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// Copyright 2009 The Go 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 gc
import (
"cmd/compile/internal/types"
"cmd/internal/gcprog"
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/src"
"fmt"
"os"
"sort"
"strings"
"sync"
)
type itabEntry struct {
t, itype *types.Type
lsym *obj.LSym // symbol of the itab itself
// symbols of each method in
// the itab, sorted by byte offset;
// filled in by peekitabs
entries []*obj.LSym
}
type ptabEntry struct {
s *types.Sym
t *types.Type
}
// runtime interface and reflection data structures
var (
signatmu sync.Mutex // protects signatset and signatslice
signatset = make(map[*types.Type]struct{})
signatslice []*types.Type
itabs []itabEntry
ptabs []ptabEntry
)
type Sig struct {
name *types.Sym
isym *types.Sym
tsym *types.Sym
type_ *types.Type
mtype *types.Type
}
// Builds a type representing a Bucket structure for
// the given map type. This type is not visible to users -
// we include only enough information to generate a correct GC
// program for it.
// Make sure this stays in sync with runtime/map.go.
const (
BUCKETSIZE = 8
MAXKEYSIZE = 128
MAXVALSIZE = 128
)
func structfieldSize() int { return 3 * Widthptr } // Sizeof(runtime.structfield{})
func imethodSize() int { return 4 + 4 } // Sizeof(runtime.imethod{})
func uncommonSize(t *types.Type) int { // Sizeof(runtime.uncommontype{})
if t.Sym == nil && len(methods(t)) == 0 {
return 0
}
return 4 + 2 + 2 + 4 + 4
}
func makefield(name string, t *types.Type) *types.Field {
f := types.NewField()
f.Type = t
f.Sym = (*types.Pkg)(nil).Lookup(name)
return f
}
// bmap makes the map bucket type given the type of the map.
func bmap(t *types.Type) *types.Type {
if t.MapType().Bucket != nil {
return t.MapType().Bucket
}
bucket := types.New(TSTRUCT)
keytype := t.Key()
valtype := t.Elem()
dowidth(keytype)
dowidth(valtype)
if keytype.Width > MAXKEYSIZE {
keytype = types.NewPtr(keytype)
}
if valtype.Width > MAXVALSIZE {
valtype = types.NewPtr(valtype)
}
field := make([]*types.Field, 0, 5)
// The first field is: uint8 topbits[BUCKETSIZE].
arr := types.NewArray(types.Types[TUINT8], BUCKETSIZE)
field = append(field, makefield("topbits", arr))
arr = types.NewArray(keytype, BUCKETSIZE)
arr.SetNoalg(true)
keys := makefield("keys", arr)
field = append(field, keys)
arr = types.NewArray(valtype, BUCKETSIZE)
arr.SetNoalg(true)
values := makefield("values", arr)
field = append(field, values)
// Make sure the overflow pointer is the last memory in the struct,
// because the runtime assumes it can use size-ptrSize as the
// offset of the overflow pointer. We double-check that property
// below once the offsets and size are computed.
//
// BUCKETSIZE is 8, so the struct is aligned to 64 bits to this point.
// On 32-bit systems, the max alignment is 32-bit, and the
// overflow pointer will add another 32-bit field, and the struct
// will end with no padding.
// On 64-bit systems, the max alignment is 64-bit, and the
// overflow pointer will add another 64-bit field, and the struct
// will end with no padding.
// On nacl/amd64p32, however, the max alignment is 64-bit,
// but the overflow pointer will add only a 32-bit field,
// so if the struct needs 64-bit padding (because a key or value does)
// then it would end with an extra 32-bit padding field.
// Preempt that by emitting the padding here.
if int(valtype.Align) > Widthptr || int(keytype.Align) > Widthptr {
field = append(field, makefield("pad", types.Types[TUINTPTR]))
}
// If keys and values have no pointers, the map implementation
// can keep a list of overflow pointers on the side so that
// buckets can be marked as having no pointers.
// Arrange for the bucket to have no pointers by changing
// the type of the overflow field to uintptr in this case.
// See comment on hmap.overflow in runtime/map.go.
otyp := types.NewPtr(bucket)
if !types.Haspointers(valtype) && !types.Haspointers(keytype) {
otyp = types.Types[TUINTPTR]
}
overflow := makefield("overflow", otyp)
field = append(field, overflow)
// link up fields
bucket.SetNoalg(true)
bucket.SetFields(field[:])
dowidth(bucket)
// Check invariants that map code depends on.
if !IsComparable(t.Key()) {
Fatalf("unsupported map key type for %v", t)
}
if BUCKETSIZE < 8 {
Fatalf("bucket size too small for proper alignment")
}
if keytype.Align > BUCKETSIZE {
Fatalf("key align too big for %v", t)
}
if valtype.Align > BUCKETSIZE {
Fatalf("value align too big for %v", t)
}
if keytype.Width > MAXKEYSIZE {
Fatalf("key size to large for %v", t)
}
if valtype.Width > MAXVALSIZE {
Fatalf("value size to large for %v", t)
}
if t.Key().Width > MAXKEYSIZE && !keytype.IsPtr() {
Fatalf("key indirect incorrect for %v", t)
}
if t.Elem().Width > MAXVALSIZE && !valtype.IsPtr() {
Fatalf("value indirect incorrect for %v", t)
}
if keytype.Width%int64(keytype.Align) != 0 {
Fatalf("key size not a multiple of key align for %v", t)
}
if valtype.Width%int64(valtype.Align) != 0 {
Fatalf("value size not a multiple of value align for %v", t)
}
if bucket.Align%keytype.Align != 0 {
Fatalf("bucket align not multiple of key align %v", t)
}
if bucket.Align%valtype.Align != 0 {
Fatalf("bucket align not multiple of value align %v", t)
}
if keys.Offset%int64(keytype.Align) != 0 {
Fatalf("bad alignment of keys in bmap for %v", t)
}
if values.Offset%int64(valtype.Align) != 0 {
Fatalf("bad alignment of values in bmap for %v", t)
}
// Double-check that overflow field is final memory in struct,
// with no padding at end. See comment above.
if overflow.Offset != bucket.Width-int64(Widthptr) {
Fatalf("bad offset of overflow in bmap for %v", t)
}
t.MapType().Bucket = bucket
bucket.StructType().Map = t
return bucket
}
// hmap builds a type representing a Hmap structure for the given map type.
// Make sure this stays in sync with runtime/map.go.
func hmap(t *types.Type) *types.Type {
if t.MapType().Hmap != nil {
return t.MapType().Hmap
}
bmap := bmap(t)
// build a struct:
// type hmap struct {
// count int
// flags uint8
// B uint8
// noverflow uint16
// hash0 uint32
// buckets *bmap
// oldbuckets *bmap
// nevacuate uintptr
// extra unsafe.Pointer // *mapextra
// }
// must match runtime/map.go:hmap.
fields := []*types.Field{
makefield("count", types.Types[TINT]),
makefield("flags", types.Types[TUINT8]),
makefield("B", types.Types[TUINT8]),
makefield("noverflow", types.Types[TUINT16]),
makefield("hash0", types.Types[TUINT32]), // Used in walk.go for OMAKEMAP.
makefield("buckets", types.NewPtr(bmap)), // Used in walk.go for OMAKEMAP.
makefield("oldbuckets", types.NewPtr(bmap)),
makefield("nevacuate", types.Types[TUINTPTR]),
makefield("extra", types.Types[TUNSAFEPTR]),
}
hmap := types.New(TSTRUCT)
hmap.SetNoalg(true)
hmap.SetFields(fields)
dowidth(hmap)
// The size of hmap should be 48 bytes on 64 bit
// and 28 bytes on 32 bit platforms.
if size := int64(8 + 5*Widthptr); hmap.Width != size {
Fatalf("hmap size not correct: got %d, want %d", hmap.Width, size)
}
t.MapType().Hmap = hmap
hmap.StructType().Map = t
return hmap
}
// hiter builds a type representing an Hiter structure for the given map type.
