80 lines
2.4 KiB
Go
80 lines
2.4 KiB
Go
//go:build amd64 && !tinygo
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package platform
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// CpuFeatures exposes the capabilities for this CPU, queried via the Has, HasExtra methods.
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var CpuFeatures = loadCpuFeatureFlags()
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// cpuFeatureFlags implements CpuFeatureFlags interface.
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type cpuFeatureFlags struct {
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flags uint64
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extraFlags uint64
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}
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// cpuid exposes the CPUID instruction to the Go layer (https://www.amd.com/system/files/TechDocs/25481.pdf)
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// implemented in impl_amd64.s
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func cpuid(arg1, arg2 uint32) (eax, ebx, ecx, edx uint32)
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// cpuidAsBitmap combines the result of invoking cpuid to uint64 bitmap.
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func cpuidAsBitmap(arg1, arg2 uint32) uint64 {
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_ /* eax */, _ /* ebx */, ecx, edx := cpuid(arg1, arg2)
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return (uint64(edx) << 32) | uint64(ecx)
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}
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// loadStandardRange load flags from the standard range, panics otherwise.
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func loadStandardRange(id uint32) uint64 {
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// ensure that the id is in the valid range, returned by cpuid(0,0)
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maxRange, _, _, _ := cpuid(0, 0)
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if id > maxRange {
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panic("cannot query standard CPU flags")
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}
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return cpuidAsBitmap(id, 0)
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}
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// loadStandardRange load flags from the extended range, panics otherwise.
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func loadExtendedRange(id uint32) uint64 {
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// ensure that the id is in the valid range, returned by cpuid(0x80000000,0)
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maxRange, _, _, _ := cpuid(0x80000000, 0)
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if id > maxRange {
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panic("cannot query extended CPU flags")
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}
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return cpuidAsBitmap(id, 0)
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}
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func loadCpuFeatureFlags() CpuFeatureFlags {
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return &cpuFeatureFlags{
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flags: loadStandardRange(1),
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extraFlags: loadExtendedRange(0x80000001),
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}
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}
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// Has implements the same method on the CpuFeatureFlags interface.
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func (f *cpuFeatureFlags) Has(cpuFeature CpuFeature) bool {
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return (f.flags & uint64(cpuFeature)) != 0
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}
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// HasExtra implements the same method on the CpuFeatureFlags interface.
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func (f *cpuFeatureFlags) HasExtra(cpuFeature CpuFeature) bool {
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return (f.extraFlags & uint64(cpuFeature)) != 0
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}
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// Raw implements the same method on the CpuFeatureFlags interface.
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func (f *cpuFeatureFlags) Raw() uint64 {
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// Below, we only set the first 4 bits for the features we care about,
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// instead of setting all the unnecessary bits obtained from the CPUID instruction.
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var ret uint64
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if f.Has(CpuFeatureAmd64SSE3) {
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ret = 1 << 0
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}
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if f.Has(CpuFeatureAmd64SSE4_1) {
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ret |= 1 << 1
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}
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if f.Has(CpuFeatureAmd64SSE4_2) {
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ret |= 1 << 2
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}
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if f.HasExtra(CpuExtraFeatureAmd64ABM) {
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ret |= 1 << 3
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}
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return ret
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}
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