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// Copyright 2013 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 ssa
// This file implements the CREATE phase of SSA construction.
// See builder.go for explanation.
import (
"fmt"
"go/ast"
"go/token"
"go/types"
"os"
"sync"
"golang.org/x/tools/internal/versions"
)
// NewProgram returns a new SSA Program.
//
// mode controls diagnostics and checking during SSA construction.
//
// To construct an SSA program:
//
// - Call NewProgram to create an empty Program.
// - Call CreatePackage providing typed syntax for each package
// you want to build, and call it with types but not
// syntax for each of those package's direct dependencies.
// - Call [Package.Build] on each syntax package you wish to build,
// or [Program.Build] to build all of them.
//
// See the Example tests for simple examples.
func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
return &Program{
Fset: fset,
imported: make(map[string]*Package),
packages: make(map[*types.Package]*Package),
mode: mode,
canon: newCanonizer(),
ctxt: types.NewContext(),
}
}
// memberFromObject populates package pkg with a member for the
// typechecker object obj.
//
// For objects from Go source code, syntax is the associated syntax
// tree (for funcs and vars only) and goversion defines the
// appropriate interpretation; they will be used during the build
// phase.
func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node, goversion string) {
name := obj.Name()
switch obj := obj.(type) {
case *types.Builtin:
if pkg.Pkg != types.Unsafe {
panic("unexpected builtin object: " + obj.String())
}
case *types.TypeName:
if name != "_" {
pkg.Members[name] = &Type{
object: obj,
pkg: pkg,
}
}
case *types.Const:
c := &NamedConst{
object: obj,
Value: NewConst(obj.Val(), obj.Type()),
pkg: pkg,
}
pkg.objects[obj] = c
if name != "_" {
pkg.Members[name] = c
}
case *types.Var:
g := &Global{
Pkg: pkg,
name: name,
object: obj,
typ: types.NewPointer(obj.Type()), // address
pos: obj.Pos(),
}
pkg.objects[obj] = g
if name != "_" {
pkg.Members[name] = g
}
case *types.Func:
sig := obj.Type().(*types.Signature)
if sig.Recv() == nil && name == "init" {
pkg.ninit++
name = fmt.Sprintf("init#%d", pkg.ninit)
}
fn := createFunction(pkg.Prog, obj, name, syntax, pkg.info, goversion)
fn.Pkg = pkg
pkg.created = append(pkg.created, fn)
pkg.objects[obj] = fn
if name != "_" && sig.Recv() == nil {
pkg.Members[name] = fn // package-level function
}
default: // (incl. *types.Package)
panic("unexpected Object type: " + obj.String())
}
}
// createFunction creates a function or method. It supports both
// CreatePackage (with or without syntax) and the on-demand creation
// of methods in non-created packages based on their types.Func.
func createFunction(prog *Program, obj *types.Func, name string, syntax ast.Node, info *types.Info, goversion string) *Function {
sig := obj.Type().(*types.Signature)
// Collect type parameters.
var tparams *types.TypeParamList
if rtparams := sig.RecvTypeParams(); rtparams.Len() > 0 {
tparams = rtparams // method of generic type
} else if sigparams := sig.TypeParams(); sigparams.Len() > 0 {
tparams = sigparams // generic function
}
/* declared function/method (from syntax or export data) */
fn := &Function{
name: name,
object: obj,
Signature: sig,
build: (*builder).buildFromSyntax,
syntax: syntax,
info: info,
goversion: goversion,
pos: obj.Pos(),
Pkg: nil, // may be set by caller
Prog: prog,
typeparams: tparams,
}
if fn.syntax == nil {
fn.Synthetic = "from type information"
fn.build = (*builder).buildParamsOnly
}
if tparams.Len() > 0 {
fn.generic = new(generic)
}
return fn
}
// membersFromDecl populates package pkg with members for each
// typechecker object (var, func, const or type) associated with the
// specified decl.
func membersFromDecl(pkg *Package, decl ast.Decl, goversion string) {
switch decl := decl.(type) {
case *ast.GenDecl: // import, const, type or var
switch decl.Tok {
case token.CONST:
for _, spec := range decl.Specs {
for _, id := range spec.(*ast.ValueSpec).Names {
memberFromObject(pkg, pkg.info.Defs[id], nil, "")
}
}
case token.VAR:
for _, spec := range decl.Specs {
for _, rhs := range spec.(*ast.ValueSpec).Values {
pkg.initVersion[rhs] = goversion
}
for _, id := range spec.(*ast.ValueSpec).Names {
memberFromObject(pkg, pkg.info.Defs[id], spec, goversion)
}
}
case token.TYPE:
for _, spec := range decl.Specs {
id := spec.(*ast.TypeSpec).Name
memberFromObject(pkg, pkg.info.Defs[id], nil, "")
}
}
case *ast.FuncDecl:
id := decl.Name
memberFromObject(pkg, pkg.info.Defs[id], decl, goversion)
}
}
// CreatePackage creates and returns an SSA Package from the
// specified type-checked, error-free file ASTs, and populates its
// Members mapping.
