GoToSocial/vendor/modernc.org/cc/v3/abi.go

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// Copyright 2019 The CC Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package cc // import "modernc.org/cc/v3"
import (
"encoding/binary"
"fmt"
"math"
"os"
"runtime"
"lukechampine.com/uint128"
"modernc.org/mathutil"
)
var (
idAligned = String("aligned")
idGCCStruct = String("gcc_struct")
idMSStruct = String("ms_struct")
idPacked = String("packed")
complexTypedefs = map[StringID]Kind{
dict.sid("__COMPLEX_CHAR_TYPE__"): ComplexChar,
dict.sid("__COMPLEX_DOUBLE_TYPE__"): ComplexDouble,
dict.sid("__COMPLEX_FLOAT_TYPE__"): ComplexFloat,
dict.sid("__COMPLEX_INT_TYPE__"): ComplexInt,
dict.sid("__COMPLEX_LONG_TYPE__"): ComplexLong,
dict.sid("__COMPLEX_LONG_DOUBLE_TYPE__"): ComplexLongDouble,
dict.sid("__COMPLEX_LONG_LONG_TYPE__"): ComplexLongLong,
dict.sid("__COMPLEX_SHORT_TYPE__"): ComplexShort,
dict.sid("__COMPLEX_UNSIGNED_TYPE__"): ComplexUInt,
dict.sid("__COMPLEX_LONG_UNSIGNED_TYPE__"): ComplexULong,
dict.sid("__COMPLEX_LONG_LONG_UNSIGNED_TYPE__"): ComplexULongLong,
dict.sid("__COMPLEX_SHORT_UNSIGNED_TYPE__"): ComplexUShort,
}
)
// NewABI creates an ABI for a given OS and architecture. The OS and architecture values are the same as used in Go.
// The ABI type map may miss advanced types like complex numbers, etc. If the os/arch pair is not recognized, a
// *ErrUnsupportedOSArch is returned.
func NewABI(os, arch string) (ABI, error) {
order, ok := abiByteOrders[arch]
if !ok {
return ABI{}, fmt.Errorf("unsupported arch: %s", arch)
}
types, ok := abiTypes[[2]string{os, arch}]
if !ok {
return ABI{}, fmt.Errorf("unsupported os/arch pair: %s-%s", os, arch)
}
abi := ABI{
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ByteOrder: order,
Types: make(map[Kind]ABIType, len(types)),
SignedChar: abiSignedChar[[2]string{os, arch}],
os: os,
arch: arch,
}
// copy the map, so it can be modified by user
for k, v := range types {
abi.Types[k] = v
}
return abi, nil
}
// NewABIFromEnv uses GOOS and GOARCH values to create a corresponding ABI.
// If those environment variables are not set, an OS/arch of a Go runtime is used.
// It returns a *ErrUnsupportedOSArch if OS/arch pair is not supported.
func NewABIFromEnv() (ABI, error) {
osv := os.Getenv("GOOS")
if osv == "" {
osv = runtime.GOOS
}
arch := os.Getenv("GOARCH")
if arch == "" {
arch = runtime.GOARCH
}
return NewABI(osv, arch)
}
// ABIType describes properties of a non-aggregate type.
type ABIType struct {
Size uintptr
Align int
FieldAlign int
}
// ABI describes selected parts of the Application Binary Interface.
