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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package noder

import (
	"fmt"
	"go/constant"
	"internal/buildcfg"
	"strings"

	"cmd/compile/internal/base"
	"cmd/compile/internal/deadcode"
	"cmd/compile/internal/dwarfgen"
	"cmd/compile/internal/inline"
	"cmd/compile/internal/ir"
	"cmd/compile/internal/reflectdata"
	"cmd/compile/internal/staticinit"
	"cmd/compile/internal/typecheck"
	"cmd/compile/internal/types"
	"cmd/internal/obj"
// This file implements cmd/compile backend's reader for the Unified
// IR export data.

// A pkgReader reads Unified IR export data.
type pkgReader struct {
	// Indices for encoded things; lazily populated as needed.
	//
	// Note: Objects (i.e., ir.Names) are lazily instantiated by
	// populating their types.Sym.Def; see objReader below.

	posBases []*src.PosBase
	pkgs     []*types.Pkg
	typs     []*types.Type

	// offset for rewriting the given (absolute!) index into the output,
	// but bitwise inverted so we can detect if we're missing the entry
	// or not.
	newindex []pkgbits.Index
func newPkgReader(pr pkgbits.PkgDecoder) *pkgReader {
		posBases: make([]*src.PosBase, pr.NumElems(pkgbits.RelocPosBase)),
		pkgs:     make([]*types.Pkg, pr.NumElems(pkgbits.RelocPkg)),
		typs:     make([]*types.Type, pr.NumElems(pkgbits.RelocType)),
		newindex: make([]pkgbits.Index, pr.TotalElems()),
// A pkgReaderIndex compactly identifies an index (and its
// corresponding dictionary) within a package's export data.
type pkgReaderIndex struct {
	pr        *pkgReader
	idx       pkgbits.Index
	dict      *readerDict
	methodSym *types.Sym

	synthetic func(pos src.XPos, r *reader)
func (pri pkgReaderIndex) asReader(k pkgbits.RelocKind, marker pkgbits.SyncMarker) *reader {
	if pri.synthetic != nil {
		return &reader{synthetic: pri.synthetic}
	}

	r := pri.pr.newReader(k, pri.idx, marker)
func (pr *pkgReader) newReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
		Decoder: pr.NewDecoder(k, idx, marker),
// A reader provides APIs for reading an individual element.
	// TODO(mdempsky): The state below is all specific to reading
	// function bodies. It probably makes sense to split it out
	// separately so that it doesn't take up space in every reader
	// instance.

	curfn       *ir.Func
	locals      []*ir.Name
	closureVars []*ir.Name
	// methodSym is the name of method's name, if reading a method.
	// It's nil if reading a normal function or closure body.
	methodSym *types.Sym

	// dictParam is the .dict param, if any.
	dictParam *ir.Name

	// synthetic is a callback function to construct a synthetic
	// function body. It's used for creating the bodies of function
	// literals used to curry arguments to shaped functions.
	synthetic func(pos src.XPos, r *reader)

	// scopeVars is a stack tracking the number of variables declared in
	// the current function at the moment each open scope was opened.
	scopeVars         []int
	marker            dwarfgen.ScopeMarker
	lastCloseScopePos src.XPos

	// === details for handling inline body expansion ===

	// If we're reading in a function body because of inlining, this is
	// the call that we're inlining for.
	inlCaller    *ir.Func
	inlCall      *ir.CallExpr
	inlFunc      *ir.Func
	inlTreeIndex int
	inlPosBases  map[*src.PosBase]*src.PosBase

	// suppressInlPos tracks whether position base rewriting for
	// inlining should be suppressed. See funcLit.
	suppressInlPos int

	delayResults bool

	// Label to return to.
	retlabel *types.Sym

	// inlvars is the list of variables that the inlinee's arguments are
	// assigned to, one for each receiver and normal parameter, in order.
	inlvars ir.Nodes

	// retvars is the list of variables that the inlinee's results are
	// assigned to, one for each result parameter, in order.
	retvars ir.Nodes
// A readerDict represents an instantiated "compile-time dictionary,"
// used for resolving any derived types needed for instantiating a
// generic object.
//
// A compile-time dictionary can either be "shaped" or "non-shaped."
// Shaped compile-time dictionaries are only used for instantiating
// shaped type definitions and function bodies, while non-shaped
// compile-time dictionaries are used for instantiating runtime
// dictionaries.
	shaped bool // whether this is a shaped dictionary

	// baseSym is the symbol for the object this dictionary belongs to.
	// If the object is an instantiated function or defined type, then
	// baseSym is the mangled symbol, including any type arguments.
	baseSym *types.Sym

	// For non-shaped dictionaries, shapedObj is a reference to the
	// corresponding shaped object (always a function or defined type).
	shapedObj *ir.Name

	// targs holds the implicit and explicit type arguments in use for
	// reading the current object. For example:
	//
	//	func F[T any]() {
	//		type X[U any] struct { t T; u U }
	//		var _ X[string]
	//	}
	//
	//	var _ = F[int]
	//
	// While instantiating F[int], we need to in turn instantiate
	// X[string]. [int] and [string] are explicit type arguments for F
	// and X, respectively; but [int] is also the implicit type
	// arguments for X.
	//
	// (As an analogy to function literals, explicits are the function
	// literal's formal parameters, while implicits are variables
	// captured by the function literal.)
	targs []*types.Type

	// implicits counts how many of types within targs are implicit type
	// arguments; the rest are explicit.
	implicits int
	derived      []derivedInfo // reloc index of the derived type's descriptor
	derivedTypes []*types.Type // slice of previously computed derived types

	// These slices correspond to entries in the runtime dictionary.
	typeParamMethodExprs []readerMethodExprInfo
	subdicts             []objInfo
	rtypes               []typeInfo
	itabs                []itabInfo
}

type readerMethodExprInfo struct {
	typeParamIdx int
	method       *types.Sym
func setType(n ir.Node, typ *types.Type) {
func setValue(name *ir.Name, val constant.Value) {
	name.SetVal(val)
	name.Defn = nil
}

// @@@ Positions

// pos reads a position from the bitstream.
func (r *reader) pos() src.XPos {
	return base.Ctxt.PosTable.XPos(r.pos0())
}

func (r *reader) pos0() src.Pos {
	r.Sync(pkgbits.SyncPos)
	if !r.Bool() {
		return src.NoPos
	}

	posBase := r.posBase()
	line := r.Uint()
	col := r.Uint()
	return src.MakePos(posBase, line, col)
}

// posBase reads a position base from the bitstream.
func (r *reader) posBase() *src.PosBase {
	return r.inlPosBase(r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase)))
// posBaseIdx returns the specified position base, reading it first if
// needed.
func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) *src.PosBase {
	if b := pr.posBases[idx]; b != nil {
		return b
	}

	r := pr.newReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
	absFilename := r.String()
	filename := absFilename

	// For build artifact stability, the export data format only
	// contains the "absolute" filename as returned by objabi.AbsFile.
	// However, some tests (e.g., test/run.go's asmcheck tests) expect
	// to see the full, original filename printed out. Re-expanding
	// "$GOROOT" to buildcfg.GOROOT is a close-enough approximation to
	// satisfy this.
	//
	// TODO(mdempsky): De-duplicate this logic with similar logic in
	// cmd/link/internal/ld's expandGoroot. However, this will probably
	// require being more consistent about when we use native vs UNIX
	// file paths.
	const dollarGOROOT = "$GOROOT"
	if buildcfg.GOROOT != "" && strings.HasPrefix(filename, dollarGOROOT) {
		filename = buildcfg.GOROOT + filename[len(dollarGOROOT):]
	}
		b = src.NewFileBase(filename, absFilename)
		line := r.Uint()
		col := r.Uint()
		b = src.NewLinePragmaBase(pos, filename, absFilename, line, col)
// inlPosBase returns the inlining-adjusted src.PosBase corresponding
// to oldBase, which must be a non-inlined position. When not
// inlining, this is just oldBase.
func (r *reader) inlPosBase(oldBase *src.PosBase) *src.PosBase {
	if index := oldBase.InliningIndex(); index >= 0 {
		base.Fatalf("oldBase %v already has inlining index %v", oldBase, index)
	}

	if r.inlCall == nil || r.suppressInlPos != 0 {
		return oldBase
	}

	if newBase, ok := r.inlPosBases[oldBase]; ok {
		return newBase
	}

	newBase := src.NewInliningBase(oldBase, r.inlTreeIndex)
	r.inlPosBases[oldBase] = newBase
	return newBase
}

