Source file src/cmd/compile/internal/noder/reader.go

     1  // Copyright 2021 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 noder
     6  
     7  import (
     8  	"encoding/hex"
     9  	"fmt"
    10  	"go/constant"
    11  	"internal/buildcfg"
    12  	"internal/pkgbits"
    13  	"path/filepath"
    14  	"strings"
    15  
    16  	"cmd/compile/internal/base"
    17  	"cmd/compile/internal/dwarfgen"
    18  	"cmd/compile/internal/inline"
    19  	"cmd/compile/internal/inline/interleaved"
    20  	"cmd/compile/internal/ir"
    21  	"cmd/compile/internal/objw"
    22  	"cmd/compile/internal/reflectdata"
    23  	"cmd/compile/internal/staticinit"
    24  	"cmd/compile/internal/typecheck"
    25  	"cmd/compile/internal/types"
    26  	"cmd/internal/notsha256"
    27  	"cmd/internal/obj"
    28  	"cmd/internal/objabi"
    29  	"cmd/internal/src"
    30  )
    31  
    32  // This file implements cmd/compile backend's reader for the Unified
    33  // IR export data.
    34  
    35  // A pkgReader reads Unified IR export data.
    36  type pkgReader struct {
    37  	pkgbits.PkgDecoder
    38  
    39  	// Indices for encoded things; lazily populated as needed.
    40  	//
    41  	// Note: Objects (i.e., ir.Names) are lazily instantiated by
    42  	// populating their types.Sym.Def; see objReader below.
    43  
    44  	posBases []*src.PosBase
    45  	pkgs     []*types.Pkg
    46  	typs     []*types.Type
    47  
    48  	// offset for rewriting the given (absolute!) index into the output,
    49  	// but bitwise inverted so we can detect if we're missing the entry
    50  	// or not.
    51  	newindex []pkgbits.Index
    52  }
    53  
    54  func newPkgReader(pr pkgbits.PkgDecoder) *pkgReader {
    55  	return &pkgReader{
    56  		PkgDecoder: pr,
    57  
    58  		posBases: make([]*src.PosBase, pr.NumElems(pkgbits.RelocPosBase)),
    59  		pkgs:     make([]*types.Pkg, pr.NumElems(pkgbits.RelocPkg)),
    60  		typs:     make([]*types.Type, pr.NumElems(pkgbits.RelocType)),
    61  
    62  		newindex: make([]pkgbits.Index, pr.TotalElems()),
    63  	}
    64  }
    65  
    66  // A pkgReaderIndex compactly identifies an index (and its
    67  // corresponding dictionary) within a package's export data.
    68  type pkgReaderIndex struct {
    69  	pr        *pkgReader
    70  	idx       pkgbits.Index
    71  	dict      *readerDict
    72  	methodSym *types.Sym
    73  
    74  	synthetic func(pos src.XPos, r *reader)
    75  }
    76  
    77  func (pri pkgReaderIndex) asReader(k pkgbits.RelocKind, marker pkgbits.SyncMarker) *reader {
    78  	if pri.synthetic != nil {
    79  		return &reader{synthetic: pri.synthetic}
    80  	}
    81  
    82  	r := pri.pr.newReader(k, pri.idx, marker)
    83  	r.dict = pri.dict
    84  	r.methodSym = pri.methodSym
    85  	return r
    86  }
    87  
    88  func (pr *pkgReader) newReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
    89  	return &reader{
    90  		Decoder: pr.NewDecoder(k, idx, marker),
    91  		p:       pr,
    92  	}
    93  }
    94  
    95  // A reader provides APIs for reading an individual element.
    96  type reader struct {
    97  	pkgbits.Decoder
    98  
    99  	p *pkgReader
   100  
   101  	dict *readerDict
   102  
   103  	// TODO(mdempsky): The state below is all specific to reading
   104  	// function bodies. It probably makes sense to split it out
   105  	// separately so that it doesn't take up space in every reader
   106  	// instance.
   107  
   108  	curfn       *ir.Func
   109  	locals      []*ir.Name
   110  	closureVars []*ir.Name
   111  
   112  	// funarghack is used during inlining to suppress setting
   113  	// Field.Nname to the inlined copies of the parameters. This is
   114  	// necessary because we reuse the same types.Type as the original
   115  	// function, and most of the compiler still relies on field.Nname to
   116  	// find parameters/results.
   117  	funarghack bool
   118  
   119  	// methodSym is the name of method's name, if reading a method.
   120  	// It's nil if reading a normal function or closure body.
   121  	methodSym *types.Sym
   122  
   123  	// dictParam is the .dict param, if any.
   124  	dictParam *ir.Name
   125  
   126  	// synthetic is a callback function to construct a synthetic
   127  	// function body. It's used for creating the bodies of function
   128  	// literals used to curry arguments to shaped functions.
   129  	synthetic func(pos src.XPos, r *reader)
   130  
   131  	// scopeVars is a stack tracking the number of variables declared in
   132  	// the current function at the moment each open scope was opened.
   133  	scopeVars         []int
   134  	marker            dwarfgen.ScopeMarker
   135  	lastCloseScopePos src.XPos
   136  
   137  	// === details for handling inline body expansion ===
   138  
   139  	// If we're reading in a function body because of inlining, this is
   140  	// the call that we're inlining for.
   141  	inlCaller    *ir.Func
   142  	inlCall      *ir.CallExpr
   143  	inlFunc      *ir.Func
   144  	inlTreeIndex int
   145  	inlPosBases  map[*src.PosBase]*src.PosBase
   146  
   147  	// suppressInlPos tracks whether position base rewriting for
   148  	// inlining should be suppressed. See funcLit.
   149  	suppressInlPos int
   150  
   151  	delayResults bool
   152  
   153  	// Label to return to.
   154  	retlabel *types.Sym
   155  }
   156  
   157  // A readerDict represents an instantiated "compile-time dictionary,"
   158  // used for resolving any derived types needed for instantiating a
   159  // generic object.
   160  //
   161  // A compile-time dictionary can either be "shaped" or "non-shaped."
   162  // Shaped compile-time dictionaries are only used for instantiating
   163  // shaped type definitions and function bodies, while non-shaped
   164  // compile-time dictionaries are used for instantiating runtime
   165  // dictionaries.
   166  type readerDict struct {
   167  	shaped bool // whether this is a shaped dictionary
   168  
   169  	// baseSym is the symbol for the object this dictionary belongs to.
   170  	// If the object is an instantiated function or defined type, then
   171  	// baseSym is the mangled symbol, including any type arguments.
   172  	baseSym *types.Sym
   173  
   174  	// For non-shaped dictionaries, shapedObj is a reference to the
   175  	// corresponding shaped object (always a function or defined type).
   176  	shapedObj *ir.Name
   177  
   178  	// targs holds the implicit and explicit type arguments in use for
   179  	// reading the current object. For example:
   180  	//
   181  	//	func F[T any]() {
   182  	//		type X[U any] struct { t T; u U }
   183  	//		var _ X[string]
   184  	//	}
   185  	//
   186  	//	var _ = F[int]
   187  	//
   188  	// While instantiating F[int], we need to in turn instantiate
   189  	// X[string]. [int] and [string] are explicit type arguments for F
   190  	// and X, respectively; but [int] is also the implicit type
   191  	// arguments for X.
   192  	//
   193  	// (As an analogy to function literals, explicits are the function
   194  	// literal's formal parameters, while implicits are variables
   195  	// captured by the function literal.)
   196  	targs []*types.Type
   197  
   198  	// implicits counts how many of types within targs are implicit type
   199  	// arguments; the rest are explicit.
   200  	implicits int
   201  
   202  	derived      []derivedInfo // reloc index of the derived type's descriptor
   203  	derivedTypes []*types.Type // slice of previously computed derived types
   204  
   205  	// These slices correspond to entries in the runtime dictionary.
   206  	typeParamMethodExprs []readerMethodExprInfo
   207  	subdicts             []objInfo
   208  	rtypes               []typeInfo
   209  	itabs                []itabInfo
   210  }
   211  
   212  type readerMethodExprInfo struct {
   213  	typeParamIdx int
   214  	method       *types.Sym
   215  }
   216  
   217  func setType(n ir.Node, typ *types.Type) {
   218  	n.SetType(typ)
   219  	n.SetTypecheck(1)
   220  }
   221  
   222  func setValue(name *ir.Name, val constant.Value) {
   223  	name.SetVal(val)
   224  	name.Defn = nil
   225  }
   226  
   227  // @@@ Positions
   228  
   229  // pos reads a position from the bitstream.
   230  func (r *reader) pos() src.XPos {
   231  	return base.Ctxt.PosTable.XPos(r.pos0())
   232  }
   233  
   234  // origPos reads a position from the bitstream, and returns both the
   235  // original raw position and an inlining-adjusted position.
   236  func (r *reader) origPos() (origPos, inlPos src.XPos) {
   237  	r.suppressInlPos++
   238  	origPos = r.pos()
   239  	r.suppressInlPos--
   240  	inlPos = r.inlPos(origPos)
   241  	return
   242  }
   243  
   244  func (r *reader) pos0() src.Pos {
   245  	r.Sync(pkgbits.SyncPos)
   246  	if !r.Bool() {
   247  		return src.NoPos
   248  	}
   249  
   250  	posBase := r.posBase()
   251  	line := r.Uint()
   252  	col := r.Uint()
   253  	return src.MakePos(posBase, line, col)
   254  }
   255  
   256  // posBase reads a position base from the bitstream.
   257  func (r *reader) posBase() *src.PosBase {
   258  	return r.inlPosBase(r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase)))
   259  }
   260  
   261  // posBaseIdx returns the specified position base, reading it first if
   262  // needed.
   263  func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) *src.PosBase {
   264  	if b := pr.posBases[idx]; b != nil {
   265  		return b
   266  	}
   267  
   268  	r := pr.newReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
   269  	var b *src.PosBase
   270  
   271  	absFilename := r.String()
   272  	filename := absFilename
   273  
   274  	// For build artifact stability, the export data format only
   275  	// contains the "absolute" filename as returned by objabi.AbsFile.
   276  	// However, some tests (e.g., test/run.go's asmcheck tests) expect
   277  	// to see the full, original filename printed out. Re-expanding
   278  	// "$GOROOT" to buildcfg.GOROOT is a close-enough approximation to
   279  	// satisfy this.
   280  	//
   281  	// The export data format only ever uses slash paths
   282  	// (for cross-operating-system reproducible builds),
   283  	// but error messages need to use native paths (backslash on Windows)
   284  	// as if they had been specified on the command line.
   285  	// (The go command always passes native paths to the compiler.)
   286  	const dollarGOROOT = "$GOROOT"
   287  	if buildcfg.GOROOT != "" && strings.HasPrefix(filename, dollarGOROOT) {
   288  		filename = filepath.FromSlash(buildcfg.GOROOT + filename[len(dollarGOROOT):])
   289  	}
   290  
   291  	if r.Bool() {
   292  		b = src.NewFileBase(filename, absFilename)
   293  	} else {
   294  		pos := r.pos0()
   295  		line := r.Uint()
   296  		col := r.Uint()
   297  		b = src.NewLinePragmaBase(pos, filename, absFilename, line, col)
   298  	}
   299  
   300  	pr.posBases[idx] = b
   301  	return b
   302  }
   303  
   304  // inlPosBase returns the inlining-adjusted src.PosBase corresponding
   305  // to oldBase, which must be a non-inlined position. When not
   306  // inlining, this is just oldBase.
   307  func (r *reader) inlPosBase(oldBase *src.PosBase) *src.PosBase {
   308  	if index := oldBase.InliningIndex(); index >= 0 {
   309  		base.Fatalf("oldBase %v already has inlining index %v", oldBase, index)
   310  	}
   311  
   312  	if r.inlCall == nil || r.suppressInlPos != 0 {
   313  		return oldBase
   314  	}
   315  
   316  	if newBase, ok := r.inlPosBases[oldBase]; ok {
   317  		return newBase
   318  	}
   319  
   320  	newBase := src.NewInliningBase(oldBase, r.inlTreeIndex)
   321  	r.inlPosBases[oldBase] = newBase
   322  	return newBase
   323  }
   324  
   325  // inlPos returns the inlining-adjusted src.XPos corresponding to
   326  // xpos, which must be a non-inlined position. When not inlining, this
   327  // is just xpos.
   328  func (r *reader) inlPos(xpos src.XPos) src.XPos {
   329  	pos := base.Ctxt.PosTable.Pos(xpos)
   330  	pos.SetBase(r.inlPosBase(pos.Base()))
   331  	return base.Ctxt.PosTable.XPos(pos)
   332  }
   333  
   334  // @@@ Packages
   335  
   336  // pkg reads a package reference from the bitstream.
   337  func (r *reader) pkg() *types.Pkg {
   338  	r.Sync(pkgbits.SyncPkg)
   339  	return r.p.pkgIdx(r.Reloc(pkgbits.RelocPkg))
   340  }
   341  
   342  // pkgIdx returns the specified package from the export data, reading
   343  // it first if needed.
   344  func (pr *pkgReader) pkgIdx(idx pkgbits.Index) *types.Pkg {
   345  	if pkg := pr.pkgs[idx]; pkg != nil {
   346  		return pkg
   347  	}
   348  
   349  	pkg := pr.newReader(pkgbits.RelocPkg, idx, pkgbits.SyncPkgDef).doPkg()
   350  	pr.pkgs[idx] = pkg
   351  	return pkg
   352  }
   353  
   354  // doPkg reads a package definition from the bitstream.
   355  func (r *reader) doPkg() *types.Pkg {
   356  	path := r.String()
   357  	switch path {
   358  	case "":
   359  		path = r.p.PkgPath()
   360  	case "builtin":
   361  		return types.BuiltinPkg
   362  	case "unsafe":
   363  		return types.UnsafePkg
   364  	}
   365  
   366  	name := r.String()
   367  
   368  	pkg := types.NewPkg(path, "")
   369  
   370  	if pkg.Name == "" {
   371  		pkg.Name = name
   372  	} else {
   373  		base.Assertf(pkg.Name == name, "package %q has name %q, but want %q", pkg.Path, pkg.Name, name)
   374  	}
   375  
   376  	return pkg
   377  }
   378  
   379  // @@@ Types
   380  
   381  func (r *reader) typ() *types.Type {
   382  	return r.typWrapped(true)
   383  }
   384  
   385  // typWrapped is like typ, but allows suppressing generation of
   386  // unnecessary wrappers as a compile-time optimization.
   387  func (r *reader) typWrapped(wrapped bool) *types.Type {
   388  	return r.p.typIdx(r.typInfo(), r.dict, wrapped)
   389  }
   390  
   391  func (r *reader) typInfo() typeInfo {
   392  	r.Sync(pkgbits.SyncType)
   393  	if r.Bool() {
   394  		return typeInfo{idx: pkgbits.Index(r.Len()), derived: true}
   395  	}
   396  	return typeInfo{idx: r.Reloc(pkgbits.RelocType), derived: false}
   397  }
   398  
   399  // typListIdx returns a list of the specified types, resolving derived
   400  // types within the given dictionary.
   401  func (pr *pkgReader) typListIdx(infos []typeInfo, dict *readerDict) []*types.Type {
   402  	typs := make([]*types.Type, len(infos))
   403  	for i, info := range infos {
   404  		typs[i] = pr.typIdx(info, dict, true)
   405  	}
   406  	return typs
   407  }
   408  
   409  // typIdx returns the specified type. If info specifies a derived
   410  // type, it's resolved within the given dictionary. If wrapped is
   411  // true, then method wrappers will be generated, if appropriate.
   412  func (pr *pkgReader) typIdx(info typeInfo, dict *readerDict, wrapped bool) *types.Type {
   413  	idx := info.idx
   414  	var where **types.Type
   415  	if info.derived {
   416  		where = &dict.derivedTypes[idx]
   417  		idx = dict.derived[idx].idx
   418  	} else {
   419  		where = &pr.typs[idx]
   420  	}
   421  
   422  	if typ := *where; typ != nil {
   423  		return typ
   424  	}
   425  
   426  	r := pr.newReader(pkgbits.RelocType, idx, pkgbits.SyncTypeIdx)
   427  	r.dict = dict
   428  
   429  	typ := r.doTyp()
   430  	if typ == nil {
   431  		base.Fatalf("doTyp returned nil for info=%v", info)
   432  	}
   433  
   434  	// For recursive type declarations involving interfaces and aliases,
   435  	// above r.doTyp() call may have already set pr.typs[idx], so just
   436  	// double check and return the type.
   437  	//
   438  	// Example:
   439  	//
   440  	//     type F = func(I)
   441  	//
   442  	//     type I interface {
   443  	//         m(F)
   444  	//     }
   445  	//
   446  	// The writer writes data types in following index order:
   447  	//
   448  	//     0: func(I)
   449  	//     1: I
   450  	//     2: interface{m(func(I))}
   451  	//
   452  	// The reader resolves it in following index order:
   453  	//
   454  	//     0 -> 1 -> 2 -> 0 -> 1
   455  	//
   456  	// and can divide in logically 2 steps:
   457  	//
   458  	//  - 0 -> 1     : first time the reader reach type I,
   459  	//                 it creates new named type with symbol I.
   460  	//
   461  	//  - 2 -> 0 -> 1: the reader ends up reaching symbol I again,
   462  	//                 now the symbol I was setup in above step, so
   463  	//                 the reader just return the named type.
   464  	//
   465  	// Now, the functions called return, the pr.typs looks like below:
   466  	//
   467  	//  - 0 -> 1 -> 2 -> 0 : [<T> I <T>]
   468  	//  - 0 -> 1 -> 2      : [func(I) I <T>]
   469  	//  - 0 -> 1           : [func(I) I interface { "".m(func("".I)) }]
   470  	//
   471  	// The idx 1, corresponding with type I was resolved successfully
   472  	// after r.doTyp() call.
   473  
   474  	if prev := *where; prev != nil {
   475  		return prev
   476  	}
   477  
   478  	if wrapped {
   479  		// Only cache if we're adding wrappers, so that other callers that
   480  		// find a cached type know it was wrapped.
   481  		*where = typ
   482  
   483  		r.needWrapper(typ)
   484  	}
   485  
   486  	if !typ.IsUntyped() {
   487  		types.CheckSize(typ)
   488  	}
   489  
   490  	return typ
   491  }
   492  
   493  func (r *reader) doTyp() *types.Type {
   494  	switch tag := pkgbits.CodeType(r.Code(pkgbits.SyncType)); tag {
   495  	default:
   496  		panic(fmt.Sprintf("unexpected type: %v", tag))
   497  
   498  	case pkgbits.TypeBasic:
   499  		return *basics[r.Len()]
   500  
   501  	case pkgbits.TypeNamed:
   502  		obj := r.obj()
   503  		assert(obj.Op() == ir.OTYPE)
   504  		return obj.Type()
   505  
   506  	case pkgbits.TypeTypeParam:
   507  		return r.dict.targs[r.Len()]
   508  
   509  	case pkgbits.TypeArray:
   510  		len := int64(r.Uint64())
   511  		return types.NewArray(r.typ(), len)
   512  	case pkgbits.TypeChan:
   513  		dir := dirs[r.Len()]
   514  		return types.NewChan(r.typ(), dir)
   515  	case pkgbits.TypeMap:
   516  		return types.NewMap(r.typ(), r.typ())
   517  	case pkgbits.TypePointer:
   518  		return types.NewPtr(r.typ())
   519  	case pkgbits.TypeSignature:
   520  		return r.signature(nil)
   521  	case pkgbits.TypeSlice:
   522  		return types.NewSlice(r.typ())
   523  	case pkgbits.TypeStruct:
   524  		return r.structType()
   525  	case pkgbits.TypeInterface:
   526  		return r.interfaceType()
   527  	case pkgbits.TypeUnion:
   528  		return r.unionType()
   529  	}
   530  }
   531  
   532  func (r *reader) unionType() *types.Type {
   533  	// In the types1 universe, we only need to handle value types.
   534  	// Impure interfaces (i.e., interfaces with non-trivial type sets
   535  	// like "int | string") can only appear as type parameter bounds,
   536  	// and this is enforced by the types2 type checker.
   537  	//
   538  	// However, type unions can still appear in pure interfaces if the
   539  	// type union is equivalent to "any". E.g., typeparam/issue52124.go
   540  	// declares variables with the type "interface { any | int }".
   541  	//
   542  	// To avoid needing to represent type unions in types1 (since we
   543  	// don't have any uses for that today anyway), we simply fold them
   544  	// to "any".
   545  
   546  	// TODO(mdempsky): Restore consistency check to make sure folding to
   547  	// "any" is safe. This is unfortunately tricky, because a pure
   548  	// interface can reference impure interfaces too, including
   549  	// cyclically (#60117).
