In-Reply-To: <[email protected]>
On Sun, 11 Jun 2006 23:05:59 +0200, Emmanuel Fleury wrote:
> > Looking at the generated code, it seems the compiler just makes dumb
> > choices and tends to recompute current_thread_info() in unlikely code
> > paths even when there is no register pressure. 4.0.2 makes better
> > choices.
>
> What size with gcc 4.1.2 ? (just curiosity)
The 3.3 vs 4.0 comparisons were with two different configs, so only
relative gain/loss with asm vs. C could be compared.
I downloaded gcc 4.1.1 and compared to 4.0.2 with the exact same config,
since I was curious how much better it might be overall.
gcc 4.0.2:
text data bss dec hex filename
3645212 555556 312024 4512792 44dc18 2.6.17-rc6-nb-C/vmlinux
3647276 555556 312024 4514856 44e428 2.6.17-rc6-nb-asm/vmlinux
-2064
gcc 4.1.1:
text data bss dec hex filename
3614686 520416 311672 4446774 43da36 2.6.17-rc6-nb-C/vmlinux
3616942 520416 311672 4449030 43e306 2.6.17-rc6-nb-asm/vmlinux
-2256
Kernel code starts out ~30K bytes smaller with gcc 4.1 and using C
for current_thread_info() helps even more than with 4.0. Nice...
Maybe a patch that enables C code for gcc 4.0+ would work, since
on 3.3 the asm code is better?
--
Chuck
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