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From: Nicolas Pitre <nico@cam.org>
To: Grant Grundler <grundler@parisc-linux.org>
Cc: Akinobu Mita <mita@miraclelinux.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Ian Molton <spyro@f2s.com>,
	dev-etrax@axis.com, David Howells <dhowells@redhat.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Linus Torvalds <torvalds@osdl.org>,
	linux-ia64@vger.kernel.org,
	Hirokazu Takata <takata@linux-m32r.org>,
	linux-m68k@vger.kernel.org, Greg Ungerer <gerg@uclinux.org>,
	linux-mips@linux-mips.org, parisc-linux@parisc-linux.org,
	linuxppc-dev@ozlabs.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 <uclinux-v850@lsi.nec.co.jp>, Andi Kleen <ak@suse.de>,
	Chris Zankel <chris@zankel.net>
Subject: Re: [parisc-linux] Re: [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h
Date: Thu, 26 Jan 2006 11:30:43 -0500 (EST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0601261128280.16649@localhost.localdomain> (raw)
In-Reply-To: <20060126161849.GA13632@colo.lackof.org>

On Thu, 26 Jan 2006, Grant Grundler wrote:

> On Thu, Jan 26, 2006 at 08:55:41AM +0000, Russell King wrote:
> > Unfortunately that's not correct.  You do not appear to have checked
> > the compiler output like I did - this code does _not_ generate
> > constant shifts.
> 
> Russell,
> By "written stupidly", I thought Richard meant they could have
> used constants instead of "s".  e.g.:
> 	if (word << 16 == 0) { b += 16; word >>= 16); }
> 	if (word << 24 == 0) { b +=  8; word >>=  8); }
> 	if (word << 28 == 0) { b +=  4; word >>=  4); }
> 
> But I prefer what Edgar Toernig suggested.

It is just as bad on ARM since it requires large constants that cannot 
be expressed with immediate litteral values.  The constant shift 
approach is really the best on ARM.


