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Re: [PATCH v2, middle-end]: Introduce TARGET_REJECT_COMBINED_INSN target hook
On Sat, 25 Aug 2012, Uros Bizjak wrote:
> Hello!
>
> v2 patch differences:
> - moves hook description text to target.def
> - fixes error path to clear clobbers, as expected by recog_for_combine callers
>
> 2012-08-25 Uros Bizjak <ubizjak@gmail.com>
>
> * target.def (reject_combined_insn): New target hook.
> * doc/tm.texi.in (TARGET_REJECT_COMBINED_INSN): New hook.
> * doc/tm.texi: Regenerated.
> * combine.c (recog_for_combine): Call targetm.reject_combined_insn
> to allow targets to reject combined insn.
Maybe mention that the default is to allow all combinations for
which a pattern match? And that the reason to disallow them can
be that they're known to result in suboptimal code? Or other
reasons.
I don't think it should be mentioned that it can be used to stop
invalid code to be generated; that'd just be encouraging
covering up bugs in reload. (Using it to simplify the port may
be valid.)
brgds, H-P