From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicolas Pitre Date: Thu, 26 Jan 2006 16:30:43 +0000 Subject: Re: [parisc-linux] Re: [PATCH 3/6] C-language equivalents of Message-Id: List-Id: References: <20060125112625.GA18584@miraclelinux.com> <20060125113206.GD18584@miraclelinux.com> <20060125200250.GA26443@flint.arm.linux.org.uk> <20060126000618.GA5592@twiddle.net> <20060126085540.GA15377@flint.arm.linux.org.uk> <20060126161849.GA13632@colo.lackof.org> In-Reply-To: <20060126161849.GA13632@colo.lackof.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Grant Grundler Cc: Akinobu Mita , lkml , Ivan Kokshaysky , Ian Molton , dev-etrax@axis.com, David Howells , Yoshinori Sato , Linus Torvalds , linux-ia64@vger.kernel.org, Hirokazu Takata , linux-m68k@vger.kernel.org, Greg Ungerer , 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 , Andi Kleen , Chris Zankel 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