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Re: RFC: additions to the machine-definition language


On May  7, 2001, Dan Nicolaescu <dann@godzilla.ICS.UCI.EDU> wrote:

> The implemented features are: 

> (define-register "REGNAME")
> (define-register-class (REGISTER_LIST))
> (define-pic-offset-table-reg "REGNAME")
> (define-arg-pointer-reg "REGNAME")
> (define-frame-pointer-reg "REGNAME")
> (define-fixed-registers "REGNAME")
> (define-call-used-registers "REGNAME")
> (define-reg-alloc-order REGISTER_LIST OR REG_CLASS_LIST)
> (define-leaf-reg-alloc-order REGISTER_LIST OR REG_CLASS_LIST)

Most of these can already be defined with define_constants, but you
don't always want to do it.  Think, for example, of a multi-ISA
back-end that uses a different frame-pointer register for each ISA.
You'd have to express a conditional in the define.  Not that this is
too hard to do, but it's probably more cumbersome, and negates part of
the benefit of moving the definitions to the md file.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me


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