[gfortran] patch for pr 21130 - 38822 lines of Fortran 90 takes more than 10 minutes to compile on a dual 3GHz P4 Linux box with lots of RAM

[Paul Thomas]

Bud,

A last PS on this!

My Athlon1700 takes 25 minutes 47 seconds to compile the testcase, whout 
the patch. With the patch, it takes 2 minutes 46 seconds.  ifort, on the 
other hand, takes 12 seconds to do the same job.

We still have some work to do, in spite of the very remarkable 
improvement that you have made.  I believe that module reading has to be 
broken up into two stages: (i) To read the module file and create a 
namespace with all the symbols on it; and (ii) To read the symbols from 
that namespace, according to the requirements of the USE statement, and 
to populate the current namespace with them.  That way, the file IO and 
the processing is only done once for each module and each compilation.

Paul