[dev.link] cmd/link: remove implicit reachability setting from SymbolBuilder

The loader's SymbolBuilder Add*/Set* methods include a call to mark
the underlying symbol as reachable (as a convenience, so that callers
would not have to set it explicitly). This code was carried over from
the corresponding sym.Symbol methods; back in the sym.Symbol world
unreachable symbols were never removed from the AllSyms slice, hence
setting and checking reachability was a good deal more important.

With the advent of the loader and the new deadcode implementation,
there is less of a need for this sort of fallback, and in addition the
implicit attr setting introduces data races in the the loader if there
are SymbolBuilder Add*/Set* method calls in parallel threads, as well
as adding overhead to the methods.

This patch gets rid of the implicit reachability setting, and instead
marks reachability in CreateSymForUpdate, as well as adding a few
explicit SetAttrReachable calls where needed.

Change-Id: I029a0c5a4a24237826a7831f9cbe5180d44cbc40
Reviewed-on: https://go-review.googlesource.com/c/go/+/237678
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

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

@@ -387,6 +387,7 @@ func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
 				oName := ldr.SymName(rs)
 				name := oName + fmt.Sprintf("%+d-tramp%d", offset, i)
 				tramp = ldr.LookupOrCreateSym(name, int(ldr.SymVersion(rs)))
+				ldr.SetAttrReachable(tramp, true)
 				if ldr.SymType(tramp) == sym.SDYNIMPORT {
 					// don't reuse trampoline defined in other module
 					continue

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

@@ -740,15 +740,14 @@ func (ctxt *Link) windynrelocsyms() {
 		return
 	}
 
-	rel := ctxt.loader.LookupOrCreateSym(".rel", 0)
+	rel := ctxt.loader.CreateSymForUpdate(".rel", 0)
-	relu := ctxt.loader.MakeSymbolUpdater(rel)
+	rel.SetType(sym.STEXT)
-	relu.SetType(sym.STEXT)
 
 	for _, s := range ctxt.Textp {
-		windynrelocsym(ctxt, relu, s)
+		windynrelocsym(ctxt, rel, s)
 	}
 
-	ctxt.Textp = append(ctxt.Textp, rel)
+	ctxt.Textp = append(ctxt.Textp, rel.Sym())
 }
 
 func dynrelocsym(ctxt *Link, s loader.Sym) {
@@ -1042,9 +1041,7 @@ func addstrdata(arch *sys.Arch, l *loader.Loader, name, value string) {
 	}
 
 	p := fmt.Sprintf("%s.str", name)
-	sp := l.LookupOrCreateSym(p, 0)
+	sbld := l.CreateSymForUpdate(p, 0)
-	sbld := l.MakeSymbolUpdater(sp)
-
 	sbld.Addstring(value)
 	sbld.SetType(sym.SRODATA)
 
@@ -1052,7 +1049,7 @@ func addstrdata(arch *sys.Arch, l *loader.Loader, name, value string) {
 	bld.SetData(make([]byte, 0, arch.PtrSize*2))
 	bld.SetReadOnly(false)
 	bld.SetRelocs(nil)
-	bld.AddAddrPlus(arch, sp, 0)
+	bld.AddAddrPlus(arch, sbld.Sym(), 0)
 	bld.AddUint(arch, uint64(len(value)))
 }
 
@@ -1069,7 +1066,6 @@ func addgostring(ctxt *Link, ldr *loader.Loader, s *loader.SymbolBuilder, symnam
 	if sdata.Type() != sym.Sxxx {
 		ctxt.Errorf(s.Sym(), "duplicate symname in addgostring: %s", symname)
 	}
-	sdata.SetReachable(true)
 	sdata.SetLocal(true)
 	sdata.SetType(sym.SRODATA)
 	sdata.SetSize(int64(len(str)))
@@ -1126,8 +1122,7 @@ type GCProg struct {
 