// Make sure this stays in sync with runtime/map.go.
func hiter(t *types.Type) *types.Type {
if t.MapType().Hiter != nil {
return t.MapType().Hiter
}
hmap := hmap(t)
bmap := bmap(t)
// build a struct:
// type hiter struct {
// key *Key
// val *Value
// t unsafe.Pointer // *MapType
// h *hmap
// buckets *bmap
// bptr *bmap
// overflow unsafe.Pointer // *[]*bmap
// oldoverflow unsafe.Pointer // *[]*bmap
// startBucket uintptr
// offset uint8
// wrapped bool
// B uint8
// i uint8
// bucket uintptr
// checkBucket uintptr
// }
// must match runtime/map.go:hiter.
fields := []*types.Field{
makefield("key", types.NewPtr(t.Key())), // Used in range.go for TMAP.
makefield("val", types.NewPtr(t.Elem())), // Used in range.go for TMAP.
makefield("t", types.Types[TUNSAFEPTR]),
makefield("h", types.NewPtr(hmap)),
makefield("buckets", types.NewPtr(bmap)),
makefield("bptr", types.NewPtr(bmap)),
makefield("overflow", types.Types[TUNSAFEPTR]),
makefield("oldoverflow", types.Types[TUNSAFEPTR]),
makefield("startBucket", types.Types[TUINTPTR]),
makefield("offset", types.Types[TUINT8]),
makefield("wrapped", types.Types[TBOOL]),
makefield("B", types.Types[TUINT8]),
makefield("i", types.Types[TUINT8]),
makefield("bucket", types.Types[TUINTPTR]),
makefield("checkBucket", types.Types[TUINTPTR]),
}
// build iterator struct holding the above fields
hiter := types.New(TSTRUCT)
hiter.SetNoalg(true)
hiter.SetFields(fields)
dowidth(hiter)
if hiter.Width != int64(12*Widthptr) {
Fatalf("hash_iter size not correct %d %d", hiter.Width, 12*Widthptr)
}
t.MapType().Hiter = hiter
hiter.StructType().Map = t
return hiter
}
// f is method type, with receiver.
// return function type, receiver as first argument (or not).
func methodfunc(f *types.Type, receiver *types.Type) *types.Type {
inLen := f.Params().Fields().Len()
if receiver != nil {
inLen++
}
in := make([]*Node, 0, inLen)
if receiver != nil {
d := anonfield(receiver)
in = append(in, d)
}
for _, t := range f.Params().Fields().Slice() {
d := anonfield(t.Type)
d.SetIsDDD(t.IsDDD())
in = append(in, d)
}
outLen := f.Results().Fields().Len()
out := make([]*Node, 0, outLen)
for _, t := range f.Results().Fields().Slice() {
d := anonfield(t.Type)
out = append(out, d)
}
t := functype(nil, in, out)
if f.Nname() != nil {
// Link to name of original method function.
t.SetNname(f.Nname())
}
return t
}
// methods returns the methods of the non-interface type t, sorted by name.
// Generates stub functions as needed.
func methods(t *types.Type) []*Sig {
// method type
mt := methtype(t)
if mt == nil {
return nil
}
expandmeth(mt)
// type stored in interface word
it := t
if !isdirectiface(it) {
it = types.NewPtr(t)
}
// make list of methods for t,
// generating code if necessary.
var ms []*Sig
for _, f := range mt.AllMethods().Slice() {
if f.Type.Etype != TFUNC || f.Type.Recv() == nil {
Fatalf("non-method on %v method %v %v\n", mt, f.Sym, f)
}
if f.Type.Recv() == nil {
Fatalf("receiver with no type on %v method %v %v\n", mt, f.Sym, f)
}
if f.Nointerface() {
continue
}
method := f.Sym
if method == nil {
break
}
// get receiver type for this particular method.
// if pointer receiver but non-pointer t and
// this is not an embedded pointer inside a struct,
// method does not apply.
if !isMethodApplicable(t, f) {
continue
}
sig := &Sig{
name: method,
isym: methodSym(it, method),
tsym: methodSym(t, method),
type_: methodfunc(f.Type, t),
mtype: methodfunc(f.Type, nil),
}
ms = append(ms, sig)
this := f.Type.Recv().Type
if !sig.isym.Siggen() {
sig.isym.SetSiggen(true)
if !types.Identical(this, it) {
genwrapper(it, f, sig.isym)
}
}
if !sig.tsym.Siggen() {
sig.tsym.SetSiggen(true)
if !types.Identical(this, t) {
genwrapper(t, f, sig.tsym)
}
}
}
return ms
}
// imethods returns the methods of the interface type t, sorted by name.
func imethods(t *types.Type) []*Sig {
var methods []*Sig
for _, f := range t.Fields().Slice() {
if f.Type.Etype != TFUNC || f.Sym == nil {
continue
}
if f.Sym.IsBlank() {
Fatalf("unexpected blank symbol in interface method set")
}
if n := len(methods); n > 0 {
last := methods[n-1]
if !last.name.Less(f.Sym) {
Fatalf("sigcmp vs sortinter %v %v", last.name, f.Sym)
}
}
sig := &Sig{
name: f.Sym,
mtype: f.Type,
type_: methodfunc(f.Type, nil),
}
methods = append(methods, sig)
// NOTE(rsc): Perhaps an oversight that
// IfaceType.Method is not in the reflect data.
// Generate the method body, so that compiled
// code can refer to it.
isym := methodSym(t, f.Sym)
if !isym.Siggen() {
isym.SetSiggen(true)
genwrapper(t, f, isym)
}
}
return methods
}
func dimportpath(p *types.Pkg) {
if p.Pathsym != nil {
return
}
// If we are compiling the runtime package, there are two runtime packages around
// -- localpkg and Runtimepkg. We don't want to produce import path symbols for
// both of them, so just produce one for localpkg.
if myimportpath == "runtime" && p == Runtimepkg {
return
}
var str string
if p == localpkg {
// Note: myimportpath != "", or else dgopkgpath won't call dimportpath.
str = myimportpath
} else {
str = p.Path
}
s := Ctxt.Lookup("type..importpath." + p.Prefix + ".")
ot := dnameData(s, 0, str, "", nil, false)
ggloblsym(s, int32(ot), obj.DUPOK|obj.RODATA)
p.Pathsym = s
}
func dgopkgpath(s *obj.LSym, ot int, pkg *types.Pkg) int {
if pkg == nil {
return duintptr(s, ot, 0)
}
if pkg == localpkg && myimportpath == "" {
// If we don't know the full import path of the package being compiled
// (i.e. -p was not passed on the compiler command line), emit a reference to
// type..importpath.""., which the linker will rewrite using the correct import path.
