Re: init_reg_autoinc bug and how to describe regs that can't autoincdec

[Hans-Peter Nilsson <hans-peter dot nilsson at axis dot com>]

> From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
> Date: Thu, 22 Nov 2007 09:09:38 EST

  hp wrote:
> > I mean, by naming, by the head comment and at a glance it seems
> > it's generally intended to guide register allocation regarding
> > autoincdec, but can currently only help in an obscure case which
> > you say probably even isn't useful anymore.  Why not improve it?
> 
> Because that's not what it means.  The most relevant comment is in regclass.c:
> 
> /* If we have auto-increment or auto-decrement and we can have secondary
>    reloads, we are not allowed to use classes requiring secondary
>    reloads for pseudos auto-incremented since reload can't handle it.  */
> 
> "not allowed" means literally that: we can't *allow* the pseudo to end up
> in such a reg class.  Here, we can allow it, but we prefer that we not
> do that.  That needs another mechanism since regclass.c currently doesn't
> distinguish between those cases.

I see.  Some comments are slightly misleading then.  I guess I
should send a patch to make it clear that this is not about
what's possible for the target to handle but what's possible for
gcc to handle.

> Here's a completely untested (not even compiled) patch that suggests a
> mechanism that I'd recommend:
> ...

Thank you!

I'll rework this as a target hook function (target hooks are in,
pure target macros are out) and post for stage 1.

(Now back to that reload problem...)

brgds, H-P