From: Eric Botcazou <ebotcazou@adacore.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [RFC] optimize x - y cmp 0 with undefined overflow
Date: Tue, 27 May 2014 10:00:00 -0000 [thread overview]
Message-ID: <2973073.WOSPpEhgk4@polaris> (raw)
In-Reply-To: <CAFiYyc07qb6BtaGerCoojJercTnO4=b184O7km-rge=CyBjq2g@mail.gmail.com>
> I'm asking to merge them (move them to fold_comparison).
OK, I'll repost a first patch doing only the fold-const.c massaging.
> Yeah, it would be nice to see some support. The most interesting cases
> will be symbolic-singleton +- CST where the offset shrinks a constant offset
> in a symbolic A +- CST (thus we don't get into any overflow issues). Thus
> handling
>
> [a + 1, a + 1] - [1, 1] -> [a, a]
>
> for example. We get the offsetted singleton symbolic ranges from
> conditional asserts a lot.
For the case at hand, you have [x + 1, INF] for y and you want to evaluate the
range of y - x, so you really don't want to use the range of x...
--
Eric Botcazou
next prev parent reply other threads:[~2014-05-27 10:00 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-26 10:24 Eric Botcazou
2014-05-26 12:55 ` Richard Biener
2014-05-27 9:26 ` Eric Botcazou
2014-05-27 9:42 ` Richard Biener
2014-05-27 10:00 ` Eric Botcazou [this message]
2014-05-27 10:12 ` Richard Biener
2014-05-30 8:49 ` Eric Botcazou
2014-06-02 10:36 ` Richard Biener
2014-06-02 10:37 ` Richard Biener
2014-06-03 8:13 ` Eric Botcazou
2014-06-03 11:00 ` Richard Biener
2014-06-06 10:54 ` Eric Botcazou
2014-06-06 15:45 ` Richard Biener
2014-06-20 9:40 ` Eric Botcazou
2014-06-24 10:34 ` Richard Biener
2014-09-29 23:01 ` Eric Botcazou
2014-05-27 16:14 ` Eric Botcazou
2014-05-27 16:19 ` Richard Biener
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