cmd/link: pack LSym boolean attributes

No performance improvement, but possibly more readable.

Linking juju:
	tip:  real 0m5.470s user 0m6.131s
	this: real 0m5.392s user 0m6.087s

Change-Id: I578e94fbe6c11b19d79034c33b3db31d9689d439
Reviewed-on: https://go-review.googlesource.com/20108Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

src/cmd/link/internal/amd64/asm.go

@@ -43,7 +43,7 @@ func PADDR(x uint32) uint32 {
 }
 
 func Addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) int64 {
-	s.Reachable = true
+	s.Attr |= ld.AttrReachable
 	i := s.Size
 	s.Size += 4
 	ld.Symgrow(ctxt, s, s.Size)
@@ -65,11 +65,11 @@ func gentext() {
 		// an init function
 		return
 	}
-	addmoduledata.Reachable = true
+	addmoduledata.Attr |= ld.AttrReachable
 	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
 	initfunc.Type = obj.STEXT
-	initfunc.Local = true
-	initfunc.Reachable = true
+	initfunc.Attr |= ld.AttrLocal
+	initfunc.Attr |= ld.AttrReachable
 	o := func(op ...uint8) {
 		for _, op1 := range op {
 			ld.Adduint8(ld.Ctxt, initfunc, op1)
@@ -93,8 +93,8 @@ func gentext() {
 	}
 	ld.Ctxt.Etextp = initfunc
 	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
-	initarray_entry.Reachable = true
-	initarray_entry.Local = true
+	initarray_entry.Attr |= ld.AttrReachable
+	initarray_entry.Attr |= ld.AttrLocal
 	initarray_entry.Type = obj.SINITARR
 	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }

src/cmd/link/internal/arm/asm.go

@@ -68,11 +68,11 @@ func gentext() {
 		// an init function
 		return
 	}
-	addmoduledata.Reachable = true
+	addmoduledata.Attr |= ld.AttrReachable
 	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
 	initfunc.Type = obj.STEXT
-	initfunc.Local = true
-	initfunc.Reachable = true
+	initfunc.Attr |= ld.AttrLocal
+	initfunc.Attr |= ld.AttrReachable
 	o := func(op uint32) {
 		ld.Adduint32(ld.Ctxt, initfunc, op)
 	}
@@ -102,8 +102,8 @@ func gentext() {
 	}
 	ld.Ctxt.Etextp = initfunc
 	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
-	initarray_entry.Reachable = true
-	initarray_entry.Local = true
+	initarray_entry.Attr |= ld.AttrReachable
+	initarray_entry.Attr |= ld.AttrLocal
 	initarray_entry.Type = obj.SINITARR
 	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }
@@ -480,7 +480,7 @@ func addpltreloc(ctxt *ld.Link, plt *ld.LSym, got *ld.LSym, sym *ld.LSym, typ in
 	r.Type = int32(typ)
 	r.Add = int64(sym.Got) - 8
 
-	plt.Reachable = true
+	plt.Attr |= ld.AttrReachable
 	plt.Size += 4
 	ld.Symgrow(ctxt, plt, plt.Size)
 

src/cmd/link/internal/arm64/asm.go

@@ -48,11 +48,11 @@ func gentext() {
 		// an init function
 		return
 	}
-	addmoduledata.Reachable = true
+	addmoduledata.Attr |= ld.AttrReachable
 	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
 	initfunc.Type = obj.STEXT
-	initfunc.Local = true
-	initfunc.Reachable = true
+	initfunc.Attr |= ld.AttrLocal
+	initfunc.Attr |= ld.AttrReachable
 	o := func(op uint32) {
 		ld.Adduint32(ld.Ctxt, initfunc, op)
 	}
@@ -85,8 +85,8 @@ func gentext() {
 	}
 	ld.Ctxt.Etextp = initfunc
 	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
-	initarray_entry.Reachable = true
-	initarray_entry.Local = true
+	initarray_entry.Attr |= ld.AttrReachable
+	initarray_entry.Attr |= ld.AttrLocal
 	initarray_entry.Type = obj.SINITARR
 	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }
@@ -258,7 +258,7 @@ func archreloc(r *ld.Reloc, s *ld.LSym, val *int64) int {
 			// (https://sourceware.org/bugzilla/show_bug.cgi?id=18270). So
 			// we convert the adrp; ld64 + R_ARM64_GOTPCREL into adrp;
 			// add + R_ADDRARM64.
-			if !(r.Sym.Version != 0 || (r.Sym.Type&obj.SHIDDEN != 0) || r.Sym.Local) && r.Sym.Type == obj.STEXT && ld.DynlinkingGo() {
+			if !(r.Sym.Version != 0 || (r.Sym.Type&obj.SHIDDEN != 0) || r.Sym.Attr.Local()) && r.Sym.Type == obj.STEXT && ld.DynlinkingGo() {
 				if o2&0xffc00000 != 0xf9400000 {
 					ld.Ctxt.Diag("R_ARM64_GOTPCREL against unexpected instruction %x", o2)
 				}

src/cmd/link/internal/ld/data.go

@@ -63,7 +63,7 @@ func setuintxx(ctxt *Link, s *LSym, off int64, v uint64, wid int64) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	if s.Size < off+wid {
 		s.Size = off + wid
 		Symgrow(ctxt, s, s.Size)
@@ -121,7 +121,7 @@ func Addaddrplus(ctxt *Link, s *LSym, t *LSym, add int64) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	i := s.Size
 	s.Size += int64(ctxt.Arch.Ptrsize)
 	Symgrow(ctxt, s, s.Size)
@@ -138,7 +138,7 @@ func Addpcrelplus(ctxt *Link, s *LSym, t *LSym, add int64) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	i := s.Size
 	s.Size += 4
 	Symgrow(ctxt, s, s.Size)
@@ -159,7 +159,7 @@ func setaddrplus(ctxt *Link, s *LSym, off int64, t *LSym, add int64) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	if off+int64(ctxt.Arch.Ptrsize) > s.Size {
 		s.Size = off + int64(ctxt.Arch.Ptrsize)
 		Symgrow(ctxt, s, s.Size)
@@ -182,7 +182,7 @@ func addsize(ctxt *Link, s *LSym, t *LSym) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	i := s.Size
 	s.Size += int64(ctxt.Arch.Ptrsize)
 	Symgrow(ctxt, s, s.Size)
@@ -198,7 +198,7 @@ func addaddrplus4(ctxt *Link, s *LSym, t *LSym, add int64) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	i := s.Size
 	s.Size += 4
 	Symgrow(ctxt, s, s.Size)
@@ -360,7 +360,7 @@ func relocsym(s *LSym) {
 				Diag("unhandled relocation for %s (type %d rtype %d)", r.Sym.Name, r.Sym.Type, r.Type)
 			}
 		}
-		if r.Sym != nil && r.Sym.Type != obj.STLSBSS && !r.Sym.Reachable {
+		if r.Sym != nil && r.Sym.Type != obj.STLSBSS && !r.Sym.Attr.Reachable() {
 			Diag("unreachable sym in relocation: %s %s", s.Name, r.Sym.Name)
 		}
 
@@ -633,7 +633,7 @@ func dynrelocsym(s *LSym) {
 			if targ == nil {
 				continue
 			}
-			if !targ.Reachable {
+			if !targ.Attr.Reachable() {
 				Diag("internal inconsistency: dynamic symbol %s is not reachable.", targ.Name)
 			}
 			if r.Sym.Plt == -2 && r.Sym.Got != -2 { // make dynimport JMP table for PE object files.
@@ -668,7 +668,7 @@ func dynrelocsym(s *LSym) {
 	for ri := 0; ri < len(s.R); ri++ {
 		r = &s.R[ri]
 		if r.Sym != nil && r.Sym.Type == obj.SDYNIMPORT || r.Type >= 256 {
-			if r.Sym != nil && !r.Sym.Reachable {
+			if r.Sym != nil && !r.Sym.Attr.Reachable() {
 				Diag("internal inconsistency: dynamic symbol %s is not reachable.", r.Sym.Name)
 			}
 			Thearch.Adddynrel(s, r)
@@ -763,7 +763,7 @@ func Codeblk(addr int64, size int64) {
 
 	var sym *LSym
 	for sym = Ctxt.Textp; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if sym.Value >= addr {
@@ -774,7 +774,7 @@ func Codeblk(addr int64, size int64) {
 	eaddr := addr + size
 	var q []byte
 	for ; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if sym.Value >= eaddr {
@@ -938,19 +938,19 @@ func addstrdata(name string, value string) {
 
 	s := Linklookup(Ctxt, name, 0)
 	s.Size = 0
-	s.Dupok = 1
-	reachable := s.Reachable
+	s.Attr |= AttrDuplicateOK
+	reachable := s.Attr.Reachable()
 	Addaddr(Ctxt, s, sp)
 	adduintxx(Ctxt, s, uint64(len(value)), Thearch.Ptrsize)
 