// inlPos returns the inlining-adjusted src.XPos corresponding to
// xpos, which must be a non-inlined position. When not inlining, this
// is just xpos.
func (r *reader) inlPos(xpos src.XPos) src.XPos {
	pos := base.Ctxt.PosTable.Pos(xpos)
	pos.SetBase(r.inlPosBase(pos.Base()))
	return base.Ctxt.PosTable.XPos(pos)
}

// @@@ Packages

// pkg reads a package reference from the bitstream.
func (r *reader) pkg() *types.Pkg {
	r.Sync(pkgbits.SyncPkg)
	return r.p.pkgIdx(r.Reloc(pkgbits.RelocPkg))
// pkgIdx returns the specified package from the export data, reading
// it first if needed.
func (pr *pkgReader) pkgIdx(idx pkgbits.Index) *types.Pkg {
	if pkg := pr.pkgs[idx]; pkg != nil {
		return pkg
	}

	pkg := pr.newReader(pkgbits.RelocPkg, idx, pkgbits.SyncPkgDef).doPkg()
// doPkg reads a package definition from the bitstream.
func (r *reader) doPkg() *types.Pkg {
	case "builtin":
		return types.BuiltinPkg
	case "unsafe":
		return types.UnsafePkg

	pkg := types.NewPkg(path, "")

	if pkg.Name == "" {
		pkg.Name = name
	} else {
		base.Assertf(pkg.Name == name, "package %q has name %q, but want %q", pkg.Path, pkg.Name, name)
	}

	return pkg
}

// @@@ Types

func (r *reader) typ() *types.Type {
	return r.typWrapped(true)
}

// typWrapped is like typ, but allows suppressing generation of
// unnecessary wrappers as a compile-time optimization.
func (r *reader) typWrapped(wrapped bool) *types.Type {
	return r.p.typIdx(r.typInfo(), r.dict, wrapped)
	r.Sync(pkgbits.SyncType)
	if r.Bool() {
		return typeInfo{idx: pkgbits.Index(r.Len()), derived: true}
	return typeInfo{idx: r.Reloc(pkgbits.RelocType), derived: false}
// typListIdx returns a list of the specified types, resolving derived
// types within the given dictionary.
func (pr *pkgReader) typListIdx(infos []typeInfo, dict *readerDict) []*types.Type {
	typs := make([]*types.Type, len(infos))
	for i, info := range infos {
		typs[i] = pr.typIdx(info, dict, true)
	}
	return typs
}

// typIdx returns the specified type. If info specifies a derived
// type, it's resolved within the given dictionary. If wrapped is
// true, then method wrappers will be generated, if appropriate.
func (pr *pkgReader) typIdx(info typeInfo, dict *readerDict, wrapped bool) *types.Type {
	if info.derived {
		where = &dict.derivedTypes[idx]
		idx = dict.derived[idx].idx
	} else {
		where = &pr.typs[idx]
	}

	if typ := *where; typ != nil {
	r := pr.newReader(pkgbits.RelocType, idx, pkgbits.SyncTypeIdx)
	typ := r.doTyp()
	assert(typ != nil)

	// For recursive type declarations involving interfaces and aliases,
	// above r.doTyp() call may have already set pr.typs[idx], so just
	// double check and return the type.
	//
	// Example:
	//
	//     type F = func(I)
	//
	//     type I interface {
	//         m(F)
	//     }
	//
	// The writer writes data types in following index order:
	//
	//     0: func(I)
	//     1: I
	//     2: interface{m(func(I))}
	//
	// The reader resolves it in following index order:
	//
	//     0 -> 1 -> 2 -> 0 -> 1
	//
	// and can divide in logically 2 steps:
	//
	//  - 0 -> 1     : first time the reader reach type I,
	//                 it creates new named type with symbol I.
	//
	//  - 2 -> 0 -> 1: the reader ends up reaching symbol I again,
	//                 now the symbol I was setup in above step, so
	//                 the reader just return the named type.
	//
	// Now, the functions called return, the pr.typs looks like below:
	//
	//  - 0 -> 1 -> 2 -> 0 : [<T> I <T>]
	//  - 0 -> 1 -> 2      : [func(I) I <T>]
	//  - 0 -> 1           : [func(I) I interface { "".m(func("".I)) }]
	//
	// The idx 1, corresponding with type I was resolved successfully
	// after r.doTyp() call.
	if prev := *where; prev != nil {
		return prev
	if wrapped {
		// Only cache if we're adding wrappers, so that other callers that
		// find a cached type know it was wrapped.
		*where = typ

		r.needWrapper(typ)
	}
	if !typ.IsUntyped() {
		types.CheckSize(typ)
	}

	return typ
}

func (r *reader) doTyp() *types.Type {
	switch tag := pkgbits.CodeType(r.Code(pkgbits.SyncType)); tag {
	default:
		panic(fmt.Sprintf("unexpected type: %v", tag))

	case pkgbits.TypeBasic:
		return *basics[r.Len()]
		obj := r.obj()
		assert(obj.Op() == ir.OTYPE)
		return obj.Type()

	case pkgbits.TypeTypeParam:
		return r.dict.targs[r.Len()]
	case pkgbits.TypeArray:
		len := int64(r.Uint64())
		return types.NewArray(r.typ(), len)
	case pkgbits.TypeChan:
		dir := dirs[r.Len()]
		return types.NewChan(r.typ(), dir)
		return types.NewMap(r.typ(), r.typ())
	case pkgbits.TypePointer:
		return types.NewPtr(r.typ())
	case pkgbits.TypeSignature:
		return r.signature(types.LocalPkg, nil)
		return types.NewSlice(r.typ())
	case pkgbits.TypeInterface:
		return r.interfaceType()
	case pkgbits.TypeUnion:
		return r.unionType()
func (r *reader) unionType() *types.Type {
	terms := make([]*types.Type, r.Len())
	tildes := make([]bool, len(terms))
	for i := range terms {
		tildes[i] = r.Bool()
		terms[i] = r.typ()
	}
	return types.NewUnion(terms, tildes)
}

func (r *reader) interfaceType() *types.Type {
	tpkg := types.LocalPkg // TODO(mdempsky): Remove after iexport is gone.