 func (p *GCProg) Init(ctxt *Link, name string) {
 	p.ctxt = ctxt
-	symIdx := ctxt.loader.LookupOrCreateSym(name, 0)
+	p.sym = ctxt.loader.CreateSymForUpdate(name, 0)
-	p.sym = ctxt.loader.MakeSymbolUpdater(symIdx)
 	p.w.Init(p.writeByte())
 	if debugGCProg {
 		fmt.Fprintf(os.Stderr, "ld: start GCProg %s\n", name)
@@ -2059,7 +2054,6 @@ func (ctxt *Link) textbuildid() {
 
 	ldr := ctxt.loader
 	s := ldr.CreateSymForUpdate("go.buildid", 0)
-	s.SetReachable(true)
 	// 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(*flagBuildid) + "\n \xff"
@@ -2083,7 +2077,6 @@ func (ctxt *Link) buildinfo() {
 
 	ldr := ctxt.loader
 	s := ldr.CreateSymForUpdate(".go.buildinfo", 0)
-	s.SetReachable(true)
 	// On AIX, .go.buildinfo must be in the symbol table as
 	// it has relocations.
 	s.SetNotInSymbolTable(!ctxt.IsAIX())
@@ -2231,7 +2224,6 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64
 
 		// Create a symbol for the start of the secondary text sections
 		ntext := ldr.CreateSymForUpdate(fmt.Sprintf("runtime.text.%d", n), 0)
-		ntext.SetReachable(true)
 		ntext.SetSect(sect)
 		if ctxt.IsAIX() {
 			// runtime.text.X must be a real symbol on AIX.

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

@@ -216,11 +216,10 @@ func (dsi *dwarfSecInfo) subSyms() []loader.Sym {
 var dwarfp []dwarfSecInfo
 
 func (d *dwctxt) writeabbrev() dwarfSecInfo {
-	abrvs := d.ldr.LookupOrCreateSym(".debug_abbrev", 0)
+	abrvs := d.ldr.CreateSymForUpdate(".debug_abbrev", 0)
-	u := d.ldr.MakeSymbolUpdater(abrvs)
+	abrvs.SetType(sym.SDWARFSECT)
-	u.SetType(sym.SDWARFSECT)
+	abrvs.AddBytes(dwarf.GetAbbrev())
-	u.AddBytes(dwarf.GetAbbrev())
+	return dwarfSecInfo{syms: []loader.Sym{abrvs.Sym()}}
-	return dwarfSecInfo{syms: []loader.Sym{abrvs}}
 }
 
 var dwtypes dwarf.DWDie
@@ -1624,13 +1623,12 @@ func (d *dwctxt) writegdbscript() dwarfSecInfo {
 		return dwarfSecInfo{}
 	}
 
-	gs := d.ldr.LookupOrCreateSym(".debug_gdb_scripts", 0)
+	gs := d.ldr.CreateSymForUpdate(".debug_gdb_scripts", 0)
-	u := d.ldr.MakeSymbolUpdater(gs)
+	gs.SetType(sym.SDWARFSECT)
-	u.SetType(sym.SDWARFSECT)
 
-	u.AddUint8(1) // magic 1 byte?
+	gs.AddUint8(1) // magic 1 byte?
-	u.Addstring(gdbscript)
+	gs.Addstring(gdbscript)
-	return dwarfSecInfo{syms: []loader.Sym{gs}}
+	return dwarfSecInfo{syms: []loader.Sym{gs.Sym()}}
 }
 
 // FIXME: might be worth looking replacing this map with a function
@@ -1969,17 +1967,13 @@ func (d *dwctxt) dwarfGenerateDebugSyms() {
 	sort.Sort(compilationUnitByStartPC(d.linkctxt.compUnits))
 
 	// Create .debug_line and .debug_ranges section symbols
-	debugLine := d.ldr.LookupOrCreateSym(".debug_line", 0)
+	debugLine := d.ldr.CreateSymForUpdate(".debug_line", 0)
-	dlu := d.ldr.MakeSymbolUpdater(debugLine)
+	debugLine.SetType(sym.SDWARFSECT)
-	dlu.SetType(sym.SDWARFSECT)
+	dwarfp = append(dwarfp, dwarfSecInfo{syms: []loader.Sym{debugLine.Sym()}})
-	d.ldr.SetAttrReachable(debugLine, true)
-	dwarfp = append(dwarfp, dwarfSecInfo{syms: []loader.Sym{debugLine}})
 	linesec := &dwarfp[len(dwarfp)-1]
 
