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/hash"
    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 []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.SectionPosBase)),
    59  		pkgs:     make([]*types.Pkg, pr.NumElems(pkgbits.SectionPkg)),
    60  		typs:     make([]*types.Type, pr.NumElems(pkgbits.SectionType)),
    61  
    62  		newindex: make([]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       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.SectionKind, 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.SectionKind, idx 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.SectionPosBase)))
   259  }
   260  
   261  // posBaseIdx returns the specified position base, reading it first if
   262  // needed.
   263  func (pr *pkgReader) posBaseIdx(idx index) *src.PosBase {
   264  	if b := pr.posBases[idx]; b != nil {
   265  		return b
   266  	}
   267  
   268  	r := pr.newReader(pkgbits.SectionPosBase, 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.SectionPkg))
   340  }
   341  
   342  // pkgIdx returns the specified package from the export data, reading
   343  // it first if needed.
   344  func (pr *pkgReader) pkgIdx(idx index) *types.Pkg {
   345  	if pkg := pr.pkgs[idx]; pkg != nil {
   346  		return pkg
   347  	}
   348  
   349  	pkg := pr.newReader(pkgbits.SectionPkg, 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: index(r.Len()), derived: true}
   395  	}
   396  	return typeInfo{idx: r.Reloc(pkgbits.SectionType), 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.SectionType, 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  	if r.Version().Has(pkgbits.DerivedFuncInstance) {
   644  		assert(!r.Bool())
   645  	}
   646  	idx := r.Reloc(pkgbits.SectionObj)
   647  
   648  	explicits := make([]typeInfo, r.Len())
   649  	for i := range explicits {
   650  		explicits[i] = r.typInfo()
   651  	}
   652  
   653  	return objInfo{idx, explicits}
   654  }
   655  
   656  // objInstIdx returns the encoded, instantiated object. If shaped is
   657  // true, then the shaped variant of the object is returned instead.
   658  func (pr *pkgReader) objInstIdx(info objInfo, dict *readerDict, shaped bool) ir.Node {
   659  	explicits := pr.typListIdx(info.explicits, dict)
   660  
   661  	var implicits []*types.Type
   662  	if dict != nil {
   663  		implicits = dict.targs
   664  	}
   665  
   666  	return pr.objIdx(info.idx, implicits, explicits, shaped)
   667  }
   668  
   669  // objIdx returns the specified object, instantiated with the given
   670  // type arguments, if any.
   671  // If shaped is true, then the shaped variant of the object is returned
   672  // instead.
   673  func (pr *pkgReader) objIdx(idx index, implicits, explicits []*types.Type, shaped bool) ir.Node {
   674  	n, err := pr.objIdxMayFail(idx, implicits, explicits, shaped)
   675  	if err != nil {
   676  		base.Fatalf("%v", err)
   677  	}
   678  	return n
   679  }
   680  
   681  // objIdxMayFail is equivalent to objIdx, but returns an error rather than
   682  // failing the build if this object requires type arguments and the incorrect
   683  // number of type arguments were passed.
   684  //
   685  // Other sources of internal failure (such as duplicate definitions) still fail
   686  // the build.
   687  func (pr *pkgReader) objIdxMayFail(idx index, implicits, explicits []*types.Type, shaped bool) (ir.Node, error) {
   688  	rname := pr.newReader(pkgbits.SectionName, idx, pkgbits.SyncObject1)
   689  	_, sym := rname.qualifiedIdent()
   690  	tag := pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
   691  
   692  	if tag == pkgbits.ObjStub {
   693  		assert(!sym.IsBlank())
   694  		switch sym.Pkg {
   695  		case types.BuiltinPkg, types.UnsafePkg:
   696  			return sym.Def.(ir.Node), nil
   697  		}
   698  		if pri, ok := objReader[sym]; ok {
   699  			return pri.pr.objIdxMayFail(pri.idx, nil, explicits, shaped)
   700  		}
   701  		if sym.Pkg.Path == "runtime" {
   702  			return typecheck.LookupRuntime(sym.Name), nil
   703  		}
   704  		base.Fatalf("unresolved stub: %v", sym)
   705  	}
   706  
   707  	dict, err := pr.objDictIdx(sym, idx, implicits, explicits, shaped)
   708  	if err != nil {
   709  		return nil, err
   710  	}
   711  
   712  	sym = dict.baseSym
   713  	if !sym.IsBlank() && sym.Def != nil {
   714  		return sym.Def.(*ir.Name), nil
   715  	}
   716  
   717  	r := pr.newReader(pkgbits.SectionObj, idx, pkgbits.SyncObject1)
   718  	rext := pr.newReader(pkgbits.SectionObjExt, idx, pkgbits.SyncObject1)
   719  
   720  	r.dict = dict
   721  	rext.dict = dict
   722  
   723  	do := func(op ir.Op, hasTParams bool) *ir.Name {
   724  		pos := r.pos()
   725  		setBasePos(pos)
   726  		if hasTParams {
   727  			r.typeParamNames()
   728  		}
   729  
   730  		name := ir.NewDeclNameAt(pos, op, sym)
   731  		name.Class = ir.PEXTERN // may be overridden later
   732  		if !sym.IsBlank() {
   733  			if sym.Def != nil {
   734  				base.FatalfAt(name.Pos(), "already have a definition for %v", name)
   735  			}
   736  			assert(sym.Def == nil)
   737  			sym.Def = name
   738  		}
   739  		return name
   740  	}
   741  
   742  	switch tag {
   743  	default:
   744  		panic("unexpected object")
   745  
   746  	case pkgbits.ObjAlias:
   747  		name := do(ir.OTYPE, false)
   748  
   749  		if r.Version().Has(pkgbits.AliasTypeParamNames) {
   750  			r.typeParamNames()
   751  		}
   752  
   753  		// Clumsy dance: the r.typ() call here might recursively find this
   754  		// type alias name, before we've set its type (#66873). So we
   755  		// temporarily clear sym.Def and then restore it later, if still
   756  		// unset.
   757  		hack := sym.Def == name
   758  		if hack {
   759  			sym.Def = nil
   760  		}
   761  		typ := r.typ()
   762  		if hack {
   763  			if sym.Def != nil {
   764  				name = sym.Def.(*ir.Name)
   765  				assert(types.IdenticalStrict(name.Type(), typ))
   766  				return name, nil
   767  			}
   768  			sym.Def = name
   769  		}
   770  
   771  		setType(name, typ)
   772  		name.SetAlias(true)
   773  		return name, nil
   774  
   775  	case pkgbits.ObjConst:
   776  		name := do(ir.OLITERAL, false)
   777  		typ := r.typ()
   778  		val := FixValue(typ, r.Value())
   779  		setType(name, typ)
   780  		setValue(name, val)
   781  		return name, nil
   782  
   783  	case pkgbits.ObjFunc:
   784  		if sym.Name == "init" {
   785  			sym = Renameinit()
   786  		}
   787  
   788  		npos := r.pos()
   789  		setBasePos(npos)
   790  		r.typeParamNames()
   791  		typ := r.signature(nil)
   792  		fpos := r.pos()
   793  
   794  		fn := ir.NewFunc(fpos, npos, sym, typ)
   795  		name := fn.Nname
   796  		if !sym.IsBlank() {
   797  			if sym.Def != nil {
   798  				base.FatalfAt(name.Pos(), "already have a definition for %v", name)
   799  			}
   800  			assert(sym.Def == nil)
   801  			sym.Def = name
   802  		}
   803  
   804  		if r.hasTypeParams() {
   805  			name.Func.SetDupok(true)
   806  			if r.dict.shaped {
   807  				setType(name, shapeSig(name.Func, r.dict))
   808  			} else {
   809  				todoDicts = append(todoDicts, func() {
   810  					r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
   811  				})
   812  			}
   813  		}
   814  
   815  		rext.funcExt(name, nil)
   816  		return name, nil
   817  
   818  	case pkgbits.ObjType:
   819  		name := do(ir.OTYPE, true)
   820  		typ := types.NewNamed(name)
   821  		setType(name, typ)
   822  		if r.hasTypeParams() && r.dict.shaped {
   823  			typ.SetHasShape(true)
   824  		}
   825  
   826  		// Important: We need to do this before SetUnderlying.
   827  		rext.typeExt(name)
   828  
   829  		// We need to defer CheckSize until we've called SetUnderlying to
   830  		// handle recursive types.
   831  		types.DeferCheckSize()
   832  		typ.SetUnderlying(r.typWrapped(false))
   833  		types.ResumeCheckSize()
   834  
   835  		if r.hasTypeParams() && !r.dict.shaped {
   836  			todoDicts = append(todoDicts, func() {
   837  				r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
   838  			})
   839  		}
   840  
   841  		methods := make([]*types.Field, r.Len())
   842  		for i := range methods {
   843  			methods[i] = r.method(rext)
   844  		}
   845  		if len(methods) != 0 {
   846  			typ.SetMethods(methods)
   847  		}
   848  
   849  		if !r.dict.shaped {
   850  			r.needWrapper(typ)
   851  		}
   852  
   853  		return name, nil
   854  
   855  	case pkgbits.ObjVar:
   856  		name := do(ir.ONAME, false)
   857  		setType(name, r.typ())
   858  		rext.varExt(name)
   859  		return name, nil
   860  	}
   861  }
   862  
   863  func (dict *readerDict) mangle(sym *types.Sym) *types.Sym {
   864  	if !dict.hasTypeParams() {
   865  		return sym
   866  	}
   867  
   868  	// If sym is a locally defined generic type, we need the suffix to
   869  	// stay at the end after mangling so that types/fmt.go can strip it
   870  	// out again when writing the type's runtime descriptor (#54456).
   871  	base, suffix := types.SplitVargenSuffix(sym.Name)
   872  
   873  	var buf strings.Builder
   874  	buf.WriteString(base)
   875  	buf.WriteByte('[')
   876  	for i, targ := range dict.targs {
   877  		if i > 0 {
   878  			if i == dict.implicits {
   879  				buf.WriteByte(';')
   880  			} else {
   881  				buf.WriteByte(',')
   882  			}
   883  		}
   884  		buf.WriteString(targ.LinkString())
   885  	}
   886  	buf.WriteByte(']')
   887  	buf.WriteString(suffix)
   888  	return sym.Pkg.Lookup(buf.String())
   889  }
   890  
   891  // shapify returns the shape type for targ.
   892  //
   893  // If basic is true, then the type argument is used to instantiate a
   894  // type parameter whose constraint is a basic interface.
   895  func shapify(targ *types.Type, basic bool) *types.Type {
   896  	if targ.Kind() == types.TFORW {
   897  		if targ.IsFullyInstantiated() {
   898  			// For recursive instantiated type argument, it may  still be a TFORW
   899  			// when shapifying happens. If we don't have targ's underlying type,
   900  			// shapify won't work. The worst case is we end up not reusing code
   901  			// optimally in some tricky cases.
   902  			if base.Debug.Shapify != 0 {
   903  				base.Warn("skipping shaping of recursive type %v", targ)
   904  			}
   905  			if targ.HasShape() {
   906  				return targ
   907  			}
   908  		} else {
   909  			base.Fatalf("%v is missing its underlying type", targ)
   910  		}
   911  	}
   912  	// For fully instantiated shape interface type, use it as-is. Otherwise, the instantiation
   913  	// involved recursive generic interface may cause mismatching in function signature, see issue #65362.
   914  	if targ.Kind() == types.TINTER && targ.IsFullyInstantiated() && targ.HasShape() {
   915  		return targ
   916  	}
   917  
   918  	// When a pointer type is used to instantiate a type parameter
   919  	// constrained by a basic interface, we know the pointer's element
   920  	// type can't matter to the generated code. In this case, we can use
   921  	// an arbitrary pointer type as the shape type. (To match the
   922  	// non-unified frontend, we use `*byte`.)
   923  	//
   924  	// Otherwise, we simply use the type's underlying type as its shape.
   925  	//
   926  	// TODO(mdempsky): It should be possible to do much more aggressive
   927  	// shaping still; e.g., collapsing all pointer-shaped types into a
   928  	// common type, collapsing scalars of the same size/alignment into a
   929  	// common type, recursively shaping the element types of composite
   930  	// types, and discarding struct field names and tags. However, we'll
   931  	// need to start tracking how type parameters are actually used to
   932  	// implement some of these optimizations.
   933  	pointerShaping := basic && targ.IsPtr() && !targ.Elem().NotInHeap()
   934  	// The exception is when the type parameter is a pointer to a type
   935  	// which `Type.HasShape()` returns true, but `Type.IsShape()` returns
   936  	// false, like `*[]go.shape.T`. This is because the type parameter is
   937  	// used to instantiate a generic function inside another generic function.
   938  	// In this case, we want to keep the targ as-is, otherwise, we may lose the
   939  	// original type after `*[]go.shape.T` is shapified to `*go.shape.uint8`.
   940  	// See issue #54535, #71184.
   941  	if pointerShaping && !targ.Elem().IsShape() && targ.Elem().HasShape() {
   942  		return targ
   943  	}
   944  	under := targ.Underlying()
   945  	if pointerShaping {
   946  		under = types.NewPtr(types.Types[types.TUINT8])
   947  	}
   948  
   949  	// Hash long type names to bound symbol name length seen by users,
   950  	// particularly for large protobuf structs (#65030).
   951  	uls := under.LinkString()
   952  	if base.Debug.MaxShapeLen != 0 &&
   953  		len(uls) > base.Debug.MaxShapeLen {
   954  		h := hash.Sum32([]byte(uls))
   955  		uls = hex.EncodeToString(h[:])
   956  	}
   957  
   958  	sym := types.ShapePkg.Lookup(uls)
   959  	if sym.Def == nil {
   960  		name := ir.NewDeclNameAt(under.Pos(), ir.OTYPE, sym)
   961  		typ := types.NewNamed(name)
   962  		typ.SetUnderlying(under)
   963  		sym.Def = typed(typ, name)
   964  	}
   965  	res := sym.Def.Type()
   966  	assert(res.IsShape())
   967  	assert(res.HasShape())
   968  	return res
   969  }
   970  
   971  // objDictIdx reads and returns the specified object dictionary.
   972  func (pr *pkgReader) objDictIdx(sym *types.Sym, idx index, implicits, explicits []*types.Type, shaped bool) (*readerDict, error) {
   973  	r := pr.newReader(pkgbits.SectionObjDict, idx, pkgbits.SyncObject1)
   974  
   975  	dict := readerDict{
   976  		shaped: shaped,
   977  	}
   978  
   979  	nimplicits := r.Len()
   980  	nexplicits := r.Len()
   981  
   982  	if nimplicits > len(implicits) || nexplicits != len(explicits) {
   983  		return nil, fmt.Errorf("%v has %v+%v params, but instantiated with %v+%v args", sym, nimplicits, nexplicits, len(implicits), len(explicits))
   984  	}
   985  
   986  	dict.targs = append(implicits[:nimplicits:nimplicits], explicits...)
   987  	dict.implicits = nimplicits
   988  
   989  	// Within the compiler, we can just skip over the type parameters.
   990  	for range dict.targs[dict.implicits:] {
   991  		// Skip past bounds without actually evaluating them.
   992  		r.typInfo()
   993  	}
   994  
   995  	dict.derived = make([]derivedInfo, r.Len())
   996  	dict.derivedTypes = make([]*types.Type, len(dict.derived))
   997  	for i := range dict.derived {
   998  		dict.derived[i] = derivedInfo{idx: r.Reloc(pkgbits.SectionType)}
   999  		if r.Version().Has(pkgbits.DerivedInfoNeeded) {
  1000  			assert(!r.Bool())
  1001  		}
  1002  	}
  1003  
  1004  	// Runtime dictionary information; private to the compiler.
  1005  
  1006  	// If any type argument is already shaped, then we're constructing a
  1007  	// shaped object, even if not explicitly requested (i.e., calling
  1008  	// objIdx with shaped==true). This can happen with instantiating
  1009  	// types that are referenced within a function body.
  1010  	for _, targ := range dict.targs {
  1011  		if targ.HasShape() {
  1012  			dict.shaped = true
  1013  			break
  1014  		}
  1015  	}
  1016  
  1017  	// And if we're constructing a shaped object, then shapify all type
  1018  	// arguments.
