Source file src/cmd/compile/internal/reflectdata/reflect.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package reflectdata
     6  
     7  import (
     8  	"encoding/binary"
     9  	"fmt"
    10  	"os"
    11  	"sort"
    12  	"strings"
    13  	"sync"
    14  
    15  	"cmd/compile/internal/base"
    16  	"cmd/compile/internal/bitvec"
    17  	"cmd/compile/internal/escape"
    18  	"cmd/compile/internal/inline"
    19  	"cmd/compile/internal/ir"
    20  	"cmd/compile/internal/objw"
    21  	"cmd/compile/internal/staticdata"
    22  	"cmd/compile/internal/typebits"
    23  	"cmd/compile/internal/typecheck"
    24  	"cmd/compile/internal/types"
    25  	"cmd/internal/gcprog"
    26  	"cmd/internal/obj"
    27  	"cmd/internal/objabi"
    28  	"cmd/internal/src"
    29  )
    30  
    31  type ptabEntry struct {
    32  	s *types.Sym
    33  	t *types.Type
    34  }
    35  
    36  func CountPTabs() int {
    37  	return len(ptabs)
    38  }
    39  
    40  // runtime interface and reflection data structures
    41  var (
    42  	// protects signatset and signatslice
    43  	signatmu sync.Mutex
    44  	// Tracking which types need runtime type descriptor
    45  	signatset = make(map[*types.Type]struct{})
    46  	// Queue of types wait to be generated runtime type descriptor
    47  	signatslice []typeAndStr
    48  
    49  	gcsymmu  sync.Mutex // protects gcsymset and gcsymslice
    50  	gcsymset = make(map[*types.Type]struct{})
    51  
    52  	ptabs []*ir.Name
    53  )
    54  
    55  type typeSig struct {
    56  	name  *types.Sym
    57  	isym  *obj.LSym
    58  	tsym  *obj.LSym
    59  	type_ *types.Type
    60  	mtype *types.Type
    61  }
    62  
    63  // Builds a type representing a Bucket structure for
    64  // the given map type. This type is not visible to users -
    65  // we include only enough information to generate a correct GC
    66  // program for it.
    67  // Make sure this stays in sync with runtime/map.go.
    68  const (
    69  	BUCKETSIZE  = 8
    70  	MAXKEYSIZE  = 128
    71  	MAXELEMSIZE = 128
    72  )
    73  
    74  func structfieldSize() int { return 3 * types.PtrSize }       // Sizeof(runtime.structfield{})
    75  func imethodSize() int     { return 4 + 4 }                   // Sizeof(runtime.imethod{})
    76  func commonSize() int      { return 4*types.PtrSize + 8 + 8 } // Sizeof(runtime._type{})
    77  
    78  func uncommonSize(t *types.Type) int { // Sizeof(runtime.uncommontype{})
    79  	if t.Sym() == nil && len(methods(t)) == 0 {
    80  		return 0
    81  	}
    82  	return 4 + 2 + 2 + 4 + 4
    83  }
    84  
    85  func makefield(name string, t *types.Type) *types.Field {
    86  	sym := (*types.Pkg)(nil).Lookup(name)
    87  	return types.NewField(src.NoXPos, sym, t)
    88  }
    89  
    90  // MapBucketType makes the map bucket type given the type of the map.
    91  func MapBucketType(t *types.Type) *types.Type {
    92  	if t.MapType().Bucket != nil {
    93  		return t.MapType().Bucket
    94  	}
    95  
    96  	keytype := t.Key()
    97  	elemtype := t.Elem()
    98  	types.CalcSize(keytype)
    99  	types.CalcSize(elemtype)
   100  	if keytype.Size() > MAXKEYSIZE {
   101  		keytype = types.NewPtr(keytype)
   102  	}
   103  	if elemtype.Size() > MAXELEMSIZE {
   104  		elemtype = types.NewPtr(elemtype)
   105  	}
   106  
   107  	field := make([]*types.Field, 0, 5)
   108  
   109  	// The first field is: uint8 topbits[BUCKETSIZE].
   110  	arr := types.NewArray(types.Types[types.TUINT8], BUCKETSIZE)
   111  	field = append(field, makefield("topbits", arr))
   112  
   113  	arr = types.NewArray(keytype, BUCKETSIZE)
   114  	arr.SetNoalg(true)
   115  	keys := makefield("keys", arr)
   116  	field = append(field, keys)
   117  
   118  	arr = types.NewArray(elemtype, BUCKETSIZE)
   119  	arr.SetNoalg(true)
   120  	elems := makefield("elems", arr)
   121  	field = append(field, elems)
   122  
   123  	// If keys and elems have no pointers, the map implementation
   124  	// can keep a list of overflow pointers on the side so that
   125  	// buckets can be marked as having no pointers.
   126  	// Arrange for the bucket to have no pointers by changing
   127  	// the type of the overflow field to uintptr in this case.
   128  	// See comment on hmap.overflow in runtime/map.go.
   129  	otyp := types.Types[types.TUNSAFEPTR]
   130  	if !elemtype.HasPointers() && !keytype.HasPointers() {
   131  		otyp = types.Types[types.TUINTPTR]
   132  	}
   133  	overflow := makefield("overflow", otyp)
   134  	field = append(field, overflow)
   135  
   136  	// link up fields
   137  	bucket := types.NewStruct(types.NoPkg, field[:])
   138  	bucket.SetNoalg(true)
   139  	types.CalcSize(bucket)
   140  
   141  	// Check invariants that map code depends on.
   142  	if !types.IsComparable(t.Key()) {
   143  		base.Fatalf("unsupported map key type for %v", t)
   144  	}
   145  	if BUCKETSIZE < 8 {
   146  		base.Fatalf("bucket size too small for proper alignment")
   147  	}
   148  	if uint8(keytype.Alignment()) > BUCKETSIZE {
   149  		base.Fatalf("key align too big for %v", t)
   150  	}
   151  	if uint8(elemtype.Alignment()) > BUCKETSIZE {
   152  		base.Fatalf("elem align too big for %v", t)
   153  	}
   154  	if keytype.Size() > MAXKEYSIZE {
   155  		base.Fatalf("key size to large for %v", t)
   156  	}
   157  	if elemtype.Size() > MAXELEMSIZE {
   158  		base.Fatalf("elem size to large for %v", t)
   159  	}
   160  	if t.Key().Size() > MAXKEYSIZE && !keytype.IsPtr() {
   161  		base.Fatalf("key indirect incorrect for %v", t)
   162  	}
   163  	if t.Elem().Size() > MAXELEMSIZE && !elemtype.IsPtr() {
   164  		base.Fatalf("elem indirect incorrect for %v", t)
   165  	}
   166  	if keytype.Size()%keytype.Alignment() != 0 {
   167  		base.Fatalf("key size not a multiple of key align for %v", t)
   168  	}
   169  	if elemtype.Size()%elemtype.Alignment() != 0 {
   170  		base.Fatalf("elem size not a multiple of elem align for %v", t)
   171  	}
   172  	if uint8(bucket.Alignment())%uint8(keytype.Alignment()) != 0 {
   173  		base.Fatalf("bucket align not multiple of key align %v", t)
   174  	}
   175  	if uint8(bucket.Alignment())%uint8(elemtype.Alignment()) != 0 {
   176  		base.Fatalf("bucket align not multiple of elem align %v", t)
   177  	}
   178  	if keys.Offset%keytype.Alignment() != 0 {
   179  		base.Fatalf("bad alignment of keys in bmap for %v", t)
   180  	}
   181  	if elems.Offset%elemtype.Alignment() != 0 {
   182  		base.Fatalf("bad alignment of elems in bmap for %v", t)
   183  	}
   184  
   185  	// Double-check that overflow field is final memory in struct,
   186  	// with no padding at end.
   187  	if overflow.Offset != bucket.Size()-int64(types.PtrSize) {
   188  		base.Fatalf("bad offset of overflow in bmap for %v", t)
   189  	}
   190  
   191  	t.MapType().Bucket = bucket
   192  
   193  	bucket.StructType().Map = t
   194  	return bucket
   195  }
   196  
   197  // MapType builds a type representing a Hmap structure for the given map type.
   198  // Make sure this stays in sync with runtime/map.go.
   199  func MapType(t *types.Type) *types.Type {
   200  	if t.MapType().Hmap != nil {
   201  		return t.MapType().Hmap
   202  	}
   203  
   204  	bmap := MapBucketType(t)
   205  
   206  	// build a struct:
   207  	// type hmap struct {
   208  	//    count      int
   209  	//    flags      uint8
   210  	//    B          uint8
   211  	//    noverflow  uint16
   212  	//    hash0      uint32
   213  	//    buckets    *bmap
   214  	//    oldbuckets *bmap
   215  	//    nevacuate  uintptr
   216  	//    extra      unsafe.Pointer // *mapextra
   217  	// }
   218  	// must match runtime/map.go:hmap.
   219  	fields := []*types.Field{
   220  		makefield("count", types.Types[types.TINT]),
   221  		makefield("flags", types.Types[types.TUINT8]),
   222  		makefield("B", types.Types[types.TUINT8]),
   223  		makefield("noverflow", types.Types[types.TUINT16]),
   224  		makefield("hash0", types.Types[types.TUINT32]), // Used in walk.go for OMAKEMAP.
   225  		makefield("buckets", types.NewPtr(bmap)),       // Used in walk.go for OMAKEMAP.
   226  		makefield("oldbuckets", types.NewPtr(bmap)),
   227  		makefield("nevacuate", types.Types[types.TUINTPTR]),
   228  		makefield("extra", types.Types[types.TUNSAFEPTR]),
   229  	}
   230  
   231  	hmap := types.NewStruct(types.NoPkg, fields)
   232  	hmap.SetNoalg(true)
   233  	types.CalcSize(hmap)
   234  
   235  	// The size of hmap should be 48 bytes on 64 bit
   236  	// and 28 bytes on 32 bit platforms.
   237  	if size := int64(8 + 5*types.PtrSize); hmap.Size() != size {
   238  		base.Fatalf("hmap size not correct: got %d, want %d", hmap.Size(), size)
   239  	}
   240  
   241  	t.MapType().Hmap = hmap
   242  	hmap.StructType().Map = t
   243  	return hmap
   244  }
   245  
   246  // MapIterType builds a type representing an Hiter structure for the given map type.
   247  // Make sure this stays in sync with runtime/map.go.
   248  func MapIterType(t *types.Type) *types.Type {
   249  	if t.MapType().Hiter != nil {
   250  		return t.MapType().Hiter
   251  	}
   252  
   253  	hmap := MapType(t)
   254  	bmap := MapBucketType(t)
   255  
   256  	// build a struct:
   257  	// type hiter struct {
   258  	//    key         *Key
   259  	//    elem        *Elem
   260  	//    t           unsafe.Pointer // *MapType
   261  	//    h           *hmap
   262  	//    buckets     *bmap
   263  	//    bptr        *bmap
   264  	//    overflow    unsafe.Pointer // *[]*bmap
   265  	//    oldoverflow unsafe.Pointer // *[]*bmap
   266  	//    startBucket uintptr
   267  	//    offset      uint8
   268  	//    wrapped     bool
   269  	//    B           uint8
   270  	//    i           uint8
   271  	//    bucket      uintptr
   272  	//    checkBucket uintptr
   273  	// }
   274  	// must match runtime/map.go:hiter.
   275  	fields := []*types.Field{
   276  		makefield("key", types.NewPtr(t.Key())),   // Used in range.go for TMAP.
   277  		makefield("elem", types.NewPtr(t.Elem())), // Used in range.go for TMAP.
