// Copyright 2014 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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// +build amd64 arm64 mips64 mips64le ppc64 ppc64le s390x wasm
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package runtime
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import "unsafe"
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const (
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// addrBits is the number of bits needed to represent a virtual address.
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//
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// See heapAddrBits for a table of address space sizes on
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// various architectures. 48 bits is enough for all
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// architectures except s390x.
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//
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// On AMD64, virtual addresses are 48-bit (or 57-bit) numbers sign extended to 64.
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// We shift the address left 16 to eliminate the sign extended part and make
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// room in the bottom for the count.
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//
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// On s390x, virtual addresses are 64-bit. There's not much we
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// can do about this, so we just hope that the kernel doesn't
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// get to really high addresses and panic if it does.
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addrBits = 48
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// In addition to the 16 bits taken from the top, we can take 3 from the
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// bottom, because node must be pointer-aligned, giving a total of 19 bits
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// of count.
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cntBits = 64 - addrBits + 3
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// On AIX, 64-bit addresses are split into 36-bit segment number and 28-bit
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// offset in segment. Segment numbers in the range 0x0A0000000-0x0AFFFFFFF(LSA)
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// are available for mmap.
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// We assume all lfnode addresses are from memory allocated with mmap.
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// We use one bit to distinguish between the two ranges.
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aixAddrBits = 57
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aixCntBits = 64 - aixAddrBits + 3
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)
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func lfstackPack(node *lfnode, cnt uintptr) uint64 {
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if GOARCH == "ppc64" && GOOS == "aix" {
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return uint64(uintptr(unsafe.Pointer(node)))<<(64-aixAddrBits) | uint64(cnt&(1<<aixCntBits-1))
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}
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return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1))
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}
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func lfstackUnpack(val uint64) *lfnode {
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if GOARCH == "amd64" {
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// amd64 systems can place the stack above the VA hole, so we need to sign extend
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// val before unpacking.
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return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3)))
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}
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if GOARCH == "ppc64" && GOOS == "aix" {
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return (*lfnode)(unsafe.Pointer(uintptr((val >> aixCntBits << 3) | 0xa<<56)))
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}
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return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
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}
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