type ABI struct {
ByteOrder binary.ByteOrder
Types map[Kind]ABIType
arch string
os string
types map[Kind]Type
SignedChar bool
}
func (a *ABI) sanityCheck(ctx *context, intMaxWidth int, s Scope) error {
if intMaxWidth == 0 {
intMaxWidth = 64
}
a.types = map[Kind]Type{}
for _, k := range []Kind{
Bool,
Char,
Double,
Enum,
Float,
Int,
Long,
LongDouble,
LongLong,
Ptr,
SChar,
Short,
UChar,
UInt,
ULong,
ULongLong,
UShort,
Void,
} {
v, ok := a.Types[k]
if !ok {
if ctx.err(noPos, "ABI is missing %s", k) {
return ctx.Err()
}
continue
}
if (k != Void && v.Size == 0) || v.Align == 0 || v.FieldAlign == 0 ||
v.Align > math.MaxUint8 || v.FieldAlign > math.MaxUint8 {
if ctx.err(noPos, "invalid ABI type %s: %+v", k, v) {
return ctx.Err()
}
}
if integerTypes[k] && v.Size > 8 {
if ctx.err(noPos, "invalid ABI type %s size: %v, must be <= 8", k, v.Size) {
return ctx.Err()
}
}
var f flag
if integerTypes[k] && a.isSignedInteger(k) {
f = fSigned
}
t := &typeBase{
align: byte(a.align(k)),
fieldAlign: byte(a.fieldAlign(k)),
flags: f,
kind: byte(k),
size: uintptr(a.size(k)),
}
a.types[k] = t
}
if _, ok := a.Types[Int128]; ok {
t := &typeBase{
align: byte(a.align(Int128)),
fieldAlign: byte(a.fieldAlign(Int128)),
flags: fSigned,
kind: byte(Int128),
size: uintptr(a.size(Int128)),
}
a.types[Int128] = t
}
if _, ok := a.Types[UInt128]; ok {
t := &typeBase{
align: byte(a.align(UInt128)),
fieldAlign: byte(a.fieldAlign(UInt128)),
kind: byte(UInt128),
size: uintptr(a.size(UInt128)),
}
a.types[UInt128] = t
}
return ctx.Err()
}
func (a *ABI) Type(k Kind) Type { return a.types[k] }
func (a *ABI) align(k Kind) int { return a.Types[k].Align }
func (a *ABI) fieldAlign(k Kind) int { return a.Types[k].FieldAlign }
func (a *ABI) size(k Kind) int { return int(a.Types[k].Size) }
func (a *ABI) isSignedInteger(k Kind) bool {
if !integerTypes[k] {
internalError()
}
switch k {
case Bool, UChar, UInt, ULong, ULongLong, UShort:
return false
case Char:
return a.SignedChar
default:
return true
}
}
func roundup(n, to int64) int64 {
if r := n % to; r != 0 {
return n + to - r
}
return n
}
func roundup128(n uint128.Uint128, to uint64) uint128.Uint128 {
if r := n.Mod(uint128.From64(to)); !r.IsZero() {
return n.Add64(to).Sub(r)
}
return n
}
func rounddown(n, to int64) int64 {
return n &^ (to - 1)
}
func rounddown128(n uint128.Uint128, to uint64) uint128.Uint128 {
return n.And(uint128.Uint128{Hi: ^uint64(0), Lo: ^(to - 1)})
}
func normalizeBitFieldWidth(n byte) byte {
switch {
case n <= 8:
return 8
case n <= 16:
return 16
case n <= 32:
return 32
case n <= 64:
return 64
default:
panic(todo("internal error: %v", n))
}
}
func (a *ABI) layout(ctx *context, n Node, t *structType) *structType {
if t == nil {
return nil
}
if t.typeBase.align < 1 {
t.typeBase.align = 1
}
for _, v := range t.attr {
if _, ok := v.Has(idGCCStruct); ok {
return a.gccLayout(ctx, n, t)
}
//TODO if _, ok := v.Has(idMSStruct); ok {
//TODO return a.msLayout(ctx, n, t)
//TODO }
}
switch {
case ctx.cfg.Config3.GCCStructs:
return a.gccLayout(ctx, n, t)
//TODO case ctx.cfg.Config3.MSStructs:
//TODO return a.msLayout(ctx, n, t)
}
var hasBitfields bool
defer func() {
if !hasBitfields {
return
}
m := make(map[uintptr][]*field, len(t.fields))
for _, f := range t.fields {
off := f.offset
m[off] = append(m[off], f)
}
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for _, s := range m {
