271 lines
8.4 KiB
Go
271 lines
8.4 KiB
Go
// 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 ir
|
|
|
|
// This file defines utilities for working with source positions
|
|
// or source-level named entities ("objects").
|
|
|
|
// TODO(adonovan): test that {Value,Instruction}.Pos() positions match
|
|
// the originating syntax, as specified.
|
|
|
|
import (
|
|
"go/ast"
|
|
"go/token"
|
|
"go/types"
|
|
)
|
|
|
|
// EnclosingFunction returns the function that contains the syntax
|
|
// node denoted by path.
|
|
//
|
|
// Syntax associated with package-level variable specifications is
|
|
// enclosed by the package's init() function.
|
|
//
|
|
// Returns nil if not found; reasons might include:
|
|
// - the node is not enclosed by any function.
|
|
// - the node is within an anonymous function (FuncLit) and
|
|
// its IR function has not been created yet
|
|
// (pkg.Build() has not yet been called).
|
|
//
|
|
func EnclosingFunction(pkg *Package, path []ast.Node) *Function {
|
|
// Start with package-level function...
|
|
fn := findEnclosingPackageLevelFunction(pkg, path)
|
|
if fn == nil {
|
|
return nil // not in any function
|
|
}
|
|
|
|
// ...then walk down the nested anonymous functions.
|
|
n := len(path)
|
|
outer:
|
|
for i := range path {
|
|
if lit, ok := path[n-1-i].(*ast.FuncLit); ok {
|
|
for _, anon := range fn.AnonFuncs {
|
|
if anon.Pos() == lit.Type.Func {
|
|
fn = anon
|
|
continue outer
|
|
}
|
|
}
|
|
// IR function not found:
|
|
// - package not yet built, or maybe
|
|
// - builder skipped FuncLit in dead block
|
|
// (in principle; but currently the Builder
|
|
// generates even dead FuncLits).
|
|
return nil
|
|
}
|
|
}
|
|
return fn
|
|
}
|
|
|
|
// HasEnclosingFunction returns true if the AST node denoted by path
|
|
// is contained within the declaration of some function or
|
|
// package-level variable.
|
|
//
|
|
// Unlike EnclosingFunction, the behaviour of this function does not
|
|
// depend on whether IR code for pkg has been built, so it can be
|
|
// used to quickly reject check inputs that will cause
|
|
// EnclosingFunction to fail, prior to IR building.
|
|
//
|
|
func HasEnclosingFunction(pkg *Package, path []ast.Node) bool {
|
|
return findEnclosingPackageLevelFunction(pkg, path) != nil
|
|
}
|
|
|
|
// findEnclosingPackageLevelFunction returns the Function
|
|
// corresponding to the package-level function enclosing path.
|
|
//
|
|
func findEnclosingPackageLevelFunction(pkg *Package, path []ast.Node) *Function {
|
|
if n := len(path); n >= 2 { // [... {Gen,Func}Decl File]
|
|
switch decl := path[n-2].(type) {
|
|
case *ast.GenDecl:
|
|
if decl.Tok == token.VAR && n >= 3 {
|
|
// Package-level 'var' initializer.
|
|
return pkg.init
|
|
}
|
|
|
|
case *ast.FuncDecl:
|
|
// Declared function/method.
|
|
fn := findNamedFunc(pkg, decl.Pos())
|
|
if fn == nil && decl.Recv == nil && decl.Name.Name == "init" {
|
|
// Hack: return non-nil when IR is not yet
|
|
// built so that HasEnclosingFunction works.
|
|
return pkg.init
|
|
}
|
|
return fn
|
|
}
|
|
}
|
|
return nil // not in any function
|
|
}
|
|
|
|
// findNamedFunc returns the named function whose FuncDecl.Ident is at
|
|
// position pos.
|
|
//
|
|
func findNamedFunc(pkg *Package, pos token.Pos) *Function {
|
|
for _, fn := range pkg.Functions {
|
|
if fn.Pos() == pos {
|
|
return fn
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// ValueForExpr returns the IR Value that corresponds to non-constant
|
|
// expression e.
|
|
//
|
|
// It returns nil if no value was found, e.g.
|
|
// - the expression is not lexically contained within f;
|
|
// - f was not built with debug information; or
|
|
// - e is a constant expression. (For efficiency, no debug
|
|
// information is stored for constants. Use
|
|
// go/types.Info.Types[e].Value instead.)
|
|
// - e is a reference to nil or a built-in function.
|
|
// - the value was optimised away.
|
|
//
|
|
// If e is an addressable expression used in an lvalue context,
|
|
// value is the address denoted by e, and isAddr is true.
|
|
//
|
|
// The types of e (or &e, if isAddr) and the result are equal
|
|
// (modulo "untyped" bools resulting from comparisons).
|
|
//
|
|
// (Tip: to find the ir.Value given a source position, use
|
|
// astutil.PathEnclosingInterval to locate the ast.Node, then
|
|
// EnclosingFunction to locate the Function, then ValueForExpr to find
|
|
// the ir.Value.)