   550  	if false {
   551  		pure := false
   552  		for i, n := 0, r.Len(); i < n; i++ {
   553  			_ = r.Bool() // tilde
   554  			term := r.typ()
   555  			if term.IsEmptyInterface() {
   556  				pure = true
   557  			}
   558  		}
   559  		if !pure {
   560  			base.Fatalf("impure type set used in value type")
   561  		}
   562  	}
   563  
   564  	return types.Types[types.TINTER]
   565  }
   566  
   567  func (r *reader) interfaceType() *types.Type {
   568  	nmethods, nembeddeds := r.Len(), r.Len()
   569  	implicit := nmethods == 0 && nembeddeds == 1 && r.Bool()
   570  	assert(!implicit) // implicit interfaces only appear in constraints
   571  
   572  	fields := make([]*types.Field, nmethods+nembeddeds)
   573  	methods, embeddeds := fields[:nmethods], fields[nmethods:]
   574  
   575  	for i := range methods {
   576  		methods[i] = types.NewField(r.pos(), r.selector(), r.signature(types.FakeRecv()))
   577  	}
   578  	for i := range embeddeds {
   579  		embeddeds[i] = types.NewField(src.NoXPos, nil, r.typ())
   580  	}
   581  
   582  	if len(fields) == 0 {
   583  		return types.Types[types.TINTER] // empty interface
   584  	}
   585  	return types.NewInterface(fields)
   586  }
   587  
   588  func (r *reader) structType() *types.Type {
   589  	fields := make([]*types.Field, r.Len())
   590  	for i := range fields {
   591  		field := types.NewField(r.pos(), r.selector(), r.typ())
   592  		field.Note = r.String()
   593  		if r.Bool() {
   594  			field.Embedded = 1
   595  		}
   596  		fields[i] = field
   597  	}
   598  	return types.NewStruct(fields)
   599  }
   600  
   601  func (r *reader) signature(recv *types.Field) *types.Type {
   602  	r.Sync(pkgbits.SyncSignature)
   603  
   604  	params := r.params()
   605  	results := r.params()
   606  	if r.Bool() { // variadic
   607  		params[len(params)-1].SetIsDDD(true)
   608  	}
   609  
   610  	return types.NewSignature(recv, params, results)
   611  }
   612  
   613  func (r *reader) params() []*types.Field {
   614  	r.Sync(pkgbits.SyncParams)
   615  	params := make([]*types.Field, r.Len())
   616  	for i := range params {
   617  		params[i] = r.param()
   618  	}
   619  	return params
   620  }
   621  
   622  func (r *reader) param() *types.Field {
   623  	r.Sync(pkgbits.SyncParam)
   624  	return types.NewField(r.pos(), r.localIdent(), r.typ())
   625  }
   626  
   627  // @@@ Objects
   628  
   629  // objReader maps qualified identifiers (represented as *types.Sym) to
   630  // a pkgReader and corresponding index that can be used for reading
   631  // that object's definition.
   632  var objReader = map[*types.Sym]pkgReaderIndex{}
   633  
   634  // obj reads an instantiated object reference from the bitstream.
   635  func (r *reader) obj() ir.Node {
   636  	return r.p.objInstIdx(r.objInfo(), r.dict, false)
   637  }
   638  
   639  // objInfo reads an instantiated object reference from the bitstream
   640  // and returns the encoded reference to it, without instantiating it.
   641  func (r *reader) objInfo() objInfo {
   642  	r.Sync(pkgbits.SyncObject)
   643  	assert(!r.Bool()) // TODO(mdempsky): Remove; was derived func inst.
   644  	idx := r.Reloc(pkgbits.RelocObj)
   645  
   646  	explicits := make([]typeInfo, r.Len())
   647  	for i := range explicits {
   648  		explicits[i] = r.typInfo()
   649  	}
   650  
   651  	return objInfo{idx, explicits}
   652  }
   653  
   654  // objInstIdx returns the encoded, instantiated object. If shaped is
   655  // true, then the shaped variant of the object is returned instead.
   656  func (pr *pkgReader) objInstIdx(info objInfo, dict *readerDict, shaped bool) ir.Node {
   657  	explicits := pr.typListIdx(info.explicits, dict)
   658  
   659  	var implicits []*types.Type
   660  	if dict != nil {
   661  		implicits = dict.targs
   662  	}
   663  
   664  	return pr.objIdx(info.idx, implicits, explicits, shaped)
   665  }
   666  
   667  // objIdx returns the specified object, instantiated with the given
   668  // type arguments, if any.
   669  // If shaped is true, then the shaped variant of the object is returned
   670  // instead.
   671  func (pr *pkgReader) objIdx(idx pkgbits.Index, implicits, explicits []*types.Type, shaped bool) ir.Node {
   672  	n, err := pr.objIdxMayFail(idx, implicits, explicits, shaped)
   673  	if err != nil {
   674  		base.Fatalf("%v", err)
   675  	}
   676  	return n
   677  }
   678  
   679  // objIdxMayFail is equivalent to objIdx, but returns an error rather than
   680  // failing the build if this object requires type arguments and the incorrect
   681  // number of type arguments were passed.
   682  //
   683  // Other sources of internal failure (such as duplicate definitions) still fail
   684  // the build.
   685  func (pr *pkgReader) objIdxMayFail(idx pkgbits.Index, implicits, explicits []*types.Type, shaped bool) (ir.Node, error) {
   686  	rname := pr.newReader(pkgbits.RelocName, idx, pkgbits.SyncObject1)
   687  	_, sym := rname.qualifiedIdent()
   688  	tag := pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
   689  
   690  	if tag == pkgbits.ObjStub {
   691  		assert(!sym.IsBlank())
   692  		switch sym.Pkg {
   693  		case types.BuiltinPkg, types.UnsafePkg:
   694  			return sym.Def.(ir.Node), nil
   695  		}
   696  		if pri, ok := objReader[sym]; ok {
   697  			return pri.pr.objIdxMayFail(pri.idx, nil, explicits, shaped)
   698  		}
   699  		if sym.Pkg.Path == "runtime" {
   700  			return typecheck.LookupRuntime(sym.Name), nil
   701  		}
   702  		base.Fatalf("unresolved stub: %v", sym)
   703  	}
   704  
   705  	dict, err := pr.objDictIdx(sym, idx, implicits, explicits, shaped)
   706  	if err != nil {
   707  		return nil, err
   708  	}
   709  
   710  	sym = dict.baseSym
   711  	if !sym.IsBlank() && sym.Def != nil {
   712  		return sym.Def.(*ir.Name), nil
   713  	}
   714  
   715  	r := pr.newReader(pkgbits.RelocObj, idx, pkgbits.SyncObject1)
   716  	rext := pr.newReader(pkgbits.RelocObjExt, idx, pkgbits.SyncObject1)
   717  
   718  	r.dict = dict
   719  	rext.dict = dict
   720  
   721  	do := func(op ir.Op, hasTParams bool) *ir.Name {
   722  		pos := r.pos()
   723  		setBasePos(pos)
   724  		if hasTParams {
   725  			r.typeParamNames()
   726  		}
   727  
   728  		name := ir.NewDeclNameAt(pos, op, sym)
   729  		name.Class = ir.PEXTERN // may be overridden later
   730  		if !sym.IsBlank() {
   731  			if sym.Def != nil {
   732  				base.FatalfAt(name.Pos(), "already have a definition for %v", name)
   733  			}
   734  			assert(sym.Def == nil)
   735  			sym.Def = name
   736  		}
   737  		return name
   738  	}
   739  
   740  	switch tag {
   741  	default:
   742  		panic("unexpected object")
   743  
   744  	case pkgbits.ObjAlias:
   745  		name := do(ir.OTYPE, false)
   746  
   747  		// Clumsy dance: the r.typ() call here might recursively find this
   748  		// type alias name, before we've set its type (#66873). So we
   749  		// temporarily clear sym.Def and then restore it later, if still
   750  		// unset.
   751  		hack := sym.Def == name
   752  		if hack {
   753  			sym.Def = nil
   754  		}
   755  		typ := r.typ()
   756  		if hack {
   757  			if sym.Def != nil {
   758  				name = sym.Def.(*ir.Name)
   759  				assert(name.Type() == typ)
   760  				return name, nil
   761  			}
   762  			sym.Def = name
   763  		}
   764  
   765  		setType(name, typ)
   766  		name.SetAlias(true)
   767  		return name, nil
   768  
   769  	case pkgbits.ObjConst:
   770  		name := do(ir.OLITERAL, false)
   771  		typ := r.typ()
   772  		val := FixValue(typ, r.Value())
   773  		setType(name, typ)
   774  		setValue(name, val)
   775  		return name, nil
   776  
   777  	case pkgbits.ObjFunc:
   778  		if sym.Name == "init" {
   779  			sym = Renameinit()
   780  		}
   781  
   782  		npos := r.pos()
   783  		setBasePos(npos)
   784  		r.typeParamNames()
   785  		typ := r.signature(nil)
   786  		fpos := r.pos()
   787  
   788  		fn := ir.NewFunc(fpos, npos, sym, typ)
   789  		name := fn.Nname
   790  		if !sym.IsBlank() {
   791  			if sym.Def != nil {
   792  				base.FatalfAt(name.Pos(), "already have a definition for %v", name)
   793  			}
   794  			assert(sym.Def == nil)
   795  			sym.Def = name
   796  		}
   797  
   798  		if r.hasTypeParams() {
   799  			name.Func.SetDupok(true)
   800  			if r.dict.shaped {
   801  				setType(name, shapeSig(name.Func, r.dict))
   802  			} else {
   803  				todoDicts = append(todoDicts, func() {
   804  					r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
   805  				})
   806  			}
   807  		}
   808  
   809  		rext.funcExt(name, nil)
   810  		return name, nil
   811  
   812  	case pkgbits.ObjType:
   813  		name := do(ir.OTYPE, true)
   814  		typ := types.NewNamed(name)
   815  		setType(name, typ)
   816  		if r.hasTypeParams() && r.dict.shaped {
   817  			typ.SetHasShape(true)
   818  		}
   819  
   820  		// Important: We need to do this before SetUnderlying.
   821  		rext.typeExt(name)
   822  
   823  		// We need to defer CheckSize until we've called SetUnderlying to
   824  		// handle recursive types.
   825  		types.DeferCheckSize()
   826  		typ.SetUnderlying(r.typWrapped(false))
   827  		types.ResumeCheckSize()
   828  
   829  		if r.hasTypeParams() && !r.dict.shaped {
   830  			todoDicts = append(todoDicts, func() {
   831  				r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
   832  			})
   833  		}
   834  
   835  		methods := make([]*types.Field, r.Len())
   836  		for i := range methods {
   837  			methods[i] = r.method(rext)
   838  		}
   839  		if len(methods) != 0 {
   840  			typ.SetMethods(methods)
   841  		}
   842  
   843  		if !r.dict.shaped {
   844  			r.needWrapper(typ)
   845  		}
   846  
   847  		return name, nil
   848  
   849  	case pkgbits.ObjVar:
   850  		name := do(ir.ONAME, false)
   851  		setType(name, r.typ())
   852  		rext.varExt(name)
   853  		return name, nil
   854  	}
   855  }
   856  
   857  func (dict *readerDict) mangle(sym *types.Sym) *types.Sym {
   858  	if !dict.hasTypeParams() {
   859  		return sym
   860  	}
   861  
   862  	// If sym is a locally defined generic type, we need the suffix to
   863  	// stay at the end after mangling so that types/fmt.go can strip it
   864  	// out again when writing the type's runtime descriptor (#54456).
   865  	base, suffix := types.SplitVargenSuffix(sym.Name)
   866  
   867  	var buf strings.Builder
   868  	buf.WriteString(base)
   869  	buf.WriteByte('[')
   870  	for i, targ := range dict.targs {
   871  		if i > 0 {
   872  			if i == dict.implicits {
   873  				buf.WriteByte(';')
   874  			} else {
   875  				buf.WriteByte(',')
   876  			}
   877  		}
   878  		buf.WriteString(targ.LinkString())
   879  	}
   880  	buf.WriteByte(']')
   881  	buf.WriteString(suffix)
   882  	return sym.Pkg.Lookup(buf.String())
   883  }
   884  
   885  // shapify returns the shape type for targ.
   886  //
   887  // If basic is true, then the type argument is used to instantiate a
   888  // type parameter whose constraint is a basic interface.
   889  func shapify(targ *types.Type, basic bool) *types.Type {
   890  	if targ.Kind() == types.TFORW {
   891  		if targ.IsFullyInstantiated() {
   892  			// For recursive instantiated type argument, it may  still be a TFORW
   893  			// when shapifying happens. If we don't have targ's underlying type,
   894  			// shapify won't work. The worst case is we end up not reusing code
   895  			// optimally in some tricky cases.
   896  			if base.Debug.Shapify != 0 {
   897  				base.Warn("skipping shaping of recursive type %v", targ)
   898  			}
   899  			if targ.HasShape() {
   900  				return targ
   901  			}
   902  		} else {
   903  			base.Fatalf("%v is missing its underlying type", targ)
   904  		}
   905  	}
   906  	// For fully instantiated shape interface type, use it as-is. Otherwise, the instantiation
   907  	// involved recursive generic interface may cause mismatching in function signature, see issue #65362.
   908  	if targ.Kind() == types.TINTER && targ.IsFullyInstantiated() && targ.HasShape() {
   909  		return targ
   910  	}
   911  
   912  	// When a pointer type is used to instantiate a type parameter
   913  	// constrained by a basic interface, we know the pointer's element
   914  	// type can't matter to the generated code. In this case, we can use
   915  	// an arbitrary pointer type as the shape type. (To match the
   916  	// non-unified frontend, we use `*byte`.)
   917  	//
   918  	// Otherwise, we simply use the type's underlying type as its shape.
   919  	//
   920  	// TODO(mdempsky): It should be possible to do much more aggressive
   921  	// shaping still; e.g., collapsing all pointer-shaped types into a
   922  	// common type, collapsing scalars of the same size/alignment into a
   923  	// common type, recursively shaping the element types of composite
   924  	// types, and discarding struct field names and tags. However, we'll
   925  	// need to start tracking how type parameters are actually used to
   926  	// implement some of these optimizations.
   927  	under := targ.Underlying()
   928  	if basic && targ.IsPtr() && !targ.Elem().NotInHeap() {
   929  		under = types.NewPtr(types.Types[types.TUINT8])
   930  	}
   931  
   932  	// Hash long type names to bound symbol name length seen by users,
   933  	// particularly for large protobuf structs (#65030).
   934  	uls := under.LinkString()
   935  	if base.Debug.MaxShapeLen != 0 &&
   936  		len(uls) > base.Debug.MaxShapeLen {
   937  		h := notsha256.Sum256([]byte(uls))
   938  		uls = hex.EncodeToString(h[:])
   939  	}
   940  
   941  	sym := types.ShapePkg.Lookup(uls)
   942  	if sym.Def == nil {
   943  		name := ir.NewDeclNameAt(under.Pos(), ir.OTYPE, sym)
   944  		typ := types.NewNamed(name)
   945  		typ.SetUnderlying(under)
   946  		sym.Def = typed(typ, name)
   947  	}
   948  	res := sym.Def.Type()
   949  	assert(res.IsShape())
   950  	assert(res.HasShape())
   951  	return res
   952  }
   953  
   954  // objDictIdx reads and returns the specified object dictionary.
   955  func (pr *pkgReader) objDictIdx(sym *types.Sym, idx pkgbits.Index, implicits, explicits []*types.Type, shaped bool) (*readerDict, error) {
   956  	r := pr.newReader(pkgbits.RelocObjDict, idx, pkgbits.SyncObject1)
   957  
   958  	dict := readerDict{
   959  		shaped: shaped,
   960  	}
   961  
   962  	nimplicits := r.Len()
   963  	nexplicits := r.Len()
   964  
   965  	if nimplicits > len(implicits) || nexplicits != len(explicits) {
   966  		return nil, fmt.Errorf("%v has %v+%v params, but instantiated with %v+%v args", sym, nimplicits, nexplicits, len(implicits), len(explicits))
   967  	}
   968  
   969  	dict.targs = append(implicits[:nimplicits:nimplicits], explicits...)
   970  	dict.implicits = nimplicits
   971  
   972  	// Within the compiler, we can just skip over the type parameters.
   973  	for range dict.targs[dict.implicits:] {
   974  		// Skip past bounds without actually evaluating them.
   975  		r.typInfo()
   976  	}
   977  
   978  	dict.derived = make([]derivedInfo, r.Len())
   979  	dict.derivedTypes = make([]*types.Type, len(dict.derived))
   980  	for i := range dict.derived {
   981  		dict.derived[i] = derivedInfo{r.Reloc(pkgbits.RelocType), r.Bool()}
   982  	}
   983  
   984  	// Runtime dictionary information; private to the compiler.
   985  
   986  	// If any type argument is already shaped, then we're constructing a
   987  	// shaped object, even if not explicitly requested (i.e., calling
   988  	// objIdx with shaped==true). This can happen with instantiating
   989  	// types that are referenced within a function body.
   990  	for _, targ := range dict.targs {
   991  		if targ.HasShape() {
   992  			dict.shaped = true
   993  			break
   994  		}
   995  	}
   996  
   997  	// And if we're constructing a shaped object, then shapify all type
   998  	// arguments.
   999  	for i, targ := range dict.targs {
  1000  		basic := r.Bool()
  1001  		if dict.shaped {
  1002  			dict.targs[i] = shapify(targ, basic)
  1003  		}
  1004  	}
  1005  
  1006  	dict.baseSym = dict.mangle(sym)
  1007  
  1008  	dict.typeParamMethodExprs = make([]readerMethodExprInfo, r.Len())
  1009  	for i := range dict.typeParamMethodExprs {
  1010  		typeParamIdx := r.Len()
  1011  		method := r.selector()
  1012  
  1013  		dict.typeParamMethodExprs[i] = readerMethodExprInfo{typeParamIdx, method}
  1014  	}
  1015  
  1016  	dict.subdicts = make([]objInfo, r.Len())
  1017  	for i := range dict.subdicts {
  1018  		dict.subdicts[i] = r.objInfo()
  1019  	}
  1020  
  1021  	dict.rtypes = make([]typeInfo, r.Len())
  1022  	for i := range dict.rtypes {
  1023  		dict.rtypes[i] = r.typInfo()
  1024  	}
  1025  
  1026  	dict.itabs = make([]itabInfo, r.Len())
  1027  	for i := range dict.itabs {
  1028  		dict.itabs[i] = itabInfo{typ: r.typInfo(), iface: r.typInfo()}
  1029  	}
  1030  
  1031  	return &dict, nil
  1032  }
  1033  
  1034  func (r *reader) typeParamNames() {
  1035  	r.Sync(pkgbits.SyncTypeParamNames)
  1036  
  1037  	for range r.dict.targs[r.dict.implicits:] {
  1038  		r.pos()
  1039  		r.localIdent()
  1040  	}
  1041  }
  1042  
  1043  func (r *reader) method(rext *reader) *types.Field {
  1044  	r.Sync(pkgbits.SyncMethod)
  1045  	npos := r.pos()
  1046  	sym := r.selector()
  1047  	r.typeParamNames()
  1048  	recv := r.param()
  1049  	typ := r.signature(recv)
  1050  
  1051  	fpos := r.pos()
  1052  	fn := ir.NewFunc(fpos, npos, ir.MethodSym(recv.Type, sym), typ)
  1053  	name := fn.Nname
  1054  
  1055  	if r.hasTypeParams() {
  1056  		name.Func.SetDupok(true)
  1057  		if r.dict.shaped {
  1058  			typ = shapeSig(name.Func, r.dict)
  1059  			setType(name, typ)
  1060  		}
  1061  	}
  1062  
  1063  	rext.funcExt(name, sym)
  1064  
  1065  	meth := types.NewField(name.Func.Pos(), sym, typ)
  1066  	meth.Nname = name
  1067  	meth.SetNointerface(name.Func.Pragma&ir.Nointerface != 0)
  1068  
  1069  	return meth
  1070  }
  1071  
  1072  func (r *reader) qualifiedIdent() (pkg *types.Pkg, sym *types.Sym) {
  1073  	r.Sync(pkgbits.SyncSym)
  1074  	pkg = r.pkg()
  1075  	if name := r.String(); name != "" {
  1076  		sym = pkg.Lookup(name)
  1077  	}
  1078  	return
  1079  }
  1080  
  1081  func (r *reader) localIdent() *types.Sym {
  1082  	r.Sync(pkgbits.SyncLocalIdent)
  1083  	pkg := r.pkg()
  1084  	if name := r.String(); name != "" {
  1085  		return pkg.Lookup(name)
  1086  	}
  1087  	return nil
  1088  }
  1089  
  1090  func (r *reader) selector() *types.Sym {
  1091  	r.Sync(pkgbits.SyncSelector)
  1092  	pkg := r.pkg()
  1093  	name := r.String()
  1094  	if types.IsExported(name) {
  1095  		pkg = types.LocalPkg
  1096  	}
  1097  	return pkg.Lookup(name)
  1098  }
  1099  
  1100  func (r *reader) hasTypeParams() bool {
  1101  	return r.dict.hasTypeParams()
  1102  }
  1103  
  1104  func (dict *readerDict) hasTypeParams() bool {
  1105  	return dict != nil && len(dict.targs) != 0
  1106  }
  1107  
  1108  // @@@ Compiler extensions
  1109  
  1110  func (r *reader) funcExt(name *ir.Name, method *types.Sym) {
  1111  	r.Sync(pkgbits.SyncFuncExt)
  1112  
  1113  	fn := name.Func
  1114  
  1115  	// XXX: Workaround because linker doesn't know how to copy Pos.
