Re: [PATCH] Use RTX_AUTOINC in rs6000 predicates.md

[Richard Sandiford <rdsandiford at googlemail dot com>]

> During the discussions about the rs6000 non-autoinc constraint
> question, Richard Henderson mentioned the ia64 constraint. ?The rs6000
> predicate should be simplified similarly. ?Is this reasonable?

Looks good to me FWIW.

Like you said in your reply in the autoinc thread, this predicate could
be used with a new ia64-like constraint that asm writers can use.  OTOH,
it might make sense for the new constraint to use the same condition as
the ia64 one, thus skipping the memory_operand check.  We know that
reload will make every MEM legitimate, so for exclusive checks like this,
'(match_test "mem")' seems better than '(match_operand "memory_operand")'.
(I was just about to start on a patch for that.)

I think this is probably just telling you back what you already said,
but the predicate's current name seems misleading; it accepts reg+reg
addresses whereas "o" doesn't.  So as things stand, the FP conversion
patterns could in principle accept a non-offsettable memref that needs
to be reloaded into an offsettable one.  (And the insns really do need
offsettable addresses.)

So I was wondering about adding the new constraint with:

  (and (match_code "mem")
       (match_test "GET_RTX_CLASS (GET_CODE (XEXP (op, 0))) != RTX_AUTOINC")))

and rewriting offsettable_mem_operand to use offsettable_memref_p.

OTOH, I could be talking rubbish. ;)

Richard