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RFC ping: Make regname use validate_change
- From: Andreas Krebbel <krebbel1 at de dot ibm dot com>
- To: gcc-patches at gcc dot gnu dot org
- Cc: bernds_cb1 at t-online dot de
- Date: Mon, 5 Sep 2005 15:11:03 +0200
- Subject: RFC ping: Make regname use validate_change
Hello,
in http://gcc.gnu.org/ml/gcc-patches/2005-08/msg01489.html
I've described a problem where regrename renamed a general
register creating an insn which does not satisfy the insn
predicate anymore. The patch using validate_change for replacing
the registers has already been discussed with Bernd Schmidt. I understand
his concerns that rerecognizing every insn would make
that step more expensive and regrename already spends some
effort not to invalidate an insn. But I'm still not convinced
that this behaviour is correct. The checks done in an insn
predicate can be rather complex and are not limited to a single
SET if you consider a match_parallel. So just drawing the
constraints into account when replacing a register may not be
enough.
As a compromise I've suggested to just call the insn predicate.
Although I wouldn't be that happy with that solution because
I doubt that it goes far enough I would like to hear what you
folks think about that.
Thanks
-Andreas-