-	debugRanges := d.ldr.LookupOrCreateSym(".debug_ranges", 0)
+	debugRanges := d.ldr.CreateSymForUpdate(".debug_ranges", 0)
-	dru := d.ldr.MakeSymbolUpdater(debugRanges)
+	debugRanges.SetType(sym.SDWARFRANGE)
-	dru.SetType(sym.SDWARFRANGE)
-	d.ldr.SetAttrReachable(debugRanges, true)
 
 	// Write per-package line and range tables and start their CU DIEs.
 	for _, u := range d.linkctxt.compUnits {
@@ -1989,7 +1983,7 @@ func (d *dwctxt) dwarfGenerateDebugSyms() {
 		}
 		linesec.syms = d.writelines(u, linesec.syms)
 		base := loader.Sym(u.Textp[0])
-		d.writepcranges(u, base, u.PCs, debugRanges)
+		d.writepcranges(u, base, u.PCs, debugRanges.Sym())
 	}
 
 	// newdie adds DIEs to the *beginning* of the parent's DIE list.
@@ -1998,12 +1992,12 @@ func (d *dwctxt) dwarfGenerateDebugSyms() {
 	reversetree(&dwtypes.Child)
 	movetomodule(d.linkctxt, &dwtypes)
 
-	infoSym := d.ldr.LookupOrCreateSym(".debug_info", 0)
+	infoSym := d.ldr.CreateSymForUpdate(".debug_info", 0)
 
-	infoSec := d.writeinfo(d.linkctxt.compUnits, abbrevSec.secSym(), infoSym)
+	infoSec := d.writeinfo(d.linkctxt.compUnits, abbrevSec.secSym(), infoSym.Sym())
 
-	frameSym := d.ldr.LookupOrCreateSym(".debug_frame", 0)
+	frameSym := d.ldr.CreateSymForUpdate(".debug_frame", 0)
-	frameSec := d.writeframes(frameSym)
+	frameSec := d.writeframes(frameSym.Sym())
 
 	dwarfp = append(dwarfp, frameSec)
 	gdbScriptSec := d.writegdbscript()
@@ -2011,14 +2005,13 @@ func (d *dwctxt) dwarfGenerateDebugSyms() {
 		dwarfp = append(dwarfp, gdbScriptSec)
 	}
 	dwarfp = append(dwarfp, infoSec)
-	locSym := d.ldr.LookupOrCreateSym(".debug_loc", 0)
+	locSym := d.ldr.CreateSymForUpdate(".debug_loc", 0)
-	d.ldr.SetAttrReachable(locSym, true)
+	locSec := d.collectlocs(locSym.Sym())
-	locSec := d.collectlocs(locSym)
 	if locSec.secSym() != 0 {
 		dwarfp = append(dwarfp, locSec)
 	}
 
-	rsyms := []loader.Sym{debugRanges}
+	rsyms := []loader.Sym{debugRanges.Sym()}
 	for _, unit := range d.linkctxt.compUnits {
 		for _, s := range unit.RangeSyms {
 			rsyms = append(rsyms, loader.Sym(s))
@@ -2145,7 +2138,6 @@ func dwarfcompress(ctxt *Link) {
 			sect.Align = 1
 			sect.Length = uint64(len(z.compressed))
 			newSym := ldr.CreateSymForUpdate(compressedSegName, 0)
-			newSym.SetReachable(true)
 			newSym.SetData(z.compressed)
 			newSym.SetSize(int64(len(z.compressed)))
 			ldr.SetSymSect(newSym.Sym(), sect)