// Every package that imports this one directly defines the symbol.
// See also https://groups.google.com/forum/#!topic/golang-dev/myb9s53HxGQ.
ns := Ctxt.Lookup(`type..importpath."".`)
return dsymptr(s, ot, ns, 0)
}
dimportpath(pkg)
return dsymptr(s, ot, pkg.Pathsym, 0)
}
// dgopkgpathOff writes an offset relocation in s at offset ot to the pkg path symbol.
func dgopkgpathOff(s *obj.LSym, ot int, pkg *types.Pkg) int {
if pkg == nil {
return duint32(s, ot, 0)
}
if pkg == localpkg && myimportpath == "" {
// If we don't know the full import path of the package being compiled
// (i.e. -p was not passed on the compiler command line), emit a reference to
// type..importpath.""., which the linker will rewrite using the correct import path.
// Every package that imports this one directly defines the symbol.
// See also https://groups.google.com/forum/#!topic/golang-dev/myb9s53HxGQ.
ns := Ctxt.Lookup(`type..importpath."".`)
return dsymptrOff(s, ot, ns)
}
dimportpath(pkg)
return dsymptrOff(s, ot, pkg.Pathsym)
}
// dnameField dumps a reflect.name for a struct field.
func dnameField(lsym *obj.LSym, ot int, spkg *types.Pkg, ft *types.Field) int {
if !types.IsExported(ft.Sym.Name) && ft.Sym.Pkg != spkg {
Fatalf("package mismatch for %v", ft.Sym)
}
nsym := dname(ft.Sym.Name, ft.Note, nil, types.IsExported(ft.Sym.Name))
return dsymptr(lsym, ot, nsym, 0)
}
// dnameData writes the contents of a reflect.name into s at offset ot.
func dnameData(s *obj.LSym, ot int, name, tag string, pkg *types.Pkg, exported bool) int {
if len(name) > 1<<16-1 {
Fatalf("name too long: %s", name)
}
if len(tag) > 1<<16-1 {
Fatalf("tag too long: %s", tag)
}
// Encode name and tag. See reflect/type.go for details.
var bits byte
l := 1 + 2 + len(name)
if exported {
bits |= 1 << 0
}
if len(tag) > 0 {
l += 2 + len(tag)
bits |= 1 << 1
}
if pkg != nil {
bits |= 1 << 2
}
b := make([]byte, l)
b[0] = bits
b[1] = uint8(len(name) >> 8)
b[2] = uint8(len(name))
copy(b[3:], name)
if len(tag) > 0 {
tb := b[3+len(name):]
tb[0] = uint8(len(tag) >> 8)
tb[1] = uint8(len(tag))
copy(tb[2:], tag)
}
ot = int(s.WriteBytes(Ctxt, int64(ot), b))
if pkg != nil {
ot = dgopkgpathOff(s, ot, pkg)
}
return ot
}
var dnameCount int
// dname creates a reflect.name for a struct field or method.
func dname(name, tag string, pkg *types.Pkg, exported bool) *obj.LSym {
// Write out data as "type.." to signal two things to the
// linker, first that when dynamically linking, the symbol
// should be moved to a relro section, and second that the
// contents should not be decoded as a type.
sname := "type..namedata."
if pkg == nil {
// In the common case, share data with other packages.
if name == "" {
if exported {
sname += "-noname-exported." + tag
} else {
sname += "-noname-unexported." + tag
}
} else {
if exported {
sname += name + "." + tag
} else {
sname += name + "-" + tag
}
}
} else {
sname = fmt.Sprintf(`%s"".%d`, sname, dnameCount)
dnameCount++
}
s := Ctxt.Lookup(sname)
if len(s.P) > 0 {
return s
}
ot := dnameData(s, 0, name, tag, pkg, exported)
ggloblsym(s, int32(ot), obj.DUPOK|obj.RODATA)
return s
}
// dextratype dumps the fields of a runtime.uncommontype.
// dataAdd is the offset in bytes after the header where the
// backing array of the []method field is written (by dextratypeData).
func dextratype(lsym *obj.LSym, ot int, t *types.Type, dataAdd int) int {
m := methods(t)
if t.Sym == nil && len(m) == 0 {
return ot
}
noff := int(Rnd(int64(ot), int64(Widthptr)))
if noff != ot {
Fatalf("unexpected alignment in dextratype for %v", t)
}
for _, a := range m {
dtypesym(a.type_)
}
ot = dgopkgpathOff(lsym, ot, typePkg(t))
dataAdd += uncommonSize(t)
mcount := len(m)
if mcount != int(uint16(mcount)) {
Fatalf("too many methods on %v: %d", t, mcount)
}
xcount := sort.Search(mcount, func(i int) bool { return !types.IsExported(m[i].name.Name) })
if dataAdd != int(uint32(dataAdd)) {
Fatalf("methods are too far away on %v: %d", t, dataAdd)
}
ot = duint16(lsym, ot, uint16(mcount))
ot = duint16(lsym, ot, uint16(xcount))
ot = duint32(lsym, ot, uint32(dataAdd))
ot = duint32(lsym, ot, 0)
return ot
}
func typePkg(t *types.Type) *types.Pkg {
tsym := t.Sym
if tsym == nil {
switch t.Etype {
case TARRAY, TSLICE, TPTR, TCHAN:
if t.Elem() != nil {
tsym = t.Elem().Sym
}
}
}
if tsym != nil && t != types.Types[t.Etype] && t != types.Errortype {
return tsym.Pkg
}
return nil
}
// dextratypeData dumps the backing array for the []method field of
// runtime.uncommontype.
func dextratypeData(lsym *obj.LSym, ot int, t *types.Type) int {
for _, a := range methods(t) {
// ../../../../runtime/type.go:/method
exported := types.IsExported(a.name.Name)
var pkg *types.Pkg
if !exported && a.name.Pkg != typePkg(t) {
pkg = a.name.Pkg
}
nsym := dname(a.name.Name, "", pkg, exported)
ot = dsymptrOff(lsym, ot, nsym)
ot = dmethodptrOff(lsym, ot, dtypesym(a.mtype))
ot = dmethodptrOff(lsym, ot, a.isym.Linksym())
ot = dmethodptrOff(lsym, ot, a.tsym.Linksym())
}
return ot
}
func dmethodptrOff(s *obj.LSym, ot int, x *obj.LSym) int {
duint32(s, ot, 0)
r := obj.Addrel(s)
r.Off = int32(ot)
r.Siz = 4
r.Sym = x
r.Type = objabi.R_METHODOFF
return ot + 4
}
var kinds = []int{
TINT: objabi.KindInt,
TUINT: objabi.KindUint,
TINT8: objabi.KindInt8,
TUINT8: objabi.KindUint8,
TINT16: objabi.KindInt16,
TUINT16: objabi.KindUint16,
TINT32: objabi.KindInt32,
TUINT32: objabi.KindUint32,
TINT64: objabi.KindInt64,
TUINT64: objabi.KindUint64,
TUINTPTR: objabi.KindUintptr,
TFLOAT32: objabi.KindFloat32,
TFLOAT64: objabi.KindFloat64,
TBOOL: objabi.KindBool,
TSTRING: objabi.KindString,
TPTR: objabi.KindPtr,
TSTRUCT: objabi.KindStruct,
TINTER: objabi.KindInterface,
TCHAN: objabi.KindChan,
TMAP: objabi.KindMap,
TARRAY: objabi.KindArray,
TSLICE: objabi.KindSlice,
TFUNC: objabi.KindFunc,
TCOMPLEX64: objabi.KindComplex64,
TCOMPLEX128: objabi.KindComplex128,
TUNSAFEPTR: objabi.KindUnsafePointer,
}
// typeptrdata returns the length in bytes of the prefix of t
// containing pointer data. Anything after this offset is scalar data.
