Date: Thu, 15 Jan 2009 12:58:16 +0100 From: Christoph Mallon <christoph.mallon@gmx.de> To: Alexey Dokuchaev <danfe@FreeBSD.org> Cc: src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, stas@FreeBSD.org, gonzo@FreeBSD.org, svn-src-head@FreeBSD.org, "M. Warner Losh" <imp@bsdimp.com> Subject: Re: svn commit: r187251 - head/sys/mips/malta Message-ID: <496F24D8.2040104@gmx.de> In-Reply-To: <20090115114407.GA67726@FreeBSD.org> References: <200901142232.n0EMWhGw055895@svn.freebsd.org> <20090115020752.52566769.stas@FreeBSD.org> <20090114.190527.1058804377.imp@bsdimp.com> <20090115114407.GA67726@FreeBSD.org>
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Alexey Dokuchaev schrieb: > On Wed, Jan 14, 2009 at 07:05:27PM -0700, M. Warner Losh wrote: >> In message: <20090115020752.52566769.stas@FreeBSD.org> >> Stanislav Sedov <stas@FreeBSD.org> writes: >> : > + shift = 8 * (reg & 3); >> : > >> : >> : Would it make sense to replace this with >> : > + shift = (reg & 3) << 3; >> : >> : to not rely on possible compiler optimizations? >> >> I don't think that it matters all that much these days... > > But the name "shift" kinda suggests << instead of *, no? The value *is* a shift amount (see its uses a few lines down). Its name does not imply the way it is calculated, but what it is used for. BTW: Even the most cheap compilers emit shift instructions for multiplication by a power of two. The new code also is clearly faster then the old - quite some code gets generated for switches.
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