cosmopolitan/libc/bits/bits.h

#ifndef COSMOPOLITAN_LIBC_BITS_H_
#define COSMOPOLITAN_LIBC_BITS_H_
#if !(__ASSEMBLER__ + __LINKER__ + 0)
COSMOPOLITAN_C_START_

#define CheckUnsigned(x) ((x) / !((typeof(x))(-1) < 0))

/*───────────────────────────────────────────────────────────────────────────│─╗
│ cosmopolitan § bits                                                      ─╬─│┼
╚────────────────────────────────────────────────────────────────────────────│*/

extern const uint8_t kReverseBits[256];

uint32_t gray(uint32_t) pureconst;
uint32_t ungray(uint32_t) pureconst;

uint8_t bitreverse8(uint8_t) libcesque pureconst;
uint16_t bitreverse16(uint16_t) libcesque pureconst;
uint32_t bitreverse32(uint32_t) libcesque pureconst;
uint64_t bitreverse64(uint64_t) libcesque pureconst;

unsigned long roundup2pow(unsigned long) libcesque pureconst;
unsigned long roundup2log(unsigned long) libcesque pureconst;
unsigned long rounddown2pow(unsigned long) libcesque pureconst;

unsigned long hamming(unsigned long, unsigned long) pureconst;

/*───────────────────────────────────────────────────────────────────────────│─╗
│ cosmopolitan § bits » no assembly required                               ─╬─│┼
╚────────────────────────────────────────────────────────────────────────────│*/

#define bitreverse8(X) (kReverseBits[(uint8_t)(X)])
#define bitreverse16(X)                          \
  ((uint16_t)kReverseBits[(uint8_t)(X)] << 010 | \
   kReverseBits[((uint16_t)(X) >> 010) & 0xff])

#define READ16LE(S)                             \
  ((uint16_t)((unsigned char *)(S))[1] << 010 | \
   (uint16_t)((unsigned char *)(S))[0] << 000)
#define READ32LE(S)                             \
  ((uint32_t)((unsigned char *)(S))[3] << 030 | \
   (uint32_t)((unsigned char *)(S))[2] << 020 | \
   (uint32_t)((unsigned char *)(S))[1] << 010 | \
   (uint32_t)((unsigned char *)(S))[0] << 000)
#define READ64LE(S)                             \
  ((uint64_t)((unsigned char *)(S))[7] << 070 | \
   (uint64_t)((unsigned char *)(S))[6] << 060 | \
   (uint64_t)((unsigned char *)(S))[5] << 050 | \
   (uint64_t)((unsigned char *)(S))[4] << 040 | \
   (uint64_t)((unsigned char *)(S))[3] << 030 | \
   (uint64_t)((unsigned char *)(S))[2] << 020 | \
   (uint64_t)((unsigned char *)(S))[1] << 010 | \
   (uint64_t)((unsigned char *)(S))[0] << 000)

#define READ16BE(S)                             \
  ((uint16_t)((unsigned char *)(S))[0] << 010 | \
   (uint16_t)((unsigned char *)(S))[1] << 000)
#define READ32BE(S)                             \
  ((uint32_t)((unsigned char *)(S))[0] << 030 | \
   (uint32_t)((unsigned char *)(S))[1] << 020 | \
   (uint32_t)((unsigned char *)(S))[2] << 010 | \
   (uint32_t)((unsigned char *)(S))[3] << 000)
#define READ64BE(S)                             \
  ((uint64_t)((unsigned char *)(S))[0] << 070 | \
   (uint64_t)((unsigned char *)(S))[1] << 060 | \
   (uint64_t)((unsigned char *)(S))[2] << 050 | \
   (uint64_t)((unsigned char *)(S))[3] << 040 | \
   (uint64_t)((unsigned char *)(S))[4] << 030 | \
   (uint64_t)((unsigned char *)(S))[5] << 020 | \
   (uint64_t)((unsigned char *)(S))[6] << 010 | \
   (uint64_t)((unsigned char *)(S))[7] << 000)

#define read16le(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ16LE(Str);                             \
  })
#define read32le(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ32LE(Str);                             \
  })
#define read64le(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ64LE(Str);                             \
  })

#define read16be(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ16BE(Str);                             \
  })
#define read32be(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ32BE(Str);                             \
  })
#define read64be(S)                            \
  ({                                           \
    unsigned char *Str = (unsigned char *)(S); \
    READ64BE(Str);                             \
  })