  1116  	if !fn.Pos().IsKnown() {
  1117  		fn.SetPos(name.Pos())
  1118  	}
  1119  
  1120  	// Normally, we only compile local functions, which saves redundant compilation work.
  1121  	// n.Defn is not nil for local functions, and is nil for imported function. But for
  1122  	// generic functions, we might have an instantiation that no other package has seen before.
  1123  	// So we need to be conservative and compile it again.
  1124  	//
  1125  	// That's why name.Defn is set here, so ir.VisitFuncsBottomUp can analyze function.
  1126  	// TODO(mdempsky,cuonglm): find a cleaner way to handle this.
  1127  	if name.Sym().Pkg == types.LocalPkg || r.hasTypeParams() {
  1128  		name.Defn = fn
  1129  	}
  1130  
  1131  	fn.Pragma = r.pragmaFlag()
  1132  	r.linkname(name)
  1133  
  1134  	if buildcfg.GOARCH == "wasm" {
  1135  		xmod := r.String()
  1136  		xname := r.String()
  1137  
  1138  		if xmod != "" && xname != "" {
  1139  			fn.WasmImport = &ir.WasmImport{
  1140  				Module: xmod,
  1141  				Name:   xname,
  1142  			}
  1143  		}
  1144  	}
  1145  
  1146  	if r.Bool() {
  1147  		assert(name.Defn == nil)
  1148  
  1149  		fn.ABI = obj.ABI(r.Uint64())
  1150  
  1151  		// Escape analysis.
  1152  		for _, f := range name.Type().RecvParams() {
  1153  			f.Note = r.String()
  1154  		}
  1155  
  1156  		if r.Bool() {
  1157  			fn.Inl = &ir.Inline{
  1158  				Cost:            int32(r.Len()),
  1159  				CanDelayResults: r.Bool(),
  1160  			}
  1161  			if buildcfg.Experiment.NewInliner {
  1162  				fn.Inl.Properties = r.String()
  1163  			}
  1164  		}
  1165  	} else {
  1166  		r.addBody(name.Func, method)
  1167  	}
  1168  	r.Sync(pkgbits.SyncEOF)
  1169  }
  1170  
  1171  func (r *reader) typeExt(name *ir.Name) {
  1172  	r.Sync(pkgbits.SyncTypeExt)
  1173  
  1174  	typ := name.Type()
  1175  
  1176  	if r.hasTypeParams() {
  1177  		// Set "RParams" (really type arguments here, not parameters) so
  1178  		// this type is treated as "fully instantiated". This ensures the
  1179  		// type descriptor is written out as DUPOK and method wrappers are
  1180  		// generated even for imported types.
  1181  		var targs []*types.Type
  1182  		targs = append(targs, r.dict.targs...)
  1183  		typ.SetRParams(targs)
  1184  	}
  1185  
  1186  	name.SetPragma(r.pragmaFlag())
  1187  
  1188  	typecheck.SetBaseTypeIndex(typ, r.Int64(), r.Int64())
  1189  }
  1190  
  1191  func (r *reader) varExt(name *ir.Name) {
  1192  	r.Sync(pkgbits.SyncVarExt)
  1193  	r.linkname(name)
  1194  }
  1195  
  1196  func (r *reader) linkname(name *ir.Name) {
  1197  	assert(name.Op() == ir.ONAME)
  1198  	r.Sync(pkgbits.SyncLinkname)
  1199  
  1200  	if idx := r.Int64(); idx >= 0 {
  1201  		lsym := name.Linksym()
  1202  		lsym.SymIdx = int32(idx)
  1203  		lsym.Set(obj.AttrIndexed, true)
  1204  	} else {
  1205  		linkname := r.String()
  1206  		sym := name.Sym()
  1207  		sym.Linkname = linkname
  1208  		if sym.Pkg == types.LocalPkg && linkname != "" {
  1209  			// Mark linkname in the current package. We don't mark the
  1210  			// ones that are imported and propagated (e.g. through
  1211  			// inlining or instantiation, which are marked in their
  1212  			// corresponding packages). So we can tell in which package
  1213  			// the linkname is used (pulled), and the linker can
  1214  			// make a decision for allowing or disallowing it.
  1215  			sym.Linksym().Set(obj.AttrLinkname, true)
  1216  		}
  1217  	}
  1218  }
  1219  
  1220  func (r *reader) pragmaFlag() ir.PragmaFlag {
  1221  	r.Sync(pkgbits.SyncPragma)
  1222  	return ir.PragmaFlag(r.Int())
  1223  }
  1224  
  1225  // @@@ Function bodies
  1226  
  1227  // bodyReader tracks where the serialized IR for a local or imported,
  1228  // generic function's body can be found.
  1229  var bodyReader = map[*ir.Func]pkgReaderIndex{}
  1230  
  1231  // importBodyReader tracks where the serialized IR for an imported,
  1232  // static (i.e., non-generic) function body can be read.
  1233  var importBodyReader = map[*types.Sym]pkgReaderIndex{}
  1234  
  1235  // bodyReaderFor returns the pkgReaderIndex for reading fn's
  1236  // serialized IR, and whether one was found.
  1237  func bodyReaderFor(fn *ir.Func) (pri pkgReaderIndex, ok bool) {
  1238  	if fn.Nname.Defn != nil {
  1239  		pri, ok = bodyReader[fn]
  1240  		base.AssertfAt(ok, base.Pos, "must have bodyReader for %v", fn) // must always be available
  1241  	} else {
  1242  		pri, ok = importBodyReader[fn.Sym()]
  1243  	}
  1244  	return
  1245  }
  1246  
  1247  // todoDicts holds the list of dictionaries that still need their
  1248  // runtime dictionary objects constructed.
  1249  var todoDicts []func()
  1250  
  1251  // todoBodies holds the list of function bodies that still need to be
  1252  // constructed.
  1253  var todoBodies []*ir.Func
  1254  
  1255  // addBody reads a function body reference from the element bitstream,
  1256  // and associates it with fn.
  1257  func (r *reader) addBody(fn *ir.Func, method *types.Sym) {
  1258  	// addBody should only be called for local functions or imported
  1259  	// generic functions; see comment in funcExt.
  1260  	assert(fn.Nname.Defn != nil)
  1261  
  1262  	idx := r.Reloc(pkgbits.RelocBody)
  1263  
  1264  	pri := pkgReaderIndex{r.p, idx, r.dict, method, nil}
  1265  	bodyReader[fn] = pri
  1266  
  1267  	if r.curfn == nil {
  1268  		todoBodies = append(todoBodies, fn)
  1269  		return
  1270  	}
  1271  
  1272  	pri.funcBody(fn)
  1273  }
  1274  
  1275  func (pri pkgReaderIndex) funcBody(fn *ir.Func) {
  1276  	r := pri.asReader(pkgbits.RelocBody, pkgbits.SyncFuncBody)
  1277  	r.funcBody(fn)
  1278  }
  1279  
  1280  // funcBody reads a function body definition from the element
  1281  // bitstream, and populates fn with it.
  1282  func (r *reader) funcBody(fn *ir.Func) {
  1283  	r.curfn = fn
  1284  	r.closureVars = fn.ClosureVars
  1285  	if len(r.closureVars) != 0 && r.hasTypeParams() {
  1286  		r.dictParam = r.closureVars[len(r.closureVars)-1] // dictParam is last; see reader.funcLit
  1287  	}
  1288  
  1289  	ir.WithFunc(fn, func() {
  1290  		r.declareParams()
  1291  
  1292  		if r.syntheticBody(fn.Pos()) {
  1293  			return
  1294  		}
  1295  
  1296  		if !r.Bool() {
  1297  			return
  1298  		}
  1299  
  1300  		body := r.stmts()
  1301  		if body == nil {
  1302  			body = []ir.Node{typecheck.Stmt(ir.NewBlockStmt(src.NoXPos, nil))}
  1303  		}
  1304  		fn.Body = body
  1305  		fn.Endlineno = r.pos()
  1306  	})
  1307  
  1308  	r.marker.WriteTo(fn)
  1309  }
  1310  
  1311  // syntheticBody adds a synthetic body to r.curfn if appropriate, and
  1312  // reports whether it did.
  1313  func (r *reader) syntheticBody(pos src.XPos) bool {
  1314  	if r.synthetic != nil {
  1315  		r.synthetic(pos, r)
  1316  		return true
  1317  	}
  1318  
  1319  	// If this function has type parameters and isn't shaped, then we
  1320  	// just tail call its corresponding shaped variant.
  1321  	if r.hasTypeParams() && !r.dict.shaped {
  1322  		r.callShaped(pos)
  1323  		return true
  1324  	}
  1325  
  1326  	return false
  1327  }
  1328  
  1329  // callShaped emits a tail call to r.shapedFn, passing along the
  1330  // arguments to the current function.
  1331  func (r *reader) callShaped(pos src.XPos) {
  1332  	shapedObj := r.dict.shapedObj
  1333  	assert(shapedObj != nil)
  1334  
  1335  	var shapedFn ir.Node
  1336  	if r.methodSym == nil {
  1337  		// Instantiating a generic function; shapedObj is the shaped
  1338  		// function itself.
  1339  		assert(shapedObj.Op() == ir.ONAME && shapedObj.Class == ir.PFUNC)
  1340  		shapedFn = shapedObj
  1341  	} else {
  1342  		// Instantiating a generic type's method; shapedObj is the shaped
  1343  		// type, so we need to select it's corresponding method.
  1344  		shapedFn = shapedMethodExpr(pos, shapedObj, r.methodSym)
  1345  	}
  1346  
  1347  	params := r.syntheticArgs()
  1348  
  1349  	// Construct the arguments list: receiver (if any), then runtime
  1350  	// dictionary, and finally normal parameters.
  1351  	//
  1352  	// Note: For simplicity, shaped methods are added as normal methods
  1353  	// on their shaped types. So existing code (e.g., packages ir and
  1354  	// typecheck) expects the shaped type to appear as the receiver
  1355  	// parameter (or first parameter, as a method expression). Hence
  1356  	// putting the dictionary parameter after that is the least invasive
  1357  	// solution at the moment.
  1358  	var args ir.Nodes
  1359  	if r.methodSym != nil {
  1360  		args.Append(params[0])
  1361  		params = params[1:]
  1362  	}
  1363  	args.Append(typecheck.Expr(ir.NewAddrExpr(pos, r.p.dictNameOf(r.dict))))
  1364  	args.Append(params...)
  1365  
  1366  	r.syntheticTailCall(pos, shapedFn, args)
  1367  }
  1368  
  1369  // syntheticArgs returns the recvs and params arguments passed to the
  1370  // current function.
  1371  func (r *reader) syntheticArgs() ir.Nodes {
  1372  	sig := r.curfn.Nname.Type()
  1373  	return ir.ToNodes(r.curfn.Dcl[:sig.NumRecvs()+sig.NumParams()])
  1374  }
  1375  
  1376  // syntheticTailCall emits a tail call to fn, passing the given
  1377  // arguments list.
  1378  func (r *reader) syntheticTailCall(pos src.XPos, fn ir.Node, args ir.Nodes) {
  1379  	// Mark the function as a wrapper so it doesn't show up in stack
  1380  	// traces.
  1381  	r.curfn.SetWrapper(true)
  1382  
  1383  	call := typecheck.Call(pos, fn, args, fn.Type().IsVariadic()).(*ir.CallExpr)
  1384  
  1385  	var stmt ir.Node
  1386  	if fn.Type().NumResults() != 0 {
  1387  		stmt = typecheck.Stmt(ir.NewReturnStmt(pos, []ir.Node{call}))
  1388  	} else {
  1389  		stmt = call
  1390  	}
  1391  	r.curfn.Body.Append(stmt)
  1392  }
  1393  
  1394  // dictNameOf returns the runtime dictionary corresponding to dict.
  1395  func (pr *pkgReader) dictNameOf(dict *readerDict) *ir.Name {
  1396  	pos := base.AutogeneratedPos
  1397  
  1398  	// Check that we only instantiate runtime dictionaries with real types.
  1399  	base.AssertfAt(!dict.shaped, pos, "runtime dictionary of shaped object %v", dict.baseSym)
  1400  
  1401  	sym := dict.baseSym.Pkg.Lookup(objabi.GlobalDictPrefix + "." + dict.baseSym.Name)
  1402  	if sym.Def != nil {
  1403  		return sym.Def.(*ir.Name)
  1404  	}
  1405  
  1406  	name := ir.NewNameAt(pos, sym, dict.varType())
  1407  	name.Class = ir.PEXTERN
  1408  	sym.Def = name // break cycles with mutual subdictionaries
  1409  
  1410  	lsym := name.Linksym()
  1411  	ot := 0
  1412  
  1413  	assertOffset := func(section string, offset int) {
  1414  		base.AssertfAt(ot == offset*types.PtrSize, pos, "writing section %v at offset %v, but it should be at %v*%v", section, ot, offset, types.PtrSize)
  1415  	}
  1416  
  1417  	assertOffset("type param method exprs", dict.typeParamMethodExprsOffset())
  1418  	for _, info := range dict.typeParamMethodExprs {
  1419  		typeParam := dict.targs[info.typeParamIdx]
  1420  		method := typecheck.NewMethodExpr(pos, typeParam, info.method)
  1421  
  1422  		rsym := method.FuncName().Linksym()
  1423  		assert(rsym.ABI() == obj.ABIInternal) // must be ABIInternal; see ir.OCFUNC in ssagen/ssa.go
  1424  
  1425  		ot = objw.SymPtr(lsym, ot, rsym, 0)
  1426  	}
  1427  
  1428  	assertOffset("subdictionaries", dict.subdictsOffset())
  1429  	for _, info := range dict.subdicts {
  1430  		explicits := pr.typListIdx(info.explicits, dict)
  1431  
  1432  		// Careful: Due to subdictionary cycles, name may not be fully
  1433  		// initialized yet.
  1434  		name := pr.objDictName(info.idx, dict.targs, explicits)
  1435  
  1436  		ot = objw.SymPtr(lsym, ot, name.Linksym(), 0)
  1437  	}
  1438  
  1439  	assertOffset("rtypes", dict.rtypesOffset())
  1440  	for _, info := range dict.rtypes {
  1441  		typ := pr.typIdx(info, dict, true)
  1442  		ot = objw.SymPtr(lsym, ot, reflectdata.TypeLinksym(typ), 0)
  1443  
  1444  		// TODO(mdempsky): Double check this.
  1445  		reflectdata.MarkTypeUsedInInterface(typ, lsym)
  1446  	}
  1447  
  1448  	// For each (typ, iface) pair, we write the *runtime.itab pointer
  1449  	// for the pair. For pairs that don't actually require an itab
  1450  	// (i.e., typ is an interface, or iface is an empty interface), we
  1451  	// write a nil pointer instead. This is wasteful, but rare in
  1452  	// practice (e.g., instantiating a type parameter with an interface
  1453  	// type).
  1454  	assertOffset("itabs", dict.itabsOffset())
  1455  	for _, info := range dict.itabs {
  1456  		typ := pr.typIdx(info.typ, dict, true)
  1457  		iface := pr.typIdx(info.iface, dict, true)
  1458  
  1459  		if !typ.IsInterface() && iface.IsInterface() && !iface.IsEmptyInterface() {
  1460  			ot = objw.SymPtr(lsym, ot, reflectdata.ITabLsym(typ, iface), 0)
  1461  		} else {
  1462  			ot += types.PtrSize
  1463  		}
  1464  
  1465  		// TODO(mdempsky): Double check this.
  1466  		reflectdata.MarkTypeUsedInInterface(typ, lsym)
  1467  		reflectdata.MarkTypeUsedInInterface(iface, lsym)
  1468  	}
  1469  
  1470  	objw.Global(lsym, int32(ot), obj.DUPOK|obj.RODATA)
  1471  
  1472  	return name
  1473  }
  1474  
  1475  // typeParamMethodExprsOffset returns the offset of the runtime
  1476  // dictionary's type parameter method expressions section, in words.
  1477  func (dict *readerDict) typeParamMethodExprsOffset() int {
  1478  	return 0
  1479  }
  1480  
  1481  // subdictsOffset returns the offset of the runtime dictionary's
  1482  // subdictionary section, in words.
  1483  func (dict *readerDict) subdictsOffset() int {
  1484  	return dict.typeParamMethodExprsOffset() + len(dict.typeParamMethodExprs)
  1485  }
  1486  
  1487  // rtypesOffset returns the offset of the runtime dictionary's rtypes
  1488  // section, in words.
  1489  func (dict *readerDict) rtypesOffset() int {
  1490  	return dict.subdictsOffset() + len(dict.subdicts)
  1491  }
  1492  
  1493  // itabsOffset returns the offset of the runtime dictionary's itabs
  1494  // section, in words.
  1495  func (dict *readerDict) itabsOffset() int {
  1496  	return dict.rtypesOffset() + len(dict.rtypes)
  1497  }
  1498  
  1499  // numWords returns the total number of words that comprise dict's
  1500  // runtime dictionary variable.
  1501  func (dict *readerDict) numWords() int64 {
  1502  	return int64(dict.itabsOffset() + len(dict.itabs))
  1503  }
  1504  
  1505  // varType returns the type of dict's runtime dictionary variable.
  1506  func (dict *readerDict) varType() *types.Type {
  1507  	return types.NewArray(types.Types[types.TUINTPTR], dict.numWords())
  1508  }
  1509  
  1510  func (r *reader) declareParams() {
  1511  	r.curfn.DeclareParams(!r.funarghack)
  1512  
  1513  	for _, name := range r.curfn.Dcl {
  1514  		if name.Sym().Name == dictParamName {
  1515  			r.dictParam = name
  1516  			continue
  1517  		}
  1518  
  1519  		r.addLocal(name)
  1520  	}
  1521  }
  1522  
  1523  func (r *reader) addLocal(name *ir.Name) {
  1524  	if r.synthetic == nil {
  1525  		r.Sync(pkgbits.SyncAddLocal)
  1526  		if r.p.SyncMarkers() {
  1527  			want := r.Int()
  1528  			if have := len(r.locals); have != want {
  1529  				base.FatalfAt(name.Pos(), "locals table has desynced")
  1530  			}
  1531  		}
  1532  		r.varDictIndex(name)
  1533  	}
  1534  
  1535  	r.locals = append(r.locals, name)
  1536  }
  1537  
  1538  func (r *reader) useLocal() *ir.Name {
  1539  	r.Sync(pkgbits.SyncUseObjLocal)
  1540  	if r.Bool() {
  1541  		return r.locals[r.Len()]
  1542  	}
  1543  	return r.closureVars[r.Len()]
  1544  }
  1545  
  1546  func (r *reader) openScope() {
  1547  	r.Sync(pkgbits.SyncOpenScope)
  1548  	pos := r.pos()
  1549  
  1550  	if base.Flag.Dwarf {
  1551  		r.scopeVars = append(r.scopeVars, len(r.curfn.Dcl))
  1552  		r.marker.Push(pos)
  1553  	}
  1554  }
  1555  
  1556  func (r *reader) closeScope() {
  1557  	r.Sync(pkgbits.SyncCloseScope)
  1558  	r.lastCloseScopePos = r.pos()
  1559  
  1560  	r.closeAnotherScope()
  1561  }
  1562  
  1563  // closeAnotherScope is like closeScope, but it reuses the same mark
  1564  // position as the last closeScope call. This is useful for "for" and
  1565  // "if" statements, as their implicit blocks always end at the same
  1566  // position as an explicit block.
  1567  func (r *reader) closeAnotherScope() {
  1568  	r.Sync(pkgbits.SyncCloseAnotherScope)
  1569  
  1570  	if base.Flag.Dwarf {
  1571  		scopeVars := r.scopeVars[len(r.scopeVars)-1]
  1572  		r.scopeVars = r.scopeVars[:len(r.scopeVars)-1]
  1573  
  1574  		// Quirkish: noder decides which scopes to keep before
  1575  		// typechecking, whereas incremental typechecking during IR
  1576  		// construction can result in new autotemps being allocated. To
  1577  		// produce identical output, we ignore autotemps here for the
  1578  		// purpose of deciding whether to retract the scope.
  1579  		//
  1580  		// This is important for net/http/fcgi, because it contains:
  1581  		//
  1582  		//	var body io.ReadCloser
  1583  		//	if len(content) > 0 {
  1584  		//		body, req.pw = io.Pipe()
  1585  		//	} else { … }
  1586  		//
  1587  		// Notably, io.Pipe is inlinable, and inlining it introduces a ~R0
  1588  		// variable at the call site.
