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Re: [PATCH] Fix force_to_mode not to modify in place the passed rtl (PR rtl-optimization/58726)
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Jakub Jelinek <jakub at redhat dot com>, Richard Biener <rguenther at suse dot de>, Steven Bosscher <stevenb dot gcc at gmail dot com>
- Date: Wed, 04 Dec 2013 11:23:27 +0100
- Subject: Re: [PATCH] Fix force_to_mode not to modify in place the passed rtl (PR rtl-optimization/58726)
- Authentication-results: sourceware.org; auth=none
- References: <20131203224654 dot GH892 at tucnak dot redhat dot com> <529EB307 dot 1080208 at redhat dot com>
> I'd worry there's other latent bugs of this nature and if we'd be better
> off avoiding the temporary sharing. We have structure sharing rules for
> a reason -- I'd hate to think of all the code that would need auditing
> to ensure it was safe with this bogus sharing.
I wouldn't throw the baby with the bath's water here, it's one of the numerous
PRs opened by Zhendong Su and which clearly look machine-generated. It fails
with 4.4.x onwards and apparently nobody noticed the problem in real life.
We know that we have latent sharing issues in the combiner because of the way
it's designed, but they are quite rare in practice.
--
Eric Botcazou