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

@@ -1036,7 +1036,6 @@ func elfdynhash(ctxt *Link) {
 	ldr := ctxt.loader
 	s := ldr.CreateSymForUpdate(".hash", 0)
 	s.SetType(sym.SELFROSECT)
-	s.SetReachable(true)
 
 	i := nsym
 	nbucket := 1
@@ -1434,7 +1433,6 @@ func elfEmitReloc(ctxt *Link) {
 func addgonote(ctxt *Link, sectionName string, tag uint32, desc []byte) {
 	ldr := ctxt.loader
 	s := ldr.CreateSymForUpdate(sectionName, 0)
-	s.SetReachable(true)
 	s.SetType(sym.SELFROSECT)
 	// namesz
 	s.AddUint32(ctxt.Arch, uint32(len(ELF_NOTE_GO_NAME)))
@@ -1463,7 +1461,6 @@ func (ctxt *Link) doelf() {
 	shstrtab := ldr.CreateSymForUpdate(".shstrtab", 0)
 
 	shstrtab.SetType(sym.SELFROSECT)
-	shstrtab.SetReachable(true)
 
 	shstrtab.Addstring("")
 	shstrtab.Addstring(".text")
@@ -1577,7 +1574,6 @@ func (ctxt *Link) doelf() {
 		dynsym := ldr.CreateSymForUpdate(".dynsym", 0)
 
 		dynsym.SetType(sym.SELFROSECT)
-		dynsym.SetReachable(true)
 		if elf64 {
 			dynsym.SetSize(dynsym.Size() + ELF64SYMSIZE)
 		} else {
@@ -1588,39 +1584,32 @@ func (ctxt *Link) doelf() {
 		dynstr := ldr.CreateSymForUpdate(".dynstr", 0)
 
 		dynstr.SetType(sym.SELFROSECT)
-		dynstr.SetReachable(true)
 		if dynstr.Size() == 0 {
 			dynstr.Addstring("")
 		}
 
 		/* relocation table */
 		s := ldr.CreateSymForUpdate(elfRelType, 0)
-		s.SetReachable(true)
 		s.SetType(sym.SELFROSECT)
 
 		/* global offset table */
 		got := ldr.CreateSymForUpdate(".got", 0)
-		got.SetReachable(true)
 		got.SetType(sym.SELFGOT) // writable
 
 		/* ppc64 glink resolver */
 		if ctxt.IsPPC64() {
 			s := ldr.CreateSymForUpdate(".glink", 0)
-			s.SetReachable(true)
 			s.SetType(sym.SELFRXSECT)
 		}
 
 		/* hash */
 		hash := ldr.CreateSymForUpdate(".hash", 0)
-		hash.SetReachable(true)
 		hash.SetType(sym.SELFROSECT)
 
 		gotplt := ldr.CreateSymForUpdate(".got.plt", 0)
-		gotplt.SetReachable(true)
 		gotplt.SetType(sym.SELFSECT) // writable
 
 		plt := ldr.CreateSymForUpdate(".plt", 0)
-		plt.SetReachable(true)
 		if ctxt.IsPPC64() {
 			// In the ppc64 ABI, .plt is a data section
 			// written by the dynamic linker.
@@ -1630,20 +1619,16 @@ func (ctxt *Link) doelf() {
 		}
 
 		s = ldr.CreateSymForUpdate(elfRelType+".plt", 0)
-		s.SetReachable(true)
 		s.SetType(sym.SELFROSECT)
 
 		s = ldr.CreateSymForUpdate(".gnu.version", 0)
-		s.SetReachable(true)
 		s.SetType(sym.SELFROSECT)
 
 		s = ldr.CreateSymForUpdate(".gnu.version_r", 0)
-		s.SetReachable(true)
 		s.SetType(sym.SELFROSECT)
 
 		/* define dynamic elf table */
 		dynamic := ldr.CreateSymForUpdate(".dynamic", 0)
-		dynamic.SetReachable(true)
 		dynamic.SetType(sym.SELFSECT) // writable
 
 		if ctxt.IsS390X() {

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

@@ -2381,7 +2381,6 @@ func (ctxt *Link) xdefine(p string, t sym.SymKind, v int64) {
 	s := ldr.CreateSymForUpdate(p, 0)
 	s.SetType(t)
 	s.SetValue(v)
-	s.SetReachable(true)
 	s.SetSpecial(true)
 	s.SetLocal(true)
 }