 	// addstring, addaddr, etc., mark the symbols as reachable.
 	// In this case that is not necessarily true, so stick to what
 	// we know before entering this function.
-	s.Reachable = reachable
+	s.Attr.Set(AttrReachable, reachable)
 
 	strdata = append(strdata, s)
 
-	sp.Reachable = reachable
+	sp.Attr.Set(AttrReachable, reachable)
 }
 
 func checkstrdata() {
@@ -967,7 +967,7 @@ func Addstring(s *LSym, str string) int64 {
 	if s.Type == 0 {
 		s.Type = obj.SNOPTRDATA
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	r := int32(s.Size)
 	n := len(str) + 1
 	if s.Name == ".shstrtab" {
@@ -987,8 +987,8 @@ func addgostring(s *LSym, symname, str string) {
 	if sym.Type != obj.Sxxx {
 		Diag("duplicate symname in addgostring: %s", symname)
 	}
-	sym.Reachable = true
-	sym.Local = true
+	sym.Attr |= AttrReachable
+	sym.Attr |= AttrLocal
 	sym.Type = obj.SRODATA
 	sym.Size = int64(len(str))
 	sym.P = []byte(str)
@@ -1001,7 +1001,7 @@ func addinitarrdata(s *LSym) {
 	sp := Linklookup(Ctxt, p, 0)
 	sp.Type = obj.SINITARR
 	sp.Size = 0
-	sp.Dupok = 1
+	sp.Attr |= AttrDuplicateOK
 	Addaddr(Ctxt, sp, s)
 }
 
@@ -1146,14 +1146,14 @@ func dodata() {
 	datap = nil
 
 	for _, s := range Ctxt.Allsym {
-		if !s.Reachable || s.Special != 0 {
+		if !s.Attr.Reachable() || s.Attr.Special() {
 			continue
 		}
 		if obj.STEXT < s.Type && s.Type < obj.SXREF {
-			if s.Onlist != 0 {
+			if s.Attr.OnList() {
 				log.Fatalf("symbol %s listed multiple times", s.Name)
 			}
-			s.Onlist = 1
+			s.Attr |= AttrOnList
 			if last == nil {
 				datap = s
 			} else {
@@ -1636,7 +1636,7 @@ func textbuildid() {
 	}
 
 	sym := Linklookup(Ctxt, "go.buildid", 0)
-	sym.Reachable = true
+	sym.Attr |= AttrReachable
 	// The \xff is invalid UTF-8, meant to make it less likely
 	// to find one of these accidentally.
 	data := "\xff Go build ID: " + strconv.Quote(buildid) + "\n \xff"
@@ -1813,12 +1813,12 @@ func address() {
 	xdefine("runtime.etypelink", obj.SRODATA, int64(typelink.Vaddr+typelink.Length))
 
 	sym := Linklookup(Ctxt, "runtime.gcdata", 0)
-	sym.Local = true
+	sym.Attr |= AttrLocal
 	xdefine("runtime.egcdata", obj.SRODATA, Symaddr(sym)+sym.Size)
 	Linklookup(Ctxt, "runtime.egcdata", 0).Sect = sym.Sect
 
 	sym = Linklookup(Ctxt, "runtime.gcbss", 0)
-	sym.Local = true
+	sym.Attr |= AttrLocal
 	xdefine("runtime.egcbss", obj.SRODATA, Symaddr(sym)+sym.Size)
 	Linklookup(Ctxt, "runtime.egcbss", 0).Sect = sym.Sect
 

src/cmd/link/internal/ld/dwarf.go

@@ -1997,16 +1997,16 @@ func Dwarfemitdebugsections() {
 			sect = addmachodwarfsect(sect, ".debug_info")
 
 			infosym = Linklookup(Ctxt, ".debug_info", 0)
-			infosym.Hidden = true
+			infosym.Attr |= AttrHidden
 
 			abbrevsym = Linklookup(Ctxt, ".debug_abbrev", 0)
-			abbrevsym.Hidden = true
+			abbrevsym.Attr |= AttrHidden
 
 			linesym = Linklookup(Ctxt, ".debug_line", 0)
-			linesym.Hidden = true
+			linesym.Attr |= AttrHidden
 
 			framesym = Linklookup(Ctxt, ".debug_frame", 0)
-			framesym.Hidden = true
+			framesym.Attr |= AttrHidden
 		}
 	}
 
@@ -2183,16 +2183,16 @@ func dwarfaddshstrings(shstrtab *LSym) {
 		}
 
 		infosym = Linklookup(Ctxt, ".debug_info", 0)
-		infosym.Hidden = true
+		infosym.Attr |= AttrHidden
 
 		abbrevsym = Linklookup(Ctxt, ".debug_abbrev", 0)
-		abbrevsym.Hidden = true
+		abbrevsym.Attr |= AttrHidden
 
 		linesym = Linklookup(Ctxt, ".debug_line", 0)
-		linesym.Hidden = true
+		linesym.Attr |= AttrHidden
 
 		framesym = Linklookup(Ctxt, ".debug_frame", 0)
-		framesym.Hidden = true
+		framesym.Attr |= AttrHidden
 	}
 }
 

src/cmd/link/internal/ld/elf.go

@@ -1342,7 +1342,7 @@ func elfdynhash() {
 	nsym := Nelfsym
 	s := Linklookup(Ctxt, ".hash", 0)
 	s.Type = obj.SELFROSECT
-	s.Reachable = true
+	s.Attr |= AttrReachable
 
 	i := nsym
 	nbucket := 1
@@ -1624,7 +1624,7 @@ func elfrelocsect(sect *Section, first *LSym) {
 	sect.Reloff = uint64(Cpos())
 	var sym *LSym
 	for sym = first; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if uint64(sym.Value) >= sect.Vaddr {
@@ -1636,7 +1636,7 @@ func elfrelocsect(sect *Section, first *LSym) {
 	var r *Reloc
 	var ri int
 	for ; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if sym.Value >= int64(eaddr) {
@@ -1685,7 +1685,7 @@ func Elfemitreloc() {
 
 func addgonote(sectionName string, tag uint32, desc []byte) {
 	s := Linklookup(Ctxt, sectionName, 0)
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	s.Type = obj.SELFROSECT
 	// namesz
 	Adduint32(Ctxt, s, uint32(len(ELF_NOTE_GO_NAME)))
@@ -1715,7 +1715,7 @@ func doelf() {
 	shstrtab := Linklookup(Ctxt, ".shstrtab", 0)
 
 	shstrtab.Type = obj.SELFROSECT
-	shstrtab.Reachable = true
+	shstrtab.Attr |= AttrReachable
 
 	Addstring(shstrtab, "")
 	Addstring(shstrtab, ".text")
@@ -1850,7 +1850,7 @@ func doelf() {
 		s := Linklookup(Ctxt, ".dynsym", 0)
 
 		s.Type = obj.SELFROSECT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		switch Thearch.Thechar {
 		case '0', '6', '7', '9':
 			s.Size += ELF64SYMSIZE
@@ -1862,7 +1862,7 @@ func doelf() {
 		s = Linklookup(Ctxt, ".dynstr", 0)
 
 		s.Type = obj.SELFROSECT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		if s.Size == 0 {
 			Addstring(s, "")
 		}
@@ -1875,35 +1875,35 @@ func doelf() {
 		default:
 			s = Linklookup(Ctxt, ".rel", 0)
 		}
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFROSECT
 
 		/* global offset table */
 		s = Linklookup(Ctxt, ".got", 0)
 
