Re: C++ compile-time regressions

[Gerald Pfeifer <pfeifer at dbai dot tuwien dot ac dot at>]

On Thu, 2 Aug 2001, Mark Mitchell wrote:
> I think we're tackling this from the wrong angle.  GCC uses about
> 3 to 4 times as much memory as it needs to, really, and our garbage
> collector touches too many pages.

Well, I think we need to tackle it from several angles. :-)   Right now,
both compile-time and run-time performance are worse than GCC 2.95 (even
if we tune for either one).

> I know how to fix these problems, I think, and I expect to start
> working on them soonish.

That's excellent news, thanks!

> Anyhow, I guess I think we've done enough for now.

Daniel seems to have a promising patch, (a first draft of) which seems
very non-invasive and simple; this might be an excellent candidate for
GCC 3.0.2.

On Thu, 2 Aug 2001, Daniel Berlin wrote:
> BTW, i've gotten the performance problem down using a slightly
> modified heuristic from integrate.c. On the last run, the compile
> times were about the same as 200 insns, but the performance was *much*
> better (we're down to about 10% speed loss).

Excellent.

> When your performance gets shot to hell, it's always being caused by
> not inlining things. I.E. at 100 insns, *::begin and *::end are taking
> >50% of the runtime, because they aren't being inlined.

I guessed that something extremely bad like this was going on, because
performance was getting *that* bad.

Good to see both issues (compile-time and run-time performance) being
addressed. :-)

Gerald
-- 
Gerald "Jerry" pfeifer@dbai.tuwien.ac.at http://www.dbai.tuwien.ac.at/~pfeifer/