| // 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 |

| |

| // On AIX, 64-bit addresses are split into 36-bit segment number and 28-bit |

| // offset in segment. Segment numbers in the range 0x0A0000000-0x0AFFFFFFF(LSA) |

| // are available for mmap. |

| // We assume all lfnode addresses are from memory allocated with mmap. |

| // We use one bit to distinguish between the two ranges. |

| aixAddrBits = 57 |

| aixCntBits = 64 - aixAddrBits + 3 |

| ) |

| |

| func lfstackPack(node *lfnode, cnt uintptr) uint64 { |

| if GOARCH == "ppc64" && GOOS == "aix" { |

| return uint64(uintptr(unsafe.Pointer(node)))<<(64-aixAddrBits) | uint64(cnt&(1<<aixCntBits-1)) |

| } |

| 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))) |

| } |

| if GOARCH == "ppc64" && GOOS == "aix" { |

| return (*lfnode)(unsafe.Pointer(uintptr((val >> aixCntBits << 3) | 0xa<<56))) |

| } |

| return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3))) |

| } |