include <inttypes.h> |
| |
| /** |
| * Generate a 64-bit mask of 'nbits' 1s, right justified. |
| */ |
| inline uint64_t |
| mask(int nbits) |
| { |
| return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1; |
| } |
| |
| |
| |
| /** |
| * Extract the bitfield from position 'first' to 'last' (inclusive) |
| * from 'val' and right justify it. MSB is numbered 63, LSB is 0. |
| */ |
| template <class T> |
| inline |
| T |
| bits(T val, int first, int last) |
| { |
| int nbits = first - last + 1; |
| return (val >> last) & mask(nbits); |
| } |
| |
| /** |
| * Mask off the given bits in place like bits() but without shifting. |
| * msb = 63, lsb = 0 |
| */ |
| template <class T> |
| inline |
| T |
| mbits(T val, int first, int last) |
| { |
| return val & (mask(first+1) & ~mask(last)); |
| } |
| |
| inline uint64_t |
| mask(int first, int last) |
| { |
| return mbits((uint64_t)-1LL, first, last); |
| } |
| |
| /** |
| * Sign-extend an N-bit value to 64 bits. |
| */ |
| template <int N> |
| inline |
| int64_t |
| sext(uint64_t val) |
| { |
| int sign_bit = bits(val, N-1, N-1); |
| return sign_bit ? (val | ~mask(N)) : val; |
| } |
| |
| /** |
| * Return val with bits first to last set to bit_val |
| */ |
| template <class T, class B> |
| inline |
| T |
| insertBits(T val, int first, int last, B bit_val) |
| { |
| T t_bit_val = bit_val; |
| T bmask = mask(first - last + 1) << last; |
| return ((t_bit_val << last) & bmask) | (val & ~bmask); |
| } |
| |
| /** |
| * A convenience function to replace bits first to last of val with bit_val |
| * in place. |
| */ |
| template <class T, class B> |
| inline |
| void |
| replaceBits(T& val, int first, int last, B bit_val) |
| { |
| val = insertBits(val, first, last, bit_val); |
| } |
| |
| /** |
| * Returns the bit position of the MSB that is set in the input |
| */ |
| inline |
| int |
| findMsbSet(uint64_t val) { |
| int msb = 0; |
| if (!val) |
| return 0; |
| if (bits(val, 63,32)) { msb += 32; val >>= 32; } |
| if (bits(val, 31,16)) { msb += 16; val >>= 16; } |
| if (bits(val, 15,8)) { msb += 8; val >>= 8; } |
| if (bits(val, 7,4)) { msb += 4; val >>= 4; } |
| if (bits(val, 3,2)) { msb += 2; val >>= 2; } |
| if (bits(val, 1,1)) { msb += 1; } |
| return msb; |
| } |
| |
| // The following implements the BitUnion system of defining bitfields |
| //on top of an underlying class. This is done through the pervasive use of |
| //both named and unnamed unions which all contain the same actual storage. |
| //Since they're unioned with each other, all of these storage locations |
| //overlap. This allows all of the bitfields to manipulate the same data |
| //without having to have access to each other. More details are provided with the |
| //individual components. |
| |
| //This namespace is for classes which implement the backend of the BitUnion |
| //stuff. Don't use any of these directly, except for the Bitfield classes in |
| //the *BitfieldTypes class(es). |
| namespace BitfieldBackend |
| { |
| //A base class for all bitfields. It instantiates the actual storage, |
| //and provides getBits and setBits functions for manipulating it. The |
| //Data template parameter is type of the underlying storage. |
| template<class Data> |
| class BitfieldBase |
| { |
| protected: |
| Data __data; |
| |
| //This function returns a range of bits from the underlying storage. |
| //It relies on the "bits" function above. It's the user's |
| //responsibility to make sure that there is a properly overloaded |
| //version of this function for whatever type they want to overlay. |
| inline uint64_t |
| getBits(int first, int last) const |
| { |
| return bits(__data, first, last); |
| } |
| |
| //Similar to the above, but for settings bits with replaceBits. |
| inline void |
| setBits(int first, int last, uint64_t val) |
| { |
| replaceBits(__data, first, last, val); |
| } |
| }; |
| |
| //This class contains all the "regular" bitfield classes. It is inherited |
