--- /dev/null
+// 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
+}
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