func typeptrdata(t *types.Type) int64 {
if !types.Haspointers(t) {
return 0
}
switch t.Etype {
case TPTR,
TUNSAFEPTR,
TFUNC,
TCHAN,
TMAP:
return int64(Widthptr)
case TSTRING:
// struct { byte *str; intgo len; }
return int64(Widthptr)
case TINTER:
// struct { Itab *tab; void *data; } or
// struct { Type *type; void *data; }
// Note: see comment in plive.go:onebitwalktype1.
return 2 * int64(Widthptr)
case TSLICE:
// struct { byte *array; uintgo len; uintgo cap; }
return int64(Widthptr)
case TARRAY:
// haspointers already eliminated t.NumElem() == 0.
return (t.NumElem()-1)*t.Elem().Width + typeptrdata(t.Elem())
case TSTRUCT:
// Find the last field that has pointers.
var lastPtrField *types.Field
for _, t1 := range t.Fields().Slice() {
if types.Haspointers(t1.Type) {
lastPtrField = t1
}
}
return lastPtrField.Offset + typeptrdata(lastPtrField.Type)
default:
Fatalf("typeptrdata: unexpected type, %v", t)
return 0
}
}
// tflag is documented in reflect/type.go.
//
// tflag values must be kept in sync with copies in:
// cmd/compile/internal/gc/reflect.go
// cmd/link/internal/ld/decodesym.go
// reflect/type.go
// runtime/type.go
const (
tflagUncommon = 1 << 0
tflagExtraStar = 1 << 1
tflagNamed = 1 << 2
)
var (
algarray *obj.LSym
memhashvarlen *obj.LSym
memequalvarlen *obj.LSym
)
// dcommontype dumps the contents of a reflect.rtype (runtime._type).
func dcommontype(lsym *obj.LSym, t *types.Type) int {
sizeofAlg := 2 * Widthptr
if algarray == nil {
algarray = sysvar("algarray")
}
dowidth(t)
alg := algtype(t)
var algsym *obj.LSym
if alg == ASPECIAL || alg == AMEM {
algsym = dalgsym(t)
}
sptrWeak := true
var sptr *obj.LSym
if !t.IsPtr() || t.IsPtrElem() {
tptr := types.NewPtr(t)
if t.Sym != nil || methods(tptr) != nil {
sptrWeak = false
}
sptr = dtypesym(tptr)
}
gcsym, useGCProg, ptrdata := dgcsym(t)
// ../../../../reflect/type.go:/^type.rtype
// actual type structure
// type rtype struct {
// size uintptr
// ptrdata uintptr
// hash uint32
// tflag tflag
// align uint8
// fieldAlign uint8
// kind uint8
// alg *typeAlg
// gcdata *byte
// str nameOff
// ptrToThis typeOff
// }
ot := 0
ot = duintptr(lsym, ot, uint64(t.Width))
ot = duintptr(lsym, ot, uint64(ptrdata))
ot = duint32(lsym, ot, typehash(t))
var tflag uint8
if uncommonSize(t) != 0 {
tflag |= tflagUncommon
}
if t.Sym != nil && t.Sym.Name != "" {
tflag |= tflagNamed
}
exported := false
p := t.LongString()
// If we're writing out type T,
// we are very likely to write out type *T as well.
// Use the string "*T"[1:] for "T", so that the two
// share storage. This is a cheap way to reduce the
// amount of space taken up by reflect strings.
if !strings.HasPrefix(p, "*") {
p = "*" + p
tflag |= tflagExtraStar
if t.Sym != nil {
exported = types.IsExported(t.Sym.Name)
}
} else {
if t.Elem() != nil && t.Elem().Sym != nil {
exported = types.IsExported(t.Elem().Sym.Name)
}
}
ot = duint8(lsym, ot, tflag)
// runtime (and common sense) expects alignment to be a power of two.
i := int(t.Align)
if i == 0 {
i = 1
}
if i&(i-1) != 0 {
Fatalf("invalid alignment %d for %v", t.Align, t)
}
ot = duint8(lsym, ot, t.Align) // align
ot = duint8(lsym, ot, t.Align) // fieldAlign
i = kinds[t.Etype]
if !types.Haspointers(t) {
i |= objabi.KindNoPointers
}
if isdirectiface(t) {
i |= objabi.KindDirectIface
}
if useGCProg {
i |= objabi.KindGCProg
}
ot = duint8(lsym, ot, uint8(i)) // kind
if algsym == nil {
ot = dsymptr(lsym, ot, algarray, int(alg)*sizeofAlg)
} else {
ot = dsymptr(lsym, ot, algsym, 0)
}
ot = dsymptr(lsym, ot, gcsym, 0) // gcdata
nsym := dname(p, "", nil, exported)
ot = dsymptrOff(lsym, ot, nsym) // str
// ptrToThis
if sptr == nil {
ot = duint32(lsym, ot, 0)
} else if sptrWeak {
ot = dsymptrWeakOff(lsym, ot, sptr)
} else {
ot = dsymptrOff(lsym, ot, sptr)
}
return ot
}
// typeHasNoAlg reports whether t does not have any associated hash/eq
// algorithms because t, or some component of t, is marked Noalg.
func typeHasNoAlg(t *types.Type) bool {
a, bad := algtype1(t)
return a == ANOEQ && bad.Noalg()
}
func typesymname(t *types.Type) string {
name := t.ShortString()
// Use a separate symbol name for Noalg types for #17752.
if typeHasNoAlg(t) {
name = "noalg." + name
}
return name
}
// Fake package for runtime type info (headers)
// Don't access directly, use typeLookup below.
var (
typepkgmu sync.Mutex // protects typepkg lookups
typepkg = types.NewPkg("type", "type")
)
func typeLookup(name string) *types.Sym {
typepkgmu.Lock()
s := typepkg.Lookup(name)
typepkgmu.Unlock()
return s
}
func typesym(t *types.Type) *types.Sym {
return typeLookup(typesymname(t))
}
// tracksym returns the symbol for tracking use of field/method f, assumed
// to be a member of struct/interface type t.
func tracksym(t *types.Type, f *types.Field) *types.Sym {
return trackpkg.Lookup(t.ShortString() + "." + f.Sym.Name)
}
func typesymprefix(prefix string, t *types.Type) *types.Sym {
p := prefix + "." + t.ShortString()
s := typeLookup(p)
// This function is for looking up type-related generated functions
// (e.g. eq and hash). Make sure they are indeed generated.