   278  		makefield("t", types.Types[types.TUNSAFEPTR]),
   279  		makefield("h", types.NewPtr(hmap)),
   280  		makefield("buckets", types.NewPtr(bmap)),
   281  		makefield("bptr", types.NewPtr(bmap)),
   282  		makefield("overflow", types.Types[types.TUNSAFEPTR]),
   283  		makefield("oldoverflow", types.Types[types.TUNSAFEPTR]),
   284  		makefield("startBucket", types.Types[types.TUINTPTR]),
   285  		makefield("offset", types.Types[types.TUINT8]),
   286  		makefield("wrapped", types.Types[types.TBOOL]),
   287  		makefield("B", types.Types[types.TUINT8]),
   288  		makefield("i", types.Types[types.TUINT8]),
   289  		makefield("bucket", types.Types[types.TUINTPTR]),
   290  		makefield("checkBucket", types.Types[types.TUINTPTR]),
   291  	}
   292  
   293  	// build iterator struct holding the above fields
   294  	hiter := types.NewStruct(types.NoPkg, fields)
   295  	hiter.SetNoalg(true)
   296  	types.CalcSize(hiter)
   297  	if hiter.Size() != int64(12*types.PtrSize) {
   298  		base.Fatalf("hash_iter size not correct %d %d", hiter.Size(), 12*types.PtrSize)
   299  	}
   300  	t.MapType().Hiter = hiter
   301  	hiter.StructType().Map = t
   302  	return hiter
   303  }
   304  
   305  // methods returns the methods of the non-interface type t, sorted by name.
   306  // Generates stub functions as needed.
   307  func methods(t *types.Type) []*typeSig {
   308  	if t.HasShape() {
   309  		// Shape types have no methods.
   310  		return nil
   311  	}
   312  	// method type
   313  	mt := types.ReceiverBaseType(t)
   314  
   315  	if mt == nil {
   316  		return nil
   317  	}
   318  	typecheck.CalcMethods(mt)
   319  
   320  	// make list of methods for t,
   321  	// generating code if necessary.
   322  	var ms []*typeSig
   323  	for _, f := range mt.AllMethods().Slice() {
   324  		if f.Sym == nil {
   325  			base.Fatalf("method with no sym on %v", mt)
   326  		}
   327  		if !f.IsMethod() {
   328  			base.Fatalf("non-method on %v method %v %v", mt, f.Sym, f)
   329  		}
   330  		if f.Type.Recv() == nil {
   331  			base.Fatalf("receiver with no type on %v method %v %v", mt, f.Sym, f)
   332  		}
   333  		if f.Nointerface() && !t.IsFullyInstantiated() {
   334  			// Skip creating method wrappers if f is nointerface. But, if
   335  			// t is an instantiated type, we still have to call
   336  			// methodWrapper, because methodWrapper generates the actual
   337  			// generic method on the type as well.
   338  			continue
   339  		}
   340  
   341  		// get receiver type for this particular method.
   342  		// if pointer receiver but non-pointer t and
   343  		// this is not an embedded pointer inside a struct,
   344  		// method does not apply.
   345  		if !types.IsMethodApplicable(t, f) {
   346  			continue
   347  		}
   348  
   349  		sig := &typeSig{
   350  			name:  f.Sym,
   351  			isym:  methodWrapper(t, f, true),
   352  			tsym:  methodWrapper(t, f, false),
   353  			type_: typecheck.NewMethodType(f.Type, t),
   354  			mtype: typecheck.NewMethodType(f.Type, nil),
   355  		}
   356  		if f.Nointerface() {
   357  			// In the case of a nointerface method on an instantiated
   358  			// type, don't actually apppend the typeSig.
   359  			continue
   360  		}
   361  		ms = append(ms, sig)
   362  	}
   363  
   364  	return ms
   365  }
   366  
   367  // imethods returns the methods of the interface type t, sorted by name.
   368  func imethods(t *types.Type) []*typeSig {
   369  	var methods []*typeSig
   370  	for _, f := range t.AllMethods().Slice() {
   371  		if f.Type.Kind() != types.TFUNC || f.Sym == nil {
   372  			continue
   373  		}
   374  		if f.Sym.IsBlank() {
   375  			base.Fatalf("unexpected blank symbol in interface method set")
   376  		}
   377  		if n := len(methods); n > 0 {
   378  			last := methods[n-1]
   379  			if !last.name.Less(f.Sym) {
   380  				base.Fatalf("sigcmp vs sortinter %v %v", last.name, f.Sym)
   381  			}
   382  		}
   383  
   384  		sig := &typeSig{
   385  			name:  f.Sym,
   386  			mtype: f.Type,
   387  			type_: typecheck.NewMethodType(f.Type, nil),
   388  		}
   389  		methods = append(methods, sig)
   390  
   391  		// NOTE(rsc): Perhaps an oversight that
   392  		// IfaceType.Method is not in the reflect data.
   393  		// Generate the method body, so that compiled
   394  		// code can refer to it.
   395  		methodWrapper(t, f, false)
   396  	}
   397  
   398  	return methods
   399  }
   400  
   401  func dimportpath(p *types.Pkg) {
   402  	if p.Pathsym != nil {
   403  		return
   404  	}
   405  
   406  	// If we are compiling the runtime package, there are two runtime packages around
   407  	// -- localpkg and Pkgs.Runtime. We don't want to produce import path symbols for
   408  	// both of them, so just produce one for localpkg.
   409  	if base.Ctxt.Pkgpath == "runtime" && p == ir.Pkgs.Runtime {
   410  		return
   411  	}
   412  
   413  	str := p.Path
   414  	if p == types.LocalPkg {
   415  		// Note: myimportpath != "", or else dgopkgpath won't call dimportpath.
   416  		str = base.Ctxt.Pkgpath
   417  	}
   418  
   419  	s := base.Ctxt.Lookup("type..importpath." + p.Prefix + ".")
   420  	ot := dnameData(s, 0, str, "", nil, false)
   421  	objw.Global(s, int32(ot), obj.DUPOK|obj.RODATA)
   422  	s.Set(obj.AttrContentAddressable, true)
   423  	p.Pathsym = s
   424  }
   425  
   426  func dgopkgpath(s *obj.LSym, ot int, pkg *types.Pkg) int {
   427  	if pkg == nil {
   428  		return objw.Uintptr(s, ot, 0)
   429  	}
   430  
   431  	if pkg == types.LocalPkg && base.Ctxt.Pkgpath == "" {
   432  		// If we don't know the full import path of the package being compiled
   433  		// (i.e. -p was not passed on the compiler command line), emit a reference to
   434  		// type..importpath.""., which the linker will rewrite using the correct import path.
   435  		// Every package that imports this one directly defines the symbol.
   436  		// See also https://groups.google.com/forum/#!topic/golang-dev/myb9s53HxGQ.
   437  		ns := base.Ctxt.Lookup(`type..importpath."".`)
   438  		return objw.SymPtr(s, ot, ns, 0)
   439  	}
   440  
   441  	dimportpath(pkg)
   442  	return objw.SymPtr(s, ot, pkg.Pathsym, 0)
   443  }
   444  
   445  // dgopkgpathOff writes an offset relocation in s at offset ot to the pkg path symbol.
   446  func dgopkgpathOff(s *obj.LSym, ot int, pkg *types.Pkg) int {
   447  	if pkg == nil {
   448  		return objw.Uint32(s, ot, 0)
   449  	}
   450  	if pkg == types.LocalPkg && base.Ctxt.Pkgpath == "" {
   451  		// If we don't know the full import path of the package being compiled
   452  		// (i.e. -p was not passed on the compiler command line), emit a reference to
   453  		// type..importpath.""., which the linker will rewrite using the correct import path.
   454  		// Every package that imports this one directly defines the symbol.
   455  		// See also https://groups.google.com/forum/#!topic/golang-dev/myb9s53HxGQ.
   456  		ns := base.Ctxt.Lookup(`type..importpath."".`)
   457  		return objw.SymPtrOff(s, ot, ns)
   458  	}
   459  
   460  	dimportpath(pkg)
   461  	return objw.SymPtrOff(s, ot, pkg.Pathsym)
   462  }
   463  
   464  // dnameField dumps a reflect.name for a struct field.
   465  func dnameField(lsym *obj.LSym, ot int, spkg *types.Pkg, ft *types.Field) int {
   466  	if !types.IsExported(ft.Sym.Name) && ft.Sym.Pkg != spkg {
   467  		base.Fatalf("package mismatch for %v", ft.Sym)
   468  	}
   469  	nsym := dname(ft.Sym.Name, ft.Note, nil, types.IsExported(ft.Sym.Name))
   470  	return objw.SymPtr(lsym, ot, nsym, 0)
   471  }
   472  
   473  // dnameData writes the contents of a reflect.name into s at offset ot.
   474  func dnameData(s *obj.LSym, ot int, name, tag string, pkg *types.Pkg, exported bool) int {
   475  	if len(name) >= 1<<29 {
   476  		base.Fatalf("name too long: %d %s...", len(name), name[:1024])
   477  	}
   478  	if len(tag) >= 1<<29 {
   479  		base.Fatalf("tag too long: %d %s...", len(tag), tag[:1024])
   480  	}
   481  	var nameLen [binary.MaxVarintLen64]byte
   482  	nameLenLen := binary.PutUvarint(nameLen[:], uint64(len(name)))
   483  	var tagLen [binary.MaxVarintLen64]byte
   484  	tagLenLen := binary.PutUvarint(tagLen[:], uint64(len(tag)))
   485  
   486  	// Encode name and tag. See reflect/type.go for details.
   487  	var bits byte
   488  	l := 1 + nameLenLen + len(name)
   489  	if exported {
   490  		bits |= 1 << 0
   491  	}
   492  	if len(tag) > 0 {
   493  		l += tagLenLen + len(tag)
   494  		bits |= 1 << 1
   495  	}
   496  	if pkg != nil {
   497  		bits |= 1 << 2
   498  	}
   499  	b := make([]byte, l)
   500  	b[0] = bits
   501  	copy(b[1:], nameLen[:nameLenLen])
   502  	copy(b[1+nameLenLen:], name)
   503  	if len(tag) > 0 {
   504  		tb := b[1+nameLenLen+len(name):]
   505  		copy(tb, tagLen[:tagLenLen])
   506  		copy(tb[tagLenLen:], tag)
   507  	}
   508  
   509  	ot = int(s.WriteBytes(base.Ctxt, int64(ot), b))
   510  
   511  	if pkg != nil {
   512  		ot = dgopkgpathOff(s, ot, pkg)
   513  	}
   514  
   515  	return ot
   516  }
   517  
   518  var dnameCount int
   519  
   520  // dname creates a reflect.name for a struct field or method.
   521  func dname(name, tag string, pkg *types.Pkg, exported bool) *obj.LSym {
   522  	// Write out data as "type.." to signal two things to the
   523  	// linker, first that when dynamically linking, the symbol
   524  	// should be moved to a relro section, and second that the
   525  	// contents should not be decoded as a type.
   526  	sname := "type..namedata."
   527  	if pkg == nil {
   528  		// In the common case, share data with other packages.
   529  		if name == "" {
   530  			if exported {
   531  				sname += "-noname-exported." + tag
   532  			} else {
   533  				sname += "-noname-unexported." + tag
   534  			}
   535  		} else {
   536  			if exported {
   537  				sname += name + "." + tag
   538  			} else {
   539  				sname += name + "-" + tag
   540  			}
   541  		}
   542  	} else {
   543  		sname = fmt.Sprintf(`%s"".%d`, sname, dnameCount)
   544  		dnameCount++
   545  	}
   546  	s := base.Ctxt.Lookup(sname)
   547  	if len(s.P) > 0 {
   548  		return s
   549  	}
   550  	ot := dnameData(s, 0, name, tag, pkg, exported)
   551  	objw.Global(s, int32(ot), obj.DUPOK|obj.RODATA)
   552  	s.Set(obj.AttrContentAddressable, true)
   553  	return s
   554  }
   555  
   556  // dextratype dumps the fields of a runtime.uncommontype.
