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You could just enable -O2 and the following: -frename-registers and -fweb. -O3 is simply -O2 plus those 3 options. |
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On Wed, 21 Jul 2004 20:50:01 -0400 |
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Adam Petaccia <adam@×××××××××.com> wrote: |
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> With gcc, is there a way to enable all -O3 options but function |
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> inlines? Would -fno-inline work or something like that? |
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> |
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> Mario Domenech Goulart wrote: |
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> |
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> >Hello, |
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> > |
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> >There's an interesting discussion in the OpenBSD mailing |
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> >list about the use of inline. |
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> > |
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> >Here's the beginning of the thread about this topic: |
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> > |
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> >,----[ http://www.sigmasoft.com/cgi-bin/wilma_hiliter/openbsd-tech/200407/msg00175.html ] |
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> >| inline considered harmful. |
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> >| |
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> >| * To: tech@×××××××.org |
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> >| * Subject: inline considered harmful. |
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> >| * From: Artur Grabowski <art@××××××××.org> |
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> >| * Date: 21 Jul 2004 03:54:46 +0200 |
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> >| * User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 |
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> >| |
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> >| Today we did a bunch of removal of inline functions in the kernel. |
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> >| It all started to make floppies fit, but now it's a quest. |
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> >| |
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> >| If you think that I'm crazy doing this because it might hurt your |
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> >| precious performance, go back to your vax and leave the performance |
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> >| tuning to people who have a cache. |
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> >| |
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> >| Every single inline we removed today (and there are more in the |
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> >| pipeline and even more waiting to be fixed) shrunk the code and MADE |
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> >| IT FASTER. Yes, modern cpus have something called "cache". The cache |
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> >| prefers the code to be smaller, rather than free from function calls. |
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> >| Yes, some cpus have expensive function call overhead. Don't use them. |
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> >| i386 has quite expensive function calls, on the other hand it doesn't |
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> >| have any relevant amount of registers either. So a function call |
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> >| instead of the same function inlined can potentially make the job |
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> >| easier for the register allocator in the compiler which could eat the |
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> >| overhead. At the same time the instruction cache can run the same code |
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> >| in the same place, instead of loading it from main memory 4711 times. |
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> >| And guess what? The stack on i386 is in the cache too, so the function |
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> >| call overhead isn't that bad anyway. |
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> >| |
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> >| I'm tired of seeing code where everything is made inline just because |
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> >| someone acted on a meme that hasn't been true for over a decade. Bloat, |
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> >| bloat and more bloat. Since people can't use inline correctly (it does |
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> >| have valid and correct uses), from now on inline in the OpenBSD kernel |
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> >| is considered to be a bug until proven otherwise. So. Next time I see |
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> >| code that adds to the bloat with inlines, I expect performance figures |
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> >| and kernel size comparisons that show that the inline actually |
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> >| contributes anything. Otherwise the code does not go in. |
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> >| |
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> >| There's still a lot of work to be done in the kernel (yes, macros can |
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> >| be evil too, just see nfs), so send diffs. And there's a whole |
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> >| unexplored field in userland too. |
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> >| |
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> >| //art |
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> >`---- |
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> > |
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> >Mario |
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> > |
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> > |
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> >-- |
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> >gentoo-performance@g.o mailing list |
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> > |
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> > |
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> > |
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> > |
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> |
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> -- |
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> gentoo-performance@g.o mailing list |
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> |
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