#define WRITE16LE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint16_t Vle = (V);             \
    Ple[0] = (uint8_t)(Vle >> 000); \
    Ple[1] = (uint8_t)(Vle >> 010); \
  } while (0)
#define WRITE32LE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint32_t Vle = (V);             \
    Ple[0] = (uint8_t)(Vle >> 000); \
    Ple[1] = (uint8_t)(Vle >> 010); \
    Ple[2] = (uint8_t)(Vle >> 020); \
    Ple[3] = (uint8_t)(Vle >> 030); \
  } while (0)
#define WRITE64LE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint64_t Vle = (V);             \
    Ple[0] = (uint8_t)(Vle >> 000); \
    Ple[1] = (uint8_t)(Vle >> 010); \
    Ple[2] = (uint8_t)(Vle >> 020); \
    Ple[3] = (uint8_t)(Vle >> 030); \
    Ple[4] = (uint8_t)(Vle >> 040); \
    Ple[5] = (uint8_t)(Vle >> 050); \
    Ple[6] = (uint8_t)(Vle >> 060); \
    Ple[7] = (uint8_t)(Vle >> 070); \
  } while (0)

#define WRITE16BE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint16_t Vle = (V);             \
    Ple[1] = (uint8_t)(Vle >> 000); \
    Ple[0] = (uint8_t)(Vle >> 010); \
  } while (0)
#define WRITE32BE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint32_t Vle = (V);             \
    Ple[3] = (uint8_t)(Vle >> 000); \
    Ple[2] = (uint8_t)(Vle >> 010); \
    Ple[1] = (uint8_t)(Vle >> 020); \
    Ple[0] = (uint8_t)(Vle >> 030); \
  } while (0)
#define WRITE64BE(P, V)             \
  do {                              \
    uint8_t *Ple = (uint8_t *)(P);  \
    uint64_t Vle = (V);             \
    Ple[7] = (uint8_t)(Vle >> 000); \
    Ple[6] = (uint8_t)(Vle >> 010); \
    Ple[5] = (uint8_t)(Vle >> 020); \
    Ple[4] = (uint8_t)(Vle >> 030); \
    Ple[3] = (uint8_t)(Vle >> 040); \
    Ple[2] = (uint8_t)(Vle >> 050); \
    Ple[1] = (uint8_t)(Vle >> 060); \
    Ple[0] = (uint8_t)(Vle >> 070); \
  } while (0)

/*───────────────────────────────────────────────────────────────────────────│─╗
│ cosmopolitan § bits » some assembly required                             ─╬─│┼
╚────────────────────────────────────────────────────────────────────────────│*/

/**
 * Constraints for virtual machine flags.
 * @note we beseech clang devs for flag constraints
 */
#ifdef __GCC_ASM_FLAG_OUTPUTS__ /* GCC6+ CLANG10+ */
#define CFLAG_CONSTRAINT  "=@ccc"
#define CFLAG_ASM(OP)     OP
#define ZFLAG_CONSTRAINT  "=@ccz"
#define ZFLAG_ASM(OP)     OP
#define OFLAG_CONSTRAINT  "=@cco"
#define OFLAG_ASM(OP)     OP
#define SFLAG_CONSTRAINT  "=@ccs"
#define SFLAG_ASM(SP)     SP
#define ABOVE_CONSTRAINT  "=@cca" /* i.e. !ZF && !CF */
#define ABOVEFLAG_ASM(OP) OP
#else
#define CFLAG_CONSTRAINT  "=q"
#define CFLAG_ASM(OP)     OP "\n\tsetc\t%b0"
#define ZFLAG_CONSTRAINT  "=q"
#define ZFLAG_ASM(OP)     OP "\n\tsetz\t%b0"
#define OFLAG_CONSTRAINT  "=q"
#define OFLAG_ASM(OP)     OP "\n\tseto\t%b0"
#define SFLAG_CONSTRAINT  "=q"
#define SFLAG_ASM(SP)     OP "\n\tsets\t%b0"
#define ABOVE_CONSTRAINT  "=@cca"
#define ABOVEFLAG_ASM(OP) OP "\n\tseta\t%b0"
#endif

/**
 * Reads scalar from memory w/ one operation.
 *
 * @param MEM is alignas(𝑘) uint𝑘_t[hasatleast 1] where 𝑘 ∈ {8,16,32,64}
 * @return *(MEM)
 * @note defeats compiler load tearing optimizations
 * @note alignas(𝑘) is implied if compiler knows type
 * @note alignas(𝑘) only avoids multi-core / cross-page edge cases
 * @see Intel's Six-Thousand Page Manual V.3A §8.2.3.1
 * @see atomic_store()
 */
#define atomic_load(MEM)                       \
  ({                                           \
    autotype(MEM) Mem = (MEM);                 \
    typeof(*Mem) Reg;                          \
    asm("mov\t%1,%0" : "=r"(Reg) : "m"(*Mem)); \
    Reg;                                       \
  })

