mirror of
https://github.com/make-42/xyosc
synced 2025-01-19 11:07:35 +01:00
273 lines
6.7 KiB
Go
273 lines
6.7 KiB
Go
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// SPDX-License-Identifier: Apache-2.0
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// SPDX-FileCopyrightText: 2024 The Ebitengine Authors
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package purego
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import (
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"math"
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"reflect"
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"unsafe"
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)
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func getStruct(outType reflect.Type, syscall syscall15Args) (v reflect.Value) {
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outSize := outType.Size()
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switch {
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case outSize == 0:
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return reflect.New(outType).Elem()
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case outSize <= 8:
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if isAllFloats(outType) {
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// 2 float32s or 1 float64s are return in the float register
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return reflect.NewAt(outType, unsafe.Pointer(&struct{ a uintptr }{syscall.f1})).Elem()
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}
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// up to 8 bytes is returned in RAX
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return reflect.NewAt(outType, unsafe.Pointer(&struct{ a uintptr }{syscall.a1})).Elem()
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case outSize <= 16:
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r1, r2 := syscall.a1, syscall.a2
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if isAllFloats(outType) {
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r1 = syscall.f1
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r2 = syscall.f2
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} else {
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// check first 8 bytes if it's floats
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hasFirstFloat := false
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f1 := outType.Field(0).Type
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if f1.Kind() == reflect.Float64 || f1.Kind() == reflect.Float32 && outType.Field(1).Type.Kind() == reflect.Float32 {
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r1 = syscall.f1
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hasFirstFloat = true
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}
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// find index of the field that starts the second 8 bytes
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var i int
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for i = 0; i < outType.NumField(); i++ {
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if outType.Field(i).Offset == 8 {
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break
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}
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}
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// check last 8 bytes if they are floats
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f1 = outType.Field(i).Type
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if f1.Kind() == reflect.Float64 || f1.Kind() == reflect.Float32 && i+1 == outType.NumField() {
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r2 = syscall.f1
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} else if hasFirstFloat {
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// if the first field was a float then that means the second integer field
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// comes from the first integer register
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r2 = syscall.a1
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}
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}
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return reflect.NewAt(outType, unsafe.Pointer(&struct{ a, b uintptr }{r1, r2})).Elem()
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default:
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// create struct from the Go pointer created above
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// weird pointer dereference to circumvent go vet
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return reflect.NewAt(outType, *(*unsafe.Pointer)(unsafe.Pointer(&syscall.a1))).Elem()
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}
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}
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func isAllFloats(ty reflect.Type) bool {
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for i := 0; i < ty.NumField(); i++ {
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f := ty.Field(i)
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switch f.Type.Kind() {
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case reflect.Float64, reflect.Float32:
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default:
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return false
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}
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}
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return true
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}
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// https://refspecs.linuxbase.org/elf/x86_64-abi-0.99.pdf
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// https://gitlab.com/x86-psABIs/x86-64-ABI
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// Class determines where the 8 byte value goes.
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// Higher value classes win over lower value classes
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const (
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_NO_CLASS = 0b0000
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_SSE = 0b0001
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_X87 = 0b0011 // long double not used in Go
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_INTEGER = 0b0111
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_MEMORY = 0b1111
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)
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func addStruct(v reflect.Value, numInts, numFloats, numStack *int, addInt, addFloat, addStack func(uintptr), keepAlive []interface{}) []interface{} {
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if v.Type().Size() == 0 {
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return keepAlive
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}
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// if greater than 64 bytes place on stack
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if v.Type().Size() > 8*8 {
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placeStack(v, addStack)
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return keepAlive
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}
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var (
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savedNumFloats = *numFloats
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savedNumInts = *numInts
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savedNumStack = *numStack
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)
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placeOnStack := postMerger(v.Type()) || !tryPlaceRegister(v, addFloat, addInt)
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if placeOnStack {
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// reset any values placed in registers
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*numFloats = savedNumFloats
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*numInts = savedNumInts
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*numStack = savedNumStack
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placeStack(v, addStack)
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}
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return keepAlive
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}
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func postMerger(t reflect.Type) bool {
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// (c) If the size of the aggregate exceeds two eightbytes and the first eight- byte isn’t SSE or any other
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// eightbyte isn’t SSEUP, the whole argument is passed in memory.