	nmethods, nembeddeds := r.Len(), r.Len()
	implicit := nmethods == 0 && nembeddeds == 1 && r.Bool()
	assert(!implicit) // implicit interfaces only appear in constraints

	fields := make([]*types.Field, nmethods+nembeddeds)
	methods, embeddeds := fields[:nmethods], fields[nmethods:]

	for i := range methods {
		pos := r.pos()
		pkg, sym := r.selector()
		tpkg = pkg
		mtyp := r.signature(pkg, types.FakeRecv())
		methods[i] = types.NewField(pos, sym, mtyp)
	}
	for i := range embeddeds {
		embeddeds[i] = types.NewField(src.NoXPos, nil, r.typ())
	}

	if len(fields) == 0 {
		return types.Types[types.TINTER] // empty interface
	}
	return types.NewInterface(tpkg, fields, false)
}

func (r *reader) structType() *types.Type {
	tpkg := types.LocalPkg // TODO(mdempsky): Remove after iexport is gone.
	fields := make([]*types.Field, r.Len())
	for i := range fields {
		pos := r.pos()
		pkg, sym := r.selector()
		tpkg = pkg
		ftyp := r.typ()
		tag := r.String()
		embedded := r.Bool()

		f := types.NewField(pos, sym, ftyp)
		f.Note = tag
		if embedded {
			f.Embedded = 1
		}
		fields[i] = f
	}
	return types.NewStruct(tpkg, fields)
}

func (r *reader) signature(tpkg *types.Pkg, recv *types.Field) *types.Type {
	r.Sync(pkgbits.SyncSignature)

	params := r.params(&tpkg)
	results := r.params(&tpkg)
	if r.Bool() { // variadic
		params[len(params)-1].SetIsDDD(true)
	}

	return types.NewSignature(tpkg, recv, nil, params, results)
}

func (r *reader) params(tpkg **types.Pkg) []*types.Field {
	r.Sync(pkgbits.SyncParams)
	fields := make([]*types.Field, r.Len())
	for i := range fields {
		*tpkg, fields[i] = r.param()
	}
	return fields
}

func (r *reader) param() (*types.Pkg, *types.Field) {
	r.Sync(pkgbits.SyncParam)

	pos := r.pos()
	pkg, sym := r.localIdent()
	typ := r.typ()

	return pkg, types.NewField(pos, sym, typ)
}

// @@@ Objects

// objReader maps qualified identifiers (represented as *types.Sym) to
// a pkgReader and corresponding index that can be used for reading
// that object's definition.
var objReader = map[*types.Sym]pkgReaderIndex{}

// obj reads an instantiated object reference from the bitstream.
func (r *reader) obj() ir.Node {
	return r.p.objInstIdx(r.objInfo(), r.dict, false)
}

// objInfo reads an instantiated object reference from the bitstream
// and returns the encoded reference to it, without instantiating it.
func (r *reader) objInfo() objInfo {
	r.Sync(pkgbits.SyncObject)
	assert(!r.Bool()) // TODO(mdempsky): Remove; was derived func inst.
	idx := r.Reloc(pkgbits.RelocObj)
	explicits := make([]typeInfo, r.Len())
	for i := range explicits {
	return objInfo{idx, explicits}
}

// objInstIdx returns the encoded, instantiated object. If shaped is
// true, then the shaped variant of the object is returned instead.
func (pr *pkgReader) objInstIdx(info objInfo, dict *readerDict, shaped bool) ir.Node {
	explicits := pr.typListIdx(info.explicits, dict)

	if dict != nil {
		implicits = dict.targs
	return pr.objIdx(info.idx, implicits, explicits, shaped)
// objIdx returns the specified object, instantiated with the given
// type arguments, if any. If shaped is true, then the shaped variant
// of the object is returned instead.
func (pr *pkgReader) objIdx(idx pkgbits.Index, implicits, explicits []*types.Type, shaped bool) ir.Node {
	rname := pr.newReader(pkgbits.RelocName, idx, pkgbits.SyncObject1)
	tag := pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
	if tag == pkgbits.ObjStub {
		assert(!sym.IsBlank())
		switch sym.Pkg {
		case types.BuiltinPkg, types.UnsafePkg:
			return sym.Def.(ir.Node)
		}
		if pri, ok := objReader[sym]; ok {
			return pri.pr.objIdx(pri.idx, nil, explicits, shaped)
		}
		base.Fatalf("unresolved stub: %v", sym)
	}
	dict := pr.objDictIdx(sym, idx, implicits, explicits, shaped)

	sym = dict.baseSym
	if !sym.IsBlank() && sym.Def != nil {
		return sym.Def.(*ir.Name)
	}
	r := pr.newReader(pkgbits.RelocObj, idx, pkgbits.SyncObject1)
	rext := pr.newReader(pkgbits.RelocObjExt, idx, pkgbits.SyncObject1)
	do := func(op ir.Op, hasTParams bool) *ir.Name {
		pos := r.pos()
		if hasTParams {
			r.typeParamNames()
		}

		name := ir.NewDeclNameAt(pos, op, sym)
		name.Class = ir.PEXTERN // may be overridden later
		if !sym.IsBlank() {
			if sym.Def != nil {
				base.FatalfAt(name.Pos(), "already have a definition for %v", name)
			}
			assert(sym.Def == nil)
			sym.Def = name
		}
		return name
	}

	switch tag {
	default:
		panic("unexpected object")

		name := do(ir.OTYPE, false)
		name := do(ir.OLITERAL, false)
		val := FixValue(typ, r.Value())
		setType(name, typ)
		setValue(name, val)
		if sym.Name == "init" {
			sym = Renameinit()
		}
		name := do(ir.ONAME, true)
		setType(name, r.signature(sym.Pkg, nil))

		name.Func = ir.NewFunc(r.pos())
		name.Func.Nname = name

		if r.hasTypeParams() {
			name.Func.SetDupok(true)
			if r.dict.shaped {
				setType(name, shapeSig(name.Func, r.dict))
			} else {
				todoDicts = append(todoDicts, func() {
					r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
				})
			}
		name := do(ir.OTYPE, true)
		typ := types.NewNamed(name)
		if r.hasTypeParams() && r.dict.shaped {
			typ.SetHasShape(true)
		}

		// Important: We need to do this before SetUnderlying.

		// We need to defer CheckSize until we've called SetUnderlying to
		// handle recursive types.
		types.DeferCheckSize()
		typ.SetUnderlying(r.typWrapped(false))
		if r.hasTypeParams() && !r.dict.shaped {
			todoDicts = append(todoDicts, func() {
				r.dict.shapedObj = pr.objIdx(idx, implicits, explicits, true).(*ir.Name)
			})
		}

		methods := make([]*types.Field, r.Len())
		for i := range methods {
		}
		if len(methods) != 0 {
			typ.Methods().Set(methods)
		}

		if !r.dict.shaped {
			r.needWrapper(typ)
		}
		name := do(ir.ONAME, false)
func (dict *readerDict) mangle(sym *types.Sym) *types.Sym {
	if !dict.hasTypeParams() {
	// If sym is a locally defined generic type, we need the suffix to
	// stay at the end after mangling so that types/fmt.go can strip it
	// out again when writing the type's runtime descriptor (#54456).
	base, suffix := types.SplitVargenSuffix(sym.Name)

	for i, targ := range dict.targs {
	return sym.Pkg.Lookup(buf.String())
}

// shapify returns the shape type for targ.
//
// If basic is true, then the type argument is used to instantiate a
// type parameter whose constraint is a basic interface.
func shapify(targ *types.Type, basic bool) *types.Type {
	base.Assertf(targ.Kind() != types.TFORW, "%v is missing its underlying type", targ)

	// When a pointer type is used to instantiate a type parameter
	// constrained by a basic interface, we know the pointer's element
	// type can't matter to the generated code. In this case, we can use
	// an arbitrary pointer type as the shape type. (To match the
	// non-unified frontend, we use `*byte`.)
	//
	// Otherwise, we simply use the type's underlying type as its shape.
	//
	// TODO(mdempsky): It should be possible to do much more aggressive
	// shaping still; e.g., collapsing all pointer-shaped types into a
	// common type, collapsing scalars of the same size/alignment into a
	// common type, recursively shaping the element types of composite
	// types, and discarding struct field names and tags. However, we'll
	// need to start tracking how type parameters are actually used to
	// implement some of these optimizations.
	if basic && targ.IsPtr() && !targ.Elem().NotInHeap() {
		under = types.NewPtr(types.Types[types.TUINT8])
	}

	sym := types.ShapePkg.Lookup(under.LinkString())
	if sym.Def == nil {
		name := ir.NewDeclNameAt(under.Pos(), ir.OTYPE, sym)
		typ := types.NewNamed(name)
		typ.SetUnderlying(under)
		sym.Def = typed(typ, name)
	}
	res := sym.Def.Type()
	assert(res.IsShape())
	assert(res.HasShape())
	return res
}