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFGOT // writable
 
 		/* ppc64 glink resolver */
 		if Thearch.Thechar == '9' {
 			s := Linklookup(Ctxt, ".glink", 0)
-			s.Reachable = true
+			s.Attr |= AttrReachable
 			s.Type = obj.SELFRXSECT
 		}
 
 		/* hash */
 		s = Linklookup(Ctxt, ".hash", 0)
 
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFROSECT
 
 		s = Linklookup(Ctxt, ".got.plt", 0)
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFSECT // writable
 
 		s = Linklookup(Ctxt, ".plt", 0)
 
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		if Thearch.Thechar == '9' {
 			// In the ppc64 ABI, .plt is a data section
 			// written by the dynamic linker.
@@ -1920,21 +1920,21 @@ func doelf() {
 		default:
 			s = Linklookup(Ctxt, ".rel.plt", 0)
 		}
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFROSECT
 
 		s = Linklookup(Ctxt, ".gnu.version", 0)
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFROSECT
 
 		s = Linklookup(Ctxt, ".gnu.version_r", 0)
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFROSECT
 
 		/* define dynamic elf table */
 		s = Linklookup(Ctxt, ".dynamic", 0)
 
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Type = obj.SELFSECT // writable
 
 		/*
@@ -1987,10 +1987,10 @@ func doelf() {
 		// The go.link.abihashbytes symbol will be pointed at the appropriate
 		// part of the .note.go.abihash section in data.go:func address().
 		s := Linklookup(Ctxt, "go.link.abihashbytes", 0)
-		s.Local = true
+		s.Attr |= AttrLocal
 		s.Type = obj.SRODATA
-		s.Special = 1
-		s.Reachable = true
+		s.Attr |= AttrSpecial
+		s.Attr |= AttrReachable
 		s.Size = int64(sha1.Size)
 
 		sort.Sort(byPkg(Ctxt.Library))
@@ -2531,7 +2531,7 @@ func Elfadddynsym(ctxt *Link, s *LSym) {
 		/* type */
 		t := STB_GLOBAL << 4
 
-		if s.Cgoexport != 0 && s.Type&obj.SMASK == obj.STEXT {
+		if s.Attr.CgoExport() && s.Type&obj.SMASK == obj.STEXT {
 			t |= STT_FUNC
 		} else {
 			t |= STT_OBJECT
@@ -2558,7 +2558,7 @@ func Elfadddynsym(ctxt *Link, s *LSym) {
 		/* size of object */
 		Adduint64(ctxt, d, uint64(s.Size))
 
-		if Thearch.Thechar == '6' && s.Cgoexport&CgoExportDynamic == 0 && s.Dynimplib != "" && !seenlib[s.Dynimplib] {
+		if Thearch.Thechar == '6' && !s.Attr.CgoExportDynamic() && s.Dynimplib != "" && !seenlib[s.Dynimplib] {
 			Elfwritedynent(Linklookup(ctxt, ".dynamic", 0), DT_NEEDED, uint64(Addstring(Linklookup(ctxt, ".dynstr", 0), s.Dynimplib)))
 		}
 	} else {
@@ -2586,9 +2586,9 @@ func Elfadddynsym(ctxt *Link, s *LSym) {
 		t := STB_GLOBAL << 4
 
 		// TODO(mwhudson): presumably the behaviour should actually be the same on both arm and 386.
-		if Thearch.Thechar == '8' && s.Cgoexport != 0 && s.Type&obj.SMASK == obj.STEXT {
+		if Thearch.Thechar == '8' && s.Attr.CgoExport() && s.Type&obj.SMASK == obj.STEXT {
 			t |= STT_FUNC
-		} else if Thearch.Thechar == '5' && s.Cgoexport&CgoExportDynamic != 0 && s.Type&obj.SMASK == obj.STEXT {
+		} else if Thearch.Thechar == '5' && s.Attr.CgoExportDynamic() && s.Type&obj.SMASK == obj.STEXT {
 			t |= STT_FUNC
 		} else {
 			t |= STT_OBJECT

src/cmd/link/internal/ld/go.go

@@ -279,7 +279,7 @@ func loadcgo(file string, pkg string, p string) {
 				s.Type = 0
 			}
 
-			if s.Cgoexport == 0 {
+			if !s.Attr.CgoExport() {
 				s.Extname = remote
 				dynexp = append(dynexp, s)
 			} else if s.Extname != remote {
@@ -289,9 +289,9 @@ func loadcgo(file string, pkg string, p string) {
 			}
 
 			if f[0] == "cgo_export_static" {
-				s.Cgoexport |= CgoExportStatic
+				s.Attr |= AttrCgoExportStatic
 			} else {
-				s.Cgoexport |= CgoExportDynamic
+				s.Attr |= AttrCgoExportDynamic
 			}
 			if local != f[1] {
 			}
@@ -372,13 +372,13 @@ var markq *LSym
 var emarkq *LSym
 
 func mark1(s *LSym, parent *LSym) {
-	if s == nil || s.Reachable {
+	if s == nil || s.Attr.Reachable() {
 		return
 	}
 	if strings.HasPrefix(s.Name, "go.weak.") {
 		return
 	}
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	s.Reachparent = parent
 	if markq == nil {
 		markq = s
@@ -473,7 +473,7 @@ func deadcode() {
 		// keep each beginning with 'typelink.' if the symbol it points at is being kept.
 		for _, s := range Ctxt.Allsym {
 			if strings.HasPrefix(s.Name, "go.typelink.") {
-				s.Reachable = len(s.R) == 1 && s.R[0].Sym.Reachable
+				s.Attr.Set(AttrReachable, len(s.R) == 1 && s.R[0].Sym.Attr.Reachable())
 			}
 		}
 
@@ -481,7 +481,7 @@ func deadcode() {
 		var last *LSym
 
 		for s := Ctxt.Textp; s != nil; s = s.Next {
-			if !s.Reachable {
+			if !s.Attr.Reachable() {
 				continue
 			}
 
@@ -505,9 +505,9 @@ func deadcode() {
 
 	for _, s := range Ctxt.Allsym {
 		if strings.HasPrefix(s.Name, "go.weak.") {
-			s.Special = 1 // do not lay out in data segment
-			s.Reachable = true
-			s.Hidden = true
+			s.Attr |= AttrSpecial // do not lay out in data segment
+			s.Attr |= AttrReachable
+			s.Attr |= AttrHidden
 		}
 	}
 
@@ -515,9 +515,9 @@ func deadcode() {
 	var buf bytes.Buffer
 	for _, s := range Ctxt.Allsym {
 		if strings.HasPrefix(s.Name, "go.track.") {
-			s.Special = 1 // do not lay out in data segment
-			s.Hidden = true
-			if s.Reachable {
+			s.Attr |= AttrSpecial // do not lay out in data segment
+			s.Attr |= AttrHidden
+			if s.Attr.Reachable() {
 				buf.WriteString(s.Name[9:])
 				for p := s.Reachparent; p != nil; p = p.Reachparent {
 					buf.WriteString("\t")
@@ -535,7 +535,7 @@ func deadcode() {
 		return
 	}
 	s := Linklookup(Ctxt, tracksym, 0)
-	if !s.Reachable {
+	if !s.Attr.Reachable() {
 		return
 	}
 	addstrdata(tracksym, buf.String())
@@ -547,7 +547,7 @@ func doweak() {
 	for _, s := range Ctxt.Allsym {
 		if strings.HasPrefix(s.Name, "go.weak.") {
 			t := Linkrlookup(Ctxt, s.Name[8:], int(s.Version))
-			if t != nil && t.Type != 0 && t.Reachable {
+			if t != nil && t.Type != 0 && t.Attr.Reachable() {
 				s.Value = t.Value
 				s.Type = t.Type
 				s.Outer = t

src/cmd/link/internal/ld/ldelf.go

@@ -784,7 +784,7 @@ func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
 
 		s = sym.sym
 		if s.Outer != nil {
-			if s.Dupok != 0 {
+			if s.Attr.DuplicateOK() {
 				continue
 			}
 			Exitf("%s: duplicate symbol reference: %s in both %s and %s", pn, s.Name, s.Outer.Name, sect.sym.Name)
@@ -793,17 +793,17 @@ func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
 		s.Sub = sect.sym.Sub
 		sect.sym.Sub = s
 		s.Type = sect.sym.Type | s.Type&^obj.SMASK | obj.SSUB
-		if s.Cgoexport&CgoExportDynamic == 0 {
+		if !s.Attr.CgoExportDynamic() {
 			s.Dynimplib = "" // satisfy dynimport
 		}
 		s.Value = int64(sym.value)
 		s.Size = int64(sym.size)
 		s.Outer = sect.sym
 		if sect.sym.Type == obj.STEXT {
-			if s.External != 0 && s.Dupok == 0 {
+			if s.Attr.External() && !s.Attr.DuplicateOK() {
 				Diag("%s: duplicate definition of %s", pn, s.Name)
 			}
-			s.External = 1
+			s.Attr |= AttrExternal
 		}
 
