1 // Copyright 2014 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package runtime 6 7 import "unsafe" 8 9 // On AMD64, virtual addresses are 48-bit numbers sign extended to 64. 10 // We shift the address left 16 to eliminate the sign extended part and make 11 // room in the bottom for the count. 12 // In addition to the 16 bits taken from the top, we can take 3 from the 13 // bottom, because node must be pointer-aligned, giving a total of 19 bits 14 // of count. 15 16 func lfstackPack(node *lfnode, cnt uintptr) uint64 { 17 return uint64(uintptr(unsafe.Pointer(node)))<<16 | uint64(cnt&(1<<19-1)) 18 } 19 20 func lfstackUnpack(val uint64) (node *lfnode, cnt uintptr) { 21 node = (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> 19 << 3))) 22 cnt = uintptr(val & (1<<19 - 1)) 23 return 24 } 25
