From owner-svn-src-head@FreeBSD.ORG Tue Mar 20 19:04:01 2012 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 7B465106566B; Tue, 20 Mar 2012 19:04:01 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 4E0868FC16; Tue, 20 Mar 2012 19:04:01 +0000 (UTC) Received: from bigwig.baldwin.cx (bigwig.baldwin.cx [96.47.65.170]) by cyrus.watson.org (Postfix) with ESMTPSA id 0413E46B46; Tue, 20 Mar 2012 15:04:01 -0400 (EDT) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id 654FCB96C; Tue, 20 Mar 2012 15:04:00 -0400 (EDT) From: John Baldwin To: Tijl Coosemans Date: Tue, 20 Mar 2012 14:56:14 -0400 User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p10; KDE/4.5.5; amd64; ; ) References: <201203091148.q29BmuIp005151@svn.freebsd.org> <201203200834.10539.jhb@freebsd.org> <201203201519.12926.tijl@freebsd.org> In-Reply-To: <201203201519.12926.tijl@freebsd.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Message-Id: <201203201456.14375.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (bigwig.baldwin.cx); Tue, 20 Mar 2012 15:04:00 -0400 (EDT) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r232721 - head/sys/x86/include X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 20 Mar 2012 19:04:01 -0000 On Tuesday, March 20, 2012 10:19:07 am Tijl Coosemans wrote: > On Tuesday 20 March 2012 13:34:10 John Baldwin wrote: > > On Friday, March 09, 2012 6:48:56 am Tijl Coosemans wrote: > >> Author: tijl > >> Date: Fri Mar 9 11:48:56 2012 > >> New Revision: 232721 > >> URL: http://svn.freebsd.org/changeset/base/232721 > >> > >> Log: > >> Clean up x86 endian.h: > >> - Remove extern "C". There are no functions with external linkage here. [1] > >> - Rename bswapNN_const(x) to bswapNN_gen(x) to indicate that these macros > >> are generic implementations that can take non-constant arguments. [1] > >> - Split up __GNUCLIKE_ASM && __GNUCLIKE_BUILTIN_CONSTANT_P and deal with > >> each separately. > >> - Replace _LP64 with __amd64__ because asm instructions are machine > >> dependent, not ABI dependent. > >> > >> Submitted by: bde [1] > >> Reviewed by: bde > > > > BTW, I think I found an old "bug" in this file. The _gen() variants > > should only use the _gen() variants of smaller types rather than using > > the version that re-checks __build_constant_p() I think. That is: > > > > Index: x86/include/endian.h > > =================================================================== > > --- endian.h (revision 233184) > > +++ endian.h (working copy) > > @@ -65,9 +65,9 @@ > > > > #define __bswap16_gen(x) (__uint16_t)((x) << 8 | (x) >> 8) > > #define __bswap32_gen(x) \ > > - (((__uint32_t)__bswap16(x) << 16) | __bswap16((x) >> 16)) > > + (((__uint32_t)__bswap16_gen(x) << 16) | __bswap16_gen((x) >> 16)) > > #define __bswap64_gen(x) \ > > - (((__uint64_t)__bswap32(x) << 32) | __bswap32((x) >> 32)) > > + (((__uint64_t)__bswap32_gen(x) << 32) | __bswap32_gen((x) >> 32)) > > > > #ifdef __GNUCLIKE_BUILTIN_CONSTANT_P > > #define __bswap16(x) \ > > > > I ran into this while porting the __builtin_constant_p() functionality > > over to ia64. > > No, on i386 bswap64 with a variable argument currently expands to two > bswap instructions. With your change it would be many shifts and logical > operations. The _gen variants are more like fallback implementations. > If bswapNN cannot be implemented directly it is split up. If those > smaller problems can be implemented directly, good, if not split it up > again and so on. Oh, I now parse the comment in __bswap64_var() correctly. That's fugly. Still, it seems that if I keep the patch to port this to ia64 (so it can do constants as constants), then it will need to use this approach since it won't have the i386 problem (in its case the _gen variants are only used for constants). -- John Baldwin