// objDictIdx reads and returns the specified object dictionary.
func (pr *pkgReader) objDictIdx(sym *types.Sym, idx pkgbits.Index, implicits, explicits []*types.Type, shaped bool) *readerDict {
	r := pr.newReader(pkgbits.RelocObjDict, idx, pkgbits.SyncObject1)
	nimplicits := r.Len()
	nexplicits := r.Len()
	if nimplicits > len(implicits) || nexplicits != len(explicits) {
		base.Fatalf("%v has %v+%v params, but instantiated with %v+%v args", sym, nimplicits, nexplicits, len(implicits), len(explicits))
	dict.targs = append(implicits[:nimplicits:nimplicits], explicits...)
	dict.implicits = nimplicits
	// Within the compiler, we can just skip over the type parameters.
	for range dict.targs[dict.implicits:] {
		// Skip past bounds without actually evaluating them.
		r.typInfo()
	}

	dict.derived = make([]derivedInfo, r.Len())
	dict.derivedTypes = make([]*types.Type, len(dict.derived))
	for i := range dict.derived {
		dict.derived[i] = derivedInfo{r.Reloc(pkgbits.RelocType), r.Bool()}
	}

	// Runtime dictionary information; private to the compiler.

	// If any type argument is already shaped, then we're constructing a
	// shaped object, even if not explicitly requested (i.e., calling
	// objIdx with shaped==true). This can happen with instantiating
	// types that are referenced within a function body.
	for _, targ := range dict.targs {
		if targ.HasShape() {
			dict.shaped = true
			break
		}
	}

	// And if we're constructing a shaped object, then shapify all type
	// arguments.
	for i, targ := range dict.targs {
		basic := r.Bool()
		if dict.shaped {
			dict.targs[i] = shapify(targ, basic)
		}
	}

	dict.baseSym = dict.mangle(sym)

	dict.typeParamMethodExprs = make([]readerMethodExprInfo, r.Len())
	for i := range dict.typeParamMethodExprs {
		typeParamIdx := r.Len()
		_, method := r.selector()

		dict.typeParamMethodExprs[i] = readerMethodExprInfo{typeParamIdx, method}
	}

	dict.subdicts = make([]objInfo, r.Len())
	for i := range dict.subdicts {
		dict.subdicts[i] = r.objInfo()
	}

	dict.rtypes = make([]typeInfo, r.Len())
	for i := range dict.rtypes {
		dict.rtypes[i] = r.typInfo()
	}

	dict.itabs = make([]itabInfo, r.Len())
	for i := range dict.itabs {
		dict.itabs[i] = itabInfo{typ: r.typInfo(), iface: r.typInfo()}
	}

}

func (r *reader) typeParamNames() {
	r.Sync(pkgbits.SyncTypeParamNames)
	for range r.dict.targs[r.dict.implicits:] {
func (r *reader) method(rext *reader) *types.Field {
	r.Sync(pkgbits.SyncMethod)
	pos := r.pos()
	pkg, sym := r.selector()
	r.typeParamNames()
	_, recv := r.param()
	typ := r.signature(pkg, recv)

	name := ir.NewNameAt(pos, ir.MethodSym(recv.Type, sym))

	name.Func = ir.NewFunc(r.pos())
	name.Func.Nname = name

	if r.hasTypeParams() {
		name.Func.SetDupok(true)
		if r.dict.shaped {
			typ = shapeSig(name.Func, r.dict)
			setType(name, typ)
		}

	meth := types.NewField(name.Func.Pos(), sym, typ)
	meth.Nname = name
	meth.SetNointerface(name.Func.Pragma&ir.Nointerface != 0)

	return meth
}

func (r *reader) qualifiedIdent() (pkg *types.Pkg, sym *types.Sym) {
	if name := r.String(); name != "" {
		sym = pkg.Lookup(name)
	}
	return
}

func (r *reader) localIdent() (pkg *types.Pkg, sym *types.Sym) {
	r.Sync(pkgbits.SyncLocalIdent)
	if name := r.String(); name != "" {
		sym = pkg.Lookup(name)
	}
	return
}

func (r *reader) selector() (origPkg *types.Pkg, sym *types.Sym) {
	r.Sync(pkgbits.SyncSelector)
	pkg := origPkg
	if types.IsExported(name) {
		pkg = types.LocalPkg
	}
	sym = pkg.Lookup(name)
	return
}

	return r.dict.hasTypeParams()
}

func (dict *readerDict) hasTypeParams() bool {
	return dict != nil && len(dict.targs) != 0
func (r *reader) funcExt(name *ir.Name, method *types.Sym) {
	r.Sync(pkgbits.SyncFuncExt)

	name.Class = 0 // so MarkFunc doesn't complain
	ir.MarkFunc(name)

	fn := name.Func

	// XXX: Workaround because linker doesn't know how to copy Pos.
	if !fn.Pos().IsKnown() {
		fn.SetPos(name.Pos())
	}

	// Normally, we only compile local functions, which saves redundant compilation work.
	// n.Defn is not nil for local functions, and is nil for imported function. But for
	// generic functions, we might have an instantiation that no other package has seen before.
	// So we need to be conservative and compile it again.
	//
	// That's why name.Defn is set here, so ir.VisitFuncsBottomUp can analyze function.
	// TODO(mdempsky,cuonglm): find a cleaner way to handle this.
	if name.Sym().Pkg == types.LocalPkg || r.hasTypeParams() {
		name.Defn = fn
	}

	fn.Pragma = r.pragmaFlag()
	r.linkname(name)

		fn.ABI = obj.ABI(r.Uint64())

		// Escape analysis.
		for _, fs := range &types.RecvsParams {
			for _, f := range fs(name.Type()).FieldSlice() {
				Cost:            int32(r.Len()),
				CanDelayResults: r.Bool(),
}

func (r *reader) typeExt(name *ir.Name) {
	r.Sync(pkgbits.SyncTypeExt)
		// Set "RParams" (really type arguments here, not parameters) so
		// this type is treated as "fully instantiated". This ensures the
		// type descriptor is written out as DUPOK and method wrappers are
		// generated even for imported types.
		var targs []*types.Type
		targs = append(targs, r.dict.targs...)
		typ.SetRParams(targs)
	}

	name.SetPragma(r.pragmaFlag())
	if name.Pragma()&ir.NotInHeap != 0 {
		typ.SetNotInHeap(true)
	}

	typecheck.SetBaseTypeIndex(typ, r.Int64(), r.Int64())
}

func (r *reader) varExt(name *ir.Name) {
	r.Sync(pkgbits.SyncVarExt)
	r.linkname(name)
}

func (r *reader) linkname(name *ir.Name) {
	assert(name.Op() == ir.ONAME)
	r.Sync(pkgbits.SyncLinkname)
	if idx := r.Int64(); idx >= 0 {
		lsym := name.Linksym()
		lsym.SymIdx = int32(idx)
		lsym.Set(obj.AttrIndexed, true)
	} else {
		name.Sym().Linkname = r.String()
	}
}

func (r *reader) pragmaFlag() ir.PragmaFlag {
	r.Sync(pkgbits.SyncPragma)
	return ir.PragmaFlag(r.Int())
// bodyReader tracks where the serialized IR for a local or imported,
// generic function's body can be found.
var bodyReader = map[*ir.Func]pkgReaderIndex{}

// importBodyReader tracks where the serialized IR for an imported,
// static (i.e., non-generic) function body can be read.
var importBodyReader = map[*types.Sym]pkgReaderIndex{}

// bodyReaderFor returns the pkgReaderIndex for reading fn's
// serialized IR, and whether one was found.
func bodyReaderFor(fn *ir.Func) (pri pkgReaderIndex, ok bool) {
	if fn.Nname.Defn != nil {
		pri, ok = bodyReader[fn]
		base.AssertfAt(ok, base.Pos, "must have bodyReader for %v", fn) // must always be available
// todoDicts holds the list of dictionaries that still need their
// runtime dictionary objects constructed.
var todoDicts []func()

