https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82864
Bug ID: 82864
Summary: Stop using GOMP_OFFLOAD_openacc_async_set_async
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: libgomp
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
CC: jakub at gcc dot gnu.org
Target Milestone: ---
When grepping for async_set_async_func in libgomp sources, we see a pattern
emerging:
...
libgomp.h:917: __typeof (GOMP_OFFLOAD_openacc_async_set_async)
*async_set_async_func;
oacc-host.c:246: .async_set_async_func = host_openacc_async_set_async,
oacc-init.c:432: acc_dev->openacc.async_set_async_func (acc_async_sync);
oacc-parallel.c:156: acc_dev->openacc.async_set_async_func (async);
oacc-parallel.c:191: acc_dev->openacc.async_set_async_func (acc_async_sync);
oacc-parallel.c:289: acc_dev->openacc.async_set_async_func (async);
oacc-parallel.c:395: acc_dev->openacc.async_set_async_func (acc_async_sync);
oacc-parallel.c:448: acc_dev->openacc.async_set_async_func (async);
oacc-parallel.c:474: acc_dev->openacc.async_set_async_func (acc_async_sync);
oacc-plugin.c:39: devicep->openacc.async_set_async_func (async);
oacc-plugin.c:41: devicep->openacc.async_set_async_func (acc_async_sync);
...
F.i., lets look at the last pair:
...
void
GOMP_PLUGIN_async_unmap_vars (void *ptr, int async)
{
struct target_mem_desc *tgt = ptr;
struct gomp_device_descr *devicep = tgt->device_descr;
devicep->openacc.async_set_async_func (async);
gomp_unmap_vars (tgt, true);
devicep->openacc.async_set_async_func (acc_async_sync);
}
...
This is an example of implicit parameter passing: instead of passing the async
argument to gomp_unmap_vars and beyond, we tell the target plugin to store the
async argument for the time being as attribute of the current thread, and let
the target plugin use that argument where appropriate while executing
gomp_unmap_vars.
It is a bit odd though that we're asking the target plugin to keep this state.
I think it would be more logical to have the attribute as a part of struct
goacc_thread, and extend the plugin interface with the async argument where
necessary. So f.i. alongside the existing
extern bool GOMP_OFFLOAD_dev2host (int, void *, const void *, size_t);
we add an async variant
extern bool GOMP_OFFLOAD_dev2host_async (int, void *, const void *, size_t,
int async);
and use that instead if the target plugin provides it.
