Re: Desire to allocate bit in DT_PARM bitmask for DEC FORMAT compatibility purposes

[Jeff Law <law at redhat dot com>]

On 03/21/2018 12:38 PM, Janne Blomqvist wrote:
> On Wed, Mar 21, 2018 at 7:29 PM, Jeff Law <law@redhat.com> wrote:
>> On 03/21/2018 11:25 AM, Jakub Jelinek wrote:
>>> On Tue, Mar 20, 2018 at 12:41:25PM -0600, Jeff Law wrote:
>>>> This is documented in the old manuals from DEC and I've found
>>>> essentially the same documentation in Oracle/Sun's current documentation
>>>> as well as old MIPS documentation.   I have a high degree of confidence
>>>> it exists in IBM's Fortran compilers as well.  In contrast Intel & PCG's
>>>> Fortran compilers do not seem to support this extension.
>>>
>>> My testing disagrees with the last one, at least ifort 17.0.4 handles
>>> the default widths like this patch does with -fdec.
>> I was going from what I could find in the online documentation.  I could
>> have missed it, or it could be undocumented behavior.
> 
> FWIW, IIRC the lineage of the Intel Fortran compiler frontend is that
> at some point DEC did a Fortran compiler for Windows (Digital Visual
> Fortran, DVF. Though I don't know to which extent the actual compiler
> differed from the DEC Unix/VAX Fortran compilers, was it a port or a
> completely different codebase?), which became Compaq Visual Fortran
> (CVF). Then at some point Intel bought the product and the team which
> developed it from Compaq (or maybe it was already HP at the time, I
> don't remember), and it became Intel Fortran.
Thanks.

> 
> So if any current compiler would support the various DEC extensions,
> it would be Intel. And if anything, I suppose Intel behavior defines
> the "canonical" behavior for the DEC extensions.
> 
>  As for the implementation of the patch itself, you might want to
> discuss it with Fritz Reese who has somewhat recently implemented the
> other -fdec-* stuff. One thing which struck me was that you (or
> whoever implemented it???) has reinvented setting the various default
> widths, code which already exists in libgfortran in order to support
> list directed output and zero width formats (zero width formats being,
> roughly, the standardized version of the DEC Format extension).
Happy to ping Fritz on this stuff.  I've looked at some of his changes
while cleaning up the Codethink patches.

Also happy to look into sharing those bits rather than reinvention.

Thanks!

jeff