When you configure GCC using the
configure script, it will
construct the file
Makefile from the template file
Makefile.in. When it does this, it can incorporate makefile
fragments from the
config directory. These are used to set
Makefile parameters that are not amenable to being calculated by
autoconf. The list of fragments to incorporate is set by
config.gcc; See System Config.
Fragments are named either
depending on whether they are relevant to configuring GCC to produce
code for a particular target, or to configuring GCC to run on a
particular host. Here target and host are mnemonics
which usually have some relationship to the canonical system name, but
no formal connection.
If these files do not exist, it means nothing needs to be added for a
given target or host. Most targets need a few
fragments, but needing
fragments is rare.