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

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