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

@@ -585,11 +585,9 @@ const (
 // a given text symbols is a container (outer sym).
 func (ctxt *Link) findfunctab(container loader.Bitmap) {
 	ldr := ctxt.loader
-	tsym := ldr.LookupOrCreateSym("runtime.findfunctab", 0)
+	t := ldr.CreateSymForUpdate("runtime.findfunctab", 0)
-	t := ldr.MakeSymbolUpdater(tsym)
 	t.SetType(sym.SRODATA)
-	ldr.SetAttrReachable(tsym, true)
+	ldr.SetAttrLocal(t.Sym(), true)
-	ldr.SetAttrLocal(tsym, true)
 
 	// find min and max address
 	min := ldr.SymValue(ctxt.Textp[0])

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

@@ -1006,13 +1006,11 @@ func Peinit(ctxt *Link) {
 	if ctxt.LinkMode == LinkInternal {
 		// some mingw libs depend on this symbol, for example, FindPESectionByName
 		for _, name := range [2]string{"__image_base__", "_image_base__"} {
-			s := ctxt.loader.LookupOrCreateSym(name, 0)
+			sb := ctxt.loader.CreateSymForUpdate(name, 0)
-			sb := ctxt.loader.MakeSymbolUpdater(s)
 			sb.SetType(sym.SDATA)
 			sb.SetValue(PEBASE)
-			ctxt.loader.SetAttrReachable(s, true)
+			ctxt.loader.SetAttrSpecial(sb.Sym(), true)
-			ctxt.loader.SetAttrSpecial(s, true)
+			ctxt.loader.SetAttrLocal(sb.Sym(), true)
-			ctxt.loader.SetAttrLocal(s, true)
 		}
 	}
 
@@ -1110,14 +1108,12 @@ func initdynimport(ctxt *Link) *Dll {
 					dynName += fmt.Sprintf("@%d", m.argsize)
 				}
 				dynSym := ldr.CreateSymForUpdate(dynName, 0)
-				dynSym.SetReachable(true)
 				dynSym.SetType(sym.SHOSTOBJ)
 				sb.AddReloc(loader.Reloc{Sym: dynSym.Sym(), Type: objabi.R_ADDR, Off: 0, Size: uint8(ctxt.Arch.PtrSize)})
 			}
 		}
 	} else {
 		dynamic := ldr.CreateSymForUpdate(".windynamic", 0)
-		dynamic.SetReachable(true)
 		dynamic.SetType(sym.SWINDOWS)
 		for d := dr; d != nil; d = d.next {
 			for m = d.ms; m != nil; m = m.next {

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

@@ -345,7 +345,6 @@ func textsectionmap(ctxt *Link) (loader.Sym, uint32) {
 	ldr := ctxt.loader
 	t := ldr.CreateSymForUpdate("runtime.textsectionmap", 0)
 	t.SetType(sym.SRODATA)
-	t.SetReachable(true)
 	nsections := int64(0)
 
 	for _, sect := range Segtext.Sections {
@@ -434,13 +433,11 @@ func (ctxt *Link) symtab() []sym.SymKind {
 	s := ldr.CreateSymForUpdate("runtime.gcdata", 0)
 	s.SetType(sym.SRODATA)
 	s.SetSize(0)
-	s.SetReachable(true)
 	ctxt.xdefine("runtime.egcdata", sym.SRODATA, 0)
 
 	s = ldr.CreateSymForUpdate("runtime.gcbss", 0)
 	s.SetType(sym.SRODATA)
 	s.SetSize(0)
-	s.SetReachable(true)
 	ctxt.xdefine("runtime.egcbss", sym.SRODATA, 0)
 
 	// pseudo-symbols to mark locations of type, string, and go string data.
@@ -450,19 +447,16 @@ func (ctxt *Link) symtab() []sym.SymKind {
 			s = ldr.CreateSymForUpdate("type.*", 0)
 			s.SetType(sym.STYPE)
 			s.SetSize(0)
-			s.SetReachable(true)
 			symtype = s.Sym()
 
