This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: [PATCH] gfortran -- Map REAL128 to REAL kind type with widest precision
On Fri, Feb 10, 2017 at 9:14 PM, Jerry DeLisle <jvdelisle@charter.net> wrote:
> On 02/09/2017 08:05 PM, Steve Kargl wrote:
>>
>> On Thu, Feb 09, 2017 at 07:35:11PM -0800, Jerry DeLisle wrote:
>>>
>>> On 02/09/2017 12:40 PM, Janne Blomqvist wrote:
>>>>
>>>> On Thu, Feb 9, 2017 at 8:33 PM, Steve Kargl
>>>> <sgk@troutmask.apl.washington.edu> wrote:
>>>>>
>>>>> On Thu, Feb 09, 2017 at 12:10:02PM +0200, Janne Blomqvist wrote:
>>>>>>
>>>>>>
>>>>>> That being said, I think even with Steve's patch, it's not guaranteed
>>>>>> to give you IEEE 754-2008 binary128. E.g. on IBM POWER targets,
>>>>>> depending on the ABI you may get an IBM extended double (double-double
>>>>>> or __ibm128) format. Although if IEEE binary128 is also available,
>>>>>> with Steve's patch you should get that one has it has more precision
>>>>>> that __ibm128.
>>>>>
>>>>>
>>>>> I do not have to a IBM POWER system, so cannot easily check the
>>>>> effect of my patch.
>>>
>>>
>>> On IBM Power
>>>
>>> program foo
>>> use iso_fortran_env
>>> REAL(REAL128) x
>>> print '(3(I0,1X))', kind(x), digits(x), precision(x)
>>> end program foo
>>>
>>> $ gfc -static foo.f90
>>> $ ./a.out
>>> 16 106 31
>>>
>>
>> That is the double-double format. The gcc manual says that
>> powerpc takes a -mfloat128 option (among others). This will
>> probably give you 16 113 33.
>>
>
> $ gfc -static -mfloat128 foo.f90
>
> $ ./a.out
> 16 106 31
Hmm, fascinating. What about
-mfloat128 -mcpu=power9
-mfloat128 -mabi=ieeelongdouble
-mfloat128 -mcpu=power9 -mabi=ieeelongdouble
?
(see https://gcc.gnu.org/wiki/Ieee128PowerPC for details)
--
Janne Blomqvist