signatmu.Lock()
addsignat(t)
signatmu.Unlock()
//print("algsym: %s -> %+S\n", p, s);
return s
}
func typenamesym(t *types.Type) *types.Sym {
if t == nil || (t.IsPtr() && t.Elem() == nil) || t.IsUntyped() {
Fatalf("typenamesym %v", t)
}
s := typesym(t)
signatmu.Lock()
addsignat(t)
signatmu.Unlock()
return s
}
func typename(t *types.Type) *Node {
s := typenamesym(t)
if s.Def == nil {
n := newnamel(src.NoXPos, s)
n.Type = types.Types[TUINT8]
n.SetClass(PEXTERN)
n.SetTypecheck(1)
s.Def = asTypesNode(n)
}
n := nod(OADDR, asNode(s.Def), nil)
n.Type = types.NewPtr(asNode(s.Def).Type)
n.SetAddable(true)
n.SetTypecheck(1)
return n
}
func itabname(t, itype *types.Type) *Node {
if t == nil || (t.IsPtr() && t.Elem() == nil) || t.IsUntyped() || !itype.IsInterface() || itype.IsEmptyInterface() {
Fatalf("itabname(%v, %v)", t, itype)
}
s := itabpkg.Lookup(t.ShortString() + "," + itype.ShortString())
if s.Def == nil {
n := newname(s)
n.Type = types.Types[TUINT8]
n.SetClass(PEXTERN)
n.SetTypecheck(1)
s.Def = asTypesNode(n)
itabs = append(itabs, itabEntry{t: t, itype: itype, lsym: s.Linksym()})
}
n := nod(OADDR, asNode(s.Def), nil)
n.Type = types.NewPtr(asNode(s.Def).Type)
n.SetAddable(true)
n.SetTypecheck(1)
return n
}
// isreflexive reports whether t has a reflexive equality operator.
// That is, if x==x for all x of type t.
func isreflexive(t *types.Type) bool {
switch t.Etype {
case TBOOL,
TINT,
TUINT,
TINT8,
TUINT8,
TINT16,
TUINT16,
TINT32,
TUINT32,
TINT64,
TUINT64,
TUINTPTR,
TPTR,
TUNSAFEPTR,
TSTRING,
TCHAN:
return true
case TFLOAT32,
TFLOAT64,
TCOMPLEX64,
TCOMPLEX128,
TINTER:
return false
case TARRAY:
return isreflexive(t.Elem())
case TSTRUCT:
for _, t1 := range t.Fields().Slice() {
if !isreflexive(t1.Type) {
return false
}
}
return true
default:
Fatalf("bad type for map key: %v", t)
return false
}
}
// needkeyupdate reports whether map updates with t as a key
// need the key to be updated.
func needkeyupdate(t *types.Type) bool {
switch t.Etype {
case TBOOL, TINT, TUINT, TINT8, TUINT8, TINT16, TUINT16, TINT32, TUINT32,
TINT64, TUINT64, TUINTPTR, TPTR, TUNSAFEPTR, TCHAN:
return false
case TFLOAT32, TFLOAT64, TCOMPLEX64, TCOMPLEX128, // floats and complex can be +0/-0
TINTER,
TSTRING: // strings might have smaller backing stores
return true
case TARRAY:
return needkeyupdate(t.Elem())
case TSTRUCT:
for _, t1 := range t.Fields().Slice() {
if needkeyupdate(t1.Type) {
return true
}
}
return false
default:
Fatalf("bad type for map key: %v", t)
return true
}
}
// formalType replaces byte and rune aliases with real types.
// They've been separate internally to make error messages
// better, but we have to merge them in the reflect tables.
func formalType(t *types.Type) *types.Type {
if t == types.Bytetype || t == types.Runetype {
return types.Types[t.Etype]
}
return t
}
func dtypesym(t *types.Type) *obj.LSym {
t = formalType(t)
if t.IsUntyped() {
Fatalf("dtypesym %v", t)
}
s := typesym(t)
lsym := s.Linksym()
if s.Siggen() {
return lsym
}
s.SetSiggen(true)
// special case (look for runtime below):
// when compiling package runtime,
// emit the type structures for int, float, etc.
tbase := t
if t.IsPtr() && t.Sym == nil && t.Elem().Sym != nil {
tbase = t.Elem()
}
dupok := 0
if tbase.Sym == nil {
dupok = obj.DUPOK
}
if myimportpath != "runtime" || (tbase != types.Types[tbase.Etype] && tbase != types.Bytetype && tbase != types.Runetype && tbase != types.Errortype) { // int, float, etc
// named types from other files are defined only by those files
if tbase.Sym != nil && tbase.Sym.Pkg != localpkg {
return lsym
}
// TODO(mdempsky): Investigate whether this can happen.
if tbase.Etype == TFORW {
return lsym
}
}
ot := 0
switch t.Etype {
default:
ot = dcommontype(lsym, t)
ot = dextratype(lsym, ot, t, 0)
case TARRAY:
// ../../../../runtime/type.go:/arrayType
s1 := dtypesym(t.Elem())
t2 := types.NewSlice(t.Elem())
s2 := dtypesym(t2)
ot = dcommontype(lsym, t)
ot = dsymptr(lsym, ot, s1, 0)
ot = dsymptr(lsym, ot, s2, 0)
ot = duintptr(lsym, ot, uint64(t.NumElem()))
ot = dextratype(lsym, ot, t, 0)
case TSLICE:
// ../../../../runtime/type.go:/sliceType
s1 := dtypesym(t.Elem())
ot = dcommontype(lsym, t)
ot = dsymptr(lsym, ot, s1, 0)
ot = dextratype(lsym, ot, t, 0)
case TCHAN:
// ../../../../runtime/type.go:/chanType
s1 := dtypesym(t.Elem())
ot = dcommontype(lsym, t)
ot = dsymptr(lsym, ot, s1, 0)
ot = duintptr(lsym, ot, uint64(t.ChanDir()))
ot = dextratype(lsym, ot, t, 0)
case TFUNC:
for _, t1 := range t.Recvs().Fields().Slice() {
dtypesym(t1.Type)
}
isddd := false
for _, t1 := range t.Params().Fields().Slice() {
isddd = t1.IsDDD()
dtypesym(t1.Type)
}
for _, t1 := range t.Results().Fields().Slice() {
dtypesym(t1.Type)
}
ot = dcommontype(lsym, t)
inCount := t.NumRecvs() + t.NumParams()
outCount := t.NumResults()
if isddd {
outCount |= 1 << 15
}
ot = duint16(lsym, ot, uint16(inCount))
ot = duint16(lsym, ot, uint16(outCount))
if Widthptr == 8 {
ot += 4 // align for *rtype
}
dataAdd := (inCount + t.NumResults()) * Widthptr
ot = dextratype(lsym, ot, t, dataAdd)
// Array of rtype pointers follows funcType.