// todoBodies holds the list of function bodies that still need to be
// constructed.
var todoBodies []*ir.Func

// addBody reads a function body reference from the element bitstream,
// and associates it with fn.
func (r *reader) addBody(fn *ir.Func, method *types.Sym) {
	// addBody should only be called for local functions or imported
	// generic functions; see comment in funcExt.
	assert(fn.Nname.Defn != nil)

	idx := r.Reloc(pkgbits.RelocBody)

	pri := pkgReaderIndex{r.p, idx, r.dict, method, nil}
		todoBodies = append(todoBodies, fn)
		return
	}

	pri.funcBody(fn)
}

func (pri pkgReaderIndex) funcBody(fn *ir.Func) {
	r := pri.asReader(pkgbits.RelocBody, pkgbits.SyncFuncBody)
// funcBody reads a function body definition from the element
// bitstream, and populates fn with it.
func (r *reader) funcBody(fn *ir.Func) {
	r.curfn = fn
	if len(r.closureVars) != 0 && r.hasTypeParams() {
		r.dictParam = r.closureVars[len(r.closureVars)-1] // dictParam is last; see reader.funcLit
	}
		body := r.stmts()
		if body == nil {
			body = []ir.Node{typecheck.Stmt(ir.NewBlockStmt(src.NoXPos, nil))}
		}
		fn.Body = body
		fn.Endlineno = r.pos()
// syntheticBody adds a synthetic body to r.curfn if appropriate, and
// reports whether it did.
func (r *reader) syntheticBody(pos src.XPos) bool {
	if r.synthetic != nil {
		r.synthetic(pos, r)
		return true
	}

	// If this function has type parameters and isn't shaped, then we
	// just tail call its corresponding shaped variant.
	if r.hasTypeParams() && !r.dict.shaped {
		r.callShaped(pos)
		return true
	}

	return false
}

// callShaped emits a tail call to r.shapedFn, passing along the
// arguments to the current function.
func (r *reader) callShaped(pos src.XPos) {
	shapedObj := r.dict.shapedObj
	assert(shapedObj != nil)

	var shapedFn ir.Node
	if r.methodSym == nil {
		// Instantiating a generic function; shapedObj is the shaped
		// function itself.
		assert(shapedObj.Op() == ir.ONAME && shapedObj.Class == ir.PFUNC)
		shapedFn = shapedObj
	} else {
		// Instantiating a generic type's method; shapedObj is the shaped
		// type, so we need to select it's corresponding method.
		shapedFn = shapedMethodExpr(pos, shapedObj, r.methodSym)
	}

	recvs, params := r.syntheticArgs(pos)
	// Construct the arguments list: receiver (if any), then runtime
	// dictionary, and finally normal parameters.
	//
	// Note: For simplicity, shaped methods are added as normal methods
	// on their shaped types. So existing code (e.g., packages ir and
	// typecheck) expects the shaped type to appear as the receiver
	// parameter (or first parameter, as a method expression). Hence
	// putting the dictionary parameter after that is the least invasive
	// solution at the moment.
	args.Append(recvs...)
	args.Append(typecheck.Expr(ir.NewAddrExpr(pos, r.p.dictNameOf(r.dict))))
	args.Append(params...)
	r.syntheticTailCall(pos, shapedFn, args)
}

// syntheticArgs returns the recvs and params arguments passed to the
// current function.
func (r *reader) syntheticArgs(pos src.XPos) (recvs, params ir.Nodes) {
	sig := r.curfn.Nname.Type()
	inlVarIdx := 0
	addParams := func(out *ir.Nodes, params []*types.Field) {
		for _, param := range params {
			var arg ir.Node
			if param.Nname != nil {
				name := param.Nname.(*ir.Name)
				if !ir.IsBlank(name) {
					if r.inlCall != nil {
						// During inlining, we want the respective inlvar where we
						// assigned the callee's arguments.
					} else {
						// Otherwise, we can use the parameter itself directly.
						base.AssertfAt(name.Curfn == r.curfn, name.Pos(), "%v has curfn %v, but want %v", name, name.Curfn, r.curfn)
						arg = name
					}
				}
			}

			// For anonymous and blank parameters, we don't have an *ir.Name
			// to use as the argument. However, since we know the shaped
			// function won't use the value either, we can just pass the
			// zero value. (Also unfortunately, we don't have an easy
			// zero-value IR node; so we use a default-initialized temporary
			// variable.)
			if arg == nil {
				tmp := typecheck.TempAt(pos, r.curfn, param.Type)
				r.curfn.Body.Append(
					typecheck.Stmt(ir.NewDecl(pos, ir.ODCL, tmp)),
					typecheck.Stmt(ir.NewAssignStmt(pos, tmp, nil)),
				)
				arg = tmp
			}

	addParams(&recvs, sig.Recvs().FieldSlice())
	addParams(&params, sig.Params().FieldSlice())
	return
}

// syntheticTailCall emits a tail call to fn, passing the given
// arguments list.
func (r *reader) syntheticTailCall(pos src.XPos, fn ir.Node, args ir.Nodes) {
	// Mark the function as a wrapper so it doesn't show up in stack
	// traces.
	r.curfn.SetWrapper(true)

	call := typecheck.Call(pos, fn, args, fn.Type().IsVariadic()).(*ir.CallExpr)
	if fn.Type().NumResults() != 0 {
		stmt = typecheck.Stmt(ir.NewReturnStmt(pos, []ir.Node{call}))
	} else {
		stmt = call
	}
	r.curfn.Body.Append(stmt)
}

// dictNameOf returns the runtime dictionary corresponding to dict.
func (pr *pkgReader) dictNameOf(dict *readerDict) *ir.Name {
	pos := base.AutogeneratedPos

	// Check that we only instantiate runtime dictionaries with real types.
	base.AssertfAt(!dict.shaped, pos, "runtime dictionary of shaped object %v", dict.baseSym)

	sym := dict.baseSym.Pkg.Lookup(objabi.GlobalDictPrefix + "." + dict.baseSym.Name)
	if sym.Def != nil {
		return sym.Def.(*ir.Name)
	name := ir.NewNameAt(pos, sym)
	name.Class = ir.PEXTERN
	sym.Def = name // break cycles with mutual subdictionaries

	lsym := name.Linksym()
	ot := 0

	assertOffset := func(section string, offset int) {
		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)
	assertOffset("type param method exprs", dict.typeParamMethodExprsOffset())
	for _, info := range dict.typeParamMethodExprs {
		typeParam := dict.targs[info.typeParamIdx]
		method := typecheck.Expr(ir.NewSelectorExpr(pos, ir.OXDOT, ir.TypeNode(typeParam), info.method)).(*ir.SelectorExpr)
		assert(method.Op() == ir.OMETHEXPR)
		rsym := method.FuncName().Linksym()
		assert(rsym.ABI() == obj.ABIInternal) // must be ABIInternal; see ir.OCFUNC in ssagen/ssa.go
		ot = objw.SymPtr(lsym, ot, rsym, 0)
	}
	assertOffset("subdictionaries", dict.subdictsOffset())
	for _, info := range dict.subdicts {
		explicits := pr.typListIdx(info.explicits, dict)
		// Careful: Due to subdictionary cycles, name may not be fully
		// initialized yet.
		name := pr.objDictName(info.idx, dict.targs, explicits)
		ot = objw.SymPtr(lsym, ot, name.Linksym(), 0)
	}
	assertOffset("rtypes", dict.rtypesOffset())
	for _, info := range dict.rtypes {
		typ := pr.typIdx(info, dict, true)
		ot = objw.SymPtr(lsym, ot, reflectdata.TypeLinksym(typ), 0)
		// TODO(mdempsky): Double check this.
		reflectdata.MarkTypeUsedInInterface(typ, lsym)
	// For each (typ, iface) pair, we write *runtime._type pointers
	// for typ and iface, as well as the *runtime.itab pointer for the
	// pair. This is wasteful, but it simplifies worrying about tricky
	// cases like instantiating type parameters with interface types.
	//
	// TODO(mdempsky): Add the needed *runtime._type pointers into the
	// rtypes section above instead, and omit itabs entries when we
	// statically know it won't be needed.
	assertOffset("itabs", dict.itabsOffset())
	for _, info := range dict.itabs {
		typ := pr.typIdx(info.typ, dict, true)
		iface := pr.typIdx(info.iface, dict, true)

		if !iface.IsInterface() {
			ot += 3 * types.PtrSize
			continue
		}

		ot = objw.SymPtr(lsym, ot, reflectdata.TypeLinksym(typ), 0)
		ot = objw.SymPtr(lsym, ot, reflectdata.TypeLinksym(iface), 0)
		if !typ.IsInterface() && !iface.IsEmptyInterface() {
			ot = objw.SymPtr(lsym, ot, reflectdata.ITabLsym(typ, iface), 0)
		} else {
			ot += types.PtrSize
		}

