2aba6925fd
Switch x86_64 to generic find_first_bit. The x86_64-specific implementation is not removed. Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm> Signed-off-by: Ingo Molnar <mingo@elte.hu>
109 lines
2.9 KiB
C
109 lines
2.9 KiB
C
#ifndef CONFIG_GENERIC_FIND_FIRST_BIT
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#include <linux/bitops.h>
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#undef find_first_zero_bit
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#undef find_first_bit
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static inline long
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__find_first_zero_bit(const unsigned long * addr, unsigned long size)
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{
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long d0, d1, d2;
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long res;
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/*
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* We must test the size in words, not in bits, because
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* otherwise incoming sizes in the range -63..-1 will not run
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* any scasq instructions, and then the flags used by the je
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* instruction will have whatever random value was in place
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* before. Nobody should call us like that, but
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* find_next_zero_bit() does when offset and size are at the
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* same word and it fails to find a zero itself.
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*/
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size += 63;
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size >>= 6;
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if (!size)
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return 0;
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asm volatile(
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" repe; scasq\n"
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" je 1f\n"
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" xorq -8(%%rdi),%%rax\n"
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" subq $8,%%rdi\n"
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" bsfq %%rax,%%rdx\n"
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"1: subq %[addr],%%rdi\n"
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" shlq $3,%%rdi\n"
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" addq %%rdi,%%rdx"
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:"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
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:"0" (0ULL), "1" (size), "2" (addr), "3" (-1ULL),
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[addr] "S" (addr) : "memory");
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/*
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* Any register would do for [addr] above, but GCC tends to
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* prefer rbx over rsi, even though rsi is readily available
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* and doesn't have to be saved.
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*/
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return res;
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}
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/**
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* find_first_zero_bit - find the first zero bit in a memory region
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* @addr: The address to start the search at
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* @size: The maximum size to search
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*
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* Returns the bit-number of the first zero bit, not the number of the byte
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* containing a bit.
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*/
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long find_first_zero_bit(const unsigned long * addr, unsigned long size)
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{
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return __find_first_zero_bit (addr, size);
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}
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static inline long
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__find_first_bit(const unsigned long * addr, unsigned long size)
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{
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long d0, d1;
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long res;
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/*
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* We must test the size in words, not in bits, because
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* otherwise incoming sizes in the range -63..-1 will not run
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* any scasq instructions, and then the flags used by the jz
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* instruction will have whatever random value was in place
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* before. Nobody should call us like that, but
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* find_next_bit() does when offset and size are at the same
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* word and it fails to find a one itself.
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*/
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size += 63;
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size >>= 6;
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if (!size)
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return 0;
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asm volatile(
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" repe; scasq\n"
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" jz 1f\n"
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" subq $8,%%rdi\n"
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" bsfq (%%rdi),%%rax\n"
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"1: subq %[addr],%%rdi\n"
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" shlq $3,%%rdi\n"
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" addq %%rdi,%%rax"
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:"=a" (res), "=&c" (d0), "=&D" (d1)
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:"0" (0ULL), "1" (size), "2" (addr),
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[addr] "r" (addr) : "memory");
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return res;
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}
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/**
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* find_first_bit - find the first set bit in a memory region
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* @addr: The address to start the search at
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* @size: The maximum size to search
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*
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* Returns the bit-number of the first set bit, not the number of the byte
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* containing a bit.
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*/
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long find_first_bit(const unsigned long * addr, unsigned long size)
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{
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return __find_first_bit(addr,size);
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}
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#include <linux/module.h>
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EXPORT_SYMBOL(find_first_bit);
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EXPORT_SYMBOL(find_first_zero_bit);
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#endif
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