Nicolas

  reply	other threads:[~2006-01-26 16:30 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-01-25 11:26 [PATCH 0/6] RFC: use include/asm-generic/bitops.h Akinobu Mita
2006-01-25 11:28 ` [PATCH 1/6] {set,clear,test}_bit() related cleanup Akinobu Mita
2006-01-25 11:46   ` Andi Kleen
2006-01-26 16:14   ` Pavel Machek
2006-01-26 16:47     ` Russell King
2006-01-26 19:14     ` Paul Jackson
2006-01-25 11:30 ` [PATCH 2/6] use non atomic operations for minix_*_bit() and ext2_*_bit() Akinobu Mita
2006-01-25 11:32 ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Akinobu Mita
2006-01-25 11:54   ` Keith Owens
2006-01-26  2:13     ` Akinobu Mita
2006-01-26  2:19       ` Akinobu Mita
2006-01-25 20:02   ` Russell King
2006-01-25 20:59     ` Grant Grundler
2006-01-26  3:27       ` Akinobu Mita
2006-01-26  3:29         ` [PATCH 1/12] generic *_bit() Akinobu Mita
2006-02-01 15:11           ` Chen, Kenneth W
2006-02-01 18:02             ` Christoph Hellwig
2006-02-01 18:07               ` Chen, Kenneth W
2006-02-01 19:19                 ` Russell King
2006-02-01 19:25                   ` Chen, Kenneth W
2006-02-01 19:35                     ` Russell King
2006-02-03 10:24                   ` Geert Uytterhoeven
2006-02-03 10:27                     ` Russell King
2006-02-01 19:39                 ` Grant Grundler
2006-02-01 21:41                   ` Chen, Kenneth W
2006-02-01 22:09                     ` Grant Grundler
2006-02-01 22:49                       ` Anton Altaparmakov
2006-02-02  0:08                         ` Grant Grundler
2006-02-02  8:52                           ` Anton Altaparmakov
2006-02-02 10:13                             ` Andreas Schwab
2006-02-02 22:43                 ` Paul Mackerras
2006-01-26  3:30         ` [PATCH 2/12] generic __ffs() Akinobu Mita
2006-01-26  3:31         ` [PATCH 3/12] generic ffz() Akinobu Mita
2006-01-26  8:21           ` Michael Tokarev
2006-01-27  6:39             ` [PATCH] parisc: add ()-pair in __ffs() Akinobu Mita
2006-01-26  3:32         ` [PATCH 4/12] generic fls() and fls64() Akinobu Mita
2006-01-26  3:33         ` [PATCH 5/12] generic find_{next,first}{,_zero}_bit() Akinobu Mita
2006-01-26  3:34         ` [PATCH 6/12] generic sched_find_first_bit() Akinobu Mita
2006-01-26  3:35         ` [PATCH 7/12] generic ffs() Akinobu Mita
2006-01-26  3:36         ` [PATCH 8/12] generic hweight{32,16,8}() Akinobu Mita
2006-01-26  7:12           ` Balbir Singh
2006-01-26 10:04             ` Rutger Nijlunsing
2006-01-27  4:55             ` Akinobu Mita
2006-01-27  5:40               ` Balbir Singh
2006-01-27  6:40                 ` Akinobu Mita
2006-01-31 11:14                   ` Balbir Singh
2006-01-26 18:57           ` Bryan O'Sullivan
2006-01-27  4:43             ` Akinobu Mita
2006-01-27  5:23               ` Bryan O'Sullivan
2006-01-26  3:36         ` [PATCH 9/12] generic hweight64() Akinobu Mita
2006-01-26  7:05           ` Balbir Singh
2006-01-26  3:38         ` [PATCH 10/12] generic ext2_{set,clear,test,find_first_zero,find_next_zero}_bit() Akinobu Mita
2006-01-26  3:38         ` [PATCH 11/12] generic ext2_{set,clear}_bit_atomic() Akinobu Mita
2006-01-26  3:39         ` [PATCH 12/12] generic minix_{test,set,test_and_clear,test,find_first_zero}_bit() Akinobu Mita
2006-01-25 23:25     ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Ian Molton
2006-01-26  0:06     ` Richard Henderson
2006-01-26  4:34       ` Edgar Toernig
2006-01-26 17:30         ` Richard Henderson
2006-01-26  8:55       ` Russell King
2006-01-26 16:18         ` [parisc-linux] " Grant Grundler
2006-01-26 16:30           ` Nicolas Pitre [this message]
2006-01-26 16:40           ` Russell King
2006-01-26 23:04             ` Grant Grundler
2006-01-26 23:03               ` Russell King
2006-01-29  7:12                 ` Stuart Brady
2006-01-30  4:03                   ` David S. Miller
2006-01-30 17:06                   ` Ralf Baechle
2006-01-30 19:50                     ` Stuart Brady
2006-01-30 23:02                       ` David S. Miller
2006-01-27  0:28               ` [parisc-linux] Re: [PATCH 3/6] C-language equivalents of John David Anglin
2006-01-27 12:51   ` [PATCH 3/6] C-language equivalents of include/asm-*/bitops.h Hirokazu Takata
2006-01-30  3:29     ` Akinobu Mita
2006-01-25 11:34 ` [PATCH 5/6] fix warning on test_ti_thread_flag() Akinobu Mita
2006-01-25 12:28   ` Geert Uytterhoeven
2006-01-25 22:28   ` Paul Mackerras
2006-01-26  0:04     ` David S. Miller
2006-01-25 11:35 ` [PATCH 6/6] remove unused generic bitops in include/linux/bitops.h Akinobu Mita
     [not found] ` <20060125113336.GE18584@miraclelinux.com>
2006-01-26  1:49   ` [PATCH 4/6] use include/asm-generic/bitops for each architecture Akinobu Mita
2006-01-26  2:37     ` Grant Grundler
2006-01-27 13:04     ` Hirokazu Takata
2006-01-30  3:15       ` Akinobu Mita

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