  1019  	for i, targ := range dict.targs {
  1020  		basic := r.Bool()
  1021  		if dict.shaped {
  1022  			dict.targs[i] = shapify(targ, basic)
  1023  		}
  1024  	}
  1025  
  1026  	dict.baseSym = dict.mangle(sym)
  1027  
  1028  	dict.typeParamMethodExprs = make([]readerMethodExprInfo, r.Len())
  1029  	for i := range dict.typeParamMethodExprs {
  1030  		typeParamIdx := r.Len()
  1031  		method := r.selector()
  1032  
  1033  		dict.typeParamMethodExprs[i] = readerMethodExprInfo{typeParamIdx, method}
  1034  	}
  1035  
  1036  	dict.subdicts = make([]objInfo, r.Len())
  1037  	for i := range dict.subdicts {
  1038  		dict.subdicts[i] = r.objInfo()
  1039  	}
  1040  
  1041  	dict.rtypes = make([]typeInfo, r.Len())
  1042  	for i := range dict.rtypes {
  1043  		dict.rtypes[i] = r.typInfo()
  1044  	}
  1045  
  1046  	dict.itabs = make([]itabInfo, r.Len())
  1047  	for i := range dict.itabs {
  1048  		dict.itabs[i] = itabInfo{typ: r.typInfo(), iface: r.typInfo()}
  1049  	}
  1050  
  1051  	return &dict, nil
  1052  }
  1053  
  1054  func (r *reader) typeParamNames() {
  1055  	r.Sync(pkgbits.SyncTypeParamNames)
  1056  
  1057  	for range r.dict.targs[r.dict.implicits:] {
  1058  		r.pos()
  1059  		r.localIdent()
  1060  	}
  1061  }
  1062  
  1063  func (r *reader) method(rext *reader) *types.Field {
  1064  	r.Sync(pkgbits.SyncMethod)
  1065  	npos := r.pos()
  1066  	sym := r.selector()
  1067  	r.typeParamNames()
  1068  	recv := r.param()
  1069  	typ := r.signature(recv)
  1070  
  1071  	fpos := r.pos()
  1072  	fn := ir.NewFunc(fpos, npos, ir.MethodSym(recv.Type, sym), typ)
  1073  	name := fn.Nname
  1074  
  1075  	if r.hasTypeParams() {
  1076  		name.Func.SetDupok(true)
  1077  		if r.dict.shaped {
  1078  			typ = shapeSig(name.Func, r.dict)
  1079  			setType(name, typ)
  1080  		}
  1081  	}
  1082  
  1083  	rext.funcExt(name, sym)
  1084  
  1085  	meth := types.NewField(name.Func.Pos(), sym, typ)
  1086  	meth.Nname = name
  1087  	meth.SetNointerface(name.Func.Pragma&ir.Nointerface != 0)
  1088  
  1089  	return meth
  1090  }
  1091  
  1092  func (r *reader) qualifiedIdent() (pkg *types.Pkg, sym *types.Sym) {
  1093  	r.Sync(pkgbits.SyncSym)
  1094  	pkg = r.pkg()
  1095  	if name := r.String(); name != "" {
  1096  		sym = pkg.Lookup(name)
  1097  	}
  1098  	return
  1099  }
  1100  
  1101  func (r *reader) localIdent() *types.Sym {
  1102  	r.Sync(pkgbits.SyncLocalIdent)
  1103  	pkg := r.pkg()
  1104  	if name := r.String(); name != "" {
  1105  		return pkg.Lookup(name)
  1106  	}
  1107  	return nil
  1108  }
  1109  
  1110  func (r *reader) selector() *types.Sym {
  1111  	r.Sync(pkgbits.SyncSelector)
  1112  	pkg := r.pkg()
  1113  	name := r.String()
  1114  	if types.IsExported(name) {
  1115  		pkg = types.LocalPkg
  1116  	}
  1117  	return pkg.Lookup(name)
  1118  }
  1119  
  1120  func (r *reader) hasTypeParams() bool {
  1121  	return r.dict.hasTypeParams()
  1122  }
  1123  
  1124  func (dict *readerDict) hasTypeParams() bool {
  1125  	return dict != nil && len(dict.targs) != 0
  1126  }
  1127  
  1128  // @@@ Compiler extensions
  1129  
  1130  func (r *reader) funcExt(name *ir.Name, method *types.Sym) {
  1131  	r.Sync(pkgbits.SyncFuncExt)
  1132  
  1133  	fn := name.Func
  1134  
  1135  	// XXX: Workaround because linker doesn't know how to copy Pos.
  1136  	if !fn.Pos().IsKnown() {
  1137  		fn.SetPos(name.Pos())
  1138  	}
  1139  
  1140  	// Normally, we only compile local functions, which saves redundant compilation work.
  1141  	// n.Defn is not nil for local functions, and is nil for imported function. But for
  1142  	// generic functions, we might have an instantiation that no other package has seen before.
  1143  	// So we need to be conservative and compile it again.
  1144  	//
  1145  	// That's why name.Defn is set here, so ir.VisitFuncsBottomUp can analyze function.
  1146  	// TODO(mdempsky,cuonglm): find a cleaner way to handle this.
  1147  	if name.Sym().Pkg == types.LocalPkg || r.hasTypeParams() {
  1148  		name.Defn = fn
  1149  	}
  1150  
  1151  	fn.Pragma = r.pragmaFlag()
  1152  	r.linkname(name)
  1153  
  1154  	if buildcfg.GOARCH == "wasm" {
  1155  		importmod := r.String()
  1156  		importname := r.String()
  1157  		exportname := r.String()
  1158  
  1159  		if importmod != "" && importname != "" {
  1160  			fn.WasmImport = &ir.WasmImport{
  1161  				Module: importmod,
  1162  				Name:   importname,
  1163  			}
  1164  		}
  1165  		if exportname != "" {
  1166  			if method != nil {
  1167  				base.ErrorfAt(fn.Pos(), 0, "cannot use //go:wasmexport on a method")
  1168  			}
  1169  			fn.WasmExport = &ir.WasmExport{Name: exportname}
  1170  		}
  1171  	}
  1172  
  1173  	if r.Bool() {
  1174  		assert(name.Defn == nil)
  1175  
  1176  		fn.ABI = obj.ABI(r.Uint64())
  1177  
  1178  		// Escape analysis.
  1179  		for _, f := range name.Type().RecvParams() {
  1180  			f.Note = r.String()
  1181  		}
  1182  
  1183  		if r.Bool() {
  1184  			fn.Inl = &ir.Inline{
  1185  				Cost:            int32(r.Len()),
  1186  				CanDelayResults: r.Bool(),
  1187  			}
  1188  			if buildcfg.Experiment.NewInliner {
  1189  				fn.Inl.Properties = r.String()
  1190  			}
  1191  		}
  1192  	} else {
  1193  		r.addBody(name.Func, method)
  1194  	}
  1195  	r.Sync(pkgbits.SyncEOF)
  1196  }
  1197  
  1198  func (r *reader) typeExt(name *ir.Name) {
  1199  	r.Sync(pkgbits.SyncTypeExt)
  1200  
  1201  	typ := name.Type()
  1202  
  1203  	if r.hasTypeParams() {
  1204  		// Mark type as fully instantiated to ensure the type descriptor is written
  1205  		// out as DUPOK and method wrappers are generated even for imported types.
  1206  		typ.SetIsFullyInstantiated(true)
  1207  		// HasShape should be set if any type argument is or has a shape type.
  1208  		for _, targ := range r.dict.targs {
  1209  			if targ.HasShape() {
  1210  				typ.SetHasShape(true)
  1211  				break
  1212  			}
  1213  		}
  1214  	}
  1215  
  1216  	name.SetPragma(r.pragmaFlag())
  1217  
  1218  	typecheck.SetBaseTypeIndex(typ, r.Int64(), r.Int64())
  1219  }
  1220  
  1221  func (r *reader) varExt(name *ir.Name) {
  1222  	r.Sync(pkgbits.SyncVarExt)
  1223  	r.linkname(name)
  1224  }
  1225  
  1226  func (r *reader) linkname(name *ir.Name) {
  1227  	assert(name.Op() == ir.ONAME)
  1228  	r.Sync(pkgbits.SyncLinkname)
  1229  
  1230  	if idx := r.Int64(); idx >= 0 {
  1231  		lsym := name.Linksym()
  1232  		lsym.SymIdx = int32(idx)
  1233  		lsym.Set(obj.AttrIndexed, true)
  1234  	} else {
  1235  		linkname := r.String()
  1236  		sym := name.Sym()
  1237  		sym.Linkname = linkname
  1238  		if sym.Pkg == types.LocalPkg && linkname != "" {
  1239  			// Mark linkname in the current package. We don't mark the
  1240  			// ones that are imported and propagated (e.g. through
  1241  			// inlining or instantiation, which are marked in their
  1242  			// corresponding packages). So we can tell in which package
  1243  			// the linkname is used (pulled), and the linker can
  1244  			// make a decision for allowing or disallowing it.
  1245  			sym.Linksym().Set(obj.AttrLinkname, true)
  1246  		}
  1247  	}
  1248  }
  1249  
  1250  func (r *reader) pragmaFlag() ir.PragmaFlag {
  1251  	r.Sync(pkgbits.SyncPragma)
  1252  	return ir.PragmaFlag(r.Int())
  1253  }
  1254  
  1255  // @@@ Function bodies
  1256  
  1257  // bodyReader tracks where the serialized IR for a local or imported,
  1258  // generic function's body can be found.
  1259  var bodyReader = map[*ir.Func]pkgReaderIndex{}
  1260  
  1261  // importBodyReader tracks where the serialized IR for an imported,
  1262  // static (i.e., non-generic) function body can be read.
  1263  var importBodyReader = map[*types.Sym]pkgReaderIndex{}
  1264  
  1265  // bodyReaderFor returns the pkgReaderIndex for reading fn's
  1266  // serialized IR, and whether one was found.
  1267  func bodyReaderFor(fn *ir.Func) (pri pkgReaderIndex, ok bool) {
  1268  	if fn.Nname.Defn != nil {
  1269  		pri, ok = bodyReader[fn]
  1270  		base.AssertfAt(ok, base.Pos, "must have bodyReader for %v", fn) // must always be available
  1271  	} else {
  1272  		pri, ok = importBodyReader[fn.Sym()]
  1273  	}
  1274  	return
  1275  }
  1276  
  1277  // todoDicts holds the list of dictionaries that still need their
  1278  // runtime dictionary objects constructed.
  1279  var todoDicts []func()
  1280  
  1281  // todoBodies holds the list of function bodies that still need to be
  1282  // constructed.
  1283  var todoBodies []*ir.Func
  1284  
  1285  // addBody reads a function body reference from the element bitstream,
  1286  // and associates it with fn.
  1287  func (r *reader) addBody(fn *ir.Func, method *types.Sym) {
  1288  	// addBody should only be called for local functions or imported
  1289  	// generic functions; see comment in funcExt.
  1290  	assert(fn.Nname.Defn != nil)
  1291  
  1292  	idx := r.Reloc(pkgbits.SectionBody)
  1293  
  1294  	pri := pkgReaderIndex{r.p, idx, r.dict, method, nil}
  1295  	bodyReader[fn] = pri
  1296  
  1297  	if r.curfn == nil {
  1298  		todoBodies = append(todoBodies, fn)
  1299  		return
  1300  	}
  1301  
  1302  	pri.funcBody(fn)
  1303  }
  1304  
  1305  func (pri pkgReaderIndex) funcBody(fn *ir.Func) {
  1306  	r := pri.asReader(pkgbits.SectionBody, pkgbits.SyncFuncBody)
  1307  	r.funcBody(fn)
  1308  }
  1309  
  1310  // funcBody reads a function body definition from the element
  1311  // bitstream, and populates fn with it.
  1312  func (r *reader) funcBody(fn *ir.Func) {
  1313  	r.curfn = fn
  1314  	r.closureVars = fn.ClosureVars
  1315  	if len(r.closureVars) != 0 && r.hasTypeParams() {
  1316  		r.dictParam = r.closureVars[len(r.closureVars)-1] // dictParam is last; see reader.funcLit
  1317  	}
  1318  
  1319  	ir.WithFunc(fn, func() {
  1320  		r.declareParams()
  1321  
  1322  		if r.syntheticBody(fn.Pos()) {
  1323  			return
  1324  		}
  1325  
  1326  		if !r.Bool() {
  1327  			return
  1328  		}
  1329  
  1330  		body := r.stmts()
  1331  		if body == nil {
  1332  			body = []ir.Node{typecheck.Stmt(ir.NewBlockStmt(src.NoXPos, nil))}
  1333  		}
  1334  		fn.Body = body
  1335  		fn.Endlineno = r.pos()
  1336  	})
  1337  
  1338  	r.marker.WriteTo(fn)
  1339  }
  1340  
  1341  // syntheticBody adds a synthetic body to r.curfn if appropriate, and
  1342  // reports whether it did.
  1343  func (r *reader) syntheticBody(pos src.XPos) bool {
  1344  	if r.synthetic != nil {
  1345  		r.synthetic(pos, r)
  1346  		return true
  1347  	}
  1348  
  1349  	// If this function has type parameters and isn't shaped, then we
  1350  	// just tail call its corresponding shaped variant.
  1351  	if r.hasTypeParams() && !r.dict.shaped {
  1352  		r.callShaped(pos)
  1353  		return true
  1354  	}
  1355  
  1356  	return false
  1357  }
  1358  
  1359  // callShaped emits a tail call to r.shapedFn, passing along the
  1360  // arguments to the current function.
  1361  func (r *reader) callShaped(pos src.XPos) {
  1362  	shapedObj := r.dict.shapedObj
  1363  	assert(shapedObj != nil)
  1364  
  1365  	var shapedFn ir.Node
  1366  	if r.methodSym == nil {
  1367  		// Instantiating a generic function; shapedObj is the shaped
  1368  		// function itself.
  1369  		assert(shapedObj.Op() == ir.ONAME && shapedObj.Class == ir.PFUNC)
  1370  		shapedFn = shapedObj
  1371  	} else {
  1372  		// Instantiating a generic type's method; shapedObj is the shaped
  1373  		// type, so we need to select it's corresponding method.
  1374  		shapedFn = shapedMethodExpr(pos, shapedObj, r.methodSym)
  1375  	}
  1376  
  1377  	params := r.syntheticArgs()
  1378  
  1379  	// Construct the arguments list: receiver (if any), then runtime
  1380  	// dictionary, and finally normal parameters.
  1381  	//
  1382  	// Note: For simplicity, shaped methods are added as normal methods
  1383  	// on their shaped types. So existing code (e.g., packages ir and
  1384  	// typecheck) expects the shaped type to appear as the receiver
  1385  	// parameter (or first parameter, as a method expression). Hence
  1386  	// putting the dictionary parameter after that is the least invasive
  1387  	// solution at the moment.
  1388  	var args ir.Nodes
  1389  	if r.methodSym != nil {
  1390  		args.Append(params[0])
  1391  		params = params[1:]
  1392  	}
  1393  	args.Append(typecheck.Expr(ir.NewAddrExpr(pos, r.p.dictNameOf(r.dict))))
  1394  	args.Append(params...)
  1395  
  1396  	r.syntheticTailCall(pos, shapedFn, args)
  1397  }
  1398  
  1399  // syntheticArgs returns the recvs and params arguments passed to the
  1400  // current function.
  1401  func (r *reader) syntheticArgs() ir.Nodes {
  1402  	sig := r.curfn.Nname.Type()
  1403  	return ir.ToNodes(r.curfn.Dcl[:sig.NumRecvs()+sig.NumParams()])
  1404  }
  1405  
  1406  // syntheticTailCall emits a tail call to fn, passing the given
  1407  // arguments list.
  1408  func (r *reader) syntheticTailCall(pos src.XPos, fn ir.Node, args ir.Nodes) {
  1409  	// Mark the function as a wrapper so it doesn't show up in stack
  1410  	// traces.
  1411  	r.curfn.SetWrapper(true)
  1412  
  1413  	call := typecheck.Call(pos, fn, args, fn.Type().IsVariadic()).(*ir.CallExpr)
  1414  
  1415  	var stmt ir.Node
  1416  	if fn.Type().NumResults() != 0 {
  1417  		stmt = typecheck.Stmt(ir.NewReturnStmt(pos, []ir.Node{call}))
  1418  	} else {
  1419  		stmt = call
  1420  	}
  1421  	r.curfn.Body.Append(stmt)
  1422  }
  1423  
  1424  // dictNameOf returns the runtime dictionary corresponding to dict.
  1425  func (pr *pkgReader) dictNameOf(dict *readerDict) *ir.Name {
  1426  	pos := base.AutogeneratedPos
  1427  
  1428  	// Check that we only instantiate runtime dictionaries with real types.
  1429  	base.AssertfAt(!dict.shaped, pos, "runtime dictionary of shaped object %v", dict.baseSym)
  1430  
  1431  	sym := dict.baseSym.Pkg.Lookup(objabi.GlobalDictPrefix + "." + dict.baseSym.Name)
  1432  	if sym.Def != nil {
  1433  		return sym.Def.(*ir.Name)
  1434  	}
  1435  
  1436  	name := ir.NewNameAt(pos, sym, dict.varType())
  1437  	name.Class = ir.PEXTERN
  1438  	sym.Def = name // break cycles with mutual subdictionaries
  1439  
  1440  	lsym := name.Linksym()
  1441  	ot := 0
  1442  
  1443  	assertOffset := func(section string, offset int) {
  1444  		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)
  1445  	}
  1446  
  1447  	assertOffset("type param method exprs", dict.typeParamMethodExprsOffset())
  1448  	for _, info := range dict.typeParamMethodExprs {
  1449  		typeParam := dict.targs[info.typeParamIdx]
  1450  		method := typecheck.NewMethodExpr(pos, typeParam, info.method)
  1451  
  1452  		rsym := method.FuncName().Linksym()
  1453  		assert(rsym.ABI() == obj.ABIInternal) // must be ABIInternal; see ir.OCFUNC in ssagen/ssa.go
  1454  
  1455  		ot = objw.SymPtr(lsym, ot, rsym, 0)
  1456  	}
  1457  
  1458  	assertOffset("subdictionaries", dict.subdictsOffset())
  1459  	for _, info := range dict.subdicts {
  1460  		explicits := pr.typListIdx(info.explicits, dict)
  1461  
  1462  		// Careful: Due to subdictionary cycles, name may not be fully
  1463  		// initialized yet.
  1464  		name := pr.objDictName(info.idx, dict.targs, explicits)
  1465  
  1466  		ot = objw.SymPtr(lsym, ot, name.Linksym(), 0)
  1467  	}
  1468  
  1469  	assertOffset("rtypes", dict.rtypesOffset())
  1470  	for _, info := range dict.rtypes {
  1471  		typ := pr.typIdx(info, dict, true)
  1472  		ot = objw.SymPtr(lsym, ot, reflectdata.TypeLinksym(typ), 0)
  1473  
  1474  		// TODO(mdempsky): Double check this.
  1475  		reflectdata.MarkTypeUsedInInterface(typ, lsym)
  1476  	}
  1477  
  1478  	// For each (typ, iface) pair, we write the *runtime.itab pointer
  1479  	// for the pair. For pairs that don't actually require an itab
  1480  	// (i.e., typ is an interface, or iface is an empty interface), we
  1481  	// write a nil pointer instead. This is wasteful, but rare in
  1482  	// practice (e.g., instantiating a type parameter with an interface
  1483  	// type).
  1484  	assertOffset("itabs", dict.itabsOffset())
  1485  	for _, info := range dict.itabs {
  1486  		typ := pr.typIdx(info.typ, dict, true)
  1487  		iface := pr.typIdx(info.iface, dict, true)
  1488  
  1489  		if !typ.IsInterface() && iface.IsInterface() && !iface.IsEmptyInterface() {
  1490  			ot = objw.SymPtr(lsym, ot, reflectdata.ITabLsym(typ, iface), 0)
  1491  		} else {
  1492  			ot += types.PtrSize
  1493  		}
  1494  
  1495  		// TODO(mdempsky): Double check this.
  1496  		reflectdata.MarkTypeUsedInInterface(typ, lsym)
  1497  		reflectdata.MarkTypeUsedInInterface(iface, lsym)
  1498  	}
  1499  
  1500  	objw.Global(lsym, int32(ot), obj.DUPOK|obj.RODATA)
  1501  
  1502  	return name
  1503  }
  1504  
  1505  // typeParamMethodExprsOffset returns the offset of the runtime
  1506  // dictionary's type parameter method expressions section, in words.
