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Re: [PATCH 2/9] S/390: Add disabled insn attribute
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: krebbel at linux dot vnet dot ibm dot com (Andreas Krebbel)
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 1 Feb 2016 18:22:18 +0100 (CET)
- Subject: Re: [PATCH 2/9] S/390: Add disabled insn attribute
- Authentication-results: sourceware.org; auth=none
Andreas Krebbel wrote:
> On 02/01/2016 02:45 PM, Ulrich Weigand wrote:
> > So I'm wondering what the difference is between this and simply
> > overriding the default implementation of "enabled" per-insn?
> >
> > So instead of adding
> > (set_attr "disabled" "0,1")])
> > to an insn, you might simply add instead:
> > (set_attr "enabled" "*,0")])
> Not sure but wouldn't this mean that the value of the enabled attribute would then depend on the
> order of the set_attr for "enabled" and "cpu_facility" since one is defined on the value of the other?!
I don't think the order matches; genattrtab seems to first read in all .md
files and only then optimize and then emit definitions of all the get_attr_...
functions. The eq_attr uses in the "enabled" definition would only be
evaluated at that point.
Bye,
Ulrich
--
Dr. Ulrich Weigand
GNU/Linux compilers and toolchain
Ulrich.Weigand@de.ibm.com