From mboxrd@z Thu Jan 1 00:00:00 1970 From: Akinobu Mita Date: Wed, 01 Feb 2006 09:02:33 +0000 Subject: [patch 09/44] generic fls() Message-Id: <20060201090323.100733000@localhost.localdomain> List-Id: References: <20060201090224.536581000@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org Cc: Richard Henderson , Ivan Kokshaysky , Russell King , Ian Molton , dev-etrax@axis.com, Yoshinori Sato , Hirokazu Takata , Greg Ungerer , linux-mips@linux-mips.org, linux390@de.ibm.com, linuxsh-dev@lists.sourceforge.net, linuxsh-shmedia-dev@lists.sourceforge.net, sparclinux@vger.kernel.org, ultralinux@vger.kernel.org, Miles Bader , Akinobu Mita This patch introduces the C-language equivalent of the function: int fls(int x); In include/asm-generic/bitops/fls.h This code largely copied from: include/linux/bitops.h Signed-off-by: Akinobu Mita include/asm-generic/bitops/fls.h | 41 +++++++++++++++++++++++++++++++++++++++ 1 files changed, 41 insertions(+) Index: 2.6-git/include/asm-generic/bitops/fls.h =================================--- /dev/null +++ 2.6-git/include/asm-generic/bitops/fls.h @@ -0,0 +1,41 @@ +#ifndef _ASM_GENERIC_BITOPS_FLS_H_ +#define _ASM_GENERIC_BITOPS_FLS_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 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; +} + +#endif /* _ASM_GENERIC_BITOPS_FLS_H_ */ --