Re: [BENCHMARK] gcc3.2 v 2.95.3 (contest and linux-2.5.38)

Mark Veltzer
2002-09-23T10:49:29Z

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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
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