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Re: AArch64 patches for glibc master.
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: "Joseph S. Myers" <joseph at codesourcery dot com>
- Cc: Marcus Shawcroft <marcus dot shawcroft at linaro dot org>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Mon, 09 Dec 2013 18:02:13 -0500
- Subject: Re: AArch64 patches for glibc master.
- Authentication-results: sourceware.org; auth=none
- References: <52A60A93 dot 1050402 at redhat dot com> <Pine dot LNX dot 4 dot 64 dot 1312091852010 dot 17984 at digraph dot polyomino dot org dot uk> <52A61590 dot 9060303 at redhat dot com> <Pine dot LNX dot 4 dot 64 dot 1312092136450 dot 22134 at digraph dot polyomino dot org dot uk>
On 12/09/2013 04:40 PM, Joseph S. Myers wrote:
> On Mon, 9 Dec 2013, Carlos O'Donell wrote:
>>> * You're adding ulps for sqrt, which should always be exact.
>> I wasn't aware that sqrt should always be exact. I'll try to
>> educate myself on that. Do you have any pointers on where I can
>> read about that?
> If a function is bound to an IEC 60559 operation, it should always be
> exact (correctly rounding according to the current rounding direction and
> with a correct set of exceptions raised including "inexact" as
> applicable). For example, C11 F.3 says "The sqrt functions in <math.h>
> provide the IEC 60559 square root operation.". Other functions that
> should never have ulps include rint, fma, scalbn.
Is this requirement because IEC 60559 requires everything to be correctly
rounded, therefore if C11 defines sqrt in terms of the IEC 60559 operation
then the function itself must be correctly rounding as required by the
standard (IEEE Std 754-2008)?