cmd/internal/obj: move STEXT-only LSym fields into new FuncInfo struct

Shrinks LSym somewhat for non-STEXT LSyms, which are much more common.

While here, switch to tracking Automs in a slice instead of a linked
list. (Previously, this would have made LSyms larger.)

Passes toolstash-check.

Change-Id: I082e50e1d1f1b544c9e06b6e412a186be6a4a2b5
Reviewed-on: https://go-review.googlesource.com/37872Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -436,6 +436,10 @@ func gendebug(fnsym *obj.LSym, decls []*Node) {
 		return
 	}
 
+	if fnsym.FuncInfo == nil {
+		fnsym.FuncInfo = new(obj.FuncInfo)
+	}
+
 	for _, n := range decls {
 		if n.Op != ONAME { // might be OTYPE or OLITERAL
 			continue
@@ -461,8 +465,13 @@ func gendebug(fnsym *obj.LSym, decls []*Node) {
 			Gotype:  Linksym(ngotype(n)),
 		}
 
-		a.Link = fnsym.Autom
-		fnsym.Autom = a
+		fnsym.Autom = append(fnsym.Autom, a)
+	}
+
+	// Reverse to make toolstash happy.
+	// TODO(mdempsky): Remove.
+	for i, j := 0, len(fnsym.Autom)-1; i < j; i, j = i+1, j-1 {
+		fnsym.Autom[i], fnsym.Autom[j] = fnsym.Autom[j], fnsym.Autom[i]
 	}
 }
 

src/cmd/internal/obj/link.go

@@ -326,15 +326,22 @@ type LSym struct {
 	Attribute
 
 	RefIdx int // Index of this symbol in the symbol reference list.
-	Args   int32
-	Locals int32
 	Size   int64
 	Gotype *LSym
-	Autom  *Auto
-	Text   *Prog
-	Pcln   *Pcln
 	P      []byte
 	R      []Reloc
+
+	// TODO(mdempsky): De-anonymize field.
+	*FuncInfo
+}
+
+// A FuncInfo contains extra fields for STEXT symbols.
+type FuncInfo struct {
+	Args   int32
+	Locals int32
+	Text   *Prog
+	Autom  []*Auto
+	Pcln   Pcln
 }
 
 // Attribute is a set of symbol attributes.
@@ -691,7 +698,6 @@ func (r RelocType) IsDirectJump() bool {
 
 type Auto struct {
 	Asym    *LSym
-	Link    *Auto
 	Aoffset int32
 	Name    AddrName
 	Gotype  *LSym

src/cmd/internal/obj/objfile.go

@@ -153,7 +153,7 @@ func (w *objWriter) addLengths(s *LSym) {
 		return
 	}
 
-	pc := s.Pcln
+	pc := &s.Pcln
 
 	data := 0
 	data += len(pc.Pcsp.P)
@@ -167,11 +167,7 @@ func (w *objWriter) addLengths(s *LSym) {
 	w.nData += data
 	w.nPcdata += len(pc.Pcdata)
 
-	autom := 0
-	for a := s.Autom; a != nil; a = a.Link {
-		autom++
-	}
-	w.nAutom += autom
+	w.nAutom += len(s.Autom)
 	w.nFuncdata += len(pc.Funcdataoff)
 	w.nFile += len(pc.File)
 }
@@ -227,7 +223,7 @@ func WriteObjFile(ctxt *Link, b *bufio.Writer) {
 	// Data block
 	for _, s := range ctxt.Text {
 		w.wr.Write(s.P)
-		pc := s.Pcln
+		pc := &s.Pcln
 		w.wr.Write(pc.Pcsp.P)
 		w.wr.Write(pc.Pcfile.P)
 		w.wr.Write(pc.Pcline.P)
@@ -294,11 +290,11 @@ func (w *objWriter) writeRefs(s *LSym) {
 	}
 
