On 06/06/2016 01:40 PM, Jakub Jelinek wrote:
On Mon, Jun 06, 2016 at 09:27:56PM +0200, Marc Glisse wrote:
The last one would miss floating point registers (no 2 platforms use the
same letter for those, hence my quest for something more generic).
The goal of the experiment is described in PR59159 (for which "+X" is
unlikely to be the right answer, in particular because it is meaningless for
constants). I don't know in what context people use the "X" constraint, or
even better "=X"...
X constraint has been added mainly for uses in match_scratch like:
(clobber (match_scratch:SI 2 "=X,X,X,&r"))
or when the predicate takes care of everything and it is not needed to
specify anything further:
[(set (match_operand:SWI12 0 "push_operand" "=X")
(match_operand:SWI12 1 "nonmemory_no_elim_operand" "rn"))]
Using it in inline asm generally has resulted in lots of issues, including
ICEs etc., so nothing I'd recommend to use.
So would it make sense to define it as not available for use in ASMs? I
realize that's potentially a user-visible change, but it might be a
reasonable one to make.
jeff
