From: mita@miraclelinux.com (Akinobu Mita)
To: Gabriel Paubert <paubert@iram.es>
Cc: linux-kernel@vger.kernel.org, linux-mips@linux-mips.org,
linux-ia64@vger.kernel.org, Ian Molton <spyro@f2s.com>,
David Howells <dhowells@redhat.com>,
linuxppc-dev@ozlabs.org, Greg Ungerer <gerg@uclinux.org>,
sparclinux@vger.kernel.org,
Miles Bader <uclinux-v850@lsi.nec.co.jp>,
Linus Torvalds <torvalds@osdl.org>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Hirokazu Takata <takata@linux-m32r.org>,
linuxsh-shmedia-dev@lists.sourceforge.net,
linux-m68k@vger.kernel.org,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Richard Henderson <rth@twiddle.net>,
Chris Zankel <chris@zankel.net>,
dev-etrax@axis.com, ultralinux@vger.kernel.org,
Andi Kleen <ak@suse.de>,
linuxsh-dev@lists.sourceforge.net, linux390@de.ibm.com,
Russell King <rmk@arm.linux.org.uk>,
parisc-linux@parisc-linux.org,
Balbir Singh <bsingharora@gmail.com>,
linux@horizon.com
Subject: Re: [patch 14/44] generic hweight{64,32,16,8}()
Date: Mon, 6 Feb 2006 20:52:57 +0900 [thread overview]
Message-ID: <20060206115257.GB11836@miraclelinux.com> (raw)
In-Reply-To: <20060202012637.GA25093@iram.es>
On Thu, Feb 02, 2006 at 02:26:38AM +0100, Gabriel Paubert wrote:
>
> The first step can be implemented slightly better:
>
> unsigned int res = w-((w>>1)&0x55555555);
>
Yes. I've got many advices about hweight speedup.
static unsigned int hweight32(unsigned int w)
{
unsigned int res = w - ((w >> 1) & 0x55555555);
res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
res = (res + (res >> 4)) & 0x0F0F0F0F;
res = res + (res >> 8);
return (res + (res >> 16)) & 0x000000FF;
}
static unsigned int hweight16(unsigned int w)
{
unsigned int res = w - ((w >> 1) & 0x5555);
res = (res & 0x3333) + ((res >> 2) & 0x3333);
res = (res + (res >> 4)) & 0x0F0F;
return (res + (res >> 8)) & 0x00FF;
}
static unsigned int hweight8(unsigned int w)
{
unsigned int res = w - ((w >> 1) & 0x55);
res = (res & 0x33) + ((res >> 2) & 0x33);
return (res + (res >> 4)) & 0x0F;
}
static unsigned long hweight64(__u64 w)
{
#if BITS_PER_LONG < 64
return hweight32((unsigned int)(w >> 32)) +
hweight32((unsigned int)w);
#else
__u64 res = w - ((w >> 1) & 0x5555555555555555ul);
res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
res = res + (res >> 8);
res = res + (res >> 16);
return (res + (res >> 32)) & 0x00000000000000FFul;
#endif
}
next prev parent reply other threads:[~2006-02-06 11:53 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-01 9:02 [patch 00/44] generic bitops Akinobu Mita
2006-02-01 9:02 ` [patch 01/44] ia64: use cpu_set() instead of __set_bit() Akinobu Mita
2006-02-01 9:02 ` [patch 02/44] parisc: add ()-pair in __ffz() macro Akinobu Mita
2006-02-01 9:02 ` [patch 03/44] cris: remove unnecessary local_irq_restore() Akinobu Mita
2006-02-01 9:02 ` [patch 04/44] use non atomic operations for minix_*_bit() and ext2_*_bit() Akinobu Mita
2006-02-01 9:02 ` [patch 05/44] generic {,test_and_}{set,clear,change}_bit() Akinobu Mita
2006-02-03 9:55 ` Martin Waitz
2006-02-06 23:07 ` Russell King
2006-02-01 9:02 ` [patch 06/44] generic __{,test_and_}{set,clear,change}_bit() and test_bit() Akinobu Mita
