Messages in this thread | | | Date | Mon, 23 Sep 2002 09:56:29 -0400 | From | Daniel Jacobowitz <> | Subject | Re: [BENCHMARK] gcc3.2 v 2.95.3 (contest and linux-2.5.38) |
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On Mon, Sep 23, 2002 at 02:06:01PM +0300, Mark Veltzer wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On Monday 23 September 2002 06:16, Con Kolivas wrote: > > > > > > > Ugh?? Something is _seriously_ messed up here. > > > > The most important question to ask here is: What flags did you compile both > ?!? I wouldn't count on the flags that were designed for gcc 2.95 to be any > good for 3.2... Could the original poster comment on this ? > > Any GCC maintainers on this list to comment ? Is there any set of flags to be > passed to gcc 3.2 to replicate 2.95 behaviour ? I wouldn't rule out gcc 3.2 > having a totaly different set of optimizations geared towards user space C++. > Again, any gcc maintainers comments ?!? > > Since most of the code in gcc is for C++ most of the changes in gcc should > have been geared towards C++ (yes - quite a monstrous language). It seems to > me that the changes in C compilation between 2.95 and 3.2 should be minor > EXCEPT in terms of C optimization. Can anyone with assembly knowledge take > apart two identical drivers and see the better machine code produced by 2.95 > as compared to 3.2 ? If so - can this be reported to the gcc folk ? > > It seems to me that the difference is so huge that even user space > applications could show the difference. I suggest compiling a large C program > (emphasis on the C) in user space and doing the comparison... I would guess > that this should have been done by the gcc folk but because of the > hideousness of the C++ language I would guess that they mostly concentrated > on C++ and didn't bother to benchmark regular C optimization. This is quite > awful as the bulk of lower level open source code is in C and not C++ so this > kind of test has a lot of meaning for any distribution that is going to be > based on gcc 3.2... > > If this benchmark turns out to be right then it seems to me that the only > conclusion is that the gcc folk let their interest in aesoteric features of > C++ (which has about 1/2 a billion of those) override the basic need for > strong C optimization. Yes - it now seems that the C++ language (which is > quite an abomination in terms of engineering and the KISS principle) is > actually hurting open source (which has been my conclusion for quite some > time).
Mark, if you followed the GCC development process you'd realize that all of your above ranting about C++ is completely unfounded. Most people doing performance work - and there are a good number of them - focus on language-independent optimizations and check them primarily in C.
And I've no idea what you mean by "EXCEPT in terms of C optimization". First of all you're completely wrong - 3.2 supports most of C99, which is substantial - and secondly, of course the bulk of changes in support for a language are optimization. And those are substantial too.
-- Daniel Jacobowitz MontaVista Software Debian GNU/Linux Developer - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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