cmd/compile: thread Curfn through to debuginfo

Updates #15756

Change-Id: I860dd45cae9d851c7844654621bbc99efe7c7f03
Reviewed-on: https://go-review.googlesource.com/38591
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/compile/internal/gc/gsubr.go

@@ -41,11 +41,13 @@ type Progs struct {
 	next  *obj.Prog // next Prog
 	pc    int64     // virtual PC; count of Progs
 	pos   src.XPos  // position to use for new Progs
+	curfn *Node     // fn these Progs are for
 }
 
 // newProgs returns a new Progs for fn.
 func newProgs(fn *Node) *Progs {
 	pp := new(Progs)
+	pp.curfn = fn
 
 	// prime the pump
 	pp.next = Ctxt.NewProg()
@@ -58,7 +60,7 @@ func newProgs(fn *Node) *Progs {
 
 // Flush converts from pp to machine code.
 func (pp *Progs) Flush() {
-	plist := &obj.Plist{Firstpc: pp.Text}
+	plist := &obj.Plist{Firstpc: pp.Text, Curfn: pp.curfn}
 	obj.Flushplist(Ctxt, plist)
 	// Clear pp to enable GC and avoid abuse.
 	*pp = Progs{}

src/cmd/compile/internal/gc/pgen.go

@@ -310,13 +310,14 @@ func compile(fn *Node) {
 	pp.Flush()
 }
 
-func debuginfo(fnsym *obj.LSym) []*dwarf.Var {
-	if expect := Linksym(Curfn.Func.Nname.Sym); fnsym != expect {
+func debuginfo(fnsym *obj.LSym, curfn interface{}) []*dwarf.Var {
+	fn := curfn.(*Node)
+	if expect := Linksym(fn.Func.Nname.Sym); fnsym != expect {
 		Fatalf("unexpected fnsym: %v != %v", fnsym, expect)
 	}
 
 	var vars []*dwarf.Var
-	for _, n := range Curfn.Func.Dcl {
+	for _, n := range fn.Func.Dcl {
 		if n.Op != ONAME { // might be OTYPE or OLITERAL
 			continue
 		}

src/cmd/internal/obj/link.go

@@ -746,7 +746,7 @@ type Link struct {
 	Armsize       int32
 	Pc            int64
 	DiagFunc      func(string, ...interface{})
-	DebugInfo     func(fn *LSym) []*dwarf.Var
+	DebugInfo     func(fn *LSym, curfn interface{}) []*dwarf.Var // if non-nil, curfn is a *gc.Node
 	Cursym        *LSym
 	Version       int
 	Errors        int

src/cmd/internal/obj/objfile.go

@@ -553,7 +553,7 @@ func (c dwCtxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64
 
 // makeFuncDebugEntry makes a DWARF Debugging Information Entry
 // for TEXT symbol s.
-func makeFuncDebugEntry(ctxt *Link, s *LSym) {
+func makeFuncDebugEntry(ctxt *Link, curfn interface{}, s *LSym) {
 	dsym := Linklookup(ctxt, dwarf.InfoPrefix+s.Name, int(s.Version))
 	if dsym.Size != 0 {
 		return
@@ -562,7 +562,7 @@ func makeFuncDebugEntry(ctxt *Link, s *LSym) {
 	dsym.Set(AttrDuplicateOK, s.DuplicateOK())
 	var vars []*dwarf.Var
 	if ctxt.DebugInfo != nil {
-		vars = ctxt.DebugInfo(s)
+		vars = ctxt.DebugInfo(s, curfn)
 	}
 	dwarf.PutFunc(dwCtxt{ctxt}, dsym, s.Name, s.Version == 0, s, s.Size, vars)
 	ctxt.Data = append(ctxt.Data, dsym)

src/cmd/internal/obj/plist.go

@@ -12,6 +12,7 @@ import (
 
 type Plist struct {
 	Firstpc *Prog
+	Curfn   interface{} // holds a *gc.Node, if non-nil
 }
 
 func Flushplist(ctxt *Link, plist *Plist) {
@@ -127,7 +128,7 @@ func flushplist(ctxt *Link, plist *Plist, freeProgs bool) {
 		ctxt.Arch.Preprocess(ctxt, s)
 		ctxt.Arch.Assemble(ctxt, s)
 		linkpcln(ctxt, s)
-		makeFuncDebugEntry(ctxt, s)
+		makeFuncDebugEntry(ctxt, plist.Curfn, s)
 		if freeProgs {
 			s.Text = nil
 		}