   557  // dataAdd is the offset in bytes after the header where the
   558  // backing array of the []method field is written (by dextratypeData).
   559  func dextratype(lsym *obj.LSym, ot int, t *types.Type, dataAdd int) int {
   560  	m := methods(t)
   561  	if t.Sym() == nil && len(m) == 0 {
   562  		return ot
   563  	}
   564  	noff := int(types.Rnd(int64(ot), int64(types.PtrSize)))
   565  	if noff != ot {
   566  		base.Fatalf("unexpected alignment in dextratype for %v", t)
   567  	}
   568  
   569  	for _, a := range m {
   570  		writeType(a.type_)
   571  	}
   572  
   573  	ot = dgopkgpathOff(lsym, ot, typePkg(t))
   574  
   575  	dataAdd += uncommonSize(t)
   576  	mcount := len(m)
   577  	if mcount != int(uint16(mcount)) {
   578  		base.Fatalf("too many methods on %v: %d", t, mcount)
   579  	}
   580  	xcount := sort.Search(mcount, func(i int) bool { return !types.IsExported(m[i].name.Name) })
   581  	if dataAdd != int(uint32(dataAdd)) {
   582  		base.Fatalf("methods are too far away on %v: %d", t, dataAdd)
   583  	}
   584  
   585  	ot = objw.Uint16(lsym, ot, uint16(mcount))
   586  	ot = objw.Uint16(lsym, ot, uint16(xcount))
   587  	ot = objw.Uint32(lsym, ot, uint32(dataAdd))
   588  	ot = objw.Uint32(lsym, ot, 0)
   589  	return ot
   590  }
   591  
   592  func typePkg(t *types.Type) *types.Pkg {
   593  	tsym := t.Sym()
   594  	if tsym == nil {
   595  		switch t.Kind() {
   596  		case types.TARRAY, types.TSLICE, types.TPTR, types.TCHAN:
   597  			if t.Elem() != nil {
   598  				tsym = t.Elem().Sym()
   599  			}
   600  		}
   601  	}
   602  	if tsym != nil && tsym.Pkg != types.BuiltinPkg {
   603  		return tsym.Pkg
   604  	}
   605  	return nil
   606  }
   607  
   608  // dextratypeData dumps the backing array for the []method field of
   609  // runtime.uncommontype.
   610  func dextratypeData(lsym *obj.LSym, ot int, t *types.Type) int {
   611  	for _, a := range methods(t) {
   612  		// ../../../../runtime/type.go:/method
   613  		exported := types.IsExported(a.name.Name)
   614  		var pkg *types.Pkg
   615  		if !exported && a.name.Pkg != typePkg(t) {
   616  			pkg = a.name.Pkg
   617  		}
   618  		nsym := dname(a.name.Name, "", pkg, exported)
   619  
   620  		ot = objw.SymPtrOff(lsym, ot, nsym)
   621  		ot = dmethodptrOff(lsym, ot, writeType(a.mtype))
   622  		ot = dmethodptrOff(lsym, ot, a.isym)
   623  		ot = dmethodptrOff(lsym, ot, a.tsym)
   624  	}
   625  	return ot
   626  }
   627  
   628  func dmethodptrOff(s *obj.LSym, ot int, x *obj.LSym) int {
   629  	objw.Uint32(s, ot, 0)
   630  	r := obj.Addrel(s)
   631  	r.Off = int32(ot)
   632  	r.Siz = 4
   633  	r.Sym = x
   634  	r.Type = objabi.R_METHODOFF
   635  	return ot + 4
   636  }
   637  
   638  var kinds = []int{
   639  	types.TINT:        objabi.KindInt,
   640  	types.TUINT:       objabi.KindUint,
   641  	types.TINT8:       objabi.KindInt8,
   642  	types.TUINT8:      objabi.KindUint8,
   643  	types.TINT16:      objabi.KindInt16,
   644  	types.TUINT16:     objabi.KindUint16,
   645  	types.TINT32:      objabi.KindInt32,
   646  	types.TUINT32:     objabi.KindUint32,
   647  	types.TINT64:      objabi.KindInt64,
   648  	types.TUINT64:     objabi.KindUint64,
   649  	types.TUINTPTR:    objabi.KindUintptr,
   650  	types.TFLOAT32:    objabi.KindFloat32,
   651  	types.TFLOAT64:    objabi.KindFloat64,
   652  	types.TBOOL:       objabi.KindBool,
   653  	types.TSTRING:     objabi.KindString,
   654  	types.TPTR:        objabi.KindPtr,
   655  	types.TSTRUCT:     objabi.KindStruct,
   656  	types.TINTER:      objabi.KindInterface,
   657  	types.TCHAN:       objabi.KindChan,
   658  	types.TMAP:        objabi.KindMap,
   659  	types.TARRAY:      objabi.KindArray,
   660  	types.TSLICE:      objabi.KindSlice,
   661  	types.TFUNC:       objabi.KindFunc,
   662  	types.TCOMPLEX64:  objabi.KindComplex64,
   663  	types.TCOMPLEX128: objabi.KindComplex128,
   664  	types.TUNSAFEPTR:  objabi.KindUnsafePointer,
   665  }
   666  
   667  // tflag is documented in reflect/type.go.
   668  //
   669  // tflag values must be kept in sync with copies in:
   670  //	cmd/compile/internal/reflectdata/reflect.go
   671  //	cmd/link/internal/ld/decodesym.go
   672  //	reflect/type.go
   673  //	runtime/type.go
   674  const (
   675  	tflagUncommon      = 1 << 0
   676  	tflagExtraStar     = 1 << 1
   677  	tflagNamed         = 1 << 2
   678  	tflagRegularMemory = 1 << 3
   679  )
   680  
   681  var (
   682  	memhashvarlen  *obj.LSym
   683  	memequalvarlen *obj.LSym
   684  )
   685  
   686  // dcommontype dumps the contents of a reflect.rtype (runtime._type).
   687  func dcommontype(lsym *obj.LSym, t *types.Type) int {
   688  	types.CalcSize(t)
   689  	eqfunc := geneq(t)
   690  
   691  	sptrWeak := true
   692  	var sptr *obj.LSym
   693  	if !t.IsPtr() || t.IsPtrElem() {
   694  		tptr := types.NewPtr(t)
   695  		if t.Sym() != nil || methods(tptr) != nil {
   696  			sptrWeak = false
   697  		}
   698  		sptr = writeType(tptr)
   699  	}
   700  
   701  	gcsym, useGCProg, ptrdata := dgcsym(t, true)
   702  	delete(gcsymset, t)
   703  
   704  	// ../../../../reflect/type.go:/^type.rtype
   705  	// actual type structure
   706  	//	type rtype struct {
   707  	//		size          uintptr
   708  	//		ptrdata       uintptr
   709  	//		hash          uint32
   710  	//		tflag         tflag
   711  	//		align         uint8
   712  	//		fieldAlign    uint8
   713  	//		kind          uint8
   714  	//		equal         func(unsafe.Pointer, unsafe.Pointer) bool
   715  	//		gcdata        *byte
   716  	//		str           nameOff
   717  	//		ptrToThis     typeOff
   718  	//	}
   719  	ot := 0
   720  	ot = objw.Uintptr(lsym, ot, uint64(t.Size()))
   721  	ot = objw.Uintptr(lsym, ot, uint64(ptrdata))
   722  	ot = objw.Uint32(lsym, ot, types.TypeHash(t))
   723  
   724  	var tflag uint8
   725  	if uncommonSize(t) != 0 {
   726  		tflag |= tflagUncommon
   727  	}
   728  	if t.Sym() != nil && t.Sym().Name != "" {
   729  		tflag |= tflagNamed
   730  	}
   731  	if isRegularMemory(t) {
   732  		tflag |= tflagRegularMemory
   733  	}
   734  
   735  	exported := false
   736  	p := t.NameString()
   737  	// If we're writing out type T,
   738  	// we are very likely to write out type *T as well.
   739  	// Use the string "*T"[1:] for "T", so that the two
   740  	// share storage. This is a cheap way to reduce the
   741  	// amount of space taken up by reflect strings.
   742  	if !strings.HasPrefix(p, "*") {
   743  		p = "*" + p
   744  		tflag |= tflagExtraStar
   745  		if t.Sym() != nil {
   746  			exported = types.IsExported(t.Sym().Name)
   747  		}
   748  	} else {
   749  		if t.Elem() != nil && t.Elem().Sym() != nil {
   750  			exported = types.IsExported(t.Elem().Sym().Name)
   751  		}
   752  	}
   753  
   754  	ot = objw.Uint8(lsym, ot, tflag)
   755  
   756  	// runtime (and common sense) expects alignment to be a power of two.
   757  	i := int(uint8(t.Alignment()))
   758  
   759  	if i == 0 {
   760  		i = 1
   761  	}
   762  	if i&(i-1) != 0 {
   763  		base.Fatalf("invalid alignment %d for %v", uint8(t.Alignment()), t)
   764  	}
   765  	ot = objw.Uint8(lsym, ot, uint8(t.Alignment())) // align
   766  	ot = objw.Uint8(lsym, ot, uint8(t.Alignment())) // fieldAlign
   767  
   768  	i = kinds[t.Kind()]
   769  	if types.IsDirectIface(t) {
   770  		i |= objabi.KindDirectIface
   771  	}
   772  	if useGCProg {
   773  		i |= objabi.KindGCProg
   774  	}
   775  	ot = objw.Uint8(lsym, ot, uint8(i)) // kind
   776  	if eqfunc != nil {
   777  		ot = objw.SymPtr(lsym, ot, eqfunc, 0) // equality function
   778  	} else {
   779  		ot = objw.Uintptr(lsym, ot, 0) // type we can't do == with
   780  	}
   781  	ot = objw.SymPtr(lsym, ot, gcsym, 0) // gcdata
   782  
   783  	nsym := dname(p, "", nil, exported)
   784  	ot = objw.SymPtrOff(lsym, ot, nsym) // str
   785  	// ptrToThis
   786  	if sptr == nil {
   787  		ot = objw.Uint32(lsym, ot, 0)
   788  	} else if sptrWeak {
   789  		ot = objw.SymPtrWeakOff(lsym, ot, sptr)
   790  	} else {
   791  		ot = objw.SymPtrOff(lsym, ot, sptr)
   792  	}
   793  
   794  	return ot
   795  }
   796  
   797  // TrackSym returns the symbol for tracking use of field/method f, assumed
   798  // to be a member of struct/interface type t.
   799  func TrackSym(t *types.Type, f *types.Field) *obj.LSym {
   800  	return base.PkgLinksym("go.track", t.LinkString()+"."+f.Sym.Name, obj.ABI0)
   801  }
   802  
   803  func TypeSymPrefix(prefix string, t *types.Type) *types.Sym {
   804  	p := prefix + "." + t.LinkString()
   805  	s := types.TypeSymLookup(p)
   806  
   807  	// This function is for looking up type-related generated functions
   808  	// (e.g. eq and hash). Make sure they are indeed generated.
