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Message-ID: <33967a01-9ed0-43db-a615-907abab989b7@lunn.ch> Date: Mon, 13 Nov 2023 20:08:40 +0100 From: Andrew Lunn <andrew@...n.ch> To: Alexander Lobakin <aleksander.lobakin@...el.com> Cc: Yury Norov <yury.norov@...il.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, Alexander Potapenko <glider@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Przemek Kitszel <przemyslaw.kitszel@...el.com>, netdev@...r.kernel.org, linux-btrfs@...r.kernel.org, dm-devel@...hat.com, ntfs3@...ts.linux.dev, linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v3 04/11] linkmode: convert linkmode_{test,set,clear,mod}_bit() to macros On Mon, Nov 13, 2023 at 06:37:10PM +0100, Alexander Lobakin wrote: > Since commit b03fc1173c0c ("bitops: let optimize out non-atomic bitops > on compile-time constants"), the non-atomic bitops are macros which can > be expanded by the compilers into compile-time expressions, which will > result in better optimized object code. Unfortunately, turned out that > passing `volatile` to those macros discards any possibility of > optimization, as the compilers then don't even try to look whether > the passed bitmap is known at compilation time. In addition to that, > the mentioned linkmode helpers are marked with `inline`, not > `__always_inline`, meaning that it's not guaranteed some compiler won't > uninline them for no reason, which will also effectively prevent them > from being optimized (it's a well-known thing the compilers sometimes > uninline `2 + 2`). > Convert linkmode_*_bit() from inlines to macros. Their calling > convention are 1:1 with the corresponding bitops, so that it's not even > needed to enumerate and map the arguments, only the names. No changes in > vmlinux' object code (compiled by LLVM for x86_64) whatsoever, but that > doesn't necessarily means the change is meaningless. > > Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com> > Acked-by: Jakub Kicinski <kuba@...nel.org> > Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com> Reviewed-by: Andrew Lunn <andrew@...n.ch> Andrew
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