for _, t1 := range t.Recvs().Fields().Slice() {
ot = dsymptr(lsym, ot, dtypesym(t1.Type), 0)
}
for _, t1 := range t.Params().Fields().Slice() {
ot = dsymptr(lsym, ot, dtypesym(t1.Type), 0)
}
for _, t1 := range t.Results().Fields().Slice() {
ot = dsymptr(lsym, ot, dtypesym(t1.Type), 0)
}
case TINTER:
m := imethods(t)
n := len(m)
for _, a := range m {
dtypesym(a.type_)
}
// ../../../../runtime/type.go:/interfaceType
ot = dcommontype(lsym, t)
var tpkg *types.Pkg
if t.Sym != nil && t != types.Types[t.Etype] && t != types.Errortype {
tpkg = t.Sym.Pkg
}
ot = dgopkgpath(lsym, ot, tpkg)
ot = dsymptr(lsym, ot, lsym, ot+3*Widthptr+uncommonSize(t))
ot = duintptr(lsym, ot, uint64(n))
ot = duintptr(lsym, ot, uint64(n))
dataAdd := imethodSize() * n
ot = dextratype(lsym, ot, t, dataAdd)
for _, a := range m {
// ../../../../runtime/type.go:/imethod
exported := types.IsExported(a.name.Name)
var pkg *types.Pkg
if !exported && a.name.Pkg != tpkg {
pkg = a.name.Pkg
}
nsym := dname(a.name.Name, "", pkg, exported)
ot = dsymptrOff(lsym, ot, nsym)
ot = dsymptrOff(lsym, ot, dtypesym(a.type_))
}
// ../../../../runtime/type.go:/mapType
case TMAP:
s1 := dtypesym(t.Key())
s2 := dtypesym(t.Elem())
s3 := dtypesym(bmap(t))
ot = dcommontype(lsym, t)
ot = dsymptr(lsym, ot, s1, 0)
ot = dsymptr(lsym, ot, s2, 0)
ot = dsymptr(lsym, ot, s3, 0)
if t.Key().Width > MAXKEYSIZE {
ot = duint8(lsym, ot, uint8(Widthptr))
ot = duint8(lsym, ot, 1) // indirect
} else {
ot = duint8(lsym, ot, uint8(t.Key().Width))
ot = duint8(lsym, ot, 0) // not indirect
}
if t.Elem().Width > MAXVALSIZE {
ot = duint8(lsym, ot, uint8(Widthptr))
ot = duint8(lsym, ot, 1) // indirect
} else {
ot = duint8(lsym, ot, uint8(t.Elem().Width))
ot = duint8(lsym, ot, 0) // not indirect
}
ot = duint16(lsym, ot, uint16(bmap(t).Width))
ot = duint8(lsym, ot, uint8(obj.Bool2int(isreflexive(t.Key()))))
ot = duint8(lsym, ot, uint8(obj.Bool2int(needkeyupdate(t.Key()))))
ot = dextratype(lsym, ot, t, 0)
case TPTR:
if t.Elem().Etype == TANY {
// ../../../../runtime/type.go:/UnsafePointerType
ot = dcommontype(lsym, t)
ot = dextratype(lsym, ot, t, 0)
break
}
// ../../../../runtime/type.go:/ptrType
s1 := dtypesym(t.Elem())
ot = dcommontype(lsym, t)
ot = dsymptr(lsym, ot, s1, 0)
ot = dextratype(lsym, ot, t, 0)
// ../../../../runtime/type.go:/structType
// for security, only the exported fields.
case TSTRUCT:
fields := t.Fields().Slice()
for _, t1 := range fields {
dtypesym(t1.Type)
}
// All non-exported struct field names within a struct
// type must originate from a single package. By
// identifying and recording that package within the
// struct type descriptor, we can omit that
// information from the field descriptors.
var spkg *types.Pkg
for _, f := range fields {
if !types.IsExported(f.Sym.Name) {
spkg = f.Sym.Pkg
break
}
}
ot = dcommontype(lsym, t)
ot = dgopkgpath(lsym, ot, spkg)
ot = dsymptr(lsym, ot, lsym, ot+3*Widthptr+uncommonSize(t))
ot = duintptr(lsym, ot, uint64(len(fields)))
ot = duintptr(lsym, ot, uint64(len(fields)))
dataAdd := len(fields) * structfieldSize()
ot = dextratype(lsym, ot, t, dataAdd)
for _, f := range fields {
// ../../../../runtime/type.go:/structField
ot = dnameField(lsym, ot, spkg, f)
ot = dsymptr(lsym, ot, dtypesym(f.Type), 0)
offsetAnon := uint64(f.Offset) << 1
if offsetAnon>>1 != uint64(f.Offset) {
Fatalf("%v: bad field offset for %s", t, f.Sym.Name)
}
if f.Embedded != 0 {
offsetAnon |= 1
}
ot = duintptr(lsym, ot, offsetAnon)
}
}
ot = dextratypeData(lsym, ot, t)
ggloblsym(lsym, int32(ot), int16(dupok|obj.RODATA))
// The linker will leave a table of all the typelinks for
// types in the binary, so the runtime can find them.
//
// When buildmode=shared, all types are in typelinks so the
// runtime can deduplicate type pointers.
keep := Ctxt.Flag_dynlink
if !keep && t.Sym == nil {
// For an unnamed type, we only need the link if the type can
// be created at run time by reflect.PtrTo and similar
// functions. If the type exists in the program, those
// functions must return the existing type structure rather
// than creating a new one.
switch t.Etype {
case TPTR, TARRAY, TCHAN, TFUNC, TMAP, TSLICE, TSTRUCT:
keep = true
}
}
// Do not put Noalg types in typelinks. See issue #22605.
if typeHasNoAlg(t) {
keep = false
}
lsym.Set(obj.AttrMakeTypelink, keep)
return lsym
}
// for each itabEntry, gather the methods on
// the concrete type that implement the interface
func peekitabs() {
for i := range itabs {
tab := &itabs[i]
methods := genfun(tab.t, tab.itype)
if len(methods) == 0 {
continue
}
tab.entries = methods
}
}
// for the given concrete type and interface
// type, return the (sorted) set of methods
// on the concrete type that implement the interface
func genfun(t, it *types.Type) []*obj.LSym {
if t == nil || it == nil {
return nil
}
sigs := imethods(it)
methods := methods(t)
out := make([]*obj.LSym, 0, len(sigs))
// TODO(mdempsky): Short circuit before calling methods(t)?
// See discussion on CL 105039.
if len(sigs) == 0 {
return nil
}
// both sigs and methods are sorted by name,
// so we can find the intersect in a single pass
for _, m := range methods {
if m.name == sigs[0].name {
out = append(out, m.isym.Linksym())
sigs = sigs[1:]
if len(sigs) == 0 {
break
}
}
}
if len(sigs) != 0 {
Fatalf("incomplete itab")
}
return out
}
// itabsym uses the information gathered in
// peekitabs to de-virtualize interface methods.
