proper way to include gcc/config/<arch>/<arch>.h ?

[Richard Kenner]

    What is the proper way to include gcc/config/<arch>/<arch>.h?

    `tm_file' is set early in `config.gcc' as
    "tm_file=${cpu_type}/${cpu_type}.h", however some config triplets add to
    `tm_file' by "tm_file="${tm_file} foo.h", while others totally
    overwrite it with tm_file="foo.h <arch>/<arch>.h bar.h".  Others do all
    kinds of things -- "*-*-gnu*" is a good example of this.

    I am finding it impossible to find a clean multi-platform example to
    follow.

It depends on the structure of the port's files.  Some <arch>.h files expect
things to be defined before they are included and use those to select various
options.  Those ports will use the second method.

Others will define default definitions for macros and expect other files to
override them.  Those use the first method.  This is what I think is the
cleanest.

And some have some files that work both ways, though that's a real mess.