[PATCH, fortran, PR 82869] Introduce default_logical_type_node and logical_type_node

[Janne Blomqvist]

On Wed, Nov 8, 2017 at 12:27 AM, Steve Kargl
<sgk@troutmask.apl.washington.edu> wrote:
> On Tue, Nov 07, 2017 at 10:38:43PM +0200, Janne Blomqvist wrote:
>> On Tue, Nov 7, 2017 at 10:06 PM, Steve Kargl
>> <sgk@troutmask.apl.washington.edu> wrote:
>> > On Tue, Nov 07, 2017 at 08:26:15PM +0200, Janne Blomqvist wrote:
>> >> +
>> >> +  logical_type_node = gfc_get_logical_type (4);
>> >
>> > Can you add a comment to note that the 4 is purposely chosen?
>> > A year or so from now, someone might change this to gfc_default_logical_kind
>> > without understand/recalling why 4 is used.
>>
>> The patch contains a comment explaining that in trans-types.h.
>
> Well, did say I scanned the patch ;-)
>
>> However, a bit of further experimenting with my patch revealed that
>> one can cause these latent bugs I feared to appear by playing with
>> -fdefault-integer-8 / -finteger-4-integer-8 with the example from
>> bugzilla (so we end up passing a pointer to a logical(kind=4) variable
>> but we tell libgfortran it's kind=8). I did fix the most obvious ones
>> in the attached patch (on top of the previous one), but I'm not
>> convinced it's exhaustive.
>>
>> So I wonder, do we actually care enough about -fdefault-integer-8 /
>> -finteger-4-integer-8 to do this kind of micro-optimization (i.e. use
>> 4 byte logical temporary variables if we can even when we use
>> -fdefault-integer-8 / -finteger-4-integer-8), or should we play it
>> safe and just use default_logical_type_node everywhere?
>
> I certainly don't care about fallout when one uses -fdefault-*
> options.  I've stated more than once I think these should
> be removed, because these options break storage association
> (among other things).  I a little surprise that -finteger-4-integer-8
> have an effect, but I admit I haven't looked closely at the
> internal representation of a Fortran logical and its relationship
> to INTEGER(4).
>
> --
> steve


So in the end I decided to play it safe and do the simpler approach.
Patch that I committed as r254526 attached. Unless there are
objections, I'll apply it to the GCC-7 tree in a few days as well
since it's a regression.


-- 
Janne Blomqvist
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