/**
 * Saves scalar to memory w/ one operation.
 *
 * This is guaranteed to happen in either one or zero operations,
 * depending on whether or not it's possible for *(MEM) to be read
 * afterwards. This macro only forbids compiler from using >1 ops.
 *
 * @param MEM is alignas(𝑘) uint𝑘_t[hasatleast 1] where 𝑘 ∈ {8,16,32,64}
 * @param VAL is uint𝑘_t w/ better encoding for immediates (constexpr)
 * @return VAL
 * @note alignas(𝑘) on nexgen32e only needed for end of page gotcha
 * @note alignas(𝑘) is implied if compiler knows type
 * @note needed to defeat store tearing optimizations
 * @see Intel Six-Thousand Page Manual Manual V.3A §8.2.3.1
 * @see atomic_load()
 */
#define atomic_store(MEM, VAL)                        \
  ({                                                  \
    autotype(VAL) Val = (VAL);                        \
    typeof(&Val) Mem = (MEM);                         \
    asm("mov%z1\t%1,%0" : "=m,m"(*Mem) : "i,r"(Val)); \
    Val;                                              \
  })

#define bts(MEM, BIT)     __BitOp("bts", BIT, MEM) /** bit test and set */
#define btr(MEM, BIT)     __BitOp("btr", BIT, MEM) /** bit test and reset */
#define btc(MEM, BIT)     __BitOp("btc", BIT, MEM) /** bit test and complement */
#define lockbts(MEM, BIT) __BitOp("lock bts", BIT, MEM)
#define lockbtr(MEM, BIT) __BitOp("lock btr", BIT, MEM)
#define lockbtc(MEM, BIT) __BitOp("lock btc", BIT, MEM)

#define lockinc(MEM) __ArithmeticOp1("lock inc", MEM)
#define lockdec(MEM) __ArithmeticOp1("lock dec", MEM)
#define locknot(MEM) __ArithmeticOp1("lock not", MEM)
#define lockneg(MEM) __ArithmeticOp1("lock neg", MEM)

#define lockaddeq(MEM, VAL) __ArithmeticOp2("lock add", VAL, MEM)
#define locksubeq(MEM, VAL) __ArithmeticOp2("lock sub", VAL, MEM)
#define lockxoreq(MEM, VAL) __ArithmeticOp2("lock xor", VAL, MEM)
#define lockandeq(MEM, VAL) __ArithmeticOp2("lock and", VAL, MEM)
#define lockoreq(MEM, VAL)  __ArithmeticOp2("lock or", VAL, MEM)

/**
 * Exchanges *MEMORY into *LOCALVAR w/ one operation.
 *
 * @param MEMORY is uint𝑘_t[hasatleast 1] where 𝑘 ∈ {8,16,32,64}
 * @param LOCALVAR is uint𝑘_t[hasatleast 1]
 * @return LOCALVAR[0]
 * @see xchg()
 */
#define lockxchg(MEMORY, LOCALVAR)                                          \
  ({                                                                        \
    static_assert(typescompatible(typeof(*(MEMORY)), typeof(*(LOCALVAR)))); \
    asm("xchg\t%0,%1" : "+%m"(*(MEMORY)), "+r"(*(LOCALVAR)));               \
    *(LOCALVAR);                                                            \
  })

/**
 * Compares and exchanges.
 *
 * @param IFTHING is uint𝑘_t[hasatleast 1] where 𝑘 ∈ {8,16,32,64}
 * @return true if value was exchanged, otherwise false
 * @see lockcmpxchg()
 */
#define cmpxchg(IFTHING, ISEQUALTOME, REPLACEITWITHME)                        \
  ({                                                                          \
    bool DidIt;                                                               \
    autotype(IFTHING) IfThing = (IFTHING);                                    \
    typeof(*IfThing) IsEqualToMe = (ISEQUALTOME);                             \
    typeof(*IfThing) ReplaceItWithMe = (REPLACEITWITHME);                     \
    asm volatile(ZFLAG_ASM("cmpxchg\t%3,%1")                                  \
                 : ZFLAG_CONSTRAINT(DidIt), "+m"(*IfThing), "+a"(IsEqualToMe) \
                 : "r"(ReplaceItWithMe)                                       \
                 : "cc");                                                     \
    DidIt;                                                                    \
  })