var first *field
var w byte
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for _, f := range s {
if first == nil {
first = f
}
if f.isBitField {
n := f.bitFieldOffset + f.bitFieldWidth
if n > w {
w = n
}
}
}
w = normalizeBitFieldWidth(w)
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for _, f := range s {
if f.isBitField {
f.blockStart = first
f.blockWidth = w
}
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if a.ByteOrder == binary.BigEndian {
f.bitFieldOffset = w - f.bitFieldWidth - f.bitFieldOffset
f.bitFieldMask = (uint64(1)<<f.bitFieldWidth - 1) << f.bitFieldOffset
}
}
}
}()
var off int64 // bit offset
align := int(t.typeBase.align)
switch {
case t.Kind() == Union:
for _, f := range t.fields {
ft := f.Type()
sz := ft.Size()
if n := int64(8 * sz); n > off {
off = n
}
al := ft.FieldAlign()
if al == 0 {
al = 1
}
if al > align {
align = al
}
if f.isBitField {
hasBitfields = true
f.bitFieldMask = 1<<f.bitFieldWidth - 1
}
f.promote = integerPromotion(a, ft)
}
t.align = byte(align)
t.fieldAlign = byte(align)
off = roundup(off, 8*int64(align))
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
default:
var i int
var group byte
var f, lf *field
for i, f = range t.fields {
ft := f.Type()
var sz uintptr
switch {
case ft.Kind() == Array && i == len(t.fields)-1:
if ft.IsIncomplete() || ft.Len() == 0 {
t.hasFlexibleMember = true
f.isFlexible = true
break
}
fallthrough
default:
sz = ft.Size()
}
bitSize := 8 * int(sz)
al := ft.FieldAlign()
if al == 0 {
al = 1
}
if al > align {
align = al
}
switch {
case f.isBitField:
hasBitfields = true
eal := 8 * al
if eal < bitSize {
eal = bitSize
}
down := off &^ (int64(eal) - 1)
bitoff := off - down
downMax := off &^ (int64(bitSize) - 1)
skip := lf != nil && lf.isBitField && lf.bitFieldWidth == 0 ||
lf != nil && lf.bitFieldWidth == 0 && ctx.cfg.NoFieldAndBitfieldOverlap
switch {
case skip || int(off-downMax)+int(f.bitFieldWidth) > bitSize:
group = 0
off = roundup(off, 8*int64(al))
f.offset = uintptr(off >> 3)
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
off += int64(f.bitFieldWidth)
if f.bitFieldWidth == 0 {
lf = f
continue
}
default:
f.offset = uintptr(down >> 3)
f.bitFieldOffset = byte(bitoff)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << byte(bitoff)
off += int64(f.bitFieldWidth)
}
group += f.bitFieldWidth
default:
if n := group % 64; n != 0 {
group -= n
off += int64(normalizeBitFieldWidth(group) - group)
}
off0 := off
off = roundup(off, 8*int64(al))
f.pad = byte(off-off0) >> 3
f.offset = uintptr(off) >> 3
off += 8 * int64(sz)
group = 0
}
f.promote = integerPromotion(a, ft)
lf = f
}
t.align = byte(align)
t.fieldAlign = byte(align)
off0 := off
off = roundup(off, 8*int64(align))
if f != nil && !f.IsBitField() {
f.pad = byte(off-off0) >> 3
}
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
}
return t
}
func (a *ABI) Ptr(n Node, t Type) Type {
base := t.base()
base.align = byte(a.align(Ptr))
base.fieldAlign = byte(a.fieldAlign(Ptr))
base.kind = byte(Ptr)
base.size = uintptr(a.size(Ptr))
base.flags &^= fIncomplete
return &pointerType{
elem: t,
typeBase: base,
}
}
func (a *ABI) gccLayout(ctx *context, n Node, t *structType) (r *structType) {
if t.IsPacked() {
return a.gccPackedLayout(ctx, n, t)
}
if t.Kind() == Union {
var off uint128.Uint128 // In bits.
