[c10d][xccl2] Add backend-agnostic TorchComms helpers for xccl2 - #5
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xccl2 needs three of the backend-agnostic helpers that nccl2 uses:
TracingGuard (profiler and flight-recorder records), Logging (TC_LOG) and
Batch (BatchSendRecv). All three were upstreamed from torchcomms'
comms/torchcomms/utils/ and contain no backend-specific code, but they
currently live under c10d/nccl2/ behind USE_C10D_NCCL and compile into
libtorch_cuda. An XPU-only build never compiles them, so xccl2 cannot link
against them.
Vendor a copy under c10d/xccl2/ in namespace c10d::xccl2. The files are
identical to the nccl2 originals apart from the namespace, the compile guard
(USE_C10D_XCCL) and the include paths. nccl2's Utils.{hpp,cpp} is deliberately
not copied: xccl2 takes its rank and size from the c10d Store rather than from
query_ranksize(), so none of its entry points are reachable here.
This duplicates the helpers rather than relocating the originals, so that
landing xccl2 requires no changes to nccl2. Consolidating the copies into a
shared directory is left to a follow-up that can be reviewed on its own merits,
once both backends are in tree.
No functional change to any existing backend.
This was referenced Aug 25, 2026
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Stack (bottom → top)
xccl2/01-foundationxccl2/02-apixccl2/03-workxccl2/04-engine-declxccl2/05-engine-implxccl2/06-backend-surfacexccl2/07-build-wiringxccl2/08-testsxccl2/09-integration-testsEach PR is exactly one commit and targets the one below it. Review bottom-up.
xccl2 needs three of the backend-agnostic helpers that nccl2 uses:
TracingGuard (profiler and flight-recorder records), Logging (TC_LOG) and
Batch (BatchSendRecv). All three were upstreamed from torchcomms'
comms/torchcomms/utils/ and contain no backend-specific code, but they
currently live under c10d/nccl2/ behind USE_C10D_NCCL and compile into
libtorch_cuda. An XPU-only build never compiles them, so xccl2 cannot link
against them.
Vendor a copy under c10d/xccl2/ in namespace c10d::xccl2. The files are
identical to the nccl2 originals apart from the namespace, the compile guard
(USE_C10D_XCCL) and the include paths. nccl2's Utils.{hpp,cpp} is deliberately
not copied: xccl2 takes its rank and size from the c10d Store rather than from
query_ranksize(), so none of its entry points are reachable here.
This duplicates the helpers rather than relocating the originals, so that
landing xccl2 requires no changes to nccl2. Consolidating the copies into a
shared directory is left to a follow-up that can be reviewed on its own merits,
once both backends are in tree.
No functional change to any existing backend.