		// TODO(mdempsky): Double check this.
		reflectdata.MarkTypeUsedInInterface(typ, lsym)
		reflectdata.MarkTypeUsedInInterface(iface, lsym)
	}

	objw.Global(lsym, int32(ot), obj.DUPOK|obj.RODATA)

	name.SetType(dict.varType())
	name.SetTypecheck(1)

	return name
}

// typeParamMethodExprsOffset returns the offset of the runtime
// dictionary's type parameter method expressions section, in words.
func (dict *readerDict) typeParamMethodExprsOffset() int {
	return 0
}

// subdictsOffset returns the offset of the runtime dictionary's
// subdictionary section, in words.
func (dict *readerDict) subdictsOffset() int {
	return dict.typeParamMethodExprsOffset() + len(dict.typeParamMethodExprs)
}

// rtypesOffset returns the offset of the runtime dictionary's rtypes
// section, in words.
func (dict *readerDict) rtypesOffset() int {
	return dict.subdictsOffset() + len(dict.subdicts)
}

// itabsOffset returns the offset of the runtime dictionary's itabs
// section, in words.
func (dict *readerDict) itabsOffset() int {
	return dict.rtypesOffset() + len(dict.rtypes)
// numWords returns the total number of words that comprise dict's
// runtime dictionary variable.
func (dict *readerDict) numWords() int64 {
	return int64(dict.itabsOffset() + 3*len(dict.itabs))
}

// varType returns the type of dict's runtime dictionary variable.
func (dict *readerDict) varType() *types.Type {
	return types.NewArray(types.Types[types.TUINTPTR], dict.numWords())
}

func (r *reader) funcargs(fn *ir.Func) {
	sig := fn.Nname.Type()

	if recv := sig.Recv(); recv != nil {
		r.funcarg(recv, recv.Sym, ir.PPARAM)
	}
	for _, param := range sig.Params().FieldSlice() {
		r.funcarg(param, param.Sym, ir.PPARAM)
	}

	for i, param := range sig.Results().FieldSlice() {
		sym := types.OrigSym(param.Sym)

		if sym == nil || sym.IsBlank() {
			prefix := "~r"
			if r.inlCall != nil {
				prefix = "~R"
			} else if sym != nil {
				prefix = "~b"
			}
			sym = typecheck.LookupNum(prefix, i)
		}

		r.funcarg(param, sym, ir.PPARAMOUT)
	}
}

func (r *reader) funcarg(param *types.Field, sym *types.Sym, ctxt ir.Class) {
	if sym == nil {
		assert(ctxt == ir.PPARAM)
		if r.inlCall != nil {
			r.inlvars.Append(ir.BlankNode)
		}
		return
	}

	name := ir.NewNameAt(r.inlPos(param.Pos), sym)
	setType(name, param.Type)
	r.addLocal(name, ctxt)

	if r.inlCall == nil {
		if !r.funarghack {
			param.Sym = sym
			param.Nname = name
		}
	} else {
		if ctxt == ir.PPARAMOUT {
			r.retvars.Append(name)
		} else {
			r.inlvars.Append(name)
		}
	}
}

func (r *reader) addLocal(name *ir.Name, ctxt ir.Class) {
	assert(ctxt == ir.PAUTO || ctxt == ir.PPARAM || ctxt == ir.PPARAMOUT)

	if name.Sym().Name == dictParamName {
		r.dictParam = name
	} else {
			r.Sync(pkgbits.SyncAddLocal)
			if r.p.SyncMarkers() {
				want := r.Int()
				if have := len(r.locals); have != want {
					base.FatalfAt(name.Pos(), "locals table has desynced")
				}
		r.locals = append(r.locals, name)
	}

	name.SetUsed(true)

	// TODO(mdempsky): Move earlier.
	if ir.IsBlank(name) {
		return
	}

	if r.inlCall != nil {
		if ctxt == ir.PAUTO {
			name.SetInlLocal(true)
		} else {
			name.SetInlFormal(true)
			ctxt = ir.PAUTO
		}

		// TODO(mdempsky): Rethink this hack.
		if strings.HasPrefix(name.Sym().Name, "~") || base.Flag.GenDwarfInl == 0 {
			name.SetPos(r.inlCall.Pos())
			name.SetInlFormal(false)
			name.SetInlLocal(false)
		}
	}

	name.Class = ctxt
	name.Curfn = r.curfn

	r.curfn.Dcl = append(r.curfn.Dcl, name)

	if ctxt == ir.PAUTO {
		name.SetFrameOffset(0)
	}
}

func (r *reader) useLocal() *ir.Name {
	r.Sync(pkgbits.SyncUseObjLocal)
	if r.Bool() {
		return r.locals[r.Len()]
	return r.closureVars[r.Len()]
	r.Sync(pkgbits.SyncOpenScope)
	pos := r.pos()

	if base.Flag.Dwarf {
		r.scopeVars = append(r.scopeVars, len(r.curfn.Dcl))
		r.marker.Push(pos)
	}
}

func (r *reader) closeScope() {
	r.Sync(pkgbits.SyncCloseScope)
	r.lastCloseScopePos = r.pos()

	r.closeAnotherScope()
}

// closeAnotherScope is like closeScope, but it reuses the same mark
// position as the last closeScope call. This is useful for "for" and
// "if" statements, as their implicit blocks always end at the same
// position as an explicit block.
func (r *reader) closeAnotherScope() {
	r.Sync(pkgbits.SyncCloseAnotherScope)

	if base.Flag.Dwarf {
		scopeVars := r.scopeVars[len(r.scopeVars)-1]
		r.scopeVars = r.scopeVars[:len(r.scopeVars)-1]

		// Quirkish: noder decides which scopes to keep before
		// typechecking, whereas incremental typechecking during IR
		// construction can result in new autotemps being allocated. To
		// produce identical output, we ignore autotemps here for the
		// purpose of deciding whether to retract the scope.
		//
		// This is important for net/http/fcgi, because it contains:
		//
		//	var body io.ReadCloser
		//	if len(content) > 0 {
		//		body, req.pw = io.Pipe()
		//	} else { … }
		//
		// Notably, io.Pipe is inlinable, and inlining it introduces a ~R0
		// variable at the call site.
		//
		// Noder does not preserve the scope where the io.Pipe() call
		// resides, because it doesn't contain any declared variables in
		// source. So the ~R0 variable ends up being assigned to the
		// enclosing scope instead.
		//
		// However, typechecking this assignment also introduces
		// autotemps, because io.Pipe's results need conversion before
		// they can be assigned to their respective destination variables.
		//
		// TODO(mdempsky): We should probably just keep all scopes, and
		// let dwarfgen take care of pruning them instead.
		retract := true
		for _, n := range r.curfn.Dcl[scopeVars:] {
			if !n.AutoTemp() {
				retract = false
				break
			}
		}

		if retract {
			// no variables were declared in this scope, so we can retract it.
			r.marker.Unpush()
		} else {
			r.marker.Pop(r.lastCloseScopePos)
		}
	}
}