align := int(t.typeBase.align)
for _, f := range t.fields {
switch {
case f.isBitField:
f.offset = 0
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
if uint64(f.bitFieldWidth) > off.Lo {
off.Lo = uint64(f.bitFieldWidth)
}
default:
al := f.Type().Align()
if al > align {
align = al
}
f.offset = 0
off2 := uint128.From64(uint64(f.Type().Size())).Mul64(8)
if off2.Cmp(off) > 0 {
off = off2
}
}
f.promote = integerPromotion(a, f.Type())
}
t.align = byte(align)
t.fieldAlign = byte(align)
off = roundup128(off, 8*uint64(align))
t.size = uintptr(off.Rsh(3).Lo)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
var off uint128.Uint128 // In bits.
align := int(t.typeBase.align)
for i, f := range t.fields {
switch {
case f.isBitField:
al := f.Type().Align()
// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
// 1. Jump backwards to nearest address that would support this type. For
// example if we have an int jump to the closest address where an int could be
// stored according to the platform alignment rules.
down := rounddown128(off, 8*uint64(al))
// 2. Get sizeof(current field) bytes from that address.
alloc := int64(f.Type().Size()) * 8
need := int64(f.bitFieldWidth)
if need == 0 && i != 0 {
off = roundup128(off, 8*uint64(al))
continue
}
if al > align {
align = al
}
used := int64(off.Sub(down).Lo)
switch {
case alloc-used >= need:
// 3. If the number of bits that we need to store can be stored in these bits,
// put the bits in the lowest possible bits of this block.
off = down.Add64(uint64(used))
f.offset = uintptr(down.Rsh(3).Lo)
f.bitFieldOffset = byte(used)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
off = off.Add64(uint64(f.bitFieldWidth))
f.promote = integerPromotion(a, f.Type())
default:
// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
// make up this bit-field in the lowest bits of the next block.
off = roundup128(off, 8*uint64(al))
f.offset = uintptr(off.Rsh(3).Lo)
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
off = off.Add64(uint64(f.bitFieldWidth))
f.promote = integerPromotion(a, f.Type())
}
default:
al := f.Type().Align()
if al > align {
align = al
}
off = roundup128(off, 8*uint64(al))
f.offset = uintptr(off.Rsh(3).Lo)
sz := uint128.From64(uint64(f.Type().Size()))
off = off.Add(sz.Mul64(8))
f.promote = integerPromotion(a, f.Type())
}
}
var lf *field
for _, f := range t.fields {
if lf != nil && !lf.isBitField && !f.isBitField {
lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
}
lf = f
}
t.align = byte(align)
t.fieldAlign = byte(align)
off0 := off
off = roundup128(off, 8*uint64(align))
if lf != nil && !lf.IsBitField() {
lf.pad = byte(off.Sub(off0).Rsh(3).Lo)
}
t.size = uintptr(off.Rsh(3).Lo)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
func (a *ABI) gccPackedLayout(ctx *context, n Node, t *structType) (r *structType) {
switch a.arch {
case "arm", "arm64":
return a.gccPackedLayoutARM(ctx, n, t)
}
if t.typeBase.flags&fAligned == 0 {
t.align = 1
}
t.fieldAlign = t.align
if t.Kind() == Union {
var off int64 // In bits.
for _, f := range t.fields {
switch {
case f.isBitField:
panic(todo("%v: ", n.Position()))
default:
f.offset = 0
if off2 := 8 * int64(f.Type().Size()); off2 > off {
off = off2
}
f.promote = integerPromotion(a, f.Type())
}
}
off = roundup(off, 8)
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
var off int64 // In bits.
