Re: [PATCH] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP*

[Nick Desaulniers]

On Thu, Feb 25, 2021 at 12:06 PM Andrew Morton
<akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, 25 Feb 2021 12:03:48 -0800 Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> > On Thu, Feb 25, 2021 at 05:45:09PM +0100, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@xxxxxxxx>
> > >
> > > Separating compiler-clang.h from compiler-gcc.h inadventently dropped the
> > > definitions of the three HAVE_BUILTIN_BSWAP macros, which requires falling
> > > back to the open-coded version and hoping that the compiler detects it.
> > >
> > > Since all versions of clang support the __builtin_bswap interfaces,
> > > add back the flags and have the headers pick these up automatically.
> > >
> > > This results in a 4% improvement of compilation speed for arm defconfig.
> > >
> > > Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
> > > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > Cc: stable@xxxxxxxxxxxxxxx
>
> I figured 4% better compile time isn't significant enough to justify a
> backport.  Thoughts?

If I made a mistake in 815f0ddb346c, then it would be important to
correct it since 815f0ddb346c has existed for a few stable branches
(first landed in v4.19-rc1).
Acked-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

>
> > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
>


-- 
Thanks,
~Nick Desaulniers