Hi!
On Fri, 21 Jun 2019 13:46:09 +0200, I wrote:
> On Wed, 05 Jun 2019 11:25:07 +0200, I wrote:
> > I [...] had a look at what OpenMP 5.0
> > is saying about Fortran 'allocatable' in 'map' clauses [...]
>
> Will you (Jakub, and/or Fortran guys), please have a look at the attached
> test case.
>
> If I disable the '!$omp declare target (ar)', then this works with
> offloading enabled, otherwise it fails, and here is my understanding what
> happens.
>
> With '!$omp declare target (ar)' active, the array descriptor globally
> gets allocated on the device, via the 'offload_vars' handling in
> 'gcc/omp-offload.c' etc.
>
> Then, in 'gcc/omp-low.c:scan_sharing_clauses', the 'GOMP_MAP_TO_PSET(ar)'
> (which would update the array descriptor on the device after the
> host-side 'allocate') gets removed, because 'Global variables with "omp
> declare target" attribute don't need to be copied, the receiver side will
> use them directly'. So, on the device, we'll still have the dummy
> (unallocated) array descriptor, and will thus fail.
>
> But even with that behavior disabled, we'll still fail, because in
> 'libgomp/target.c:gomp_map_vars_internal', when processing the
> 'GOMP_MAP_TO_PSET(ar)', we find that 'ar' has already been mapped
> (globally, as mentioned above), so for 'n && n->refcount !=
> REFCOUNT_LINK', we'll call 'gomp_map_vars_existing', and that one again
> won't update device-side the array descriptor, because it's not
> 'GOMP_MAP_ALWAYS_TO_P'.
>
> Indeed, if I use '!$omp declare target link(ar)' ('link' added), then
> things seem to work as expected.
>
> Unless I got something wrong, at which level do you suggest this should
> be fixed?
So, handling 'declare'd 'allocatable's via the 'link' case does seem to
make some sense to me -- but not yet fully thought through, for example,
how that'd relate to the (default) 'to' property of '!$omp declare target
[to](ar)'? Is there even something in OpenMP that we'd indeed copy data
to the device (as opposed to just allocate)? Because, in OpenACC, we
actually do have '!$acc declare copyin', etc. (But what would that mean
with an 'allocatable'?)
Anyway, I tried a WIP patch, and I'm also attaching the previous test
case rewritten to add a '!$omp declare target' routine 'ar_properties' to
read the device-side array properties. However, compiling that for
offloading results in:
[...]/target-array-properties-allocatable-declare-1-2.f90:6: error:
variable 'ar' has been referenced in offloaded code but hasn't been marked to
be included in the offloaded code
6 | integer, allocatable :: ar(:,:,:)
|
lto1: fatal error: errors during merging of translation units
Same, if I use an explicit '!$omp declare target link(ar)'. (I thought
that was the very point of the 'link' clause, that you could then
reference such a variable in offloaded code; I shall re-read the
standards again. Or, is that just another bug?)
(There doesn't seem to be any Fortran libgomp test case exercising the
'!$omp declare target link'?)
For the record, for the corresponding OpenACC code, we get:
[...]/array-properties-allocatable-declare-1-2.f90:6:0:
6 | integer, allocatable :: ar(:,:,:)
|
Error: 'ar' with 'link' clause used in 'routine' function
[...]/array-properties-allocatable-declare-1-2.f90:6:0: Error: 'ar' with
'link' clause used in 'routine' function
[...]/array-properties-allocatable-declare-1-2.f90:6:0: Error: 'ar' with
'link' clause used in 'routine' function
..., which is different -- but not better.
