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/**
This file includes code copied from three source files in the Linux kernel
v 2.6.23.1:
- include/asm-generic/bitops/fls.h
- include/asm-i386/bitops.h
- include/asm-x86_64/bitops.h
The second and third files contain this notice:
* Copyright 1992, Linus Torvalds.
And of course the kernel is distributed under the terms of the GPL v2.
*/
#ifndef AN_FLS_H
#define AN_FLS_H
#include <stdint.h>
#include <assert.h>
/**
* fls - find last (most-significant) bit set
*
* @x: the word to search
*
* This is defined the same way as ffs.
*
* Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
*/
static inline int an_fls(int x);
/**
* flsB() = fls() - 1.
*
* Note that x MUST be > 0.
*/
static inline uint8_t an_flsB(uint32_t x);
/**** Below this line are the implementations for different CPUs. ****/
#if AN_I386
static inline int an_fls(int x) {
int r;
__asm__("bsrl %1,%0\n\t"
"jnz 1f\n\t"
"movl $-1,%0\n"
"1:" : "=r" (r) : "rm" (x));
return r+1;
}
static inline uint8_t an_flsB(uint32_t x) {
int r;
assert(x);
__asm__("bsrl %1,%0\n\t"
"jnz 1f\n\t"
"movl $-1,%0\n"
"1:" : "=r" (r) : "rm" (x));
return r;
}
#elif AN_X86_64
static __inline__ int an_fls(int x) {
int r;
__asm__("bsrl %1,%0\n\t"
"cmovzl %2,%0"
: "=&r" (r) : "rm" (x), "rm" (-1));
return r+1;
}
static inline uint8_t an_flsB(uint32_t x) {
int r;
assert(x);
__asm__("bsrl %1,%0\n\t"
"cmovzl %2,%0"
: "=&r" (r) : "rm" (x), "rm" (-1));
return r;
}
#else
static inline int an_fls(int x) {
int r = 32;
if (!x)
return 0;
if (!(x & 0xffff0000u)) {
x <<= 16;
r -= 16;
}
if (!(x & 0xff000000u)) {
x <<= 8;
r -= 8;
}
if (!(x & 0xf0000000u)) {
x <<= 4;
r -= 4;
}
if (!(x & 0xc0000000u)) {
x <<= 2;
r -= 2;
}
if (!(x & 0x80000000u)) {
x <<= 1;
r -= 1;
}
return r;
}
static inline uint8_t an_flsB(uint32_t x) {
int r = 31;
assert(x);
if (!(x & 0xffff0000u)) {
x <<= 16;
r -= 16;
}
if (!(x & 0xff000000u)) {
x <<= 8;
r -= 8;
}
if (!(x & 0xf0000000u)) {
x <<= 4;
r -= 4;
}
if (!(x & 0xc0000000u)) {
x <<= 2;
r -= 2;
}
if (!(x & 0x80000000u)) {
x <<= 1;
r -= 1;
}
return r;
}
#endif
#endif
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