 			s = ldr.CreateSymForUpdate("typerel.*", 0)
 			s.SetType(sym.STYPERELRO)
 			s.SetSize(0)
-			s.SetReachable(true)
 			symtyperel = s.Sym()
 		} else {
 			s = ldr.CreateSymForUpdate("type.*", 0)
 			s.SetType(sym.STYPE)
 			s.SetSize(0)
-			s.SetReachable(true)
 			symtype = s.Sym()
 			symtyperel = s.Sym()
 		}
@@ -473,7 +467,6 @@ func (ctxt *Link) symtab() []sym.SymKind {
 		s.SetType(t)
 		s.SetSize(0)
 		s.SetLocal(true)
-		s.SetReachable(true)
 		return s.Sym()
 	}
 	var (
@@ -497,7 +490,6 @@ func (ctxt *Link) symtab() []sym.SymKind {
 	symt := ldr.CreateSymForUpdate("runtime.symtab", 0)
 	symt.SetType(sym.SSYMTAB)
 	symt.SetSize(0)
-	symt.SetReachable(true)
 	symt.SetLocal(true)
 
 	nitablinks := 0
@@ -580,7 +572,6 @@ func (ctxt *Link) symtab() []sym.SymKind {
 
 	if ctxt.BuildMode == BuildModeShared {
 		abihashgostr := ldr.CreateSymForUpdate("go.link.abihash."+filepath.Base(*flagOutfile), 0)
-		abihashgostr.SetReachable(true)
 		abihashgostr.SetType(sym.SRODATA)
 		hashsym := ldr.LookupOrCreateSym("go.link.abihashbytes", 0)
 		abihashgostr.AddAddr(ctxt.Arch, hashsym)
@@ -589,12 +580,10 @@ func (ctxt *Link) symtab() []sym.SymKind {
 	if ctxt.BuildMode == BuildModePlugin || ctxt.CanUsePlugins() {
 		for _, l := range ctxt.Library {
 			s := ldr.CreateSymForUpdate("go.link.pkghashbytes."+l.Pkg, 0)
-			s.SetReachable(true)
 			s.SetType(sym.SRODATA)
 			s.SetSize(int64(len(l.Fingerprint)))
 			s.SetData(l.Fingerprint[:])
 			str := ldr.CreateSymForUpdate("go.link.pkghash."+l.Pkg, 0)
-			str.SetReachable(true)
 			str.SetType(sym.SRODATA)
 			str.AddAddr(ctxt.Arch, s.Sym())
 			str.AddUint(ctxt.Arch, uint64(len(l.Fingerprint)))
@@ -690,7 +679,6 @@ func (ctxt *Link) symtab() []sym.SymKind {
 		addgostring(ctxt, ldr, moduledata, "go.link.thispluginpath", objabi.PathToPrefix(*flagPluginPath))
 
 		pkghashes := ldr.CreateSymForUpdate("go.link.pkghashes", 0)
-		pkghashes.SetReachable(true)
 		pkghashes.SetLocal(true)
 		pkghashes.SetType(sym.SRODATA)
 
@@ -724,7 +712,6 @@ func (ctxt *Link) symtab() []sym.SymKind {
 		addgostring(ctxt, ldr, moduledata, "go.link.thismodulename", thismodulename)
 
 		modulehashes := ldr.CreateSymForUpdate("go.link.abihashes", 0)
-		modulehashes.SetReachable(true)
 		modulehashes.SetLocal(true)
 		modulehashes.SetType(sym.SRODATA)
 

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

@@ -37,7 +37,6 @@ func (ctxt *Link) typelink() {
 
 	tl := ldr.CreateSymForUpdate("runtime.typelink", 0)
 	tl.SetType(sym.STYPELINK)
-	ldr.SetAttrReachable(tl.Sym(), true)
 	ldr.SetAttrLocal(tl.Sym(), true)
 	tl.SetSize(int64(4 * len(typelinks)))
 	tl.Grow(tl.Size())

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

@@ -1173,12 +1173,12 @@ func (f *xcoffFile) adddynimpsym(ctxt *Link, s loader.Sym) {
 	}
 
 	sb := ldr.MakeSymbolUpdater(s)
+	sb.SetReachable(true)
 	sb.SetType(sym.SXCOFFTOC)
 
