diff options
Diffstat (limited to 'arch/x86_64/lib/bitops_64.c')
| -rw-r--r-- | arch/x86_64/lib/bitops_64.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/arch/x86_64/lib/bitops_64.c b/arch/x86_64/lib/bitops_64.c new file mode 100644 index 00000000000..95b6d9639fb --- /dev/null +++ b/arch/x86_64/lib/bitops_64.c @@ -0,0 +1,175 @@ +#include <linux/bitops.h> + +#undef find_first_zero_bit +#undef find_next_zero_bit +#undef find_first_bit +#undef find_next_bit + +static inline long +__find_first_zero_bit(const unsigned long * addr, unsigned long size) +{ + long d0, d1, d2; + long res; + + /* + * We must test the size in words, not in bits, because + * otherwise incoming sizes in the range -63..-1 will not run + * any scasq instructions, and then the flags used by the je + * instruction will have whatever random value was in place + * before. Nobody should call us like that, but + * find_next_zero_bit() does when offset and size are at the + * same word and it fails to find a zero itself. + */ + size += 63; + size >>= 6; + if (!size) + return 0; + asm volatile( + " repe; scasq\n" + " je 1f\n" + " xorq -8(%%rdi),%%rax\n" + " subq $8,%%rdi\n" + " bsfq %%rax,%%rdx\n" + "1: subq %[addr],%%rdi\n" + " shlq $3,%%rdi\n" + " addq %%rdi,%%rdx" + :"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2) + :"0" (0ULL), "1" (size), "2" (addr), "3" (-1ULL), + [addr] "S" (addr) : "memory"); + /* + * Any register would do for [addr] above, but GCC tends to + * prefer rbx over rsi, even though rsi is readily available + * and doesn't have to be saved. + */ + return res; +} + +/** + * find_first_zero_bit - find the first zero bit in a memory region + * @addr: The address to start the search at + * @size: The maximum size to search + * + * Returns the bit-number of the first zero bit, not the number of the byte + * containing a bit. + */ +long find_first_zero_bit(const unsigned long * addr, unsigned long size) +{ + return __find_first_zero_bit (addr, size); +} + +/** + * find_next_zero_bit - find the first zero bit in a memory region + * @addr: The address to base the search on + * @offset: The bitnumber to start searching at + * @size: The maximum size to search + */ +long find_next_zero_bit (const unsigned long * addr, long size, long offset) +{ + const unsigned long * p = addr + (offset >> 6); + unsigned long set = 0; + unsigned long res, bit = offset&63; + + if (bit) { + /* + * Look for zero in first word + */ + asm("bsfq %1,%0\n\t" + "cmoveq %2,%0" + : "=r" (set) + : "r" (~(*p >> bit)), "r"(64L)); + if (set < (64 - bit)) + return set + offset; + set = 64 - bit; + p++; + } + /* + * No zero yet, search remaining full words for a zero + */ + res = __find_first_zero_bit (p, size - 64 * (p - addr)); + + return (offset + set + res); +} + +static inline long +__find_first_bit(const unsigned long * addr, unsigned long size) +{ + long d0, d1; + long res; + + /* + * We must test the size in words, not in bits, because + * otherwise incoming sizes in the range -63..-1 will not run + * any scasq instructions, and then the flags used by the jz + * instruction will have whatever random value was in place + * before. Nobody should call us like that, but + * find_next_bit() does when offset and size are at the same + * word and it fails to find a one itself. + */ + size += 63; + size >>= 6; + if (!size) + return 0; + asm volatile( + " repe; scasq\n" + " jz 1f\n" + " subq $8,%%rdi\n" + " bsfq (%%rdi),%%rax\n" + "1: subq %[addr],%%rdi\n" + " shlq $3,%%rdi\n" + " addq %%rdi,%%rax" + :"=a" (res), "=&c" (d0), "=&D" (d1) + :"0" (0ULL), "1" (size), "2" (addr), + [addr] "r" (addr) : "memory"); + return res; +} + +/** + * find_first_bit - find the first set bit in a memory region + * @addr: The address to start the search at + * @size: The maximum size to search + * + * Returns the bit-number of the first set bit, not the number of the byte + * containing a bit. + */ +long find_first_bit(const unsigned long * addr, unsigned long size) +{ + return __find_first_bit(addr,size); +} + +/** + * find_next_bit - find the first set bit in a memory region + * @addr: The address to base the search on + * @offset: The bitnumber to start searching at + * @size: The maximum size to search + */ +long find_next_bit(const unsigned long * addr, long size, long offset) +{ + const unsigned long * p = addr + (offset >> 6); + unsigned long set = 0, bit = offset & 63, res; + + if (bit) { + /* + * Look for nonzero in the first 64 bits: + */ + asm("bsfq %1,%0\n\t" + "cmoveq %2,%0\n\t" + : "=r" (set) + : "r" (*p >> bit), "r" (64L)); + if (set < (64 - bit)) + return set + offset; + set = 64 - bit; + p++; + } + /* + * No set bit yet, search remaining full words for a bit + */ + res = __find_first_bit (p, size - 64 * (p - addr)); + return (offset + set + res); +} + +#include <linux/module.h> + +EXPORT_SYMBOL(find_next_bit); +EXPORT_SYMBOL(find_first_bit); +EXPORT_SYMBOL(find_first_zero_bit); +EXPORT_SYMBOL(find_next_zero_bit); |