/**
 * Compares and exchanges w/ one operation.
 *
 * @param IFTHING is uint𝑘_t[hasatleast 1] where 𝑘 ∈ {8,16,32,64}
 * @return true if value was exchanged, otherwise false
 * @see lockcmpxchg()
 */
#define lockcmpxchg(IFTHING, ISEQUALTOME, REPLACEITWITHME)                    \
  ({                                                                          \
    bool DidIt;                                                               \
    autotype(IFTHING) IfThing = (IFTHING);                                    \
    typeof(*IfThing) IsEqualToMe = (ISEQUALTOME);                             \
    typeof(*IfThing) ReplaceItWithMe = (REPLACEITWITHME);                     \
    asm volatile(ZFLAG_ASM("lock cmpxchg\t%3,%1")                             \
                 : ZFLAG_CONSTRAINT(DidIt), "+m"(*IfThing), "+a"(IsEqualToMe) \
                 : "r"(ReplaceItWithMe)                                       \
                 : "cc");                                                     \
    DidIt;                                                                    \
  })

/**
 * Gets value of extended control register.
 */
#define xgetbv(xcr_register_num)                               \
  ({                                                           \
    unsigned hi, lo;                                           \
    asm("xgetbv" : "=d"(hi), "=a"(lo) : "c"(cr_register_num)); \
    (uint64_t) hi << 32 | lo;                                  \
  })

/**
 * Reads model-specific register.
 * @note programs running as guests won't have authorization
 */
#define rdmsr(msr)                                         \
  ({                                                       \
    uint32_t lo, hi;                                       \
    asm volatile("rdmsr" : "=a"(lo), "=d"(hi) : "c"(msr)); \
    (uint64_t) hi << 32 | lo;                              \
  })

/**
 * Writes model-specific register.
 * @note programs running as guests won't have authorization
 */
#define wrmsr(msr, val)                           \
  do {                                            \
    uint64_t val_ = (val);                        \
    asm volatile("wrmsr"                          \
                 : /* no outputs */               \
                 : "c"(msr), "a"((uint32_t)val_), \
                   "d"((uint32_t)(val_ >> 32)));  \
  } while (0)

/**
 * Tells CPU page tables changed for virtual address.
 * @note programs running as guests won't have authorization
 */
#define invlpg(MEM) \
  asm volatile("invlpg\t(%0)" : /* no outputs */ : "r"(MEM) : "memory")

#define IsAddressCanonicalForm(P)                             \
  ({                                                          \
    intptr_t p2 = (intptr_t)(P);                              \
    (0xffff800000000000l <= p2 && p2 <= 0x00007fffffffffffl); \
  })

/*───────────────────────────────────────────────────────────────────────────│─╗
│ cosmopolitan § bits » implementation details                             ─╬─│┼
╚────────────────────────────────────────────────────────────────────────────│*/

#define __ArithmeticOp1(OP, MEM)                               \
  ({                                                           \
    asm(OP "%z0\t%0" : "+m"(*(MEM)) : /* no inputs */ : "cc"); \
    MEM;                                                       \
  })

#define __ArithmeticOp2(OP, VAL, MEM)                          \
  ({                                                           \
    asm(OP "%z0\t%1,%0" : "+m,m"(*(MEM)) : "i,r"(VAL) : "cc"); \
    MEM;                                                       \
  })

#define __BitOp(OP, BIT, MEM)                                  \
  ({                                                           \
    bool OldBit;                                               \
    if (isconstant(BIT)) {                                     \
      asm(CFLAG_ASM(OP "%z1\t%2,%1")                           \
          : CFLAG_CONSTRAINT(OldBit),                          \
            "+m"((MEM)[(BIT) / (sizeof((MEM)[0]) * CHAR_BIT)]) \
          : "J"((BIT) % (sizeof((MEM)[0]) * CHAR_BIT))         \
          : "cc");                                             \
    } else if (sizeof((MEM)[0]) == 2) {                        \
      asm(CFLAG_ASM(OP "\t%w2,%1")                             \
          : CFLAG_CONSTRAINT(OldBit), "+m"((MEM)[0])           \
          : "r"(BIT)                                           \
          : "cc");                                             \
    } else if (sizeof((MEM)[0]) == 4) {                        \
      asm(CFLAG_ASM(OP "\t%k2,%1")                             \
          : CFLAG_CONSTRAINT(OldBit), "+m"((MEM)[0])           \
          : "r"(BIT)                                           \
          : "cc");                                             \
    } else if (sizeof((MEM)[0]) == 8) {                        \
      asm(CFLAG_ASM(OP "\t%q2,%1")                             \
          : CFLAG_CONSTRAINT(OldBit), "+m"((MEM)[0])           \
          : "r"(BIT)                                           \
          : "cc");                                             \
    }                                                          \
    OldBit;                                                    \
  })

COSMOPOLITAN_C_END_
#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
#endif /* COSMOPOLITAN_LIBC_BITS_H_ */