  1507  func (dict *readerDict) typeParamMethodExprsOffset() int {
  1508  	return 0
  1509  }
  1510  
  1511  // subdictsOffset returns the offset of the runtime dictionary's
  1512  // subdictionary section, in words.
  1513  func (dict *readerDict) subdictsOffset() int {
  1514  	return dict.typeParamMethodExprsOffset() + len(dict.typeParamMethodExprs)
  1515  }
  1516  
  1517  // rtypesOffset returns the offset of the runtime dictionary's rtypes
  1518  // section, in words.
  1519  func (dict *readerDict) rtypesOffset() int {
  1520  	return dict.subdictsOffset() + len(dict.subdicts)
  1521  }
  1522  
  1523  // itabsOffset returns the offset of the runtime dictionary's itabs
  1524  // section, in words.
  1525  func (dict *readerDict) itabsOffset() int {
  1526  	return dict.rtypesOffset() + len(dict.rtypes)
  1527  }
  1528  
  1529  // numWords returns the total number of words that comprise dict's
  1530  // runtime dictionary variable.
  1531  func (dict *readerDict) numWords() int64 {
  1532  	return int64(dict.itabsOffset() + len(dict.itabs))
  1533  }
  1534  
  1535  // varType returns the type of dict's runtime dictionary variable.
  1536  func (dict *readerDict) varType() *types.Type {
  1537  	return types.NewArray(types.Types[types.TUINTPTR], dict.numWords())
  1538  }
  1539  
  1540  func (r *reader) declareParams() {
  1541  	r.curfn.DeclareParams(!r.funarghack)
  1542  
  1543  	for _, name := range r.curfn.Dcl {
  1544  		if name.Sym().Name == dictParamName {
  1545  			r.dictParam = name
  1546  			continue
  1547  		}
  1548  
  1549  		r.addLocal(name)
  1550  	}
  1551  }
  1552  
  1553  func (r *reader) addLocal(name *ir.Name) {
  1554  	if r.synthetic == nil {
  1555  		r.Sync(pkgbits.SyncAddLocal)
  1556  		if r.p.SyncMarkers() {
  1557  			want := r.Int()
  1558  			if have := len(r.locals); have != want {
  1559  				base.FatalfAt(name.Pos(), "locals table has desynced")
  1560  			}
  1561  		}
  1562  		r.varDictIndex(name)
  1563  	}
  1564  
  1565  	r.locals = append(r.locals, name)
  1566  }
  1567  
  1568  func (r *reader) useLocal() *ir.Name {
  1569  	r.Sync(pkgbits.SyncUseObjLocal)
  1570  	if r.Bool() {
  1571  		return r.locals[r.Len()]
  1572  	}
  1573  	return r.closureVars[r.Len()]
  1574  }
  1575  
  1576  func (r *reader) openScope() {
  1577  	r.Sync(pkgbits.SyncOpenScope)
  1578  	pos := r.pos()
  1579  
  1580  	if base.Flag.Dwarf {
  1581  		r.scopeVars = append(r.scopeVars, len(r.curfn.Dcl))
  1582  		r.marker.Push(pos)
  1583  	}
  1584  }
  1585  
  1586  func (r *reader) closeScope() {
  1587  	r.Sync(pkgbits.SyncCloseScope)
  1588  	r.lastCloseScopePos = r.pos()
  1589  
  1590  	r.closeAnotherScope()
  1591  }
  1592  
  1593  // closeAnotherScope is like closeScope, but it reuses the same mark
  1594  // position as the last closeScope call. This is useful for "for" and
  1595  // "if" statements, as their implicit blocks always end at the same
  1596  // position as an explicit block.
  1597  func (r *reader) closeAnotherScope() {
  1598  	r.Sync(pkgbits.SyncCloseAnotherScope)
  1599  
  1600  	if base.Flag.Dwarf {
  1601  		scopeVars := r.scopeVars[len(r.scopeVars)-1]
  1602  		r.scopeVars = r.scopeVars[:len(r.scopeVars)-1]
  1603  
  1604  		// Quirkish: noder decides which scopes to keep before
  1605  		// typechecking, whereas incremental typechecking during IR
  1606  		// construction can result in new autotemps being allocated. To
  1607  		// produce identical output, we ignore autotemps here for the
  1608  		// purpose of deciding whether to retract the scope.
  1609  		//
  1610  		// This is important for net/http/fcgi, because it contains:
  1611  		//
  1612  		//	var body io.ReadCloser
  1613  		//	if len(content) > 0 {
  1614  		//		body, req.pw = io.Pipe()
  1615  		//	} else { … }
  1616  		//
  1617  		// Notably, io.Pipe is inlinable, and inlining it introduces a ~R0
  1618  		// variable at the call site.
  1619  		//
  1620  		// Noder does not preserve the scope where the io.Pipe() call
  1621  		// resides, because it doesn't contain any declared variables in
  1622  		// source. So the ~R0 variable ends up being assigned to the
  1623  		// enclosing scope instead.
  1624  		//
  1625  		// However, typechecking this assignment also introduces
  1626  		// autotemps, because io.Pipe's results need conversion before
  1627  		// they can be assigned to their respective destination variables.
  1628  		//
  1629  		// TODO(mdempsky): We should probably just keep all scopes, and
  1630  		// let dwarfgen take care of pruning them instead.
  1631  		retract := true
  1632  		for _, n := range r.curfn.Dcl[scopeVars:] {
  1633  			if !n.AutoTemp() {
  1634  				retract = false
  1635  				break
  1636  			}
  1637  		}
  1638  
  1639  		if retract {
  1640  			// no variables were declared in this scope, so we can retract it.
  1641  			r.marker.Unpush()
  1642  		} else {
  1643  			r.marker.Pop(r.lastCloseScopePos)
  1644  		}
  1645  	}
  1646  }
  1647  
  1648  // @@@ Statements
  1649  
  1650  func (r *reader) stmt() ir.Node {
  1651  	return block(r.stmts())
  1652  }
  1653  
  1654  func block(stmts []ir.Node) ir.Node {
  1655  	switch len(stmts) {
  1656  	case 0:
  1657  		return nil
  1658  	case 1:
  1659  		return stmts[0]
  1660  	default:
  1661  		return ir.NewBlockStmt(stmts[0].Pos(), stmts)
  1662  	}
  1663  }
  1664  
  1665  func (r *reader) stmts() ir.Nodes {
  1666  	assert(ir.CurFunc == r.curfn)
  1667  	var res ir.Nodes
  1668  
  1669  	r.Sync(pkgbits.SyncStmts)
  1670  	for {
  1671  		tag := codeStmt(r.Code(pkgbits.SyncStmt1))
  1672  		if tag == stmtEnd {
  1673  			r.Sync(pkgbits.SyncStmtsEnd)
  1674  			return res
  1675  		}
  1676  
  1677  		if n := r.stmt1(tag, &res); n != nil {
  1678  			res.Append(typecheck.Stmt(n))
  1679  		}
  1680  	}
  1681  }
  1682  
  1683  func (r *reader) stmt1(tag codeStmt, out *ir.Nodes) ir.Node {
  1684  	var label *types.Sym
  1685  	if n := len(*out); n > 0 {
  1686  		if ls, ok := (*out)[n-1].(*ir.LabelStmt); ok {
  1687  			label = ls.Label
  1688  		}
  1689  	}
  1690  
  1691  	switch tag {
  1692  	default:
  1693  		panic("unexpected statement")
  1694  
  1695  	case stmtAssign:
  1696  		pos := r.pos()
  1697  		names, lhs := r.assignList()
  1698  		rhs := r.multiExpr()
  1699  
  1700  		if len(rhs) == 0 {
  1701  			for _, name := range names {
  1702  				as := ir.NewAssignStmt(pos, name, nil)
  1703  				as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, name))
  1704  				out.Append(typecheck.Stmt(as))
  1705  			}
  1706  			return nil
  1707  		}
  1708  
  1709  		if len(lhs) == 1 && len(rhs) == 1 {
  1710  			n := ir.NewAssignStmt(pos, lhs[0], rhs[0])
  1711  			n.Def = r.initDefn(n, names)
  1712  			return n
  1713  		}
  1714  
  1715  		n := ir.NewAssignListStmt(pos, ir.OAS2, lhs, rhs)
  1716  		n.Def = r.initDefn(n, names)
  1717  		return n
  1718  
  1719  	case stmtAssignOp:
  1720  		op := r.op()
  1721  		lhs := r.expr()
  1722  		pos := r.pos()
  1723  		rhs := r.expr()
  1724  		return ir.NewAssignOpStmt(pos, op, lhs, rhs)
  1725  
  1726  	case stmtIncDec:
  1727  		op := r.op()
  1728  		lhs := r.expr()
  1729  		pos := r.pos()
  1730  		n := ir.NewAssignOpStmt(pos, op, lhs, ir.NewOne(pos, lhs.Type()))
  1731  		n.IncDec = true
  1732  		return n
  1733  
  1734  	case stmtBlock:
  1735  		out.Append(r.blockStmt()...)
  1736  		return nil
  1737  
  1738  	case stmtBranch:
  1739  		pos := r.pos()
  1740  		op := r.op()
  1741  		sym := r.optLabel()
  1742  		return ir.NewBranchStmt(pos, op, sym)
  1743  
  1744  	case stmtCall:
  1745  		pos := r.pos()
  1746  		op := r.op()
  1747  		call := r.expr()
  1748  		stmt := ir.NewGoDeferStmt(pos, op, call)
  1749  		if op == ir.ODEFER {
  1750  			x := r.optExpr()
  1751  			if x != nil {
  1752  				stmt.DeferAt = x.(ir.Expr)
  1753  			}
  1754  		}
  1755  		return stmt
  1756  
  1757  	case stmtExpr:
  1758  		return r.expr()
  1759  
  1760  	case stmtFor:
  1761  		return r.forStmt(label)
  1762  
  1763  	case stmtIf:
  1764  		return r.ifStmt()
  1765  
  1766  	case stmtLabel:
  1767  		pos := r.pos()
  1768  		sym := r.label()
  1769  		return ir.NewLabelStmt(pos, sym)
  1770  
  1771  	case stmtReturn:
  1772  		pos := r.pos()
  1773  		results := r.multiExpr()
  1774  		return ir.NewReturnStmt(pos, results)
  1775  
  1776  	case stmtSelect:
  1777  		return r.selectStmt(label)
  1778  
  1779  	case stmtSend:
  1780  		pos := r.pos()
  1781  		ch := r.expr()
  1782  		value := r.expr()
  1783  		return ir.NewSendStmt(pos, ch, value)
  1784  
  1785  	case stmtSwitch:
  1786  		return r.switchStmt(label)
  1787  	}
  1788  }
  1789  
  1790  func (r *reader) assignList() ([]*ir.Name, []ir.Node) {
  1791  	lhs := make([]ir.Node, r.Len())
  1792  	var names []*ir.Name
  1793  
  1794  	for i := range lhs {
  1795  		expr, def := r.assign()
  1796  		lhs[i] = expr
  1797  		if def {
  1798  			names = append(names, expr.(*ir.Name))
  1799  		}
  1800  	}
  1801  
  1802  	return names, lhs
  1803  }
  1804  
  1805  // assign returns an assignee expression. It also reports whether the
  1806  // returned expression is a newly declared variable.
  1807  func (r *reader) assign() (ir.Node, bool) {
  1808  	switch tag := codeAssign(r.Code(pkgbits.SyncAssign)); tag {
  1809  	default:
  1810  		panic("unhandled assignee expression")
  1811  
  1812  	case assignBlank:
  1813  		return typecheck.AssignExpr(ir.BlankNode), false
  1814  
  1815  	case assignDef:
  1816  		pos := r.pos()
  1817  		setBasePos(pos) // test/fixedbugs/issue49767.go depends on base.Pos being set for the r.typ() call here, ugh
  1818  		name := r.curfn.NewLocal(pos, r.localIdent(), r.typ())
  1819  		r.addLocal(name)
  1820  		return name, true
  1821  
  1822  	case assignExpr:
  1823  		return r.expr(), false
  1824  	}
  1825  }
  1826  
  1827  func (r *reader) blockStmt() []ir.Node {
  1828  	r.Sync(pkgbits.SyncBlockStmt)
  1829  	r.openScope()
  1830  	stmts := r.stmts()
  1831  	r.closeScope()
  1832  	return stmts
  1833  }
  1834  
  1835  func (r *reader) forStmt(label *types.Sym) ir.Node {
  1836  	r.Sync(pkgbits.SyncForStmt)
  1837  
  1838  	r.openScope()
  1839  
  1840  	if r.Bool() {
  1841  		pos := r.pos()
  1842  		rang := ir.NewRangeStmt(pos, nil, nil, nil, nil, false)
  1843  		rang.Label = label
  1844  
  1845  		names, lhs := r.assignList()
  1846  		if len(lhs) >= 1 {
  1847  			rang.Key = lhs[0]
  1848  			if len(lhs) >= 2 {
  1849  				rang.Value = lhs[1]
  1850  			}
  1851  		}
  1852  		rang.Def = r.initDefn(rang, names)
  1853  
  1854  		rang.X = r.expr()
  1855  		if rang.X.Type().IsMap() {
  1856  			rang.RType = r.rtype(pos)
  1857  		}
  1858  		if rang.Key != nil && !ir.IsBlank(rang.Key) {
  1859  			rang.KeyTypeWord, rang.KeySrcRType = r.convRTTI(pos)
  1860  		}
  1861  		if rang.Value != nil && !ir.IsBlank(rang.Value) {
  1862  			rang.ValueTypeWord, rang.ValueSrcRType = r.convRTTI(pos)
  1863  		}
  1864  
  1865  		rang.Body = r.blockStmt()
  1866  		rang.DistinctVars = r.Bool()
  1867  		r.closeAnotherScope()
  1868  
  1869  		return rang
  1870  	}
  1871  
  1872  	pos := r.pos()
  1873  	init := r.stmt()
  1874  	cond := r.optExpr()
  1875  	post := r.stmt()
  1876  	body := r.blockStmt()
  1877  	perLoopVars := r.Bool()
  1878  	r.closeAnotherScope()
  1879  
  1880  	if ir.IsConst(cond, constant.Bool) && !ir.BoolVal(cond) {
  1881  		return init // simplify "for init; false; post { ... }" into "init"
  1882  	}
  1883  
  1884  	stmt := ir.NewForStmt(pos, init, cond, post, body, perLoopVars)
  1885  	stmt.Label = label
  1886  	return stmt
  1887  }
  1888  
  1889  func (r *reader) ifStmt() ir.Node {
  1890  	r.Sync(pkgbits.SyncIfStmt)
  1891  	r.openScope()
  1892  	pos := r.pos()
  1893  	init := r.stmts()
  1894  	cond := r.expr()
  1895  	staticCond := r.Int()
  1896  	var then, els []ir.Node
  1897  	if staticCond >= 0 {
  1898  		then = r.blockStmt()
  1899  	} else {
  1900  		r.lastCloseScopePos = r.pos()
  1901  	}
  1902  	if staticCond <= 0 {
  1903  		els = r.stmts()
  1904  	}
  1905  	r.closeAnotherScope()
  1906  
  1907  	if staticCond != 0 {
  1908  		// We may have removed a dead return statement, which can trip up
  1909  		// later passes (#62211). To avoid confusion, we instead flatten
  1910  		// the if statement into a block.
  1911  
  1912  		if cond.Op() != ir.OLITERAL {
  1913  			init.Append(typecheck.Stmt(ir.NewAssignStmt(pos, ir.BlankNode, cond))) // for side effects
  1914  		}
  1915  		init.Append(then...)
  1916  		init.Append(els...)
  1917  		return block(init)
  1918  	}
  1919  
  1920  	n := ir.NewIfStmt(pos, cond, then, els)
  1921  	n.SetInit(init)
  1922  	return n
  1923  }
  1924  
  1925  func (r *reader) selectStmt(label *types.Sym) ir.Node {
  1926  	r.Sync(pkgbits.SyncSelectStmt)
  1927  
  1928  	pos := r.pos()
  1929  	clauses := make([]*ir.CommClause, r.Len())
  1930  	for i := range clauses {
  1931  		if i > 0 {
  1932  			r.closeScope()
  1933  		}
  1934  		r.openScope()
  1935  
  1936  		pos := r.pos()
  1937  		comm := r.stmt()
  1938  		body := r.stmts()
  1939  
  1940  		// "case i = <-c: ..." may require an implicit conversion (e.g.,
  1941  		// see fixedbugs/bug312.go). Currently, typecheck throws away the
  1942  		// implicit conversion and relies on it being reinserted later,
  1943  		// but that would lose any explicit RTTI operands too. To preserve
  1944  		// RTTI, we rewrite this as "case tmp := <-c: i = tmp; ...".
  1945  		if as, ok := comm.(*ir.AssignStmt); ok && as.Op() == ir.OAS && !as.Def {
  1946  			if conv, ok := as.Y.(*ir.ConvExpr); ok && conv.Op() == ir.OCONVIFACE {
  1947  				base.AssertfAt(conv.Implicit(), conv.Pos(), "expected implicit conversion: %v", conv)
  1948  
  1949  				recv := conv.X
  1950  				base.AssertfAt(recv.Op() == ir.ORECV, recv.Pos(), "expected receive expression: %v", recv)
  1951  
  1952  				tmp := r.temp(pos, recv.Type())
  1953  
  1954  				// Replace comm with `tmp := <-c`.
  1955  				tmpAs := ir.NewAssignStmt(pos, tmp, recv)
  1956  				tmpAs.Def = true
  1957  				tmpAs.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
  1958  				comm = tmpAs
  1959  
  1960  				// Change original assignment to `i = tmp`, and prepend to body.
  1961  				conv.X = tmp
  1962  				body = append([]ir.Node{as}, body...)
  1963  			}
  1964  		}
  1965  
  1966  		// multiExpr will have desugared a comma-ok receive expression
  1967  		// into a separate statement. However, the rest of the compiler
  1968  		// expects comm to be the OAS2RECV statement itself, so we need to
  1969  		// shuffle things around to fit that pattern.
