[PING^3] INSN attribute to enable/disable alternatives

["Andreas Krebbel" <Andreas.Krebbel@de.ibm.com>]

Hi,

these 3 patches introduce a new special attribute to be used in INSN
definitions in order to enable or disable certain INSN alternatives.
I think this comes in quite handy when enhancing a back end with new
instructions.  I've posted these patches in stage 2 and really need
them to go in since I've a few back end patches relying on that
feature.

Ian already had a look.  Although the feature was considered
reasonable I can understand that he was unhappy with the genattr
changes in patch 3 introducing new attribute 'getter' functions with
an additional 'alternative' parameter.  These changes are the part
which unfortunately make the introduction of that simple feature look
rather complicated.

I would be happy to rework that part of the patch if someone comes up
with a better/simpler solution.  Any suggestions?!

Here is the mail from Ian:
http://gcc.gnu.org/ml/gcc/2007-09/msg00458.html


[PATCH 1/3] S/390: New `enabled' insn attribute
http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01908.html

[PATCH 2/3] reload,recog: New `enabled' insn attribute
http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01909.html

[PATCH 3/3] genattr: New `enabled' insn attribute
http://gcc.gnu.org/ml/gcc-patches/2007-08/msg01910.html

Bye,

-Andreas-