This directory contains all code for the mpn layer of GMP.

Most subdirectories contain machine-dependent code, written in assembly or
C.  The `generic' subdirectory contains default code, used when there is no
machine-dependent replacement for a particular machine.

There is one subdirectory for each architecture.  Note that e.g., 32-bit
sparc and 64-bit sparc cannot share any code, and are therefore considered
completely different architecture.

A particular machine will only use code from one such subdirectory, and the
`generic' subdirectory.  The architecture-specific subdirectory contains a
hierachy of directories for various architecture variants and
implementations; the top-most level contains code that runs correctly on all
variants.