   809  	signatmu.Lock()
   810  	NeedRuntimeType(t)
   811  	signatmu.Unlock()
   812  
   813  	//print("algsym: %s -> %+S\n", p, s);
   814  
   815  	return s
   816  }
   817  
   818  func TypeSym(t *types.Type) *types.Sym {
   819  	if t == nil || (t.IsPtr() && t.Elem() == nil) || t.IsUntyped() {
   820  		base.Fatalf("TypeSym %v", t)
   821  	}
   822  	if t.Kind() == types.TFUNC && t.Recv() != nil {
   823  		base.Fatalf("misuse of method type: %v", t)
   824  	}
   825  	s := types.TypeSym(t)
   826  	signatmu.Lock()
   827  	NeedRuntimeType(t)
   828  	signatmu.Unlock()
   829  	return s
   830  }
   831  
   832  func TypeLinksymPrefix(prefix string, t *types.Type) *obj.LSym {
   833  	return TypeSymPrefix(prefix, t).Linksym()
   834  }
   835  
   836  func TypeLinksymLookup(name string) *obj.LSym {
   837  	return types.TypeSymLookup(name).Linksym()
   838  }
   839  
   840  func TypeLinksym(t *types.Type) *obj.LSym {
   841  	return TypeSym(t).Linksym()
   842  }
   843  
   844  func TypePtr(t *types.Type) *ir.AddrExpr {
   845  	n := ir.NewLinksymExpr(base.Pos, TypeLinksym(t), types.Types[types.TUINT8])
   846  	return typecheck.Expr(typecheck.NodAddr(n)).(*ir.AddrExpr)
   847  }
   848  
   849  // ITabLsym returns the LSym representing the itab for concrete type typ implementing
   850  // interface iface. A dummy tab will be created in the unusual case where typ doesn't
   851  // implement iface. Normally, this wouldn't happen, because the typechecker would
   852  // have reported a compile-time error. This situation can only happen when the
   853  // destination type of a type assert or a type in a type switch is parameterized, so
   854  // it may sometimes, but not always, be a type that can't implement the specified
   855  // interface.
   856  func ITabLsym(typ, iface *types.Type) *obj.LSym {
   857  	s, existed := ir.Pkgs.Itab.LookupOK(typ.LinkString() + "," + iface.LinkString())
   858  	lsym := s.Linksym()
   859  
   860  	if !existed {
   861  		writeITab(lsym, typ, iface, true)
   862  	}
   863  	return lsym
   864  }
   865  
   866  // ITabAddr returns an expression representing a pointer to the itab
   867  // for concrete type typ implementing interface iface.
   868  func ITabAddr(typ, iface *types.Type) *ir.AddrExpr {
   869  	s, existed := ir.Pkgs.Itab.LookupOK(typ.LinkString() + "," + iface.LinkString())
   870  	lsym := s.Linksym()
   871  
   872  	if !existed {
   873  		writeITab(lsym, typ, iface, false)
   874  	}
   875  
   876  	n := ir.NewLinksymExpr(base.Pos, lsym, types.Types[types.TUINT8])
   877  	return typecheck.Expr(typecheck.NodAddr(n)).(*ir.AddrExpr)
   878  }
   879  
   880  // needkeyupdate reports whether map updates with t as a key
   881  // need the key to be updated.
   882  func needkeyupdate(t *types.Type) bool {
   883  	switch t.Kind() {
   884  	case types.TBOOL, types.TINT, types.TUINT, types.TINT8, types.TUINT8, types.TINT16, types.TUINT16, types.TINT32, types.TUINT32,
   885  		types.TINT64, types.TUINT64, types.TUINTPTR, types.TPTR, types.TUNSAFEPTR, types.TCHAN:
   886  		return false
   887  
   888  	case types.TFLOAT32, types.TFLOAT64, types.TCOMPLEX64, types.TCOMPLEX128, // floats and complex can be +0/-0
   889  		types.TINTER,
   890  		types.TSTRING: // strings might have smaller backing stores
   891  		return true
   892  
   893  	case types.TARRAY:
   894  		return needkeyupdate(t.Elem())
   895  
   896  	case types.TSTRUCT:
   897  		for _, t1 := range t.Fields().Slice() {
   898  			if needkeyupdate(t1.Type) {
   899  				return true
   900  			}
   901  		}
   902  		return false
   903  
   904  	default:
   905  		base.Fatalf("bad type for map key: %v", t)
   906  		return true
   907  	}
   908  }
   909  
   910  // hashMightPanic reports whether the hash of a map key of type t might panic.
   911  func hashMightPanic(t *types.Type) bool {
   912  	switch t.Kind() {
   913  	case types.TINTER:
   914  		return true
   915  
   916  	case types.TARRAY:
   917  		return hashMightPanic(t.Elem())
   918  
   919  	case types.TSTRUCT:
   920  		for _, t1 := range t.Fields().Slice() {
   921  			if hashMightPanic(t1.Type) {
   922  				return true
   923  			}
   924  		}
   925  		return false
   926  
   927  	default:
   928  		return false
   929  	}
   930  }
   931  
   932  // formalType replaces predeclared aliases with real types.
   933  // They've been separate internally to make error messages
   934  // better, but we have to merge them in the reflect tables.
   935  func formalType(t *types.Type) *types.Type {
   936  	switch t {
   937  	case types.AnyType, types.ByteType, types.RuneType:
   938  		return types.Types[t.Kind()]
   939  	}
   940  	return t
   941  }
   942  
   943  func writeType(t *types.Type) *obj.LSym {
   944  	t = formalType(t)
   945  	if t.IsUntyped() || t.HasTParam() {
   946  		base.Fatalf("writeType %v", t)
   947  	}
   948  
   949  	s := types.TypeSym(t)
   950  	lsym := s.Linksym()
   951  	if s.Siggen() {
   952  		return lsym
   953  	}
   954  	s.SetSiggen(true)
   955  
   956  	// special case (look for runtime below):
   957  	// when compiling package runtime,
   958  	// emit the type structures for int, float, etc.
   959  	tbase := t
   960  
   961  	if t.IsPtr() && t.Sym() == nil && t.Elem().Sym() != nil {
   962  		tbase = t.Elem()
   963  	}
   964  	if tbase.Kind() == types.TFORW {
   965  		base.Fatalf("unresolved defined type: %v", tbase)
   966  	}
   967  
   968  	if !NeedEmit(tbase) {
   969  		if i := typecheck.BaseTypeIndex(t); i >= 0 {
   970  			lsym.Pkg = tbase.Sym().Pkg.Prefix
   971  			lsym.SymIdx = int32(i)
   972  			lsym.Set(obj.AttrIndexed, true)
   973  		}
   974  
   975  		// TODO(mdempsky): Investigate whether this still happens.
   976  		// If we know we don't need to emit code for a type,
   977  		// we should have a link-symbol index for it.
   978  		// See also TODO in NeedEmit.
   979  		return lsym
   980  	}
   981  
   982  	ot := 0
   983  	switch t.Kind() {
   984  	default:
   985  		ot = dcommontype(lsym, t)
   986  		ot = dextratype(lsym, ot, t, 0)
   987  
   988  	case types.TARRAY:
   989  		// ../../../../runtime/type.go:/arrayType
   990  		s1 := writeType(t.Elem())
   991  		t2 := types.NewSlice(t.Elem())
   992  		s2 := writeType(t2)
   993  		ot = dcommontype(lsym, t)
   994  		ot = objw.SymPtr(lsym, ot, s1, 0)
   995  		ot = objw.SymPtr(lsym, ot, s2, 0)
   996  		ot = objw.Uintptr(lsym, ot, uint64(t.NumElem()))
   997  		ot = dextratype(lsym, ot, t, 0)
   998  
   999  	case types.TSLICE:
  1000  		// ../../../../runtime/type.go:/sliceType
  1001  		s1 := writeType(t.Elem())
  1002  		ot = dcommontype(lsym, t)
  1003  		ot = objw.SymPtr(lsym, ot, s1, 0)
  1004  		ot = dextratype(lsym, ot, t, 0)
  1005  
  1006  	case types.TCHAN:
  1007  		// ../../../../runtime/type.go:/chanType
  1008  		s1 := writeType(t.Elem())
  1009  		ot = dcommontype(lsym, t)
  1010  		ot = objw.SymPtr(lsym, ot, s1, 0)
  1011  		ot = objw.Uintptr(lsym, ot, uint64(t.ChanDir()))
  1012  		ot = dextratype(lsym, ot, t, 0)
  1013  
  1014  	case types.TFUNC:
  1015  		for _, t1 := range t.Recvs().Fields().Slice() {
  1016  			writeType(t1.Type)
  1017  		}
  1018  		isddd := false
  1019  		for _, t1 := range t.Params().Fields().Slice() {
  1020  			isddd = t1.IsDDD()
  1021  			writeType(t1.Type)
  1022  		}
  1023  		for _, t1 := range t.Results().Fields().Slice() {
  1024  			writeType(t1.Type)
  1025  		}
  1026  
  1027  		ot = dcommontype(lsym, t)
  1028  		inCount := t.NumRecvs() + t.NumParams()
  1029  		outCount := t.NumResults()
  1030  		if isddd {
  1031  			outCount |= 1 << 15
  1032  		}
  1033  		ot = objw.Uint16(lsym, ot, uint16(inCount))
  1034  		ot = objw.Uint16(lsym, ot, uint16(outCount))
  1035  		if types.PtrSize == 8 {
  1036  			ot += 4 // align for *rtype
  1037  		}
  1038  
  1039  		dataAdd := (inCount + t.NumResults()) * types.PtrSize
  1040  		ot = dextratype(lsym, ot, t, dataAdd)
  1041  
  1042  		// Array of rtype pointers follows funcType.
  1043  		for _, t1 := range t.Recvs().Fields().Slice() {
  1044  			ot = objw.SymPtr(lsym, ot, writeType(t1.Type), 0)
  1045  		}
  1046  		for _, t1 := range t.Params().Fields().Slice() {
  1047  			ot = objw.SymPtr(lsym, ot, writeType(t1.Type), 0)
  1048  		}
  1049  		for _, t1 := range t.Results().Fields().Slice() {
  1050  			ot = objw.SymPtr(lsym, ot, writeType(t1.Type), 0)
  1051  		}
  1052  
  1053  	case types.TINTER:
  1054  		m := imethods(t)
  1055  		n := len(m)
  1056  		for _, a := range m {
  1057  			writeType(a.type_)
  1058  		}
  1059  
  1060  		// ../../../../runtime/type.go:/interfaceType
  1061  		ot = dcommontype(lsym, t)
  1062  
  1063  		var tpkg *types.Pkg
  1064  		if t.Sym() != nil && t != types.Types[t.Kind()] && t != types.ErrorType {
  1065  			tpkg = t.Sym().Pkg
  1066  		}
  1067  		ot = dgopkgpath(lsym, ot, tpkg)
  1068  
  1069  		ot = objw.SymPtr(lsym, ot, lsym, ot+3*types.PtrSize+uncommonSize(t))
  1070  		ot = objw.Uintptr(lsym, ot, uint64(n))
  1071  		ot = objw.Uintptr(lsym, ot, uint64(n))
  1072  		dataAdd := imethodSize() * n
  1073  		ot = dextratype(lsym, ot, t, dataAdd)
  1074  
  1075  		for _, a := range m {
  1076  			// ../../../../runtime/type.go:/imethod
  1077  			exported := types.IsExported(a.name.Name)
  1078  			var pkg *types.Pkg
  1079  			if !exported && a.name.Pkg != tpkg {
  1080  				pkg = a.name.Pkg
  1081  			}
  1082  			nsym := dname(a.name.Name, "", pkg, exported)
  1083  
  1084  			ot = objw.SymPtrOff(lsym, ot, nsym)
  1085  			ot = objw.SymPtrOff(lsym, ot, writeType(a.type_))
  1086  		}
  1087  
  1088  	// ../../../../runtime/type.go:/mapType
  1089  	case types.TMAP:
  1090  		s1 := writeType(t.Key())
  1091  		s2 := writeType(t.Elem())
  1092  		s3 := writeType(MapBucketType(t))
  1093  		hasher := genhash(t.Key())
  1094  
  1095  		ot = dcommontype(lsym, t)
  1096  		ot = objw.SymPtr(lsym, ot, s1, 0)
  1097  		ot = objw.SymPtr(lsym, ot, s2, 0)
  1098  		ot = objw.SymPtr(lsym, ot, s3, 0)
  1099  		ot = objw.SymPtr(lsym, ot, hasher, 0)
  1100  		var flags uint32
  1101  		// Note: flags must match maptype accessors in ../../../../runtime/type.go
  1102  		// and maptype builder in ../../../../reflect/type.go:MapOf.
