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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/46080] [4.4/4.5/4.6 Regression] incorrect precision of sqrtf builtin for x87 arithmetic (-mfpmath=387)
Date: Wed, 20 Oct 2010 08:29:00 -0000 [thread overview]
Message-ID: <20101020082900.G4_xsNGc5zWJ-_OdAdD55xvz0XYbrW70Ak6KdtGjHbs@z> (raw)
In-Reply-To: <bug-46080-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46080
--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2010-10-20 08:28:57 UTC ---
(In reply to comment #2)
> Created attachment 22089 [details]
> sh script to test sqrtf
>
> Similar problems can also be found with:
>
> printf ("%.60f\n%.60f\n%.60f\n", sqrtf(x), sqrtf(x), sqrtf(x));
>
> I've found that every GCC version I could test was showing some incorrect
> behavior (but GCC 4.2.4 was the most consistent one). With the attached script,
> I get:
>
> -DSEP -O0 -O1 -O2
> GCC 3.4.6 SSS SSS SDD SDD
> GCC 4.1.3 SSS SSS DSS DDS
> GCC 4.2.4 SSS SSS DDD DDD (x86)
> GCC 4.3.5 SSS SSS DSS DDD (ditto with GCC 4.3.2 on x86)
> GCC 4.4.5 DSS SSD DSS DDD
>
> where S means that one gets the result in single precision (as expected) and D
> means that one gets the result in double precision.
You should use -ffloat-store to remove excess precision.
next prev parent reply other threads:[~2010-10-20 8:29 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-19 8:55 [Bug target/46080] New: " vincent at vinc17 dot org
2010-10-19 10:49 ` [Bug target/46080] [4.4/4.5/4.6 Regression] " rguenth at gcc dot gnu.org
2010-10-20 1:52 ` vincent at vinc17 dot org
2010-10-20 8:29 ` ubizjak at gmail dot com [this message]
2010-10-20 9:39 ` jakub at gcc dot gnu.org
2010-10-20 9:54 ` zimmerma+gcc at loria dot fr
2010-10-20 10:46 ` jakub at gcc dot gnu.org
2010-10-20 23:43 ` vincent at vinc17 dot org
2010-10-20 23:49 ` pinskia at gcc dot gnu.org
2010-10-21 19:26 ` zimmerma+gcc at loria dot fr
2010-10-21 20:56 ` jakub at gcc dot gnu.org
2010-10-22 6:56 ` zimmerma+gcc at loria dot fr
2010-10-26 13:41 ` jakub at gcc dot gnu.org
2010-11-12 14:35 ` rguenth at gcc dot gnu.org
2010-11-16 10:56 ` jakub at gcc dot gnu.org
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