mirror of git://gcc.gnu.org/git/gcc.git
51 lines
1.8 KiB
Go
51 lines
1.8 KiB
Go
// 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 ignore
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// +build amd64 arm64 mips64 mips64le ppc64 ppc64le s390x
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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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// In Linux the user address space for each architecture is limited as
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// follows (taken from the processor.h file for the architecture):
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//
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// Architecture Name Maximum Value (exclusive)
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// ---------------------------------------------------------------------
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// arm64 TASK_SIZE_64 Depends on configuration.
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// ppc64{,le} TASK_SIZE_USER64 0x400000000000UL (46 bit addresses)
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// mips64{,le} TASK_SIZE64 0x010000000000UL (40 bit addresses)
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// s390x TASK_SIZE 0x020000000000UL (41 bit addresses)
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//
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// These values may increase over time.
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//
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// On AMD64, virtual addresses are 48-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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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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)
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func lfstackPack(node *lfnode, cnt uintptr) uint64 {
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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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return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
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}
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