Messages in this thread | ![/](/images/icornerl.gif) | | From | Geert Uytterhoeven <> | Date | Tue, 2 Jan 2024 11:49:03 +0100 | Subject | Re: [PATCH v3 2/5] m68k/bitops: use __builtin_{clz,ctzl,ffs} to evaluate constant expressions |
| |
On Sun, Dec 17, 2023 at 8:13 AM Vincent Mailhol <mailhol.vincent@wanadoo.fr> wrote: > > The compiler is not able to do constant folding on "asm volatile" code. > > Evaluate whether or not the function argument is a constant expression > and if this is the case, return an equivalent builtin expression. > > On an allyesconfig, with GCC 13.2.1, it saves roughly 8 KB. > > $ size --format=GNU vmlinux.before vmlinux.after > text data bss total filename > 60446534 70972412 2289596 133708542 vmlinux.before > 60429746 70978876 2291676 133700298 vmlinux.after
Still a win with gcc 9.5.0-1ubuntu1~22.04:
allyesconfig:
text data bss total filename 58882250 72419706 2284004 133585960 vmlinux-v6.7-rc8-1-m68k-bitops-force-inlining 58863570 72419546 2285860 133568976 vmlinux-v6.7-rc8-2-m68k-bitops-use-__builtin_clz,ctzl,ffs
So an even bigger win...
atari_defconfig:
text data bss total filename 4117008 1579350 151680 5848038 vmlinux-v6.7-rc8-1-m68k-bitops-force-inlining 4116940 1579534 151712 5848186 vmlinux-v6.7-rc8-2-m68k-bitops-use-__builtin_clz,ctzl,ffs
... but a small size increase here.
> > Reference: commit fdb6649ab7c1 ("x86/asm/bitops: Use __builtin_ctzl() > to evaluate constant expressions")
Please don't split lines containing tags.
> Link: https://git.kernel.org/torvalds/c/fdb6649ab7c1 > > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
| ![\](/images/icornerr.gif) |