 		if elfobj.machine == ElfMachPower64 {
@@ -827,10 +827,10 @@ func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
 			s.Sub = listsort(s.Sub, valuecmp, listsubp)
 		}
 		if s.Type == obj.STEXT {
-			if s.Onlist != 0 {
+			if s.Attr.OnList() {
 				log.Fatalf("symbol %s listed multiple times", s.Name)
 			}
-			s.Onlist = 1
+			s.Attr |= AttrOnList
 			if Ctxt.Etextp != nil {
 				Ctxt.Etextp.Next = s
 			} else {
@@ -838,10 +838,10 @@ func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
 			}
 			Ctxt.Etextp = s
 			for s = s.Sub; s != nil; s = s.Sub {
-				if s.Onlist != 0 {
+				if s.Attr.OnList() {
 					log.Fatalf("symbol %s listed multiple times", s.Name)
 				}
-				s.Onlist = 1
+				s.Attr |= AttrOnList
 				Ctxt.Etextp.Next = s
 				Ctxt.Etextp = s
 			}
@@ -1043,7 +1043,7 @@ func readelfsym(elfobj *ElfObj, i int, sym *ElfSym, needSym int) (err error) {
 				// comment #5 for details.
 				if s != nil && sym.other == 2 {
 					s.Type |= obj.SHIDDEN
-					s.Dupok = 1
+					s.Attr |= AttrDuplicateOK
 				}
 			}
 

src/cmd/link/internal/ld/ldmacho.go

@@ -620,7 +620,7 @@ func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
 		}
 		s = Linklookup(Ctxt, name, v)
 		if sym.type_&N_EXT == 0 {
-			s.Dupok = 1
+			s.Attr |= AttrDuplicateOK
 		}
 		sym.sym = s
 		if sym.sectnum == 0 { // undefined
@@ -639,7 +639,7 @@ func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
 		}
 
 		if s.Outer != nil {
-			if s.Dupok != 0 {
+			if s.Attr.DuplicateOK() {
 				continue
 			}
 			Exitf("%s: duplicate symbol reference: %s in both %s and %s", pn, s.Name, s.Outer.Name, sect.sym.Name)
@@ -650,14 +650,14 @@ func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
 		outer.Sub = s
 		s.Outer = outer
 		s.Value = int64(sym.value - sect.addr)
-		if s.Cgoexport&CgoExportDynamic == 0 {
+		if !s.Attr.CgoExportDynamic() {
 			s.Dynimplib = "" // satisfy dynimport
 		}
 		if outer.Type == obj.STEXT {
-			if s.External != 0 && s.Dupok == 0 {
+			if s.Attr.External() && !s.Attr.DuplicateOK() {
 				Diag("%s: duplicate definition of %s", pn, s.Name)
 			}
-			s.External = 1
+			s.Attr |= AttrExternal
 		}
 
 		sym.sym = s
@@ -685,10 +685,10 @@ func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
 		}
 
 		if s.Type == obj.STEXT {
-			if s.Onlist != 0 {
+			if s.Attr.OnList() {
 				log.Fatalf("symbol %s listed multiple times", s.Name)
 			}
-			s.Onlist = 1
+			s.Attr |= AttrOnList
 			if Ctxt.Etextp != nil {
 				Ctxt.Etextp.Next = s
 			} else {
@@ -696,10 +696,10 @@ func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
 			}
 			Ctxt.Etextp = s
 			for s1 = s.Sub; s1 != nil; s1 = s1.Sub {
-				if s1.Onlist != 0 {
+				if s1.Attr.OnList() {
 					log.Fatalf("symbol %s listed multiple times", s1.Name)
 				}
-				s1.Onlist = 1
+				s1.Attr |= AttrOnList
 				Ctxt.Etextp.Next = s1
 				Ctxt.Etextp = s1
 			}

src/cmd/link/internal/ld/ldpe.go

@@ -397,7 +397,7 @@ func ldpe(f *obj.Biobuf, pkg string, length int64, pn string) {
 		}
 
 		if s.Outer != nil {
-			if s.Dupok != 0 {
+			if s.Attr.DuplicateOK() {
 				continue
 			}
 			Exitf("%s: duplicate symbol reference: %s in both %s and %s", pn, s.Name, s.Outer.Name, sect.sym.Name)
@@ -410,10 +410,10 @@ func ldpe(f *obj.Biobuf, pkg string, length int64, pn string) {
 		s.Size = 4
 		s.Outer = sect.sym
 		if sect.sym.Type == obj.STEXT {
-			if s.External != 0 && s.Dupok == 0 {
+			if s.Attr.External() && !s.Attr.DuplicateOK() {
 				Diag("%s: duplicate definition of %s", pn, s.Name)
 			}
-			s.External = 1
+			s.Attr |= AttrExternal
 		}
 	}
 
@@ -428,10 +428,10 @@ func ldpe(f *obj.Biobuf, pkg string, length int64, pn string) {
 			s.Sub = listsort(s.Sub, valuecmp, listsubp)
 		}
 		if s.Type == obj.STEXT {
-			if s.Onlist != 0 {
+			if s.Attr.OnList() {
 				log.Fatalf("symbol %s listed multiple times", s.Name)
 			}
-			s.Onlist = 1
+			s.Attr |= AttrOnList
 			if Ctxt.Etextp != nil {
 				Ctxt.Etextp.Next = s
 			} else {
@@ -439,10 +439,10 @@ func ldpe(f *obj.Biobuf, pkg string, length int64, pn string) {
 			}
 			Ctxt.Etextp = s
 			for s = s.Sub; s != nil; s = s.Sub {
-				if s.Onlist != 0 {
+				if s.Attr.OnList() {
 					log.Fatalf("symbol %s listed multiple times", s.Name)
 				}
-				s.Onlist = 1
+				s.Attr |= AttrOnList
 				Ctxt.Etextp.Next = s
 				Ctxt.Etextp = s
 			}
@@ -515,7 +515,7 @@ func readpesym(peobj *PeObj, i int, y **PeSym) (err error) {
 
 		case IMAGE_SYM_CLASS_NULL, IMAGE_SYM_CLASS_STATIC, IMAGE_SYM_CLASS_LABEL:
 			s = Linklookup(Ctxt, name, Ctxt.Version)
-			s.Dupok = 1
+			s.Attr |= AttrDuplicateOK
 
 		default:
 			err = fmt.Errorf("%s: invalid symbol binding %d", sym.name, sym.sclass)

src/cmd/link/internal/ld/lib.go

@@ -225,12 +225,6 @@ var (
 	liveness           int64
 )
 
-// for dynexport field of LSym
-const (
-	CgoExportDynamic = 1 << 0
-	CgoExportStatic  = 1 << 1
-)
-
 var (
 	Segtext   Segment
 	Segrodata Segment
@@ -499,11 +493,11 @@ func loadlib() {
 	switch Buildmode {
 	case BuildmodeCShared:
 		s := Linklookup(Ctxt, "runtime.islibrary", 0)
-		s.Dupok = 1
+		s.Attr |= AttrDuplicateOK
 		Adduint8(Ctxt, s, 1)
 	case BuildmodeCArchive:
 		s := Linklookup(Ctxt, "runtime.isarchive", 0)
-		s.Dupok = 1
+		s.Attr |= AttrDuplicateOK
 		Adduint8(Ctxt, s, 1)
 	}
 
