[llgo] irgen: introduce ManglePackagePath function

[pcc]

Summary

This is useful for clients that need to use llgo's mangling of the package
path to look up a specific function within a given package.

[axw]

LGTM

irgen/typemap.go

for i := 0; i != r.Len(); i++ {
       ctx.mangleType(r.At(i).Type(), b)
     }
     b.WriteRune('e')
   }
 
   b.WriteRune('e')
 }
 
-func (ctx *manglerContext) manglePackagePath(pkgpath string, b *bytes.Buffer) {
+func ManglePackagePath(pkgpath string) string {
   pkgpath = strings.Replace(pkgpath, "/", "_", -1)
   pkgpath = strings.Replace(pkgpath, ".", "_", -1)
-  b.WriteString(pkgpath)
+  return pkgpath
 }
 
 func (ctx *manglerContext) mangleType(t types.Type, b *bytes.Buffer) {
   switch t := t.(type) {
   case *types.Basic, *types.Named:
     var nb bytes.Buffer
     ti := ctx.getNamedTypeInfo(t)
     if ti.pkgpath != "" {
-      ctx.manglePackagePath(ti.pkgpath, &nb)
+      nb.WriteString(ManglePackagePath(ti.pkgpath))
       nb.WriteRune('.')
     }
     if ti.functionName != "" {
       nb.WriteString(ti.functionName)
       nb.WriteRune('$')
       if ti.scopeNum != 0 {
         nb.WriteString(strconv.Itoa(ti.scopeNum))
         nb.WriteRune('$')

 }
 
 func (ctx *manglerContext) mangleTypeDescriptorName(t types.Type, b *bytes.Buffer) {
   switch t := t.(type) {
   case *types.Basic, *types.Named:
     b.WriteString("__go_tdn_")
     ti := ctx.getNamedTypeInfo(t)
     if ti.pkgpath != "" {
-      ctx.manglePackagePath(ti.pkgpath, b)
+      b.WriteString(ManglePackagePath(ti.pkgpath))
       b.WriteRune('.')
     }
     if ti.functionName != "" {
       b.WriteString(ti.functionName)
       b.WriteRune('.')
       if ti.scopeNum != 0 {
         b.WriteString(strconv.Itoa(ti.scopeNum))
         b.WriteRune('.')
func (ctx *manglerContext) mangleFunctionName(f *ssa.Function) string {
   var pkg *types.Package
   if f.Pkg != nil {
     pkg = f.Pkg.Object
   } else if !f.Object().Exported() {
     pkg = f.Object().Pkg()
   }
 
   if pkg != nil {
-    ctx.manglePackagePath(pkg.Path(), &b)
+    b.WriteString(ManglePackagePath(pkg.Path()))
     b.WriteRune('.')
   }
 
   if f.Signature.Recv() == nil && f.Name() == "init" {
     b.WriteString(".import")
   } else {
     b.WriteString(f.Name())
   }
   if f.Signature.Recv() != nil {
     b.WriteRune('.')
     ctx.mangleType(f.Signature.Recv().Type(), &b)
   }
 
   return b.String()
 }
 
 func (ctx *manglerContext) mangleGlobalName(g *ssa.Global) string {
   var b bytes.Buffer
 
-  ctx.manglePackagePath(g.Pkg.Object.Path(), &b)
+  b.WriteString(ManglePackagePath(g.Pkg.Object.Path()))
   b.WriteRune('.')
   b.WriteString(g.Name())
 
   return b.String()
 }
 
 const (
   // From gofrontend/types.h

 }
 
 func (tm *TypeMap) writeType(typ types.Type, b *bytes.Buffer) {
   switch t := typ.(type) {
   case *types.Basic, *types.Named:
     ti := tm.mc.getNamedTypeInfo(t)
     if ti.pkgpath != "" {
       b.WriteByte('\t')
-      tm.mc.manglePackagePath(ti.pkgpath, b)
+      b.WriteString(ManglePackagePath(ti.pkgpath))
       b.WriteByte('\t')
       b.WriteString(ti.pkgname)
       b.WriteByte('.')
     }
     if ti.functionName != "" {
       b.WriteByte('\t')
       b.WriteString(ti.functionName)
       b.WriteByte('$')