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Re: [PATCH] diagnose unsupported uses of hardware register variables (PR 88000)
Hi,
On Fri, 16 Nov 2018, Segher Boessenkool wrote:
> > I.e. like volatile they can arbitrarily change their value. I don't
> > know if other peoples mind model is similar, but it certainly is the
> > model that is implemented in the GIMPLE pipeline (and if memory serves
> > well of the RTL pipeline as well).
> >
> > Copying outof/into pseudos around asms serves no purpose with that
> > model, it rather makes regvars somewhat "safer" to use, without
> > actually making them safer (there _is_ nothing safe about them).
>
> The only supported case is for inputs and outputs to extended asm.
> Maybe we should just come up with a syntax so you can specify hard regs
> for that directly (without needing a separate regclass for every reg).
I would like that, yes. (Of course backward compat would have us support
the historic usage for some time, but still ...)
Ciao,
Michael.