more m68k breakage on m68k-linux
Bernardo Innocenti
bernie@develer.com
Tue Mar 2 00:18:00 GMT 2004
Richard Zidlicky wrote:
> Note the typo "FIRST_PSEOUDO_REGISTER".. made it somewhat hard to
> find the change.
Oops! That's very unfortunate. I've fixed it in the ChangeLog.
> This looks highly bogus to me: You create a new "hard" register but
> dont init it anywhere (FIXED_REGISTERS,...). You change ARG_POINTER_REGNUM
> from 14 to 24 claiming in the comment that it is not a hard register..
> well it is still < FIRST_PSEOUDO_REGISTER so it is a hard register.
All registers >= FIRST_PSEUDO_REGISTER are free for use in
RTL expressions as temporaries before the register allocator
pass moves them to a hard register.
If I didn't increment FIRST_PSEUDO_REGISTER, register 25 would
be used both as the argptr and as a placeholder for some
temporary register, with very interesting consequences :-)
> Last not least there is
>
> #define ELIMINABLE_REGS \
> {{ ARG_POINTER_REGNUM, STACK_POINTER_REGNUM }, \
> { ARG_POINTER_REGNUM, FRAME_POINTER_REGNUM }, \
> { FRAME_POINTER_REGNUM, STACK_POINTER_REGNUM }}
>
> and it is not clear to me how this should work if ARG_POINTER_REGNUM
> were a pseudo register.
This basically says that the arg pointer can be eliminated
against either SP or FP. Additionally, FP can be
eliminated with SP.
--
// Bernardo Innocenti - Develer S.r.l., R&D dept.
\X/ http://www.develer.com/
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