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Re: [PATCH] match.pd: reassociate multiplications with constants

From: Alexander Monakov <amonakov at ispras dot ru>
To: Marc Glisse <marc dot glisse at inria dot fr>
Cc: gcc-patches at gcc dot gnu dot org
Date: Thu, 13 Jul 2017 22:41:41 +0300 (MSK)
Subject: Re: [PATCH] match.pd: reassociate multiplications with constants
Authentication-results: sourceware.org; auth=none
References: <alpine.LNX.2.20.13.1707131911060.20069@monopod.intra.ispras.ru> <alpine.DEB.2.20.1707131956130.1999@stedding.saclay.inria.fr>

On Thu, 13 Jul 2017, Marc Glisse wrote:
> I notice that we do not turn (X*10)*10 into X*100 in GIMPLE.

Sorry, could you clarify what you mean here?  I think we certainly do that,
just not via match.pd, but in 'associate:' case of fold_binary_loc.

> Relying on inner expressions being folded can be slightly dangerous,
> especially for generic IIRC. It seems easy enough to check that @1 is neither
> 0 nor -1 for safety.

I wanted to add a gcc_checking_assert to that effect, but it's not used in
match.pd anywhere.  Is there a nice way to do that?

Thanks!
Alexander

Follow-Ups:
- Re: [PATCH] match.pd: reassociate multiplications with constants
  - From: Marc Glisse

References:
- [PATCH] match.pd: reassociate multiplications with constants
  - From: Alexander Monakov
- Re: [PATCH] match.pd: reassociate multiplications with constants
  - From: Marc Glisse

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