@@ -605,7 +599,7 @@ func loadlib() {
 				// cgo_import_static and cgo_import_dynamic,
 				// then we want to make it cgo_import_dynamic
 				// now.
-				if s.Extname != "" && s.Dynimplib != "" && s.Cgoexport == 0 {
+				if s.Extname != "" && s.Dynimplib != "" && !s.Attr.CgoExport() {
 					s.Type = obj.SDYNIMPORT
 				} else {
 					s.Type = 0
@@ -624,7 +618,7 @@ func loadlib() {
 	} else if tlsg.Type != obj.SDYNIMPORT {
 		Diag("internal error: runtime declared tlsg variable %d", tlsg.Type)
 	}
-	tlsg.Reachable = true
+	tlsg.Attr |= AttrReachable
 	Ctxt.Tlsg = tlsg
 
 	moduledata := Linklookup(Ctxt, "runtime.firstmoduledata", 0)
@@ -649,23 +643,23 @@ func loadlib() {
 		// If OTOH the module does not contain the runtime package,
 		// create a local symbol for the moduledata.
 		moduledata = Linklookup(Ctxt, "local.moduledata", 0)
-		moduledata.Local = true
+		moduledata.Attr |= AttrLocal
 	}
 	// In all cases way we mark the moduledata as noptrdata to hide it from
 	// the GC.
 	moduledata.Type = obj.SNOPTRDATA
-	moduledata.Reachable = true
+	moduledata.Attr |= AttrReachable
 	Ctxt.Moduledata = moduledata
 
 	// Now that we know the link mode, trim the dynexp list.
-	x := CgoExportDynamic
+	x := AttrCgoExportDynamic
 
 	if Linkmode == LinkExternal {
-		x = CgoExportStatic
+		x = AttrCgoExportStatic
 	}
 	w := 0
 	for i := 0; i < len(dynexp); i++ {
-		if int(dynexp[i].Cgoexport)&x != 0 {
+		if dynexp[i].Attr&x != 0 {
 			dynexp[w] = dynexp[i]
 			w++
 		}
@@ -1671,7 +1665,7 @@ func dostkcheck() {
 			continue
 		}
 
-		if s.Nosplit != 0 {
+		if s.Attr.NoSplit() {
 			Ctxt.Cursym = s
 			ch.sym = s
 			stkcheck(&ch, 0)
@@ -1679,7 +1673,7 @@ func dostkcheck() {
 	}
 
 	for s := Ctxt.Textp; s != nil; s = s.Next {
-		if s.Nosplit == 0 {
+		if !s.Attr.NoSplit() {
 			Ctxt.Cursym = s
 			ch.sym = s
 			stkcheck(&ch, 0)
@@ -1695,10 +1689,10 @@ func stkcheck(up *Chain, depth int) int {
 	// function at top of safe zone once.
 	top := limit == obj.StackLimit-callsize()
 	if top {
-		if s.Stkcheck != 0 {
+		if s.Attr.StackCheck() {
 			return 0
 		}
-		s.Stkcheck = 1
+		s.Attr |= AttrStackCheck
 	}
 
 	if depth > 100 {
@@ -1707,7 +1701,7 @@ func stkcheck(up *Chain, depth int) int {
 		return -1
 	}
 
-	if s.External != 0 || s.Pcln == nil {
+	if s.Attr.External() || s.Pcln == nil {
 		// external function.
 		// should never be called directly.
 		// only diagnose the direct caller.
@@ -1733,7 +1727,7 @@ func stkcheck(up *Chain, depth int) int {
 	var ch Chain
 	ch.up = up
 
-	if s.Nosplit == 0 {
+	if !s.Attr.NoSplit() {
 		// Ensure we have enough stack to call morestack.
 		ch.limit = limit - callsize()
 		ch.sym = morestack
@@ -1806,7 +1800,7 @@ func stkprint(ch *Chain, limit int) {
 
 	if ch.sym != nil {
 		name = ch.sym.Name
-		if ch.sym.Nosplit != 0 {
+		if ch.sym.Attr.NoSplit() {
 			name += " (nosplit)"
 		}
 	} else {
@@ -1815,7 +1809,7 @@ func stkprint(ch *Chain, limit int) {
 
 	if ch.up == nil {
 		// top of chain.  ch->sym != nil.
-		if ch.sym.Nosplit != 0 {
+		if ch.sym.Attr.NoSplit() {
 			fmt.Printf("\t%d\tassumed on entry to %s\n", ch.limit, name)
 		} else {
 			fmt.Printf("\t%d\tguaranteed after split check in %s\n", ch.limit, name)
@@ -1905,7 +1899,10 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 	}
 
 	for _, s := range Ctxt.Allsym {
-		if s.Hidden || ((s.Name == "" || s.Name[0] == '.') && s.Version == 0 && s.Name != ".rathole" && s.Name != ".TOC.") {
+		if s.Attr.Hidden() {
+			continue
+		}
+		if (s.Name == "" || s.Name[0] == '.') && s.Version == 0 && s.Name != ".rathole" && s.Name != ".TOC." {
 			continue
 		}
 		switch s.Type & obj.SMASK {
@@ -1931,17 +1928,17 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 			obj.SRODATARELRO,
 			obj.STYPELINK,
 			obj.SWINDOWS:
-			if !s.Reachable {
+			if !s.Attr.Reachable() {
 				continue
 			}
 			put(s, s.Name, 'D', Symaddr(s), s.Size, int(s.Version), s.Gotype)
 
 		case obj.SBSS, obj.SNOPTRBSS:
-			if !s.Reachable {
+			if !s.Attr.Reachable() {
 				continue
 			}
 			if len(s.P) > 0 {
-				Diag("%s should not be bss (size=%d type=%d special=%d)", s.Name, int(len(s.P)), s.Type, s.Special)
+				Diag("%s should not be bss (size=%d type=%d special=%v)", s.Name, int(len(s.P)), s.Type, s.Attr.Special())
 			}
 			put(s, s.Name, 'B', Symaddr(s), s.Size, int(s.Version), s.Gotype)
 
@@ -1954,7 +1951,7 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 			}
 
 		case obj.SDYNIMPORT:
-			if !s.Reachable {
+			if !s.Attr.Reachable() {
 				continue
 			}
 			put(s, s.Extname, 'U', 0, 0, int(s.Version), nil)
@@ -2011,7 +2008,7 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 }
 
 func Symaddr(s *LSym) int64 {
-	if !s.Reachable {
+	if !s.Attr.Reachable() {
 		Diag("unreachable symbol in symaddr - %s", s.Name)
 	}
 	return s.Value
@@ -2021,9 +2018,9 @@ func xdefine(p string, t int, v int64) {
 	s := Linklookup(Ctxt, p, 0)
 	s.Type = int16(t)
 	s.Value = v
-	s.Reachable = true
-	s.Special = 1
-	s.Local = true
+	s.Attr |= AttrReachable
+	s.Attr |= AttrSpecial
+	s.Attr |= AttrLocal
 }
 
 func datoff(addr int64) int64 {
@@ -2064,7 +2061,7 @@ func undefsym(s *LSym) {
 		if r.Sym.Type == obj.Sxxx || r.Sym.Type == obj.SXREF {
 			Diag("undefined: %s", r.Sym.Name)
 		}
-		if !r.Sym.Reachable {
+		if !r.Sym.Attr.Reachable() {
 			Diag("use of unreachable symbol: %s", r.Sym.Name)
 		}
 	}

src/cmd/link/internal/ld/link.go

@@ -38,25 +38,12 @@ import (
 )
 
 type LSym struct {
-	Name       string
-	Extname    string
-	Type       int16
-	Version    int16
-	Dupok      uint8
-	External   uint8
-	Nosplit    uint8
-	Reachable  bool
-	Cgoexport  uint8
-	Special    uint8
-	Stkcheck   uint8
-	Hidden     bool
-	Leaf       uint8
-	Localentry uint8
-	Onlist     uint8
-	// ElfType is set for symbols read from shared libraries by ldshlibsyms. It
-	// is not set for symbols defined by the packages being linked or by symbols
-	// read by ldelf (and so is left as elf.STT_NOTYPE).
-	ElfType     elf.SymType
+	Name        string
+	Extname     string
+	Type        int16
+	Version     int16
+	Attr        Attribute
+	Localentry  uint8
 	Dynid       int32
 	Plt         int32
 	Got         int32
@@ -67,6 +54,10 @@ type LSym struct {
 	Locals      int32
 	Value       int64
 	Size        int64
+	// ElfType is set for symbols read from shared libraries by ldshlibsyms. It
+	// is not set for symbols defined by the packages being linked or by symbols
+	// read by ldelf (and so is left as elf.STT_NOTYPE).
+	ElfType     elf.SymType
 	Next        *LSym
 	Sub         *LSym
 	Outer       *LSym
@@ -81,7 +72,6 @@ type LSym struct {
 	Pcln        *Pcln
 	P           []byte
 	R           []Reloc
-	Local       bool
 }
 
 func (s *LSym) String() string {
@@ -101,6 +91,47 @@ func (s *LSym) ElfsymForReloc() int32 {
 	}
 }
 
