From: Richard Sandiford <rdsandiford@googlemail.com>
To: "Maciej W. Rozycki" <macro@codesourcery.com>
Cc: "Jürgen Urban" <JuergenUrban@gmx.de>,
binutils@sourceware.org, gcc-patches@gcc.gnu.org
Subject: Re: Support for MIPS r5900
Date: Sat, 19 Jan 2013 10:53:00 -0000 [thread overview]
Message-ID: <8738xxmok7.fsf@talisman.default> (raw)
In-Reply-To: <alpine.DEB.1.10.1301172232280.4834@tp.orcam.me.uk> (Maciej W. Rozycki's message of "Thu, 17 Jan 2013 23:22:36 +0000")
"Maciej W. Rozycki" <macro@codesourcery.com> writes:
>> I tested the calculation with the type "float".
>> ABI o32 with -mhard-float and -msingle-float produces the following results:
>> 1.000000 (0x3f800000) / 0.000000 (0x00000000) = nan (0x7fffffff)
>> 0.000000 (0x00000000) / 0.000000 (0x00000000) = nan (0x7fffffff)
>> 0.000000 (0x00000000) / nan (0x7fc00000) = 0.000000 (0x00000000)
>> 1.000000 (0x3f800000) + 1.000000 (0x3f800000) = 2.000000 (0x40000000)
>> 1.000000 (0x3f800000) + inf (0x7f800000) = inf (0x7f800000)
>> inf (0x7f800000) + inf (0x7f800000) = nan (0x7fffffff)
>> inf (0x7f800000) + -inf (0xff800000) = 0.000000 (0x00000000)
>> nan (0x7fc00000) + nan (0x7fc00000) = nan (0x7fffffff)
>> nan (0x7fc00000) + nan (0xffc00000) = 0.000000 (0x00000000)
>>
>> The r5900 manual calls the result of 0/0 Fmax. So 0x7fffffff seems to be Fmax.
>
> So presumably you can get 0x7fffffff as an arithmetic result of a
> calculation involving regular numbers as well, right? Say 0x7f7ffffe +
> 0x74000000 (using the binary-encoded notation)? That would be beyond the
> IEEE-754 single range.
Yeah, if I recall correctly. We already support what I think is the
same format for SPU (spu_single_format), which I suppose makes sense
given its heritage. Hopefully the format itself won't need much
work in GCC.
Richard
next prev parent reply other threads:[~2013-01-19 10:53 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-06 22:57 "Jürgen Urban"
2013-01-07 17:15 ` Jeff Law
2013-01-07 20:44 ` Richard Sandiford
2013-01-07 21:52 ` Richard Sandiford
2013-01-08 0:23 ` Maciej W. Rozycki
2013-01-08 7:28 ` Richard Sandiford
2013-01-08 17:24 ` Maciej W. Rozycki
2013-01-08 18:25 ` Richard Sandiford
2013-01-08 22:34 ` "Jürgen Urban"
2013-01-10 23:25 ` Maciej W. Rozycki
2013-01-11 9:49 ` Richard Sandiford
2013-01-11 16:55 ` Maciej W. Rozycki
2013-01-13 14:16 ` "Jürgen Urban"
2013-01-14 18:42 ` Maciej W. Rozycki
2013-01-17 22:21 ` "Jürgen Urban"
2013-01-17 23:23 ` Maciej W. Rozycki
2013-01-19 10:53 ` Richard Sandiford [this message]
2013-01-20 21:43 ` "Jürgen Urban"
2013-01-08 4:22 ` Jeff Law
2013-01-08 7:22 ` Richard Sandiford
2013-01-08 22:49 ` "Jürgen Urban"
2013-01-09 5:25 ` Jeff Law
2013-01-10 22:59 ` "Jürgen Urban"
2013-01-11 4:41 ` Jeff Law
2013-01-08 7:16 ` Richard Sandiford
2013-01-08 21:30 ` "Jürgen Urban"
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