// Since this is called by the SSA backend, it shouldn't
// generate additional Nodes, Syms, etc.
func itabsym(it *obj.LSym, offset int64) *obj.LSym {
var syms []*obj.LSym
if it == nil {
return nil
}
for i := range itabs {
e := &itabs[i]
if e.lsym == it {
syms = e.entries
break
}
}
if syms == nil {
return nil
}
// keep this arithmetic in sync with *itab layout
methodnum := int((offset - 2*int64(Widthptr) - 8) / int64(Widthptr))
if methodnum >= len(syms) {
return nil
}
return syms[methodnum]
}
// addsignat ensures that a runtime type descriptor is emitted for t.
func addsignat(t *types.Type) {
if _, ok := signatset[t]; !ok {
signatset[t] = struct{}{}
signatslice = append(signatslice, t)
}
}
func addsignats(dcls []*Node) {
// copy types from dcl list to signatset
for _, n := range dcls {
if n.Op == OTYPE {
addsignat(n.Type)
}
}
}
func dumpsignats() {
// Process signatset. Use a loop, as dtypesym adds
// entries to signatset while it is being processed.
signats := make([]typeAndStr, len(signatslice))
for len(signatslice) > 0 {
signats = signats[:0]
// Transfer entries to a slice and sort, for reproducible builds.
for _, t := range signatslice {
signats = append(signats, typeAndStr{t: t, short: typesymname(t), regular: t.String()})
delete(signatset, t)
}
signatslice = signatslice[:0]
sort.Sort(typesByString(signats))
for _, ts := range signats {
t := ts.t
dtypesym(t)
if t.Sym != nil {
dtypesym(types.NewPtr(t))
}
}
}
}
func dumptabs() {
// process itabs
for _, i := range itabs {
// dump empty itab symbol into i.sym
// type itab struct {
// inter *interfacetype
// _type *_type
// hash uint32
// _ [4]byte
// fun [1]uintptr // variable sized
// }
o := dsymptr(i.lsym, 0, dtypesym(i.itype), 0)
o = dsymptr(i.lsym, o, dtypesym(i.t), 0)
o = duint32(i.lsym, o, typehash(i.t)) // copy of type hash
o += 4 // skip unused field
for _, fn := range genfun(i.t, i.itype) {
o = dsymptr(i.lsym, o, fn, 0) // method pointer for each method
}
// Nothing writes static itabs, so they are read only.
ggloblsym(i.lsym, int32(o), int16(obj.DUPOK|obj.RODATA))
ilink := itablinkpkg.Lookup(i.t.ShortString() + "," + i.itype.ShortString()).Linksym()
dsymptr(ilink, 0, i.lsym, 0)
ggloblsym(ilink, int32(Widthptr), int16(obj.DUPOK|obj.RODATA))
}
// process ptabs
if localpkg.Name == "main" && len(ptabs) > 0 {
ot := 0
s := Ctxt.Lookup("go.plugin.tabs")
for _, p := range ptabs {
// Dump ptab symbol into go.pluginsym package.
//
// type ptab struct {
// name nameOff
// typ typeOff // pointer to symbol
// }
nsym := dname(p.s.Name, "", nil, true)
ot = dsymptrOff(s, ot, nsym)
ot = dsymptrOff(s, ot, dtypesym(p.t))
}
ggloblsym(s, int32(ot), int16(obj.RODATA))
ot = 0
s = Ctxt.Lookup("go.plugin.exports")
for _, p := range ptabs {
ot = dsymptr(s, ot, p.s.Linksym(), 0)
}
ggloblsym(s, int32(ot), int16(obj.RODATA))
}
}
func dumpimportstrings() {
// generate import strings for imported packages
for _, p := range types.ImportedPkgList() {
dimportpath(p)
}
}
func dumpbasictypes() {
// do basic types if compiling package runtime.
// they have to be in at least one package,
// and runtime is always loaded implicitly,
// so this is as good as any.
// another possible choice would be package main,
// but using runtime means fewer copies in object files.
if myimportpath == "runtime" {
for i := types.EType(1); i <= TBOOL; i++ {
dtypesym(types.NewPtr(types.Types[i]))
}
dtypesym(types.NewPtr(types.Types[TSTRING]))
dtypesym(types.NewPtr(types.Types[TUNSAFEPTR]))
// emit type structs for error and func(error) string.
// The latter is the type of an auto-generated wrapper.
dtypesym(types.NewPtr(types.Errortype))
dtypesym(functype(nil, []*Node{anonfield(types.Errortype)}, []*Node{anonfield(types.Types[TSTRING])}))
// add paths for runtime and main, which 6l imports implicitly.
dimportpath(Runtimepkg)
if flag_race {
dimportpath(racepkg)
}
if flag_msan {
dimportpath(msanpkg)
}
dimportpath(types.NewPkg("main", ""))
}
}
type typeAndStr struct {
t *types.Type
short string
regular string
}
type typesByString []typeAndStr
func (a typesByString) Len() int { return len(a) }
func (a typesByString) Less(i, j int) bool {
if a[i].short != a[j].short {
return a[i].short < a[j].short
}
// When the only difference between the types is whether
// they refer to byte or uint8, such as **byte vs **uint8,
// the types' ShortStrings can be identical.
// To preserve deterministic sort ordering, sort these by String().
return a[i].regular < a[j].regular
}
func (a typesByString) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func dalgsym(t *types.Type) *obj.LSym {
var lsym *obj.LSym
var hashfunc *obj.LSym
var eqfunc *obj.LSym
// dalgsym is only called for a type that needs an algorithm table,
// which implies that the type is comparable (or else it would use ANOEQ).
if algtype(t) == AMEM {
// we use one algorithm table for all AMEM types of a given size
p := fmt.Sprintf(".alg%d", t.Width)
s := typeLookup(p)
lsym = s.Linksym()
if s.AlgGen() {
return lsym
}
s.SetAlgGen(true)
if memhashvarlen == nil {
memhashvarlen = sysfunc("memhash_varlen")
memequalvarlen = sysvar("memequal_varlen") // asm func
}
// make hash closure
p = fmt.Sprintf(".hashfunc%d", t.Width)
hashfunc = typeLookup(p).Linksym()
ot := 0
ot = dsymptr(hashfunc, ot, memhashvarlen, 0)
ot = duintptr(hashfunc, ot, uint64(t.Width)) // size encoded in closure
ggloblsym(hashfunc, int32(ot), obj.DUPOK|obj.RODATA)
// make equality closure
p = fmt.Sprintf(".eqfunc%d", t.Width)
eqfunc = typeLookup(p).Linksym()
ot = 0
ot = dsymptr(eqfunc, ot, memequalvarlen, 0)
ot = duintptr(eqfunc, ot, uint64(t.Width))
ggloblsym(eqfunc, int32(ot), obj.DUPOK|obj.RODATA)
} else {
// generate an alg table specific to this type
s := typesymprefix(".alg", t)
lsym = s.Linksym()
hash := typesymprefix(".hash", t)
eq := typesymprefix(".eq", t)
hashfunc = typesymprefix(".hashfunc", t).Linksym()
eqfunc = typesymprefix(".eqfunc", t).Linksym()
genhash(hash, t)
geneq(eq, t)
// make Go funcs (closures) for calling hash and equal from Go
dsymptr(hashfunc, 0, hash.Linksym(), 0)
ggloblsym(hashfunc, int32(Widthptr), obj.DUPOK|obj.RODATA)
dsymptr(eqfunc, 0, eq.Linksym(), 0)
ggloblsym(eqfunc, int32(Widthptr), obj.DUPOK|obj.RODATA)
}
// ../../../../runtime/alg.go:/typeAlg
ot := 0
ot = dsymptr(lsym, ot, hashfunc, 0)
ot = dsymptr(lsym, ot, eqfunc, 0)
ggloblsym(lsym, int32(ot), obj.DUPOK|obj.RODATA)
return lsym
}
// maxPtrmaskBytes is the maximum length of a GC ptrmask bitmap,
// which holds 1-bit entries describing where pointers are in a given type.
// Above this length, the GC information is recorded as a GC program,
// which can express repetition compactly. In either form, the
// information is used by the runtime to initialize the heap bitmap,
// and for large types (like 128 or more words), they are roughly the
// same speed. GC programs are never much larger and often more
// compact. (If large arrays are involved, they can be arbitrarily
// more compact.)