+// Attribute is a set of common symbol attributes.
+type Attribute int16
+
+const (
+	AttrDuplicateOK Attribute = 1 << iota
+	AttrExternal
+	AttrNoSplit
+	AttrReachable
+	AttrCgoExportDynamic
+	AttrCgoExportStatic
+	AttrSpecial
+	AttrStackCheck
+	AttrHidden
+	AttrOnList
+	AttrLocal
+)
+
+func (a Attribute) DuplicateOK() bool      { return a&AttrDuplicateOK != 0 }
+func (a Attribute) External() bool         { return a&AttrExternal != 0 }
+func (a Attribute) NoSplit() bool          { return a&AttrNoSplit != 0 }
+func (a Attribute) Reachable() bool        { return a&AttrReachable != 0 }
+func (a Attribute) CgoExportDynamic() bool { return a&AttrCgoExportDynamic != 0 }
+func (a Attribute) CgoExportStatic() bool  { return a&AttrCgoExportStatic != 0 }
+func (a Attribute) Special() bool          { return a&AttrSpecial != 0 }
+func (a Attribute) StackCheck() bool       { return a&AttrStackCheck != 0 }
+func (a Attribute) Hidden() bool           { return a&AttrHidden != 0 }
+func (a Attribute) OnList() bool           { return a&AttrOnList != 0 }
+func (a Attribute) Local() bool            { return a&AttrLocal != 0 }
+
+func (a Attribute) CgoExport() bool {
+	return a.CgoExportDynamic() || a.CgoExportStatic()
+}
+
+func (a *Attribute) Set(flag Attribute, value bool) {
+	if value {
+		*a |= flag
+	} else {
+		*a &= ^flag
+	}
+}
+
 type Reloc struct {
 	Off     int32
 	Siz     uint8

src/cmd/link/internal/ld/macho.go

@@ -308,31 +308,31 @@ func domacho() {
 	s := Linklookup(Ctxt, ".machosymstr", 0)
 
 	s.Type = obj.SMACHOSYMSTR
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	Adduint8(Ctxt, s, ' ')
 	Adduint8(Ctxt, s, '\x00')
 
 	s = Linklookup(Ctxt, ".machosymtab", 0)
 	s.Type = obj.SMACHOSYMTAB
-	s.Reachable = true
+	s.Attr |= AttrReachable
 
 	if Linkmode != LinkExternal {
 		s := Linklookup(Ctxt, ".plt", 0) // will be __symbol_stub
 		s.Type = obj.SMACHOPLT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 
 		s = Linklookup(Ctxt, ".got", 0) // will be __nl_symbol_ptr
 		s.Type = obj.SMACHOGOT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		s.Align = 4
 
 		s = Linklookup(Ctxt, ".linkedit.plt", 0) // indirect table for .plt
 		s.Type = obj.SMACHOINDIRECTPLT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 
 		s = Linklookup(Ctxt, ".linkedit.got", 0) // indirect table for .got
 		s.Type = obj.SMACHOINDIRECTGOT
-		s.Reachable = true
+		s.Attr |= AttrReachable
 	}
 }
 
@@ -600,7 +600,7 @@ func symkind(s *LSym) int {
 	if s.Type == obj.SDYNIMPORT {
 		return SymKindUndef
 	}
-	if s.Cgoexport != 0 {
+	if s.Attr.CgoExport() {
 		return SymKindExtdef
 	}
 	return SymKindLocal
@@ -654,7 +654,7 @@ func machogenasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 	genasmsym(put)
 	for _, s := range Ctxt.Allsym {
 		if s.Type == obj.SDYNIMPORT || s.Type == obj.SHOSTOBJ {
-			if s.Reachable {
+			if s.Attr.Reachable() {
 				put(s, "", 'D', 0, 0, 0, nil)
 			}
 		}
@@ -666,7 +666,7 @@ func machosymorder() {
 	// So we sort them here and pre-allocate dynid for them
 	// See https://golang.org/issue/4029
 	for i := 0; i < len(dynexp); i++ {
-		dynexp[i].Reachable = true
+		dynexp[i].Attr |= AttrReachable
 	}
 	machogenasmsym(addsym)
 	sortsym = make([]*LSym, nsortsym)
@@ -717,7 +717,7 @@ func machosymtab() {
 			Adduint16(Ctxt, symtab, 0)                  // desc
 			adduintxx(Ctxt, symtab, 0, Thearch.Ptrsize) // no value
 		} else {
-			if s.Cgoexport != 0 {
+			if s.Attr.CgoExport() {
 				Adduint8(Ctxt, symtab, 0x0f)
 			} else {
 				Adduint8(Ctxt, symtab, 0x0e)
@@ -829,7 +829,7 @@ func machorelocsect(sect *Section, first *LSym) {
 	sect.Reloff = uint64(Cpos())
 	var sym *LSym
 	for sym = first; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if uint64(sym.Value) >= sect.Vaddr {
@@ -841,7 +841,7 @@ func machorelocsect(sect *Section, first *LSym) {
 	var r *Reloc
 	var ri int
 	for ; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if sym.Value >= int64(eaddr) {

src/cmd/link/internal/ld/objfile.go

@@ -171,11 +171,8 @@ func readsym(ctxt *Link, f *obj.Biobuf, pkg string, pn string) {
 		log.Fatalf("invalid symbol version %d", v)
 	}
 	flags := rdint(f)
-	dupok := flags & 1
-	local := false
-	if flags&2 != 0 {
-		local = true
-	}
+	dupok := flags&1 != 0
+	local := flags&2 != 0
 	size := rdint(f)
 	typ := rdsym(ctxt, f, pkg)
 	data := rddata(f)
@@ -200,7 +197,7 @@ func readsym(ctxt *Link, f *obj.Biobuf, pkg string, pn string) {
 		if (s.Type == obj.SDATA || s.Type == obj.SBSS || s.Type == obj.SNOPTRBSS) && len(s.P) == 0 && len(s.R) == 0 {
 			goto overwrite
 		}
-		if s.Type != obj.SBSS && s.Type != obj.SNOPTRBSS && dupok == 0 && s.Dupok == 0 {
+		if s.Type != obj.SBSS && s.Type != obj.SNOPTRBSS && !dupok && !s.Attr.DuplicateOK() {
 			log.Fatalf("duplicate symbol %s (types %d and %d) in %s and %s", s.Name, s.Type, t, s.File, pn)
 		}
 		if len(s.P) > 0 {
@@ -212,7 +209,9 @@ func readsym(ctxt *Link, f *obj.Biobuf, pkg string, pn string) {
 
 overwrite:
 	s.File = pkg
-	s.Dupok = uint8(dupok)
+	if dupok {
+		s.Attr |= AttrDuplicateOK
+	}
 	if t == obj.SXREF {
 		log.Fatalf("bad sxref")
 	}
@@ -226,7 +225,7 @@ overwrite:
 	if s.Size < int64(size) {
 		s.Size = int64(size)
 	}
-	s.Local = local
+	s.Attr.Set(AttrLocal, local)
 	if typ != nil { // if bss sym defined multiple times, take type from any one def
 		s.Gotype = typ
 	}
@@ -262,9 +261,10 @@ overwrite:
 	if s.Type == obj.STEXT {
 		s.Args = rdint32(f)
 		s.Locals = rdint32(f)
-		s.Nosplit = rduint8(f)
-		v := rdint(f)
-		s.Leaf = uint8(v & 1)
+		if rduint8(f) != 0 {
+			s.Attr |= AttrNoSplit
+		}
+		rdint(f) // v&1 is Leaf, currently unused
 		n := rdint(f)
 		var a *Auto
 		for i := 0; i < n; i++ {
@@ -306,10 +306,10 @@ overwrite:
 		}
 