  1970  		if as2, ok := comm.(*ir.AssignListStmt); ok && as2.Op() == ir.OAS2 {
  1971  			init := ir.TakeInit(as2.Rhs[0])
  1972  			base.AssertfAt(len(init) == 1 && init[0].Op() == ir.OAS2RECV, as2.Pos(), "unexpected assignment: %+v", as2)
  1973  
  1974  			comm = init[0]
  1975  			body = append([]ir.Node{as2}, body...)
  1976  		}
  1977  
  1978  		clauses[i] = ir.NewCommStmt(pos, comm, body)
  1979  	}
  1980  	if len(clauses) > 0 {
  1981  		r.closeScope()
  1982  	}
  1983  	n := ir.NewSelectStmt(pos, clauses)
  1984  	n.Label = label
  1985  	return n
  1986  }
  1987  
  1988  func (r *reader) switchStmt(label *types.Sym) ir.Node {
  1989  	r.Sync(pkgbits.SyncSwitchStmt)
  1990  
  1991  	r.openScope()
  1992  	pos := r.pos()
  1993  	init := r.stmt()
  1994  
  1995  	var tag ir.Node
  1996  	var ident *ir.Ident
  1997  	var iface *types.Type
  1998  	if r.Bool() {
  1999  		pos := r.pos()
  2000  		if r.Bool() {
  2001  			ident = ir.NewIdent(r.pos(), r.localIdent())
  2002  		}
  2003  		x := r.expr()
  2004  		iface = x.Type()
  2005  		tag = ir.NewTypeSwitchGuard(pos, ident, x)
  2006  	} else {
  2007  		tag = r.optExpr()
  2008  	}
  2009  
  2010  	clauses := make([]*ir.CaseClause, r.Len())
  2011  	for i := range clauses {
  2012  		if i > 0 {
  2013  			r.closeScope()
  2014  		}
  2015  		r.openScope()
  2016  
  2017  		pos := r.pos()
  2018  		var cases, rtypes []ir.Node
  2019  		if iface != nil {
  2020  			cases = make([]ir.Node, r.Len())
  2021  			if len(cases) == 0 {
  2022  				cases = nil // TODO(mdempsky): Unclear if this matters.
  2023  			}
  2024  			for i := range cases {
  2025  				if r.Bool() { // case nil
  2026  					cases[i] = typecheck.Expr(types.BuiltinPkg.Lookup("nil").Def.(*ir.NilExpr))
  2027  				} else {
  2028  					cases[i] = r.exprType()
  2029  				}
  2030  			}
  2031  		} else {
  2032  			cases = r.exprList()
  2033  
  2034  			// For `switch { case any(true): }` (e.g., issue 3980 in
  2035  			// test/switch.go), the backend still creates a mixed bool/any
  2036  			// comparison, and we need to explicitly supply the RTTI for the
  2037  			// comparison.
  2038  			//
  2039  			// TODO(mdempsky): Change writer.go to desugar "switch {" into
  2040  			// "switch true {", which we already handle correctly.
  2041  			if tag == nil {
  2042  				for i, cas := range cases {
  2043  					if cas.Type().IsEmptyInterface() {
  2044  						for len(rtypes) < i {
  2045  							rtypes = append(rtypes, nil)
  2046  						}
  2047  						rtypes = append(rtypes, reflectdata.TypePtrAt(cas.Pos(), types.Types[types.TBOOL]))
  2048  					}
  2049  				}
  2050  			}
  2051  		}
  2052  
  2053  		clause := ir.NewCaseStmt(pos, cases, nil)
  2054  		clause.RTypes = rtypes
  2055  
  2056  		if ident != nil {
  2057  			name := r.curfn.NewLocal(r.pos(), ident.Sym(), r.typ())
  2058  			r.addLocal(name)
  2059  			clause.Var = name
  2060  			name.Defn = tag
  2061  		}
  2062  
  2063  		clause.Body = r.stmts()
  2064  		clauses[i] = clause
  2065  	}
  2066  	if len(clauses) > 0 {
  2067  		r.closeScope()
  2068  	}
  2069  	r.closeScope()
  2070  
  2071  	n := ir.NewSwitchStmt(pos, tag, clauses)
  2072  	n.Label = label
  2073  	if init != nil {
  2074  		n.SetInit([]ir.Node{init})
  2075  	}
  2076  	return n
  2077  }
  2078  
  2079  func (r *reader) label() *types.Sym {
  2080  	r.Sync(pkgbits.SyncLabel)
  2081  	name := r.String()
  2082  	if r.inlCall != nil && name != "_" {
  2083  		name = fmt.Sprintf("~%s·%d", name, inlgen)
  2084  	}
  2085  	return typecheck.Lookup(name)
  2086  }
  2087  
  2088  func (r *reader) optLabel() *types.Sym {
  2089  	r.Sync(pkgbits.SyncOptLabel)
  2090  	if r.Bool() {
  2091  		return r.label()
  2092  	}
  2093  	return nil
  2094  }
  2095  
  2096  // initDefn marks the given names as declared by defn and populates
  2097  // its Init field with ODCL nodes. It then reports whether any names
  2098  // were so declared, which can be used to initialize defn.Def.
  2099  func (r *reader) initDefn(defn ir.InitNode, names []*ir.Name) bool {
  2100  	if len(names) == 0 {
  2101  		return false
  2102  	}
  2103  
  2104  	init := make([]ir.Node, len(names))
  2105  	for i, name := range names {
  2106  		name.Defn = defn
  2107  		init[i] = ir.NewDecl(name.Pos(), ir.ODCL, name)
  2108  	}
  2109  	defn.SetInit(init)
  2110  	return true
  2111  }
  2112  
  2113  // @@@ Expressions
  2114  
  2115  // expr reads and returns a typechecked expression.
  2116  func (r *reader) expr() (res ir.Node) {
  2117  	defer func() {
  2118  		if res != nil && res.Typecheck() == 0 {
  2119  			base.FatalfAt(res.Pos(), "%v missed typecheck", res)
  2120  		}
  2121  	}()
  2122  
  2123  	switch tag := codeExpr(r.Code(pkgbits.SyncExpr)); tag {
  2124  	default:
  2125  		panic("unhandled expression")
  2126  
  2127  	case exprLocal:
  2128  		return typecheck.Expr(r.useLocal())
  2129  
  2130  	case exprGlobal:
  2131  		// Callee instead of Expr allows builtins
  2132  		// TODO(mdempsky): Handle builtins directly in exprCall, like method calls?
  2133  		return typecheck.Callee(r.obj())
  2134  
  2135  	case exprFuncInst:
  2136  		origPos, pos := r.origPos()
  2137  		wrapperFn, baseFn, dictPtr := r.funcInst(pos)
  2138  		if wrapperFn != nil {
  2139  			return wrapperFn
  2140  		}
  2141  		return r.curry(origPos, false, baseFn, dictPtr, nil)
  2142  
  2143  	case exprConst:
  2144  		pos := r.pos()
  2145  		typ := r.typ()
  2146  		val := FixValue(typ, r.Value())
  2147  		return ir.NewBasicLit(pos, typ, val)
  2148  
  2149  	case exprZero:
  2150  		pos := r.pos()
  2151  		typ := r.typ()
  2152  		return ir.NewZero(pos, typ)
  2153  
  2154  	case exprCompLit:
  2155  		return r.compLit()
  2156  
  2157  	case exprFuncLit:
  2158  		return r.funcLit()
  2159  
  2160  	case exprFieldVal:
  2161  		x := r.expr()
  2162  		pos := r.pos()
  2163  		sym := r.selector()
  2164  
  2165  		return typecheck.XDotField(pos, x, sym)
  2166  
  2167  	case exprMethodVal:
  2168  		recv := r.expr()
  2169  		origPos, pos := r.origPos()
  2170  		wrapperFn, baseFn, dictPtr := r.methodExpr()
  2171  
  2172  		// For simple wrapperFn values, the existing machinery for creating
  2173  		// and deduplicating wrapperFn value wrappers still works fine.
  2174  		if wrapperFn, ok := wrapperFn.(*ir.SelectorExpr); ok && wrapperFn.Op() == ir.OMETHEXPR {
  2175  			// The receiver expression we constructed may have a shape type.
  2176  			// For example, in fixedbugs/issue54343.go, `New[int]()` is
  2177  			// constructed as `New[go.shape.int](&.dict.New[int])`, which
  2178  			// has type `*T[go.shape.int]`, not `*T[int]`.
  2179  			//
  2180  			// However, the method we want to select here is `(*T[int]).M`,
  2181  			// not `(*T[go.shape.int]).M`, so we need to manually convert
  2182  			// the type back so that the OXDOT resolves correctly.
  2183  			//
  2184  			// TODO(mdempsky): Logically it might make more sense for
  2185  			// exprCall to take responsibility for setting a non-shaped
  2186  			// result type, but this is the only place where we care
  2187  			// currently. And only because existing ir.OMETHVALUE backend
  2188  			// code relies on n.X.Type() instead of n.Selection.Recv().Type
  2189  			// (because the latter is types.FakeRecvType() in the case of
  2190  			// interface method values).
  2191  			//
  2192  			if recv.Type().HasShape() {
  2193  				typ := wrapperFn.Type().Param(0).Type
  2194  				if !types.Identical(typ, recv.Type()) {
  2195  					base.FatalfAt(wrapperFn.Pos(), "receiver %L does not match %L", recv, wrapperFn)
  2196  				}
  2197  				recv = typecheck.Expr(ir.NewConvExpr(recv.Pos(), ir.OCONVNOP, typ, recv))
  2198  			}
  2199  
  2200  			n := typecheck.XDotMethod(pos, recv, wrapperFn.Sel, false)
  2201  
  2202  			// As a consistency check here, we make sure "n" selected the
  2203  			// same method (represented by a types.Field) that wrapperFn
  2204  			// selected. However, for anonymous receiver types, there can be
  2205  			// multiple such types.Field instances (#58563). So we may need
  2206  			// to fallback to making sure Sym and Type (including the
  2207  			// receiver parameter's type) match.
  2208  			if n.Selection != wrapperFn.Selection {
  2209  				assert(n.Selection.Sym == wrapperFn.Selection.Sym)
  2210  				assert(types.Identical(n.Selection.Type, wrapperFn.Selection.Type))
  2211  				assert(types.Identical(n.Selection.Type.Recv().Type, wrapperFn.Selection.Type.Recv().Type))
  2212  			}
  2213  
  2214  			wrapper := methodValueWrapper{
  2215  				rcvr:   n.X.Type(),
  2216  				method: n.Selection,
  2217  			}
  2218  
  2219  			if r.importedDef() {
  2220  				haveMethodValueWrappers = append(haveMethodValueWrappers, wrapper)
  2221  			} else {
  2222  				needMethodValueWrappers = append(needMethodValueWrappers, wrapper)
  2223  			}
  2224  			return n
  2225  		}
  2226  
  2227  		// For more complicated method expressions, we construct a
  2228  		// function literal wrapper.
  2229  		return r.curry(origPos, true, baseFn, recv, dictPtr)
  2230  
  2231  	case exprMethodExpr:
  2232  		recv := r.typ()
  2233  
  2234  		implicits := make([]int, r.Len())
  2235  		for i := range implicits {
  2236  			implicits[i] = r.Len()
  2237  		}
  2238  		var deref, addr bool
  2239  		if r.Bool() {
  2240  			deref = true
  2241  		} else if r.Bool() {
  2242  			addr = true
  2243  		}
  2244  
  2245  		origPos, pos := r.origPos()
  2246  		wrapperFn, baseFn, dictPtr := r.methodExpr()
  2247  
  2248  		// If we already have a wrapper and don't need to do anything with
  2249  		// it, we can just return the wrapper directly.
  2250  		//
  2251  		// N.B., we use implicits/deref/addr here as the source of truth
  2252  		// rather than types.Identical, because the latter can be confused
  2253  		// by tricky promoted methods (e.g., typeparam/mdempsky/21.go).
  2254  		if wrapperFn != nil && len(implicits) == 0 && !deref && !addr {
  2255  			if !types.Identical(recv, wrapperFn.Type().Param(0).Type) {
  2256  				base.FatalfAt(pos, "want receiver type %v, but have method %L", recv, wrapperFn)
  2257  			}
  2258  			return wrapperFn
  2259  		}
  2260  
  2261  		// Otherwise, if the wrapper function is a static method
  2262  		// expression (OMETHEXPR) and the receiver type is unshaped, then
  2263  		// we can rely on a statically generated wrapper being available.
  2264  		if method, ok := wrapperFn.(*ir.SelectorExpr); ok && method.Op() == ir.OMETHEXPR && !recv.HasShape() {
  2265  			return typecheck.NewMethodExpr(pos, recv, method.Sel)
  2266  		}
  2267  
  2268  		return r.methodExprWrap(origPos, recv, implicits, deref, addr, baseFn, dictPtr)
  2269  
  2270  	case exprIndex:
  2271  		x := r.expr()
  2272  		pos := r.pos()
  2273  		index := r.expr()
  2274  		n := typecheck.Expr(ir.NewIndexExpr(pos, x, index))
  2275  		switch n.Op() {
  2276  		case ir.OINDEXMAP:
  2277  			n := n.(*ir.IndexExpr)
  2278  			n.RType = r.rtype(pos)
  2279  		}
  2280  		return n
  2281  
  2282  	case exprSlice:
  2283  		x := r.expr()
  2284  		pos := r.pos()
  2285  		var index [3]ir.Node
  2286  		for i := range index {
  2287  			index[i] = r.optExpr()
  2288  		}
  2289  		op := ir.OSLICE
  2290  		if index[2] != nil {
  2291  			op = ir.OSLICE3
  2292  		}
  2293  		return typecheck.Expr(ir.NewSliceExpr(pos, op, x, index[0], index[1], index[2]))
  2294  
  2295  	case exprAssert:
  2296  		x := r.expr()
  2297  		pos := r.pos()
  2298  		typ := r.exprType()
  2299  		srcRType := r.rtype(pos)
  2300  
  2301  		// TODO(mdempsky): Always emit ODYNAMICDOTTYPE for uniformity?
  2302  		if typ, ok := typ.(*ir.DynamicType); ok && typ.Op() == ir.ODYNAMICTYPE {
  2303  			assert := ir.NewDynamicTypeAssertExpr(pos, ir.ODYNAMICDOTTYPE, x, typ.RType)
  2304  			assert.SrcRType = srcRType
  2305  			assert.ITab = typ.ITab
  2306  			return typed(typ.Type(), assert)
  2307  		}
  2308  		return typecheck.Expr(ir.NewTypeAssertExpr(pos, x, typ.Type()))
  2309  
  2310  	case exprUnaryOp:
  2311  		op := r.op()
  2312  		pos := r.pos()
  2313  		x := r.expr()
  2314  
  2315  		switch op {
  2316  		case ir.OADDR:
  2317  			return typecheck.Expr(typecheck.NodAddrAt(pos, x))
  2318  		case ir.ODEREF:
  2319  			return typecheck.Expr(ir.NewStarExpr(pos, x))
  2320  		}
  2321  		return typecheck.Expr(ir.NewUnaryExpr(pos, op, x))
  2322  
  2323  	case exprBinaryOp:
  2324  		op := r.op()
  2325  		x := r.expr()
  2326  		pos := r.pos()
  2327  		y := r.expr()
  2328  
  2329  		switch op {
  2330  		case ir.OANDAND, ir.OOROR:
  2331  			return typecheck.Expr(ir.NewLogicalExpr(pos, op, x, y))
  2332  		case ir.OLSH, ir.ORSH:
  2333  			// Untyped rhs of non-constant shift, e.g. x << 1.0.
  2334  			// If we have a constant value, it must be an int >= 0.
  2335  			if ir.IsConstNode(y) {
  2336  				val := constant.ToInt(y.Val())
  2337  				assert(val.Kind() == constant.Int && constant.Sign(val) >= 0)
  2338  			}
  2339  		}
  2340  		return typecheck.Expr(ir.NewBinaryExpr(pos, op, x, y))
  2341  
  2342  	case exprRecv:
  2343  		x := r.expr()
  2344  		pos := r.pos()
  2345  		for i, n := 0, r.Len(); i < n; i++ {
  2346  			x = Implicit(typecheck.DotField(pos, x, r.Len()))
  2347  		}
  2348  		if r.Bool() { // needs deref
  2349  			x = Implicit(Deref(pos, x.Type().Elem(), x))
  2350  		} else if r.Bool() { // needs addr
  2351  			x = Implicit(Addr(pos, x))
  2352  		}
  2353  		return x
  2354  
  2355  	case exprCall:
  2356  		var fun ir.Node
  2357  		var args ir.Nodes
  2358  		if r.Bool() { // method call
  2359  			recv := r.expr()
  2360  			_, method, dictPtr := r.methodExpr()
  2361  
  2362  			if recv.Type().IsInterface() && method.Op() == ir.OMETHEXPR {
  2363  				method := method.(*ir.SelectorExpr)
  2364  
  2365  				// The compiler backend (e.g., devirtualization) handle
  2366  				// OCALLINTER/ODOTINTER better than OCALLFUNC/OMETHEXPR for
  2367  				// interface calls, so we prefer to continue constructing
  2368  				// calls that way where possible.
  2369  				//
  2370  				// There are also corner cases where semantically it's perhaps
  2371  				// significant; e.g., fixedbugs/issue15975.go, #38634, #52025.
  2372  
  2373  				fun = typecheck.XDotMethod(method.Pos(), recv, method.Sel, true)
  2374  			} else {
  2375  				if recv.Type().IsInterface() {
  2376  					// N.B., this happens currently for typeparam/issue51521.go
  2377  					// and typeparam/typeswitch3.go.
  2378  					if base.Flag.LowerM != 0 {
  2379  						base.WarnfAt(method.Pos(), "imprecise interface call")
  2380  					}
  2381  				}
  2382  
  2383  				fun = method
  2384  				args.Append(recv)
  2385  			}
  2386  			if dictPtr != nil {
  2387  				args.Append(dictPtr)
  2388  			}
  2389  		} else if r.Bool() { // call to instanced function
  2390  			pos := r.pos()
  2391  			_, shapedFn, dictPtr := r.funcInst(pos)
  2392  			fun = shapedFn
  2393  			args.Append(dictPtr)
  2394  		} else {
  2395  			fun = r.expr()
  2396  		}
  2397  		pos := r.pos()
  2398  		args.Append(r.multiExpr()...)
