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maleadt
added this pull request to stack #29
September 25, 2026 13:30
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September 25, 2026 15:11
Back-ends need the workgroup, device, ... scopes, and use the internal LLVMSyncScope type to get them. Provide `subgroup`, `workgroup`, `device` and `system` (the existing `none`) as constants, and `SyncScope(name)` for target-specific scopes such as `:agent`.
The IR for Ptr atomics that can't use the intrinsics was built for each scope singleton when defining the methods. Build it in @generated helpers that take the scope as a type parameter instead, so that other scopes can be supported without enumerating them. No functional change.
Atomics on Ptr only accepted the `none` and `singlethread` scopes, while LLVMPtr accepts any. Define the llvmcall-based methods for every LLVMSyncScope, so that the canonical scopes and target-specific ones like `SyncScope(:agent)` work on Ptr too. The system scope keeps using the intrinsics where possible.
Fences only accepted the `none` and `singlethread` scopes, so back-ends had to add methods for others (AMDGPU does). Emit them for any LLVMSyncScope. This also fixes `fence(monotonic, singlethread)` and `fence(unordered, singlethread)`, which emitted IR that failed to parse: like for the system scope, the former is now a no-op and the latter throws a ConcurrencyViolationError.
Nothing is exported, so mark the functions, orderings and scopes as `public` on Julia 1.11 and later, to distinguish them from the internals that back-ends currently reach into.
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Stack: #28 → #25 → this PR → #30.
GPU back-ends need scopes such as
workgroupanddevice, but UnsafeAtomics only exposednoneandsinglethread. As a result, Metal.jl, SPIRVIntrinsics and AMDGPU.jl construct the internalUnsafeAtomics.Internal.LLVMSyncScope{name}()type, and AMDGPU.jl piratesUnsafeAtomics.fencebecause fences only accepted those two scopes. OnlyLLVMPtrhonored other scopes at all.This PR adds a public set of scopes:
singlethread,subgroup,workgroup,deviceandsystem(an alias ofnone), plusSyncScope(:name)for target-specific scopes such as:agent. All operations on both pointer types, includingfence, accept any of them. The change is purely additive.Once released, back-ends can stop using the internal type, and AMDGPU.jl can remove its
fencemethods.