mirror of git://gcc.gnu.org/git/gcc.git
51 lines
1.3 KiB
Go
51 lines
1.3 KiB
Go
// Copyright 2012 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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// Lock-free stack.
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// Initialize head to 0, compare with 0 to test for emptiness.
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// The stack does not keep pointers to nodes,
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// so they can be garbage collected if there are no other pointers to nodes.
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// The following code runs only in non-preemptible contexts.
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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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// Temporary for C code to call:
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//go:linkname lfstackpush runtime.lfstackpush
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//go:linkname lfstackpop runtime.lfstackpop
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func lfstackpush(head *uint64, node *lfnode) {
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node.pushcnt++
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new := lfstackPack(node, node.pushcnt)
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if node1 := lfstackUnpack(new); node1 != node {
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print("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
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throw("lfstackpush")
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}
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for {
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old := atomic.Load64(head)
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node.next = old
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if atomic.Cas64(head, old, new) {
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break
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}
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}
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}
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func lfstackpop(head *uint64) unsafe.Pointer {
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for {
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old := atomic.Load64(head)
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if old == 0 {
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return nil
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}
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node := lfstackUnpack(old)
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next := atomic.Load64(&node.next)
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if atomic.Cas64(head, old, next) {
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return unsafe.Pointer(node)
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}
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}
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}
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