 		if dup == nil {
-			if s.Onlist != 0 {
+			if s.Attr.OnList() {
 				log.Fatalf("symbol %s listed multiple times", s.Name)
 			}
-			s.Onlist = 1
+			s.Attr |= AttrOnList
 			if ctxt.Etextp != nil {
 				ctxt.Etextp.Next = s
 			} else {
@@ -327,10 +327,10 @@ overwrite:
 		if s.Type != 0 {
 			fmt.Fprintf(ctxt.Bso, "t=%d ", s.Type)
 		}
-		if s.Dupok != 0 {
+		if s.Attr.DuplicateOK() {
 			fmt.Fprintf(ctxt.Bso, "dupok ")
 		}
-		if s.Nosplit != 0 {
+		if s.Attr.NoSplit() {
 			fmt.Fprintf(ctxt.Bso, "nosplit ")
 		}
 		fmt.Fprintf(ctxt.Bso, "size=%d value=%d", int64(s.Size), int64(s.Value))
@@ -501,20 +501,20 @@ func rdsym(ctxt *Link, f *obj.Biobuf, pkg string) *LSym {
 			x, _ := strconv.ParseUint(s.Name[5:], 16, 32)
 			i32 := int32(x)
 			s.Type = obj.SRODATA
-			s.Local = true
+			s.Attr |= AttrLocal
 			Adduint32(ctxt, s, uint32(i32))
-			s.Reachable = false
+			s.Attr.Set(AttrReachable, false)
 		} else if strings.HasPrefix(s.Name, "$f64.") || strings.HasPrefix(s.Name, "$i64.") {
 			x, _ := strconv.ParseUint(s.Name[5:], 16, 64)
 			i64 := int64(x)
 			s.Type = obj.SRODATA
-			s.Local = true
+			s.Attr |= AttrLocal
 			Adduint64(ctxt, s, uint64(i64))
-			s.Reachable = false
+			s.Attr.Set(AttrReachable, false)
 		}
 	}
 	if v == 0 && strings.HasPrefix(s.Name, "runtime.gcbits.") {
-		s.Local = true
+		s.Attr |= AttrLocal
 	}
 	return s
 }

src/cmd/link/internal/ld/pcln.go

@@ -218,7 +218,7 @@ func pclntab() {
 	funcdata_bytes := int64(0)
 	ftab := Linklookup(Ctxt, "runtime.pclntab", 0)
 	ftab.Type = obj.SPCLNTAB
-	ftab.Reachable = true
+	ftab.Attr |= AttrReachable
 
 	// See golang.org/s/go12symtab for the format. Briefly:
 	//	8-byte header
@@ -403,8 +403,8 @@ const (
 func findfunctab() {
 	t := Linklookup(Ctxt, "runtime.findfunctab", 0)
 	t.Type = obj.SRODATA
-	t.Reachable = true
-	t.Local = true
+	t.Attr |= AttrReachable
+	t.Attr |= AttrLocal
 
 	// find min and max address
 	min := Ctxt.Textp.Value

src/cmd/link/internal/ld/pe.go

@@ -488,7 +488,7 @@ func initdynimport() *Dll {
 	dr = nil
 	var m *Imp
 	for _, s := range Ctxt.Allsym {
-		if !s.Reachable || s.Type != obj.SDYNIMPORT {
+		if !s.Attr.Reachable() || s.Type != obj.SDYNIMPORT {
 			continue
 		}
 		for d = dr; d != nil; d = d.next {
@@ -538,7 +538,7 @@ func initdynimport() *Dll {
 					dynName += fmt.Sprintf("@%d", m.argsize)
 				}
 				dynSym := Linklookup(Ctxt, dynName, 0)
-				dynSym.Reachable = true
+				dynSym.Attr |= AttrReachable
 				dynSym.Type = obj.SHOSTOBJ
 				r := Addrel(m.s)
 				r.Sym = dynSym
@@ -549,7 +549,7 @@ func initdynimport() *Dll {
 		}
 	} else {
 		dynamic := Linklookup(Ctxt, ".windynamic", 0)
-		dynamic.Reachable = true
+		dynamic.Attr |= AttrReachable
 		dynamic.Type = obj.SWINDOWS
 		for d := dr; d != nil; d = d.next {
 			for m = d.ms; m != nil; m = m.next {
@@ -693,7 +693,7 @@ func (s byExtname) Less(i, j int) bool { return s[i].Extname < s[j].Extname }
 func initdynexport() {
 	nexport = 0
 	for _, s := range Ctxt.Allsym {
-		if !s.Reachable || s.Cgoexport&CgoExportDynamic == 0 {
+		if !s.Attr.Reachable() || !s.Attr.CgoExportDynamic() {
 			continue
 		}
 		if nexport+1 > len(dexport) {
@@ -785,7 +785,7 @@ func perelocsect(sect *Section, first *LSym) int {
 	sect.Reloff = uint64(Cpos())
 	var sym *LSym
 	for sym = first; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if uint64(sym.Value) >= sect.Vaddr {
@@ -797,7 +797,7 @@ func perelocsect(sect *Section, first *LSym) int {
 	var r *Reloc
 	var ri int
 	for ; sym != nil; sym = sym.Next {
-		if !sym.Reachable {
+		if !sym.Attr.Reachable() {
 			continue
 		}
 		if sym.Value >= int64(eaddr) {
@@ -888,7 +888,7 @@ func dope() {
 	/* relocation table */
 	rel := Linklookup(Ctxt, ".rel", 0)
 
-	rel.Reachable = true
+	rel.Attr |= AttrReachable
 	rel.Type = obj.SELFROSECT
 
 	initdynimport()
@@ -941,7 +941,7 @@ func addpesym(s *LSym, name string, type_ int, addr int64, size int64, ver int,
 
 	if coffsym != nil {
 		// only windows/386 requires underscore prefix on external symbols
-		if Thearch.Thechar == '8' && Linkmode == LinkExternal && (s.Type == obj.SHOSTOBJ || s.Cgoexport != 0) && s.Name == s.Extname {
+		if Thearch.Thechar == '8' && Linkmode == LinkExternal && (s.Type == obj.SHOSTOBJ || s.Attr.CgoExport()) && s.Name == s.Extname {
 			s.Name = "_" + s.Name
 		}
 		cs := &coffsym[ncoffsym]

src/cmd/link/internal/ld/symtab.go

@@ -142,7 +142,7 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 	// maybe one day STB_WEAK.
 	bind := STB_GLOBAL
 
-	if ver != 0 || (x.Type&obj.SHIDDEN != 0) || x.Local {
+	if ver != 0 || (x.Type&obj.SHIDDEN != 0) || x.Attr.Local() {
 		bind = STB_LOCAL
 	}
 
@@ -151,7 +151,7 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 	// To avoid filling the dynamic table with lots of unnecessary symbols,
 	// mark all Go symbols local (not global) in the final executable.
 	// But when we're dynamically linking, we need all those global symbols.
-	if !DynlinkingGo() && Linkmode == LinkExternal && x.Cgoexport&CgoExportStatic == 0 && elfshnum != SHN_UNDEF {
+	if !DynlinkingGo() && Linkmode == LinkExternal && !x.Attr.CgoExportStatic() && elfshnum != SHN_UNDEF {
 		bind = STB_LOCAL
 	}
 
@@ -389,13 +389,13 @@ func symtab() {
 
 	s.Type = obj.SRODATA
 	s.Size = 0
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	xdefine("runtime.egcdata", obj.SRODATA, 0)
 
 	s = Linklookup(Ctxt, "runtime.gcbss", 0)
 	s.Type = obj.SRODATA
 	s.Size = 0
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	xdefine("runtime.egcbss", obj.SRODATA, 0)
 