  2399  		dots := r.Bool()
  2400  		n := typecheck.Call(pos, fun, args, dots)
  2401  		switch n.Op() {
  2402  		case ir.OAPPEND:
  2403  			n := n.(*ir.CallExpr)
  2404  			n.RType = r.rtype(pos)
  2405  			// For append(a, b...), we don't need the implicit conversion. The typechecker already
  2406  			// ensured that a and b are both slices with the same base type, or []byte and string.
  2407  			if n.IsDDD {
  2408  				if conv, ok := n.Args[1].(*ir.ConvExpr); ok && conv.Op() == ir.OCONVNOP && conv.Implicit() {
  2409  					n.Args[1] = conv.X
  2410  				}
  2411  			}
  2412  		case ir.OCOPY:
  2413  			n := n.(*ir.BinaryExpr)
  2414  			n.RType = r.rtype(pos)
  2415  		case ir.ODELETE:
  2416  			n := n.(*ir.CallExpr)
  2417  			n.RType = r.rtype(pos)
  2418  		case ir.OUNSAFESLICE:
  2419  			n := n.(*ir.BinaryExpr)
  2420  			n.RType = r.rtype(pos)
  2421  		}
  2422  		return n
  2423  
  2424  	case exprMake:
  2425  		pos := r.pos()
  2426  		typ := r.exprType()
  2427  		extra := r.exprs()
  2428  		n := typecheck.Expr(ir.NewCallExpr(pos, ir.OMAKE, nil, append([]ir.Node{typ}, extra...))).(*ir.MakeExpr)
  2429  		n.RType = r.rtype(pos)
  2430  		return n
  2431  
  2432  	case exprNew:
  2433  		pos := r.pos()
  2434  		if r.Bool() {
  2435  			// new(expr) -> tmp := expr; &tmp
  2436  			x := r.expr()
  2437  			x = typecheck.DefaultLit(x, nil) // See TODO in exprConvert case.
  2438  			var init ir.Nodes
  2439  			addr := ir.NewAddrExpr(pos, r.tempCopy(pos, x, &init))
  2440  			addr.SetInit(init)
  2441  			return typecheck.Expr(addr)
  2442  		}
  2443  		// new(T)
  2444  		return typecheck.Expr(ir.NewUnaryExpr(pos, ir.ONEW, r.exprType()))
  2445  
  2446  	case exprSizeof:
  2447  		return ir.NewUintptr(r.pos(), r.typ().Size())
  2448  
  2449  	case exprAlignof:
  2450  		return ir.NewUintptr(r.pos(), r.typ().Alignment())
  2451  
  2452  	case exprOffsetof:
  2453  		pos := r.pos()
  2454  		typ := r.typ()
  2455  		types.CalcSize(typ)
  2456  
  2457  		var offset int64
  2458  		for i := r.Len(); i >= 0; i-- {
  2459  			field := typ.Field(r.Len())
  2460  			offset += field.Offset
  2461  			typ = field.Type
  2462  		}
  2463  
  2464  		return ir.NewUintptr(pos, offset)
  2465  
  2466  	case exprReshape:
  2467  		typ := r.typ()
  2468  		x := r.expr()
  2469  
  2470  		if types.IdenticalStrict(x.Type(), typ) {
  2471  			return x
  2472  		}
  2473  
  2474  		// Comparison expressions are constructed as "untyped bool" still.
  2475  		//
  2476  		// TODO(mdempsky): It should be safe to reshape them here too, but
  2477  		// maybe it's better to construct them with the proper type
  2478  		// instead.
  2479  		if x.Type() == types.UntypedBool && typ.IsBoolean() {
  2480  			return x
  2481  		}
  2482  
  2483  		base.AssertfAt(x.Type().HasShape() || typ.HasShape(), x.Pos(), "%L and %v are not shape types", x, typ)
  2484  		base.AssertfAt(types.Identical(x.Type(), typ), x.Pos(), "%L is not shape-identical to %v", x, typ)
  2485  
  2486  		// We use ir.HasUniquePos here as a check that x only appears once
  2487  		// in the AST, so it's okay for us to call SetType without
  2488  		// breaking any other uses of it.
  2489  		//
  2490  		// Notably, any ONAMEs should already have the exactly right shape
  2491  		// type and been caught by types.IdenticalStrict above.
  2492  		base.AssertfAt(ir.HasUniquePos(x), x.Pos(), "cannot call SetType(%v) on %L", typ, x)
  2493  
  2494  		if base.Debug.Reshape != 0 {
  2495  			base.WarnfAt(x.Pos(), "reshaping %L to %v", x, typ)
  2496  		}
  2497  
  2498  		x.SetType(typ)
  2499  		return x
  2500  
  2501  	case exprConvert:
  2502  		implicit := r.Bool()
  2503  		typ := r.typ()
  2504  		pos := r.pos()
  2505  		typeWord, srcRType := r.convRTTI(pos)
  2506  		dstTypeParam := r.Bool()
  2507  		identical := r.Bool()
  2508  		x := r.expr()
  2509  
  2510  		// TODO(mdempsky): Stop constructing expressions of untyped type.
  2511  		x = typecheck.DefaultLit(x, typ)
  2512  
  2513  		ce := ir.NewConvExpr(pos, ir.OCONV, typ, x)
  2514  		ce.TypeWord, ce.SrcRType = typeWord, srcRType
  2515  		if implicit {
  2516  			ce.SetImplicit(true)
  2517  		}
  2518  		n := typecheck.Expr(ce)
  2519  
  2520  		// Conversions between non-identical, non-empty interfaces always
  2521  		// requires a runtime call, even if they have identical underlying
  2522  		// interfaces. This is because we create separate itab instances
  2523  		// for each unique interface type, not merely each unique
  2524  		// interface shape.
  2525  		//
  2526  		// However, due to shape types, typecheck.Expr might mistakenly
  2527  		// think a conversion between two non-empty interfaces are
  2528  		// identical and set ir.OCONVNOP, instead of ir.OCONVIFACE. To
  2529  		// ensure we update the itab field appropriately, we force it to
  2530  		// ir.OCONVIFACE instead when shape types are involved.
  2531  		//
  2532  		// TODO(mdempsky): Are there other places we might get this wrong?
  2533  		// Should this be moved down into typecheck.{Assign,Convert}op?
  2534  		// This would be a non-issue if itabs were unique for each
  2535  		// *underlying* interface type instead.
  2536  		if !identical {
  2537  			if n, ok := n.(*ir.ConvExpr); ok && n.Op() == ir.OCONVNOP && n.Type().IsInterface() && !n.Type().IsEmptyInterface() && (n.Type().HasShape() || n.X.Type().HasShape()) {
  2538  				n.SetOp(ir.OCONVIFACE)
  2539  			}
  2540  		}
  2541  
  2542  		// spec: "If the type is a type parameter, the constant is converted
  2543  		// into a non-constant value of the type parameter."
  2544  		if dstTypeParam && ir.IsConstNode(n) {
  2545  			// Wrap in an OCONVNOP node to ensure result is non-constant.
  2546  			n = Implicit(ir.NewConvExpr(pos, ir.OCONVNOP, n.Type(), n))
  2547  			n.SetTypecheck(1)
  2548  		}
  2549  		return n
  2550  
  2551  	case exprRuntimeBuiltin:
  2552  		builtin := typecheck.LookupRuntime(r.String())
  2553  		return builtin
  2554  	}
  2555  }
  2556  
  2557  // funcInst reads an instantiated function reference, and returns
  2558  // three (possibly nil) expressions related to it:
  2559  //
  2560  // baseFn is always non-nil: it's either a function of the appropriate
  2561  // type already, or it has an extra dictionary parameter as the first
  2562  // parameter.
  2563  //
  2564  // If dictPtr is non-nil, then it's a dictionary argument that must be
  2565  // passed as the first argument to baseFn.
  2566  //
  2567  // If wrapperFn is non-nil, then it's either the same as baseFn (if
  2568  // dictPtr is nil), or it's semantically equivalent to currying baseFn
  2569  // to pass dictPtr. (wrapperFn is nil when dictPtr is an expression
  2570  // that needs to be computed dynamically.)
  2571  //
  2572  // For callers that are creating a call to the returned function, it's
  2573  // best to emit a call to baseFn, and include dictPtr in the arguments
  2574  // list as appropriate.
  2575  //
  2576  // For callers that want to return the function without invoking it,
  2577  // they may return wrapperFn if it's non-nil; but otherwise, they need
  2578  // to create their own wrapper.
  2579  func (r *reader) funcInst(pos src.XPos) (wrapperFn, baseFn, dictPtr ir.Node) {
  2580  	// Like in methodExpr, I'm pretty sure this isn't needed.
  2581  	var implicits []*types.Type
  2582  	if r.dict != nil {
  2583  		implicits = r.dict.targs
  2584  	}
  2585  
  2586  	if r.Bool() { // dynamic subdictionary
  2587  		idx := r.Len()
  2588  		info := r.dict.subdicts[idx]
  2589  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2590  
  2591  		baseFn = r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2592  
  2593  		// TODO(mdempsky): Is there a more robust way to get the
  2594  		// dictionary pointer type here?
  2595  		dictPtrType := baseFn.Type().Param(0).Type
  2596  		dictPtr = typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, dictPtrType, r.dictWord(pos, r.dict.subdictsOffset()+idx)))
  2597  
  2598  		return
  2599  	}
  2600  
  2601  	info := r.objInfo()
  2602  	explicits := r.p.typListIdx(info.explicits, r.dict)
  2603  
  2604  	wrapperFn = r.p.objIdx(info.idx, implicits, explicits, false).(*ir.Name)
  2605  	baseFn = r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2606  
  2607  	dictName := r.p.objDictName(info.idx, implicits, explicits)
  2608  	dictPtr = typecheck.Expr(ir.NewAddrExpr(pos, dictName))
  2609  
  2610  	return
  2611  }
  2612  
  2613  func (pr *pkgReader) objDictName(idx index, implicits, explicits []*types.Type) *ir.Name {
  2614  	rname := pr.newReader(pkgbits.SectionName, idx, pkgbits.SyncObject1)
  2615  	_, sym := rname.qualifiedIdent()
  2616  	tag := pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
  2617  
  2618  	if tag == pkgbits.ObjStub {
  2619  		assert(!sym.IsBlank())
  2620  		if pri, ok := objReader[sym]; ok {
  2621  			return pri.pr.objDictName(pri.idx, nil, explicits)
  2622  		}
  2623  		base.Fatalf("unresolved stub: %v", sym)
  2624  	}
  2625  
  2626  	dict, err := pr.objDictIdx(sym, idx, implicits, explicits, false)
  2627  	if err != nil {
  2628  		base.Fatalf("%v", err)
  2629  	}
  2630  
  2631  	return pr.dictNameOf(dict)
  2632  }
  2633  
  2634  // curry returns a function literal that calls fun with arg0 and
  2635  // (optionally) arg1, accepting additional arguments to the function
  2636  // literal as necessary to satisfy fun's signature.
  2637  //
  2638  // If nilCheck is true and arg0 is an interface value, then it's
  2639  // checked to be non-nil as an initial step at the point of evaluating
  2640  // the function literal itself.
  2641  func (r *reader) curry(origPos src.XPos, ifaceHack bool, fun ir.Node, arg0, arg1 ir.Node) ir.Node {
  2642  	var captured ir.Nodes
  2643  	captured.Append(fun, arg0)
  2644  	if arg1 != nil {
  2645  		captured.Append(arg1)
  2646  	}
  2647  
  2648  	params, results := syntheticSig(fun.Type())
  2649  	params = params[len(captured)-1:] // skip curried parameters
  2650  	typ := types.NewSignature(nil, params, results)
  2651  
  2652  	addBody := func(pos src.XPos, r *reader, captured []ir.Node) {
  2653  		fun := captured[0]
  2654  
  2655  		var args ir.Nodes
  2656  		args.Append(captured[1:]...)
  2657  		args.Append(r.syntheticArgs()...)
  2658  
  2659  		r.syntheticTailCall(pos, fun, args)
  2660  	}
  2661  
  2662  	return r.syntheticClosure(origPos, typ, ifaceHack, captured, addBody)
  2663  }
  2664  
  2665  // methodExprWrap returns a function literal that changes method's
  2666  // first parameter's type to recv, and uses implicits/deref/addr to
  2667  // select the appropriate receiver parameter to pass to method.
  2668  func (r *reader) methodExprWrap(origPos src.XPos, recv *types.Type, implicits []int, deref, addr bool, method, dictPtr ir.Node) ir.Node {
  2669  	var captured ir.Nodes
  2670  	captured.Append(method)
  2671  
  2672  	params, results := syntheticSig(method.Type())
  2673  
  2674  	// Change first parameter to recv.
  2675  	params[0].Type = recv
  2676  
  2677  	// If we have a dictionary pointer argument to pass, then omit the
  2678  	// underlying method expression's dictionary parameter from the
  2679  	// returned signature too.
  2680  	if dictPtr != nil {
  2681  		captured.Append(dictPtr)
  2682  		params = append(params[:1], params[2:]...)
  2683  	}
  2684  
  2685  	typ := types.NewSignature(nil, params, results)
  2686  
  2687  	addBody := func(pos src.XPos, r *reader, captured []ir.Node) {
  2688  		fn := captured[0]
  2689  		args := r.syntheticArgs()
  2690  
  2691  		// Rewrite first argument based on implicits/deref/addr.
  2692  		{
  2693  			arg := args[0]
  2694  			for _, ix := range implicits {
  2695  				arg = Implicit(typecheck.DotField(pos, arg, ix))
  2696  			}
  2697  			if deref {
  2698  				arg = Implicit(Deref(pos, arg.Type().Elem(), arg))
  2699  			} else if addr {
  2700  				arg = Implicit(Addr(pos, arg))
  2701  			}
  2702  			args[0] = arg
  2703  		}
  2704  
  2705  		// Insert dictionary argument, if provided.
  2706  		if dictPtr != nil {
  2707  			newArgs := make([]ir.Node, len(args)+1)
  2708  			newArgs[0] = args[0]
  2709  			newArgs[1] = captured[1]
  2710  			copy(newArgs[2:], args[1:])
  2711  			args = newArgs
  2712  		}
  2713  
  2714  		r.syntheticTailCall(pos, fn, args)
  2715  	}
  2716  
  2717  	return r.syntheticClosure(origPos, typ, false, captured, addBody)
  2718  }
  2719  
  2720  // syntheticClosure constructs a synthetic function literal for
  2721  // currying dictionary arguments. origPos is the position used for the
  2722  // closure, which must be a non-inlined position. typ is the function
  2723  // literal's signature type.
  2724  //
  2725  // captures is a list of expressions that need to be evaluated at the
  2726  // point of function literal evaluation and captured by the function
  2727  // literal. If ifaceHack is true and captures[1] is an interface type,
  2728  // it's checked to be non-nil after evaluation.
  2729  //
  2730  // addBody is a callback function to populate the function body. The
  2731  // list of captured values passed back has the captured variables for
  2732  // use within the function literal, corresponding to the expressions
  2733  // in captures.
  2734  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 {
  2735  	// isSafe reports whether n is an expression that we can safely
  2736  	// defer to evaluating inside the closure instead, to avoid storing
  2737  	// them into the closure.
  2738  	//
  2739  	// In practice this is always (and only) the wrappee function.
  2740  	isSafe := func(n ir.Node) bool {
  2741  		if n.Op() == ir.ONAME && n.(*ir.Name).Class == ir.PFUNC {
  2742  			return true
  2743  		}
  2744  		if n.Op() == ir.OMETHEXPR {
  2745  			return true
  2746  		}
  2747  
  2748  		return false
  2749  	}
  2750  
  2751  	fn := r.inlClosureFunc(origPos, typ, ir.OCLOSURE)
  2752  	fn.SetWrapper(true)
  2753  
  2754  	clo := fn.OClosure
  2755  	inlPos := clo.Pos()
  2756  
  2757  	var init ir.Nodes
  2758  	for i, n := range captures {
  2759  		if isSafe(n) {
  2760  			continue // skip capture; can reference directly
  2761  		}
  2762  
  2763  		tmp := r.tempCopy(inlPos, n, &init)
  2764  		ir.NewClosureVar(origPos, fn, tmp)
  2765  
  2766  		// We need to nil check interface receivers at the point of method
  2767  		// value evaluation, ugh.
  2768  		if ifaceHack && i == 1 && n.Type().IsInterface() {
  2769  			check := ir.NewUnaryExpr(inlPos, ir.OCHECKNIL, ir.NewUnaryExpr(inlPos, ir.OITAB, tmp))
  2770  			init.Append(typecheck.Stmt(check))
  2771  		}
  2772  	}
  2773  
  2774  	pri := pkgReaderIndex{synthetic: func(pos src.XPos, r *reader) {
  2775  		captured := make([]ir.Node, len(captures))
  2776  		next := 0
  2777  		for i, n := range captures {
  2778  			if isSafe(n) {
  2779  				captured[i] = n
  2780  			} else {
  2781  				captured[i] = r.closureVars[next]
  2782  				next++
  2783  			}
  2784  		}
  2785  		assert(next == len(r.closureVars))
  2786  
  2787  		addBody(origPos, r, captured)
  2788  	}}
  2789  	bodyReader[fn] = pri
  2790  	pri.funcBody(fn)
  2791  
  2792  	return ir.InitExpr(init, clo)
  2793  }
  2794  
  2795  // syntheticSig duplicates and returns the params and results lists
  2796  // for sig, but renaming anonymous parameters so they can be assigned
  2797  // ir.Names.
  2798  func syntheticSig(sig *types.Type) (params, results []*types.Field) {
  2799  	clone := func(params []*types.Field) []*types.Field {
  2800  		res := make([]*types.Field, len(params))
  2801  		for i, param := range params {
  2802  			// TODO(mdempsky): It would be nice to preserve the original
  2803  			// parameter positions here instead, but at least
  2804  			// typecheck.NewMethodType replaces them with base.Pos, making
  2805  			// them useless. Worse, the positions copied from base.Pos may
  2806  			// have inlining contexts, which we definitely don't want here
  2807  			// (e.g., #54625).
