cmd/internal/obj: index pcdata symbols in NumberSyms

When writing an object file, most symbols are indexed in
NumberSyms. Currently, pcdata symbols are indexed late and
separately. This is not really necessary, as pcdata symbols
already exist at the time of NumberSyms. Just do it there.

As pcdata symbols are laid out in the pclntab in a special way at
link time, distinguish them from other symbols in the content
hash. (In the old code this was partly achieved by indexing them
late.)

Change-Id: Ie9e721382b0af2cfb39350d031e2e66d79095a3c
Reviewed-on: https://go-review.googlesource.com/c/go/+/352611
Trust: Cherry Mui <cherryyz@google.com>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/internal/obj/link.go

@@ -700,6 +700,9 @@ const (
 	// convert between ABI0 and ABIInternal calling conventions.
 	AttrABIWrapper
 
+	// IsPcdata indicates this is a pcdata symbol.
+	AttrPcdata
+
 	// attrABIBase is the value at which the ABI is encoded in
 	// Attribute. This must be last; all bits after this are
 	// assumed to be an ABI value.
@@ -727,6 +730,7 @@ func (a *Attribute) Indexed() bool            { return a.load()&AttrIndexed != 0
 func (a *Attribute) UsedInIface() bool        { return a.load()&AttrUsedInIface != 0 }
 func (a *Attribute) ContentAddressable() bool { return a.load()&AttrContentAddressable != 0 }
 func (a *Attribute) ABIWrapper() bool         { return a.load()&AttrABIWrapper != 0 }
+func (a *Attribute) IsPcdata() bool           { return a.load()&AttrPcdata != 0 }
 
 func (a *Attribute) Set(flag Attribute, value bool) {
 	for {

src/cmd/internal/obj/objfile.go

@@ -391,7 +391,9 @@ func (w *writer) Hash(s *LSym) {
 // TODO: instead of duplicating them, have the compiler decide where symbols go.
 func contentHashSection(s *LSym) byte {
 	name := s.Name
-	if strings.HasPrefix(name, "type.") {
+	if s.IsPcdata() {
+		return 'P'
+	} else if strings.HasPrefix(name, "type.") {
 		return 'T'
 	}
 	return 0
@@ -655,16 +657,6 @@ func nAuxSym(s *LSym) int {
 func genFuncInfoSyms(ctxt *Link) {
 	infosyms := make([]*LSym, 0, len(ctxt.Text))
 	hashedsyms := make([]*LSym, 0, 4*len(ctxt.Text))
-	preparePcSym := func(s *LSym) *LSym {
-		if s == nil {
-			return s
-		}
-		s.PkgIdx = goobj.PkgIdxHashed
-		s.SymIdx = int32(len(hashedsyms) + len(ctxt.hasheddefs))
-		s.Set(AttrIndexed, true)
-		hashedsyms = append(hashedsyms, s)
-		return s
-	}
 	var b bytes.Buffer
 	symidx := int32(len(ctxt.defs))
 	for _, s := range ctxt.Text {
@@ -679,13 +671,13 @@ func genFuncInfoSyms(ctxt *Link) {
 			FuncFlag: fn.FuncFlag,
 		}
 		pc := &fn.Pcln
-		o.Pcsp = makeSymRef(preparePcSym(pc.Pcsp))
+		o.Pcsp = makeSymRef(pc.Pcsp)
-		o.Pcfile = makeSymRef(preparePcSym(pc.Pcfile))
+		o.Pcfile = makeSymRef(pc.Pcfile)
-		o.Pcline = makeSymRef(preparePcSym(pc.Pcline))
+		o.Pcline = makeSymRef(pc.Pcline)
-		o.Pcinline = makeSymRef(preparePcSym(pc.Pcinline))
+		o.Pcinline = makeSymRef(pc.Pcinline)
 		o.Pcdata = make([]goobj.SymRef, len(pc.Pcdata))
 		for i, pcSym := range pc.Pcdata {
-			o.Pcdata[i] = makeSymRef(preparePcSym(pcSym))
+			o.Pcdata[i] = makeSymRef(pcSym)
 		}
 		o.Funcdataoff = make([]uint32, len(pc.Funcdataoff))
 		for i, x := range pc.Funcdataoff {

