Add Python bindings for SYCL IPC memory via dpctl

[zxue2]

Add inter-process communication (IPC) support for SYCL USM memory, enabling zero-copy GPU memory sharing across processes. It wraps sycl::ext::oneapi::experimental::ipc::memory (get/open/close/put).

C API (libsyclinterface):

• dpctl_sycl_ipc_memory_interface.h: declares DPCTLIPCMem_GetHandle, DPCTLIPCMem_OpenHandle, DPCTLIPCMem_CloseHandle, DPCTLIPCMem_FreeHandleData
• dpctl_sycl_ipc_memory_interface.cpp: implements the C API by calling the SYCL experimental ipc::memory functions; auto-discovered by CMake.

Cython declarations:

• _backend.pxd: extern block for the 4 new C functions

Python subpackage (dpctl.ipc):

• IPCMemoryHandle: Cython extension class wrapping IPC memory export/import init(usm_memory): calls get() + put(), stores handle as bytes to_bytes(): serializable payload for cross-process transport open(handle_bytes, device, nbytes): returns MemoryUSMDevice close_mapping(usm_memory): explicitly closes an IPC mapping

Test In Docker (oneAPI 2026.0 installed):

python -c "
import dpctl
from dpctl.memory import MemoryUSMDevice
from dpctl.ipc import IPCMemoryHandle
d = dpctl.SyclDevice('level_zero:gpu')
q = dpctl.SyclQueue(d)
mem = MemoryUSMDevice(4096, queue=q)
h = IPCMemoryHandle(mem)
raw = h.to_bytes()
print(f'IPC handle: {len(raw)} bytes')
mem2 = IPCMemoryHandle.open(raw, d, nbytes=4096)
print(f'Opened: {mem2.nbytes} bytes on {mem2.sycl_device.name}')
IPCMemoryHandle.close_mapping(mem2)
print('close OK')
"

IPC handle: 120 bytes
Opened: 4096 bytes on Intel(R) Arc(TM) Pro B60 Graphics
close OK

[coveralls]

coverage: 75.504% (-0.2%) from 75.677% — zxue2:enable_ipc_mem into IntelPython:master

[antonwolfy]

Is the class meant to be public? Then it seems missed in dpctl/memory/__init__.py and __all__ above/

[antonwolfy]

Suggested change

	Class representing emory object backed by an IPC-mapped USM device pointer.
	Class representing memory object backed by an IPC-mapped USM device pointer.

[antonwolfy]

The comment seems inaccurate, there is no put call inside DPCTLIPCMem_GetHandle

[antonwolfy]

If the construction fails due to some reason, there will be __dealloc__ called, which will do DPCTLIPCMem_CloseHandle(...), because we already did: base._memory_ptr = USMRef.

From other side. since the construction fails at that point, there will be exception raised, and so there will be the 2nd call of DPCTLIPCMem_CloseHandle(...) at line 1214, during the exception handling.