  1103  		if t.Key().Size() > MAXKEYSIZE {
  1104  			ot = objw.Uint8(lsym, ot, uint8(types.PtrSize))
  1105  			flags |= 1 // indirect key
  1106  		} else {
  1107  			ot = objw.Uint8(lsym, ot, uint8(t.Key().Size()))
  1108  		}
  1109  
  1110  		if t.Elem().Size() > MAXELEMSIZE {
  1111  			ot = objw.Uint8(lsym, ot, uint8(types.PtrSize))
  1112  			flags |= 2 // indirect value
  1113  		} else {
  1114  			ot = objw.Uint8(lsym, ot, uint8(t.Elem().Size()))
  1115  		}
  1116  		ot = objw.Uint16(lsym, ot, uint16(MapBucketType(t).Size()))
  1117  		if types.IsReflexive(t.Key()) {
  1118  			flags |= 4 // reflexive key
  1119  		}
  1120  		if needkeyupdate(t.Key()) {
  1121  			flags |= 8 // need key update
  1122  		}
  1123  		if hashMightPanic(t.Key()) {
  1124  			flags |= 16 // hash might panic
  1125  		}
  1126  		ot = objw.Uint32(lsym, ot, flags)
  1127  		ot = dextratype(lsym, ot, t, 0)
  1128  		if u := t.Underlying(); u != t {
  1129  			// If t is a named map type, also keep the underlying map
  1130  			// type live in the binary. This is important to make sure that
  1131  			// a named map and that same map cast to its underlying type via
  1132  			// reflection, use the same hash function. See issue 37716.
  1133  			r := obj.Addrel(lsym)
  1134  			r.Sym = writeType(u)
  1135  			r.Type = objabi.R_KEEP
  1136  		}
  1137  
  1138  	case types.TPTR:
  1139  		if t.Elem().Kind() == types.TANY {
  1140  			// ../../../../runtime/type.go:/UnsafePointerType
  1141  			ot = dcommontype(lsym, t)
  1142  			ot = dextratype(lsym, ot, t, 0)
  1143  
  1144  			break
  1145  		}
  1146  
  1147  		// ../../../../runtime/type.go:/ptrType
  1148  		s1 := writeType(t.Elem())
  1149  
  1150  		ot = dcommontype(lsym, t)
  1151  		ot = objw.SymPtr(lsym, ot, s1, 0)
  1152  		ot = dextratype(lsym, ot, t, 0)
  1153  
  1154  	// ../../../../runtime/type.go:/structType
  1155  	// for security, only the exported fields.
  1156  	case types.TSTRUCT:
  1157  		fields := t.Fields().Slice()
  1158  		for _, t1 := range fields {
  1159  			writeType(t1.Type)
  1160  		}
  1161  
  1162  		// All non-exported struct field names within a struct
  1163  		// type must originate from a single package. By
  1164  		// identifying and recording that package within the
  1165  		// struct type descriptor, we can omit that
  1166  		// information from the field descriptors.
  1167  		var spkg *types.Pkg
  1168  		for _, f := range fields {
  1169  			if !types.IsExported(f.Sym.Name) {
  1170  				spkg = f.Sym.Pkg
  1171  				break
  1172  			}
  1173  		}
  1174  
  1175  		ot = dcommontype(lsym, t)
  1176  		ot = dgopkgpath(lsym, ot, spkg)
  1177  		ot = objw.SymPtr(lsym, ot, lsym, ot+3*types.PtrSize+uncommonSize(t))
  1178  		ot = objw.Uintptr(lsym, ot, uint64(len(fields)))
  1179  		ot = objw.Uintptr(lsym, ot, uint64(len(fields)))
  1180  
  1181  		dataAdd := len(fields) * structfieldSize()
  1182  		ot = dextratype(lsym, ot, t, dataAdd)
  1183  
  1184  		for _, f := range fields {
  1185  			// ../../../../runtime/type.go:/structField
  1186  			ot = dnameField(lsym, ot, spkg, f)
  1187  			ot = objw.SymPtr(lsym, ot, writeType(f.Type), 0)
  1188  			offsetAnon := uint64(f.Offset) << 1
  1189  			if offsetAnon>>1 != uint64(f.Offset) {
  1190  				base.Fatalf("%v: bad field offset for %s", t, f.Sym.Name)
  1191  			}
  1192  			if f.Embedded != 0 {
  1193  				offsetAnon |= 1
  1194  			}
  1195  			ot = objw.Uintptr(lsym, ot, offsetAnon)
  1196  		}
  1197  	}
  1198  
  1199  	ot = dextratypeData(lsym, ot, t)
  1200  	objw.Global(lsym, int32(ot), int16(obj.DUPOK|obj.RODATA))
  1201  	// Note: DUPOK is required to ensure that we don't end up with more
  1202  	// than one type descriptor for a given type.
  1203  
  1204  	// The linker will leave a table of all the typelinks for
  1205  	// types in the binary, so the runtime can find them.
  1206  	//
  1207  	// When buildmode=shared, all types are in typelinks so the
  1208  	// runtime can deduplicate type pointers.
  1209  	keep := base.Ctxt.Flag_dynlink
  1210  	if !keep && t.Sym() == nil {
  1211  		// For an unnamed type, we only need the link if the type can
  1212  		// be created at run time by reflect.PtrTo and similar
  1213  		// functions. If the type exists in the program, those
  1214  		// functions must return the existing type structure rather
  1215  		// than creating a new one.
  1216  		switch t.Kind() {
  1217  		case types.TPTR, types.TARRAY, types.TCHAN, types.TFUNC, types.TMAP, types.TSLICE, types.TSTRUCT:
  1218  			keep = true
  1219  		}
  1220  	}
  1221  	// Do not put Noalg types in typelinks.  See issue #22605.
  1222  	if types.TypeHasNoAlg(t) {
  1223  		keep = false
  1224  	}
  1225  	lsym.Set(obj.AttrMakeTypelink, keep)
  1226  
  1227  	return lsym
  1228  }
  1229  
  1230  // InterfaceMethodOffset returns the offset of the i-th method in the interface
  1231  // type descriptor, ityp.
  1232  func InterfaceMethodOffset(ityp *types.Type, i int64) int64 {
  1233  	// interface type descriptor layout is struct {
  1234  	//   _type        // commonSize
  1235  	//   pkgpath      // 1 word
  1236  	//   []imethod    // 3 words (pointing to [...]imethod below)
  1237  	//   uncommontype // uncommonSize
  1238  	//   [...]imethod
  1239  	// }
  1240  	// The size of imethod is 8.
  1241  	return int64(commonSize()+4*types.PtrSize+uncommonSize(ityp)) + i*8
  1242  }
  1243  
  1244  // NeedRuntimeType ensures that a runtime type descriptor is emitted for t.
  1245  func NeedRuntimeType(t *types.Type) {
  1246  	if t.HasTParam() {
  1247  		// Generic types don't really exist at run-time and have no runtime
  1248  		// type descriptor.  But we do write out shape types.
  1249  		return
  1250  	}
  1251  	if _, ok := signatset[t]; !ok {
  1252  		signatset[t] = struct{}{}
  1253  		signatslice = append(signatslice, typeAndStr{t: t, short: types.TypeSymName(t), regular: t.String()})
  1254  	}
  1255  }
  1256  
  1257  func WriteRuntimeTypes() {
  1258  	// Process signatslice. Use a loop, as writeType adds
  1259  	// entries to signatslice while it is being processed.
  1260  	for len(signatslice) > 0 {
  1261  		signats := signatslice
  1262  		// Sort for reproducible builds.
  1263  		sort.Sort(typesByString(signats))
  1264  		for _, ts := range signats {
  1265  			t := ts.t
  1266  			writeType(t)
  1267  			if t.Sym() != nil {
  1268  				writeType(types.NewPtr(t))
  1269  			}
  1270  		}
  1271  		signatslice = signatslice[len(signats):]
  1272  	}
  1273  
  1274  	// Emit GC data symbols.
  1275  	gcsyms := make([]typeAndStr, 0, len(gcsymset))
  1276  	for t := range gcsymset {
  1277  		gcsyms = append(gcsyms, typeAndStr{t: t, short: types.TypeSymName(t), regular: t.String()})
  1278  	}
  1279  	sort.Sort(typesByString(gcsyms))
  1280  	for _, ts := range gcsyms {
  1281  		dgcsym(ts.t, true)
  1282  	}
  1283  }
  1284  
  1285  // writeITab writes the itab for concrete type typ implementing interface iface. If
  1286  // allowNonImplement is true, allow the case where typ does not implement iface, and just
  1287  // create a dummy itab with zeroed-out method entries.
  1288  func writeITab(lsym *obj.LSym, typ, iface *types.Type, allowNonImplement bool) {
  1289  	// TODO(mdempsky): Fix methodWrapper, geneq, and genhash (and maybe
  1290  	// others) to stop clobbering these.
  1291  	oldpos, oldfn := base.Pos, ir.CurFunc
  1292  	defer func() { base.Pos, ir.CurFunc = oldpos, oldfn }()
  1293  
  1294  	if typ == nil || (typ.IsPtr() && typ.Elem() == nil) || typ.IsUntyped() || iface == nil || !iface.IsInterface() || iface.IsEmptyInterface() {
  1295  		base.Fatalf("writeITab(%v, %v)", typ, iface)
  1296  	}
  1297  
  1298  	sigs := iface.AllMethods().Slice()
  1299  	entries := make([]*obj.LSym, 0, len(sigs))
  1300  
  1301  	// both sigs and methods are sorted by name,
  1302  	// so we can find the intersection in a single pass
  1303  	for _, m := range methods(typ) {
  1304  		if m.name == sigs[0].Sym {
  1305  			entries = append(entries, m.isym)
  1306  			if m.isym == nil {
  1307  				panic("NO ISYM")
  1308  			}
  1309  			sigs = sigs[1:]
  1310  			if len(sigs) == 0 {
  1311  				break
  1312  			}
  1313  		}
  1314  	}
  1315  	completeItab := len(sigs) == 0
  1316  	if !allowNonImplement && !completeItab {
  1317  		base.Fatalf("incomplete itab")
  1318  	}
  1319  
  1320  	// dump empty itab symbol into i.sym
  1321  	// type itab struct {
  1322  	//   inter  *interfacetype
  1323  	//   _type  *_type
  1324  	//   hash   uint32 // copy of _type.hash. Used for type switches.
  1325  	//   _      [4]byte
  1326  	//   fun    [1]uintptr // variable sized. fun[0]==0 means _type does not implement inter.
  1327  	// }
  1328  	o := objw.SymPtr(lsym, 0, writeType(iface), 0)
  1329  	o = objw.SymPtr(lsym, o, writeType(typ), 0)
  1330  	o = objw.Uint32(lsym, o, types.TypeHash(typ)) // copy of type hash
  1331  	o += 4                                        // skip unused field
  1332  	if !completeItab {
  1333  		// If typ doesn't implement iface, make method entries be zero.
  1334  		o = objw.Uintptr(lsym, o, 0)
  1335  		entries = entries[:0]
  1336  	}
  1337  	for _, fn := range entries {
  1338  		o = objw.SymPtrWeak(lsym, o, fn, 0) // method pointer for each method
  1339  	}
  1340  	// Nothing writes static itabs, so they are read only.