 	// Create new dynamic symbol
 	extsym := ldr.CreateSymForUpdate(ldr.SymExtname(s), 0)
 	extsym.SetType(sym.SDYNIMPORT)
-	extsym.SetReachable(true)
 	extsym.SetDynimplib(ldr.SymDynimplib(s))
 	extsym.SetExtname(ldr.SymExtname(s))
 	extsym.SetDynimpvers(ldr.SymDynimpvers(s))
@@ -1279,7 +1279,6 @@ func (ctxt *Link) doxcoff() {
 	// TOC
 	toc := ldr.CreateSymForUpdate("TOC", 0)
 	toc.SetType(sym.SXCOFFTOC)
-	toc.SetReachable(true)
 	toc.SetVisibilityHidden(true)
 
 	// Add entry point to .loader symbols.
@@ -1330,6 +1329,7 @@ func (ctxt *Link) doxcoff() {
 				ldr.SetSymExtname(s, "."+name)
 
 				desc := ldr.MakeSymbolUpdater(ldr.CreateExtSym(name, 0))
+				desc.SetReachable(true)
 				desc.SetType(sym.SNOPTRDATA)
 				desc.AddAddr(ctxt.Arch, s)
 				desc.AddAddr(ctxt.Arch, toc.Sym())

src/cmd/link/internal/loader/loader_test.go

@@ -210,11 +210,6 @@ func TestAddMaterializedSymbol(t *testing.T) {
 	if 0 != es1val {
 		t.Errorf("expected IsReflectMethod(es1) value of 0, got %v", irm)
 	}
-
-	// Writing data to a materialized symbol should mark it reachable.
-	if !sb1.Reachable() || !sb2.Reachable() {
-		t.Fatalf("written-to materialized symbols should be reachable")
-	}
 }
 
 func sameRelocSlice(s1 *Relocs, s2 []Reloc) bool {
@@ -347,9 +342,6 @@ func TestAddDataMethods(t *testing.T) {
 			t.Errorf("testing Loader.%s: expected data %v got %v",
 				tp.which, tp.expData, ldr.Data(mi))
 		}
-		if !ldr.AttrReachable(mi) {
-			t.Fatalf("testing Loader.%s: sym updated should be reachable", tp.which)
-		}
 		relocs := ldr.Relocs(mi)
 		if !sameRelocSlice(&relocs, tp.expRel) {
 			t.Fatalf("testing Loader.%s: got relocslice %+v wanted %+v",

src/cmd/link/internal/loader/symbolbuilder.go

@@ -54,7 +54,9 @@ func (l *Loader) MakeSymbolUpdater(symIdx Sym) *SymbolBuilder {
 // returns a CreateSymForUpdate for update. If the symbol already
 // exists, it will update in-place.
 func (l *Loader) CreateSymForUpdate(name string, version int) *SymbolBuilder {
-	return l.MakeSymbolUpdater(l.LookupOrCreateSym(name, version))
+	s := l.LookupOrCreateSym(name, version)
+	l.SetAttrReachable(s, true)
+	return l.MakeSymbolUpdater(s)
 }
 
 // Getters for properties of the symbol we're working on.
@@ -105,7 +107,6 @@ func (sb *SymbolBuilder) SetNotInSymbolTable(value bool) {
 func (sb *SymbolBuilder) SetSect(sect *sym.Section) { sb.l.SetSymSect(sb.symIdx, sect) }
 
 func (sb *SymbolBuilder) AddBytes(data []byte) {
-	sb.setReachable()
 	if sb.kind == 0 {
 		sb.kind = sym.SDATA
 	}
@@ -248,7 +249,6 @@ func (sb *SymbolBuilder) AddUint8(v uint8) int64 {
 	if sb.kind == 0 {
 		sb.kind = sym.SDATA
 	}
-	sb.setReachable()
 	sb.size++
 	sb.data = append(sb.data, v)
 	return off
@@ -256,7 +256,6 @@ func (sb *SymbolBuilder) AddUint8(v uint8) int64 {
 
 func (sb *SymbolBuilder) AddUintXX(arch *sys.Arch, v uint64, wid int) int64 {
 	off := sb.size
-	sb.setReachable()
 	sb.setUintXX(arch, off, v, int64(wid))
 	return off
 }
@@ -301,22 +300,18 @@ func (sb *SymbolBuilder) AddUint(arch *sys.Arch, v uint64) int64 {
 }
 
