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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/55559] [4.6/4.7/4.8 Regression] Marshalling double through union with inlines, incorrect behavior with -O2
Date: Tue, 04 Dec 2012 09:03:00 -0000	[thread overview]
Message-ID: <bug-55559-4-7y3WXUj4Td@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-55559-4@http.gcc.gnu.org/bugzilla/>


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55559

--- Comment #8 from rguenther at suse dot de <rguenther at suse dot de> 2012-12-04 09:02:00 UTC ---
On Mon, 3 Dec 2012, mpreda at gmail dot com wrote:

> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55559
> 
> --- Comment #7 from Mihai Preda <mpreda at gmail dot com> 2012-12-03 22:13:03 UTC ---
> Thanks, I didn't realize that (unsigned)-1.0 is undefined.
> 
> For the behavior I was expecting it's enough to use an intermediary cast
> through int, e.g. (unsigned)(int)-1.0.

Yes, that makes it implementation-defined (and all implementations
I know of do what you expect, modulo-two reduction).

> It may be nice to generate a consistent (-O0/-O1) result for (unsigned)-1.0
> though, even if not required by the standard.

That's unfortunately generally impossible.


      parent reply	other threads:[~2012-12-04  9:03 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-12-01 22:56 [Bug c++/55559] New: " mpreda at gmail dot com
2012-12-02  0:10 ` [Bug tree-optimization/55559] " pinskia at gcc dot gnu.org
2012-12-02 11:16 ` mikpe at it dot uu.se
2012-12-02 16:05 ` mikpe at it dot uu.se
2012-12-03 11:44 ` [Bug tree-optimization/55559] [4.6/4.7/4.8 Regression] " rguenth at gcc dot gnu.org
2012-12-03 12:30 ` rguenth at gcc dot gnu.org
2012-12-03 12:52 ` paolo.carlini at oracle dot com
2012-12-03 22:13 ` mpreda at gmail dot com
2012-12-04  9:03 ` rguenther at suse dot de [this message]

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