| //by all BitUnions which give them access to those types. |
| template<class Type> |
| class RegularBitfieldTypes |
| { |
| protected: |
| //This class implements ordinary bitfields, that is a span of bits |
| //who's msb is "first", and who's lsb is "last". |
| template<int first, int last=first> |
| class Bitfield : public BitfieldBase<Type> |
| { |
| public: |
| operator uint64_t () const |
| { |
| return this->getBits(first, last); |
| } |
| |
| uint64_t |
| operator=(const uint64_t _data) |
| { |
| this->setBits(first, last, _data); |
| return _data; |
| } |
| }; |
| |
| //A class which specializes the above so that it can only be read |
| //from. This is accomplished explicitly making sure the assignment |
| //operator is blocked. The conversion operator is carried through |
| //inheritance. This will unfortunately need to be copied into each |
| //bitfield type due to limitations with how templates work |
| template<int first, int last=first> |
| class BitfieldRO : public Bitfield<first, last> |
| { |
| private: |
| uint64_t |
| operator=(const uint64_t _data); |
| }; |
| |
| //Similar to the above, but only allows writing. |
| template<int first, int last=first> |
| class BitfieldWO : public Bitfield<first, last> |
| { |
| private: |
| operator uint64_t () const; |
| |
| public: |
| using Bitfield<first, last>::operator=; |
| }; |
| }; |
| |
| //This class contains all the "regular" bitfield classes. It is inherited |
| //by all BitUnions which give them access to those types. |
| template<class Type> |
| class SignedBitfieldTypes |
| { |
| protected: |
| //This class implements ordinary bitfields, that is a span of bits |
| //who's msb is "first", and who's lsb is "last". |
| template<int first, int last=first> |
| class SignedBitfield : public BitfieldBase<Type> |
| { |
| public: |
| operator int64_t () const |
| { |
| return sext<first - last + 1>(this->getBits(first, last)); |
| } |
| |
| int64_t |
| operator=(const int64_t _data) |
| { |
| this->setBits(first, last, _data); |
| return _data; |
| } |
| }; |
| |
| //A class which specializes the above so that it can only be read |
| //from. This is accomplished explicitly making sure the assignment |
| //operator is blocked. The conversion operator is carried through |
| //inheritance. This will unfortunately need to be copied into each |
| //bitfield type due to limitations with how templates work |
| template<int first, int last=first> |
| class SignedBitfieldRO : public SignedBitfield<first, last> |
| { |
| private: |
| int64_t |
| operator=(const int64_t _data); |
| }; |
| |
| //Similar to the above, but only allows writing. |
| template<int first, int last=first> |
| class SignedBitfieldWO : public SignedBitfield<first, last> |
| { |
| private: |
| operator int64_t () const; |
| |
| public: |
| int64_t operator=(const int64_t _data) |
| { |
| *((SignedBitfield<first, last> *)this) = _data; |
| return _data; |
| } |
| }; |
| }; |
| |
| template<class Type> |
| class BitfieldTypes : public RegularBitfieldTypes<Type>, |
| public SignedBitfieldTypes<Type> |
| {}; |
| |
| //When a BitUnion is set up, an underlying class is created which holds |
| //the actual union. This class then inherits from it, and provids the |
| //implementations for various operators. Setting things up this way |
| //prevents having to redefine these functions in every different BitUnion |
| //type. More operators could be implemented in the future, as the need |
| //arises. |
| template <class Type, class Base> |
| class BitUnionOperators : public Base |
| { |
| public: |
| operator Type () const |
| { |
| return Base::__data; |
| } |
| |
| Type |
| operator=(const Type & _data) |
| { |
| Base::__data = _data; |
| return _data; |
| } |
| |
| bool |
| operator<(const Base & base) const |
| { |
| return Base::__data < base.__data; |
| } |
| |
| bool |
| operator==(const Base & base) const |
| { |
