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Re: Architecture floating-point underflow information wanted
- From: "Carlos O'Donell" <carlos at systemhalted dot org>
- To: "Joseph S. Myers" <joseph at codesourcery dot com>
- Cc: libc-alpha at sourceware dot org, libc-ports at sourceware dot org, Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>, Richard Henderson <rth at twiddle dot net>, Mark Salter <msalter at redhat dot com>, Mike Frysinger <vapier at gentoo dot org>, Andreas Schwab <schwab at linux-m68k dot org>
- Date: Tue, 25 Sep 2012 11:21:56 -0400
- Subject: Re: Architecture floating-point underflow information wanted
- References: <Pine.LNX.4.64.1209251238230.12872@digraph.polyomino.org.uk><CAE2sS1jYLx5is-x9U6f2pmRopVJS8T4ypV60j64ABop3TcY-qA@mail.gmail.com>
On Tue, Sep 25, 2012 at 11:17 AM, Carlos O'Donell
<carlos@systemhalted.org> wrote:
> On Tue, Sep 25, 2012 at 8:52 AM, Joseph S. Myers
> <joseph@codesourcery.com> wrote:
>> As part of fixing bug 14047, I'd like information about how each glibc
>> architecture (libc and ports) detects floating-point underflow. (IEEE
>> 754-2008 gives two options: "before rounding" (exponent would be below
>> normal range if both exponent range and mantissa precision were unbounded)
>> and "after rounding" (exponent of the rounded value would be below normal
>> range if the exponent range were unbounded and values with all exponents
>> had the same mantissa precision as for normal values).)
>
> Thanks for the test case.
>
>> I'm looking for information for the following architectures:
>>
>> s390-32, s390-64
>> alpha
>> am33
>> hppa
>> ia64
>> m68k (classic)
>
> hppa (64-bit PA-RISC 2.0) is after rounding according to the test.
>
> The manual says:
> ~~~
> Tininess is detected on a nonzero result which lies strictly between
> +/-2^(Emin), when the result is rounded as if the exponent range were
> unbounded.
> ~~~
>
> Thus verified by what the manual says.
Verified that PA-RISC 1.1 hardware is also after rounding according to
the manual.
I have not booted real 1.1 hardware to verify.
Cheers,
Carlos.