  1341  	objw.Global(lsym, int32(o), int16(obj.DUPOK|obj.RODATA))
  1342  	lsym.Set(obj.AttrContentAddressable, true)
  1343  }
  1344  
  1345  func WriteTabs() {
  1346  	// process ptabs
  1347  	if types.LocalPkg.Name == "main" && len(ptabs) > 0 {
  1348  		ot := 0
  1349  		s := base.Ctxt.Lookup("go.plugin.tabs")
  1350  		for _, p := range ptabs {
  1351  			// Dump ptab symbol into go.pluginsym package.
  1352  			//
  1353  			// type ptab struct {
  1354  			//	name nameOff
  1355  			//	typ  typeOff // pointer to symbol
  1356  			// }
  1357  			nsym := dname(p.Sym().Name, "", nil, true)
  1358  			t := p.Type()
  1359  			if p.Class != ir.PFUNC {
  1360  				t = types.NewPtr(t)
  1361  			}
  1362  			tsym := writeType(t)
  1363  			ot = objw.SymPtrOff(s, ot, nsym)
  1364  			ot = objw.SymPtrOff(s, ot, tsym)
  1365  			// Plugin exports symbols as interfaces. Mark their types
  1366  			// as UsedInIface.
  1367  			tsym.Set(obj.AttrUsedInIface, true)
  1368  		}
  1369  		objw.Global(s, int32(ot), int16(obj.RODATA))
  1370  
  1371  		ot = 0
  1372  		s = base.Ctxt.Lookup("go.plugin.exports")
  1373  		for _, p := range ptabs {
  1374  			ot = objw.SymPtr(s, ot, p.Linksym(), 0)
  1375  		}
  1376  		objw.Global(s, int32(ot), int16(obj.RODATA))
  1377  	}
  1378  }
  1379  
  1380  func WriteImportStrings() {
  1381  	// generate import strings for imported packages
  1382  	for _, p := range types.ImportedPkgList() {
  1383  		dimportpath(p)
  1384  	}
  1385  }
  1386  
  1387  func WriteBasicTypes() {
  1388  	// do basic types if compiling package runtime.
  1389  	// they have to be in at least one package,
  1390  	// and runtime is always loaded implicitly,
  1391  	// so this is as good as any.
  1392  	// another possible choice would be package main,
  1393  	// but using runtime means fewer copies in object files.
  1394  	if base.Ctxt.Pkgpath == "runtime" {
  1395  		for i := types.Kind(1); i <= types.TBOOL; i++ {
  1396  			writeType(types.NewPtr(types.Types[i]))
  1397  		}
  1398  		writeType(types.NewPtr(types.Types[types.TSTRING]))
  1399  		writeType(types.NewPtr(types.Types[types.TUNSAFEPTR]))
  1400  		if base.Flag.G > 0 {
  1401  			writeType(types.AnyType)
  1402  		}
  1403  
  1404  		// emit type structs for error and func(error) string.
  1405  		// The latter is the type of an auto-generated wrapper.
  1406  		writeType(types.NewPtr(types.ErrorType))
  1407  
  1408  		writeType(types.NewSignature(types.NoPkg, nil, nil, []*types.Field{
  1409  			types.NewField(base.Pos, nil, types.ErrorType),
  1410  		}, []*types.Field{
  1411  			types.NewField(base.Pos, nil, types.Types[types.TSTRING]),
  1412  		}))
  1413  
  1414  		// add paths for runtime and main, which 6l imports implicitly.
  1415  		dimportpath(ir.Pkgs.Runtime)
  1416  
  1417  		if base.Flag.Race {
  1418  			dimportpath(types.NewPkg("runtime/race", ""))
  1419  		}
  1420  		if base.Flag.MSan {
  1421  			dimportpath(types.NewPkg("runtime/msan", ""))
  1422  		}
  1423  		if base.Flag.ASan {
  1424  			dimportpath(types.NewPkg("runtime/asan", ""))
  1425  		}
  1426  
  1427  		dimportpath(types.NewPkg("main", ""))
  1428  	}
  1429  }
  1430  
  1431  type typeAndStr struct {
  1432  	t       *types.Type
  1433  	short   string // "short" here means TypeSymName
  1434  	regular string
  1435  }
  1436  
  1437  type typesByString []typeAndStr
  1438  
  1439  func (a typesByString) Len() int { return len(a) }
  1440  func (a typesByString) Less(i, j int) bool {
  1441  	if a[i].short != a[j].short {
  1442  		return a[i].short < a[j].short
  1443  	}
  1444  	// When the only difference between the types is whether
  1445  	// they refer to byte or uint8, such as **byte vs **uint8,
  1446  	// the types' NameStrings can be identical.
  1447  	// To preserve deterministic sort ordering, sort these by String().
  1448  	//
  1449  	// TODO(mdempsky): This all seems suspect. Using LinkString would
  1450  	// avoid naming collisions, and there shouldn't be a reason to care
  1451  	// about "byte" vs "uint8": they share the same runtime type
  1452  	// descriptor anyway.
  1453  	if a[i].regular != a[j].regular {
  1454  		return a[i].regular < a[j].regular
  1455  	}
  1456  	// Identical anonymous interfaces defined in different locations
  1457  	// will be equal for the above checks, but different in DWARF output.
  1458  	// Sort by source position to ensure deterministic order.
  1459  	// See issues 27013 and 30202.
  1460  	if a[i].t.Kind() == types.TINTER && a[i].t.AllMethods().Len() > 0 {
  1461  		return a[i].t.AllMethods().Index(0).Pos.Before(a[j].t.AllMethods().Index(0).Pos)
  1462  	}
  1463  	return false
  1464  }
  1465  func (a typesByString) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
  1466  
  1467  // maxPtrmaskBytes is the maximum length of a GC ptrmask bitmap,
  1468  // which holds 1-bit entries describing where pointers are in a given type.
  1469  // Above this length, the GC information is recorded as a GC program,
  1470  // which can express repetition compactly. In either form, the
  1471  // information is used by the runtime to initialize the heap bitmap,
  1472  // and for large types (like 128 or more words), they are roughly the
  1473  // same speed. GC programs are never much larger and often more
  1474  // compact. (If large arrays are involved, they can be arbitrarily
  1475  // more compact.)
  1476  //
  1477  // The cutoff must be large enough that any allocation large enough to
  1478  // use a GC program is large enough that it does not share heap bitmap
  1479  // bytes with any other objects, allowing the GC program execution to
  1480  // assume an aligned start and not use atomic operations. In the current
  1481  // runtime, this means all malloc size classes larger than the cutoff must
  1482  // be multiples of four words. On 32-bit systems that's 16 bytes, and
  1483  // all size classes >= 16 bytes are 16-byte aligned, so no real constraint.
  1484  // On 64-bit systems, that's 32 bytes, and 32-byte alignment is guaranteed
  1485  // for size classes >= 256 bytes. On a 64-bit system, 256 bytes allocated
  1486  // is 32 pointers, the bits for which fit in 4 bytes. So maxPtrmaskBytes
  1487  // must be >= 4.
  1488  //
  1489  // We used to use 16 because the GC programs do have some constant overhead
  1490  // to get started, and processing 128 pointers seems to be enough to
  1491  // amortize that overhead well.
  1492  //
  1493  // To make sure that the runtime's chansend can call typeBitsBulkBarrier,
  1494  // we raised the limit to 2048, so that even 32-bit systems are guaranteed to
  1495  // use bitmaps for objects up to 64 kB in size.
  1496  //
  1497  // Also known to reflect/type.go.
  1498  //
  1499  const maxPtrmaskBytes = 2048
  1500  
  1501  // GCSym returns a data symbol containing GC information for type t, along
  1502  // with a boolean reporting whether the UseGCProg bit should be set in the
  1503  // type kind, and the ptrdata field to record in the reflect type information.
  1504  // GCSym may be called in concurrent backend, so it does not emit the symbol
  1505  // content.
  1506  func GCSym(t *types.Type) (lsym *obj.LSym, useGCProg bool, ptrdata int64) {
  1507  	// Record that we need to emit the GC symbol.
  1508  	gcsymmu.Lock()
  1509  	if _, ok := gcsymset[t]; !ok {
  1510  		gcsymset[t] = struct{}{}
  1511  	}
  1512  	gcsymmu.Unlock()
  1513  
  1514  	return dgcsym(t, false)
  1515  }
  1516  
  1517  // dgcsym returns a data symbol containing GC information for type t, along
  1518  // with a boolean reporting whether the UseGCProg bit should be set in the
  1519  // type kind, and the ptrdata field to record in the reflect type information.
  1520  // When write is true, it writes the symbol data.
  1521  func dgcsym(t *types.Type, write bool) (lsym *obj.LSym, useGCProg bool, ptrdata int64) {
  1522  	ptrdata = types.PtrDataSize(t)
  1523  	if ptrdata/int64(types.PtrSize) <= maxPtrmaskBytes*8 {
  1524  		lsym = dgcptrmask(t, write)
  1525  		return
  1526  	}
  1527  
  1528  	useGCProg = true
  1529  	lsym, ptrdata = dgcprog(t, write)
  1530  	return
  1531  }
  1532  
  1533  // dgcptrmask emits and returns the symbol containing a pointer mask for type t.
  1534  func dgcptrmask(t *types.Type, write bool) *obj.LSym {
  1535  	ptrmask := make([]byte, (types.PtrDataSize(t)/int64(types.PtrSize)+7)/8)
  1536  	fillptrmask(t, ptrmask)
  1537  	p := fmt.Sprintf("runtime.gcbits.%x", ptrmask)
  1538  
  1539  	lsym := base.Ctxt.Lookup(p)
  1540  	if write && !lsym.OnList() {
  1541  		for i, x := range ptrmask {
  1542  			objw.Uint8(lsym, i, x)
  1543  		}
  1544  		objw.Global(lsym, int32(len(ptrmask)), obj.DUPOK|obj.RODATA|obj.LOCAL)
  1545  		lsym.Set(obj.AttrContentAddressable, true)
  1546  	}
  1547  	return lsym
  1548  }
  1549  
  1550  // fillptrmask fills in ptrmask with 1s corresponding to the
  1551  // word offsets in t that hold pointers.
  1552  // ptrmask is assumed to fit at least types.PtrDataSize(t)/PtrSize bits.
  1553  func fillptrmask(t *types.Type, ptrmask []byte) {
  1554  	for i := range ptrmask {
  1555  		ptrmask[i] = 0
  1556  	}
  1557  	if !t.HasPointers() {
  1558  		return
  1559  	}
  1560  
  1561  	vec := bitvec.New(8 * int32(len(ptrmask)))
  1562  	typebits.Set(t, 0, vec)
  1563  
  1564  	nptr := types.PtrDataSize(t) / int64(types.PtrSize)
  1565  	for i := int64(0); i < nptr; i++ {
  1566  		if vec.Get(int32(i)) {
  1567  			ptrmask[i/8] |= 1 << (uint(i) % 8)
  1568  		}
  1569  	}
  1570  }
  1571  
  1572  // dgcprog emits and returns the symbol containing a GC program for type t
  1573  // along with the size of the data described by the program (in the range
  1574  // [types.PtrDataSize(t), t.Width]).
  1575  // In practice, the size is types.PtrDataSize(t) except for non-trivial arrays.
  1576  // For non-trivial arrays, the program describes the full t.Width size.
