https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113216
Bug ID: 113216
Summary: [OpenMP] Improve omp_target_is_accessible
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: openmp
Severity: normal
Priority: P3
Component: libgomp
Assignee: unassigned at gcc dot gnu.org
Reporter: burnus at gcc dot gnu.org
CC: jakub at gcc dot gnu.org
Target Milestone: ---
For omp_target_is_accessible + unified address:
* it is not 100% correct to assume that any address is accessible on the host,
it might be a device-only address
(For handling NULL, see also PR 113213)
Likewise for the nonhost device:
* memory might be accessible even if only unified address
* * *
The host case is a bit trickier as no generic documentation seems to be
available albeit some ranges like 0x7F...... seem to denote device addresses +
a superset has to be formed.
* * *
For the device side, an API function might be available to check for it.
* *
In case of nvptx / CUDA, the following function seems to be suitable:
CUresult cuMemGetAccess ( unsigned long long* flags,
const CUmemLocation* location, CUdeviceptr ptr )
checking for flags == CU_MEM_ACCESS_FLAGS_PROT_READWRITE, if I understand it
correctly.
typedef enum CUmemAccess_flags_enum {
CU_MEM_ACCESS_FLAGS_PROT_NONE = 0x0, /**< Default, make the address range
not accessible */
CU_MEM_ACCESS_FLAGS_PROT_READ = 0x1, /**< Make the address range read
accessible */
CU_MEM_ACCESS_FLAGS_PROT_READWRITE = 0x3, /**< Make the address range
read-write accessible */
CU_MEM_ACCESS_FLAGS_PROT_MAX = 0x7FFFFFFF
} CUmemAccess_flags;
* *
In case of HSA/ROCm, I bet there is also some function.
For instance, hipPointerGetAttribute{,s} + hipDrvPointerGetAttributes permit to
query some pointer data.