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if t.Kind() != reflect.Struct {
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return false
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}
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if t.Size() <= 2*8 {
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return false
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}
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first := getFirst(t).Kind()
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if first != reflect.Float32 && first != reflect.Float64 {
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return false
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}
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return true
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}
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func getFirst(t reflect.Type) reflect.Type {
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first := t.Field(0).Type
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if first.Kind() == reflect.Struct {
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return getFirst(first)
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}
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return first
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}
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func tryPlaceRegister(v reflect.Value, addFloat func(uintptr), addInt func(uintptr)) (ok bool) {
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ok = true
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var val uint64
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var shift byte // # of bits to shift
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var flushed bool
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class := _NO_CLASS
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flushIfNeeded := func() {
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if flushed {
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return
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}
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flushed = true
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if class == _SSE {
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addFloat(uintptr(val))
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} else {
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addInt(uintptr(val))
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}
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val = 0
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shift = 0
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class = _NO_CLASS
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}
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var place func(v reflect.Value)
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place = func(v reflect.Value) {
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var numFields int
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if v.Kind() == reflect.Struct {
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numFields = v.Type().NumField()
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} else {
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numFields = v.Type().Len()
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}
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for i := 0; i < numFields; i++ {
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flushed = false
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var f reflect.Value
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if v.Kind() == reflect.Struct {
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f = v.Field(i)
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} else {
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f = v.Index(i)
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}
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switch f.Kind() {
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case reflect.Struct:
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place(f)
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case reflect.Bool:
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if f.Bool() {
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val |= 1
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}
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shift += 8
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class |= _INTEGER
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case reflect.Pointer:
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ok = false
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return
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case reflect.Int8:
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val |= uint64(f.Int()&0xFF) << shift
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shift += 8
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class |= _INTEGER
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case reflect.Int16:
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val |= uint64(f.Int()&0xFFFF) << shift
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shift += 16
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class |= _INTEGER
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case reflect.Int32:
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val |= uint64(f.Int()&0xFFFF_FFFF) << shift
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shift += 32
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class |= _INTEGER
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case reflect.Int64:
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val = uint64(f.Int())
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shift = 64
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class = _INTEGER
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case reflect.Uint8:
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val |= f.Uint() << shift
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shift += 8
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class |= _INTEGER
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case reflect.Uint16:
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val |= f.Uint() << shift
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shift += 16
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class |= _INTEGER
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case reflect.Uint32:
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val |= f.Uint() << shift
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shift += 32
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class |= _INTEGER
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case reflect.Uint64:
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val = f.Uint()
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shift = 64
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class = _INTEGER
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case reflect.Float32:
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val |= uint64(math.Float32bits(float32(f.Float()))) << shift
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shift += 32
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class |= _SSE
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case reflect.Float64:
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if v.Type().Size() > 16 {
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ok = false
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return
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}
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val = uint64(math.Float64bits(f.Float()))
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shift = 64
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class = _SSE
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case reflect.Array:
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place(f)
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default:
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panic("purego: unsupported kind " + f.Kind().String())
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}
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if shift == 64 {
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flushIfNeeded()
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} else if shift > 64 {
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// Should never happen, but may if we forget to reset shift after flush (or forget to flush),
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// better fall apart here, than corrupt arguments.
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panic("purego: tryPlaceRegisters shift > 64")
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}
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}
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}
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place(v)
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flushIfNeeded()
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return ok
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}
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func placeStack(v reflect.Value, addStack func(uintptr)) {
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for i := 0; i < v.Type().NumField(); i++ {
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f := v.Field(i)
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switch f.Kind() {
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case reflect.Pointer:
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addStack(f.Pointer())
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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addStack(uintptr(f.Int()))
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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addStack(uintptr(f.Uint()))
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case reflect.Float32:
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addStack(uintptr(math.Float32bits(float32(f.Float()))))
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case reflect.Float64:
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addStack(uintptr(math.Float64bits(f.Float())))
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case reflect.Struct:
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placeStack(f, addStack)
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default:
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panic("purego: unsupported kind " + f.Kind().String())
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}
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}
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}
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