Messages in this thread | | | Date | Thu, 25 Feb 2021 13:18:01 -0700 | From | Nathan Chancellor <> | Subject | Re: [PATCH] linux/compiler-clang.h: define HAVE_BUILTIN_BSWAP* |
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On Thu, Feb 25, 2021 at 12:14:17PM -0800, Kees Cook wrote: > On Thu, Feb 25, 2021 at 12:06:37PM -0800, Andrew Morton wrote: > > On Thu, 25 Feb 2021 12:03:48 -0800 Kees Cook <keescook@chromium.org> wrote: > > > > > On Thu, Feb 25, 2021 at 05:45:09PM +0100, Arnd Bergmann wrote: > > > > From: Arnd Bergmann <arnd@arndb.de> > > > > > > > > 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@arndb.de> > > > > > > Cc: stable@vger.kernel.org > > > > I figured 4% better compile time isn't significant enough to justify a > > backport. Thoughts? > > It's a trivial change, so I think it's worth it?
Indeed. Any wins that we can get with compile time, we should take. Clang is being widely used in production systems now so I feel like with a trivial change plus user visible impact, it should be backported.
Not to mention that the generated code in theory should be better because it is the compiler's builtin, rather than a hand rolled one, AND this is technically a regression, given that it worked before compiler.h was split.
Cheers, Nathan
> > > > > Reviewed-by: Kees Cook <keescook@chromium.org> > > > > -- > Kees Cook
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