From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750983AbcEIGdH (ORCPT ); Mon, 9 May 2016 02:33:07 -0400 Received: from ozlabs.org ([103.22.144.67]:35417 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750879AbcEIGdF (ORCPT ); Mon, 9 May 2016 02:33:05 -0400 Date: Mon, 9 May 2016 16:33:02 +1000 From: Stephen Rothwell To: Josh Poimboeuf Cc: Michael Ellerman , Andrew Morton , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Linus Torvalds Subject: Re: [PATCH] compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16() Message-ID: <20160509163302.59f3f6a2@canb.auug.org.au> In-Reply-To: <20160509105927.68dfa6d2@canb.auug.org.au> References: <20160506145810.04a319d3@canb.auug.org.au> <20160505224429.3b8f3837bcb0281932cfe03f@linux-foundation.org> <20160506160916.3192f615@canb.auug.org.au> <1462517712.8044.2.camel@ellerman.id.au> <20160506142225.rtp2swmdgfzucfjl@treble> <20160509105927.68dfa6d2@canb.auug.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, On Mon, 9 May 2016 10:59:27 +1000 Stephen Rothwell wrote: > > On Fri, 6 May 2016 09:22:25 -0500 Josh Poimboeuf wrote: > > > > I've also seen no problems on powerpc with 4.4 and 4.8. I suspect it's > > specific to gcc 4.6. Stephen, can you confirm this patch fixes it? > > That will obviously fix the problem for us (since it will effectively > restore the code to what it was before the other commit for our gcc > 4.6.3 builds and we have not seen it in other builds). I will add this > patch to linux-next today. > > And since "byteswap: try to avoid __builtin_constant_p gcc bug" is not > in Linus' tree, hopefully we can have this fix applied soon. > > > From: Josh Poimboeuf > > Subject: [PATCH] compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16() > > > > gcc support for __builtin_bswap16() was supposedly added for powerpc in > > gcc 4.6, and was then later added for other architectures in gcc 4.8. > > > > However, Stephen Rothwell reported that attempting to use it on powerpc > > in gcc 4.6 fails with: > > > > lib/vsprintf.c:160:2: error: initializer element is not constant > > lib/vsprintf.c:160:2: error: (near initialization for 'decpair[0]') > > lib/vsprintf.c:160:2: error: initializer element is not constant > > lib/vsprintf.c:160:2: error: (near initialization for 'decpair[1]') > > lib/vsprintf.c:160:2: error: initializer element is not constant > > lib/vsprintf.c:160:2: error: (near initialization for 'decpair[2]') > > lib/vsprintf.c:160:2: error: initializer element is not constant > > lib/vsprintf.c:160:2: error: (near initialization for 'decpair[3]') > > lib/vsprintf.c:160:2: error: initializer element is not constant > > > > I'm not entirely sure what those errors mean, but I don't see them on > > gcc 4.8. So let's consider gcc 4.8 to be the official starting point > > for __builtin_bswap16(). > > > > Fixes: 7322dd755e7d ("byteswap: try to avoid __builtin_constant_p gcc bug") > > Reported-by: Stephen Rothwell > > Signed-off-by: Josh Poimboeuf > > --- > > include/linux/compiler-gcc.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > 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 */ > > -- > > 2.4.11 Tested-by: Stephen Rothwell Michael, do you want to pass the fix patch on, or will I submit it directly to Linus? -- Cheers, Stephen Rothwell