|
|
//
|
|
func (f *Function) ValueForExpr(e ast.Expr) (value Value, isAddr bool) {
|
|
if f.debugInfo() { // (opt)
|
|
e = unparen(e)
|
|
for _, b := range f.Blocks {
|
|
for _, instr := range b.Instrs {
|
|
if ref, ok := instr.(*DebugRef); ok {
|
|
if ref.Expr == e {
|
|
return ref.X, ref.IsAddr
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
// --- Lookup functions for source-level named entities (types.Objects) ---
|
|
|
|
// Package returns the IR Package corresponding to the specified
|
|
// type-checker package object.
|
|
// It returns nil if no such IR package has been created.
|
|
//
|
|
func (prog *Program) Package(obj *types.Package) *Package {
|
|
return prog.packages[obj]
|
|
}
|
|
|
|
// packageLevelValue returns the package-level value corresponding to
|
|
// the specified named object, which may be a package-level const
|
|
// (*Const), var (*Global) or func (*Function) of some package in
|
|
// prog. It returns nil if the object is not found.
|
|
//
|
|
func (prog *Program) packageLevelValue(obj types.Object) Value {
|
|
if pkg, ok := prog.packages[obj.Pkg()]; ok {
|
|
return pkg.values[obj]
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// FuncValue returns the concrete Function denoted by the source-level
|
|
// named function obj, or nil if obj denotes an interface method.
|
|
//
|
|
// TODO(adonovan): check the invariant that obj.Type() matches the
|
|
// result's Signature, both in the params/results and in the receiver.
|
|
//
|
|
func (prog *Program) FuncValue(obj *types.Func) *Function {
|
|
fn, _ := prog.packageLevelValue(obj).(*Function)
|
|
return fn
|
|
}
|
|
|
|
// ConstValue returns the IR Value denoted by the source-level named
|
|
// constant obj.
|
|
//
|
|
func (prog *Program) ConstValue(obj *types.Const) *Const {
|
|
// TODO(adonovan): opt: share (don't reallocate)
|
|
// Consts for const objects and constant ast.Exprs.
|
|
|
|
// Universal constant? {true,false,nil}
|
|
if obj.Parent() == types.Universe {
|
|
return NewConst(obj.Val(), obj.Type())
|
|
}
|
|
// Package-level named constant?
|
|
if v := prog.packageLevelValue(obj); v != nil {
|
|
return v.(*Const)
|
|
}
|
|
return NewConst(obj.Val(), obj.Type())
|
|
}
|
|
|
|
// VarValue returns the IR Value that corresponds to a specific
|
|
// identifier denoting the source-level named variable obj.
|
|
//
|
|
// VarValue returns nil if a local variable was not found, perhaps
|
|
// because its package was not built, the debug information was not
|
|
// requested during IR construction, or the value was optimized away.
|
|
//
|
|
// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
|
|
// and that ident must resolve to obj.
|
|
//
|
|
// pkg is the package enclosing the reference. (A reference to a var
|
|
// always occurs within a function, so we need to know where to find it.)
|
|
//
|
|
// If the identifier is a field selector and its base expression is
|
|
// non-addressable, then VarValue returns the value of that field.
|
|
// For example:
|
|
// func f() struct {x int}
|
|
// f().x // VarValue(x) returns a *Field instruction of type int
|
|
//
|
|
// All other identifiers denote addressable locations (variables).
|
|
// For them, VarValue may return either the variable's address or its
|
|
// value, even when the expression is evaluated only for its value; the
|
|
// situation is reported by isAddr, the second component of the result.
|
|
//
|
|
// If !isAddr, the returned value is the one associated with the
|
|
// specific identifier. For example,
|
|
// var x int // VarValue(x) returns Const 0 here
|
|
// x = 1 // VarValue(x) returns Const 1 here
|
|
//
|
|
// It is not specified whether the value or the address is returned in
|
|
// any particular case, as it may depend upon optimizations performed
|
|
// during IR code generation, such as registerization, constant
|
|
// folding, avoidance of materialization of subexpressions, etc.
|
|
//
|
|
func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) (value Value, isAddr bool) {
|
|
// All references to a var are local to some function, possibly init.
|
|
fn := EnclosingFunction(pkg, ref)
|
|
if fn == nil {
|
|
return // e.g. def of struct field; IR not built?
|
|
}
|
|
|
|
id := ref[0].(*ast.Ident)
|
|
|
|
// Defining ident of a parameter?
|
|
if id.Pos() == obj.Pos() {
|
|
for _, param := range fn.Params {
|
|
if param.Object() == obj {
|
|
return param, false
|
|
}
|
|
}
|
|
}
|
|
|
|
// Other ident?
|
|
for _, b := range fn.Blocks {
|
|
for _, instr := range b.Instrs {
|
|
if dr, ok := instr.(*DebugRef); ok {
|
|
if dr.Pos() == id.Pos() {
|
|
return dr.X, dr.IsAddr
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// Defining ident of package-level var?
|
|
if v := prog.packageLevelValue(obj); v != nil {
|
|
return v.(*Global), true
|
|
}
|
|
|
|
return // e.g. debug info not requested, or var optimized away
|
|
}
|