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

INCLUDED FROM

DEFINITIONS

1. prep_zero_mask
2. find_zero
3. has_zero
4. count_masked_bytes
5. count_masked_bytes
6. has_zero
7. prep_zero_mask
8. create_zero_mask
9. find_zero

   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 
  10 struct 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 */
  17 static 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 
  25 static 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 
  41 static 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  */
  60 struct 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  */
  74 static 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 */
  82 static 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 */
  93 static 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 
 100 static 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 
 105 static 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 
 114 static 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 */