  1577  func dgcprog(t *types.Type, write bool) (*obj.LSym, int64) {
  1578  	types.CalcSize(t)
  1579  	if t.Size() == types.BADWIDTH {
  1580  		base.Fatalf("dgcprog: %v badwidth", t)
  1581  	}
  1582  	lsym := TypeLinksymPrefix(".gcprog", t)
  1583  	var p gcProg
  1584  	p.init(lsym, write)
  1585  	p.emit(t, 0)
  1586  	offset := p.w.BitIndex() * int64(types.PtrSize)
  1587  	p.end()
  1588  	if ptrdata := types.PtrDataSize(t); offset < ptrdata || offset > t.Size() {
  1589  		base.Fatalf("dgcprog: %v: offset=%d but ptrdata=%d size=%d", t, offset, ptrdata, t.Size())
  1590  	}
  1591  	return lsym, offset
  1592  }
  1593  
  1594  type gcProg struct {
  1595  	lsym   *obj.LSym
  1596  	symoff int
  1597  	w      gcprog.Writer
  1598  	write  bool
  1599  }
  1600  
  1601  func (p *gcProg) init(lsym *obj.LSym, write bool) {
  1602  	p.lsym = lsym
  1603  	p.write = write && !lsym.OnList()
  1604  	p.symoff = 4 // first 4 bytes hold program length
  1605  	if !write {
  1606  		p.w.Init(func(byte) {})
  1607  		return
  1608  	}
  1609  	p.w.Init(p.writeByte)
  1610  	if base.Debug.GCProg > 0 {
  1611  		fmt.Fprintf(os.Stderr, "compile: start GCProg for %v\n", lsym)
  1612  		p.w.Debug(os.Stderr)
  1613  	}
  1614  }
  1615  
  1616  func (p *gcProg) writeByte(x byte) {
  1617  	p.symoff = objw.Uint8(p.lsym, p.symoff, x)
  1618  }
  1619  
  1620  func (p *gcProg) end() {
  1621  	p.w.End()
  1622  	if !p.write {
  1623  		return
  1624  	}
  1625  	objw.Uint32(p.lsym, 0, uint32(p.symoff-4))
  1626  	objw.Global(p.lsym, int32(p.symoff), obj.DUPOK|obj.RODATA|obj.LOCAL)
  1627  	p.lsym.Set(obj.AttrContentAddressable, true)
  1628  	if base.Debug.GCProg > 0 {
  1629  		fmt.Fprintf(os.Stderr, "compile: end GCProg for %v\n", p.lsym)
  1630  	}
  1631  }
  1632  
  1633  func (p *gcProg) emit(t *types.Type, offset int64) {
  1634  	types.CalcSize(t)
  1635  	if !t.HasPointers() {
  1636  		return
  1637  	}
  1638  	if t.Size() == int64(types.PtrSize) {
  1639  		p.w.Ptr(offset / int64(types.PtrSize))
  1640  		return
  1641  	}
  1642  	switch t.Kind() {
  1643  	default:
  1644  		base.Fatalf("gcProg.emit: unexpected type %v", t)
  1645  
  1646  	case types.TSTRING:
  1647  		p.w.Ptr(offset / int64(types.PtrSize))
  1648  
  1649  	case types.TINTER:
  1650  		// Note: the first word isn't a pointer. See comment in typebits.Set
  1651  		p.w.Ptr(offset/int64(types.PtrSize) + 1)
  1652  
  1653  	case types.TSLICE:
  1654  		p.w.Ptr(offset / int64(types.PtrSize))
  1655  
  1656  	case types.TARRAY:
  1657  		if t.NumElem() == 0 {
  1658  			// should have been handled by haspointers check above
  1659  			base.Fatalf("gcProg.emit: empty array")
  1660  		}
  1661  
  1662  		// Flatten array-of-array-of-array to just a big array by multiplying counts.
  1663  		count := t.NumElem()
  1664  		elem := t.Elem()
  1665  		for elem.IsArray() {
  1666  			count *= elem.NumElem()
  1667  			elem = elem.Elem()
  1668  		}
  1669  
  1670  		if !p.w.ShouldRepeat(elem.Size()/int64(types.PtrSize), count) {
  1671  			// Cheaper to just emit the bits.
  1672  			for i := int64(0); i < count; i++ {
  1673  				p.emit(elem, offset+i*elem.Size())
  1674  			}
  1675  			return
  1676  		}
  1677  		p.emit(elem, offset)
  1678  		p.w.ZeroUntil((offset + elem.Size()) / int64(types.PtrSize))
  1679  		p.w.Repeat(elem.Size()/int64(types.PtrSize), count-1)
  1680  
  1681  	case types.TSTRUCT:
  1682  		for _, t1 := range t.Fields().Slice() {
  1683  			p.emit(t1.Type, offset+t1.Offset)
  1684  		}
  1685  	}
  1686  }
  1687  
  1688  // ZeroAddr returns the address of a symbol with at least
  1689  // size bytes of zeros.
  1690  func ZeroAddr(size int64) ir.Node {
  1691  	if size >= 1<<31 {
  1692  		base.Fatalf("map elem too big %d", size)
  1693  	}
  1694  	if ZeroSize < size {
  1695  		ZeroSize = size
  1696  	}
  1697  	lsym := base.PkgLinksym("go.map", "zero", obj.ABI0)
  1698  	x := ir.NewLinksymExpr(base.Pos, lsym, types.Types[types.TUINT8])
  1699  	return typecheck.Expr(typecheck.NodAddr(x))
  1700  }
  1701  
  1702  func CollectPTabs() {
  1703  	if !base.Ctxt.Flag_dynlink || types.LocalPkg.Name != "main" {
  1704  		return
  1705  	}
  1706  	for _, exportn := range typecheck.Target.Exports {
  1707  		s := exportn.Sym()
  1708  		nn := ir.AsNode(s.Def)
  1709  		if nn == nil {
  1710  			continue
  1711  		}
  1712  		if nn.Op() != ir.ONAME {
  1713  			continue
  1714  		}
  1715  		n := nn.(*ir.Name)
  1716  		if !types.IsExported(s.Name) {
  1717  			continue
  1718  		}
  1719  		if s.Pkg.Name != "main" {
  1720  			continue
  1721  		}
  1722  		ptabs = append(ptabs, n)
  1723  	}
  1724  }
  1725  
  1726  // NeedEmit reports whether typ is a type that we need to emit code
  1727  // for (e.g., runtime type descriptors, method wrappers).
  1728  func NeedEmit(typ *types.Type) bool {
  1729  	// TODO(mdempsky): Export data should keep track of which anonymous
  1730  	// and instantiated types were emitted, so at least downstream
  1731  	// packages can skip re-emitting them.
  1732  	//
  1733  	// Perhaps we can just generalize the linker-symbol indexing to
  1734  	// track the index of arbitrary types, not just defined types, and
  1735  	// use its presence to detect this. The same idea would work for
  1736  	// instantiated generic functions too.
  1737  
  1738  	switch sym := typ.Sym(); {
  1739  	case sym == nil:
  1740  		// Anonymous type; possibly never seen before or ever again.
  1741  		// Need to emit to be safe (however, see TODO above).
  1742  		return true
  1743  
  1744  	case sym.Pkg == types.LocalPkg:
  1745  		// Local defined type; our responsibility.
  1746  		return true
  1747  
  1748  	case base.Ctxt.Pkgpath == "runtime" && (sym.Pkg == types.BuiltinPkg || sym.Pkg == types.UnsafePkg):
  1749  		// Package runtime is responsible for including code for builtin
  1750  		// types (predeclared and package unsafe).
  1751  		return true
  1752  
  1753  	case typ.IsFullyInstantiated():
  1754  		// Instantiated type; possibly instantiated with unique type arguments.
  1755  		// Need to emit to be safe (however, see TODO above).
  1756  		return true
  1757  
  1758  	case typ.HasShape():
  1759  		// Shape type; need to emit even though it lives in the .shape package.
  1760  		// TODO: make sure the linker deduplicates them (see dupok in writeType above).
  1761  		return true
  1762  
  1763  	default:
  1764  		// Should have been emitted by an imported package.
  1765  		return false
  1766  	}
  1767  }
  1768  
  1769  // Generate a wrapper function to convert from
  1770  // a receiver of type T to a receiver of type U.
  1771  // That is,
  1772  //
  1773  //	func (t T) M() {
  1774  //		...
  1775  //	}
  1776  //
  1777  // already exists; this function generates
  1778  //
  1779  //	func (u U) M() {
  1780  //		u.M()
  1781  //	}
  1782  //
  1783  // where the types T and U are such that u.M() is valid
  1784  // and calls the T.M method.
  1785  // The resulting function is for use in method tables.
  1786  //
  1787  //	rcvr - U
  1788  //	method - M func (t T)(), a TFIELD type struct
  1789  //
  1790  // Also wraps methods on instantiated generic types for use in itab entries.
  1791  // For an instantiated generic type G[int], we generate wrappers like:
  1792  // G[int] pointer shaped:
  1793  //	func (x G[int]) f(arg) {
  1794  //		.inst.G[int].f(dictionary, x, arg)
  1795  // 	}
  1796  // G[int] not pointer shaped:
  1797  //	func (x *G[int]) f(arg) {
  1798  //		.inst.G[int].f(dictionary, *x, arg)
  1799  // 	}
  1800  // These wrappers are always fully stenciled.
  1801  func methodWrapper(rcvr *types.Type, method *types.Field, forItab bool) *obj.LSym {
  1802  	orig := rcvr
  1803  	if forItab && !types.IsDirectIface(rcvr) {
  1804  		rcvr = rcvr.PtrTo()
  1805  	}
  1806  
  1807  	generic := false
  1808  	// We don't need a dictionary if we are reaching a method (possibly via an
  1809  	// embedded field) which is an interface method.
  1810  	if !types.IsInterfaceMethod(method.Type) {
  1811  		rcvr1 := deref(rcvr)
  1812  		if len(rcvr1.RParams()) > 0 {
  1813  			// If rcvr has rparams, remember method as generic, which
  1814  			// means we need to add a dictionary to the wrapper.
  1815  			generic = true
  1816  			if rcvr.HasShape() {
  1817  				base.Fatalf("method on type instantiated with shapes, rcvr:%+v", rcvr)
  1818  			}
  1819  		}
  1820  	}
  1821  
  1822  	newnam := ir.MethodSym(rcvr, method.Sym)
  1823  	lsym := newnam.Linksym()
  1824  	if newnam.Siggen() {
  1825  		return lsym
  1826  	}
  1827  	newnam.SetSiggen(true)
  1828  
  1829  	// Except in quirks mode, unified IR creates its own wrappers.
  1830  	if base.Debug.Unified != 0 && base.Debug.UnifiedQuirks == 0 {
  1831  		return lsym
  1832  	}
  1833  
  1834  	methodrcvr := method.Type.Recv().Type
  1835  	// For generic methods, we need to generate the wrapper even if the receiver
  1836  	// types are identical, because we want to add the dictionary.
  1837  	if !generic && types.Identical(rcvr, methodrcvr) {
  1838  		return lsym
  1839  	}
  1840  
  1841  	if !NeedEmit(rcvr) || rcvr.IsPtr() && !NeedEmit(rcvr.Elem()) {
  1842  		return lsym
  1843  	}
  1844  
  1845  	base.Pos = base.AutogeneratedPos
  1846  	typecheck.DeclContext = ir.PEXTERN
  1847  
  1848  	tfn := ir.NewFuncType(base.Pos,
  1849  		ir.NewField(base.Pos, typecheck.Lookup(".this"), nil, rcvr),
  1850  		typecheck.NewFuncParams(method.Type.Params(), true),
  1851  		typecheck.NewFuncParams(method.Type.Results(), false))
  1852  
  1853  	// TODO(austin): SelectorExpr may have created one or more
  1854  	// ir.Names for these already with a nil Func field. We should
  1855  	// consolidate these and always attach a Func to the Name.
  1856  	fn := typecheck.DeclFunc(newnam, tfn)
  1857  	fn.SetDupok(true)
  1858  
  1859  	nthis := ir.AsNode(tfn.Type().Recv().Nname)
  1860  
  1861  	indirect := rcvr.IsPtr() && rcvr.Elem() == methodrcvr
  1862  
  1863  	// generate nil pointer check for better error
  1864  	if indirect {
  1865  		// generating wrapper from *T to T.
