mirror of https://github.com/golang/go.git
49 lines
1.3 KiB
Go
49 lines
1.3 KiB
Go
// Copyright 2017 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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package cpu
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const CacheLinePadSize = 32
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// arm doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
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// These are initialized by archauxv() and should not be changed after they are
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// initialized.
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var HWCap uint
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var HWCap2 uint
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var Platform string
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// HWCAP/HWCAP2 bits. These are exposed by Linux and FreeBSD.
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const (
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hwcap_VFPv4 = 1 << 16
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hwcap_IDIVA = 1 << 17
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hwcap_LPAE = 1 << 20
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)
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func doinit() {
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options = []option{
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{Name: "vfpv4", Feature: &ARM.HasVFPv4},
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{Name: "idiva", Feature: &ARM.HasIDIVA},
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{Name: "v7atomics", Feature: &ARM.HasV7Atomics},
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}
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// HWCAP feature bits
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ARM.HasVFPv4 = isSet(HWCap, hwcap_VFPv4)
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ARM.HasIDIVA = isSet(HWCap, hwcap_IDIVA)
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// lpae is required to make the 64-bit instructions LDRD and STRD (and variants) atomic.
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// See ARMv7 manual section B1.6.
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// We also need at least a v7 chip, for the DMB instruction.
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ARM.HasV7Atomics = isSet(HWCap, hwcap_LPAE) && isV7(Platform)
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}
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func isSet(hwc uint, value uint) bool {
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return hwc&value != 0
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}
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func isV7(s string) bool {
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if s == "aarch64" {
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return true
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}
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return s >= "v7" // will be something like v5, v7, v8, v8l
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}
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