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  • // UNREVIEWED
    
    // 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 (
    	"bytes"
    	"fmt"
    	"internal/goversion"
    	"io"
    	"runtime"
    	"sort"
    
    	"cmd/compile/internal/base"
    	"cmd/compile/internal/inline"
    	"cmd/compile/internal/ir"
    	"cmd/compile/internal/typecheck"
    	"cmd/compile/internal/types"
    	"cmd/compile/internal/types2"
    	"cmd/internal/src"
    )
    
    // localPkgReader holds the package reader used for reading the local
    // package. It exists so the unified IR linker can refer back to it
    // later.
    var localPkgReader *pkgReader
    
    // useUnifiedIR reports whether the unified IR frontend should be
    // used; and if so, uses it to construct the local package's IR.
    func useUnifiedIR(noders []*noder) {
    	inline.NewInline = InlineCall
    
    	if !quirksMode() {
    		writeNewExportFunc = writeNewExport
    	}
    
    	newReadImportFunc = func(data string, pkg1 *types.Pkg, check *types2.Checker, packages map[string]*types2.Package) (pkg2 *types2.Package, err error) {
    		pr := newPkgDecoder(pkg1.Path, data)
    
    		// Read package descriptors for both types2 and compiler backend.
    		readPackage(newPkgReader(pr), pkg1)
    		pkg2 = readPackage2(check, packages, pr)
    		return
    	}
    
    	data := writePkgStub(noders)
    
    	// We already passed base.Flag.Lang to types2 to handle validating
    	// the user's source code. Bump it up now to the current version and
    	// re-parse, so typecheck doesn't complain if we construct IR that
    	// utilizes newer Go features.
    	base.Flag.Lang = fmt.Sprintf("go1.%d", goversion.Version)
    	types.ParseLangFlag()
    
    	assert(types.LocalPkg.Path == "")
    	types.LocalPkg.Height = 0 // reset so pkgReader.pkgIdx doesn't complain
    	target := typecheck.Target
    
    	typecheck.TypecheckAllowed = true
    
    	localPkgReader = newPkgReader(newPkgDecoder(types.LocalPkg.Path, data))
    	readPackage(localPkgReader, types.LocalPkg)
    
    	r := localPkgReader.newReader(relocMeta, privateRootIdx, syncPrivate)
    	r.ext = r
    	r.pkgInit(types.LocalPkg, target)
    
    	// Don't use range--bodyIdx can add closures to todoBodies.
    	for len(todoBodies) > 0 {
    		// The order we expand bodies doesn't matter, so pop from the end
    		// to reduce todoBodies reallocations if it grows further.
    		fn := todoBodies[len(todoBodies)-1]
    		todoBodies = todoBodies[:len(todoBodies)-1]
    
    		pri, ok := bodyReader[fn]
    		assert(ok)
    		pri.funcBody(fn)
    
    		// Instantiated generic function: add to Decls for typechecking
    		// and compilation.
    		if len(pri.implicits) != 0 && fn.OClosure == nil {
    			target.Decls = append(target.Decls, fn)
    		}
    	}
    	todoBodies = nil
    
    	// Don't use range--typecheck can add closures to Target.Decls.
    	for i := 0; i < len(target.Decls); i++ {
    		target.Decls[i] = typecheck.Stmt(target.Decls[i])
    	}
    
    	// Don't use range--typecheck can add closures to Target.Decls.
    	for i := 0; i < len(target.Decls); i++ {
    		if fn, ok := target.Decls[i].(*ir.Func); ok {
    			if base.Flag.W > 1 {
    				s := fmt.Sprintf("\nbefore typecheck %v", fn)
    				ir.Dump(s, fn)
    			}
    			ir.CurFunc = fn
    			typecheck.Stmts(fn.Body)
    			if base.Flag.W > 1 {
    				s := fmt.Sprintf("\nafter typecheck %v", fn)
    				ir.Dump(s, fn)
    			}
    		}
    	}
    
    	base.ExitIfErrors() // just in case
    }
    
    // writePkgStub type checks the given parsed source files and then
    // returns
    func writePkgStub(noders []*noder) string {
    	m, pkg, info := checkFiles(noders)
    
    	pw := newPkgWriter(m, pkg, info)
    
    	pw.collectDecls(noders)
    
    	publicRootWriter := pw.newWriter(relocMeta, syncPublic)
    	privateRootWriter := pw.newWriter(relocMeta, syncPrivate)
    
    	assert(publicRootWriter.idx == publicRootIdx)
    	assert(privateRootWriter.idx == privateRootIdx)
    