| return Base::__data == base.__data; |
| } |
| }; |
| } |
| |
| //This macro is a backend for other macros that specialize it slightly. |
| //First, it creates/extends a namespace "BitfieldUnderlyingClasses" and |
| //sticks the class which has the actual union in it, which |
| //BitfieldOperators above inherits from. Putting these classes in a special |
| //namespace ensures that there will be no collisions with other names as long |
| //as the BitUnion names themselves are all distinct and nothing else uses |
| //the BitfieldUnderlyingClasses namespace, which is unlikely. The class itself |
| //creates a typedef of the "type" parameter called __DataType. This allows |
| //the type to propagate outside of the macro itself in a controlled way. |
| //Finally, the base storage is defined which BitfieldOperators will refer to |
| //in the operators it defines. This macro is intended to be followed by |
| //bitfield definitions which will end up inside it's union. As explained |
| //above, these is overlayed the __data member in its entirety by each of the |
| //bitfields which are defined in the union, creating shared storage with no |
| //overhead. |
| #define __BitUnion(type, name) \ |
| namespace BitfieldUnderlyingClasses \ |
| { \ |
| class name; \ |
| } \ |
| class BitfieldUnderlyingClasses::name : \ |
| public BitfieldBackend::BitfieldTypes<type> \ |
| { \ |
| public: \ |
| typedef type __DataType; \ |
| union { \ |
| type __data;\ |
| |
| //This closes off the class and union started by the above macro. It is |
| //followed by a typedef which makes "name" refer to a BitfieldOperator |
| //class inheriting from the class and union just defined, which completes |
| //building up the type for the user. |
| #define EndBitUnion(name) \ |
| }; \ |
| }; \ |
| typedef BitfieldBackend::BitUnionOperators< \ |
| BitfieldUnderlyingClasses::name::__DataType, \ |
| BitfieldUnderlyingClasses::name> name; |
| |
| //This sets up a bitfield which has other bitfields nested inside of it. The |
| //__data member functions like the "underlying storage" of the top level |
| //BitUnion. Like everything else, it overlays with the top level storage, so |
| //making it a regular bitfield type makes the entire thing function as a |
| //regular bitfield when referred to by itself. |
| #define __SubBitUnion(fieldType, first, last, name) \ |
| class : public BitfieldBackend::BitfieldTypes<__DataType> \ |
| { \ |
| public: \ |
| union { \ |
| fieldType<first, last> __data; |
| |
| //This closes off the union created above and gives it a name. Unlike the top |
| //level BitUnion, we're interested in creating an object instead of a type. |
| //The operators are defined in the macro itself instead of a class for |
| //technical reasons. If someone determines a way to move them to one, please |
| //do so. |
| #define EndSubBitUnion(name) \ |
| }; \ |
| inline operator const __DataType () \ |
| { return __data; } \ |
| \ |
| inline const __DataType operator = (const __DataType & _data) \ |
| { __data = _data; } \ |
| } name; |
| |
| //Regular bitfields |
| //These define macros for read/write regular bitfield based subbitfields. |
| #define SubBitUnion(name, first, last) \ |
| __SubBitUnion(Bitfield, first, last, name) |
| |
| //Regular bitfields |
| //These define macros for read/write regular bitfield based subbitfields. |
| #define SignedSubBitUnion(name, first, last) \ |
| __SubBitUnion(SignedBitfield, first, last, name) |
| |
| //Use this to define an arbitrary type overlayed with bitfields. |
| #define BitUnion(type, name) __BitUnion(type, name) |
| |
| //Use this to define conveniently sized values overlayed with bitfields. |
| #define BitUnion64(name) __BitUnion(uint64_t, name) |
| #define BitUnion32(name) __BitUnion(uint32_t, name) |
| #define BitUnion16(name) __BitUnion(uint16_t, name) |
| #define BitUnion8(name) __BitUnion(uint8_t, name) |
| |
| #endif // __BASE_BITFIELD_HH__ |