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[stdlib] Don't use aarch64 hint for arm targets in Synchronization #74258

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Merged
merged 1 commit into from
Jun 10, 2024
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[stdlib] Don't use aarch64 hint for arm targets in Synchronization #74258

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20 changes: 20 additions & 0 deletions stdlib/public/Synchronization/Mutex/SpinLoopHint.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@ var _tries: Int {
100
}

#if arch(arm)

// The following are acceptable operands to the aarch64 hint intrinsic from
// 'llvm-project/llvm/lib/Target/ARM/ARMInstrInfo.td':
//
Expand All @@ -28,9 +30,27 @@ var _tries: Int {
// `sevl` = 5
//
// There are others, but for the sake of spin loops, we only care about 'wfe'.
@_extern(c, "llvm.arm.hint")
func _hint(_: UInt32)

#else

// The following are acceptable operands to the aarch64 hint intrinsic from
// 'llvm-project/llvm/lib/Target/AArch64/AArch64InstrInfo.td':
//
// `nop` = 0
// `yield` = 1
// `wfe` = 2
// `wfi` = 3
// `sev` = 4
// `sevl` = 5
//
// There are others, but for the sake of spin loops, we only care about 'wfe'.
@_extern(c, "llvm.aarch64.hint")
func _hint(_: UInt32)

#endif

@inline(__always)
func _wfe() {
_hint(2)
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