Re: GCC 4..4.x speed regression - help?

[Martin Guy <martinwguy at gmail dot com>]

Yes, GCC is bigger and slower and for several architectures generates
bigger, slower code with every release, though saying so won't make
you very popular on this list! :)

One theory is that there are now so many different optimization passes
(and, worse, clever case-specific hacks hidden in the backends) that
the interaction between the lot of them is now chaotic. Selecting
optimization flags by hand is no longer humanly possible.

There is a project to untangle the mess: Grigori Fursin's MILEPOST GCC
at http://ctuning.org/wiki/index.php/CTools:MilepostGCC - an AI-based
attempt to autmatically select combinations of GCC optimization flags
according to their measured effectiveness and a profile of you source
code's characteristics. The idea is fairly repulsive but effective -
it reports major speed gains of the order of twice as fast compared to
the standard "fastest" -O options, and there is  Google Summer of Code
2009 project based on this work.

It seems to me that much over-hacked software lives a life cycle much
like the human one: infancy, adolescence, adulthood, middle-age (spot
the spread!) and ultimately old age and senility, exhibiting
characteristics at each stage akin to the mental faculties of a
person.

If you're serious about speed, you could try MILEPOST GCC, or try the
current up-and-coming "adolescent" open source compiler, LLVM at
llvm.org

    M