 	if s.Type == STEXT {
-		for a := s.Autom; a != nil; a = a.Link {
+		for _, a := range s.Autom {
 			w.writeRef(a.Asym, false)
 			w.writeRef(a.Gotype, false)
 		}
-		pc := s.Pcln
+		pc := &s.Pcln
 		for _, d := range pc.Funcdata {
 			w.writeRef(d, false)
 		}
@@ -338,15 +334,15 @@ func (w *objWriter) writeSymDebug(s *LSym) {
 			fmt.Fprintf(ctxt.Bso, " leaf")
 		}
 	}
-
 	fmt.Fprintf(ctxt.Bso, "\n")
+	if s.Type == STEXT {
 		for p := s.Text; p != nil; p = p.Link {
 			fmt.Fprintf(ctxt.Bso, "\t%#04x %v\n", uint(int(p.Pc)), p)
 		}
-	var c int
-	var j int
-	for i := 0; i < len(s.P); {
+	}
+	for i := 0; i < len(s.P); i += 16 {
 		fmt.Fprintf(ctxt.Bso, "\t%#04x", uint(i))
+		j := i
 		for j = i; j < i+16 && j < len(s.P); j++ {
 			fmt.Fprintf(ctxt.Bso, " %02x", s.P[j])
 		}
@@ -355,7 +351,7 @@ func (w *objWriter) writeSymDebug(s *LSym) {
 		}
 		fmt.Fprintf(ctxt.Bso, "  ")
 		for j = i; j < i+16 && j < len(s.P); j++ {
-			c = int(s.P[j])
+			c := int(s.P[j])
 			if ' ' <= c && c <= 0x7e {
 				fmt.Fprintf(ctxt.Bso, "%c", c)
 			} else {
@@ -364,7 +360,6 @@ func (w *objWriter) writeSymDebug(s *LSym) {
 		}
 
 		fmt.Fprintf(ctxt.Bso, "\n")
-		i += 16
 	}
 
 	sort.Sort(relocByOff(s.R)) // generate stable output
@@ -440,12 +435,8 @@ func (w *objWriter) writeSym(s *LSym) {
 		flags |= 1 << 2
 	}
 	w.writeInt(flags)
-	n := 0
-	for a := s.Autom; a != nil; a = a.Link {
-		n++
-	}
-	w.writeInt(int64(n))
-	for a := s.Autom; a != nil; a = a.Link {
+	w.writeInt(int64(len(s.Autom)))
+	for _, a := range s.Autom {
 		w.writeRefIndex(a.Asym)
 		w.writeInt(int64(a.Aoffset))
 		if a.Name == NAME_AUTO {
@@ -458,7 +449,7 @@ func (w *objWriter) writeSym(s *LSym) {
 		w.writeRefIndex(a.Gotype)
 	}
 
-	pc := s.Pcln
+	pc := &s.Pcln
 	w.writeInt(int64(len(pc.Pcsp.P)))
 	w.writeInt(int64(len(pc.Pcfile.P)))
 	w.writeInt(int64(len(pc.Pcline.P)))
@@ -575,7 +566,7 @@ func gendwarf(ctxt *Link, text []*LSym) []*LSym {
 		var vars []*dwarf.Var
 		var abbrev int
 		var offs int32
-		for a := s.Autom; a != nil; a = a.Link {
+		for _, a := range s.Autom {
 			switch a.Name {
 			case NAME_AUTO:
 				abbrev = dwarf.DW_ABRV_AUTO

src/cmd/internal/obj/pcln.go

@@ -254,8 +254,7 @@ func pctopcdata(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg i
 func linkpcln(ctxt *Link, cursym *LSym) {
 	ctxt.Cursym = cursym
 
-	pcln := new(Pcln)
-	cursym.Pcln = pcln
+	pcln := &cursym.Pcln
 
 	npcdata := 0
 	nfuncdata := 0

src/cmd/internal/obj/plist.go

@@ -46,6 +46,9 @@ func flushplist(ctxt *Link, plist *Plist, freeProgs bool) {
 
 				continue
 			}
+			if s.FuncInfo == nil {
+				s.FuncInfo = new(FuncInfo)
+			}
 
 			if s.Text != nil {
 				log.Fatalf("duplicate TEXT for %s", s.Name)

src/cmd/internal/obj/sizeof_test.go

@@ -23,7 +23,7 @@ func TestSizeof(t *testing.T) {
 		_64bit uintptr     // size on 64bit platforms
 	}{
 		{Addr{}, 40, 64},
-		{LSym{}, 76, 128},
+		{LSym{}, 60, 104},
 		{Prog{}, 148, 232},
 	}