getting the right boolean type

[Andrew MacLeod]

On 11/09/2017 10:29 AM, Richard Biener wrote:
> On Thu, Nov 9, 2017 at 4:24 PM, Andrew MacLeod <amacleod@redhat.com> wrote:
>> On 11/09/2017 10:16 AM, Richard Biener wrote:
>>> On Thu, Nov 9, 2017 at 3:44 PM, Andrew MacLeod <amacleod@redhat.com>
>>> wrote:
>>>> I'm a little confused.  In gimple I need to do a comparison between 2
>>>> values, and I create a boolean_type_node result.
>>>> I then combine it with an existing condition, but fortran is crapping out
>>>> on
>>>> me because the boolean_type I created is not
>>>> compatible with the boolean type is has already created for a different
>>>> condition:
>>>>
>>>> Its not exactly this situation, but the idea is similar:
>>>>
>>>>    _65 = _37 != 0;    <<-- in the IL
>>>>    _77 = _34 != 0;    <<-- Im creating this
>>>>
>>>>    and something like
>>>>
>>>>      (_65 != _77)
>>>>
>>>>    Craps out on me because the types are incompatible.
>>>>
>>>> The expression created by fortran assigned to _65 is of type:
>>>> logical(kind=4)
>>>> and mine, _77 created with boolean_type_node, is logical(kind=1)
>>>>
>>>> I was under the impression that using boolean_type_node would give me the
>>>> right kind of boolean for that language, but apparently I was mistaken.
>>>>
>>>> If I don't have the context of the type of _65,  how am I suppose to get
>>>> the
>>>> right boolean type for _77 when I create it? I don't want to cast it to
>>>> the
>>>> right logical kind, Id like to just get it right.   I haven't stumbled
>>>> across any hooks or other obvious thing...
>>>>
>>>> I feel like I am missing something obvious...  :-P
>>> You should already know the boolean type from the existing comparison in
>>> the IL.
>>> That is, you shouldn't generate conditions out of thin air, do you?  That
>>> is,
>>> there isn't a "single" boolean type a random hook would tell you.
>>>
>>> Richard.
>> Yeah, I do actually generate them from thin air :-)   That why I said it
>> wasnt exactly that situation.  All I have is 2 arbitrary things that are
>> being compared, and then eventually I sometimes end up combining it with an
>> existing boolean.  I dont know in advance that I will need to combine it. I
>> chose boolean_type_node because I thought it was the default.
> Sure - you can use boolean_type_node.  Then when combining you need
> to convert to a common boolean type (choose any).  Eventually forwprop
> will retroactively "fix" your (or the other) generated comparison to produce
> the correct type in the first place.
>
>> I presume fortran is using SImode because it works better, or there is some
>> other subtle difference?
> Fortran has boolean types of each size -- logical(1) to logical(16).
>
>>   so even if I wasn't eventually combining it with a
>> logical, and I was using the default  QImode, I would generate less than
>> ideal code?  Is there not a way for the optimizers to pick the preferred
>> type?
> The preferred type depends on the context and should almost always be
> boolean_type_node _unless_ the bool(s) you are working with are
> loaded from / stored to memory where of course the size of the bool
> matters.
>
OK, perfect, thats all I really need then...  I'll figure out how I want 
to deal with it.

THanks
Andrew.