LXR linux/include/asm-generic/word-at-a-time.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _ASM_WORD_AT_A_TIME_H
   3#define _ASM_WORD_AT_A_TIME_H
   4
   5#include <linux/kernel.h>
   6#include <asm/byteorder.h>
   7
   8#ifdef __BIG_ENDIAN
   9
  10struct word_at_a_time {
  11        const unsigned long high_bits, low_bits;
  12};
  13
  14#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0xfe) + 1, REPEAT_BYTE(0x7f) }
  15
  16/* Bit set in the bytes that have a zero */
  17static inline long prep_zero_mask(unsigned long val, unsigned long rhs, const struct word_at_a_time *c)
  18{
  19        unsigned long mask = (val & c->low_bits) + c->low_bits;
  20        return ~(mask | rhs);
  21}
  22
  23#define create_zero_mask(mask) (mask)
  24
  25static inline long find_zero(unsigned long mask)
  26{
  27        long byte = 0;
  28#ifdef CONFIG_64BIT
  29        if (mask >> 32)
  30                mask >>= 32;
  31        else
  32                byte = 4;
  33#endif
  34        if (mask >> 16)
  35                mask >>= 16;
  36        else
  37                byte += 2;
  38        return (mask >> 8) ? byte : byte + 1;
  39}
  40
  41static inline bool has_zero(unsigned long val, unsigned long *data, const struct word_at_a_time *c)
  42{
  43        unsigned long rhs = val | c->low_bits;
  44        *data = rhs;
  45        return (val + c->high_bits) & ~rhs;
  46}
  47
  48#ifndef zero_bytemask
  49#define zero_bytemask(mask) (~1ul << __fls(mask))
  50#endif
  51
  52#else
  53
  54/*
  55 * The optimal byte mask counting is probably going to be something
  56 * that is architecture-specific. If you have a reliably fast
  57 * bit count instruction, that might be better than the multiply
  58 * and shift, for example.
  59 */
  60struct word_at_a_time {
  61        const unsigned long one_bits, high_bits;
  62};
  63
  64#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
  65
  66#ifdef CONFIG_64BIT
  67
  68/*
  69 * Jan Achrenius on G+: microoptimized version of
  70 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
  71 * that works for the bytemasks without having to
  72 * mask them first.
  73 */
  74static inline long count_masked_bytes(unsigned long mask)
  75{
  76        return mask*0x0001020304050608ul >> 56;
  77}
  78
  79#else   /* 32-bit case */
  80
  81/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
  82static inline long count_masked_bytes(long mask)
  83{
  84        /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
  85        long a = (0x0ff0001+mask) >> 23;
  86        /* Fix the 1 for 00 case */
  87        return a & mask;
  88}
  89
  90#endif
  91
  92/* Return nonzero if it has a zero */
  93static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c)
  94{
  95        unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
  96        *bits = mask;
  97        return mask;
  98}
  99
 100static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
 101{
 102        return bits;
 103}
 104
 105static inline unsigned long create_zero_mask(unsigned long bits)
 106{
 107        bits = (bits - 1) & ~bits;
 108        return bits >> 7;
 109}
 110
 111/* The mask we created is directly usable as a bytemask */
 112#define zero_bytemask(mask) (mask)
 113
 114static inline unsigned long find_zero(unsigned long mask)
 115{
 116        return count_masked_bytes(mask);
 117}
 118
 119#endif /* __BIG_ENDIAN */
 120
 121#endif /* _ASM_WORD_AT_A_TIME_H */
 122