Tejas Belagod <tejas.bela...@arm.com> writes:
> On 5/30/24 6:28 PM, Richard Sandiford wrote:
>> Tejas Belagod <tejas.bela...@arm.com> writes:
>>> Currently poly-int type structures are passed by value to OpenMP runtime
>>> functions for shared clauses etc. This patch improves on this by passing
>>> around poly-int structures by address to avoid copy-overhead.
>>>
>>> gcc/ChangeLog
>>> * omp-low.c (use_pointer_for_field): Use pointer if the OMP data
>>> structure's field type is a poly-int.
>>> ---
>>> gcc/omp-low.cc | 3 ++-
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/gcc/omp-low.cc b/gcc/omp-low.cc
>>> index 1a65229cc37..b15607f4ef5 100644
>>> --- a/gcc/omp-low.cc
>>> +++ b/gcc/omp-low.cc
>>> @@ -466,7 +466,8 @@ static bool
>>> use_pointer_for_field (tree decl, omp_context *shared_ctx)
>>> {
>>> if (AGGREGATE_TYPE_P (TREE_TYPE (decl))
>>> - || TYPE_ATOMIC (TREE_TYPE (decl)))
>>> + || TYPE_ATOMIC (TREE_TYPE (decl))
>>> + || POLY_INT_CST_P (DECL_SIZE (decl)))
>>> return true;
>>>
>>> /* We can only use copy-in/copy-out semantics for shared variables
>>
>
> Thanks for the reviews.
>
>> Realise this is also true of my original patch, but:
>>
>> I suppose a question here is whether this function is only ever used for
>> local interfaces between code generated by the same source code function,
>> or whether it's ABI in a more general sense.
>
> I'm not a 100% sure, but AFAICS, 'use_pointer_for_field' seems to be
> used only for local interface between source and generated functions. I
> don't see any backend hooks into this or backend hooking into this
> function for general ABI. Ofcourse, I'm not the expert on OMP lowering,
> so it would be great to get an expert opinion on this.
>
>> If the latter, I suppose
>> we should make sure to handle ACLE types the same way regardless of
>> whether the SVE vector size is known.
>>
>
> When you say same way, do you mean the way SVE ABI defines the rules for
> SVE types?
No, sorry, I meant that if the choice isn't purely local to a source
code function, the condition should be something like sizeless_type_p
(suitably abstracted) rather than POLY_INT_CST_P. That way, the "ABI"
stays the same regardless of -msve-vector-bits.
Thanks,
Richard
