From: Michael Ellerman <mpe@ellerman•id.au>
To: Stephen Rothwell <sfr@canb•auug.org.au>,
Josh Poimboeuf <jpoimboe@redhat•com>
Cc: Andrew Morton <akpm@linux-foundation•org>,
linux-next@vger•kernel.org, linux-kernel@vger•kernel.org,
Arnd Bergmann <arnd@arndb•de>,
Linus Torvalds <torvalds@linux-foundation•org>
Subject: Re: [PATCH] compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16()
Date: Mon, 09 May 2016 19:34:53 +1000 [thread overview]
Message-ID: <1462786493.5531.1.camel@ellerman.id.au> (raw)
In-Reply-To: <20160509163302.59f3f6a2@canb.auug.org.au>
On Mon, 2016-05-09 at 16:33 +1000, Stephen Rothwell wrote:
> On Mon, 9 May 2016 10:59:27 +1000 Stephen Rothwell <sfr@canb•auug.org.au> wrote:
> > On Fri, 6 May 2016 09:22:25 -0500 Josh Poimboeuf <jpoimboe@redhat•com> 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 <jpoimboe@redhat•com>
> > > 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 <sfr@canb•auug.org.au>
> > > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat•com>
> > > ---
> > > 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 <sfr@canb•auug.org.au>
>
> 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.
cheers
next prev parent reply other threads:[~2016-05-09 9:35 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-06 4:58 linux-next: build failure after merge of the akpm-current tree Stephen Rothwell
2016-05-06 5:44 ` Andrew Morton
2016-05-06 6:09 ` Stephen Rothwell
2016-05-06 6:55 ` Michael Ellerman
2016-05-06 14:22 ` [PATCH] compiler-gcc: require gcc 4.8 for powerpc __builtin_bswap16() Josh Poimboeuf
2016-05-09 0:59 ` Stephen Rothwell
2016-05-09 5:39 ` Sedat Dilek
2016-05-09 8:31 ` Stephen Rothwell
2016-05-09 6:33 ` Stephen Rothwell
2016-05-09 9:34 ` Michael Ellerman [this message]
2016-05-09 10:16 ` Arnd Bergmann
2016-05-09 10:36 ` Stephen Rothwell
2016-06-15 9:33 ` linux-next: build failure after merge of the akpm-current tree Paul Bolle
2016-06-15 14:03 ` Josh Poimboeuf
2016-06-15 21:12 ` Paul Bolle
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