// @@@ Statements

func (r *reader) stmt() ir.Node {
	switch stmts := r.stmts(); len(stmts) {
	case 0:
		return nil
	case 1:
		return stmts[0]
	default:
		return ir.NewBlockStmt(stmts[0].Pos(), stmts)
	}
}

func (r *reader) stmts() []ir.Node {
	r.Sync(pkgbits.SyncStmts)
		tag := codeStmt(r.Code(pkgbits.SyncStmt1))
			r.Sync(pkgbits.SyncStmtsEnd)
			return res
		}

		if n := r.stmt1(tag, &res); n != nil {
		}
	}
}

func (r *reader) stmt1(tag codeStmt, out *ir.Nodes) ir.Node {
	var label *types.Sym
	if n := len(*out); n > 0 {
		if ls, ok := (*out)[n-1].(*ir.LabelStmt); ok {
			label = ls.Label
		}
	}

	switch tag {
	default:
		panic("unexpected statement")

	case stmtAssign:
		pos := r.pos()

		if len(rhs) == 0 {
			for _, name := range names {
				as := ir.NewAssignStmt(pos, name, nil)
				as.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, name))
			}
			return nil
		}

		if len(lhs) == 1 && len(rhs) == 1 {
			n := ir.NewAssignStmt(pos, lhs[0], rhs[0])
			n.Def = r.initDefn(n, names)
			return n
		}

		n := ir.NewAssignListStmt(pos, ir.OAS2, lhs, rhs)
		n.Def = r.initDefn(n, names)
		return n

	case stmtAssignOp:
		op := r.op()
		lhs := r.expr()
		pos := r.pos()
		rhs := r.expr()
		return ir.NewAssignOpStmt(pos, op, lhs, rhs)

	case stmtIncDec:
		op := r.op()
		lhs := r.expr()
		pos := r.pos()
		n := ir.NewAssignOpStmt(pos, op, lhs, ir.NewBasicLit(pos, one))
		n.IncDec = true
		return n

	case stmtBlock:
		out.Append(r.blockStmt()...)
		return nil

	case stmtBranch:
		pos := r.pos()
		op := r.op()
		sym := r.optLabel()
		return ir.NewBranchStmt(pos, op, sym)

	case stmtCall:
		pos := r.pos()
		op := r.op()
		call := r.expr()
		return ir.NewGoDeferStmt(pos, op, call)

	case stmtExpr:
		return r.expr()

	case stmtFor:
		return r.forStmt(label)

	case stmtIf:
		return r.ifStmt()

	case stmtLabel:
		pos := r.pos()
		sym := r.label()
		return ir.NewLabelStmt(pos, sym)

	case stmtReturn:
		pos := r.pos()
		return ir.NewReturnStmt(pos, results)

	case stmtSelect:
		return r.selectStmt(label)

	case stmtSend:
		pos := r.pos()
		ch := r.expr()
		value := r.expr()
		return ir.NewSendStmt(pos, ch, value)

	case stmtSwitch:
		return r.switchStmt(label)
	}
}

func (r *reader) assignList() ([]*ir.Name, []ir.Node) {
	lhs := make([]ir.Node, r.Len())
	var names []*ir.Name

	for i := range lhs {
		expr, def := r.assign()
		lhs[i] = expr
		if def {
			names = append(names, expr.(*ir.Name))
// assign returns an assignee expression. It also reports whether the
// returned expression is a newly declared variable.
func (r *reader) assign() (ir.Node, bool) {
	switch tag := codeAssign(r.Code(pkgbits.SyncAssign)); tag {
	default:
		panic("unhandled assignee expression")

	case assignBlank:
		return typecheck.AssignExpr(ir.BlankNode), false

	case assignDef:
		pos := r.pos()
		_, sym := r.localIdent()
		typ := r.typ()

		name := ir.NewNameAt(pos, sym)
		setType(name, typ)
		r.addLocal(name, ir.PAUTO)
		return name, true

	case assignExpr:
		return r.expr(), false
	}
}

func (r *reader) blockStmt() []ir.Node {
	r.Sync(pkgbits.SyncBlockStmt)
	r.openScope()
	stmts := r.stmts()
	r.closeScope()
	return stmts
}

func (r *reader) forStmt(label *types.Sym) ir.Node {
	r.Sync(pkgbits.SyncForStmt)
		rang := ir.NewRangeStmt(pos, nil, nil, nil, nil)
		rang.Label = label
		if len(lhs) >= 1 {
			rang.Key = lhs[0]
			if len(lhs) >= 2 {
				rang.Value = lhs[1]
			}
		}
		rang.Def = r.initDefn(rang, names)
		rang.X = r.expr()
		if rang.X.Type().IsMap() {
			rang.RType = r.rtype(pos)
		}
		if rang.Key != nil && !ir.IsBlank(rang.Key) {
			rang.KeyTypeWord, rang.KeySrcRType = r.convRTTI(pos)
		}
		if rang.Value != nil && !ir.IsBlank(rang.Value) {
			rang.ValueTypeWord, rang.ValueSrcRType = r.convRTTI(pos)
		rang.Body = r.blockStmt()
		r.closeAnotherScope()

		return rang
	}

	pos := r.pos()
	init := r.stmt()
	post := r.stmt()
	body := r.blockStmt()
	r.closeAnotherScope()

	stmt := ir.NewForStmt(pos, init, cond, post, body)
	stmt.Label = label
	return stmt
}

func (r *reader) ifStmt() ir.Node {
	r.Sync(pkgbits.SyncIfStmt)
	r.openScope()
	pos := r.pos()
	init := r.stmts()
	cond := r.expr()
	then := r.blockStmt()
	els := r.stmts()
	n := ir.NewIfStmt(pos, cond, then, els)
	n.SetInit(init)
	r.closeAnotherScope()
	return n
}

func (r *reader) selectStmt(label *types.Sym) ir.Node {
	r.Sync(pkgbits.SyncSelectStmt)
	clauses := make([]*ir.CommClause, r.Len())
	for i := range clauses {
		if i > 0 {
			r.closeScope()
		}
		r.openScope()

		pos := r.pos()
		comm := r.stmt()
		body := r.stmts()

		// "case i = <-c: ..." may require an implicit conversion (e.g.,
		// see fixedbugs/bug312.go). Currently, typecheck throws away the
		// implicit conversion and relies on it being reinserted later,
		// but that would lose any explicit RTTI operands too. To preserve
		// RTTI, we rewrite this as "case tmp := <-c: i = tmp; ...".
		if as, ok := comm.(*ir.AssignStmt); ok && as.Op() == ir.OAS && !as.Def {
			if conv, ok := as.Y.(*ir.ConvExpr); ok && conv.Op() == ir.OCONVIFACE {
				base.AssertfAt(conv.Implicit(), conv.Pos(), "expected implicit conversion: %v", conv)

				recv := conv.X
				base.AssertfAt(recv.Op() == ir.ORECV, recv.Pos(), "expected receive expression: %v", recv)

				tmp := r.temp(pos, recv.Type())

				// Replace comm with `tmp := <-c`.
				tmpAs := ir.NewAssignStmt(pos, tmp, recv)
				tmpAs.Def = true
				tmpAs.PtrInit().Append(ir.NewDecl(pos, ir.ODCL, tmp))
				comm = tmpAs

				// Change original assignment to `i = tmp`, and prepend to body.
				conv.X = tmp
				body = append([]ir.Node{as}, body...)
			}
		}