//
// importable determines whether this package should be returned by a
// subsequent call to ImportedPackage(pkg.Path()).
//
// The real work of building SSA form for each function is not done
// until a subsequent call to Package.Build.
//
// CreatePackage should not be called after building any package in
// the program.
func (prog *Program) CreatePackage(pkg *types.Package, files []*ast.File, info *types.Info, importable bool) *Package {
// TODO(adonovan): assert that no package has yet been built.
if pkg == nil {
panic("nil pkg") // otherwise pkg.Scope below returns types.Universe!
}
p := &Package{
Prog: prog,
Members: make(map[string]Member),
objects: make(map[types.Object]Member),
Pkg: pkg,
syntax: info != nil,
// transient values (cleared after Package.Build)
info: info,
files: files,
initVersion: make(map[ast.Expr]string),
}
/* synthesized package initializer */
p.init = &Function{
name: "init",
Signature: new(types.Signature),
Synthetic: "package initializer",
Pkg: p,
Prog: prog,
build: (*builder).buildPackageInit,
info: p.info,
goversion: "", // See Package.build for details.
}
p.Members[p.init.name] = p.init
p.created = append(p.created, p.init)
// Allocate all package members: vars, funcs, consts and types.
if len(files) > 0 {
// Go source package.
for _, file := range files {
goversion := versions.Lang(versions.FileVersion(p.info, file))
for _, decl := range file.Decls {
membersFromDecl(p, decl, goversion)
}
}
} else {
// GC-compiled binary package (or "unsafe")
// No code.
// No position information.
scope := p.Pkg.Scope()
for _, name := range scope.Names() {
obj := scope.Lookup(name)
memberFromObject(p, obj, nil, "")
if obj, ok := obj.(*types.TypeName); ok {
// No Unalias: aliases should not duplicate methods.
if named, ok := obj.Type().(*types.Named); ok {
for i, n := 0, named.NumMethods(); i < n; i++ {
memberFromObject(p, named.Method(i), nil, "")
}
}
}
}
}
if prog.mode&BareInits == 0 {
// Add initializer guard variable.
initguard := &Global{
Pkg: p,
name: "init$guard",
typ: types.NewPointer(tBool),
}
p.Members[initguard.Name()] = initguard
}
if prog.mode&GlobalDebug != 0 {
p.SetDebugMode(true)
}
if prog.mode&PrintPackages != 0 {
printMu.Lock()
p.WriteTo(os.Stdout)
printMu.Unlock()
}
if importable {
prog.imported[p.Pkg.Path()] = p
}
prog.packages[p.Pkg] = p
return p
}
// printMu serializes printing of Packages/Functions to stdout.
var printMu sync.Mutex
// AllPackages returns a new slice containing all packages created by
// prog.CreatePackage in unspecified order.
func (prog *Program) AllPackages() []*Package {
pkgs := make([]*Package, 0, len(prog.packages))
for _, pkg := range prog.packages {
pkgs = append(pkgs, pkg)
}
return pkgs
}
// ImportedPackage returns the importable Package whose PkgPath
// is path, or nil if no such Package has been created.
//
// A parameter to CreatePackage determines whether a package should be
// considered importable. For example, no import declaration can resolve
// to the ad-hoc main package created by 'go build foo.go'.
//
// TODO(adonovan): rethink this function and the "importable" concept;
// most packages are importable. This function assumes that all
// types.Package.Path values are unique within the ssa.Program, which is
// false---yet this function remains very convenient.
// Clients should use (*Program).Package instead where possible.
// SSA doesn't really need a string-keyed map of packages.
//
// Furthermore, the graph of packages may contain multiple variants
// (e.g. "p" vs "p as compiled for q.test"), and each has a different
// view of its dependencies.
func (prog *Program) ImportedPackage(path string) *Package {
return prog.imported[path]
}
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