for i, f := range t.fields {
switch {
case f.isBitField:
if f.bitFieldWidth == 0 {
if i != 0 {
off = roundup(off, 8*int64(f.Type().Align()))
}
continue
}
if b := f.Type().base(); b.flags&fAligned != 0 {
off = roundup(off, 8*int64(a.Types[f.Type().Kind()].Align))
}
f.offset = uintptr(off >> 3)
f.bitFieldOffset = byte(off & 7)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << f.bitFieldOffset
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
default:
al := f.Type().Align()
off = roundup(off, 8*int64(al))
f.offset = uintptr(off) >> 3
off += 8 * int64(f.Type().Size())
f.promote = integerPromotion(a, f.Type())
}
}
var lf *field
for _, f := range t.fields {
if lf != nil && !lf.isBitField && !f.isBitField {
lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
}
lf = f
}
off0 := off
off = roundup(off, 8*int64(t.Align()))
if lf != nil && !lf.IsBitField() {
lf.pad = byte(off-off0) >> 3
}
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
func (a *ABI) gccPackedLayoutARM(ctx *context, n Node, t *structType) (r *structType) {
align := 1
if t.typeBase.flags&fAligned == 0 {
t.align = 1
}
t.fieldAlign = t.align
if t.Kind() == Union {
var off int64 // In bits.
for _, f := range t.fields {
switch {
case f.isBitField:
panic(todo("%v: ", n.Position()))
default:
f.offset = 0
if off2 := 8 * int64(f.Type().Size()); off2 > off {
off = off2
}
f.promote = integerPromotion(a, f.Type())
}
}
off = roundup(off, 8)
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
var off int64 // In bits.
for i, f := range t.fields {
switch {
case f.isBitField:
if f.bitFieldWidth == 0 {
al := f.Type().Align()
if al > align {
align = al
}
if i != 0 {
off = roundup(off, 8*int64(f.Type().Align()))
}
continue
}
if b := f.Type().base(); b.flags&fAligned != 0 {
off = roundup(off, 8*int64(a.Types[f.Type().Kind()].Align))
}
f.offset = uintptr(off >> 3)
f.bitFieldOffset = byte(off & 7)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << f.bitFieldOffset
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
default:
al := f.Type().Align()
off = roundup(off, 8*int64(al))
f.offset = uintptr(off) >> 3
off += 8 * int64(f.Type().Size())
f.promote = integerPromotion(a, f.Type())
}
}
var lf *field
for _, f := range t.fields {
if lf != nil && !lf.isBitField && !f.isBitField {
lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
}
lf = f
}
if b := t.base(); b.flags&fAligned == 0 {
t.align = byte(align)
t.fieldAlign = byte(align)
}
off0 := off
off = roundup(off, 8*int64(t.Align()))
if lf != nil && !lf.IsBitField() {
lf.pad = byte(off-off0) >> 3
}
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
// https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html#x86-Options
//
// -mno-ms-bitfields
//
// Enable/disable bit-field layout compatible with the native Microsoft Windows
// compiler.
//
// If packed is used on a structure, or if bit-fields are used, it may be that
// the Microsoft ABI lays out the structure differently than the way GCC
// normally does. Particularly when moving packed data between functions
// compiled with GCC and the native Microsoft compiler (either via function
// call or as data in a file), it may be necessary to access either format.
//
// This option is enabled by default for Microsoft Windows targets. This
// behavior can also be controlled locally by use of variable or type
// attributes. For more information, see x86 Variable Attributes and x86 Type
// Attributes.
//
// The Microsoft structure layout algorithm is fairly simple with the exception
// of the bit-field packing. The padding and alignment of members of structures
// and whether a bit-field can straddle a storage-unit boundary are determine
// by these rules:
//
// Structure members are stored sequentially in the order in which they are
// declared: the first member has the lowest memory address and the last member
// the highest. Every data object has an alignment requirement. The alignment
// requirement for all data except structures, unions, and arrays is either the
// size of the object or the current packing size (specified with either the
// aligned attribute or the pack pragma), whichever is less. For structures,
// unions, and arrays, the alignment requirement is the largest alignment
// requirement of its members. Every object is allocated an offset so that:
// offset % alignment_requirement == 0 Adjacent bit-fields are packed into the
// same 1-, 2-, or 4-byte allocation unit if the integral types are the same
// size and if the next bit-field fits into the current allocation unit without
// crossing the boundary imposed by the common alignment requirements of the
// bit-fields. MSVC interprets zero-length bit-fields in the following ways:
//
// If a zero-length bit-field is inserted between two bit-fields that are
// normally coalesced, the bit-fields are not coalesced. For example:
//
// struct
// {
// unsigned long bf_1 : 12;
// unsigned long : 0;
// unsigned long bf_2 : 12;
// } t1;
//
// The size of t1 is 8 bytes with the zero-length bit-field. If the zero-length
// bit-field were removed, t1s size would be 4 bytes.