		// multiExpr will have desugared a comma-ok receive expression
		// into a separate statement. However, the rest of the compiler
		// expects comm to be the OAS2RECV statement itself, so we need to
		// shuffle things around to fit that pattern.
		if as2, ok := comm.(*ir.AssignListStmt); ok && as2.Op() == ir.OAS2 {
			init := ir.TakeInit(as2.Rhs[0])
			base.AssertfAt(len(init) == 1 && init[0].Op() == ir.OAS2RECV, as2.Pos(), "unexpected assignment: %+v", as2)

			comm = init[0]
			body = append([]ir.Node{as2}, body...)
		}

		clauses[i] = ir.NewCommStmt(pos, comm, body)
	}
	if len(clauses) > 0 {
		r.closeScope()
	}
	n := ir.NewSelectStmt(pos, clauses)
	n.Label = label
	return n
}

func (r *reader) switchStmt(label *types.Sym) ir.Node {
	r.Sync(pkgbits.SyncSwitchStmt)

	r.openScope()
	pos := r.pos()
	init := r.stmt()
	var ident *ir.Ident
	var iface *types.Type
			sym := typecheck.Lookup(r.String())
		tag = ir.NewTypeSwitchGuard(pos, ident, x)
	} else {
	clauses := make([]*ir.CaseClause, r.Len())
	for i := range clauses {
		if i > 0 {
			r.closeScope()
		}
		r.openScope()

		pos := r.pos()
		if iface != nil {
			cases = make([]ir.Node, r.Len())
			if len(cases) == 0 {
				cases = nil // TODO(mdempsky): Unclear if this matters.
			}
			for i := range cases {
				if r.Bool() { // case nil
					cases[i] = typecheck.Expr(types.BuiltinPkg.Lookup("nil").Def.(*ir.NilExpr))
				} else {
					cases[i] = r.exprType()
				}
			// For `switch { case any(true): }` (e.g., issue 3980 in
			// test/switch.go), the backend still creates a mixed bool/any
			// comparison, and we need to explicitly supply the RTTI for the
			// comparison.
			//
			// TODO(mdempsky): Change writer.go to desugar "switch {" into
			// "switch true {", which we already handle correctly.
			if tag == nil {
				for i, cas := range cases {
					if cas.Type().IsEmptyInterface() {
						for len(rtypes) < i {
							rtypes = append(rtypes, nil)
						}
						rtypes = append(rtypes, reflectdata.TypePtrAt(cas.Pos(), types.Types[types.TBOOL]))

		clause := ir.NewCaseStmt(pos, cases, nil)
			name := ir.NewNameAt(pos, ident.Sym())
			r.addLocal(name, ir.PAUTO)
			clause.Var = name
		}

		clause.Body = r.stmts()
		clauses[i] = clause
	}
	if len(clauses) > 0 {
		r.closeScope()
	}
	r.closeScope()

	n := ir.NewSwitchStmt(pos, tag, clauses)
	n.Label = label
	if init != nil {
		n.SetInit([]ir.Node{init})
	}
	return n
}

func (r *reader) label() *types.Sym {
	r.Sync(pkgbits.SyncLabel)
	name := r.String()
	if r.inlCall != nil {
		name = fmt.Sprintf("~%s·%d", name, inlgen)
	}
	return typecheck.Lookup(name)
}

func (r *reader) optLabel() *types.Sym {
	r.Sync(pkgbits.SyncOptLabel)
	if r.Bool() {
		return r.label()
	}
	return nil
}

// initDefn marks the given names as declared by defn and populates
// its Init field with ODCL nodes. It then reports whether any names
// were so declared, which can be used to initialize defn.Def.
func (r *reader) initDefn(defn ir.InitNode, names []*ir.Name) bool {
	if len(names) == 0 {
		return false
	}

	init := make([]ir.Node, len(names))
	for i, name := range names {
		name.Defn = defn
		init[i] = ir.NewDecl(name.Pos(), ir.ODCL, name)
	}
	defn.SetInit(init)
	return true
}

// @@@ Expressions

// expr reads and returns a typechecked expression.
func (r *reader) expr() (res ir.Node) {
	defer func() {
		if res != nil && res.Typecheck() == 0 {
			base.FatalfAt(res.Pos(), "%v missed typecheck", res)
		}
	}()
	switch tag := codeExpr(r.Code(pkgbits.SyncExpr)); tag {
	default:
		panic("unhandled expression")

	case exprLocal:
		// Callee instead of Expr allows builtins
		// TODO(mdempsky): Handle builtins directly in exprCall, like method calls?
		return typecheck.Callee(r.obj())
		pos := r.pos()
		wrapperFn, baseFn, dictPtr := r.funcInst(pos)
		if wrapperFn != nil {
			return wrapperFn
		}
		return r.curry(pos, false, baseFn, dictPtr, nil)
	case exprConst:
		pos := r.pos()
		val := FixValue(typ, r.Value())
		return typecheck.Expr(OrigConst(pos, typ, val, op, orig))
	case exprNil:
		pos := r.pos()
		typ := r.typ()
		return Nil(pos, typ)

	case exprCompLit:
		return r.compLit()

	case exprFuncLit:
		return r.funcLit()

	case exprFieldVal:
		x := r.expr()
		pos := r.pos()
		_, sym := r.selector()
		return typecheck.Expr(ir.NewSelectorExpr(pos, ir.OXDOT, x, sym)).(*ir.SelectorExpr)

	case exprMethodVal:
		wrapperFn, baseFn, dictPtr := r.methodExpr()

		// For simple wrapperFn values, the existing machinery for creating
		// and deduplicating wrapperFn value wrappers still works fine.
		if wrapperFn, ok := wrapperFn.(*ir.SelectorExpr); ok && wrapperFn.Op() == ir.OMETHEXPR {
			// The receiver expression we constructed may have a shape type.
			// For example, in fixedbugs/issue54343.go, `New[int]()` is
			// constructed as `New[go.shape.int](&.dict.New[int])`, which
			// has type `*T[go.shape.int]`, not `*T[int]`.
			//
			// However, the method we want to select here is `(*T[int]).M`,
			// not `(*T[go.shape.int]).M`, so we need to manually convert
			// the type back so that the OXDOT resolves correctly.
			//
			// TODO(mdempsky): Logically it might make more sense for
			// exprCall to take responsibility for setting a non-shaped
			// result type, but this is the only place where we care
			// currently. And only because existing ir.OMETHVALUE backend
			// code relies on n.X.Type() instead of n.Selection.Recv().Type
			// (because the latter is types.FakeRecvType() in the case of
			// interface method values).
			//
			if recv.Type().HasShape() {
				typ := wrapperFn.Type().Params().Field(0).Type
				if !types.Identical(typ, recv.Type()) {
					base.FatalfAt(wrapperFn.Pos(), "receiver %L does not match %L", recv, wrapperFn)
				}
				recv = typecheck.Expr(ir.NewConvExpr(recv.Pos(), ir.OCONVNOP, typ, recv))
			}
			n := typecheck.Expr(ir.NewSelectorExpr(pos, ir.OXDOT, recv, wrapperFn.Sel)).(*ir.SelectorExpr)
			assert(n.Selection == wrapperFn.Selection)

			wrapper := methodValueWrapper{
				rcvr:   n.X.Type(),
				method: n.Selection,
			}

			if r.importedDef() {
				haveMethodValueWrappers = append(haveMethodValueWrappers, wrapper)
			} else {
				needMethodValueWrappers = append(needMethodValueWrappers, wrapper)
			}
			return n

		// For more complicated method expressions, we construct a
		// function literal wrapper.
		return r.curry(pos, true, baseFn, recv, dictPtr)
		recv := r.typ()

		implicits := make([]int, r.Len())
		for i := range implicits {
			implicits[i] = r.Len()
		}
		var deref, addr bool
		if r.Bool() {
			deref = true
		} else if r.Bool() {
			addr = true
		}

		wrapperFn, baseFn, dictPtr := r.methodExpr()
		// If we already have a wrapper and don't need to do anything with
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