propagate_freq enormous performance hit in 3.1

[Brad Lucier]

Jan:

>From examining the sources, it seems that predict.c is your baby,
and it seems to have a serious performance problem in propagate_freq
for large flow graphs, see

http://gcc.gnu.org/ml/gcc-prs/2001-08/msg00184.html

Do you have any idea of what's going on here?

BTW, I apologize for the large, useless inclusion in that GNAT PR.  The real
source code I tested it on is at

http://www.math.purdue.edu/~lucier/all.i.gz

Brad Lucier