blob: 4ce7d2a0988273bca1eebe2010f545696de6dafb [file] [log] [blame]
// 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)))
}