  1589  		//
  1590  		// Noder does not preserve the scope where the io.Pipe() call
  1591  		// resides, because it doesn't contain any declared variables in
  1592  		// source. So the ~R0 variable ends up being assigned to the
  1593  		// enclosing scope instead.
  1594  		//
  1595  		// However, typechecking this assignment also introduces
  1596  		// autotemps, because io.Pipe's results need conversion before
  1597  		// they can be assigned to their respective destination variables.
  1598  		//
  1599  		// TODO(mdempsky): We should probably just keep all scopes, and
  1600  		// let dwarfgen take care of pruning them instead.
  1601  		retract := true
  1602  		for _, n := range r.curfn.Dcl[scopeVars:] {
  1603  			if !n.AutoTemp() {
  1604  				retract = false
  1605  				break
  1606  			}
  1607  		}
  1608  
  1609  		if retract {
  1610  			// no variables were declared in this scope, so we can retract it.
  1611  			r.marker.Unpush()
  1612  		} else {
  1613  			r.marker.Pop(r.lastCloseScopePos)
  1614  		}
  1615  	}
  1616  }
  1617  
  1618  // @@@ Statements
  1619  
  1620  func (r *reader) stmt() ir.Node {
  1621  	return block(r.stmts())
  1622  }
  1623  
  1624  func block(stmts []ir.Node) ir.Node {
  1625  	switch len(stmts) {
  1626  	case 0:
  1627  		return nil
  1628  	case 1:
  1629  		return stmts[0]
  1630  	default:
  1631  		return ir.NewBlockStmt(stmts[0].Pos(), stmts)
  1632  	}
  1633  }
  1634  
  1635  func (r *reader) stmts() ir.Nodes {
  1636  	assert(ir.CurFunc == r.curfn)
  1637  	var res ir.Nodes
  1638  
  1639  	r.Sync(pkgbits.SyncStmts)
  1640  	for {
  1641  		tag := codeStmt(r.Code(pkgbits.SyncStmt1))
  1642  		if tag == stmtEnd {
  1643  			r.Sync(pkgbits.SyncStmtsEnd)
  1644  			return res
  1645  		}
  1646  
  1647  		if n := r.stmt1(tag, &res); n != nil {
  1648  			res.Append(typecheck.Stmt(n))
  1649  		}
  1650  	}
  1651  }
  1652  
  1653  func (r *reader) stmt1(tag codeStmt, out *ir.Nodes) ir.Node {
  1654  	var label *types.Sym
  1655  	if n := len(*out); n > 0 {
  1656  		if ls, ok := (*out)[n-1].(*ir.LabelStmt); ok {
  1657  			label = ls.Label
  1658  		}
  1659  	}
  1660  
  1661  	switch tag {
  1662  	default:
  1663  		panic("unexpected statement")
  1664  
  1665  	case stmtAssign:
  1666  		pos := r.pos()
  1667  		names, lhs := r.assignList()
  1668  		rhs := r.multiExpr()
  1669  
  1670  		if len(rhs) == 0 {
  1671  			for _, name := range names {
  1672  				as := ir.NewAssignStmt(pos, name, nil)
  1673  				as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, name))
  1674  				out.Append(typecheck.Stmt(as))
  1675  			}
  1676  			return nil
  1677  		}
  1678  
  1679  		if len(lhs) == 1 && len(rhs) == 1 {
  1680  			n := ir.NewAssignStmt(pos, lhs[0], rhs[0])
  1681  			n.Def = r.initDefn(n, names)
  1682  			return n
  1683  		}
  1684  
  1685  		n := ir.NewAssignListStmt(pos, ir.OAS2, lhs, rhs)
  1686  		n.Def = r.initDefn(n, names)
  1687  		return n
  1688  
  1689  	case stmtAssignOp:
  1690  		op := r.op()
  1691  		lhs := r.expr()
  1692  		pos := r.pos()
  1693  		rhs := r.expr()
  1694  		return ir.NewAssignOpStmt(pos, op, lhs, rhs)
  1695  
  1696  	case stmtIncDec:
  1697  		op := r.op()
  1698  		lhs := r.expr()
  1699  		pos := r.pos()
  1700  		n := ir.NewAssignOpStmt(pos, op, lhs, ir.NewOne(pos, lhs.Type()))
  1701  		n.IncDec = true
  1702  		return n
  1703  
  1704  	case stmtBlock:
  1705  		out.Append(r.blockStmt()...)
  1706  		return nil
  1707  
  1708  	case stmtBranch:
  1709  		pos := r.pos()
  1710  		op := r.op()
  1711  		sym := r.optLabel()
  1712  		return ir.NewBranchStmt(pos, op, sym)
  1713  
  1714  	case stmtCall:
  1715  		pos := r.pos()
  1716  		op := r.op()
  1717  		call := r.expr()
  1718  		stmt := ir.NewGoDeferStmt(pos, op, call)
  1719  		if op == ir.ODEFER {
  1720  			x := r.optExpr()
  1721  			if x != nil {
  1722  				stmt.DeferAt = x.(ir.Expr)
  1723  			}
  1724  		}
  1725  		return stmt
  1726  
  1727  	case stmtExpr:
  1728  		return r.expr()
  1729  
  1730  	case stmtFor:
  1731  		return r.forStmt(label)
  1732  
  1733  	case stmtIf:
  1734  		return r.ifStmt()
  1735  
  1736  	case stmtLabel:
  1737  		pos := r.pos()
  1738  		sym := r.label()
  1739  		return ir.NewLabelStmt(pos, sym)
  1740  
  1741  	case stmtReturn:
  1742  		pos := r.pos()
  1743  		results := r.multiExpr()
  1744  		return ir.NewReturnStmt(pos, results)
  1745  
  1746  	case stmtSelect:
  1747  		return r.selectStmt(label)
  1748  
  1749  	case stmtSend:
  1750  		pos := r.pos()
  1751  		ch := r.expr()
  1752  		value := r.expr()
  1753  		return ir.NewSendStmt(pos, ch, value)
  1754  
  1755  	case stmtSwitch:
  1756  		return r.switchStmt(label)
  1757  	}
  1758  }
  1759  
  1760  func (r *reader) assignList() ([]*ir.Name, []ir.Node) {
  1761  	lhs := make([]ir.Node, r.Len())
  1762  	var names []*ir.Name
  1763  
  1764  	for i := range lhs {
  1765  		expr, def := r.assign()
  1766  		lhs[i] = expr
  1767  		if def {
  1768  			names = append(names, expr.(*ir.Name))
  1769  		}
  1770  	}
  1771  
  1772  	return names, lhs
  1773  }
  1774  
  1775  // assign returns an assignee expression. It also reports whether the
  1776  // returned expression is a newly declared variable.
  1777  func (r *reader) assign() (ir.Node, bool) {
  1778  	switch tag := codeAssign(r.Code(pkgbits.SyncAssign)); tag {
  1779  	default:
  1780  		panic("unhandled assignee expression")
  1781  
  1782  	case assignBlank:
  1783  		return typecheck.AssignExpr(ir.BlankNode), false
  1784  
  1785  	case assignDef:
  1786  		pos := r.pos()
  1787  		setBasePos(pos) // test/fixedbugs/issue49767.go depends on base.Pos being set for the r.typ() call here, ugh
  1788  		name := r.curfn.NewLocal(pos, r.localIdent(), r.typ())
  1789  		r.addLocal(name)
  1790  		return name, true
  1791  
  1792  	case assignExpr:
  1793  		return r.expr(), false
  1794  	}
  1795  }
  1796  
  1797  func (r *reader) blockStmt() []ir.Node {
  1798  	r.Sync(pkgbits.SyncBlockStmt)
  1799  	r.openScope()
  1800  	stmts := r.stmts()
  1801  	r.closeScope()
  1802  	return stmts
  1803  }
  1804  
  1805  func (r *reader) forStmt(label *types.Sym) ir.Node {
  1806  	r.Sync(pkgbits.SyncForStmt)
  1807  
  1808  	r.openScope()
  1809  
  1810  	if r.Bool() {
  1811  		pos := r.pos()
  1812  		rang := ir.NewRangeStmt(pos, nil, nil, nil, nil, false)
  1813  		rang.Label = label
  1814  
  1815  		names, lhs := r.assignList()
  1816  		if len(lhs) >= 1 {
  1817  			rang.Key = lhs[0]
  1818  			if len(lhs) >= 2 {
  1819  				rang.Value = lhs[1]
  1820  			}
  1821  		}
  1822  		rang.Def = r.initDefn(rang, names)
  1823  
  1824  		rang.X = r.expr()
  1825  		if rang.X.Type().IsMap() {
  1826  			rang.RType = r.rtype(pos)
  1827  		}
  1828  		if rang.Key != nil && !ir.IsBlank(rang.Key) {
  1829  			rang.KeyTypeWord, rang.KeySrcRType = r.convRTTI(pos)
  1830  		}
  1831  		if rang.Value != nil && !ir.IsBlank(rang.Value) {
  1832  			rang.ValueTypeWord, rang.ValueSrcRType = r.convRTTI(pos)
  1833  		}
  1834  
  1835  		rang.Body = r.blockStmt()
  1836  		rang.DistinctVars = r.Bool()
  1837  		r.closeAnotherScope()
  1838  
  1839  		return rang
  1840  	}
  1841  
  1842  	pos := r.pos()
  1843  	init := r.stmt()
  1844  	cond := r.optExpr()
  1845  	post := r.stmt()
  1846  	body := r.blockStmt()
  1847  	perLoopVars := r.Bool()
  1848  	r.closeAnotherScope()
  1849  
  1850  	if ir.IsConst(cond, constant.Bool) && !ir.BoolVal(cond) {
  1851  		return init // simplify "for init; false; post { ... }" into "init"
  1852  	}
  1853  
  1854  	stmt := ir.NewForStmt(pos, init, cond, post, body, perLoopVars)
  1855  	stmt.Label = label
  1856  	return stmt
  1857  }
  1858  
  1859  func (r *reader) ifStmt() ir.Node {
  1860  	r.Sync(pkgbits.SyncIfStmt)
  1861  	r.openScope()
  1862  	pos := r.pos()
  1863  	init := r.stmts()
  1864  	cond := r.expr()
  1865  	staticCond := r.Int()
  1866  	var then, els []ir.Node
  1867  	if staticCond >= 0 {
  1868  		then = r.blockStmt()
  1869  	} else {
  1870  		r.lastCloseScopePos = r.pos()
  1871  	}
  1872  	if staticCond <= 0 {
  1873  		els = r.stmts()
  1874  	}
  1875  	r.closeAnotherScope()
  1876  
  1877  	if staticCond != 0 {
  1878  		// We may have removed a dead return statement, which can trip up
  1879  		// later passes (#62211). To avoid confusion, we instead flatten
  1880  		// the if statement into a block.
  1881  
  1882  		if cond.Op() != ir.OLITERAL {
  1883  			init.Append(typecheck.Stmt(ir.NewAssignStmt(pos, ir.BlankNode, cond))) // for side effects
  1884  		}
  1885  		init.Append(then...)
  1886  		init.Append(els...)
  1887  		return block(init)
  1888  	}
  1889  
  1890  	n := ir.NewIfStmt(pos, cond, then, els)
  1891  	n.SetInit(init)
  1892  	return n
  1893  }
  1894  
  1895  func (r *reader) selectStmt(label *types.Sym) ir.Node {
  1896  	r.Sync(pkgbits.SyncSelectStmt)
  1897  
  1898  	pos := r.pos()
  1899  	clauses := make([]*ir.CommClause, r.Len())
  1900  	for i := range clauses {
  1901  		if i > 0 {
  1902  			r.closeScope()
  1903  		}
  1904  		r.openScope()
  1905  
  1906  		pos := r.pos()
  1907  		comm := r.stmt()
  1908  		body := r.stmts()
  1909  
  1910  		// "case i = <-c: ..." may require an implicit conversion (e.g.,
  1911  		// see fixedbugs/bug312.go). Currently, typecheck throws away the
  1912  		// implicit conversion and relies on it being reinserted later,
  1913  		// but that would lose any explicit RTTI operands too. To preserve
  1914  		// RTTI, we rewrite this as "case tmp := <-c: i = tmp; ...".
  1915  		if as, ok := comm.(*ir.AssignStmt); ok && as.Op() == ir.OAS && !as.Def {
  1916  			if conv, ok := as.Y.(*ir.ConvExpr); ok && conv.Op() == ir.OCONVIFACE {
  1917  				base.AssertfAt(conv.Implicit(), conv.Pos(), "expected implicit conversion: %v", conv)
  1918  
  1919  				recv := conv.X
  1920  				base.AssertfAt(recv.Op() == ir.ORECV, recv.Pos(), "expected receive expression: %v", recv)
  1921  
  1922  				tmp := r.temp(pos, recv.Type())
  1923  
  1924  				// Replace comm with `tmp := <-c`.
  1925  				tmpAs := ir.NewAssignStmt(pos, tmp, recv)
  1926  				tmpAs.Def = true
  1927  				tmpAs.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
  1928  				comm = tmpAs
  1929  
  1930  				// Change original assignment to `i = tmp`, and prepend to body.
  1931  				conv.X = tmp
  1932  				body = append([]ir.Node{as}, body...)
  1933  			}
  1934  		}
  1935  
  1936  		// multiExpr will have desugared a comma-ok receive expression
  1937  		// into a separate statement. However, the rest of the compiler
  1938  		// expects comm to be the OAS2RECV statement itself, so we need to
  1939  		// shuffle things around to fit that pattern.
  1940  		if as2, ok := comm.(*ir.AssignListStmt); ok && as2.Op() == ir.OAS2 {
  1941  			init := ir.TakeInit(as2.Rhs[0])
  1942  			base.AssertfAt(len(init) == 1 && init[0].Op() == ir.OAS2RECV, as2.Pos(), "unexpected assignment: %+v", as2)
  1943  
  1944  			comm = init[0]
  1945  			body = append([]ir.Node{as2}, body...)
  1946  		}
  1947  
  1948  		clauses[i] = ir.NewCommStmt(pos, comm, body)
  1949  	}
  1950  	if len(clauses) > 0 {
  1951  		r.closeScope()
  1952  	}
  1953  	n := ir.NewSelectStmt(pos, clauses)
  1954  	n.Label = label
  1955  	return n
  1956  }
  1957  
  1958  func (r *reader) switchStmt(label *types.Sym) ir.Node {
  1959  	r.Sync(pkgbits.SyncSwitchStmt)
  1960  
  1961  	r.openScope()
  1962  	pos := r.pos()
  1963  	init := r.stmt()
  1964  
  1965  	var tag ir.Node
  1966  	var ident *ir.Ident
  1967  	var iface *types.Type
  1968  	if r.Bool() {
  1969  		pos := r.pos()
  1970  		if r.Bool() {
  1971  			ident = ir.NewIdent(r.pos(), r.localIdent())
  1972  		}
  1973  		x := r.expr()
  1974  		iface = x.Type()
  1975  		tag = ir.NewTypeSwitchGuard(pos, ident, x)
  1976  	} else {
  1977  		tag = r.optExpr()
  1978  	}
  1979  
  1980  	clauses := make([]*ir.CaseClause, r.Len())
  1981  	for i := range clauses {
  1982  		if i > 0 {
  1983  			r.closeScope()
  1984  		}
  1985  		r.openScope()
  1986  
  1987  		pos := r.pos()
  1988  		var cases, rtypes []ir.Node
  1989  		if iface != nil {
  1990  			cases = make([]ir.Node, r.Len())
  1991  			if len(cases) == 0 {
  1992  				cases = nil // TODO(mdempsky): Unclear if this matters.
  1993  			}
  1994  			for i := range cases {
  1995  				if r.Bool() { // case nil
  1996  					cases[i] = typecheck.Expr(types.BuiltinPkg.Lookup("nil").Def.(*ir.NilExpr))
  1997  				} else {
  1998  					cases[i] = r.exprType()
  1999  				}
  2000  			}
  2001  		} else {
  2002  			cases = r.exprList()
  2003  
  2004  			// For `switch { case any(true): }` (e.g., issue 3980 in
  2005  			// test/switch.go), the backend still creates a mixed bool/any
  2006  			// comparison, and we need to explicitly supply the RTTI for the
  2007  			// comparison.
  2008  			//
  2009  			// TODO(mdempsky): Change writer.go to desugar "switch {" into
  2010  			// "switch true {", which we already handle correctly.
  2011  			if tag == nil {
  2012  				for i, cas := range cases {
  2013  					if cas.Type().IsEmptyInterface() {
  2014  						for len(rtypes) < i {
  2015  							rtypes = append(rtypes, nil)
  2016  						}
  2017  						rtypes = append(rtypes, reflectdata.TypePtrAt(cas.Pos(), types.Types[types.TBOOL]))
  2018  					}
  2019  				}
  2020  			}
  2021  		}
  2022  
  2023  		clause := ir.NewCaseStmt(pos, cases, nil)
  2024  		clause.RTypes = rtypes
  2025  
  2026  		if ident != nil {
  2027  			name := r.curfn.NewLocal(r.pos(), ident.Sym(), r.typ())
  2028  			r.addLocal(name)
  2029  			clause.Var = name
  2030  			name.Defn = tag
  2031  		}
  2032  
  2033  		clause.Body = r.stmts()
  2034  		clauses[i] = clause
  2035  	}
  2036  	if len(clauses) > 0 {
  2037  		r.closeScope()
  2038  	}
  2039  	r.closeScope()
  2040  
  2041  	n := ir.NewSwitchStmt(pos, tag, clauses)
  2042  	n.Label = label
  2043  	if init != nil {
  2044  		n.SetInit([]ir.Node{init})
  2045  	}
  2046  	return n
  2047  }
  2048  
  2049  func (r *reader) label() *types.Sym {
  2050  	r.Sync(pkgbits.SyncLabel)
  2051  	name := r.String()
  2052  	if r.inlCall != nil {
  2053  		name = fmt.Sprintf("~%s·%d", name, inlgen)
  2054  	}
  2055  	return typecheck.Lookup(name)
  2056  }
  2057  
  2058  func (r *reader) optLabel() *types.Sym {
  2059  	r.Sync(pkgbits.SyncOptLabel)
  2060  	if r.Bool() {
  2061  		return r.label()
  2062  	}
  2063  	return nil
  2064  }
  2065  
  2066  // initDefn marks the given names as declared by defn and populates
  2067  // its Init field with ODCL nodes. It then reports whether any names
  2068  // were so declared, which can be used to initialize defn.Def.
  2069  func (r *reader) initDefn(defn ir.InitNode, names []*ir.Name) bool {
  2070  	if len(names) == 0 {
  2071  		return false
  2072  	}
  2073  
  2074  	init := make([]ir.Node, len(names))
  2075  	for i, name := range names {
  2076  		name.Defn = defn
  2077  		init[i] = ir.NewDecl(name.Pos(), ir.ODCL, name)
  2078  	}
  2079  	defn.SetInit(init)
  2080  	return true
  2081  }
  2082  
  2083  // @@@ Expressions
  2084  
  2085  // expr reads and returns a typechecked expression.
  2086  func (r *reader) expr() (res ir.Node) {
  2087  	defer func() {
  2088  		if res != nil && res.Typecheck() == 0 {
  2089  			base.FatalfAt(res.Pos(), "%v missed typecheck", res)
  2090  		}
  2091  	}()
  2092  
  2093  	switch tag := codeExpr(r.Code(pkgbits.SyncExpr)); tag {
  2094  	default:
  2095  		panic("unhandled expression")
  2096  
  2097  	case exprLocal:
  2098  		return typecheck.Expr(r.useLocal())
  2099  
  2100  	case exprGlobal:
  2101  		// Callee instead of Expr allows builtins
  2102  		// TODO(mdempsky): Handle builtins directly in exprCall, like method calls?
  2103  		return typecheck.Callee(r.obj())
  2104  
  2105  	case exprFuncInst:
  2106  		origPos, pos := r.origPos()
  2107  		wrapperFn, baseFn, dictPtr := r.funcInst(pos)
  2108  		if wrapperFn != nil {
  2109  			return wrapperFn
  2110  		}
  2111  		return r.curry(origPos, false, baseFn, dictPtr, nil)
  2112  
  2113  	case exprConst:
  2114  		pos := r.pos()
  2115  		typ := r.typ()
  2116  		val := FixValue(typ, r.Value())
  2117  		return ir.NewBasicLit(pos, typ, val)
  2118  
  2119  	case exprZero:
  2120  		pos := r.pos()
  2121  		typ := r.typ()
  2122  		return ir.NewZero(pos, typ)
  2123  
  2124  	case exprCompLit:
  2125  		return r.compLit()
  2126  
  2127  	case exprFuncLit:
  2128  		return r.funcLit()
  2129  
  2130  	case exprFieldVal:
  2131  		x := r.expr()
  2132  		pos := r.pos()
  2133  		sym := r.selector()
  2134  
  2135  		return typecheck.XDotField(pos, x, sym)
  2136  
  2137  	case exprMethodVal:
  2138  		recv := r.expr()
  2139  		origPos, pos := r.origPos()
  2140  		wrapperFn, baseFn, dictPtr := r.methodExpr()
  2141  
  2142  		// For simple wrapperFn values, the existing machinery for creating
  2143  		// and deduplicating wrapperFn value wrappers still works fine.
