i686 double alignment vs performance

[tprince@cat.e-mail.com]

I got the following geometric mean Mflops from Livermore
Kernels lfk537e.f (double precision), with my modifications.  Both
g77 and egcs are compiled with binutils-2.9.1 installed, with
-O2 -malign-double -march=pentiumpro -funroll-lloops so that I
believe the loop code alignments are reasonable and
comparable.

Compiler       PPro/200      P II/233

g77-0.5.23     14.8              50
egcs-0628     35.8              50
lf90-4.50d       42.5              55

So, the additional alignments currently generated in egcs must
give it a tremendous advantage on the pentiumpro, but the
pentium2 isn't so dependent on them.  If I compare egcs and
g77 without -funroll-loops, however, egcs often has an
advantage even on P II.  If I turn off -malign-double, performance
drops significantly in every case, but more so with egcs on PPro.

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