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Re: loop opts, mark 11


>  Basically, I am interested in samples that generate
>  different results with and without -fno-rerun-loop-opt.
>  (Note that I don't disable it by default anymore.)

[ On m68k-next-nextstep3 ]

OK, I managed to build a egcs-980602 CVS snapshot with (and  
without) your mark 11 patch.  c-torture-1.45 found no regression for  
the compiler with your patch.

Some preliminary figures:

% /usr/snp/bin/g77 -O2 bs3dvw.f
% time ./a.out
[ ... ]
84.8u 0.8s 2:27 58% 0+0k 0+0io 0pf+0w
% /usr/snp/bin/g77 -O2 -fforce-addr bs3dvw.f
% time ./a.out
[ ... ]
82.1u 0.7s 2:33 54% 0+0k 0+0io 0pf+0w
% /usr/snp/bin/g77 -O2 -fno-rerun-loop-opt -fforce-addr bs3dvw.f
% time ./a.out
[ ... ]
85.9u 1.5s 1:50 79% 0+0k 0+0io 0pf+0w
% /usr/snp/bin/g77 -O2 -fno-rerun-loop-opt bs3dvw.f
% time ./a.out
[ ... ]
85.3u 1.0s 1:34 91% 0+0k 0+0io 0pf+0w

So, for this piece of code (that has a lot of opportunities for giv  
combining), rerunning loop optimisation helps (as does  
-fforce-addr, but that's usual for Fortran code on m68k).  It's also  
1.5 seconds faster than the mark 10 attempt.

The NWP code is still running; no timings yet.

HTH,
Toon.


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