From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH] compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16() Date: Mon, 09 May 2016 12:16:11 +0200 Message-ID: <75773040.xkfFJb3GoQ@wuerfel> References: <20160506145810.04a319d3@canb.auug.org.au> <20160509163302.59f3f6a2@canb.auug.org.au> <1462786493.5531.1.camel@ellerman.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from mout.kundenserver.de ([217.72.192.73]:58770 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750927AbcEIKQ1 (ORCPT ); Mon, 9 May 2016 06:16:27 -0400 In-Reply-To: <1462786493.5531.1.camel@ellerman.id.au> Sender: linux-next-owner@vger.kernel.org List-ID: To: Michael Ellerman Cc: Stephen Rothwell , Josh Poimboeuf , Andrew Morton , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds On Monday 09 May 2016 19:34:53 Michael Ellerman wrote: > On Mon, 2016-05-09 at 16:33 +1000, Stephen Rothwell wrote: > > On Mon, 9 May 2016 10:59:27 +1000 Stephen Rothwell wrote: > > > On Fri, 6 May 2016 09:22:25 -0500 Josh Poimboeuf wrote: > > > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > > > > index eeae401..3d5202e 100644 > > > > --- a/include/linux/compiler-gcc.h > > > > +++ b/include/linux/compiler-gcc.h > > > > @@ -246,7 +246,7 @@ > > > > #define __HAVE_BUILTIN_BSWAP32__ > > > > #define __HAVE_BUILTIN_BSWAP64__ > > > > #endif > > > > -#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600) > > > > +#if GCC_VERSION >= 40800 > > > > #define __HAVE_BUILTIN_BSWAP16__ > > > > #endif > > > > #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */ > > > > Tested-by: Stephen Rothwell Acked-by: Arnd Bergmann > > Michael, do you want to pass the fix patch on, or will I submit it > > directly to Linus? > > I'm happy for you to send it, I haven't actually hit the bug myself. I found the commit in gcc-4.8 that replaced the powerpc-specific implementation of __builtin_bswap16 with an architecture-independent one. Apparently the powerpc version (gcc-4.6 and 4.7) just mapped to the lhbrx/sthbrx instructions, so it ended up not being a constant, though the intent of the patch was mainly to add support for the builtin to x86. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624 has the patch that went into gcc-4.8 and more information. Arnd