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[Synchronization] Fix wasm atomic intrinsic declarations #74171

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Merged
merged 2 commits into from
Jun 6, 2024
Merged

[Synchronization] Fix wasm atomic intrinsic declarations #74171

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[Synchronization] Fix wasm atomic intrinsic declarations
kateinoigakukun Jun 6, 2024
2dbbbcf
[Synchronization] Skip atomic operations in single-threaded mode on W…
kateinoigakukun Jun 6, 2024
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14 changes: 9 additions & 5 deletions stdlib/public/Synchronization/Mutex/WasmImpl.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -13,30 +13,34 @@
// Note: All atomic accesses on WASM are sequentially consistent regardless of
// what ordering we tell LLVM to use.

@_extern(c, "llvm.wasm32.memory.atomic.wait32")
@_extern(c, "llvm.wasm.memory.atomic.wait32")
internal func _swift_stdlib_wait(
on: UnsafePointer<UInt32>,
expected: UInt32,
timeout: Int64
) -> UInt32

@_extern(c, "llvm.wasm32.memory.atomic.notify")
internal func _swift_stdlib_wake(on: UnsafePointer<UInt32>, count: UInt32)
@_extern(c, "llvm.wasm.memory.atomic.notify")
internal func _swift_stdlib_wake(on: UnsafePointer<UInt32>, count: UInt32) -> UInt32

extension Atomic where Value == _MutexHandle.State {
internal borrowing func _wait(expected: _MutexHandle.State) {
_swift_stdlib_wait(
#if _runtime(_multithreaded)
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I think we should generally make Mutex unavailable when the runtime isn't multithreaded

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although I guess it doesn't really matter because Mutex can always acquire in the single threaded context and needing to call wait or notify should ever occur so this is probably fine.

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Ah, it might be better to have a separate noop implementations for single threaded targets instead of just skipping wait/notify operations.

_ = _swift_stdlib_wait(
on: .init(_rawAddress),
expected: expected.rawValue,

// A timeout of < 0 means indefinitely.
timeout: -1
)
#endif
}

internal borrowing func _wake() {
#if _runtime(_multithreaded)
// Only wake up 1 thread
_swift_stdlib_wake(on: .init(_rawAddress), count: 1)
_ = _swift_stdlib_wake(on: .init(_rawAddress), count: 1)
#endif
}
}

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