 	// pseudo-symbols to mark locations of type, string, and go string data.
@@ -406,54 +406,54 @@ func symtab() {
 
 		s.Type = obj.STYPE
 		s.Size = 0
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		symtype = s
 
 		s = Linklookup(Ctxt, "typerel.*", 0)
 
 		s.Type = obj.STYPERELRO
 		s.Size = 0
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		symtyperel = s
 	} else if !DynlinkingGo() {
 		s = Linklookup(Ctxt, "type.*", 0)
 
 		s.Type = obj.STYPE
 		s.Size = 0
-		s.Reachable = true
+		s.Attr |= AttrReachable
 		symtype = s
 		symtyperel = s
 	}
 
 	s = Linklookup(Ctxt, "go.string.*", 0)
 	s.Type = obj.SGOSTRING
-	s.Local = true
+	s.Attr |= AttrLocal
 	s.Size = 0
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	symgostring := s
 
 	s = Linklookup(Ctxt, "go.func.*", 0)
 	s.Type = obj.SGOFUNC
-	s.Local = true
+	s.Attr |= AttrLocal
 	s.Size = 0
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	symgofunc := s
 
 	s = Linklookup(Ctxt, "runtime.gcbits.*", 0)
 	s.Type = obj.SGCBITS
-	s.Local = true
+	s.Attr |= AttrLocal
 	s.Size = 0
-	s.Reachable = true
+	s.Attr |= AttrReachable
 	symgcbits := s
 
 	symtypelink := Linklookup(Ctxt, "runtime.typelink", 0)
 	symtypelink.Type = obj.STYPELINK
 
 	symt = Linklookup(Ctxt, "runtime.symtab", 0)
-	symt.Local = true
+	symt.Attr |= AttrLocal
 	symt.Type = obj.SSYMTAB
 	symt.Size = 0
-	symt.Reachable = true
+	symt.Attr |= AttrReachable
 
 	ntypelinks := 0
 
@@ -462,12 +462,12 @@ func symtab() {
 	// just defined above will be first.
 	// hide the specific symbols.
 	for _, s := range Ctxt.Allsym {
-		if !s.Reachable || s.Special != 0 || s.Type != obj.SRODATA {
+		if !s.Attr.Reachable() || s.Attr.Special() || s.Type != obj.SRODATA {
 			continue
 		}
 
 		if strings.HasPrefix(s.Name, "type.") && !DynlinkingGo() {
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			if UseRelro() && len(s.R) > 0 {
 				s.Type = obj.STYPERELRO
 				s.Outer = symtyperel
@@ -480,31 +480,31 @@ func symtab() {
 		if strings.HasPrefix(s.Name, "go.typelink.") {
 			ntypelinks++
 			s.Type = obj.STYPELINK
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			s.Outer = symtypelink
 		}
 
 		if strings.HasPrefix(s.Name, "go.string.") {
 			s.Type = obj.SGOSTRING
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			s.Outer = symgostring
 		}
 
 		if strings.HasPrefix(s.Name, "runtime.gcbits.") {
 			s.Type = obj.SGCBITS
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			s.Outer = symgcbits
 		}
 
 		if strings.HasPrefix(s.Name, "go.func.") {
 			s.Type = obj.SGOFUNC
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			s.Outer = symgofunc
 		}
 
 		if strings.HasPrefix(s.Name, "gcargs.") || strings.HasPrefix(s.Name, "gclocals.") || strings.HasPrefix(s.Name, "gclocals·") {
 			s.Type = obj.SGOFUNC
-			s.Hidden = true
+			s.Attr |= AttrHidden
 			s.Outer = symgofunc
 			s.Align = 4
 			liveness += (s.Size + int64(s.Align) - 1) &^ (int64(s.Align) - 1)
@@ -513,7 +513,7 @@ func symtab() {
 
 	if Buildmode == BuildmodeShared {
 		abihashgostr := Linklookup(Ctxt, "go.link.abihash."+filepath.Base(outfile), 0)
-		abihashgostr.Reachable = true
+		abihashgostr.Attr |= AttrReachable
 		abihashgostr.Type = obj.SRODATA
 		hashsym := Linklookup(Ctxt, "go.link.abihashbytes", 0)
 		Addaddr(Ctxt, abihashgostr, hashsym)
@@ -571,8 +571,8 @@ func symtab() {
 		addgostring(moduledata, "go.link.thismodulename", thismodulename)
 
 		modulehashes := Linklookup(Ctxt, "go.link.abihashes", 0)
-		modulehashes.Reachable = true
-		modulehashes.Local = true
+		modulehashes.Attr |= AttrReachable
+		modulehashes.Attr |= AttrLocal
 		modulehashes.Type = obj.SRODATA
 
 		for i, shlib := range Ctxt.Shlibs {
@@ -585,7 +585,7 @@ func symtab() {
 
 			// modulehashes[i].runtimehash
 			abihash := Linklookup(Ctxt, "go.link.abihash."+modulename, 0)
-			abihash.Reachable = true
+			abihash.Attr |= AttrReachable
 			Addaddr(Ctxt, modulehashes, abihash)
 		}
 

src/cmd/link/internal/ppc64/asm.go

@@ -112,7 +112,9 @@ func genplt() {
 			n = fmt.Sprintf("%s.%s", s.Name, r.Sym.Name)
 
 			stub = ld.Linklookup(ld.Ctxt, n, 0)
-			stub.Reachable = stub.Reachable || s.Reachable
+			if s.Attr.Reachable() {
+				stub.Attr |= ld.AttrReachable
+			}
 			if stub.Size == 0 {
 				// Need outer to resolve .TOC.
 				stub.Outer = s
@@ -145,11 +147,11 @@ func genaddmoduledata() {
 	if addmoduledata.Type == obj.STEXT {
 		return
 	}
-	addmoduledata.Reachable = true
+	addmoduledata.Attr |= ld.AttrReachable
 	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
 	initfunc.Type = obj.STEXT
-	initfunc.Local = true
-	initfunc.Reachable = true
+	initfunc.Attr |= ld.AttrLocal
+	initfunc.Attr |= ld.AttrReachable
 	o := func(op uint32) {
 		ld.Adduint32(ld.Ctxt, initfunc, op)
 	}
@@ -201,8 +203,8 @@ func genaddmoduledata() {
 	ld.Ctxt.Etextp = initfunc
 
 	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
-	initarray_entry.Reachable = true
-	initarray_entry.Local = true
+	initarray_entry.Attr |= ld.AttrReachable
+	initarray_entry.Attr |= ld.AttrLocal
 	initarray_entry.Type = obj.SINITARR
 	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }

src/cmd/link/internal/x86/asm.go

@@ -39,7 +39,7 @@ import (
 
 // Append 4 bytes to s and create a R_CALL relocation targeting t to fill them in.
 func addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) {
-	s.Reachable = true
+	s.Attr |= ld.AttrReachable
 	i := s.Size
 	s.Size += 4
 	ld.Symgrow(ctxt, s, s.Size)
@@ -57,8 +57,8 @@ func gentext() {
 
 	thunkfunc := ld.Linklookup(ld.Ctxt, "__x86.get_pc_thunk.cx", 0)
 	thunkfunc.Type = obj.STEXT
-	thunkfunc.Local = true
-	thunkfunc.Reachable = true
+	thunkfunc.Attr |= ld.AttrLocal
+	thunkfunc.Attr |= ld.AttrReachable
 	o := func(op ...uint8) {
 		for _, op1 := range op {
 			ld.Adduint8(ld.Ctxt, thunkfunc, op1)
@@ -83,12 +83,12 @@ func gentext() {
 		return
 	}
 
-	addmoduledata.Reachable = true
+	addmoduledata.Attr |= ld.AttrReachable
 
 	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
 	initfunc.Type = obj.STEXT
-	initfunc.Local = true
-	initfunc.Reachable = true
+	initfunc.Attr |= ld.AttrLocal
+	initfunc.Attr |= ld.AttrReachable
 	o = func(op ...uint8) {
 		for _, op1 := range op {
 			ld.Adduint8(ld.Ctxt, initfunc, op1)
@@ -133,8 +133,8 @@ func gentext() {
 	ld.Ctxt.Etextp.Next = initfunc
 	ld.Ctxt.Etextp = initfunc
 	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
-	initarray_entry.Reachable = true
-	initarray_entry.Local = true
+	initarray_entry.Attr |= ld.AttrReachable
+	initarray_entry.Attr |= ld.AttrLocal
 	initarray_entry.Type = obj.SINITARR
 	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
 }

src/cmd/link/internal/x86/obj.go

@@ -93,7 +93,7 @@ func archinit() {
 		ld.Linkmode = ld.LinkExternal
 		got := ld.Linklookup(ld.Ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
 		got.Type = obj.SDYNIMPORT
-		got.Reachable = true
+		got.Attr |= ld.AttrReachable
 	}
 
 	switch ld.HEADTYPE {