  2144  		if wrapperFn, ok := wrapperFn.(*ir.SelectorExpr); ok && wrapperFn.Op() == ir.OMETHEXPR {
  2145  			// The receiver expression we constructed may have a shape type.
  2146  			// For example, in fixedbugs/issue54343.go, `New[int]()` is
  2147  			// constructed as `New[go.shape.int](&.dict.New[int])`, which
  2148  			// has type `*T[go.shape.int]`, not `*T[int]`.
  2149  			//
  2150  			// However, the method we want to select here is `(*T[int]).M`,
  2151  			// not `(*T[go.shape.int]).M`, so we need to manually convert
  2152  			// the type back so that the OXDOT resolves correctly.
  2153  			//
  2154  			// TODO(mdempsky): Logically it might make more sense for
  2155  			// exprCall to take responsibility for setting a non-shaped
  2156  			// result type, but this is the only place where we care
  2157  			// currently. And only because existing ir.OMETHVALUE backend
  2158  			// code relies on n.X.Type() instead of n.Selection.Recv().Type
  2159  			// (because the latter is types.FakeRecvType() in the case of
  2160  			// interface method values).
  2161  			//
  2162  			if recv.Type().HasShape() {
  2163  				typ := wrapperFn.Type().Param(0).Type
  2164  				if !types.Identical(typ, recv.Type()) {
  2165  					base.FatalfAt(wrapperFn.Pos(), "receiver %L does not match %L", recv, wrapperFn)
  2166  				}
  2167  				recv = typecheck.Expr(ir.NewConvExpr(recv.Pos(), ir.OCONVNOP, typ, recv))
  2168  			}
  2169  
  2170  			n := typecheck.XDotMethod(pos, recv, wrapperFn.Sel, false)
  2171  
  2172  			// As a consistency check here, we make sure "n" selected the
  2173  			// same method (represented by a types.Field) that wrapperFn
  2174  			// selected. However, for anonymous receiver types, there can be
  2175  			// multiple such types.Field instances (#58563). So we may need
  2176  			// to fallback to making sure Sym and Type (including the
  2177  			// receiver parameter's type) match.
  2178  			if n.Selection != wrapperFn.Selection {
  2179  				assert(n.Selection.Sym == wrapperFn.Selection.Sym)
  2180  				assert(types.Identical(n.Selection.Type, wrapperFn.Selection.Type))
  2181  				assert(types.Identical(n.Selection.Type.Recv().Type, wrapperFn.Selection.Type.Recv().Type))
  2182  			}
  2183  
  2184  			wrapper := methodValueWrapper{
  2185  				rcvr:   n.X.Type(),
  2186  				method: n.Selection,
  2187  			}
  2188  
  2189  			if r.importedDef() {
  2190  				haveMethodValueWrappers = append(haveMethodValueWrappers, wrapper)
  2191  			} else {
  2192  				needMethodValueWrappers = append(needMethodValueWrappers, wrapper)
  2193  			}
  2194  			return n
  2195  		}
  2196  
  2197  		// For more complicated method expressions, we construct a
  2198  		// function literal wrapper.
  2199  		return r.curry(origPos, true, baseFn, recv, dictPtr)
  2200  
  2201  	case exprMethodExpr:
  2202  		recv := r.typ()
  2203  
  2204  		implicits := make([]int, r.Len())
  2205  		for i := range implicits {
  2206  			implicits[i] = r.Len()
  2207  		}
  2208  		var deref, addr bool
  2209  		if r.Bool() {
  2210  			deref = true
  2211  		} else if r.Bool() {
  2212  			addr = true
  2213  		}
  2214  
  2215  		origPos, pos := r.origPos()
  2216  		wrapperFn, baseFn, dictPtr := r.methodExpr()
  2217  
  2218  		// If we already have a wrapper and don't need to do anything with
  2219  		// it, we can just return the wrapper directly.
  2220  		//
  2221  		// N.B., we use implicits/deref/addr here as the source of truth
  2222  		// rather than types.Identical, because the latter can be confused
  2223  		// by tricky promoted methods (e.g., typeparam/mdempsky/21.go).
  2224  		if wrapperFn != nil && len(implicits) == 0 && !deref && !addr {
  2225  			if !types.Identical(recv, wrapperFn.Type().Param(0).Type) {
  2226  				base.FatalfAt(pos, "want receiver type %v, but have method %L", recv, wrapperFn)
  2227  			}
  2228  			return wrapperFn
  2229  		}
  2230  
  2231  		// Otherwise, if the wrapper function is a static method
  2232  		// expression (OMETHEXPR) and the receiver type is unshaped, then
  2233  		// we can rely on a statically generated wrapper being available.
  2234  		if method, ok := wrapperFn.(*ir.SelectorExpr); ok && method.Op() == ir.OMETHEXPR && !recv.HasShape() {
  2235  			return typecheck.NewMethodExpr(pos, recv, method.Sel)
  2236  		}
  2237  
  2238  		return r.methodExprWrap(origPos, recv, implicits, deref, addr, baseFn, dictPtr)
  2239  
  2240  	case exprIndex:
  2241  		x := r.expr()
  2242  		pos := r.pos()
  2243  		index := r.expr()
  2244  		n := typecheck.Expr(ir.NewIndexExpr(pos, x, index))
  2245  		switch n.Op() {
  2246  		case ir.OINDEXMAP:
  2247  			n := n.(*ir.IndexExpr)
  2248  			n.RType = r.rtype(pos)
  2249  		}
  2250  		return n
  2251  
  2252  	case exprSlice:
  2253  		x := r.expr()
  2254  		pos := r.pos()
  2255  		var index [3]ir.Node
  2256  		for i := range index {
  2257  			index[i] = r.optExpr()
  2258  		}
  2259  		op := ir.OSLICE
  2260  		if index[2] != nil {
  2261  			op = ir.OSLICE3
  2262  		}
  2263  		return typecheck.Expr(ir.NewSliceExpr(pos, op, x, index[0], index[1], index[2]))
  2264  
  2265  	case exprAssert:
  2266  		x := r.expr()
  2267  		pos := r.pos()
  2268  		typ := r.exprType()
  2269  		srcRType := r.rtype(pos)
  2270  
  2271  		// TODO(mdempsky): Always emit ODYNAMICDOTTYPE for uniformity?
  2272  		if typ, ok := typ.(*ir.DynamicType); ok && typ.Op() == ir.ODYNAMICTYPE {
  2273  			assert := ir.NewDynamicTypeAssertExpr(pos, ir.ODYNAMICDOTTYPE, x, typ.RType)
  2274  			assert.SrcRType = srcRType
  2275  			assert.ITab = typ.ITab
  2276  			return typed(typ.Type(), assert)
  2277  		}
  2278  		return typecheck.Expr(ir.NewTypeAssertExpr(pos, x, typ.Type()))
  2279  
  2280  	case exprUnaryOp:
  2281  		op := r.op()
  2282  		pos := r.pos()
  2283  		x := r.expr()
  2284  
  2285  		switch op {
  2286  		case ir.OADDR:
  2287  			return typecheck.Expr(typecheck.NodAddrAt(pos, x))
  2288  		case ir.ODEREF:
  2289  			return typecheck.Expr(ir.NewStarExpr(pos, x))
  2290  		}
  2291  		return typecheck.Expr(ir.NewUnaryExpr(pos, op, x))
  2292  
  2293  	case exprBinaryOp:
  2294  		op := r.op()
  2295  		x := r.expr()
  2296  		pos := r.pos()
  2297  		y := r.expr()
  2298  
  2299  		switch op {
  2300  		case ir.OANDAND, ir.OOROR:
  2301  			return typecheck.Expr(ir.NewLogicalExpr(pos, op, x, y))
  2302  		case ir.OLSH, ir.ORSH:
  2303  			// Untyped rhs of non-constant shift, e.g. x << 1.0.
  2304  			// If we have a constant value, it must be an int >= 0.
  2305  			if ir.IsConstNode(y) {
  2306  				val := constant.ToInt(y.Val())
  2307  				assert(val.Kind() == constant.Int && constant.Sign(val) >= 0)
  2308  			}
  2309  		}
  2310  		return typecheck.Expr(ir.NewBinaryExpr(pos, op, x, y))
  2311  
  2312  	case exprRecv:
  2313  		x := r.expr()
  2314  		pos := r.pos()
  2315  		for i, n := 0, r.Len(); i < n; i++ {
  2316  			x = Implicit(typecheck.DotField(pos, x, r.Len()))
  2317  		}
  2318  		if r.Bool() { // needs deref
  2319  			x = Implicit(Deref(pos, x.Type().Elem(), x))
  2320  		} else if r.Bool() { // needs addr
  2321  			x = Implicit(Addr(pos, x))
  2322  		}
  2323  		return x
  2324  
  2325  	case exprCall:
  2326  		var fun ir.Node
  2327  		var args ir.Nodes
  2328  		if r.Bool() { // method call
  2329  			recv := r.expr()
  2330  			_, method, dictPtr := r.methodExpr()
  2331  
  2332  			if recv.Type().IsInterface() && method.Op() == ir.OMETHEXPR {
  2333  				method := method.(*ir.SelectorExpr)
  2334  
  2335  				// The compiler backend (e.g., devirtualization) handle
  2336  				// OCALLINTER/ODOTINTER better than OCALLFUNC/OMETHEXPR for
  2337  				// interface calls, so we prefer to continue constructing
  2338  				// calls that way where possible.
  2339  				//
  2340  				// There are also corner cases where semantically it's perhaps
  2341  				// significant; e.g., fixedbugs/issue15975.go, #38634, #52025.
  2342  
  2343  				fun = typecheck.XDotMethod(method.Pos(), recv, method.Sel, true)
  2344  			} else {
  2345  				if recv.Type().IsInterface() {
  2346  					// N.B., this happens currently for typeparam/issue51521.go
  2347  					// and typeparam/typeswitch3.go.
  2348  					if base.Flag.LowerM != 0 {
  2349  						base.WarnfAt(method.Pos(), "imprecise interface call")
  2350  					}
  2351  				}
  2352  
  2353  				fun = method
  2354  				args.Append(recv)
  2355  			}
  2356  			if dictPtr != nil {
  2357  				args.Append(dictPtr)
  2358  			}
  2359  		} else if r.Bool() { // call to instanced function
  2360  			pos := r.pos()
  2361  			_, shapedFn, dictPtr := r.funcInst(pos)
  2362  			fun = shapedFn
  2363  			args.Append(dictPtr)
  2364  		} else {
  2365  			fun = r.expr()
  2366  		}
  2367  		pos := r.pos()
  2368  		args.Append(r.multiExpr()...)
  2369  		dots := r.Bool()
  2370  		n := typecheck.Call(pos, fun, args, dots)
  2371  		switch n.Op() {
  2372  		case ir.OAPPEND:
  2373  			n := n.(*ir.CallExpr)
  2374  			n.RType = r.rtype(pos)
  2375  			// For append(a, b...), we don't need the implicit conversion. The typechecker already
  2376  			// ensured that a and b are both slices with the same base type, or []byte and string.
  2377  			if n.IsDDD {
  2378  				if conv, ok := n.Args[1].(*ir.ConvExpr); ok && conv.Op() == ir.OCONVNOP && conv.Implicit() {
  2379  					n.Args[1] = conv.X
  2380  				}
  2381  			}
  2382  		case ir.OCOPY:
  2383  			n := n.(*ir.BinaryExpr)
  2384  			n.RType = r.rtype(pos)
  2385  		case ir.ODELETE:
  2386  			n := n.(*ir.CallExpr)
  2387  			n.RType = r.rtype(pos)
  2388  		case ir.OUNSAFESLICE:
  2389  			n := n.(*ir.BinaryExpr)
  2390  			n.RType = r.rtype(pos)
  2391  		}
  2392  		return n
  2393  
  2394  	case exprMake:
  2395  		pos := r.pos()
  2396  		typ := r.exprType()
  2397  		extra := r.exprs()
  2398  		n := typecheck.Expr(ir.NewCallExpr(pos, ir.OMAKE, nil, append([]ir.Node{typ}, extra...))).(*ir.MakeExpr)
  2399  		n.RType = r.rtype(pos)
  2400  		return n
  2401  
  2402  	case exprNew:
  2403  		pos := r.pos()
  2404  		typ := r.exprType()
  2405  		return typecheck.Expr(ir.NewUnaryExpr(pos, ir.ONEW, typ))
  2406  
  2407  	case exprSizeof:
  2408  		return ir.NewUintptr(r.pos(), r.typ().Size())
  2409  
  2410  	case exprAlignof:
  2411  		return ir.NewUintptr(r.pos(), r.typ().Alignment())
  2412  
  2413  	case exprOffsetof:
  2414  		pos := r.pos()
  2415  		typ := r.typ()
  2416  		types.CalcSize(typ)
  2417  
  2418  		var offset int64
  2419  		for i := r.Len(); i >= 0; i-- {
  2420  			field := typ.Field(r.Len())
  2421  			offset += field.Offset
  2422  			typ = field.Type
  2423  		}
  2424  
  2425  		return ir.NewUintptr(pos, offset)
  2426  
  2427  	case exprReshape:
  2428  		typ := r.typ()
  2429  		x := r.expr()
  2430  
  2431  		if types.IdenticalStrict(x.Type(), typ) {
  2432  			return x
  2433  		}
  2434  
  2435  		// Comparison expressions are constructed as "untyped bool" still.
  2436  		//
  2437  		// TODO(mdempsky): It should be safe to reshape them here too, but
  2438  		// maybe it's better to construct them with the proper type
  2439  		// instead.
  2440  		if x.Type() == types.UntypedBool && typ.IsBoolean() {
  2441  			return x
  2442  		}
  2443  
  2444  		base.AssertfAt(x.Type().HasShape() || typ.HasShape(), x.Pos(), "%L and %v are not shape types", x, typ)
  2445  		base.AssertfAt(types.Identical(x.Type(), typ), x.Pos(), "%L is not shape-identical to %v", x, typ)
  2446  
  2447  		// We use ir.HasUniquePos here as a check that x only appears once
  2448  		// in the AST, so it's okay for us to call SetType without
  2449  		// breaking any other uses of it.
  2450  		//
  2451  		// Notably, any ONAMEs should already have the exactly right shape
  2452  		// type and been caught by types.IdenticalStrict above.
  2453  		base.AssertfAt(ir.HasUniquePos(x), x.Pos(), "cannot call SetType(%v) on %L", typ, x)
  2454  
  2455  		if base.Debug.Reshape != 0 {
  2456  			base.WarnfAt(x.Pos(), "reshaping %L to %v", x, typ)
  2457  		}
  2458  
  2459  		x.SetType(typ)
  2460  		return x
  2461  
  2462  	case exprConvert:
  2463  		implicit := r.Bool()
  2464  		typ := r.typ()
  2465  		pos := r.pos()
  2466  		typeWord, srcRType := r.convRTTI(pos)
  2467  		dstTypeParam := r.Bool()
  2468  		identical := r.Bool()
  2469  		x := r.expr()
  2470  
  2471  		// TODO(mdempsky): Stop constructing expressions of untyped type.
  2472  		x = typecheck.DefaultLit(x, typ)
  2473  
  2474  		ce := ir.NewConvExpr(pos, ir.OCONV, typ, x)
  2475  		ce.TypeWord, ce.SrcRType = typeWord, srcRType
  2476  		if implicit {
  2477  			ce.SetImplicit(true)
  2478  		}
  2479  		n := typecheck.Expr(ce)
  2480  
  2481  		// Conversions between non-identical, non-empty interfaces always
  2482  		// requires a runtime call, even if they have identical underlying
  2483  		// interfaces. This is because we create separate itab instances
  2484  		// for each unique interface type, not merely each unique
  2485  		// interface shape.
  2486  		//
  2487  		// However, due to shape types, typecheck.Expr might mistakenly
  2488  		// think a conversion between two non-empty interfaces are
  2489  		// identical and set ir.OCONVNOP, instead of ir.OCONVIFACE. To
  2490  		// ensure we update the itab field appropriately, we force it to
  2491  		// ir.OCONVIFACE instead when shape types are involved.
  2492  		//
  2493  		// TODO(mdempsky): Are there other places we might get this wrong?
  2494  		// Should this be moved down into typecheck.{Assign,Convert}op?
  2495  		// This would be a non-issue if itabs were unique for each
  2496  		// *underlying* interface type instead.
  2497  		if !identical {
  2498  			if n, ok := n.(*ir.ConvExpr); ok && n.Op() == ir.OCONVNOP && n.Type().IsInterface() && !n.Type().IsEmptyInterface() && (n.Type().HasShape() || n.X.Type().HasShape()) {
  2499  				n.SetOp(ir.OCONVIFACE)
  2500  			}
  2501  		}
  2502  
  2503  		// spec: "If the type is a type parameter, the constant is converted
  2504  		// into a non-constant value of the type parameter."
  2505  		if dstTypeParam && ir.IsConstNode(n) {
  2506  			// Wrap in an OCONVNOP node to ensure result is non-constant.
  2507  			n = Implicit(ir.NewConvExpr(pos, ir.OCONVNOP, n.Type(), n))
  2508  			n.SetTypecheck(1)
  2509  		}
  2510  		return n
  2511  
  2512  	case exprRuntimeBuiltin:
  2513  		builtin := typecheck.LookupRuntime(r.String())
  2514  		return builtin
  2515  	}
  2516  }
  2517  
  2518  // funcInst reads an instantiated function reference, and returns
  2519  // three (possibly nil) expressions related to it:
  2520  //
  2521  // baseFn is always non-nil: it's either a function of the appropriate
  2522  // type already, or it has an extra dictionary parameter as the first
  2523  // parameter.
  2524  //
  2525  // If dictPtr is non-nil, then it's a dictionary argument that must be
  2526  // passed as the first argument to baseFn.
  2527  //
  2528  // If wrapperFn is non-nil, then it's either the same as baseFn (if
  2529  // dictPtr is nil), or it's semantically equivalent to currying baseFn
  2530  // to pass dictPtr. (wrapperFn is nil when dictPtr is an expression
  2531  // that needs to be computed dynamically.)
  2532  //
  2533  // For callers that are creating a call to the returned function, it's
  2534  // best to emit a call to baseFn, and include dictPtr in the arguments
  2535  // list as appropriate.
  2536  //
  2537  // For callers that want to return the function without invoking it,
  2538  // they may return wrapperFn if it's non-nil; but otherwise, they need
  2539  // to create their own wrapper.
  2540  func (r *reader) funcInst(pos src.XPos) (wrapperFn, baseFn, dictPtr ir.Node) {
  2541  	// Like in methodExpr, I'm pretty sure this isn't needed.
  2542  	var implicits []*types.Type
  2543  	if r.dict != nil {
  2544  		implicits = r.dict.targs
  2545  	}
  2546  
  2547  	if r.Bool() { // dynamic subdictionary
  2548  		idx := r.Len()
  2549  		info := r.dict.subdicts[idx]
  2550  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2551  
  2552  		baseFn = r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2553  
  2554  		// TODO(mdempsky): Is there a more robust way to get the
  2555  		// dictionary pointer type here?
  2556  		dictPtrType := baseFn.Type().Param(0).Type
  2557  		dictPtr = typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, dictPtrType, r.dictWord(pos, r.dict.subdictsOffset()+idx)))
  2558  
  2559  		return
  2560  	}
  2561  
  2562  	info := r.objInfo()
  2563  	explicits := r.p.typListIdx(info.explicits, r.dict)
  2564  
  2565  	wrapperFn = r.p.objIdx(info.idx, implicits, explicits, false).(*ir.Name)
  2566  	baseFn = r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2567  
  2568  	dictName := r.p.objDictName(info.idx, implicits, explicits)
  2569  	dictPtr = typecheck.Expr(ir.NewAddrExpr(pos, dictName))
  2570  
  2571  	return
  2572  }
  2573  
  2574  func (pr *pkgReader) objDictName(idx pkgbits.Index, implicits, explicits []*types.Type) *ir.Name {
  2575  	rname := pr.newReader(pkgbits.RelocName, idx, pkgbits.SyncObject1)
  2576  	_, sym := rname.qualifiedIdent()
  2577  	tag := pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
  2578  
  2579  	if tag == pkgbits.ObjStub {
  2580  		assert(!sym.IsBlank())
  2581  		if pri, ok := objReader[sym]; ok {
  2582  			return pri.pr.objDictName(pri.idx, nil, explicits)
  2583  		}
  2584  		base.Fatalf("unresolved stub: %v", sym)
  2585  	}
  2586  
  2587  	dict, err := pr.objDictIdx(sym, idx, implicits, explicits, false)
  2588  	if err != nil {
  2589  		base.Fatalf("%v", err)
  2590  	}
  2591  
  2592  	return pr.dictNameOf(dict)
  2593  }
  2594  
  2595  // curry returns a function literal that calls fun with arg0 and
  2596  // (optionally) arg1, accepting additional arguments to the function
  2597  // literal as necessary to satisfy fun's signature.
