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Re: c/7344: performance regression on huge case statements
- From: Nathanael Nerode <neroden at twcny dot rr dot com>
- To: gcc-gnats at gcc dot gnu dot org, rschiele at uni-mannheim dot de, gcc-bugs at gcc dot gnu dot org, nobody at gcc dot gnu dot org
- Date: Thu, 10 Oct 2002 21:57:12 -0400
- Subject: Re: c/7344: performance regression on huge case statements
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7344
To clarify what I meant:
>The call to note_prediction_to_br_prob was added to
rest_of_compilation >in toplev.c with the change from revision 1.620 to
1.621 of toplev.c.
>Sure enough, everything is fine with the May 7th CVS.
In the May 9th CVS,
>CC1 spends a large amount of time cycling through basic blocks, but it
>doesn't hang yet. I haven't pinned down the patch which causes it to
>hang.
So there's a slowdown when the call is introduced, but it isn't enough
to cause the infinite execution time. A subsequent change between May
9th and July 17th must have done that, and I haven't pinned down what
change that is.