Re: About GSOC.

[Tejas Joshi <tejasjoshi9673@gmail.com>]

Hello.
I tried to check the values for significand words using _Float128
using a test program with value larger than 64 bit.
Test program :

int main ()
{
    _Float128 x = 18446744073709551617.5;   (i.e. 2^64 + 1.5 which is
certainly longer than 64-bit)
    _Float128 y = __builtin_roundf128 (x);
}

The lower words of significand (sig[1] and sig[0] for 64-bit system)
are still being zero. I haven't included the roundevenf128 yet but
inspecting this on real_round function.
Am I missing something here?

Thanks.


On Wed, 29 May 2019 at 16:56, Tejas Joshi <tejasjoshi9673@gmail.com> wrote:
>
> Hello.
> My exams are finally over and I have started to address these points now. I intend to give my most of the time cause of holidays and will try to consider most of the cases for the patch this time .
>
> Thanks,
> -Tejas
>
> On Tue, 21 May 2019 at 03:18, Joseph Myers <joseph@codesourcery.com> wrote:
>>
>> On Mon, 20 May 2019, Martin Jambor wrote:
>>
>> > in addition to the things already pointed out by Joseph, I have the
>> > following comments.  But as Joseph has already pointed out, you should
>> > also test your patch on __float128 types, so please make sure your code
>> > gets invoked and works for something like:
>> >
>> >     if (__builtin_roundevenf128 (0x1p64q+0.5) != (0x1p64q))
>> >       link_error (__LINE__);
>>
>>  ... but with the f128 constant suffix not q, so it works on more
>> architectures (all those with _Float128 support, not just those with older
>> __float128 support).
>>
>> > > +DEF_EXT_LIB_BUILTIN    (BUILT_IN_ROUNDEVEN, "roundeven", BT_FN_DOUBLE_DOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
>> > > +DEF_EXT_LIB_BUILTIN    (BUILT_IN_ROUNDEVENF, "roundevenf", BT_FN_FLOAT_FLOAT, ATTR_CONST_NOTHROW_LEAF_LIST)
>> > > +DEF_EXT_LIB_BUILTIN    (BUILT_IN_ROUNDEVENL, "roundevenl", BT_FN_LONGDOUBLE_LONGDOUBLE, ATTR_CONST_NOTHROW_LEAF_LIST)
>> >
>> > ...and for the code to trigger for __builtin_roundevenf128 you have to
>> > define this builtin function too.  The easiest way is to do it in the
>> > same way it is done for BUILTIN_ROUND and many other functions, i.e. use
>> > DEF_EXT_LIB_FLOATN_NX_BUILTINS.
>>
>> Also note that TS 18661-1 has been merged into C2X.  I haven't yet updated
>> glibc headers to reflect this, but this means a new DEF_C2X_BUILTIN should
>> be added similar to DEF_C11_BUILTIN, and used for those three new
>> functions, instead of DEF_EXT_LIB_BUILTIN.  (And for the strdup and
>> strndup built-in functions, also added to C2X, but that's independent of
>> the present project.)
>>
>> --
>> Joseph S. Myers
>> joseph@codesourcery.com