https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110347
--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
An explicit 'firstprivate(x)' will be turned in the compiler from a FIELD_DECL
to:
int D.2935 [value-expr: ((struct t *) this)->x];
#pragma omp target firstprivate(D.2934) firstprivate(D.2935)
{
(void) (D.2935 = 5)
in semantics.cc's omp_privatize_field, called by finish_omp_clauses for
handle_field_decl. The gimple dump then looks like:
int x [value-expr: ((struct t *) this)->x];
#pragma omp target ... firstprivate(x)
map(alloc:MEM[(char *)this] [len: 0])
map(firstprivate:this [pointer assign, bias: 0])
{
this->x = 5;
i.e. there is already a pointless 'this' mapping.
For 'private', we could do in omp_privatize_field a simple:
v = build_decl (input_location, VAR_DECL, DECL_NAME (t),
TREE_TYPE (t));
but for 'firstprivate' that would miss the initialization - and adding a
pointless assignment is not really the best, especially not for larger objects
(like structs, arrays, reference types).
* * *
And for 'defaultmap(firstprivate)', the current code already adds 'this'
mapping in the original dump:
#pragma omp target map(tofrom:*(struct t *) this [len: 44])
map(firstprivate:(struct t *) this [pointer assign, bias: 0])
defaultmap(firstprivate:all)
{
{
(void) (((struct t *) this)->x = 5);
That's due to 'finish_omp_target_clauses_r' + data->this_expr_accessed = true;
it either needs to be suppressed here - or later in the ME removed again. The
former has the problem that 'defaultmap(firstprivate)' is not handled here, the
latter means a special case - ensuring that it is only removed if all member
accesses are for firstprivatized members.
While 'private' does not exist as defaultmap, compiler-internal handling or
(not checked) predefined/implicit mapping might.
