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Re: [PATCH] Fix optimization regression in constant folder

From: Eric Botcazou <ebotcazou at adacore dot com>
To: Ian Lance Taylor <iant at google dot com>
Cc: "Richard Guenther" <richard dot guenther at gmail dot com>, gcc-patches at gcc dot gnu dot org
Date: Mon, 1 Oct 2007 01:27:59 +0200
Subject: Re: [PATCH] Fix optimization regression in constant folder
References: <200709171539.26653.ebotcazou@adacore.com> <200709301801.39718.ebotcazou@adacore.com> <m3r6kf3gyx.fsf@localhost.localdomain>

> That doesn't make sense: a type either wraps on overflow or is
> undefined on overflow.

Well, I've given the rationale and I stand by it.  We already have the 
property that, if flag_strict_overflow is not set, signed types are neither 
TYPE_OVERFLOW_WRAPS nor TYPE_OVERFLOW_UNDEFINED.

> I think TYPE_IS_SIZETYPE should imply TYPE_OVERFLOW_UNDEFINED.

Agreed.  We already have this in Ada because size types are signed, but that's 
not sufficient, we need more to be able to reassociate.

> Richard's patch for PR 30364 should test TYPE_OVERFLOW_UNDEFINED, not
> TYPE_OVERFLOW_WRAPS.

Makes sense, but that won't change anything as far as Ada is concerned.

-- 
Eric Botcazou

References:
- [PATCH] Fix optimization regression in constant folder
  - From: Eric Botcazou
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Eric Botcazou
- Re: [PATCH] Fix optimization regression in constant folder
  - From: Ian Lance Taylor

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