  2598  //
  2599  // If nilCheck is true and arg0 is an interface value, then it's
  2600  // checked to be non-nil as an initial step at the point of evaluating
  2601  // the function literal itself.
  2602  func (r *reader) curry(origPos src.XPos, ifaceHack bool, fun ir.Node, arg0, arg1 ir.Node) ir.Node {
  2603  	var captured ir.Nodes
  2604  	captured.Append(fun, arg0)
  2605  	if arg1 != nil {
  2606  		captured.Append(arg1)
  2607  	}
  2608  
  2609  	params, results := syntheticSig(fun.Type())
  2610  	params = params[len(captured)-1:] // skip curried parameters
  2611  	typ := types.NewSignature(nil, params, results)
  2612  
  2613  	addBody := func(pos src.XPos, r *reader, captured []ir.Node) {
  2614  		fun := captured[0]
  2615  
  2616  		var args ir.Nodes
  2617  		args.Append(captured[1:]...)
  2618  		args.Append(r.syntheticArgs()...)
  2619  
  2620  		r.syntheticTailCall(pos, fun, args)
  2621  	}
  2622  
  2623  	return r.syntheticClosure(origPos, typ, ifaceHack, captured, addBody)
  2624  }
  2625  
  2626  // methodExprWrap returns a function literal that changes method's
  2627  // first parameter's type to recv, and uses implicits/deref/addr to
  2628  // select the appropriate receiver parameter to pass to method.
  2629  func (r *reader) methodExprWrap(origPos src.XPos, recv *types.Type, implicits []int, deref, addr bool, method, dictPtr ir.Node) ir.Node {
  2630  	var captured ir.Nodes
  2631  	captured.Append(method)
  2632  
  2633  	params, results := syntheticSig(method.Type())
  2634  
  2635  	// Change first parameter to recv.
  2636  	params[0].Type = recv
  2637  
  2638  	// If we have a dictionary pointer argument to pass, then omit the
  2639  	// underlying method expression's dictionary parameter from the
  2640  	// returned signature too.
  2641  	if dictPtr != nil {
  2642  		captured.Append(dictPtr)
  2643  		params = append(params[:1], params[2:]...)
  2644  	}
  2645  
  2646  	typ := types.NewSignature(nil, params, results)
  2647  
  2648  	addBody := func(pos src.XPos, r *reader, captured []ir.Node) {
  2649  		fn := captured[0]
  2650  		args := r.syntheticArgs()
  2651  
  2652  		// Rewrite first argument based on implicits/deref/addr.
  2653  		{
  2654  			arg := args[0]
  2655  			for _, ix := range implicits {
  2656  				arg = Implicit(typecheck.DotField(pos, arg, ix))
  2657  			}
  2658  			if deref {
  2659  				arg = Implicit(Deref(pos, arg.Type().Elem(), arg))
  2660  			} else if addr {
  2661  				arg = Implicit(Addr(pos, arg))
  2662  			}
  2663  			args[0] = arg
  2664  		}
  2665  
  2666  		// Insert dictionary argument, if provided.
  2667  		if dictPtr != nil {
  2668  			newArgs := make([]ir.Node, len(args)+1)
  2669  			newArgs[0] = args[0]
  2670  			newArgs[1] = captured[1]
  2671  			copy(newArgs[2:], args[1:])
  2672  			args = newArgs
  2673  		}
  2674  
  2675  		r.syntheticTailCall(pos, fn, args)
  2676  	}
  2677  
  2678  	return r.syntheticClosure(origPos, typ, false, captured, addBody)
  2679  }
  2680  
  2681  // syntheticClosure constructs a synthetic function literal for
  2682  // currying dictionary arguments. origPos is the position used for the
  2683  // closure, which must be a non-inlined position. typ is the function
  2684  // literal's signature type.
  2685  //
  2686  // captures is a list of expressions that need to be evaluated at the
  2687  // point of function literal evaluation and captured by the function
  2688  // literal. If ifaceHack is true and captures[1] is an interface type,
  2689  // it's checked to be non-nil after evaluation.
  2690  //
  2691  // addBody is a callback function to populate the function body. The
  2692  // list of captured values passed back has the captured variables for
  2693  // use within the function literal, corresponding to the expressions
  2694  // in captures.
  2695  func (r *reader) syntheticClosure(origPos src.XPos, typ *types.Type, ifaceHack bool, captures ir.Nodes, addBody func(pos src.XPos, r *reader, captured []ir.Node)) ir.Node {
  2696  	// isSafe reports whether n is an expression that we can safely
  2697  	// defer to evaluating inside the closure instead, to avoid storing
  2698  	// them into the closure.
  2699  	//
  2700  	// In practice this is always (and only) the wrappee function.
  2701  	isSafe := func(n ir.Node) bool {
  2702  		if n.Op() == ir.ONAME && n.(*ir.Name).Class == ir.PFUNC {
  2703  			return true
  2704  		}
  2705  		if n.Op() == ir.OMETHEXPR {
  2706  			return true
  2707  		}
  2708  
  2709  		return false
  2710  	}
  2711  
  2712  	fn := r.inlClosureFunc(origPos, typ, ir.OCLOSURE)
  2713  	fn.SetWrapper(true)
  2714  
  2715  	clo := fn.OClosure
  2716  	inlPos := clo.Pos()
  2717  
  2718  	var init ir.Nodes
  2719  	for i, n := range captures {
  2720  		if isSafe(n) {
  2721  			continue // skip capture; can reference directly
  2722  		}
  2723  
  2724  		tmp := r.tempCopy(inlPos, n, &init)
  2725  		ir.NewClosureVar(origPos, fn, tmp)
  2726  
  2727  		// We need to nil check interface receivers at the point of method
  2728  		// value evaluation, ugh.
  2729  		if ifaceHack && i == 1 && n.Type().IsInterface() {
  2730  			check := ir.NewUnaryExpr(inlPos, ir.OCHECKNIL, ir.NewUnaryExpr(inlPos, ir.OITAB, tmp))
  2731  			init.Append(typecheck.Stmt(check))
  2732  		}
  2733  	}
  2734  
  2735  	pri := pkgReaderIndex{synthetic: func(pos src.XPos, r *reader) {
  2736  		captured := make([]ir.Node, len(captures))
  2737  		next := 0
  2738  		for i, n := range captures {
  2739  			if isSafe(n) {
  2740  				captured[i] = n
  2741  			} else {
  2742  				captured[i] = r.closureVars[next]
  2743  				next++
  2744  			}
  2745  		}
  2746  		assert(next == len(r.closureVars))
  2747  
  2748  		addBody(origPos, r, captured)
  2749  	}}
  2750  	bodyReader[fn] = pri
  2751  	pri.funcBody(fn)
  2752  
  2753  	return ir.InitExpr(init, clo)
  2754  }
  2755  
  2756  // syntheticSig duplicates and returns the params and results lists
  2757  // for sig, but renaming anonymous parameters so they can be assigned
  2758  // ir.Names.
  2759  func syntheticSig(sig *types.Type) (params, results []*types.Field) {
  2760  	clone := func(params []*types.Field) []*types.Field {
  2761  		res := make([]*types.Field, len(params))
  2762  		for i, param := range params {
  2763  			// TODO(mdempsky): It would be nice to preserve the original
  2764  			// parameter positions here instead, but at least
  2765  			// typecheck.NewMethodType replaces them with base.Pos, making
  2766  			// them useless. Worse, the positions copied from base.Pos may
  2767  			// have inlining contexts, which we definitely don't want here
  2768  			// (e.g., #54625).
  2769  			res[i] = types.NewField(base.AutogeneratedPos, param.Sym, param.Type)
  2770  			res[i].SetIsDDD(param.IsDDD())
  2771  		}
  2772  		return res
  2773  	}
  2774  
  2775  	return clone(sig.Params()), clone(sig.Results())
  2776  }
  2777  
  2778  func (r *reader) optExpr() ir.Node {
  2779  	if r.Bool() {
  2780  		return r.expr()
  2781  	}
  2782  	return nil
  2783  }
  2784  
  2785  // methodExpr reads a method expression reference, and returns three
  2786  // (possibly nil) expressions related to it:
  2787  //
  2788  // baseFn is always non-nil: it's either a function of the appropriate
  2789  // type already, or it has an extra dictionary parameter as the second
  2790  // parameter (i.e., immediately after the promoted receiver
  2791  // parameter).
  2792  //
  2793  // If dictPtr is non-nil, then it's a dictionary argument that must be
  2794  // passed as the second argument to baseFn.
  2795  //
  2796  // If wrapperFn is non-nil, then it's either the same as baseFn (if
  2797  // dictPtr is nil), or it's semantically equivalent to currying baseFn
  2798  // to pass dictPtr. (wrapperFn is nil when dictPtr is an expression
  2799  // that needs to be computed dynamically.)
  2800  //
  2801  // For callers that are creating a call to the returned method, it's
  2802  // best to emit a call to baseFn, and include dictPtr in the arguments
  2803  // list as appropriate.
  2804  //
  2805  // For callers that want to return a method expression without
  2806  // invoking it, they may return wrapperFn if it's non-nil; but
  2807  // otherwise, they need to create their own wrapper.
  2808  func (r *reader) methodExpr() (wrapperFn, baseFn, dictPtr ir.Node) {
  2809  	recv := r.typ()
  2810  	sig0 := r.typ()
  2811  	pos := r.pos()
  2812  	sym := r.selector()
  2813  
  2814  	// Signature type to return (i.e., recv prepended to the method's
  2815  	// normal parameters list).
  2816  	sig := typecheck.NewMethodType(sig0, recv)
  2817  
  2818  	if r.Bool() { // type parameter method expression
  2819  		idx := r.Len()
  2820  		word := r.dictWord(pos, r.dict.typeParamMethodExprsOffset()+idx)
  2821  
  2822  		// TODO(mdempsky): If the type parameter was instantiated with an
  2823  		// interface type (i.e., embed.IsInterface()), then we could
  2824  		// return the OMETHEXPR instead and save an indirection.
  2825  
  2826  		// We wrote the method expression's entry point PC into the
  2827  		// dictionary, but for Go `func` values we need to return a
  2828  		// closure (i.e., pointer to a structure with the PC as the first
  2829  		// field). Because method expressions don't have any closure
  2830  		// variables, we pun the dictionary entry as the closure struct.
  2831  		fn := typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, sig, ir.NewAddrExpr(pos, word)))
  2832  		return fn, fn, nil
  2833  	}
  2834  
  2835  	// TODO(mdempsky): I'm pretty sure this isn't needed: implicits is
  2836  	// only relevant to locally defined types, but they can't have
  2837  	// (non-promoted) methods.
  2838  	var implicits []*types.Type
  2839  	if r.dict != nil {
  2840  		implicits = r.dict.targs
  2841  	}
  2842  
  2843  	if r.Bool() { // dynamic subdictionary
  2844  		idx := r.Len()
  2845  		info := r.dict.subdicts[idx]
  2846  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2847  
  2848  		shapedObj := r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2849  		shapedFn := shapedMethodExpr(pos, shapedObj, sym)
  2850  
  2851  		// TODO(mdempsky): Is there a more robust way to get the
  2852  		// dictionary pointer type here?
  2853  		dictPtrType := shapedFn.Type().Param(1).Type
  2854  		dictPtr := typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, dictPtrType, r.dictWord(pos, r.dict.subdictsOffset()+idx)))
  2855  
  2856  		return nil, shapedFn, dictPtr
  2857  	}
  2858  
  2859  	if r.Bool() { // static dictionary
  2860  		info := r.objInfo()
  2861  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2862  
  2863  		shapedObj := r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2864  		shapedFn := shapedMethodExpr(pos, shapedObj, sym)
  2865  
  2866  		dict := r.p.objDictName(info.idx, implicits, explicits)
  2867  		dictPtr := typecheck.Expr(ir.NewAddrExpr(pos, dict))
  2868  
  2869  		// Check that dictPtr matches shapedFn's dictionary parameter.
  2870  		if !types.Identical(dictPtr.Type(), shapedFn.Type().Param(1).Type) {
  2871  			base.FatalfAt(pos, "dict %L, but shaped method %L", dict, shapedFn)
  2872  		}
  2873  
  2874  		// For statically known instantiations, we can take advantage of
  2875  		// the stenciled wrapper.
  2876  		base.AssertfAt(!recv.HasShape(), pos, "shaped receiver %v", recv)
  2877  		wrapperFn := typecheck.NewMethodExpr(pos, recv, sym)
  2878  		base.AssertfAt(types.Identical(sig, wrapperFn.Type()), pos, "wrapper %L does not have type %v", wrapperFn, sig)
  2879  
  2880  		return wrapperFn, shapedFn, dictPtr
  2881  	}
  2882  
  2883  	// Simple method expression; no dictionary needed.
  2884  	base.AssertfAt(!recv.HasShape() || recv.IsInterface(), pos, "shaped receiver %v", recv)
  2885  	fn := typecheck.NewMethodExpr(pos, recv, sym)
  2886  	return fn, fn, nil
  2887  }
  2888  
  2889  // shapedMethodExpr returns the specified method on the given shaped
  2890  // type.
  2891  func shapedMethodExpr(pos src.XPos, obj *ir.Name, sym *types.Sym) *ir.SelectorExpr {
  2892  	assert(obj.Op() == ir.OTYPE)
  2893  
  2894  	typ := obj.Type()
  2895  	assert(typ.HasShape())
  2896  
  2897  	method := func() *types.Field {
  2898  		for _, method := range typ.Methods() {
  2899  			if method.Sym == sym {
  2900  				return method
  2901  			}
  2902  		}
  2903  
  2904  		base.FatalfAt(pos, "failed to find method %v in shaped type %v", sym, typ)
  2905  		panic("unreachable")
  2906  	}()
  2907  
  2908  	// Construct an OMETHEXPR node.
  2909  	recv := method.Type.Recv().Type
  2910  	return typecheck.NewMethodExpr(pos, recv, sym)
  2911  }
  2912  
  2913  func (r *reader) multiExpr() []ir.Node {
  2914  	r.Sync(pkgbits.SyncMultiExpr)
  2915  
  2916  	if r.Bool() { // N:1
  2917  		pos := r.pos()
  2918  		expr := r.expr()
  2919  
  2920  		results := make([]ir.Node, r.Len())
  2921  		as := ir.NewAssignListStmt(pos, ir.OAS2, nil, []ir.Node{expr})
  2922  		as.Def = true
  2923  		for i := range results {
  2924  			tmp := r.temp(pos, r.typ())
  2925  			as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
  2926  			as.Lhs.Append(tmp)
  2927  
  2928  			res := ir.Node(tmp)
  2929  			if r.Bool() {
  2930  				n := ir.NewConvExpr(pos, ir.OCONV, r.typ(), res)
  2931  				n.TypeWord, n.SrcRType = r.convRTTI(pos)
  2932  				n.SetImplicit(true)
  2933  				res = typecheck.Expr(n)
  2934  			}
  2935  			results[i] = res
  2936  		}
  2937  
  2938  		// TODO(mdempsky): Could use ir.InlinedCallExpr instead?
  2939  		results[0] = ir.InitExpr([]ir.Node{typecheck.Stmt(as)}, results[0])
  2940  		return results
  2941  	}
  2942  
  2943  	// N:N
  2944  	exprs := make([]ir.Node, r.Len())
  2945  	if len(exprs) == 0 {
  2946  		return nil
  2947  	}
  2948  	for i := range exprs {
  2949  		exprs[i] = r.expr()
  2950  	}
  2951  	return exprs
  2952  }
  2953  
  2954  // temp returns a new autotemp of the specified type.
  2955  func (r *reader) temp(pos src.XPos, typ *types.Type) *ir.Name {
  2956  	return typecheck.TempAt(pos, r.curfn, typ)
  2957  }
  2958  
  2959  // tempCopy declares and returns a new autotemp initialized to the
  2960  // value of expr.
  2961  func (r *reader) tempCopy(pos src.XPos, expr ir.Node, init *ir.Nodes) *ir.Name {
  2962  	tmp := r.temp(pos, expr.Type())
  2963  
  2964  	init.Append(typecheck.Stmt(ir.NewDecl(pos, ir.ODCL, tmp)))
  2965  
  2966  	assign := ir.NewAssignStmt(pos, tmp, expr)
  2967  	assign.Def = true
  2968  	init.Append(typecheck.Stmt(ir.NewAssignStmt(pos, tmp, expr)))
  2969  
  2970  	tmp.Defn = assign
  2971  
  2972  	return tmp
  2973  }
  2974  
  2975  func (r *reader) compLit() ir.Node {
  2976  	r.Sync(pkgbits.SyncCompLit)
  2977  	pos := r.pos()
  2978  	typ0 := r.typ()
  2979  
  2980  	typ := typ0
  2981  	if typ.IsPtr() {
  2982  		typ = typ.Elem()
  2983  	}
  2984  	if typ.Kind() == types.TFORW {
  2985  		base.FatalfAt(pos, "unresolved composite literal type: %v", typ)
  2986  	}
  2987  	var rtype ir.Node
  2988  	if typ.IsMap() {
  2989  		rtype = r.rtype(pos)
  2990  	}
  2991  	isStruct := typ.Kind() == types.TSTRUCT
  2992  
  2993  	elems := make([]ir.Node, r.Len())
  2994  	for i := range elems {
  2995  		elemp := &elems[i]
  2996  
  2997  		if isStruct {
  2998  			sk := ir.NewStructKeyExpr(r.pos(), typ.Field(r.Len()), nil)
  2999  			*elemp, elemp = sk, &sk.Value
  3000  		} else if r.Bool() {
  3001  			kv := ir.NewKeyExpr(r.pos(), r.expr(), nil)
  3002  			*elemp, elemp = kv, &kv.Value
  3003  		}
  3004  
  3005  		*elemp = r.expr()
  3006  	}
  3007  
  3008  	lit := typecheck.Expr(ir.NewCompLitExpr(pos, ir.OCOMPLIT, typ, elems))
  3009  	if rtype != nil {
  3010  		lit := lit.(*ir.CompLitExpr)
  3011  		lit.RType = rtype
  3012  	}
  3013  	if typ0.IsPtr() {
  3014  		lit = typecheck.Expr(typecheck.NodAddrAt(pos, lit))
  3015  		lit.SetType(typ0)
  3016  	}
  3017  	return lit
  3018  }
  3019  
  3020  func (r *reader) funcLit() ir.Node {
  3021  	r.Sync(pkgbits.SyncFuncLit)
  3022  
  3023  	// The underlying function declaration (including its parameters'
  3024  	// positions, if any) need to remain the original, uninlined
  3025  	// positions. This is because we track inlining-context on nodes so
  3026  	// we can synthesize the extra implied stack frames dynamically when
  3027  	// generating tracebacks, whereas those stack frames don't make
  3028  	// sense *within* the function literal. (Any necessary inlining
  3029  	// adjustments will have been applied to the call expression
  3030  	// instead.)
  3031  	//
  3032  	// This is subtle, and getting it wrong leads to cycles in the
  3033  	// inlining tree, which lead to infinite loops during stack
  3034  	// unwinding (#46234, #54625).
  3035  	//
  3036  	// Note that we *do* want the inline-adjusted position for the
  3037  	// OCLOSURE node, because that position represents where any heap
  3038  	// allocation of the closure is credited (#49171).
  3039  	r.suppressInlPos++
  3040  	origPos := r.pos()
  3041  	sig := r.signature(nil)
  3042  	r.suppressInlPos--
  3043  	why := ir.OCLOSURE
  3044  	if r.Bool() {
  3045  		why = ir.ORANGE
  3046  	}
  3047  
  3048  	fn := r.inlClosureFunc(origPos, sig, why)
  3049  
  3050  	fn.ClosureVars = make([]*ir.Name, 0, r.Len())
  3051  	for len(fn.ClosureVars) < cap(fn.ClosureVars) {
  3052  		// TODO(mdempsky): I think these should be original positions too
  3053  		// (i.e., not inline-adjusted).
  3054  		ir.NewClosureVar(r.pos(), fn, r.useLocal())
  3055  	}
  3056  	if param := r.dictParam; param != nil {
  3057  		// If we have a dictionary parameter, capture it too. For
  3058  		// simplicity, we capture it last and unconditionally.
  3059  		ir.NewClosureVar(param.Pos(), fn, param)
  3060  	}
  3061  
  3062  	r.addBody(fn, nil)
  3063  
  3064  	// un-hide closures belong to init function.