  2808  			res[i] = types.NewField(base.AutogeneratedPos, param.Sym, param.Type)
  2809  			res[i].SetIsDDD(param.IsDDD())
  2810  		}
  2811  		return res
  2812  	}
  2813  
  2814  	return clone(sig.Params()), clone(sig.Results())
  2815  }
  2816  
  2817  func (r *reader) optExpr() ir.Node {
  2818  	if r.Bool() {
  2819  		return r.expr()
  2820  	}
  2821  	return nil
  2822  }
  2823  
  2824  // methodExpr reads a method expression reference, and returns three
  2825  // (possibly nil) expressions related to it:
  2826  //
  2827  // baseFn is always non-nil: it's either a function of the appropriate
  2828  // type already, or it has an extra dictionary parameter as the second
  2829  // parameter (i.e., immediately after the promoted receiver
  2830  // parameter).
  2831  //
  2832  // If dictPtr is non-nil, then it's a dictionary argument that must be
  2833  // passed as the second argument to baseFn.
  2834  //
  2835  // If wrapperFn is non-nil, then it's either the same as baseFn (if
  2836  // dictPtr is nil), or it's semantically equivalent to currying baseFn
  2837  // to pass dictPtr. (wrapperFn is nil when dictPtr is an expression
  2838  // that needs to be computed dynamically.)
  2839  //
  2840  // For callers that are creating a call to the returned method, it's
  2841  // best to emit a call to baseFn, and include dictPtr in the arguments
  2842  // list as appropriate.
  2843  //
  2844  // For callers that want to return a method expression without
  2845  // invoking it, they may return wrapperFn if it's non-nil; but
  2846  // otherwise, they need to create their own wrapper.
  2847  func (r *reader) methodExpr() (wrapperFn, baseFn, dictPtr ir.Node) {
  2848  	recv := r.typ()
  2849  	sig0 := r.typ()
  2850  	pos := r.pos()
  2851  	sym := r.selector()
  2852  
  2853  	// Signature type to return (i.e., recv prepended to the method's
  2854  	// normal parameters list).
  2855  	sig := typecheck.NewMethodType(sig0, recv)
  2856  
  2857  	if r.Bool() { // type parameter method expression
  2858  		idx := r.Len()
  2859  		word := r.dictWord(pos, r.dict.typeParamMethodExprsOffset()+idx)
  2860  
  2861  		// TODO(mdempsky): If the type parameter was instantiated with an
  2862  		// interface type (i.e., embed.IsInterface()), then we could
  2863  		// return the OMETHEXPR instead and save an indirection.
  2864  
  2865  		// We wrote the method expression's entry point PC into the
  2866  		// dictionary, but for Go `func` values we need to return a
  2867  		// closure (i.e., pointer to a structure with the PC as the first
  2868  		// field). Because method expressions don't have any closure
  2869  		// variables, we pun the dictionary entry as the closure struct.
  2870  		fn := typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, sig, ir.NewAddrExpr(pos, word)))
  2871  		return fn, fn, nil
  2872  	}
  2873  
  2874  	// TODO(mdempsky): I'm pretty sure this isn't needed: implicits is
  2875  	// only relevant to locally defined types, but they can't have
  2876  	// (non-promoted) methods.
  2877  	var implicits []*types.Type
  2878  	if r.dict != nil {
  2879  		implicits = r.dict.targs
  2880  	}
  2881  
  2882  	if r.Bool() { // dynamic subdictionary
  2883  		idx := r.Len()
  2884  		info := r.dict.subdicts[idx]
  2885  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2886  
  2887  		shapedObj := r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2888  		shapedFn := shapedMethodExpr(pos, shapedObj, sym)
  2889  
  2890  		// TODO(mdempsky): Is there a more robust way to get the
  2891  		// dictionary pointer type here?
  2892  		dictPtrType := shapedFn.Type().Param(1).Type
  2893  		dictPtr := typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, dictPtrType, r.dictWord(pos, r.dict.subdictsOffset()+idx)))
  2894  
  2895  		return nil, shapedFn, dictPtr
  2896  	}
  2897  
  2898  	if r.Bool() { // static dictionary
  2899  		info := r.objInfo()
  2900  		explicits := r.p.typListIdx(info.explicits, r.dict)
  2901  
  2902  		shapedObj := r.p.objIdx(info.idx, implicits, explicits, true).(*ir.Name)
  2903  		shapedFn := shapedMethodExpr(pos, shapedObj, sym)
  2904  
  2905  		dict := r.p.objDictName(info.idx, implicits, explicits)
  2906  		dictPtr := typecheck.Expr(ir.NewAddrExpr(pos, dict))
  2907  
  2908  		// Check that dictPtr matches shapedFn's dictionary parameter.
  2909  		if !types.Identical(dictPtr.Type(), shapedFn.Type().Param(1).Type) {
  2910  			base.FatalfAt(pos, "dict %L, but shaped method %L", dict, shapedFn)
  2911  		}
  2912  
  2913  		// For statically known instantiations, we can take advantage of
  2914  		// the stenciled wrapper.
  2915  		base.AssertfAt(!recv.HasShape(), pos, "shaped receiver %v", recv)
  2916  		wrapperFn := typecheck.NewMethodExpr(pos, recv, sym)
  2917  		base.AssertfAt(types.Identical(sig, wrapperFn.Type()), pos, "wrapper %L does not have type %v", wrapperFn, sig)
  2918  
  2919  		return wrapperFn, shapedFn, dictPtr
  2920  	}
  2921  
  2922  	// Simple method expression; no dictionary needed.
  2923  	base.AssertfAt(!recv.HasShape() || recv.IsInterface(), pos, "shaped receiver %v", recv)
  2924  	fn := typecheck.NewMethodExpr(pos, recv, sym)
  2925  	return fn, fn, nil
  2926  }
  2927  
  2928  // shapedMethodExpr returns the specified method on the given shaped
  2929  // type.
  2930  func shapedMethodExpr(pos src.XPos, obj *ir.Name, sym *types.Sym) *ir.SelectorExpr {
  2931  	assert(obj.Op() == ir.OTYPE)
  2932  
  2933  	typ := obj.Type()
  2934  	assert(typ.HasShape())
  2935  
  2936  	method := func() *types.Field {
  2937  		for _, method := range typ.Methods() {
  2938  			if method.Sym == sym {
  2939  				return method
  2940  			}
  2941  		}
  2942  
  2943  		base.FatalfAt(pos, "failed to find method %v in shaped type %v", sym, typ)
  2944  		panic("unreachable")
  2945  	}()
  2946  
  2947  	// Construct an OMETHEXPR node.
  2948  	recv := method.Type.Recv().Type
  2949  	return typecheck.NewMethodExpr(pos, recv, sym)
  2950  }
  2951  
  2952  func (r *reader) multiExpr() []ir.Node {
  2953  	r.Sync(pkgbits.SyncMultiExpr)
  2954  
  2955  	if r.Bool() { // N:1
  2956  		pos := r.pos()
  2957  		expr := r.expr()
  2958  
  2959  		results := make([]ir.Node, r.Len())
  2960  		as := ir.NewAssignListStmt(pos, ir.OAS2, nil, []ir.Node{expr})
  2961  		as.Def = true
  2962  		for i := range results {
  2963  			tmp := r.temp(pos, r.typ())
  2964  			tmp.Defn = as
  2965  			as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
  2966  			as.Lhs.Append(tmp)
  2967  
  2968  			res := ir.Node(tmp)
  2969  			if r.Bool() {
  2970  				n := ir.NewConvExpr(pos, ir.OCONV, r.typ(), res)
  2971  				n.TypeWord, n.SrcRType = r.convRTTI(pos)
  2972  				n.SetImplicit(true)
  2973  				res = typecheck.Expr(n)
  2974  			}
  2975  			results[i] = res
  2976  		}
  2977  
  2978  		// TODO(mdempsky): Could use ir.InlinedCallExpr instead?
  2979  		results[0] = ir.InitExpr([]ir.Node{typecheck.Stmt(as)}, results[0])
  2980  		return results
  2981  	}
  2982  
  2983  	// N:N
  2984  	exprs := make([]ir.Node, r.Len())
  2985  	if len(exprs) == 0 {
  2986  		return nil
  2987  	}
  2988  	for i := range exprs {
  2989  		exprs[i] = r.expr()
  2990  	}
  2991  	return exprs
  2992  }
  2993  
  2994  // temp returns a new autotemp of the specified type.
  2995  func (r *reader) temp(pos src.XPos, typ *types.Type) *ir.Name {
  2996  	return typecheck.TempAt(pos, r.curfn, typ)
  2997  }
  2998  
  2999  // tempCopy declares and returns a new autotemp initialized to the
  3000  // value of expr.
  3001  func (r *reader) tempCopy(pos src.XPos, expr ir.Node, init *ir.Nodes) *ir.Name {
  3002  	tmp := r.temp(pos, expr.Type())
  3003  
  3004  	init.Append(typecheck.Stmt(ir.NewDecl(pos, ir.ODCL, tmp)))
  3005  
  3006  	assign := ir.NewAssignStmt(pos, tmp, expr)
  3007  	assign.Def = true
  3008  	init.Append(typecheck.Stmt(ir.NewAssignStmt(pos, tmp, expr)))
  3009  
  3010  	tmp.Defn = assign
  3011  
  3012  	return tmp
  3013  }
  3014  
  3015  func (r *reader) compLit() ir.Node {
  3016  	r.Sync(pkgbits.SyncCompLit)
  3017  	pos := r.pos()
  3018  	typ0 := r.typ()
  3019  
  3020  	typ := typ0
  3021  	if typ.IsPtr() {
  3022  		typ = typ.Elem()
  3023  	}
  3024  	if typ.Kind() == types.TFORW {
  3025  		base.FatalfAt(pos, "unresolved composite literal type: %v", typ)
  3026  	}
  3027  	var rtype ir.Node
  3028  	if typ.IsMap() {
  3029  		rtype = r.rtype(pos)
  3030  	}
  3031  	isStruct := typ.Kind() == types.TSTRUCT
  3032  
  3033  	elems := make([]ir.Node, r.Len())
  3034  	for i := range elems {
  3035  		elemp := &elems[i]
  3036  
  3037  		if isStruct {
  3038  			sk := ir.NewStructKeyExpr(r.pos(), typ.Field(r.Len()), nil)
  3039  			*elemp, elemp = sk, &sk.Value
  3040  		} else if r.Bool() {
  3041  			kv := ir.NewKeyExpr(r.pos(), r.expr(), nil)
  3042  			*elemp, elemp = kv, &kv.Value
  3043  		}
  3044  
  3045  		*elemp = r.expr()
  3046  	}
  3047  
  3048  	lit := typecheck.Expr(ir.NewCompLitExpr(pos, ir.OCOMPLIT, typ, elems))
  3049  	if rtype != nil {
  3050  		lit := lit.(*ir.CompLitExpr)
  3051  		lit.RType = rtype
  3052  	}
  3053  	if typ0.IsPtr() {
  3054  		lit = typecheck.Expr(typecheck.NodAddrAt(pos, lit))
  3055  		lit.SetType(typ0)
  3056  	}
  3057  	return lit
  3058  }
  3059  
  3060  func (r *reader) funcLit() ir.Node {
  3061  	r.Sync(pkgbits.SyncFuncLit)
  3062  
  3063  	// The underlying function declaration (including its parameters'
  3064  	// positions, if any) need to remain the original, uninlined
  3065  	// positions. This is because we track inlining-context on nodes so
  3066  	// we can synthesize the extra implied stack frames dynamically when
  3067  	// generating tracebacks, whereas those stack frames don't make
  3068  	// sense *within* the function literal. (Any necessary inlining
  3069  	// adjustments will have been applied to the call expression
  3070  	// instead.)
  3071  	//
  3072  	// This is subtle, and getting it wrong leads to cycles in the
  3073  	// inlining tree, which lead to infinite loops during stack
  3074  	// unwinding (#46234, #54625).
  3075  	//
  3076  	// Note that we *do* want the inline-adjusted position for the
  3077  	// OCLOSURE node, because that position represents where any heap
  3078  	// allocation of the closure is credited (#49171).
  3079  	r.suppressInlPos++
  3080  	origPos := r.pos()
  3081  	sig := r.signature(nil)
  3082  	r.suppressInlPos--
  3083  	why := ir.OCLOSURE
  3084  	if r.Bool() {
  3085  		why = ir.ORANGE
  3086  	}
  3087  
  3088  	fn := r.inlClosureFunc(origPos, sig, why)
  3089  
  3090  	fn.ClosureVars = make([]*ir.Name, 0, r.Len())
  3091  	for len(fn.ClosureVars) < cap(fn.ClosureVars) {
  3092  		// TODO(mdempsky): I think these should be original positions too
  3093  		// (i.e., not inline-adjusted).
  3094  		ir.NewClosureVar(r.pos(), fn, r.useLocal())
  3095  	}
  3096  	if param := r.dictParam; param != nil {
  3097  		// If we have a dictionary parameter, capture it too. For
  3098  		// simplicity, we capture it last and unconditionally.
  3099  		ir.NewClosureVar(param.Pos(), fn, param)
  3100  	}
  3101  
  3102  	r.addBody(fn, nil)
  3103  
  3104  	return fn.OClosure
  3105  }
  3106  
  3107  // inlClosureFunc constructs a new closure function, but correctly
  3108  // handles inlining.
  3109  func (r *reader) inlClosureFunc(origPos src.XPos, sig *types.Type, why ir.Op) *ir.Func {
  3110  	curfn := r.inlCaller
  3111  	if curfn == nil {
  3112  		curfn = r.curfn
  3113  	}
  3114  
  3115  	// TODO(mdempsky): Remove hard-coding of typecheck.Target.
  3116  	return ir.NewClosureFunc(origPos, r.inlPos(origPos), why, sig, curfn, typecheck.Target)
  3117  }
  3118  
  3119  func (r *reader) exprList() []ir.Node {
  3120  	r.Sync(pkgbits.SyncExprList)
  3121  	return r.exprs()
  3122  }
  3123  
  3124  func (r *reader) exprs() []ir.Node {
  3125  	r.Sync(pkgbits.SyncExprs)
  3126  	nodes := make([]ir.Node, r.Len())
  3127  	if len(nodes) == 0 {
  3128  		return nil // TODO(mdempsky): Unclear if this matters.
  3129  	}
  3130  	for i := range nodes {
  3131  		nodes[i] = r.expr()
  3132  	}
  3133  	return nodes
  3134  }
  3135  
  3136  // dictWord returns an expression to return the specified
  3137  // uintptr-typed word from the dictionary parameter.
  3138  func (r *reader) dictWord(pos src.XPos, idx int) ir.Node {
  3139  	base.AssertfAt(r.dictParam != nil, pos, "expected dictParam in %v", r.curfn)
  3140  	return typecheck.Expr(ir.NewIndexExpr(pos, r.dictParam, ir.NewInt(pos, int64(idx))))
  3141  }
  3142  
  3143  // rttiWord is like dictWord, but converts it to *byte (the type used
  3144  // internally to represent *runtime._type and *runtime.itab).
  3145  func (r *reader) rttiWord(pos src.XPos, idx int) ir.Node {
  3146  	return typecheck.Expr(ir.NewConvExpr(pos, ir.OCONVNOP, types.NewPtr(types.Types[types.TUINT8]), r.dictWord(pos, idx)))
  3147  }
  3148  
  3149  // rtype reads a type reference from the element bitstream, and
  3150  // returns an expression of type *runtime._type representing that
  3151  // type.
  3152  func (r *reader) rtype(pos src.XPos) ir.Node {
  3153  	_, rtype := r.rtype0(pos)
  3154  	return rtype
  3155  }
  3156  
  3157  func (r *reader) rtype0(pos src.XPos) (typ *types.Type, rtype ir.Node) {
  3158  	r.Sync(pkgbits.SyncRType)
  3159  	if r.Bool() { // derived type
  3160  		idx := r.Len()
  3161  		info := r.dict.rtypes[idx]
  3162  		typ = r.p.typIdx(info, r.dict, true)
  3163  		rtype = r.rttiWord(pos, r.dict.rtypesOffset()+idx)
  3164  		return
  3165  	}
  3166  
  3167  	typ = r.typ()
  3168  	rtype = reflectdata.TypePtrAt(pos, typ)
  3169  	return
  3170  }
  3171  
  3172  // varDictIndex populates name.DictIndex if name is a derived type.
  3173  func (r *reader) varDictIndex(name *ir.Name) {
  3174  	if r.Bool() {
  3175  		idx := 1 + r.dict.rtypesOffset() + r.Len()
  3176  		if int(uint16(idx)) != idx {
  3177  			base.FatalfAt(name.Pos(), "DictIndex overflow for %v: %v", name, idx)
  3178  		}
  3179  		name.DictIndex = uint16(idx)
  3180  	}
  3181  }
  3182  
  3183  // itab returns a (typ, iface) pair of types.
  3184  //
  3185  // typRType and ifaceRType are expressions that evaluate to the
  3186  // *runtime._type for typ and iface, respectively.
  3187  //
  3188  // If typ is a concrete type and iface is a non-empty interface type,
  3189  // then itab is an expression that evaluates to the *runtime.itab for
  3190  // the pair. Otherwise, itab is nil.
  3191  func (r *reader) itab(pos src.XPos) (typ *types.Type, typRType ir.Node, iface *types.Type, ifaceRType ir.Node, itab ir.Node) {
  3192  	typ, typRType = r.rtype0(pos)
  3193  	iface, ifaceRType = r.rtype0(pos)
  3194  
  3195  	idx := -1
  3196  	if r.Bool() {
  3197  		idx = r.Len()
  3198  	}
  3199  
  3200  	if !typ.IsInterface() && iface.IsInterface() && !iface.IsEmptyInterface() {
  3201  		if idx >= 0 {
  3202  			itab = r.rttiWord(pos, r.dict.itabsOffset()+idx)
  3203  		} else {
  3204  			base.AssertfAt(!typ.HasShape(), pos, "%v is a shape type", typ)
  3205  			base.AssertfAt(!iface.HasShape(), pos, "%v is a shape type", iface)
  3206  
  3207  			lsym := reflectdata.ITabLsym(typ, iface)
  3208  			itab = typecheck.LinksymAddr(pos, lsym, types.Types[types.TUINT8])
  3209  		}
  3210  	}
  3211  
  3212  	return
  3213  }
  3214  
  3215  // convRTTI returns expressions appropriate for populating an
  3216  // ir.ConvExpr's TypeWord and SrcRType fields, respectively.
