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(g77-295.info)Use Submodel Options

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Use Submodel Options
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   Using an appropriate `-m' option to generate specific code for your
CPU may be worthwhile, though it may mean the executable won't run on
other versions of the CPU that don't support the same instruction set.
Note: Hardware Models and Configurations.  For
instance on an x86 system the compiler might have been built--as shown
by `g77 -v'--for the target `i386-pc-linux-gnu', i.e. an `i386' CPU.
In that case to generate code best optimized for a Pentium you could
use the option `-march=pentium'.

   For recent CPUs that don't have explicit support in the released
version of `gcc', it *might* still be possible to get improvements with
certain `-m' options.

   `-fomit-frame-pointer' can help performance on x86 systems and
others.  It will, however, inhibit debugging on the systems on which it
is not turned on anyway by `-O'.