//
// If a zero-length bit-field is inserted after a bit-field, foo, and the
// alignment of the zero-length bit-field is greater than the member that
// follows it, bar, bar is aligned as the type of the zero-length bit-field.
// For example:
//
// struct
// {
// char foo : 4;
// short : 0;
// char bar;
// } t2;
//
// struct
// {
// char foo : 4;
// short : 0;
// double bar;
// } t3;
//
// For t2, bar is placed at offset 2, rather than offset 1. Accordingly, the
// size of t2 is 4. For t3, the zero-length bit-field does not affect the
// alignment of bar or, as a result, the size of the structure.
//
// Taking this into account, it is important to note the following:
//
// If a zero-length bit-field follows a normal bit-field, the type of the
// zero-length bit-field may affect the alignment of the structure as whole.
// For example, t2 has a size of 4 bytes, since the zero-length bit-field
// follows a normal bit-field, and is of type short. Even if a zero-length
// bit-field is not followed by a normal bit-field, it may still affect the
// alignment of the structure:
//
// struct
// {
// char foo : 6;
// long : 0;
// } t4;
//
// Here, t4 takes up 4 bytes.
//
// Zero-length bit-fields following non-bit-field members are ignored:
//
// struct
// {
// char foo;
// long : 0;
// char bar;
// } t5;
//
// Here, t5 takes up 2 bytes.
func (a *ABI) msLayout(ctx *context, n Node, t *structType) (r *structType) {
if t.IsPacked() {
return a.msPackedLayout(ctx, n, t)
}
if t.Kind() == Union {
panic(todo(""))
}
var off int64 // In bits.
align := int(t.typeBase.align)
var prev *field
for i, f := range t.fields {
switch {
case f.isBitField:
al := f.Type().Align()
if prev != nil {
switch {
case prev.isBitField && prev.Type().Size() != f.Type().Size():
off = roundup(off, 8*int64(prev.Type().Align()))
off = roundup(off, 8*int64(al))
case !prev.isBitField:
off = roundup(off, 8*int64(al))
default:
// Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte allocation
// unit if the integral types are the same size and if the next bit-field fits
// into the current allocation unit without crossing the boundary imposed by
// the common alignment requirements of the bit-fields.
}
}
// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
// 1. Jump backwards to nearest address that would support this type. For
// example if we have an int jump to the closest address where an int could be
// stored according to the platform alignment rules.
down := rounddown(off, 8*int64(al))
// 2. Get sizeof(current field) bytes from that address.
alloc := int64(f.Type().Size()) * 8
need := int64(f.bitFieldWidth)
if need == 0 && i != 0 {
off = roundup(off, 8*int64(al))
continue
}
if al > align {
align = al
}
used := off - down
switch {
case alloc-used >= need:
// 3. If the number of bits that we need to store can be stored in these bits,
// put the bits in the lowest possible bits of this block.
off = down + used
f.offset = uintptr(down >> 3)
f.bitFieldOffset = byte(used)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
default:
// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
// make up this bit-field in the lowest bits of the next block.
