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Linux/lib/clz_ctz.c

  1 /*
  2  * lib/clz_ctz.c
  3  *
  4  * Copyright (C) 2013 Chanho Min <chanho.min@lge.com>
  5  *
  6  * This program is free software; you can redistribute it and/or modify
  7  * it under the terms of the GNU General Public License version 2 as
  8  * published by the Free Software Foundation.
  9  * The functions in this file aren't called directly, but are required by
 10  * GCC builtins such as __builtin_ctz, and therefore they can't be removed
 11  * despite appearing unreferenced in kernel source.
 12  *
 13  * __c[lt]z[sd]i2 can be overridden by linking arch-specific versions.
 14  */
 15 
 16 #include <linux/export.h>
 17 #include <linux/kernel.h>
 18 
 19 int __weak __ctzsi2(int val);
 20 int __weak __ctzsi2(int val)
 21 {
 22         return __ffs(val);
 23 }
 24 EXPORT_SYMBOL(__ctzsi2);
 25 
 26 int __weak __clzsi2(int val);
 27 int __weak __clzsi2(int val)
 28 {
 29         return 32 - fls(val);
 30 }
 31 EXPORT_SYMBOL(__clzsi2);
 32 
 33 int __weak __clzdi2(long val);
 34 int __weak __ctzdi2(long val);
 35 #if BITS_PER_LONG == 32
 36 
 37 int __weak __clzdi2(long val)
 38 {
 39         return 32 - fls((int)val);
 40 }
 41 EXPORT_SYMBOL(__clzdi2);
 42 
 43 int __weak __ctzdi2(long val)
 44 {
 45         return __ffs((u32)val);
 46 }
 47 EXPORT_SYMBOL(__ctzdi2);
 48 
 49 #elif BITS_PER_LONG == 64
 50 
 51 int __weak __clzdi2(long val)
 52 {
 53         return 64 - fls64((u64)val);
 54 }
 55 EXPORT_SYMBOL(__clzdi2);
 56 
 57 int __weak __ctzdi2(long val)
 58 {
 59         return __ffs64((u64)val);
 60 }
 61 EXPORT_SYMBOL(__ctzdi2);
 62 
 63 #else
 64 #error BITS_PER_LONG not 32 or 64
 65 #endif
 66 

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