  3065  	if (r.curfn.IsPackageInit() || strings.HasPrefix(r.curfn.Sym().Name, "init.")) && ir.IsTrivialClosure(fn.OClosure) {
  3066  		fn.SetIsHiddenClosure(false)
  3067  	}
  3068  
  3069  	return fn.OClosure
  3070  }
  3071  
  3072  // inlClosureFunc constructs a new closure function, but correctly
  3073  // handles inlining.
  3074  func (r *reader) inlClosureFunc(origPos src.XPos, sig *types.Type, why ir.Op) *ir.Func {
  3075  	curfn := r.inlCaller
  3076  	if curfn == nil {
  3077  		curfn = r.curfn
  3078  	}
  3079  
  3080  	// TODO(mdempsky): Remove hard-coding of typecheck.Target.
  3081  	return ir.NewClosureFunc(origPos, r.inlPos(origPos), why, sig, curfn, typecheck.Target)
  3082  }
  3083  
  3084  func (r *reader) exprList() []ir.Node {
  3085  	r.Sync(pkgbits.SyncExprList)
  3086  	return r.exprs()
  3087  }
  3088  
  3089  func (r *reader) exprs() []ir.Node {
  3090  	r.Sync(pkgbits.SyncExprs)
  3091  	nodes := make([]ir.Node, r.Len())
  3092  	if len(nodes) == 0 {
  3093  		return nil // TODO(mdempsky): Unclear if this matters.
  3094  	}
  3095  	for i := range nodes {
  3096  		nodes[i] = r.expr()
  3097  	}
  3098  	return nodes
  3099  }
  3100  
  3101  // dictWord returns an expression to return the specified
  3102  // uintptr-typed word from the dictionary parameter.
  3103  func (r *reader) dictWord(pos src.XPos, idx int) ir.Node {
  3104  	base.AssertfAt(r.dictParam != nil, pos, "expected dictParam in %v", r.curfn)
  3105  	return typecheck.Expr(ir.NewIndexExpr(pos, r.dictParam, ir.NewInt(pos, int64(idx))))
  3106  }
  3107  
  3108  // rttiWord is like dictWord, but converts it to *byte (the type used
  3109  // internally to represent *runtime._type and *runtime.itab).
  3110  func (r *reader) rttiWord(pos src.XPos, idx int) ir.Node {
  3111  	return typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, types.NewPtr(types.Types[types.TUINT8]), r.dictWord(pos, idx)))
  3112  }
  3113  
  3114  // rtype reads a type reference from the element bitstream, and
  3115  // returns an expression of type *runtime._type representing that
  3116  // type.
  3117  func (r *reader) rtype(pos src.XPos) ir.Node {
  3118  	_, rtype := r.rtype0(pos)
  3119  	return rtype
  3120  }
  3121  
  3122  func (r *reader) rtype0(pos src.XPos) (typ *types.Type, rtype ir.Node) {
  3123  	r.Sync(pkgbits.SyncRType)
  3124  	if r.Bool() { // derived type
  3125  		idx := r.Len()
  3126  		info := r.dict.rtypes[idx]
  3127  		typ = r.p.typIdx(info, r.dict, true)
  3128  		rtype = r.rttiWord(pos, r.dict.rtypesOffset()+idx)
  3129  		return
  3130  	}
  3131  
  3132  	typ = r.typ()
  3133  	rtype = reflectdata.TypePtrAt(pos, typ)
  3134  	return
  3135  }
  3136  
  3137  // varDictIndex populates name.DictIndex if name is a derived type.
  3138  func (r *reader) varDictIndex(name *ir.Name) {
  3139  	if r.Bool() {
  3140  		idx := 1 + r.dict.rtypesOffset() + r.Len()
  3141  		if int(uint16(idx)) != idx {
  3142  			base.FatalfAt(name.Pos(), "DictIndex overflow for %v: %v", name, idx)
  3143  		}
  3144  		name.DictIndex = uint16(idx)
  3145  	}
  3146  }
  3147  
  3148  // itab returns a (typ, iface) pair of types.
  3149  //
  3150  // typRType and ifaceRType are expressions that evaluate to the
  3151  // *runtime._type for typ and iface, respectively.
  3152  //
  3153  // If typ is a concrete type and iface is a non-empty interface type,
  3154  // then itab is an expression that evaluates to the *runtime.itab for
  3155  // the pair. Otherwise, itab is nil.
  3156  func (r *reader) itab(pos src.XPos) (typ *types.Type, typRType ir.Node, iface *types.Type, ifaceRType ir.Node, itab ir.Node) {
  3157  	typ, typRType = r.rtype0(pos)
  3158  	iface, ifaceRType = r.rtype0(pos)
  3159  
  3160  	idx := -1
  3161  	if r.Bool() {
  3162  		idx = r.Len()
  3163  	}
  3164  
  3165  	if !typ.IsInterface() && iface.IsInterface() && !iface.IsEmptyInterface() {
  3166  		if idx >= 0 {
  3167  			itab = r.rttiWord(pos, r.dict.itabsOffset()+idx)
  3168  		} else {
  3169  			base.AssertfAt(!typ.HasShape(), pos, "%v is a shape type", typ)
  3170  			base.AssertfAt(!iface.HasShape(), pos, "%v is a shape type", iface)
  3171  
  3172  			lsym := reflectdata.ITabLsym(typ, iface)
  3173  			itab = typecheck.LinksymAddr(pos, lsym, types.Types[types.TUINT8])
  3174  		}
  3175  	}
  3176  
  3177  	return
  3178  }
  3179  
  3180  // convRTTI returns expressions appropriate for populating an
  3181  // ir.ConvExpr's TypeWord and SrcRType fields, respectively.
  3182  func (r *reader) convRTTI(pos src.XPos) (typeWord, srcRType ir.Node) {
  3183  	r.Sync(pkgbits.SyncConvRTTI)
  3184  	src, srcRType0, dst, dstRType, itab := r.itab(pos)
  3185  	if !dst.IsInterface() {
  3186  		return
  3187  	}
  3188  
  3189  	// See reflectdata.ConvIfaceTypeWord.
  3190  	switch {
  3191  	case dst.IsEmptyInterface():
  3192  		if !src.IsInterface() {
  3193  			typeWord = srcRType0 // direct eface construction
  3194  		}
  3195  	case !src.IsInterface():
  3196  		typeWord = itab // direct iface construction
  3197  	default:
  3198  		typeWord = dstRType // convI2I
  3199  	}
  3200  
  3201  	// See reflectdata.ConvIfaceSrcRType.
  3202  	if !src.IsInterface() {
  3203  		srcRType = srcRType0
  3204  	}
  3205  
  3206  	return
  3207  }
  3208  
  3209  func (r *reader) exprType() ir.Node {
  3210  	r.Sync(pkgbits.SyncExprType)
  3211  	pos := r.pos()
  3212  
  3213  	var typ *types.Type
  3214  	var rtype, itab ir.Node
  3215  
  3216  	if r.Bool() {
  3217  		typ, rtype, _, _, itab = r.itab(pos)
  3218  		if !typ.IsInterface() {
  3219  			rtype = nil // TODO(mdempsky): Leave set?
  3220  		}
  3221  	} else {
  3222  		typ, rtype = r.rtype0(pos)
  3223  
  3224  		if !r.Bool() { // not derived
  3225  			return ir.TypeNode(typ)
  3226  		}
  3227  	}
  3228  
  3229  	dt := ir.NewDynamicType(pos, rtype)
  3230  	dt.ITab = itab
  3231  	return typed(typ, dt)
  3232  }
  3233  
  3234  func (r *reader) op() ir.Op {
  3235  	r.Sync(pkgbits.SyncOp)
  3236  	return ir.Op(r.Len())
  3237  }
  3238  
  3239  // @@@ Package initialization
  3240  
  3241  func (r *reader) pkgInit(self *types.Pkg, target *ir.Package) {
  3242  	cgoPragmas := make([][]string, r.Len())
  3243  	for i := range cgoPragmas {
  3244  		cgoPragmas[i] = r.Strings()
  3245  	}
  3246  	target.CgoPragmas = cgoPragmas
  3247  
  3248  	r.pkgInitOrder(target)
  3249  
  3250  	r.pkgDecls(target)
  3251  
  3252  	r.Sync(pkgbits.SyncEOF)
  3253  }
  3254  
  3255  // pkgInitOrder creates a synthetic init function to handle any
  3256  // package-scope initialization statements.
  3257  func (r *reader) pkgInitOrder(target *ir.Package) {
  3258  	initOrder := make([]ir.Node, r.Len())
  3259  	if len(initOrder) == 0 {
  3260  		return
  3261  	}
  3262  
  3263  	// Make a function that contains all the initialization statements.
  3264  	pos := base.AutogeneratedPos
  3265  	base.Pos = pos
  3266  
  3267  	fn := ir.NewFunc(pos, pos, typecheck.Lookup("init"), types.NewSignature(nil, nil, nil))
  3268  	fn.SetIsPackageInit(true)
  3269  	fn.SetInlinabilityChecked(true) // suppress useless "can inline" diagnostics
  3270  
  3271  	typecheck.DeclFunc(fn)
  3272  	r.curfn = fn
  3273  
  3274  	for i := range initOrder {
  3275  		lhs := make([]ir.Node, r.Len())
  3276  		for j := range lhs {
  3277  			lhs[j] = r.obj()
  3278  		}
  3279  		rhs := r.expr()
  3280  		pos := lhs[0].Pos()
  3281  
  3282  		var as ir.Node
  3283  		if len(lhs) == 1 {
  3284  			as = typecheck.Stmt(ir.NewAssignStmt(pos, lhs[0], rhs))
  3285  		} else {
  3286  			as = typecheck.Stmt(ir.NewAssignListStmt(pos, ir.OAS2, lhs, []ir.Node{rhs}))
  3287  		}
  3288  
  3289  		for _, v := range lhs {
  3290  			v.(*ir.Name).Defn = as
  3291  		}
  3292  
  3293  		initOrder[i] = as
  3294  	}
  3295  
  3296  	fn.Body = initOrder
  3297  
  3298  	typecheck.FinishFuncBody()
  3299  	r.curfn = nil
  3300  	r.locals = nil
  3301  
  3302  	// Outline (if legal/profitable) global map inits.
  3303  	staticinit.OutlineMapInits(fn)
  3304  
  3305  	target.Inits = append(target.Inits, fn)
  3306  }
  3307  
  3308  func (r *reader) pkgDecls(target *ir.Package) {
  3309  	r.Sync(pkgbits.SyncDecls)
  3310  	for {
  3311  		switch code := codeDecl(r.Code(pkgbits.SyncDecl)); code {
  3312  		default:
  3313  			panic(fmt.Sprintf("unhandled decl: %v", code))
  3314  
  3315  		case declEnd:
  3316  			return
  3317  
  3318  		case declFunc:
  3319  			names := r.pkgObjs(target)
  3320  			assert(len(names) == 1)
  3321  			target.Funcs = append(target.Funcs, names[0].Func)
  3322  
  3323  		case declMethod:
  3324  			typ := r.typ()
  3325  			sym := r.selector()
  3326  
  3327  			method := typecheck.Lookdot1(nil, sym, typ, typ.Methods(), 0)
  3328  			target.Funcs = append(target.Funcs, method.Nname.(*ir.Name).Func)
  3329  
  3330  		case declVar:
  3331  			names := r.pkgObjs(target)
  3332  
  3333  			if n := r.Len(); n > 0 {
  3334  				assert(len(names) == 1)
  3335  				embeds := make([]ir.Embed, n)
  3336  				for i := range embeds {
  3337  					embeds[i] = ir.Embed{Pos: r.pos(), Patterns: r.Strings()}
  3338  				}
  3339  				names[0].Embed = &embeds
  3340  				target.Embeds = append(target.Embeds, names[0])
  3341  			}
  3342  
  3343  		case declOther:
  3344  			r.pkgObjs(target)
  3345  		}
  3346  	}
  3347  }
  3348  
  3349  func (r *reader) pkgObjs(target *ir.Package) []*ir.Name {
  3350  	r.Sync(pkgbits.SyncDeclNames)
  3351  	nodes := make([]*ir.Name, r.Len())
  3352  	for i := range nodes {
  3353  		r.Sync(pkgbits.SyncDeclName)
  3354  
  3355  		name := r.obj().(*ir.Name)
  3356  		nodes[i] = name
  3357  
  3358  		sym := name.Sym()
  3359  		if sym.IsBlank() {
  3360  			continue
  3361  		}
  3362  
  3363  		switch name.Class {
  3364  		default:
  3365  			base.FatalfAt(name.Pos(), "unexpected class: %v", name.Class)
  3366  
  3367  		case ir.PEXTERN:
  3368  			target.Externs = append(target.Externs, name)
  3369  
  3370  		case ir.PFUNC:
  3371  			assert(name.Type().Recv() == nil)
  3372  
  3373  			// TODO(mdempsky): Cleaner way to recognize init?
  3374  			if strings.HasPrefix(sym.Name, "init.") {
  3375  				target.Inits = append(target.Inits, name.Func)
  3376  			}
  3377  		}
  3378  
  3379  		if base.Ctxt.Flag_dynlink && types.LocalPkg.Name == "main" && types.IsExported(sym.Name) && name.Op() == ir.ONAME {
  3380  			assert(!sym.OnExportList())
  3381  			target.PluginExports = append(target.PluginExports, name)
  3382  			sym.SetOnExportList(true)
  3383  		}
  3384  
  3385  		if base.Flag.AsmHdr != "" && (name.Op() == ir.OLITERAL || name.Op() == ir.OTYPE) {
  3386  			assert(!sym.Asm())
  3387  			target.AsmHdrDecls = append(target.AsmHdrDecls, name)
  3388  			sym.SetAsm(true)
  3389  		}
  3390  	}
  3391  
  3392  	return nodes
  3393  }
  3394  
  3395  // @@@ Inlining
  3396  
  3397  // unifiedHaveInlineBody reports whether we have the function body for
  3398  // fn, so we can inline it.
  3399  func unifiedHaveInlineBody(fn *ir.Func) bool {
  3400  	if fn.Inl == nil {
  3401  		return false
  3402  	}
  3403  
  3404  	_, ok := bodyReaderFor(fn)
  3405  	return ok
  3406  }
  3407  
  3408  var inlgen = 0
  3409  
  3410  // unifiedInlineCall implements inline.NewInline by re-reading the function
  3411  // body from its Unified IR export data.
  3412  func unifiedInlineCall(callerfn *ir.Func, call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExpr {
  3413  	pri, ok := bodyReaderFor(fn)
  3414  	if !ok {
  3415  		base.FatalfAt(call.Pos(), "cannot inline call to %v: missing inline body", fn)
  3416  	}
  3417  
  3418  	if !fn.Inl.HaveDcl {
  3419  		expandInline(fn, pri)
  3420  	}
  3421  
  3422  	r := pri.asReader(pkgbits.RelocBody, pkgbits.SyncFuncBody)
  3423  
  3424  	tmpfn := ir.NewFunc(fn.Pos(), fn.Nname.Pos(), callerfn.Sym(), fn.Type())
  3425  
  3426  	r.curfn = tmpfn
  3427  
  3428  	r.inlCaller = callerfn
  3429  	r.inlCall = call
  3430  	r.inlFunc = fn
  3431  	r.inlTreeIndex = inlIndex
  3432  	r.inlPosBases = make(map[*src.PosBase]*src.PosBase)
  3433  	r.funarghack = true
  3434  
  3435  	r.closureVars = make([]*ir.Name, len(r.inlFunc.ClosureVars))
  3436  	for i, cv := range r.inlFunc.ClosureVars {
  3437  		// TODO(mdempsky): It should be possible to support this case, but
  3438  		// for now we rely on the inliner avoiding it.
  3439  		if cv.Outer.Curfn != callerfn {
  3440  			base.FatalfAt(call.Pos(), "inlining closure call across frames")
  3441  		}
  3442  		r.closureVars[i] = cv.Outer
  3443  	}
  3444  	if len(r.closureVars) != 0 && r.hasTypeParams() {
  3445  		r.dictParam = r.closureVars[len(r.closureVars)-1] // dictParam is last; see reader.funcLit
  3446  	}
  3447  
  3448  	r.declareParams()
  3449  
  3450  	var inlvars, retvars []*ir.Name
  3451  	{
  3452  		sig := r.curfn.Type()
  3453  		endParams := sig.NumRecvs() + sig.NumParams()
  3454  		endResults := endParams + sig.NumResults()
  3455  
  3456  		inlvars = r.curfn.Dcl[:endParams]
  3457  		retvars = r.curfn.Dcl[endParams:endResults]
  3458  	}
  3459  
  3460  	r.delayResults = fn.Inl.CanDelayResults
  3461  
  3462  	r.retlabel = typecheck.AutoLabel(".i")
  3463  	inlgen++
  3464  
  3465  	init := ir.TakeInit(call)
  3466  
  3467  	// For normal function calls, the function callee expression
  3468  	// may contain side effects. Make sure to preserve these,
  3469  	// if necessary (#42703).
  3470  	if call.Op() == ir.OCALLFUNC {
  3471  		inline.CalleeEffects(&init, call.Fun)
  3472  	}
  3473  
  3474  	var args ir.Nodes
  3475  	if call.Op() == ir.OCALLMETH {
  3476  		base.FatalfAt(call.Pos(), "OCALLMETH missed by typecheck")
  3477  	}
  3478  	args.Append(call.Args...)
  3479  
  3480  	// Create assignment to declare and initialize inlvars.
  3481  	as2 := ir.NewAssignListStmt(call.Pos(), ir.OAS2, ir.ToNodes(inlvars), args)
  3482  	as2.Def = true
  3483  	var as2init ir.Nodes
  3484  	for _, name := range inlvars {
  3485  		if ir.IsBlank(name) {
  3486  			continue
  3487  		}
  3488  		// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3489  		as2init.Append(ir.NewDecl(call.Pos(), ir.ODCL, name))
  3490  		name.Defn = as2
  3491  	}
  3492  	as2.SetInit(as2init)
  3493  	init.Append(typecheck.Stmt(as2))
  3494  
  3495  	if !r.delayResults {
  3496  		// If not delaying retvars, declare and zero initialize the
  3497  		// result variables now.
  3498  		for _, name := range retvars {
  3499  			// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3500  			init.Append(ir.NewDecl(call.Pos(), ir.ODCL, name))
  3501  			ras := ir.NewAssignStmt(call.Pos(), name, nil)
  3502  			init.Append(typecheck.Stmt(ras))
  3503  		}
  3504  	}
  3505  
  3506  	// Add an inline mark just before the inlined body.
  3507  	// This mark is inline in the code so that it's a reasonable spot
  3508  	// to put a breakpoint. Not sure if that's really necessary or not
  3509  	// (in which case it could go at the end of the function instead).
  3510  	// Note issue 28603.
  3511  	init.Append(ir.NewInlineMarkStmt(call.Pos().WithIsStmt(), int64(r.inlTreeIndex)))
  3512  
  3513  	ir.WithFunc(r.curfn, func() {
  3514  		if !r.syntheticBody(call.Pos()) {
  3515  			assert(r.Bool()) // have body
  3516  
  3517  			r.curfn.Body = r.stmts()
  3518  			r.curfn.Endlineno = r.pos()
  3519  		}
  3520  
  3521  		// TODO(mdempsky): This shouldn't be necessary. Inlining might
  3522  		// read in new function/method declarations, which could
  3523  		// potentially be recursively inlined themselves; but we shouldn't
  3524  		// need to read in the non-inlined bodies for the declarations
  3525  		// themselves. But currently it's an easy fix to #50552.
  3526  		readBodies(typecheck.Target, true)
  3527  
  3528  		// Replace any "return" statements within the function body.
  3529  		var edit func(ir.Node) ir.Node
  3530  		edit = func(n ir.Node) ir.Node {
  3531  			if ret, ok := n.(*ir.ReturnStmt); ok {
  3532  				n = typecheck.Stmt(r.inlReturn(ret, retvars))
  3533  			}
  3534  			ir.EditChildren(n, edit)
  3535  			return n
  3536  		}
  3537  		edit(r.curfn)
  3538  	})
  3539  
  3540  	body := ir.Nodes(r.curfn.Body)
  3541  
  3542  	// Reparent any declarations into the caller function.
  3543  	for _, name := range r.curfn.Dcl {
  3544  		name.Curfn = callerfn
  3545  
  3546  		if name.Class != ir.PAUTO {
  3547  			name.SetPos(r.inlPos(name.Pos()))
  3548  			name.SetInlFormal(true)
  3549  			name.Class = ir.PAUTO
  3550  		} else {
  3551  			name.SetInlLocal(true)
  3552  		}
  3553  	}
  3554  	callerfn.Dcl = append(callerfn.Dcl, r.curfn.Dcl...)