  3217  func (r *reader) convRTTI(pos src.XPos) (typeWord, srcRType ir.Node) {
  3218  	r.Sync(pkgbits.SyncConvRTTI)
  3219  	src, srcRType0, dst, dstRType, itab := r.itab(pos)
  3220  	if !dst.IsInterface() {
  3221  		return
  3222  	}
  3223  
  3224  	// See reflectdata.ConvIfaceTypeWord.
  3225  	switch {
  3226  	case dst.IsEmptyInterface():
  3227  		if !src.IsInterface() {
  3228  			typeWord = srcRType0 // direct eface construction
  3229  		}
  3230  	case !src.IsInterface():
  3231  		typeWord = itab // direct iface construction
  3232  	default:
  3233  		typeWord = dstRType // convI2I
  3234  	}
  3235  
  3236  	// See reflectdata.ConvIfaceSrcRType.
  3237  	if !src.IsInterface() {
  3238  		srcRType = srcRType0
  3239  	}
  3240  
  3241  	return
  3242  }
  3243  
  3244  func (r *reader) exprType() ir.Node {
  3245  	r.Sync(pkgbits.SyncExprType)
  3246  	pos := r.pos()
  3247  
  3248  	var typ *types.Type
  3249  	var rtype, itab ir.Node
  3250  
  3251  	if r.Bool() {
  3252  		// non-empty interface
  3253  		typ, rtype, _, _, itab = r.itab(pos)
  3254  		if !typ.IsInterface() {
  3255  			rtype = nil // TODO(mdempsky): Leave set?
  3256  		}
  3257  	} else {
  3258  		typ, rtype = r.rtype0(pos)
  3259  
  3260  		if !r.Bool() { // not derived
  3261  			return ir.TypeNode(typ)
  3262  		}
  3263  	}
  3264  
  3265  	dt := ir.NewDynamicType(pos, rtype)
  3266  	dt.ITab = itab
  3267  	dt = typed(typ, dt).(*ir.DynamicType)
  3268  	if st := dt.ToStatic(); st != nil {
  3269  		return st
  3270  	}
  3271  	return dt
  3272  }
  3273  
  3274  func (r *reader) op() ir.Op {
  3275  	r.Sync(pkgbits.SyncOp)
  3276  	return ir.Op(r.Len())
  3277  }
  3278  
  3279  // @@@ Package initialization
  3280  
  3281  func (r *reader) pkgInit(self *types.Pkg, target *ir.Package) {
  3282  	cgoPragmas := make([][]string, r.Len())
  3283  	for i := range cgoPragmas {
  3284  		cgoPragmas[i] = r.Strings()
  3285  	}
  3286  	target.CgoPragmas = cgoPragmas
  3287  
  3288  	r.pkgInitOrder(target)
  3289  
  3290  	r.pkgDecls(target)
  3291  
  3292  	r.Sync(pkgbits.SyncEOF)
  3293  }
  3294  
  3295  // pkgInitOrder creates a synthetic init function to handle any
  3296  // package-scope initialization statements.
  3297  func (r *reader) pkgInitOrder(target *ir.Package) {
  3298  	initOrder := make([]ir.Node, r.Len())
  3299  	if len(initOrder) == 0 {
  3300  		return
  3301  	}
  3302  
  3303  	// Make a function that contains all the initialization statements.
  3304  	pos := base.AutogeneratedPos
  3305  	base.Pos = pos
  3306  
  3307  	fn := ir.NewFunc(pos, pos, typecheck.Lookup("init"), types.NewSignature(nil, nil, nil))
  3308  	fn.SetIsPackageInit(true)
  3309  	fn.SetInlinabilityChecked(true) // suppress useless "can inline" diagnostics
  3310  
  3311  	typecheck.DeclFunc(fn)
  3312  	r.curfn = fn
  3313  
  3314  	for i := range initOrder {
  3315  		lhs := make([]ir.Node, r.Len())
  3316  		for j := range lhs {
  3317  			lhs[j] = r.obj()
  3318  		}
  3319  		rhs := r.expr()
  3320  		pos := lhs[0].Pos()
  3321  
  3322  		var as ir.Node
  3323  		if len(lhs) == 1 {
  3324  			as = typecheck.Stmt(ir.NewAssignStmt(pos, lhs[0], rhs))
  3325  		} else {
  3326  			as = typecheck.Stmt(ir.NewAssignListStmt(pos, ir.OAS2, lhs, []ir.Node{rhs}))
  3327  		}
  3328  
  3329  		for _, v := range lhs {
  3330  			v.(*ir.Name).Defn = as
  3331  		}
  3332  
  3333  		initOrder[i] = as
  3334  	}
  3335  
  3336  	fn.Body = initOrder
  3337  
  3338  	typecheck.FinishFuncBody()
  3339  	r.curfn = nil
  3340  	r.locals = nil
  3341  
  3342  	// Outline (if legal/profitable) global map inits.
  3343  	staticinit.OutlineMapInits(fn)
  3344  
  3345  	// Split large init function.
  3346  	staticinit.SplitLargeInit(fn)
  3347  
  3348  	target.Inits = append(target.Inits, fn)
  3349  }
  3350  
  3351  func (r *reader) pkgDecls(target *ir.Package) {
  3352  	r.Sync(pkgbits.SyncDecls)
  3353  	for {
  3354  		switch code := codeDecl(r.Code(pkgbits.SyncDecl)); code {
  3355  		default:
  3356  			panic(fmt.Sprintf("unhandled decl: %v", code))
  3357  
  3358  		case declEnd:
  3359  			return
  3360  
  3361  		case declFunc:
  3362  			names := r.pkgObjs(target)
  3363  			assert(len(names) == 1)
  3364  			target.Funcs = append(target.Funcs, names[0].Func)
  3365  
  3366  		case declMethod:
  3367  			typ := r.typ()
  3368  			sym := r.selector()
  3369  
  3370  			method := typecheck.Lookdot1(nil, sym, typ, typ.Methods(), 0)
  3371  			target.Funcs = append(target.Funcs, method.Nname.(*ir.Name).Func)
  3372  
  3373  		case declVar:
  3374  			names := r.pkgObjs(target)
  3375  
  3376  			if n := r.Len(); n > 0 {
  3377  				assert(len(names) == 1)
  3378  				embeds := make([]ir.Embed, n)
  3379  				for i := range embeds {
  3380  					embeds[i] = ir.Embed{Pos: r.pos(), Patterns: r.Strings()}
  3381  				}
  3382  				names[0].Embed = &embeds
  3383  				target.Embeds = append(target.Embeds, names[0])
  3384  			}
  3385  
  3386  		case declOther:
  3387  			r.pkgObjs(target)
  3388  		}
  3389  	}
  3390  }
  3391  
  3392  func (r *reader) pkgObjs(target *ir.Package) []*ir.Name {
  3393  	r.Sync(pkgbits.SyncDeclNames)
  3394  	nodes := make([]*ir.Name, r.Len())
  3395  	for i := range nodes {
  3396  		r.Sync(pkgbits.SyncDeclName)
  3397  
  3398  		name := r.obj().(*ir.Name)
  3399  		nodes[i] = name
  3400  
  3401  		sym := name.Sym()
  3402  		if sym.IsBlank() {
  3403  			continue
  3404  		}
  3405  
  3406  		switch name.Class {
  3407  		default:
  3408  			base.FatalfAt(name.Pos(), "unexpected class: %v", name.Class)
  3409  
  3410  		case ir.PEXTERN:
  3411  			target.Externs = append(target.Externs, name)
  3412  
  3413  		case ir.PFUNC:
  3414  			assert(name.Type().Recv() == nil)
  3415  
  3416  			// TODO(mdempsky): Cleaner way to recognize init?
  3417  			if strings.HasPrefix(sym.Name, "init.") {
  3418  				target.Inits = append(target.Inits, name.Func)
  3419  			}
  3420  		}
  3421  
  3422  		if base.Ctxt.Flag_dynlink && types.LocalPkg.Name == "main" && types.IsExported(sym.Name) && name.Op() == ir.ONAME {
  3423  			assert(!sym.OnExportList())
  3424  			target.PluginExports = append(target.PluginExports, name)
  3425  			sym.SetOnExportList(true)
  3426  		}
  3427  
  3428  		if base.Flag.AsmHdr != "" && (name.Op() == ir.OLITERAL || name.Op() == ir.OTYPE) {
  3429  			assert(!sym.Asm())
  3430  			target.AsmHdrDecls = append(target.AsmHdrDecls, name)
  3431  			sym.SetAsm(true)
  3432  		}
  3433  	}
  3434  
  3435  	return nodes
  3436  }
  3437  
  3438  // @@@ Inlining
  3439  
  3440  // unifiedHaveInlineBody reports whether we have the function body for
  3441  // fn, so we can inline it.
  3442  func unifiedHaveInlineBody(fn *ir.Func) bool {
  3443  	if fn.Inl == nil {
  3444  		return false
  3445  	}
  3446  
  3447  	_, ok := bodyReaderFor(fn)
  3448  	return ok
  3449  }
  3450  
  3451  var inlgen = 0
  3452  
  3453  // unifiedInlineCall implements inline.NewInline by re-reading the function
  3454  // body from its Unified IR export data.
  3455  func unifiedInlineCall(callerfn *ir.Func, call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExpr {
  3456  	pri, ok := bodyReaderFor(fn)
  3457  	if !ok {
  3458  		base.FatalfAt(call.Pos(), "cannot inline call to %v: missing inline body", fn)
  3459  	}
  3460  
  3461  	if !fn.Inl.HaveDcl {
  3462  		expandInline(fn, pri)
  3463  	}
  3464  
  3465  	r := pri.asReader(pkgbits.SectionBody, pkgbits.SyncFuncBody)
  3466  
  3467  	tmpfn := ir.NewFunc(fn.Pos(), fn.Nname.Pos(), callerfn.Sym(), fn.Type())
  3468  
  3469  	r.curfn = tmpfn
  3470  
  3471  	r.inlCaller = callerfn
  3472  	r.inlCall = call
  3473  	r.inlFunc = fn
  3474  	r.inlTreeIndex = inlIndex
  3475  	r.inlPosBases = make(map[*src.PosBase]*src.PosBase)
  3476  	r.funarghack = true
  3477  
  3478  	r.closureVars = make([]*ir.Name, len(r.inlFunc.ClosureVars))
  3479  	for i, cv := range r.inlFunc.ClosureVars {
  3480  		// TODO(mdempsky): It should be possible to support this case, but
  3481  		// for now we rely on the inliner avoiding it.
  3482  		if cv.Outer.Curfn != callerfn {
  3483  			base.FatalfAt(call.Pos(), "inlining closure call across frames")
  3484  		}
  3485  		r.closureVars[i] = cv.Outer
  3486  	}
  3487  	if len(r.closureVars) != 0 && r.hasTypeParams() {
  3488  		r.dictParam = r.closureVars[len(r.closureVars)-1] // dictParam is last; see reader.funcLit
  3489  	}
  3490  
  3491  	r.declareParams()
  3492  
  3493  	var inlvars, retvars []*ir.Name
  3494  	{
  3495  		sig := r.curfn.Type()
  3496  		endParams := sig.NumRecvs() + sig.NumParams()
  3497  		endResults := endParams + sig.NumResults()
  3498  
  3499  		inlvars = r.curfn.Dcl[:endParams]
  3500  		retvars = r.curfn.Dcl[endParams:endResults]
  3501  	}
  3502  
  3503  	r.delayResults = fn.Inl.CanDelayResults
  3504  
  3505  	r.retlabel = typecheck.AutoLabel(".i")
  3506  	inlgen++
  3507  
  3508  	init := ir.TakeInit(call)
  3509  
  3510  	// For normal function calls, the function callee expression
  3511  	// may contain side effects. Make sure to preserve these,
  3512  	// if necessary (#42703).
  3513  	if call.Op() == ir.OCALLFUNC {
  3514  		inline.CalleeEffects(&init, call.Fun)
  3515  	}
  3516  
  3517  	var args ir.Nodes
  3518  	if call.Op() == ir.OCALLMETH {
  3519  		base.FatalfAt(call.Pos(), "OCALLMETH missed by typecheck")
  3520  	}
  3521  	args.Append(call.Args...)
  3522  
  3523  	// Create assignment to declare and initialize inlvars.
  3524  	as2 := ir.NewAssignListStmt(call.Pos(), ir.OAS2, ir.ToNodes(inlvars), args)
  3525  	as2.Def = true
  3526  	var as2init ir.Nodes
  3527  	for _, name := range inlvars {
  3528  		if ir.IsBlank(name) {
  3529  			continue
  3530  		}
  3531  		// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3532  		as2init.Append(ir.NewDecl(call.Pos(), ir.ODCL, name))
  3533  		name.Defn = as2
  3534  	}
  3535  	as2.SetInit(as2init)
  3536  	init.Append(typecheck.Stmt(as2))
  3537  
  3538  	if !r.delayResults {
  3539  		// If not delaying retvars, declare and zero initialize the
  3540  		// result variables now.
  3541  		for _, name := range retvars {
  3542  			// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3543  			init.Append(ir.NewDecl(call.Pos(), ir.ODCL, name))
  3544  			ras := ir.NewAssignStmt(call.Pos(), name, nil)
  3545  			init.Append(typecheck.Stmt(ras))
  3546  		}
  3547  	}
  3548  
  3549  	// Add an inline mark just before the inlined body.
  3550  	// This mark is inline in the code so that it's a reasonable spot
  3551  	// to put a breakpoint. Not sure if that's really necessary or not
  3552  	// (in which case it could go at the end of the function instead).
  3553  	// Note issue 28603.
  3554  	init.Append(ir.NewInlineMarkStmt(call.Pos().WithIsStmt(), int64(r.inlTreeIndex)))
  3555  
  3556  	ir.WithFunc(r.curfn, func() {
  3557  		if !r.syntheticBody(call.Pos()) {
  3558  			assert(r.Bool()) // have body
  3559  
  3560  			r.curfn.Body = r.stmts()
  3561  			r.curfn.Endlineno = r.pos()
  3562  		}
  3563  
  3564  		// TODO(mdempsky): This shouldn't be necessary. Inlining might
  3565  		// read in new function/method declarations, which could
  3566  		// potentially be recursively inlined themselves; but we shouldn't
  3567  		// need to read in the non-inlined bodies for the declarations
  3568  		// themselves. But currently it's an easy fix to #50552.
  3569  		readBodies(typecheck.Target, true)
  3570  
  3571  		// Replace any "return" statements within the function body.
  3572  		var edit func(ir.Node) ir.Node
  3573  		edit = func(n ir.Node) ir.Node {
  3574  			if ret, ok := n.(*ir.ReturnStmt); ok {
  3575  				n = typecheck.Stmt(r.inlReturn(ret, retvars))
  3576  			}
  3577  			ir.EditChildren(n, edit)
  3578  			return n
  3579  		}
  3580  		edit(r.curfn)
  3581  	})
  3582  
  3583  	body := r.curfn.Body
  3584  
  3585  	// Reparent any declarations into the caller function.
  3586  	for _, name := range r.curfn.Dcl {
  3587  		name.Curfn = callerfn
  3588  
  3589  		if name.Class != ir.PAUTO {
  3590  			name.SetPos(r.inlPos(name.Pos()))
  3591  			name.SetInlFormal(true)
  3592  			name.Class = ir.PAUTO
  3593  		} else {
  3594  			name.SetInlLocal(true)
  3595  		}
  3596  	}
  3597  	callerfn.Dcl = append(callerfn.Dcl, r.curfn.Dcl...)
  3598  
  3599  	body.Append(ir.NewLabelStmt(call.Pos(), r.retlabel))
  3600  
  3601  	res := ir.NewInlinedCallExpr(call.Pos(), body, ir.ToNodes(retvars))
  3602  	res.SetInit(init)
  3603  	res.SetType(call.Type())
  3604  	res.SetTypecheck(1)
  3605  
  3606  	// Inlining shouldn't add any functions to todoBodies.
  3607  	assert(len(todoBodies) == 0)
  3608  
  3609  	return res
  3610  }
  3611  
  3612  // inlReturn returns a statement that can substitute for the given
  3613  // return statement when inlining.
  3614  func (r *reader) inlReturn(ret *ir.ReturnStmt, retvars []*ir.Name) *ir.BlockStmt {
  3615  	pos := r.inlCall.Pos()
  3616  
  3617  	block := ir.TakeInit(ret)
  3618  
  3619  	if results := ret.Results; len(results) != 0 {
  3620  		assert(len(retvars) == len(results))
  3621  
  3622  		as2 := ir.NewAssignListStmt(pos, ir.OAS2, ir.ToNodes(retvars), ret.Results)
  3623  
  3624  		if r.delayResults {
  3625  			for _, name := range retvars {
  3626  				// TODO(mdempsky): Use inlined position of name.Pos() instead?
  3627  				block.Append(ir.NewDecl(pos, ir.ODCL, name))
  3628  				name.Defn = as2
  3629  			}
  3630  		}
  3631  
  3632  		block.Append(as2)
  3633  	}
  3634  
  3635  	block.Append(ir.NewBranchStmt(pos, ir.OGOTO, r.retlabel))
  3636  	return ir.NewBlockStmt(pos, block)
  3637  }
  3638  
  3639  // expandInline reads in an extra copy of IR to populate
  3640  // fn.Inl.Dcl.
  3641  func expandInline(fn *ir.Func, pri pkgReaderIndex) {
  3642  	// TODO(mdempsky): Remove this function. It's currently needed by
  3643  	// dwarfgen/dwarf.go:preInliningDcls, which requires fn.Inl.Dcl to
  3644  	// create abstract function DIEs. But we should be able to provide it
  3645  	// with the same information some other way.
  3646  
  3647  	fndcls := len(fn.Dcl)
  3648  	topdcls := len(typecheck.Target.Funcs)
  3649  
  3650  	tmpfn := ir.NewFunc(fn.Pos(), fn.Nname.Pos(), fn.Sym(), fn.Type())
  3651  	tmpfn.ClosureVars = fn.ClosureVars
  3652  
  3653  	{
  3654  		r := pri.asReader(pkgbits.SectionBody, pkgbits.SyncFuncBody)
  3655  
  3656  		// Don't change parameter's Sym/Nname fields.
  3657  		r.funarghack = true
  3658  
  3659  		r.funcBody(tmpfn)
  3660  	}
  3661  
  3662  	// Move tmpfn's params to fn.Inl.Dcl, and reparent under fn.
