diff options
Diffstat (limited to 'arch/x86/include/asm/word-at-a-time.h')
| -rw-r--r-- | arch/x86/include/asm/word-at-a-time.h | 57 |
1 files changed, 23 insertions, 34 deletions
diff --git a/arch/x86/include/asm/word-at-a-time.h b/arch/x86/include/asm/word-at-a-time.h index e8d7d4941c4c..422a47746657 100644 --- a/arch/x86/include/asm/word-at-a-time.h +++ b/arch/x86/include/asm/word-at-a-time.h @@ -5,45 +5,12 @@ #include <linux/bitops.h> #include <linux/wordpart.h> -/* - * This is largely generic for little-endian machines, but the - * optimal byte mask counting is probably going to be something - * that is architecture-specific. If you have a reliably fast - * bit count instruction, that might be better than the multiply - * and shift, for example. - */ struct word_at_a_time { const unsigned long one_bits, high_bits; }; #define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) } -#ifdef CONFIG_64BIT - -/* - * Jan Achrenius on G+: microoptimized version of - * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56" - * that works for the bytemasks without having to - * mask them first. - */ -static inline long count_masked_bytes(unsigned long mask) -{ - return mask*0x0001020304050608ul >> 56; -} - -#else /* 32-bit case */ - -/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */ -static inline long count_masked_bytes(long mask) -{ - /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */ - long a = (0x0ff0001+mask) >> 23; - /* Fix the 1 for 00 case */ - return a & mask; -} - -#endif - /* Return nonzero if it has a zero */ static inline unsigned long has_zero(unsigned long a, unsigned long *bits, const struct word_at_a_time *c) { @@ -57,6 +24,22 @@ static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, return bits; } +#ifdef CONFIG_64BIT + +/* Keep the initial has_zero() value for both bitmask and size calc */ +#define create_zero_mask(bits) (bits) + +static inline unsigned long zero_bytemask(unsigned long bits) +{ + bits = (bits - 1) & ~bits; + return bits >> 7; +} + +#define find_zero(bits) (__ffs(bits) >> 3) + +#else + +/* Create the final mask for both bytemask and size */ static inline unsigned long create_zero_mask(unsigned long bits) { bits = (bits - 1) & ~bits; @@ -66,11 +49,17 @@ static inline unsigned long create_zero_mask(unsigned long bits) /* The mask we created is directly usable as a bytemask */ #define zero_bytemask(mask) (mask) +/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */ static inline unsigned long find_zero(unsigned long mask) { - return count_masked_bytes(mask); + /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */ + long a = (0x0ff0001+mask) >> 23; + /* Fix the 1 for 00 case */ + return a & mask; } +#endif + /* * Load an unaligned word from kernel space. * |