WIP patch:
diff --git gcc/fortran/trans-common.c gcc/fortran/trans-common.c
index debdbd98ac0..5c2cd9b539e 100644
--- gcc/fortran/trans-common.c
+++ gcc/fortran/trans-common.c
@@ -452,16 +452,18 @@ build_common_decl (gfc_common_head *com, tree union_type,
bool is_init)
DECL_USER_ALIGN (decl) = 0;
GFC_DECL_COMMON_OR_EQUIV (decl) = 1;
gfc_set_decl_location (decl, &com->where);
if (com->threadprivate)
set_decl_tls_model (decl, decl_default_tls_model (decl));
+ /* Not possible to get an 'allocatable' here, no special handling
+ required. */
if (com->omp_declare_target_link)
DECL_ATTRIBUTES (decl)
= tree_cons (get_identifier ("omp declare target link"),
NULL_TREE, DECL_ATTRIBUTES (decl));
else if (com->omp_declare_target)
DECL_ATTRIBUTES (decl)
= tree_cons (get_identifier ("omp declare target"),
NULL_TREE, DECL_ATTRIBUTES (decl));
diff --git gcc/fortran/trans-decl.c gcc/fortran/trans-decl.c
index 8803525f6ae..029962f65c6 100644
--- gcc/fortran/trans-decl.c
+++ gcc/fortran/trans-decl.c
@@ -1429,18 +1429,26 @@ add_attributes_to_decl (symbol_attribute sym_attr, tree
list)
tree c = build_omp_clause (UNKNOWN_LOCATION, code);
OMP_CLAUSE_CHAIN (c) = clauses;
clauses = c;
tree dims = oacc_build_routine_dims (clauses);
list = oacc_replace_fn_attrib_attr (list, dims);
}
+ /* For an 'allocatable', it's the user's responsibility to 'allocate' it, and
+ create a device copy, so here, we handle it like the 'link' case. */
if (sym_attr.omp_declare_target_link
- || sym_attr.oacc_declare_link)
+ || sym_attr.oacc_declare_link
+ || ((sym_attr.omp_declare_target
+ || sym_attr.oacc_declare_create
+ || sym_attr.oacc_declare_copyin
+ || sym_attr.oacc_declare_deviceptr
+ || sym_attr.oacc_declare_device_resident)
+ && sym_attr.allocatable))
list = tree_cons (get_identifier ("omp declare target link"),
NULL_TREE, list);
else if (sym_attr.omp_declare_target
|| sym_attr.oacc_declare_create
|| sym_attr.oacc_declare_copyin
|| sym_attr.oacc_declare_deviceptr
|| sym_attr.oacc_declare_device_resident)
list = tree_cons (get_identifier ("omp declare target"),
@@ -6473,17 +6481,22 @@ find_module_oacc_declare_clauses (gfc_symbol *sym)
map_op = OMP_MAP_DEVICE_RESIDENT;
if (sym->attr.oacc_declare_create
|| sym->attr.oacc_declare_copyin
|| sym->attr.oacc_declare_deviceptr
|| sym->attr.oacc_declare_device_resident)
{
sym->attr.referenced = 1;
- add_clause (sym, map_op);
+ /* For an 'allocatable', it's the user's responsibility to 'allocate'
+ it, and create a device copy, so here, we handle it like the
+ 'link' case, and don't add it to the outer OpenACC 'data'
+ construct. */
+ if (!sym->attr.allocatable)
+ add_clause (sym, map_op);
}
}
}
void
finish_oacc_declare (gfc_namespace *ns, gfc_symbol *sym, bool block)
{
Grüße
Thomas
! { dg-do run }
module mod
implicit none
integer, parameter :: n = 40
integer, allocatable :: ar(:,:,:)
integer, parameter :: ar_rank = rank(ar)
integer :: ar_rank_v
integer :: ar_size_v
integer, dimension(ar_rank) :: ar_extent_v
integer, dimension(ar_rank) :: ar_shape_v
!$omp declare target (ar, ar_rank_v, ar_size_v, ar_extent_v, ar_shape_v)
end module mod
subroutine ar_properties
use mod
implicit none
!$omp declare target
integer :: i
ar_rank_v = rank(ar)
ar_size_v = size(ar)
do i = 1, ar_rank
ar_extent_v(i) = size(ar, i)
end do
ar_shape_v = shape(ar)
end subroutine ar_properties
program main
use mod
implicit none
allocate (ar(n,0:n+1,-1:n+2))
!$omp target enter data map(alloc:ar)
!$omp target map(from:ar_rank_v, ar_size_v, ar_extent_v, ar_shape_v)
call ar_properties
!$omp end target
!$omp target update from(ar_rank_v, ar_size_v, ar_extent_v, ar_shape_v)
print *, ar_rank_v
if (ar_rank_v /= rank(ar)) error stop
print *, ar_size_v
if (ar_size_v /= size(ar)) error stop
print *, ar_extent_v
if (any (ar_extent_v /= shape(ar))) error stop
print *, ar_shape_v
if (any (ar_shape_v /= shape(ar))) error stop
end program main
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