  3663  	for _, name := range tmpfn.Dcl {
  3664  		name.Curfn = fn
  3665  	}
  3666  	fn.Inl.Dcl = tmpfn.Dcl
  3667  	fn.Inl.HaveDcl = true
  3668  
  3669  	// Double check that we didn't change fn.Dcl by accident.
  3670  	assert(fndcls == len(fn.Dcl))
  3671  
  3672  	// typecheck.Stmts may have added function literals to
  3673  	// typecheck.Target.Decls. Remove them again so we don't risk trying
  3674  	// to compile them multiple times.
  3675  	typecheck.Target.Funcs = typecheck.Target.Funcs[:topdcls]
  3676  }
  3677  
  3678  // @@@ Method wrappers
  3679  //
  3680  // Here we handle constructing "method wrappers," alternative entry
  3681  // points that adapt methods to different calling conventions. Given a
  3682  // user-declared method "func (T) M(i int) bool { ... }", there are a
  3683  // few wrappers we may need to construct:
  3684  //
  3685  //	- Implicit dereferencing. Methods declared with a value receiver T
  3686  //	  are also included in the method set of the pointer type *T, so
  3687  //	  we need to construct a wrapper like "func (recv *T) M(i int)
  3688  //	  bool { return (*recv).M(i) }".
  3689  //
  3690  //	- Promoted methods. If struct type U contains an embedded field of
  3691  //	  type T or *T, we need to construct a wrapper like "func (recv U)
  3692  //	  M(i int) bool { return recv.T.M(i) }".
  3693  //
  3694  //	- Method values. If x is an expression of type T, then "x.M" is
  3695  //	  roughly "tmp := x; func(i int) bool { return tmp.M(i) }".
  3696  //
  3697  // At call sites, we always prefer to call the user-declared method
  3698  // directly, if known, so wrappers are only needed for indirect calls
  3699  // (for example, interface method calls that can't be devirtualized).
  3700  // Consequently, we can save some compile time by skipping
  3701  // construction of wrappers that are never needed.
  3702  //
  3703  // Alternatively, because the linker doesn't care which compilation
  3704  // unit constructed a particular wrapper, we can instead construct
  3705  // them as needed. However, if a wrapper is needed in multiple
  3706  // downstream packages, we may end up needing to compile it multiple
  3707  // times, costing us more compile time and object file size. (We mark
  3708  // the wrappers as DUPOK, so the linker doesn't complain about the
  3709  // duplicate symbols.)
  3710  //
  3711  // The current heuristics we use to balance these trade offs are:
  3712  //
  3713  //	- For a (non-parameterized) defined type T, we construct wrappers
  3714  //	  for *T and any promoted methods on T (and *T) in the same
  3715  //	  compilation unit as the type declaration.
  3716  //
  3717  //	- For a parameterized defined type, we construct wrappers in the
  3718  //	  compilation units in which the type is instantiated. We
  3719  //	  similarly handle wrappers for anonymous types with methods and
  3720  //	  compilation units where their type literals appear in source.
  3721  //
  3722  //	- Method value expressions are relatively uncommon, so we
  3723  //	  construct their wrappers in the compilation units that they
  3724  //	  appear in.
  3725  //
  3726  // Finally, as an opportunistic compile-time optimization, if we know
  3727  // a wrapper was constructed in any imported package's compilation
  3728  // unit, then we skip constructing a duplicate one. However, currently
  3729  // this is only done on a best-effort basis.
  3730  
  3731  // needWrapperTypes lists types for which we may need to generate
  3732  // method wrappers.
  3733  var needWrapperTypes []*types.Type
  3734  
  3735  // haveWrapperTypes lists types for which we know we already have
  3736  // method wrappers, because we found the type in an imported package.
  3737  var haveWrapperTypes []*types.Type
  3738  
  3739  // needMethodValueWrappers lists methods for which we may need to
  3740  // generate method value wrappers.
  3741  var needMethodValueWrappers []methodValueWrapper
  3742  
  3743  // haveMethodValueWrappers lists methods for which we know we already
  3744  // have method value wrappers, because we found it in an imported
  3745  // package.
  3746  var haveMethodValueWrappers []methodValueWrapper
  3747  
  3748  type methodValueWrapper struct {
  3749  	rcvr   *types.Type
  3750  	method *types.Field
  3751  }
  3752  
  3753  // needWrapper records that wrapper methods may be needed at link
  3754  // time.
  3755  func (r *reader) needWrapper(typ *types.Type) {
  3756  	if typ.IsPtr() {
  3757  		return
  3758  	}
  3759  
  3760  	// Special case: runtime must define error even if imported packages mention it (#29304).
  3761  	forceNeed := typ == types.ErrorType && base.Ctxt.Pkgpath == "runtime"
  3762  
  3763  	// If a type was found in an imported package, then we can assume
  3764  	// that package (or one of its transitive dependencies) already
  3765  	// generated method wrappers for it.
  3766  	if r.importedDef() && !forceNeed {
  3767  		haveWrapperTypes = append(haveWrapperTypes, typ)
  3768  	} else {
  3769  		needWrapperTypes = append(needWrapperTypes, typ)
  3770  	}
  3771  }
  3772  
  3773  // importedDef reports whether r is reading from an imported and
  3774  // non-generic element.
  3775  //
  3776  // If a type was found in an imported package, then we can assume that
  3777  // package (or one of its transitive dependencies) already generated
  3778  // method wrappers for it.
  3779  //
  3780  // Exception: If we're instantiating an imported generic type or
  3781  // function, we might be instantiating it with type arguments not
  3782  // previously seen before.
  3783  //
  3784  // TODO(mdempsky): Distinguish when a generic function or type was
  3785  // instantiated in an imported package so that we can add types to
  3786  // haveWrapperTypes instead.
  3787  func (r *reader) importedDef() bool {
  3788  	return r.p != localPkgReader && !r.hasTypeParams()
  3789  }
  3790  
  3791  // MakeWrappers constructs all wrapper methods needed for the target
  3792  // compilation unit.
  3793  func MakeWrappers(target *ir.Package) {
  3794  	// always generate a wrapper for error.Error (#29304)
  3795  	needWrapperTypes = append(needWrapperTypes, types.ErrorType)
  3796  
  3797  	seen := make(map[string]*types.Type)
  3798  
  3799  	for _, typ := range haveWrapperTypes {
  3800  		wrapType(typ, target, seen, false)
  3801  	}
  3802  	haveWrapperTypes = nil
  3803  
  3804  	for _, typ := range needWrapperTypes {
  3805  		wrapType(typ, target, seen, true)
  3806  	}
  3807  	needWrapperTypes = nil
  3808  
  3809  	for _, wrapper := range haveMethodValueWrappers {
  3810  		wrapMethodValue(wrapper.rcvr, wrapper.method, target, false)
  3811  	}
  3812  	haveMethodValueWrappers = nil
  3813  
  3814  	for _, wrapper := range needMethodValueWrappers {
  3815  		wrapMethodValue(wrapper.rcvr, wrapper.method, target, true)
  3816  	}
  3817  	needMethodValueWrappers = nil
  3818  }
  3819  
  3820  func wrapType(typ *types.Type, target *ir.Package, seen map[string]*types.Type, needed bool) {
  3821  	key := typ.LinkString()
  3822  	if prev := seen[key]; prev != nil {
  3823  		if !types.Identical(typ, prev) {
  3824  			base.Fatalf("collision: types %v and %v have link string %q", typ, prev, key)
  3825  		}
  3826  		return
  3827  	}
  3828  	seen[key] = typ
  3829  
  3830  	if !needed {
  3831  		// Only called to add to 'seen'.
  3832  		return
  3833  	}
  3834  
  3835  	if !typ.IsInterface() {
  3836  		typecheck.CalcMethods(typ)
  3837  	}
  3838  	for _, meth := range typ.AllMethods() {
  3839  		if meth.Sym.IsBlank() || !meth.IsMethod() {
  3840  			base.FatalfAt(meth.Pos, "invalid method: %v", meth)
  3841  		}
  3842  
  3843  		methodWrapper(0, typ, meth, target)
  3844  
  3845  		// For non-interface types, we also want *T wrappers.
  3846  		if !typ.IsInterface() {
  3847  			methodWrapper(1, typ, meth, target)
  3848  
  3849  			// For not-in-heap types, *T is a scalar, not pointer shaped,
  3850  			// so the interface wrappers use **T.
  3851  			if typ.NotInHeap() {
  3852  				methodWrapper(2, typ, meth, target)
  3853  			}
  3854  		}
  3855  	}
  3856  }
  3857  
  3858  func methodWrapper(derefs int, tbase *types.Type, method *types.Field, target *ir.Package) {
  3859  	wrapper := tbase
  3860  	for i := 0; i < derefs; i++ {
  3861  		wrapper = types.NewPtr(wrapper)
  3862  	}
  3863  
  3864  	sym := ir.MethodSym(wrapper, method.Sym)
  3865  	base.Assertf(!sym.Siggen(), "already generated wrapper %v", sym)
  3866  	sym.SetSiggen(true)
  3867  
  3868  	wrappee := method.Type.Recv().Type
  3869  	if types.Identical(wrapper, wrappee) ||
  3870  		!types.IsMethodApplicable(wrapper, method) ||
  3871  		!reflectdata.NeedEmit(tbase) {
  3872  		return
  3873  	}
  3874  
  3875  	// TODO(mdempsky): Use method.Pos instead?
  3876  	pos := base.AutogeneratedPos
  3877  
  3878  	fn := newWrapperFunc(pos, sym, wrapper, method)
  3879  
  3880  	var recv ir.Node = fn.Nname.Type().Recv().Nname.(*ir.Name)
  3881  
  3882  	// For simple *T wrappers around T methods, panicwrap produces a
  3883  	// nicer panic message.
  3884  	if wrapper.IsPtr() && types.Identical(wrapper.Elem(), wrappee) {
  3885  		cond := ir.NewBinaryExpr(pos, ir.OEQ, recv, types.BuiltinPkg.Lookup("nil").Def.(ir.Node))
  3886  		then := []ir.Node{ir.NewCallExpr(pos, ir.OCALL, typecheck.LookupRuntime("panicwrap"), nil)}
  3887  		fn.Body.Append(ir.NewIfStmt(pos, cond, then, nil))
  3888  	}
  3889  
  3890  	// typecheck will add one implicit deref, if necessary,
  3891  	// but not-in-heap types require more for their **T wrappers.
  3892  	for i := 1; i < derefs; i++ {
  3893  		recv = Implicit(ir.NewStarExpr(pos, recv))
  3894  	}
  3895  
  3896  	addTailCall(pos, fn, recv, method)
  3897  
  3898  	finishWrapperFunc(fn, target)
  3899  }
  3900  
  3901  func wrapMethodValue(recvType *types.Type, method *types.Field, target *ir.Package, needed bool) {
  3902  	sym := ir.MethodSymSuffix(recvType, method.Sym, "-fm")
  3903  	if sym.Uniq() {
  3904  		return
  3905  	}
  3906  	sym.SetUniq(true)
  3907  
  3908  	// TODO(mdempsky): Use method.Pos instead?
  3909  	pos := base.AutogeneratedPos
  3910  
  3911  	fn := newWrapperFunc(pos, sym, nil, method)
  3912  	sym.Def = fn.Nname
  3913  
  3914  	// Declare and initialize variable holding receiver.
  3915  	recv := ir.NewHiddenParam(pos, fn, typecheck.Lookup(".this"), recvType)
  3916  
  3917  	if !needed {
  3918  		return
  3919  	}
  3920  
  3921  	addTailCall(pos, fn, recv, method)
  3922  
  3923  	finishWrapperFunc(fn, target)
  3924  }
  3925  
  3926  func newWrapperFunc(pos src.XPos, sym *types.Sym, wrapper *types.Type, method *types.Field) *ir.Func {
  3927  	sig := newWrapperType(wrapper, method)
  3928  	fn := ir.NewFunc(pos, pos, sym, sig)
  3929  	fn.DeclareParams(true)
  3930  	fn.SetDupok(true) // TODO(mdempsky): Leave unset for local, non-generic wrappers?
  3931  
  3932  	return fn
  3933  }
  3934  
  3935  func finishWrapperFunc(fn *ir.Func, target *ir.Package) {
  3936  	ir.WithFunc(fn, func() {
  3937  		typecheck.Stmts(fn.Body)
  3938  	})
  3939  
  3940  	// We generate wrappers after the global inlining pass,
  3941  	// so we're responsible for applying inlining ourselves here.
  3942  	// TODO(prattmic): plumb PGO.
  3943  	interleaved.DevirtualizeAndInlineFunc(fn, nil)
  3944  
  3945  	// The body of wrapper function after inlining may reveal new ir.OMETHVALUE node,
  3946  	// we don't know whether wrapper function has been generated for it or not, so
  3947  	// generate one immediately here.
  3948  	//
  3949  	// Further, after CL 492017, function that construct closures is allowed to be inlined,
  3950  	// even though the closure itself can't be inline. So we also need to visit body of any
  3951  	// closure that we see when visiting body of the wrapper function.
  3952  	ir.VisitFuncAndClosures(fn, func(n ir.Node) {
  3953  		if n, ok := n.(*ir.SelectorExpr); ok && n.Op() == ir.OMETHVALUE {
  3954  			wrapMethodValue(n.X.Type(), n.Selection, target, true)
  3955  		}
  3956  	})
  3957  
  3958  	fn.Nname.Defn = fn
  3959  	target.Funcs = append(target.Funcs, fn)
  3960  }
  3961  
  3962  // newWrapperType returns a copy of the given signature type, but with
  3963  // the receiver parameter type substituted with recvType.
  3964  // If recvType is nil, newWrapperType returns a signature
  3965  // without a receiver parameter.
  3966  func newWrapperType(recvType *types.Type, method *types.Field) *types.Type {
  3967  	clone := func(params []*types.Field) []*types.Field {
  3968  		res := make([]*types.Field, len(params))
  3969  		for i, param := range params {
  3970  			res[i] = types.NewField(param.Pos, param.Sym, param.Type)
  3971  			res[i].SetIsDDD(param.IsDDD())
  3972  		}
  3973  		return res
  3974  	}
  3975  
  3976  	sig := method.Type
  3977  
  3978  	var recv *types.Field
  3979  	if recvType != nil {
  3980  		recv = types.NewField(sig.Recv().Pos, sig.Recv().Sym, recvType)
  3981  	}
  3982  	params := clone(sig.Params())
  3983  	results := clone(sig.Results())
  3984  
  3985  	return types.NewSignature(recv, params, results)
  3986  }
  3987  
  3988  func addTailCall(pos src.XPos, fn *ir.Func, recv ir.Node, method *types.Field) {
  3989  	sig := fn.Nname.Type()
  3990  	args := make([]ir.Node, sig.NumParams())
  3991  	for i, param := range sig.Params() {
  3992  		args[i] = param.Nname.(*ir.Name)
  3993  	}
  3994  
  3995  	dot := typecheck.XDotMethod(pos, recv, method.Sym, true)
  3996  	call := typecheck.Call(pos, dot, args, method.Type.IsVariadic()).(*ir.CallExpr)
  3997  
  3998  	if recv.Type() != nil && recv.Type().IsPtr() && method.Type.Recv().Type.IsPtr() &&
  3999  		method.Embedded != 0 && !types.IsInterfaceMethod(method.Type) &&
  4000  		!unifiedHaveInlineBody(ir.MethodExprName(dot).Func) &&
  4001  		!(base.Ctxt.Arch.Name == "ppc64le" && base.Ctxt.Flag_dynlink) {
  4002  		if base.Debug.TailCall != 0 {
  4003  			base.WarnfAt(fn.Nname.Type().Recv().Type.Elem().Pos(), "tail call emitted for the method %v wrapper", method.Nname)
  4004  		}
  4005  		// Prefer OTAILCALL to reduce code size (except the case when the called method can be inlined).
  4006  		fn.Body.Append(ir.NewTailCallStmt(pos, call))
  4007  		return
  4008  	}
  4009  
  4010  	fn.SetWrapper(true)
  4011  
  4012  	if method.Type.NumResults() == 0 {
  4013  		fn.Body.Append(call)
  4014  		return
  4015  	}
  4016  
  4017  	ret := ir.NewReturnStmt(pos, nil)
  4018  	ret.Results = []ir.Node{call}
  4019  	fn.Body.Append(ret)
  4020  }
  4021  
  4022  func setBasePos(pos src.XPos) {
  4023  	// Set the position for any error messages we might print (e.g. too large types).
  4024  	base.Pos = pos
  4025  }
  4026  
  4027  // dictParamName is the name of the synthetic dictionary parameter
  4028  // added to shaped functions.
  4029  //
  4030  // N.B., this variable name is known to Delve:
  4031  // https://github.com/go-delve/delve/blob/cb91509630529e6055be845688fd21eb89ae8714/pkg/proc/eval.go#L28
  4032  const dictParamName = typecheck.LocalDictName
  4033  
  4034  // shapeSig returns a copy of fn's signature, except adding a
  4035  // dictionary parameter and promoting the receiver parameter (if any)
  4036  // to a normal parameter.
  4037  //
  4038  // The parameter types.Fields are all copied too, so their Nname
  4039  // fields can be initialized for use by the shape function.
  4040  func shapeSig(fn *ir.Func, dict *readerDict) *types.Type {
  4041  	sig := fn.Nname.Type()
  4042  	oldRecv := sig.Recv()
  4043  
  4044  	var recv *types.Field
  4045  	if oldRecv != nil {
  4046  		recv = types.NewField(oldRecv.Pos, oldRecv.Sym, oldRecv.Type)
  4047  	}
  4048  
  4049  	params := make([]*types.Field, 1+sig.NumParams())
  4050  	params[0] = types.NewField(fn.Pos(), fn.Sym().Pkg.Lookup(dictParamName), types.NewPtr(dict.varType()))
  4051  	for i, param := range sig.Params() {
  4052  		d := types.NewField(param.Pos, param.Sym, param.Type)
  4053  		d.SetIsDDD(param.IsDDD())
  4054  		params[1+i] = d
  4055  	}
  4056  
  4057  	results := make([]*types.Field, sig.NumResults())
  4058  	for i, result := range sig.Results() {
  4059  		results[i] = types.NewField(result.Pos, result.Sym, result.Type)
  4060  	}
  4061  
  4062  	return types.NewSignature(recv, params, results)
  4063  }
  4064  

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