//
// The cutoff must be large enough that any allocation large enough to
// use a GC program is large enough that it does not share heap bitmap
// bytes with any other objects, allowing the GC program execution to
// assume an aligned start and not use atomic operations. In the current
// runtime, this means all malloc size classes larger than the cutoff must
// be multiples of four words. On 32-bit systems that's 16 bytes, and
// all size classes >= 16 bytes are 16-byte aligned, so no real constraint.
// On 64-bit systems, that's 32 bytes, and 32-byte alignment is guaranteed
// for size classes >= 256 bytes. On a 64-bit system, 256 bytes allocated
// is 32 pointers, the bits for which fit in 4 bytes. So maxPtrmaskBytes
// must be >= 4.
//
// We used to use 16 because the GC programs do have some constant overhead
// to get started, and processing 128 pointers seems to be enough to
// amortize that overhead well.
//
// To make sure that the runtime's chansend can call typeBitsBulkBarrier,
// we raised the limit to 2048, so that even 32-bit systems are guaranteed to
// use bitmaps for objects up to 64 kB in size.
//
// Also known to reflect/type.go.
//
const maxPtrmaskBytes = 2048
// dgcsym emits and returns a data symbol containing GC information for type t,
// along with a boolean reporting whether the UseGCProg bit should be set in
// the type kind, and the ptrdata field to record in the reflect type information.
func dgcsym(t *types.Type) (lsym *obj.LSym, useGCProg bool, ptrdata int64) {
ptrdata = typeptrdata(t)
if ptrdata/int64(Widthptr) <= maxPtrmaskBytes*8 {
lsym = dgcptrmask(t)
return
}
useGCProg = true
lsym, ptrdata = dgcprog(t)
return
}
// dgcptrmask emits and returns the symbol containing a pointer mask for type t.
func dgcptrmask(t *types.Type) *obj.LSym {
ptrmask := make([]byte, (typeptrdata(t)/int64(Widthptr)+7)/8)
fillptrmask(t, ptrmask)
p := fmt.Sprintf("gcbits.%x", ptrmask)
sym := Runtimepkg.Lookup(p)
lsym := sym.Linksym()
if !sym.Uniq() {
sym.SetUniq(true)
for i, x := range ptrmask {
duint8(lsym, i, x)
}
ggloblsym(lsym, int32(len(ptrmask)), obj.DUPOK|obj.RODATA|obj.LOCAL)
}
return lsym
}
// fillptrmask fills in ptrmask with 1s corresponding to the
// word offsets in t that hold pointers.
// ptrmask is assumed to fit at least typeptrdata(t)/Widthptr bits.
func fillptrmask(t *types.Type, ptrmask []byte) {
for i := range ptrmask {
ptrmask[i] = 0
}
if !types.Haspointers(t) {
return
}
vec := bvalloc(8 * int32(len(ptrmask)))
onebitwalktype1(t, 0, vec)
nptr := typeptrdata(t) / int64(Widthptr)
for i := int64(0); i < nptr; i++ {
if vec.Get(int32(i)) {
ptrmask[i/8] |= 1 << (uint(i) % 8)
}
}
}
// dgcprog emits and returns the symbol containing a GC program for type t
// along with the size of the data described by the program (in the range [typeptrdata(t), t.Width]).
// In practice, the size is typeptrdata(t) except for non-trivial arrays.
// For non-trivial arrays, the program describes the full t.Width size.
func dgcprog(t *types.Type) (*obj.LSym, int64) {
dowidth(t)
if t.Width == BADWIDTH {
Fatalf("dgcprog: %v badwidth", t)
}
lsym := typesymprefix(".gcprog", t).Linksym()
var p GCProg
p.init(lsym)
p.emit(t, 0)
offset := p.w.BitIndex() * int64(Widthptr)
p.end()
if ptrdata := typeptrdata(t); offset < ptrdata || offset > t.Width {
Fatalf("dgcprog: %v: offset=%d but ptrdata=%d size=%d", t, offset, ptrdata, t.Width)
}
return lsym, offset
}
type GCProg struct {
lsym *obj.LSym
symoff int
w gcprog.Writer
}
var Debug_gcprog int // set by -d gcprog
func (p *GCProg) init(lsym *obj.LSym) {
p.lsym = lsym
p.symoff = 4 // first 4 bytes hold program length
p.w.Init(p.writeByte)
if Debug_gcprog > 0 {
fmt.Fprintf(os.Stderr, "compile: start GCProg for %v\n", lsym)
p.w.Debug(os.Stderr)
}
}
func (p *GCProg) writeByte(x byte) {
p.symoff = duint8(p.lsym, p.symoff, x)
}
func (p *GCProg) end() {
p.w.End()
duint32(p.lsym, 0, uint32(p.symoff-4))
ggloblsym(p.lsym, int32(p.symoff), obj.DUPOK|obj.RODATA|obj.LOCAL)
if Debug_gcprog > 0 {
fmt.Fprintf(os.Stderr, "compile: end GCProg for %v\n", p.lsym)
}
}
func (p *GCProg) emit(t *types.Type, offset int64) {
dowidth(t)
if !types.Haspointers(t) {
return
}
if t.Width == int64(Widthptr) {
p.w.Ptr(offset / int64(Widthptr))
return
}
switch t.Etype {
default:
Fatalf("GCProg.emit: unexpected type %v", t)
case TSTRING:
p.w.Ptr(offset / int64(Widthptr))
case TINTER:
// Note: the first word isn't a pointer. See comment in plive.go:onebitwalktype1.
p.w.Ptr(offset/int64(Widthptr) + 1)
case TSLICE:
p.w.Ptr(offset / int64(Widthptr))
case TARRAY:
if t.NumElem() == 0 {
// should have been handled by haspointers check above
Fatalf("GCProg.emit: empty array")
}
// Flatten array-of-array-of-array to just a big array by multiplying counts.
count := t.NumElem()
elem := t.Elem()
for elem.IsArray() {
count *= elem.NumElem()
elem = elem.Elem()
}
if !p.w.ShouldRepeat(elem.Width/int64(Widthptr), count) {
// Cheaper to just emit the bits.
for i := int64(0); i < count; i++ {
p.emit(elem, offset+i*elem.Width)
}
return
}
p.emit(elem, offset)
p.w.ZeroUntil((offset + elem.Width) / int64(Widthptr))
p.w.Repeat(elem.Width/int64(Widthptr), count-1)
case TSTRUCT:
for _, t1 := range t.Fields().Slice() {
p.emit(t1.Type, offset+t1.Offset)
}
}
}
// zeroaddr returns the address of a symbol with at least
// size bytes of zeros.
func zeroaddr(size int64) *Node {
if size >= 1<<31 {
Fatalf("map value too big %d", size)
}
if zerosize < size {
zerosize = size
}
s := mappkg.Lookup("zero")
if s.Def == nil {
x := newname(s)
x.Type = types.Types[TUINT8]
x.SetClass(PEXTERN)
x.SetTypecheck(1)
s.Def = asTypesNode(x)
}
z := nod(OADDR, asNode(s.Def), nil)
z.Type = types.NewPtr(types.Types[TUINT8])
z.SetAddable(true)
z.SetTypecheck(1)
return z
}