Re: [PATCH] Automatics in equivalence statements

[Jeff Law <law at redhat dot com>]

On 7/1/19 3:35 AM, Mark Eggleston wrote:
> 
> On 25/06/2019 14:17, Mark Eggleston wrote:
>>
>> On 25/06/2019 00:17, Jeff Law wrote:
>>> On 6/24/19 2:19 AM, Bernhard Reutner-Fischer wrote:
>>>> On Fri, 21 Jun 2019 07:10:11 -0700
>>>> Steve Kargl <sgk@troutmask.apl.washington.edu> wrote:
>>>>
>>>>> On Fri, Jun 21, 2019 at 02:31:51PM +0100, Mark Eggleston wrote:
>>>>>> Currently variables with the AUTOMATIC attribute can not appear in an
>>>>>> EQUIVALENCE statement. However its counterpart, STATIC, can be
>>>>>> used in
>>>>>> an EQUIVALENCE statement.
>>>>>>
>>>>>> Where there is a clear conflict in the attributes of variables in an
>>>>>> EQUIVALENCE statement an error message will be issued as is currently
>>>>>> the case.
>>>>>>
>>>>>> If there is no conflict e.g. a variable with a AUTOMATIC attribute
>>>>>> and a
>>>>>> variable(s) without attributes all variables in the EQUIVALENCE will
>>>>>> become AUTOMATIC.
>>>>>>
>>>>>> Note: most of this patch was written by Jeff Law <law@redhat.com>
>>>>>>
>>>>>> Please review.
>>>>>>
>>>>>> ChangeLogs:
>>>>>>
>>>>>> gcc/fortran
>>>>>>
>>>>>>       Jeff Law  <law@redhat.com>
>>>>>>       Mark Eggleston  <mark.eggleston@codethink.com>
>>>>>>
>>>>>>       * gfortran.h: Add check_conflict declaration.
>>>>> This is wrong.  By convention a routine that is not static
>>>>> has the gfc_ prefix.
> Updated the code to use gfc_check_conflict instead.
>>>>>
>>>> Furthermore doesn't this export indicate that you're committing a
>>>> layering violation somehow?
>>> Possibly.  I'm the original author, but my experience in our fortran
>>> front-end is minimal.  I fully expected this patch to need some
>>> tweaking.
>>>
>>> We certainly don't want to recreate all the checking that's done in
>>> check_conflict.  We just need to defer it to a later point --
>>> find_equivalence seemed like a good point since we've got the full
>>> equivalence list handy and can accumulate the attributes across the
>>> entire list, then check for conflicts.
>>>
>>> If there's a concrete place where you think we should be doing this, I'm
>>> all ears.
>>>
>> Any suggestions will be appreciate.
>>>>>       * symbol.c (check_conflict): Remove automatic in equivalence
>>>>> conflict
>>>>>       check.
>>>>>       * symbol.c (save_symbol): Add check for in equivalence to
>>>>> stop the
>>>>>       the save attribute being added.
>>>>>       * trans-common.c (build_equiv_decl): Add is_auto parameter and
>>>>>       add !is_auto to condition where TREE_STATIC (decl) is set.
>>>>>       * trans-common.c (build_equiv_decl): Add local variable is_auto,
>>>>>       set it true if an atomatic attribute is encountered in the
>>>>> variable
>>>> atomatic? I read atomic but you mean automatic.
>>> Yes.
>>>
>>>>>       list.  Call build_equiv_decl with is_auto as an additional
>>>>> parameter.
>>>>>       flag_dec_format_defaults is enabled.
>>>>>       * trans-common.c (accumulate_equivalence_attributes) : New
>>>>> subroutine.
>>>>>       * trans-common.c (find_equivalence) : New local variable
>>>>> dummy_symbol,
>>>>>       accumulated equivalence attributes from each symbol then
>>>>> check for
>>>>>       conflicts.
>>>> I'm just curious why you don't gfc_copy_attr for the most part of
>>>> accumulate_equivalence_attributes?
>>>> thanks,
>>> Simply didn't know about it.  It could probably significantly simplify
>>> the accumulation of attributes step.
>> Using gfc_copy_attr causes a great many "Duplicate DIMENSION attribute
>> specified at (1)" errors. This is because there is a great deal of
>> checking done instead of simply keeping track of the attributes used
>> which is all that is required for determining whether there is a
>> conflict in the equivalence statement.
>>
>> Also, the final section of accumulate_equivalence_attributes involving
>> SAVE, INTENT and ACCESS look suspect to me. I'll check and update the
>> patch if necessary.
> 
> No need to check intent as there is already a conflict with DUMMY and
> INTENT can only be present for dummy variables.
> 
> Please find attached an updated patch. Change logs:
> 
> gcc/fortran
> 
>     Jeff Law  <law@redhat.com>
>     Mark Eggleston  <mark.eggleston@codethink.com>
> 
>     * gfortran.h: Add gfc_check_conflict declaration.
>     * symbol.c (check_conflict): Rename cfg_check_conflict and remove
>     static.
>     * symbol.c (cfg_check_conflict): Remove automatic in equivalence
>     conflict check.
>     * symbol.c (save_symbol): Add check for in equivalence to stop the
>     the save attribute being added.
>     * trans-common.c (build_equiv_decl): Add is_auto parameter and
>     add !is_auto to condition where TREE_STATIC (decl) is set.
>     * trans-common.c (build_equiv_decl): Add local variable is_auto,
>     set it true if an atomatic attribute is encountered in the variable
>     list.  Call build_equiv_decl with is_auto as an additional parameter.
>     flag_dec_format_defaults is enabled.
>     * trans-common.c (accumulate_equivalence_attributes) : New subroutine.
>     * trans-common.c (find_equivalence) : New local variable dummy_symbol,
>     accumulated equivalence attributes from each symbol then check for
>     conflicts.
> 
> gcc/testsuite
> 
>     Mark Eggleston <mark.eggleston@codethink.com>
> 
>     * gfortran.dg/auto_in_equiv_1.f90: New test.
>     * gfortran.dg/auto_in_equiv_2.f90: New test.
>     * gfortran.dg/auto_in_equiv_3.f90: New test.
> 
> If the updated patch is acceptable, please can someone with the
> privileges commit the patch.
[ ... ]
BTW, I've put the latest version of this into my tester.  I don't expect
to see any problems, of course.

Jeff