From: Goswin von Brederlow <goswin-v-b@web.de>
To: "Richard W.M. Jones" <rich@annexia.org>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Zarith problems on ppc64le
Date: Tue, 8 Nov 2016 11:00:29 +0100 [thread overview]
Message-ID: <20161108100029.GB18517@frosties> (raw)
In-Reply-To: <20161107154843.GH27249@annexia.org>
On Mon, Nov 07, 2016 at 03:48:43PM +0000, Richard W.M. Jones wrote:
> On Mon, Nov 07, 2016 at 01:22:01PM +0000, Richard W.M. Jones wrote:
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=1392247
> >
> > Zarith fails tests on OCaml 4.04.0 + ppc64le with some fairly gross
> > errors, eg:
> >
> > of_float -1.
> > - = -1
> > + = 0
> >
> > (It passes fine on OCaml 4.04.0 + ppc64)
> >
> > The implementation of Zarith is quite complex and I've so far failed
> > to understand what's going on.
>
> FWIW this seems like it is invoking undefined behaviour in C. See
> my analysis here:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1392247#c3
>
> Rich.
What I don't get is why this ihappens only on ppc64le. For it to
consistently return 0 there has to be some check in there for negative
values. But that check is only present in some specialized ppc64le
code? Seems like something the generic code for all archs should
already have.
Just out of interest: So what's so special about ppc64le that checking
for negatives is present just there?
MfG
Goswin
next prev parent reply other threads:[~2016-11-08 10:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-07 13:22 Richard W.M. Jones
2016-11-07 13:31 ` Nicolas Ojeda Bar
2016-11-07 13:55 ` Francois BERENGER
2016-11-07 14:11 ` Sylvain Le Gall
2016-11-07 14:59 ` Simon Cruanes
2016-11-15 9:11 ` Bernhard Schommer
2016-11-07 15:48 ` Richard W.M. Jones
2016-11-07 15:58 ` Xavier Leroy
2016-11-07 16:19 ` Richard W.M. Jones
2016-11-08 10:00 ` Goswin von Brederlow [this message]
2016-11-08 11:10 ` Richard W.M. Jones
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