| // Copyright 2014 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| // +build amd64 arm64 mips64 mips64le ppc64 ppc64le s390x wasm | |
| package runtime | |
| import "unsafe" | |
| const ( | |
| // addrBits is the number of bits needed to represent a virtual address. | |
| // | |
| // See heapAddrBits for a table of address space sizes on | |
| // various architectures. 48 bits is enough for all | |
| // architectures except s390x. | |
| // | |
| // On AMD64, virtual addresses are 48-bit (or 57-bit) numbers sign extended to 64. | |
| // We shift the address left 16 to eliminate the sign extended part and make | |
| // room in the bottom for the count. | |
| // | |
| // On s390x, virtual addresses are 64-bit. There's not much we | |
| // can do about this, so we just hope that the kernel doesn't | |
| // get to really high addresses and panic if it does. | |
| addrBits = 48 | |
| // In addition to the 16 bits taken from the top, we can take 3 from the | |
| // bottom, because node must be pointer-aligned, giving a total of 19 bits | |
| // of count. | |
| cntBits = 64 - addrBits + 3 | |
| ) | |
| func lfstackPack(node *lfnode, cnt uintptr) uint64 { | |
| return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1)) | |
| } | |
| func lfstackUnpack(val uint64) *lfnode { | |
| if GOARCH == "amd64" { | |
| // amd64 systems can place the stack above the VA hole, so we need to sign extend | |
| // val before unpacking. | |
| return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3))) | |
| } | |
| return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3))) | |
| } |