--- /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 irutil // import "honnef.co/go/tools/ir/irutil"
+
+import "honnef.co/go/tools/ir"
+
+// This file defines utilities for visiting the IR of
+// a Program.
+//
+// TODO(adonovan): test coverage.
+
+// AllFunctions finds and returns the set of functions potentially
+// needed by program prog, as determined by a simple linker-style
+// reachability algorithm starting from the members and method-sets of
+// each package. The result may include anonymous functions and
+// synthetic wrappers.
+//
+// Precondition: all packages are built.
+//
+func AllFunctions(prog *ir.Program) map[*ir.Function]bool {
+ visit := visitor{
+ prog: prog,
+ seen: make(map[*ir.Function]bool),
+ }
+ visit.program()
+ return visit.seen
+}
+
+type visitor struct {
+ prog *ir.Program
+ seen map[*ir.Function]bool
+}
+
+func (visit *visitor) program() {
+ for _, pkg := range visit.prog.AllPackages() {
+ for _, mem := range pkg.Members {
+ if fn, ok := mem.(*ir.Function); ok {
+ visit.function(fn)
+ }
+ }
+ }
+ for _, T := range visit.prog.RuntimeTypes() {
+ mset := visit.prog.MethodSets.MethodSet(T)
+ for i, n := 0, mset.Len(); i < n; i++ {
+ visit.function(visit.prog.MethodValue(mset.At(i)))
+ }
+ }
+}
+
+func (visit *visitor) function(fn *ir.Function) {
+ if !visit.seen[fn] {
+ visit.seen[fn] = true
+ var buf [10]*ir.Value // avoid alloc in common case
+ for _, b := range fn.Blocks {
+ for _, instr := range b.Instrs {
+ for _, op := range instr.Operands(buf[:0]) {
+ if fn, ok := (*op).(*ir.Function); ok {
+ visit.function(fn)
+ }
+ }
+ }
+ }
+ }
+}
+
+// MainPackages returns the subset of the specified packages
+// named "main" that define a main function.
+// The result may include synthetic "testmain" packages.
+func MainPackages(pkgs []*ir.Package) []*ir.Package {
+ var mains []*ir.Package
+ for _, pkg := range pkgs {
+ if pkg.Pkg.Name() == "main" && pkg.Func("main") != nil {
+ mains = append(mains, pkg)
+ }
+ }
+ return mains
+}