Re: GCC 4.2.0 Status Report (2007-02-19)

["Kaveh R. GHAZI" <ghazi at caip dot rutgers dot edu>]

On Tue, 20 Feb 2007, Andi Kleen wrote:

> "Kaveh R. GHAZI" <ghazi@caip.rutgers.edu> writes:
> >
> > And we don't want to arm our detractors with bad SPEC numbers.  I can just
> > imagine the FUD spreading... we've got to fix it or backout.
>
> For me as a gcc user miscompilations are far worse than bad SPEC numbers.
> I never run SPEC, but if my programs are miscompiled I am in deep trouble.
> I expect many other people to feel similar. Broken programs are infinitely
> worse than slower programs.
>
> If you really have any detractors(?) they will get much more meat out
> of miscompilations than out of any SPEC numbers.
>
> I find it amazing that this needs stating.
> -Andi

No it doesn't need stating, at least not for me. :-)  Sure nobody likes
bugs/miscompilations, but all compilers have them.  We evaluate how
serious they are and whether a performance hit from a bug fix is worth it.
My understanding is that 4.1 has this very same bug, and it hits about as
often as it does in 4.2.  See the end of this message:
http://gcc.gnu.org/ml/gcc/2007-02/msg00432.html

If so, then it can't be too bad IMHO.  That was the context within which
I made my statement.  And if that holds, I continue to stand by it.

Clearly the best option is to fix the bug properly and retain the
performance.  The estimate in the above link ranges from two weeks to two
months of work, if we can find a volunteer.  I'm in favor of trying that
if someone steps forward.  "Plan B" IMHO should be to back out the
slowdown bugfix.

		--Kaveh
--
Kaveh R. Ghazi			ghazi@caip.rutgers.edu