src/cmd/internal/obj/pcln.go

@@ -26,7 +26,7 @@ func funcpctab(ctxt *Link, func_ *LSym, desc string, valfunc func(*Link, *LSym,
 	dst := []byte{}
 	sym := &LSym{
 		Type:      objabi.SRODATA,
-		Attribute: AttrContentAddressable,
+		Attribute: AttrContentAddressable | AttrPcdata,
 	}
 
 	if dbg {
@@ -337,7 +337,7 @@ func linkpcln(ctxt *Link, cursym *LSym) {
 			// use an empty symbol.
 			pcln.Pcdata[i] = &LSym{
 				Type:      objabi.SRODATA,
-				Attribute: AttrContentAddressable,
+				Attribute: AttrContentAddressable | AttrPcdata,
 			}
 		} else {
 			pcln.Pcdata[i] = funcpctab(ctxt, cursym, "pctopcdata", pctopcdata, interface{}(uint32(i)))

src/cmd/internal/obj/sym.go

@@ -201,7 +201,7 @@ func (ctxt *Link) NumberSyms() {
 	ctxt.nonpkgdefs = []*LSym{}
 
 	var idx, hashedidx, hashed64idx, nonpkgidx int32
-	ctxt.traverseSyms(traverseDefs, func(s *LSym) {
+	ctxt.traverseSyms(traverseDefs|traversePcdata, func(s *LSym) {
 		// if Pkgpath is unknown, cannot hash symbols with relocations, as it
 		// may reference named symbols whose names are not fully expanded.
 		if s.ContentAddressable() && (ctxt.Pkgpath != "" || len(s.R) == 0) {
@@ -324,12 +324,18 @@ const (
 	traverseDefs traverseFlag = 1 << iota
 	traverseRefs
 	traverseAux
+	traversePcdata
 
-	traverseAll = traverseDefs | traverseRefs | traverseAux
+	traverseAll = traverseDefs | traverseRefs | traverseAux | traversePcdata
 )
 
 // Traverse symbols based on flag, call fn for each symbol.
 func (ctxt *Link) traverseSyms(flag traverseFlag, fn func(*LSym)) {
+	fnNoNil := func(s *LSym) {
+		if s != nil {
+			fn(s)
+		}
+	}
 	lists := [][]*LSym{ctxt.Text, ctxt.Data}
 	for _, list := range lists {
 		for _, s := range list {
@@ -338,15 +344,11 @@ func (ctxt *Link) traverseSyms(flag traverseFlag, fn func(*LSym)) {
 			}
 			if flag&traverseRefs != 0 {
 				for _, r := range s.R {
-					if r.Sym != nil {
+					fnNoNil(r.Sym)
-						fn(r.Sym)
-					}
 				}
 			}
 			if flag&traverseAux != 0 {
-				if s.Gotype != nil {
+				fnNoNil(s.Gotype)
-					fn(s.Gotype)
-				}
 				if s.Type == objabi.STEXT {
 					f := func(parent *LSym, aux *LSym) {
 						fn(aux)
@@ -354,6 +356,16 @@ func (ctxt *Link) traverseSyms(flag traverseFlag, fn func(*LSym)) {
 					ctxt.traverseFuncAux(flag, s, f)
 				}
 			}
+			if flag&traversePcdata != 0 && s.Type == objabi.STEXT {
+				fi := s.Func().Pcln
+				fnNoNil(fi.Pcsp)
+				fnNoNil(fi.Pcfile)
+				fnNoNil(fi.Pcline)
+				fnNoNil(fi.Pcinline)
+				for _, d := range fi.Pcdata {
+					fnNoNil(d)
+				}
+			}
 		}
 	}
 }