[PR72741] Encode OpenACC 'routine' directive's level of parallelism inside Fortran module files

[Thomas Schwinge]

Hi!

On Thu, 28 Feb 2019 22:17:01 +0100, Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, Feb 28, 2019 at 10:12:00PM +0100, Thomas Schwinge wrote:
> > On Wed, 15 Jun 2016 20:12:15 -0700, Cesar Philippidis <cesar@codesourcery.com> wrote:
> > The code changes now are actually very simple.  The "problem" is that
> > we're incrementing the Fortran module version, 'MOD_VERSION', which
> > breaks binary compatibility with Fortran module files created with
> > earlier versions of GCC, which is something that is to be avoided, as
> > I've heard.  Or, is it not that bad actually?
> 
> It is bad and we certainly shouldn't change it on release branches.

ACK.

> There are many ways to deal with it without bumping MOD_VERSION in a
> backwards but not forwards compatible way, so that a newer compiler will be
> able to parse old *.mod files, and newer compiler new ones as long as this
> problematic stuff doesn't appear in.

Like the attached, actually pretty simple now?

It may seem wasteful to use individual bits for 'gang', 'worker',
'vector', 'seq', but that makes it easy to implement the behavior
described above by Jakub, and I've heard rumors that OpenACC might at
some point allow several of these level of parallelism clauses to be
specified (plus a new 'auto' clause?), and then this will be necessary
anyway (several of these bits can then in fact appear).

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Grüße
 Thomas


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