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Re: [rtl] combine a vec_concat of 2 vec_selects from the same vector
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Marc Glisse <marc dot glisse at inria dot fr>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Sat, 16 Mar 2013 10:30:07 +0100
- Subject: Re: [rtl] combine a vec_concat of 2 vec_selects from the same vector
- References: <alpine.DEB.2.02.1209091258520.5537@stedding.saclay.inria.fr> <alpine.DEB.2.02.1209300954110.4012@stedding.saclay.inria.fr> <alpine.DEB.2.02.1303151622520.3890@laptop-mg.saclay.inria.fr>
> My current understanding of simplify-rtx is that we should only do "safe"
> optimizations in it (make sure we only create expressions that every
> target will recognize), and if I want more advanced optimizations, I
> should do them elsewhere (not sure where). So I should probably at least
> restrict this one to the case where the result and XEXP (trueop0, 0) have
> the same mode.
Yes, simplify-rtx should only canonicalize or simplify expressions. Merging 2
VEC_SELECTs into a single one seems to fall into the second category, but if
no target can take advantage of it, that's probably a bit questionable indeed.
--
Eric Botcazou