2006-02-01 9:02 ` [patch 07/44] generic __ffs() Akinobu Mita
2006-02-01 9:02 ` [patch 08/44] generic ffz() Akinobu Mita
2006-02-01 9:02 ` [patch 09/44] generic fls() Akinobu Mita
2006-02-01 9:02 ` [patch 10/44] generic fls64() Akinobu Mita
2006-02-01 9:02 ` [patch 11/44] generic find_{next,first}{,_zero}_bit() Akinobu Mita
2006-02-01 9:02 ` [patch 12/44] generic sched_find_first_bit() Akinobu Mita
2006-02-03 3:58 ` [parisc-linux] " Grant Grundler
2006-02-01 9:02 ` [patch 13/44] generic ffs() Akinobu Mita
2006-02-01 9:02 ` [patch 14/44] generic hweight{64,32,16,8}() Akinobu Mita
2006-02-01 9:06 ` Andi Kleen
2006-02-01 9:26 ` Michael Tokarev
2006-02-01 10:24 ` Andi Kleen
2006-02-02 12:50 ` Akinobu Mita
2006-02-09 5:55 ` [PATCH] alpha: remove __alpha_cix__ and __alpha_fix__ Akinobu Mita
2006-02-09 19:12 ` Richard Henderson
2006-02-10 5:40 ` Akinobu Mita
2006-02-02 1:26 ` [patch 14/44] generic hweight{64,32,16,8}() Gabriel Paubert
2006-02-06 11:52 ` Akinobu Mita [this message]
2006-02-03 8:31 ` Ulrich Eckhardt
2006-02-01 9:02 ` [patch 15/44] generic ext2_{set,clear,test,find_first_zero,find_next_zero}_bit() Akinobu Mita
2006-02-01 11:27 ` Roman Zippel
2006-02-06 11:47 ` Akinobu Mita
2006-02-08 10:41 ` Akinobu Mita
2006-02-01 9:02 ` [patch 16/44] generic ext2_{set,clear}_bit_atomic() Akinobu Mita
2006-02-01 9:02 ` [patch 17/44] generic minix_{test,set,test_and_clear,test,find_first_zero}_bit() Akinobu Mita
2006-02-01 9:02 ` [patch 18/44] alpha: use generic bitops Akinobu Mita
2006-02-01 9:02 ` [patch 19/44] arm: " Akinobu Mita
2006-02-01 9:02 ` [patch 20/44] arm26: " Akinobu Mita
2006-02-01 9:02 ` [patch 21/44] cris: " Akinobu Mita
2006-02-01 9:02 ` [patch 22/44] frv: " Akinobu Mita
2006-02-01 9:02 ` [patch 23/44] h8300: " Akinobu Mita
2006-02-01 9:02 ` [patch 24/44] i386: " Akinobu Mita
2006-02-01 9:02 ` [patch 25/44] ia64: " Akinobu Mita
2006-02-01 9:02 ` [patch 26/44] m32r: " Akinobu Mita
2006-02-01 9:02 ` [patch 27/44] m68k: " Akinobu Mita
2006-02-01 9:02 ` [patch 28/44] m68knommu: " Akinobu Mita
2006-02-01 9:02 ` [patch 29/44] mips: " Akinobu Mita
2006-02-01 9:02 ` [patch 30/44] parisc: " Akinobu Mita
2006-02-01 9:02 ` [patch 31/44] powerpc: " Akinobu Mita
2006-02-01 9:02 ` [patch 32/44] s390: " Akinobu Mita
2006-02-01 9:02 ` [patch 33/44] sh: " Akinobu Mita
2006-02-01 9:02 ` [patch 34/44] sh64: " Akinobu Mita
2006-02-01 9:02 ` [patch 35/44] sparc: " Akinobu Mita
2006-02-01 9:03 ` [patch 36/44] sparc64: " Akinobu Mita
2006-02-01 9:03 ` [patch 37/44] v850: " Akinobu Mita
2006-02-01 9:03 ` [patch 38/44] x86_64: " Akinobu Mita
2006-02-01 9:03 ` [patch 39/44] xtensa: " Akinobu Mita
2006-02-01 9:03 ` [patch 40/44] update include/asm-generic/bitops.h Akinobu Mita
2006-02-01 9:03 ` [patch 41/44] make thread_info.flags an unsigned long Akinobu Mita
2006-02-01 9:03 ` [patch 42/44] ia64: make partial_page.bitmap " Akinobu Mita
2006-02-01 9:03 ` [patch 43/44] ntfs: remove generic_ffs() Akinobu Mita
2006-02-01 9:03 ` [patch 44/44] remove unused generic bitops in include/linux/bitops.h Akinobu Mita
2006-02-06 10:26 ` [patch 11/44] generic find_{next,first}{,_zero}_bit() David Howells
2006-02-07 2:02 ` Akinobu Mita
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