  1866  		n := ir.NewIfStmt(base.Pos, nil, nil, nil)
  1867  		n.Cond = ir.NewBinaryExpr(base.Pos, ir.OEQ, nthis, typecheck.NodNil())
  1868  		call := ir.NewCallExpr(base.Pos, ir.OCALL, typecheck.LookupRuntime("panicwrap"), nil)
  1869  		n.Body = []ir.Node{call}
  1870  		fn.Body.Append(n)
  1871  	}
  1872  
  1873  	dot := typecheck.AddImplicitDots(ir.NewSelectorExpr(base.Pos, ir.OXDOT, nthis, method.Sym))
  1874  	// generate call
  1875  	// It's not possible to use a tail call when dynamic linking on ppc64le. The
  1876  	// bad scenario is when a local call is made to the wrapper: the wrapper will
  1877  	// call the implementation, which might be in a different module and so set
  1878  	// the TOC to the appropriate value for that module. But if it returns
  1879  	// directly to the wrapper's caller, nothing will reset it to the correct
  1880  	// value for that function.
  1881  	if !base.Flag.Cfg.Instrumenting && rcvr.IsPtr() && methodrcvr.IsPtr() && method.Embedded != 0 && !types.IsInterfaceMethod(method.Type) && !(base.Ctxt.Arch.Name == "ppc64le" && base.Ctxt.Flag_dynlink) && !generic {
  1882  		call := ir.NewCallExpr(base.Pos, ir.OCALL, dot, nil)
  1883  		call.Args = ir.ParamNames(tfn.Type())
  1884  		call.IsDDD = tfn.Type().IsVariadic()
  1885  		fn.Body.Append(ir.NewTailCallStmt(base.Pos, call))
  1886  	} else {
  1887  		fn.SetWrapper(true) // ignore frame for panic+recover matching
  1888  		var call *ir.CallExpr
  1889  
  1890  		if generic && dot.X != nthis {
  1891  			// If there is embedding involved, then we should do the
  1892  			// normal non-generic embedding wrapper below, which calls
  1893  			// the wrapper for the real receiver type using dot as an
  1894  			// argument. There is no need for generic processing (adding
  1895  			// a dictionary) for this wrapper.
  1896  			generic = false
  1897  		}
  1898  
  1899  		if generic {
  1900  			targs := deref(rcvr).RParams()
  1901  			// The wrapper for an auto-generated pointer/non-pointer
  1902  			// receiver method should share the same dictionary as the
  1903  			// corresponding original (user-written) method.
  1904  			baseOrig := orig
  1905  			if baseOrig.IsPtr() && !methodrcvr.IsPtr() {
  1906  				baseOrig = baseOrig.Elem()
  1907  			} else if !baseOrig.IsPtr() && methodrcvr.IsPtr() {
  1908  				baseOrig = types.NewPtr(baseOrig)
  1909  			}
  1910  			args := []ir.Node{getDictionary(ir.MethodSym(baseOrig, method.Sym), targs)}
  1911  			if indirect {
  1912  				args = append(args, ir.NewStarExpr(base.Pos, dot.X))
  1913  			} else if methodrcvr.IsPtr() && methodrcvr.Elem() == dot.X.Type() {
  1914  				// Case where method call is via a non-pointer
  1915  				// embedded field with a pointer method.
  1916  				args = append(args, typecheck.NodAddrAt(base.Pos, dot.X))
  1917  			} else {
  1918  				args = append(args, dot.X)
  1919  			}
  1920  			args = append(args, ir.ParamNames(tfn.Type())...)
  1921  
  1922  			// Target method uses shaped names.
  1923  			targs2 := make([]*types.Type, len(targs))
  1924  			origRParams := deref(orig).OrigType().RParams()
  1925  			for i, t := range targs {
  1926  				targs2[i] = typecheck.Shapify(t, i, origRParams[i])
  1927  			}
  1928  			targs = targs2
  1929  
  1930  			sym := typecheck.MakeFuncInstSym(ir.MethodSym(methodrcvr, method.Sym), targs, false, true)
  1931  			if sym.Def == nil {
  1932  				// Currently we make sure that we have all the
  1933  				// instantiations we need by generating them all in
  1934  				// ../noder/stencil.go:instantiateMethods
  1935  				// Extra instantiations because of an inlined function
  1936  				// should have been exported, and so available via
  1937  				// Resolve.
  1938  				in := typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
  1939  				if in.Op() == ir.ONONAME {
  1940  					base.Fatalf("instantiation %s not found", sym.Name)
  1941  				}
  1942  				sym = in.Sym()
  1943  			}
  1944  			target := ir.AsNode(sym.Def)
  1945  			call = ir.NewCallExpr(base.Pos, ir.OCALL, target, args)
  1946  			// Fill-in the generic method node that was not filled in
  1947  			// in instantiateMethod.
  1948  			method.Nname = fn.Nname
  1949  		} else {
  1950  			call = ir.NewCallExpr(base.Pos, ir.OCALL, dot, nil)
  1951  			call.Args = ir.ParamNames(tfn.Type())
  1952  		}
  1953  		call.IsDDD = tfn.Type().IsVariadic()
  1954  		if method.Type.NumResults() > 0 {
  1955  			ret := ir.NewReturnStmt(base.Pos, nil)
  1956  			ret.Results = []ir.Node{call}
  1957  			fn.Body.Append(ret)
  1958  		} else {
  1959  			fn.Body.Append(call)
  1960  		}
  1961  	}
  1962  
  1963  	typecheck.FinishFuncBody()
  1964  	if base.Debug.DclStack != 0 {
  1965  		types.CheckDclstack()
  1966  	}
  1967  
  1968  	typecheck.Func(fn)
  1969  	ir.CurFunc = fn
  1970  	typecheck.Stmts(fn.Body)
  1971  
  1972  	if AfterGlobalEscapeAnalysis {
  1973  		inline.InlineCalls(fn)
  1974  		escape.Batch([]*ir.Func{fn}, false)
  1975  	}
  1976  
  1977  	ir.CurFunc = nil
  1978  	typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
  1979  
  1980  	return lsym
  1981  }
  1982  
  1983  // AfterGlobalEscapeAnalysis tracks whether package gc has already
  1984  // performed the main, global escape analysis pass. If so,
  1985  // methodWrapper takes responsibility for escape analyzing any
  1986  // generated wrappers.
  1987  var AfterGlobalEscapeAnalysis bool
  1988  
  1989  var ZeroSize int64
  1990  
  1991  // MarkTypeUsedInInterface marks that type t is converted to an interface.
  1992  // This information is used in the linker in dead method elimination.
  1993  func MarkTypeUsedInInterface(t *types.Type, from *obj.LSym) {
  1994  	if t.HasShape() {
  1995  		// Shape types shouldn't be put in interfaces, so we shouldn't ever get here.
  1996  		base.Fatalf("shape types have no methods %+v", t)
  1997  	}
  1998  	tsym := TypeLinksym(t)
  1999  	// Emit a marker relocation. The linker will know the type is converted
  2000  	// to an interface if "from" is reachable.
  2001  	r := obj.Addrel(from)
  2002  	r.Sym = tsym
  2003  	r.Type = objabi.R_USEIFACE
  2004  }
  2005  
  2006  // MarkUsedIfaceMethod marks that an interface method is used in the current
  2007  // function. n is OCALLINTER node.
  2008  func MarkUsedIfaceMethod(n *ir.CallExpr) {
  2009  	// skip unnamed functions (func _())
  2010  	if ir.CurFunc.LSym == nil {
  2011  		return
  2012  	}
  2013  	dot := n.X.(*ir.SelectorExpr)
  2014  	ityp := dot.X.Type()
  2015  	if ityp.HasShape() {
  2016  		// Here we're calling a method on a generic interface. Something like:
  2017  		//
  2018  		// type I[T any] interface { foo() T }
  2019  		// func f[T any](x I[T]) {
  2020  		//     ... = x.foo()
  2021  		// }
  2022  		// f[int](...)
  2023  		// f[string](...)
  2024  		//
  2025  		// In this case, in f we're calling foo on a generic interface.
  2026  		// Which method could that be? Normally we could match the method
  2027  		// both by name and by type. But in this case we don't really know
  2028  		// the type of the method we're calling. It could be func()int
  2029  		// or func()string. So we match on just the function name, instead
  2030  		// of both the name and the type used for the non-generic case below.
  2031  		// TODO: instantiations at least know the shape of the instantiated
  2032  		// type, and the linker could do more complicated matching using
  2033  		// some sort of fuzzy shape matching. For now, only use the name
  2034  		// of the method for matching.
  2035  		r := obj.Addrel(ir.CurFunc.LSym)
  2036  		// We use a separate symbol just to tell the linker the method name.
  2037  		// (The symbol itself is not needed in the final binary.)
  2038  		r.Sym = staticdata.StringSym(src.NoXPos, dot.Sel.Name)
  2039  		r.Type = objabi.R_USEGENERICIFACEMETHOD
  2040  		return
  2041  	}
  2042  
  2043  	tsym := TypeLinksym(ityp)
  2044  	r := obj.Addrel(ir.CurFunc.LSym)
  2045  	r.Sym = tsym
  2046  	// dot.Offset() is the method index * PtrSize (the offset of code pointer
  2047  	// in itab).
  2048  	midx := dot.Offset() / int64(types.PtrSize)
  2049  	r.Add = InterfaceMethodOffset(ityp, midx)
  2050  	r.Type = objabi.R_USEIFACEMETHOD
  2051  }
  2052  
  2053  // getDictionary returns the dictionary for the given named generic function
  2054  // or method, with the given type arguments.
  2055  func getDictionary(gf *types.Sym, targs []*types.Type) ir.Node {
  2056  	if len(targs) == 0 {
  2057  		base.Fatalf("%s should have type arguments", gf.Name)
  2058  	}
  2059  	for _, t := range targs {
  2060  		if t.HasShape() {
  2061  			base.Fatalf("dictionary for %s should only use concrete types: %+v", gf.Name, t)
  2062  		}
  2063  	}
  2064  
  2065  	sym := typecheck.MakeDictSym(gf, targs, true)
  2066  
  2067  	// Dictionary should already have been generated by instantiateMethods().
  2068  	// Extra dictionaries needed because of an inlined function should have been
  2069  	// exported, and so available via Resolve.
  2070  	if lsym := sym.Linksym(); len(lsym.P) == 0 {
  2071  		in := typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
  2072  		if in.Op() == ir.ONONAME {
  2073  			base.Fatalf("Dictionary should have already been generated: %s.%s", sym.Pkg.Path, sym.Name)
  2074  		}
  2075  		sym = in.Sym()
  2076  	}
  2077  
  2078  	// Make (or reuse) a node referencing the dictionary symbol.
  2079  	var n *ir.Name
  2080  	if sym.Def != nil {
  2081  		n = sym.Def.(*ir.Name)
  2082  	} else {
  2083  		n = typecheck.NewName(sym)
  2084  		n.SetType(types.Types[types.TUINTPTR]) // should probably be [...]uintptr, but doesn't really matter
  2085  		n.SetTypecheck(1)
  2086  		n.Class = ir.PEXTERN
  2087  		sym.Def = n
  2088  	}
  2089  
  2090  	// Return the address of the dictionary.
  2091  	np := typecheck.NodAddr(n)
  2092  	// Note: treat dictionary pointers as uintptrs, so they aren't pointers
  2093  	// with respect to GC. That saves on stack scanning work, write barriers, etc.
  2094  	// We can get away with it because dictionaries are global variables.
  2095  	np.SetType(types.Types[types.TUINTPTR])
  2096  	np.SetTypecheck(1)
  2097  	return np
  2098  }
  2099  
  2100  func deref(t *types.Type) *types.Type {
  2101  	if t.IsPtr() {
  2102  		return t.Elem()
  2103  	}
  2104  	return t
  2105  }
  2106  

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