86ff185365
PR go/84215
runtime, sync/atomic: use write barrier for atomic pointer functions
This copies atomic_pointer.go from 1.10rc2. It was omitted during the
transition of the runtime from C to Go, and I forgot about it.
This may help with https://gcc.gnu.org/PR84215.
Reviewed-on: https://go-review.googlesource.com/93197
From-SVN: r257599
70 lines
2.9 KiB
Go
70 lines
2.9 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"runtime/internal/atomic"
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"unsafe"
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)
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// These functions cannot have go:noescape annotations,
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// because while ptr does not escape, new does.
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// If new is marked as not escaping, the compiler will make incorrect
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// escape analysis decisions about the pointer value being stored.
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// Instead, these are wrappers around the actual atomics (casp1 and so on)
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// that use noescape to convey which arguments do not escape.
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// atomicstorep performs *ptr = new atomically and invokes a write barrier.
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//
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//go:nosplit
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func atomicstorep(ptr unsafe.Pointer, new unsafe.Pointer) {
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writebarrierptr_prewrite((*uintptr)(ptr), uintptr(new))
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atomic.StorepNoWB(noescape(ptr), new)
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}
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//go:nosplit
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func casp(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
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// The write barrier is only necessary if the CAS succeeds,
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// but since it needs to happen before the write becomes
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// public, we have to do it conservatively all the time.
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writebarrierptr_prewrite((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
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return atomic.Casp1((*unsafe.Pointer)(noescape(unsafe.Pointer(ptr))), noescape(old), new)
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}
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// Like above, but implement in terms of sync/atomic's uintptr operations.
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// We cannot just call the runtime routines, because the race detector expects
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// to be able to intercept the sync/atomic forms but not the runtime forms.
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//go:linkname sync_atomic_StoreUintptr sync_atomic.StoreUintptr
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func sync_atomic_StoreUintptr(ptr *uintptr, new uintptr)
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//go:linkname sync_atomic_StorePointer sync_atomic.StorePointer
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//go:nosplit
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func sync_atomic_StorePointer(ptr *unsafe.Pointer, new unsafe.Pointer) {
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writebarrierptr_prewrite((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
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sync_atomic_StoreUintptr((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
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}
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//go:linkname sync_atomic_SwapUintptr sync_atomic.SwapUintptr
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func sync_atomic_SwapUintptr(ptr *uintptr, new uintptr) uintptr
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//go:linkname sync_atomic_SwapPointer sync_atomic.SwapPointer
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//go:nosplit
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func sync_atomic_SwapPointer(ptr *unsafe.Pointer, new unsafe.Pointer) unsafe.Pointer {
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writebarrierptr_prewrite((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
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old := unsafe.Pointer(sync_atomic_SwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(new)))
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return old
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}
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//go:linkname sync_atomic_CompareAndSwapUintptr sync_atomic.CompareAndSwapUintptr
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func sync_atomic_CompareAndSwapUintptr(ptr *uintptr, old, new uintptr) bool
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//go:linkname sync_atomic_CompareAndSwapPointer sync_atomic.CompareAndSwapPointer
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//go:nosplit
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func sync_atomic_CompareAndSwapPointer(ptr *unsafe.Pointer, old, new unsafe.Pointer) bool {
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writebarrierptr_prewrite((*uintptr)(unsafe.Pointer(ptr)), uintptr(new))
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return sync_atomic_CompareAndSwapUintptr((*uintptr)(noescape(unsafe.Pointer(ptr))), uintptr(old), uintptr(new))
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}
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