Current File : //usr/local/go119/src/cmd/compile/internal/noder/unified.go
// 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"
"internal/pkgbits"
"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
// unified constructs the local package's Internal Representation (IR)
// from its syntax tree (AST).
//
// The pipeline contains 2 steps:
//
// 1. Generate the export data "stub".
//
// 2. Generate the IR from the export data above.
//
// The package data "stub" at step (1) contains everything from the local package,
// but nothing that has been imported. When we're actually writing out export data
// to the output files (see writeNewExport), we run the "linker", which:
//
// - Updates compiler extensions data (e.g. inlining cost, escape analysis results).
//
// - Handles re-exporting any transitive dependencies.
//
// - Prunes out any unnecessary details (e.g. non-inlineable functions, because any
// downstream importers only care about inlinable functions).
//
// The source files are typechecked twice: once before writing the export data
// using types2, and again after reading the export data using gc/typecheck.
// The duplication of work will go away once we only use the types2 type checker,
// removing the gc/typecheck step. For now, it is kept because:
//
// - It reduces the engineering costs in maintaining a fork of typecheck
// (e.g. no need to backport fixes like CL 327651).
//
// - It makes it easier to pass toolstash -cmp.
//
// - Historically, we would always re-run the typechecker after importing a package,
// even though we know the imported data is valid. It's not ideal, but it's
// not causing any problems either.
//
// - gc/typecheck is still in charge of some transformations, such as rewriting
// multi-valued function calls or transforming ir.OINDEX to ir.OINDEXMAP.
//
// Using the syntax tree with types2, which has a complete representation of generics,
// the unified IR has the full typed AST needed for introspection during step (1).
// In other words, we have all the necessary information to build the generic IR form
// (see writer.captureVars for an example).
func unified(noders []*noder) {
inline.NewInline = InlineCall
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()
types.LocalPkg.Height = 0 // reset so pkgReader.pkgIdx doesn't complain
target := typecheck.Target
typecheck.TypecheckAllowed = true
localPkgReader = newPkgReader(pkgbits.NewPkgDecoder(types.LocalPkg.Path, data))
readPackage(localPkgReader, types.LocalPkg)
r := localPkgReader.newReader(pkgbits.RelocMeta, pkgbits.PrivateRootIdx, pkgbits.SyncPrivate)
r.pkgInit(types.LocalPkg, target)
// Type-check any top-level assignments. We ignore non-assignments
// here because other declarations are typechecked as they're
// constructed.
for i, ndecls := 0, len(target.Decls); i < ndecls; i++ {
switch n := target.Decls[i]; n.Op() {
case ir.OAS, ir.OAS2:
target.Decls[i] = typecheck.Stmt(n)
}
}
readBodies(target)
// Check that nothing snuck past typechecking.
for _, n := range target.Decls {
if n.Typecheck() == 0 {
base.FatalfAt(n.Pos(), "missed typecheck: %v", n)
}
// For functions, check that at least their first statement (if
// any) was typechecked too.
if fn, ok := n.(*ir.Func); ok && len(fn.Body) != 0 {
if stmt := fn.Body[0]; stmt.Typecheck() == 0 {
base.FatalfAt(stmt.Pos(), "missed typecheck: %v", stmt)
}
}
}
base.ExitIfErrors() // just in case
}
// readBodies reads in bodies for any
func readBodies(target *ir.Package) {
// 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 fn.OClosure == nil && len(pri.dict.targs) != 0 {
target.Decls = append(target.Decls, fn)
}
}
todoBodies = nil
}
// writePkgStub type checks the given parsed source files,
// writes an export data package stub representing them,
// and returns the result.
func writePkgStub(noders []*noder) string {
m, pkg, info := checkFiles(noders)
pw := newPkgWriter(m, pkg, info)
pw.collectDecls(noders)
publicRootWriter := pw.newWriter(pkgbits.RelocMeta, pkgbits.SyncPublic)
privateRootWriter := pw.newWriter(pkgbits.RelocMeta, pkgbits.SyncPrivate)
assert(publicRootWriter.Idx == pkgbits.PublicRootIdx)
assert(privateRootWriter.Idx == pkgbits.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(pkgbits.SyncEOF)
w.Flush()
}
{
w := privateRootWriter
w.pkgInit(noders)
w.Flush()
}
var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
pw.DumpTo(&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(pkgbits.RelocMeta, pkgbits.PublicRootIdx, pkgbits.SyncPublic)
pkg := r.pkg()
base.Assertf(pkg == importpkg, "have package %q (%p), want package %q (%p)", pkg.Path, pkg, importpkg.Path, 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(pkgbits.SyncObject)
assert(!r.Bool())
idx := r.Reloc(pkgbits.RelocObj)
assert(r.Len() == 0)
path, name, code := r.p.PeekObj(idx)
if code != pkgbits.ObjStub {
objReader[types.NewPkg(path, "").Lookup(name)] = pkgReaderIndex{pr, idx, nil}
}
}
}
func writeUnifiedExport(out io.Writer) {
l := linker{
pw: pkgbits.NewPkgEncoder(base.Debug.SyncFrames),
pkgs: make(map[string]pkgbits.Index),
decls: make(map[*types.Sym]pkgbits.Index),
}
publicRootWriter := l.pw.NewEncoder(pkgbits.RelocMeta, pkgbits.SyncPublic)
assert(publicRootWriter.Idx == pkgbits.PublicRootIdx)
var selfPkgIdx pkgbits.Index
{
pr := localPkgReader
r := pr.NewDecoder(pkgbits.RelocMeta, pkgbits.PublicRootIdx, pkgbits.SyncPublic)
r.Sync(pkgbits.SyncPkg)
selfPkgIdx = l.relocIdx(pr, pkgbits.RelocPkg, r.Reloc(pkgbits.RelocPkg))
r.Bool() // has init
for i, n := 0, r.Len(); i < n; i++ {
r.Sync(pkgbits.SyncObject)
assert(!r.Bool())
idx := r.Reloc(pkgbits.RelocObj)
assert(r.Len() == 0)
xpath, xname, xtag := pr.PeekObj(idx)
assert(xpath == pr.PkgPath())
assert(xtag != pkgbits.ObjStub)
if types.IsExported(xname) {
l.relocIdx(pr, pkgbits.RelocObj, idx)
}
}
r.Sync(pkgbits.SyncEOF)
}
{
var idxs []pkgbits.Index
for _, idx := range l.decls {
idxs = append(idxs, idx)
}
sort.Slice(idxs, func(i, j int) bool { return idxs[i] < idxs[j] })
w := publicRootWriter
w.Sync(pkgbits.SyncPkg)
w.Reloc(pkgbits.RelocPkg, selfPkgIdx)
w.Bool(typecheck.Lookup(".inittask").Def != nil)
w.Len(len(idxs))
for _, idx := range idxs {
w.Sync(pkgbits.SyncObject)
w.Bool(false)
w.Reloc(pkgbits.RelocObj, idx)
w.Len(0)
}
w.Sync(pkgbits.SyncEOF)
w.Flush()
}
base.Ctxt.Fingerprint = l.pw.DumpTo(out)
}
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