 func (sb *SymbolBuilder) SetUint8(arch *sys.Arch, r int64, v uint8) int64 {
-	sb.setReachable()
 	return sb.setUintXX(arch, r, uint64(v), 1)
 }
 
 func (sb *SymbolBuilder) SetUint16(arch *sys.Arch, r int64, v uint16) int64 {
-	sb.setReachable()
 	return sb.setUintXX(arch, r, uint64(v), 2)
 }
 
 func (sb *SymbolBuilder) SetUint32(arch *sys.Arch, r int64, v uint32) int64 {
-	sb.setReachable()
 	return sb.setUintXX(arch, r, uint64(v), 4)
 }
 
 func (sb *SymbolBuilder) SetUint(arch *sys.Arch, r int64, v uint64) int64 {
-	sb.setReachable()
 	return sb.setUintXX(arch, r, v, int64(arch.PtrSize))
 }
 
@@ -324,7 +319,6 @@ func (sb *SymbolBuilder) SetAddrPlus(arch *sys.Arch, off int64, tgt Sym, add int
 	if sb.Type() == 0 {
 		sb.SetType(sym.SDATA)
 	}
-	sb.setReachable()
 	if off+int64(arch.PtrSize) > sb.size {
 		sb.size = off + int64(arch.PtrSize)
 		sb.Grow(sb.size)
@@ -344,7 +338,6 @@ func (sb *SymbolBuilder) SetAddr(arch *sys.Arch, off int64, tgt Sym) int64 {
 }
 
 func (sb *SymbolBuilder) Addstring(str string) int64 {
-	sb.setReachable()
 	if sb.kind == 0 {
 		sb.kind = sym.SNOPTRDATA
 	}
@@ -382,17 +375,14 @@ func (sb *SymbolBuilder) addSymRef(tgt Sym, add int64, typ objabi.RelocType, rsi
 // Add a symbol reference (relocation) with given type, addend, and size
 // (the most generic form).
 func (sb *SymbolBuilder) AddSymRef(arch *sys.Arch, tgt Sym, add int64, typ objabi.RelocType, rsize int) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, add, typ, rsize)
 }
 
 func (sb *SymbolBuilder) AddAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, add, objabi.R_ADDR, arch.PtrSize)
 }
 
 func (sb *SymbolBuilder) AddAddrPlus4(arch *sys.Arch, tgt Sym, add int64) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, add, objabi.R_ADDR, 4)
 }
 
@@ -401,17 +391,14 @@ func (sb *SymbolBuilder) AddAddr(arch *sys.Arch, tgt Sym) int64 {
 }
 
 func (sb *SymbolBuilder) AddPCRelPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, add, objabi.R_PCREL, 4)
 }
 
 func (sb *SymbolBuilder) AddCURelativeAddrPlus(arch *sys.Arch, tgt Sym, add int64) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, add, objabi.R_ADDRCUOFF, arch.PtrSize)
 }
 
 func (sb *SymbolBuilder) AddSize(arch *sys.Arch, tgt Sym) int64 {
-	sb.setReachable()
 	return sb.addSymRef(tgt, 0, objabi.R_SIZE, arch.PtrSize)
 }
 

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

@@ -749,7 +749,6 @@ func gentramp(ctxt *ld.Link, ldr *loader.Loader, tramp *loader.SymbolBuilder, ta
 
 		toctramp := ldr.CreateSymForUpdate("TOC."+ldr.SymName(tramp.Sym()), 0)
 		toctramp.SetType(sym.SXCOFFTOC)
-		toctramp.SetReachable(true)
 		toctramp.AddAddrPlus(ctxt.Arch, target, offset)
 
 		r := loader.Reloc{
@@ -1027,8 +1026,7 @@ func addpltsym(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym) {
 
 // Generate the glink resolver stub if necessary and return the .glink section
 func ensureglinkresolver(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuilder {
-	gs := ldr.LookupOrCreateSym(".glink", 0)
+	glink := ldr.CreateSymForUpdate(".glink", 0)
-	glink := ldr.MakeSymbolUpdater(gs)
 	if glink.Size() != 0 {
 		return glink
 	}