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55 lines
1.2 KiB
C
55 lines
1.2 KiB
C
#include <common/stddef.h>
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/**
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* @brief 统计二进制数的前导0
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*
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* @param x 待统计的数
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* @return int 结果
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*/
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static __always_inline int __clz(uint32_t x)
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{
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asm volatile("bsr %%eax, %%eax\n\t"
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"xor $0x1f, %%eax\n\t"
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: "=a"(x)
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: "a"(x)
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: "memory");
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return x;
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}
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/**
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* @brief 统计二进制数的前导0 (宽度为unsigned long)
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*
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* @param x 待统计的数
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* @return int 结果
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*/
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static __always_inline int __clzl(unsigned long x)
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{
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int res = 0;
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asm volatile("cltq\n\t"
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"bsr %%rax, %%rax\n\t"
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"xor $0x3f, %%rax\n\t"
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"mov %%eax,%0\n\t"
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: "=m"(res)
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: "a"(x)
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: "memory");
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return res;
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}
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/**
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* @brief 统计二进制数的前导0（宽度为unsigned long long）
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*
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* @param x 待统计的数
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* @return int 结果
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*/
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static __always_inline int __clzll(unsigned long long x)
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{
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int res = 0;
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asm volatile("cltq\n\t"
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"bsr %%rax, %%rax\n\t"
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"xor $0x3f, %%rax\n\t"
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"mov %%eax,%0\n\t"
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: "=m"(res)
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: "a"(x)
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: "memory");
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return res;
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} |