off = roundup(off, 8*int64(al))
f.offset = uintptr(off >> 3)
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
}
default:
if prev != nil && prev.isBitField {
off = roundup(off, 8*int64(prev.Type().Align()))
}
al := f.Type().Align()
if al > align {
align = al
}
off = roundup(off, 8*int64(al))
f.offset = uintptr(off) >> 3
off += 8 * int64(f.Type().Size())
f.promote = integerPromotion(a, f.Type())
}
prev = f
}
var lf *field
for _, f := range t.fields {
if lf != nil && !lf.isBitField && !f.isBitField {
lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
}
lf = f
}
t.align = byte(align)
t.fieldAlign = byte(align)
off0 := off
off = roundup(off, 8*int64(align))
if lf != nil && !lf.IsBitField() {
lf.pad = byte(off-off0) >> 3
}
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
func (a *ABI) msPackedLayout(ctx *context, n Node, t *structType) (r *structType) {
if t.typeBase.flags&fAligned == 0 {
t.align = 1
}
t.fieldAlign = t.align
if t.Kind() == Union {
panic(todo(""))
var off int64 // In bits.
for _, f := range t.fields {
switch {
case f.isBitField:
panic(todo("%v: ", n.Position()))
default:
f.offset = 0
if off2 := 8 * int64(f.Type().Size()); off2 > off {
off = off2
}
f.promote = integerPromotion(a, f.Type())
}
}
off = roundup(off, 8)
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}
var off int64 // In bits.
var prev *field
align := int(t.typeBase.align)
for i, f := range t.fields {
out:
switch {
case f.isBitField:
al := f.Type().Align()
switch {
case prev != nil && prev.IsBitField() && prev.Type().Size() != f.Type().Size():
off = mathutil.MaxInt64(off, int64(prev.Offset()*8)+int64(prev.BitFieldOffset()+8*prev.Type().Align()))
off = roundup(off, 8*int64(align))
f.offset = uintptr(off >> 3)
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
break out
}
// http://jkz.wtf/bit-field-packing-in-gcc-and-clang
// 1. Jump backwards to nearest address that would support this type. For
// example if we have an int jump to the closest address where an int could be
// stored according to the platform alignment rules.
down := rounddown(off, 8*int64(al))
// 2. Get sizeof(current field) bytes from that address.
alloc := int64(f.Type().Size()) * 8
need := int64(f.bitFieldWidth)
if need == 0 && i != 0 {
off = roundup(off, 8*int64(al))
continue
}
used := off - down
switch {
case alloc-used >= need:
// 3. If the number of bits that we need to store can be stored in these bits,
// put the bits in the lowest possible bits of this block.
off = down + used
f.offset = uintptr(down >> 3)
f.bitFieldOffset = byte(used)
f.bitFieldMask = (1<<f.bitFieldWidth - 1) << used
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
default:
// 4. Otherwise, pad the rest of this block with zeros, and store the bits that
// make up this bit-field in the lowest bits of the next block.
off = roundup(off, 8*int64(al))
f.offset = uintptr(off >> 3)
f.bitFieldOffset = 0
f.bitFieldMask = 1<<f.bitFieldWidth - 1
off += int64(f.bitFieldWidth)
f.promote = integerPromotion(a, f.Type())
}
default:
off = roundup(off, 8)
f.offset = uintptr(off) >> 3
off += 8 * int64(f.Type().Size())
f.promote = integerPromotion(a, f.Type())
}
prev = f
}
var lf *field
for _, f := range t.fields {
if lf != nil && !lf.isBitField && !f.isBitField {
lf.pad = byte(f.offset - lf.offset - lf.Type().Size())
}
lf = f
}
t.align = byte(align)
t.fieldAlign = byte(align)
switch {
case lf != nil && lf.IsBitField():
off = mathutil.MaxInt64(off, int64(lf.Offset()*8)+int64(lf.BitFieldOffset()+8*lf.Type().Align()))
off = roundup(off, 8*int64(align))
default:
off0 := off
off = roundup(off, 8*int64(align))
if lf != nil && !lf.IsBitField() {
lf.pad = byte(off-off0) >> 3
}
}
t.size = uintptr(off >> 3)
ctx.structs[StructInfo{Size: t.size, Align: t.Align()}] = struct{}{}
return t
}