    	{
    		w := publicRootWriter
    		w.pkg(pkg)
    		w.bool(false) // has init; XXX
    
    		scope := pkg.Scope()
    		names := scope.Names()
    		w.len(len(names))
    		for _, name := range scope.Names() {
    			w.obj(scope.Lookup(name), nil)
    		}
    
    		w.sync(syncEOF)
    		w.flush()
    	}
    
    	{
    		w := privateRootWriter
    		w.ext = w
    		w.pkgInit(noders)
    		w.flush()
    	}
    
    	var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
    	pw.dump(&sb)
    
    	// At this point, we're done with types2. Make sure the package is
    	// garbage collected.
    	freePackage(pkg)
    
    	return sb.String()
    }
    
    // freePackage ensures the given package is garbage collected.
    func freePackage(pkg *types2.Package) {
    
    	// The GC test below relies on a precise GC that runs finalizers as
    	// soon as objects are unreachable. Our implementation provides
    	// this, but other/older implementations may not (e.g., Go 1.4 does
    	// not because of #22350). To avoid imposing unnecessary
    	// restrictions on the GOROOT_BOOTSTRAP toolchain, we skip the test
    	// during bootstrapping.
    	if base.CompilerBootstrap {
    		return
    	}
    
    
    	// Set a finalizer on pkg so we can detect if/when it's collected.
    	done := make(chan struct{})
    	runtime.SetFinalizer(pkg, func(*types2.Package) { close(done) })
    
    	// Important: objects involved in cycles are not finalized, so zero
    	// out pkg to break its cycles and allow the finalizer to run.
    	*pkg = types2.Package{}
    
    	// It typically takes just 1 or 2 cycles to release pkg, but it
    	// doesn't hurt to try a few more times.
    	for i := 0; i < 10; i++ {
    		select {
    		case <-done:
    			return
    		default:
    			runtime.GC()
    		}
    	}
    
    	base.Fatalf("package never finalized")
    }
    
    func readPackage(pr *pkgReader, importpkg *types.Pkg) {
    	r := pr.newReader(relocMeta, publicRootIdx, syncPublic)
    
    	pkg := r.pkg()
    	assert(pkg == importpkg)
    
    	if r.bool() {
    		sym := pkg.Lookup(".inittask")
    		task := ir.NewNameAt(src.NoXPos, sym)
    		task.Class = ir.PEXTERN
    		sym.Def = task
    	}
    
    	for i, n := 0, r.len(); i < n; i++ {
    		r.sync(syncObject)
    		idx := r.reloc(relocObj)
    		assert(r.len() == 0)
    
    		path, name, code, _ := r.p.peekObj(idx)
    		if code != objStub {
    			objReader[types.NewPkg(path, "").Lookup(name)] = pkgReaderIndex{pr, idx, nil}
    		}
    	}
    }
    
    func writeNewExport(out io.Writer) {
    	l := linker{
    		pw: newPkgEncoder(),
    
    		pkgs:  make(map[string]int),
    		decls: make(map[*types.Sym]int),
    	}
    
    	publicRootWriter := l.pw.newEncoder(relocMeta, syncPublic)
    	assert(publicRootWriter.idx == publicRootIdx)
    
    	var selfPkgIdx int
    
    	{
    		pr := localPkgReader
    		r := pr.newDecoder(relocMeta, publicRootIdx, syncPublic)
    
    		r.sync(syncPkg)
    		selfPkgIdx = l.relocIdx(pr, relocPkg, r.reloc(relocPkg))
    
    		r.bool() // has init
    
    		for i, n := 0, r.len(); i < n; i++ {
    			r.sync(syncObject)
    			idx := r.reloc(relocObj)
    			assert(r.len() == 0)
    
    			xpath, xname, xtag, _ := pr.peekObj(idx)
    			assert(xpath == pr.pkgPath)
    			assert(xtag != objStub)
    
    			if types.IsExported(xname) {
    				l.relocIdx(pr, relocObj, idx)
    			}
    		}
    
    		r.sync(syncEOF)
    	}
    
    	{
    		var idxs []int
    		for _, idx := range l.decls {
    			idxs = append(idxs, idx)
    		}
    		sort.Ints(idxs)
    
    		w := publicRootWriter
    
    		w.sync(syncPkg)
    		w.reloc(relocPkg, selfPkgIdx)
    
    		w.bool(typecheck.Lookup(".inittask").Def != nil)
    
    		w.len(len(idxs))
    		for _, idx := range idxs {
    			w.sync(syncObject)
    			w.reloc(relocObj, idx)
    			w.len(0)
    		}
    
    		w.sync(syncEOF)
    		w.flush()
    	}
    
    	l.pw.dump(out)
    }