  3555  
  3556  	body.Append(ir.NewLabelStmt(call.Pos(), r.retlabel))
  3557  
  3558  	res := ir.NewInlinedCallExpr(call.Pos(), body, ir.ToNodes(retvars))
  3559  	res.SetInit(init)
  3560  	res.SetType(call.Type())
  3561  	res.SetTypecheck(1)
  3562  
  3563  	// Inlining shouldn't add any functions to todoBodies.
  3564  	assert(len(todoBodies) == 0)
  3565  
  3566  	return res
  3567  }
  3568  
  3569  // inlReturn returns a statement that can substitute for the given
  3570  // return statement when inlining.
  3571  func (r *reader) inlReturn(ret *ir.ReturnStmt, retvars []*ir.Name) *ir.BlockStmt {
  3572  	pos := r.inlCall.Pos()
  3573  
  3574  	block := ir.TakeInit(ret)
  3575  
  3576  	if results := ret.Results; len(results) != 0 {
  3577  		assert(len(retvars) == len(results))
  3578  
  3579  		as2 := ir.NewAssignListStmt(pos, ir.OAS2, ir.ToNodes(retvars), ret.Results)
  3580  
  3581  		if r.delayResults {
  3582  			for _, name := range retvars {
  3583  				// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3584  				block.Append(ir.NewDecl(pos, ir.ODCL, name))
  3585  				name.Defn = as2
  3586  			}
  3587  		}
  3588  
  3589  		block.Append(as2)
  3590  	}
  3591  
  3592  	block.Append(ir.NewBranchStmt(pos, ir.OGOTO, r.retlabel))
  3593  	return ir.NewBlockStmt(pos, block)
  3594  }
  3595  
  3596  // expandInline reads in an extra copy of IR to populate
  3597  // fn.Inl.Dcl.
  3598  func expandInline(fn *ir.Func, pri pkgReaderIndex) {
  3599  	// TODO(mdempsky): Remove this function. It's currently needed by
  3600  	// dwarfgen/dwarf.go:preInliningDcls, which requires fn.Inl.Dcl to
  3601  	// create abstract function DIEs. But we should be able to provide it
  3602  	// with the same information some other way.
  3603  
  3604  	fndcls := len(fn.Dcl)
  3605  	topdcls := len(typecheck.Target.Funcs)
  3606  
  3607  	tmpfn := ir.NewFunc(fn.Pos(), fn.Nname.Pos(), fn.Sym(), fn.Type())
  3608  	tmpfn.ClosureVars = fn.ClosureVars
  3609  
  3610  	{
  3611  		r := pri.asReader(pkgbits.RelocBody, pkgbits.SyncFuncBody)
  3612  
  3613  		// Don't change parameter's Sym/Nname fields.
  3614  		r.funarghack = true
  3615  
  3616  		r.funcBody(tmpfn)
  3617  	}
  3618  
  3619  	// Move tmpfn's params to fn.Inl.Dcl, and reparent under fn.
  3620  	for _, name := range tmpfn.Dcl {
  3621  		name.Curfn = fn
  3622  	}
  3623  	fn.Inl.Dcl = tmpfn.Dcl
  3624  	fn.Inl.HaveDcl = true
  3625  
  3626  	// Double check that we didn't change fn.Dcl by accident.
  3627  	assert(fndcls == len(fn.Dcl))
  3628  
  3629  	// typecheck.Stmts may have added function literals to
  3630  	// typecheck.Target.Decls. Remove them again so we don't risk trying
  3631  	// to compile them multiple times.
  3632  	typecheck.Target.Funcs = typecheck.Target.Funcs[:topdcls]
  3633  }
  3634  
  3635  // usedLocals returns a set of local variables that are used within body.
  3636  func usedLocals(body []ir.Node) ir.NameSet {
  3637  	var used ir.NameSet
  3638  	ir.VisitList(body, func(n ir.Node) {
  3639  		if n, ok := n.(*ir.Name); ok && n.Op() == ir.ONAME && n.Class == ir.PAUTO {
  3640  			used.Add(n)
  3641  		}
  3642  	})
  3643  	return used
  3644  }
  3645  
  3646  // @@@ Method wrappers
  3647  //
  3648  // Here we handle constructing "method wrappers," alternative entry
  3649  // points that adapt methods to different calling conventions. Given a
  3650  // user-declared method "func (T) M(i int) bool { ... }", there are a
  3651  // few wrappers we may need to construct:
  3652  //
  3653  //	- Implicit dereferencing. Methods declared with a value receiver T
  3654  //	  are also included in the method set of the pointer type *T, so
  3655  //	  we need to construct a wrapper like "func (recv *T) M(i int)
  3656  //	  bool { return (*recv).M(i) }".
  3657  //
  3658  //	- Promoted methods. If struct type U contains an embedded field of
  3659  //	  type T or *T, we need to construct a wrapper like "func (recv U)
  3660  //	  M(i int) bool { return recv.T.M(i) }".
  3661  //
  3662  //	- Method values. If x is an expression of type T, then "x.M" is
  3663  //	  roughly "tmp := x; func(i int) bool { return tmp.M(i) }".
  3664  //
  3665  // At call sites, we always prefer to call the user-declared method
  3666  // directly, if known, so wrappers are only needed for indirect calls
  3667  // (for example, interface method calls that can't be devirtualized).
  3668  // Consequently, we can save some compile time by skipping
  3669  // construction of wrappers that are never needed.
  3670  //
  3671  // Alternatively, because the linker doesn't care which compilation
  3672  // unit constructed a particular wrapper, we can instead construct
  3673  // them as needed. However, if a wrapper is needed in multiple
  3674  // downstream packages, we may end up needing to compile it multiple
  3675  // times, costing us more compile time and object file size. (We mark
  3676  // the wrappers as DUPOK, so the linker doesn't complain about the
  3677  // duplicate symbols.)
  3678  //
  3679  // The current heuristics we use to balance these trade offs are:
  3680  //
  3681  //	- For a (non-parameterized) defined type T, we construct wrappers
  3682  //	  for *T and any promoted methods on T (and *T) in the same
  3683  //	  compilation unit as the type declaration.
  3684  //
  3685  //	- For a parameterized defined type, we construct wrappers in the
  3686  //	  compilation units in which the type is instantiated. We
  3687  //	  similarly handle wrappers for anonymous types with methods and
  3688  //	  compilation units where their type literals appear in source.
  3689  //
  3690  //	- Method value expressions are relatively uncommon, so we
  3691  //	  construct their wrappers in the compilation units that they
  3692  //	  appear in.
  3693  //
  3694  // Finally, as an opportunistic compile-time optimization, if we know
  3695  // a wrapper was constructed in any imported package's compilation
  3696  // unit, then we skip constructing a duplicate one. However, currently
  3697  // this is only done on a best-effort basis.
  3698  
  3699  // needWrapperTypes lists types for which we may need to generate
  3700  // method wrappers.
  3701  var needWrapperTypes []*types.Type
  3702  
  3703  // haveWrapperTypes lists types for which we know we already have
  3704  // method wrappers, because we found the type in an imported package.
  3705  var haveWrapperTypes []*types.Type
  3706  
  3707  // needMethodValueWrappers lists methods for which we may need to
  3708  // generate method value wrappers.
  3709  var needMethodValueWrappers []methodValueWrapper
  3710  
  3711  // haveMethodValueWrappers lists methods for which we know we already
  3712  // have method value wrappers, because we found it in an imported
  3713  // package.
  3714  var haveMethodValueWrappers []methodValueWrapper
  3715  
  3716  type methodValueWrapper struct {
  3717  	rcvr   *types.Type
  3718  	method *types.Field
  3719  }
  3720  
  3721  // needWrapper records that wrapper methods may be needed at link
  3722  // time.
  3723  func (r *reader) needWrapper(typ *types.Type) {
  3724  	if typ.IsPtr() {
  3725  		return
  3726  	}
  3727  
  3728  	// Special case: runtime must define error even if imported packages mention it (#29304).
  3729  	forceNeed := typ == types.ErrorType && base.Ctxt.Pkgpath == "runtime"
  3730  
  3731  	// If a type was found in an imported package, then we can assume
  3732  	// that package (or one of its transitive dependencies) already
  3733  	// generated method wrappers for it.
  3734  	if r.importedDef() && !forceNeed {
  3735  		haveWrapperTypes = append(haveWrapperTypes, typ)
  3736  	} else {
  3737  		needWrapperTypes = append(needWrapperTypes, typ)
  3738  	}
  3739  }
  3740  
  3741  // importedDef reports whether r is reading from an imported and
  3742  // non-generic element.
  3743  //
  3744  // If a type was found in an imported package, then we can assume that
  3745  // package (or one of its transitive dependencies) already generated
  3746  // method wrappers for it.
  3747  //
  3748  // Exception: If we're instantiating an imported generic type or
  3749  // function, we might be instantiating it with type arguments not
  3750  // previously seen before.
  3751  //
  3752  // TODO(mdempsky): Distinguish when a generic function or type was
  3753  // instantiated in an imported package so that we can add types to
  3754  // haveWrapperTypes instead.
  3755  func (r *reader) importedDef() bool {
  3756  	return r.p != localPkgReader && !r.hasTypeParams()
  3757  }
  3758  
  3759  // MakeWrappers constructs all wrapper methods needed for the target
  3760  // compilation unit.
  3761  func MakeWrappers(target *ir.Package) {
  3762  	// always generate a wrapper for error.Error (#29304)
  3763  	needWrapperTypes = append(needWrapperTypes, types.ErrorType)
  3764  
  3765  	seen := make(map[string]*types.Type)
  3766  
  3767  	for _, typ := range haveWrapperTypes {
  3768  		wrapType(typ, target, seen, false)
  3769  	}
  3770  	haveWrapperTypes = nil
  3771  
  3772  	for _, typ := range needWrapperTypes {
  3773  		wrapType(typ, target, seen, true)
  3774  	}
  3775  	needWrapperTypes = nil
  3776  
  3777  	for _, wrapper := range haveMethodValueWrappers {
  3778  		wrapMethodValue(wrapper.rcvr, wrapper.method, target, false)
  3779  	}
  3780  	haveMethodValueWrappers = nil
  3781  
  3782  	for _, wrapper := range needMethodValueWrappers {
  3783  		wrapMethodValue(wrapper.rcvr, wrapper.method, target, true)
  3784  	}
  3785  	needMethodValueWrappers = nil
  3786  }
  3787  
  3788  func wrapType(typ *types.Type, target *ir.Package, seen map[string]*types.Type, needed bool) {
  3789  	key := typ.LinkString()
  3790  	if prev := seen[key]; prev != nil {
  3791  		if !types.Identical(typ, prev) {
  3792  			base.Fatalf("collision: types %v and %v have link string %q", typ, prev, key)
  3793  		}
  3794  		return
  3795  	}
  3796  	seen[key] = typ
  3797  
  3798  	if !needed {
  3799  		// Only called to add to 'seen'.
  3800  		return
  3801  	}
  3802  
  3803  	if !typ.IsInterface() {
  3804  		typecheck.CalcMethods(typ)
  3805  	}
  3806  	for _, meth := range typ.AllMethods() {
  3807  		if meth.Sym.IsBlank() || !meth.IsMethod() {
  3808  			base.FatalfAt(meth.Pos, "invalid method: %v", meth)
  3809  		}
  3810  
  3811  		methodWrapper(0, typ, meth, target)
  3812  
  3813  		// For non-interface types, we also want *T wrappers.
  3814  		if !typ.IsInterface() {
  3815  			methodWrapper(1, typ, meth, target)
  3816  
  3817  			// For not-in-heap types, *T is a scalar, not pointer shaped,
  3818  			// so the interface wrappers use **T.
  3819  			if typ.NotInHeap() {
  3820  				methodWrapper(2, typ, meth, target)
  3821  			}
  3822  		}
  3823  	}
  3824  }
  3825  
  3826  func methodWrapper(derefs int, tbase *types.Type, method *types.Field, target *ir.Package) {
  3827  	wrapper := tbase
  3828  	for i := 0; i < derefs; i++ {
  3829  		wrapper = types.NewPtr(wrapper)
  3830  	}
  3831  
  3832  	sym := ir.MethodSym(wrapper, method.Sym)
  3833  	base.Assertf(!sym.Siggen(), "already generated wrapper %v", sym)
  3834  	sym.SetSiggen(true)
  3835  
  3836  	wrappee := method.Type.Recv().Type
  3837  	if types.Identical(wrapper, wrappee) ||
  3838  		!types.IsMethodApplicable(wrapper, method) ||
  3839  		!reflectdata.NeedEmit(tbase) {
  3840  		return
  3841  	}
  3842  
  3843  	// TODO(mdempsky): Use method.Pos instead?
  3844  	pos := base.AutogeneratedPos
  3845  
  3846  	fn := newWrapperFunc(pos, sym, wrapper, method)
  3847  
  3848  	var recv ir.Node = fn.Nname.Type().Recv().Nname.(*ir.Name)
  3849  
  3850  	// For simple *T wrappers around T methods, panicwrap produces a
  3851  	// nicer panic message.
  3852  	if wrapper.IsPtr() && types.Identical(wrapper.Elem(), wrappee) {
  3853  		cond := ir.NewBinaryExpr(pos, ir.OEQ, recv, types.BuiltinPkg.Lookup("nil").Def.(ir.Node))
  3854  		then := []ir.Node{ir.NewCallExpr(pos, ir.OCALL, typecheck.LookupRuntime("panicwrap"), nil)}
  3855  		fn.Body.Append(ir.NewIfStmt(pos, cond, then, nil))
  3856  	}
  3857  
  3858  	// typecheck will add one implicit deref, if necessary,
  3859  	// but not-in-heap types require more for their **T wrappers.
  3860  	for i := 1; i < derefs; i++ {
  3861  		recv = Implicit(ir.NewStarExpr(pos, recv))
  3862  	}
  3863  
  3864  	addTailCall(pos, fn, recv, method)
  3865  
  3866  	finishWrapperFunc(fn, target)
  3867  }
  3868  
  3869  func wrapMethodValue(recvType *types.Type, method *types.Field, target *ir.Package, needed bool) {
  3870  	sym := ir.MethodSymSuffix(recvType, method.Sym, "-fm")
  3871  	if sym.Uniq() {
  3872  		return
  3873  	}
  3874  	sym.SetUniq(true)
  3875  
  3876  	// TODO(mdempsky): Use method.Pos instead?
  3877  	pos := base.AutogeneratedPos
  3878  
  3879  	fn := newWrapperFunc(pos, sym, nil, method)
  3880  	sym.Def = fn.Nname
  3881  
  3882  	// Declare and initialize variable holding receiver.
  3883  	recv := ir.NewHiddenParam(pos, fn, typecheck.Lookup(".this"), recvType)
  3884  
  3885  	if !needed {
  3886  		return
  3887  	}
  3888  
  3889  	addTailCall(pos, fn, recv, method)
  3890  
  3891  	finishWrapperFunc(fn, target)
  3892  }
  3893  
  3894  func newWrapperFunc(pos src.XPos, sym *types.Sym, wrapper *types.Type, method *types.Field) *ir.Func {
  3895  	sig := newWrapperType(wrapper, method)
  3896  	fn := ir.NewFunc(pos, pos, sym, sig)
  3897  	fn.DeclareParams(true)
  3898  	fn.SetDupok(true) // TODO(mdempsky): Leave unset for local, non-generic wrappers?
  3899  
  3900  	return fn
  3901  }
  3902  
  3903  func finishWrapperFunc(fn *ir.Func, target *ir.Package) {
  3904  	ir.WithFunc(fn, func() {
  3905  		typecheck.Stmts(fn.Body)
  3906  	})
  3907  
  3908  	// We generate wrappers after the global inlining pass,
  3909  	// so we're responsible for applying inlining ourselves here.
  3910  	// TODO(prattmic): plumb PGO.
  3911  	interleaved.DevirtualizeAndInlineFunc(fn, nil)
  3912  
  3913  	// The body of wrapper function after inlining may reveal new ir.OMETHVALUE node,
  3914  	// we don't know whether wrapper function has been generated for it or not, so
  3915  	// generate one immediately here.
  3916  	//
  3917  	// Further, after CL 492017, function that construct closures is allowed to be inlined,
  3918  	// even though the closure itself can't be inline. So we also need to visit body of any
  3919  	// closure that we see when visiting body of the wrapper function.
  3920  	ir.VisitFuncAndClosures(fn, func(n ir.Node) {
  3921  		if n, ok := n.(*ir.SelectorExpr); ok && n.Op() == ir.OMETHVALUE {
  3922  			wrapMethodValue(n.X.Type(), n.Selection, target, true)
  3923  		}
  3924  	})
  3925  
  3926  	fn.Nname.Defn = fn
  3927  	target.Funcs = append(target.Funcs, fn)
  3928  }
  3929  
  3930  // newWrapperType returns a copy of the given signature type, but with
  3931  // the receiver parameter type substituted with recvType.
  3932  // If recvType is nil, newWrapperType returns a signature
  3933  // without a receiver parameter.
  3934  func newWrapperType(recvType *types.Type, method *types.Field) *types.Type {
  3935  	clone := func(params []*types.Field) []*types.Field {
  3936  		res := make([]*types.Field, len(params))
  3937  		for i, param := range params {
  3938  			res[i] = types.NewField(param.Pos, param.Sym, param.Type)
  3939  			res[i].SetIsDDD(param.IsDDD())
  3940  		}
  3941  		return res
  3942  	}
  3943  
  3944  	sig := method.Type
  3945  
  3946  	var recv *types.Field
  3947  	if recvType != nil {
  3948  		recv = types.NewField(sig.Recv().Pos, sig.Recv().Sym, recvType)
  3949  	}
  3950  	params := clone(sig.Params())
  3951  	results := clone(sig.Results())
  3952  
  3953  	return types.NewSignature(recv, params, results)
  3954  }
  3955  
  3956  func addTailCall(pos src.XPos, fn *ir.Func, recv ir.Node, method *types.Field) {
  3957  	sig := fn.Nname.Type()
  3958  	args := make([]ir.Node, sig.NumParams())
  3959  	for i, param := range sig.Params() {
  3960  		args[i] = param.Nname.(*ir.Name)
  3961  	}
  3962  
  3963  	// TODO(mdempsky): Support creating OTAILCALL, when possible. See reflectdata.methodWrapper.
  3964  	// Not urgent though, because tail calls are currently incompatible with regabi anyway.
  3965  
  3966  	fn.SetWrapper(true) // TODO(mdempsky): Leave unset for tail calls?
  3967  
  3968  	dot := typecheck.XDotMethod(pos, recv, method.Sym, true)
  3969  	call := typecheck.Call(pos, dot, args, method.Type.IsVariadic()).(*ir.CallExpr)
  3970  
  3971  	if method.Type.NumResults() == 0 {
  3972  		fn.Body.Append(call)
  3973  		return
  3974  	}
  3975  
  3976  	ret := ir.NewReturnStmt(pos, nil)
  3977  	ret.Results = []ir.Node{call}
  3978  	fn.Body.Append(ret)
  3979  }
  3980  
  3981  func setBasePos(pos src.XPos) {
  3982  	// Set the position for any error messages we might print (e.g. too large types).
  3983  	base.Pos = pos
  3984  }
  3985  
  3986  // dictParamName is the name of the synthetic dictionary parameter
  3987  // added to shaped functions.
  3988  //
  3989  // N.B., this variable name is known to Delve:
  3990  // https://github.com/go-delve/delve/blob/cb91509630529e6055be845688fd21eb89ae8714/pkg/proc/eval.go#L28
  3991  const dictParamName = typecheck.LocalDictName
  3992  
  3993  // shapeSig returns a copy of fn's signature, except adding a
  3994  // dictionary parameter and promoting the receiver parameter (if any)
  3995  // to a normal parameter.
  3996  //
  3997  // The parameter types.Fields are all copied too, so their Nname
  3998  // fields can be initialized for use by the shape function.
  3999  func shapeSig(fn *ir.Func, dict *readerDict) *types.Type {
  4000  	sig := fn.Nname.Type()
  4001  	oldRecv := sig.Recv()
  4002  
  4003  	var recv *types.Field
  4004  	if oldRecv != nil {
  4005  		recv = types.NewField(oldRecv.Pos, oldRecv.Sym, oldRecv.Type)
  4006  	}
  4007  
  4008  	params := make([]*types.Field, 1+sig.NumParams())
  4009  	params[0] = types.NewField(fn.Pos(), fn.Sym().Pkg.Lookup(dictParamName), types.NewPtr(dict.varType()))
  4010  	for i, param := range sig.Params() {
  4011  		d := types.NewField(param.Pos, param.Sym, param.Type)
  4012  		d.SetIsDDD(param.IsDDD())
  4013  		params[1+i] = d
  4014  	}
  4015  
  4016  	results := make([]*types.Field, sig.NumResults())
  4017  	for i, result := range sig.Results() {
  4018  		results[i] = types.NewField(result.Pos, result.Sym, result.Type)
  4019  	}
  4020  
  4021  	return types.NewSignature(recv, params, results)
  4022  }
  4023  

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