Hi all,
On Mon, 9 May 2016 10:59:27 +1000 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
>
> On Fri, 6 May 2016 09:22:25 -0500 Josh Poimboeuf <jpoimboe@xxxxxxxxxx> 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@xxxxxxxxxx>
> > 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@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxxxx>
Michael, do you want to pass the fix patch on, or will I submit it
directly to Linus?
--
Cheers,
Stephen Rothwell
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