Hi Chung-Lin,
https://gcc.gnu.org/pipermail/gcc-patches/2024-January/641669.html
Chung-Lin Tang wrote:
this patch implements reductions for arrays and structs for OpenACC. Following
the pattern for OpenACC reductions [...]
(Stumbled over while looking at the Fortran patch, but applying to
C/C++, hence mentioned here; the Fortran patch is at
https://gcc.gnu.org/pipermail/gcc-patches/2024-February/645205.html )
OpenACC permits array elements and subarrays. I have not checked whether
array elements are currently rejected or fully supported, but I miss a
testcase for both array elements (unless there is one already) and array
sections.
If implemented, I think there should be a working run-time test.
If not supported, there should be a sorry_at error for those.
Note: the parser should handle array sections as OpenMP handles them.
The testcase should cover something like the following:
void f(int n)
{
int x[5][5]; // Multimensional array;
int y[n]; // VLA
int *z = (int*)malloc(5*5*sizeof(int)); // Allocated array
... reduction(+:x)
... reduction(+:y)
... reduction(+:x[0:5][2:1]) // OK
... reduction(+:x[1:4][2:1])
// invalid - while contiguous, first dim does not span the whole array
... reduction(+:y[2:2]) // OK
... reduction(+:y[3:]) // OK - same as [3:n-3]
... reduction(+:y[:2]) // OK - same as [0:2]
... reduction(+:z[1:2][1:6]) // OK
And the same where at least one of the const number is replaced by
a variable.
Note: The 'invalid' reduction is fine in terms of being contiguous (last
dimension contains a single element, hence, the dimension before does
not need to span the whole extend) - but OpenACC requires the all
dimensions but the last to span the whole range.
See "2.7.1 Data Specification in Data Clauses" for the subarray description.
I think - if known at compile time - there should be also a diagnostic
if the any dimension but the last does not span the whole range.
Thanks,
Tobias
