[dev.link] cmd/link/internal/objfile: update deadcode2 to use new reloc hooks

Update the new deadcode pass to use the revised loader interface
for querying relocations. Remove some of the previous loader relocation
methods, since they are no longer used.

Change-Id: I08cec4c05793a17698b2674068f64837a5bf4477
Reviewed-on: https://go-review.googlesource.com/c/go/+/200718Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/link/internal/ld/deadcode2.go

@@ -64,9 +64,9 @@ func (d *deadcodePass2) init() {
 			// but we do keep the symbols it refers to.
 			exportsIdx := d.loader.Lookup("go.plugin.exports", 0)
 			if exportsIdx != 0 {
-				nreloc := d.loader.NReloc(exportsIdx)
-				for i := 0; i < nreloc; i++ {
-					d.mark(d.loader.RelocSym(exportsIdx, i))
+				relocs := d.loader.Relocs(exportsIdx)
+				for i := 0; i < relocs.Count; i++ {
+					d.mark(relocs.At(i).Sym)
 				}
 			}
 		}
@@ -86,17 +86,17 @@ func (d *deadcodePass2) init() {
 func (d *deadcodePass2) flood() {
 	for !d.wq.empty() {
 		symIdx := d.wq.pop()
-		nreloc := d.loader.NReloc(symIdx)
-		for i := 0; i < nreloc; i++ {
-			t := d.loader.RelocType(symIdx, i)
-			if t == objabi.R_WEAKADDROFF {
+		relocs := d.loader.Relocs(symIdx)
+		for i := 0; i < relocs.Count; i++ {
+			r := relocs.At(i)
+			if r.Type == objabi.R_WEAKADDROFF {
 				continue
 			}
-			if t == objabi.R_METHODOFF {
+			if r.Type == objabi.R_METHODOFF {
 				// TODO: we should do something about it
 				// For now, all the methods are considered live
 			}
-			d.mark(d.loader.RelocSym(symIdx, i))
+			d.mark(r.Sym)
 		}
 		naux := d.loader.NAux(symIdx)
 		for i := 0; i < naux; i++ {
@@ -125,7 +125,8 @@ func deadcode2(ctxt *Link) {
 		for i := 1; i < n; i++ {
 			s := objfile.Sym(i)
 			if strings.HasPrefix(loader.RawSymName(s), "go.itablink.") {
-				if d.loader.NReloc(s) > 0 && loader.Reachable.Has(loader.RelocSym(s, 0)) {
+				relocs := loader.Relocs(s)
+				if relocs.Count > 0 && loader.Reachable.Has(relocs.At(0).Sym) {
 					loader.Reachable.Set(s)
 				}
 			}

src/cmd/link/internal/objfile/objfile2.go

@@ -266,33 +266,6 @@ func (l *Loader) SymType(i Sym) sym.SymKind {
 	return sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)]
 }
 
-// Returns the number of relocations given a global index.
-func (l *Loader) NReloc(i Sym) int {
-	r, li := l.ToLocal(i)
-	if r == nil {
-		return 0
-	}
-	return r.NReloc(li)
-}
-
-// Returns the referred symbol of the j-th relocation of the i-th
-// symbol.
-func (l *Loader) RelocSym(i Sym, j int) Sym {
-	r, li := l.ToLocal(i)
-	rel := goobj2.Reloc{}
-	rel.Read(r.Reader, r.RelocOff(li, j))
-	return l.Resolve(r, rel.Sym)
-}
-
-// Returns the relocation type of the j-th relocation of the i-th
-// symbol.
-func (l *Loader) RelocType(i Sym, j int) objabi.RelocType {
-	r, li := l.ToLocal(i)
-	rel := goobj2.Reloc{}
-	rel.Read(r.Reader, r.RelocOff(li, j))
-	return objabi.RelocType(rel.Type)
-}
-
 // Returns the number of aux symbols given a global index.
 func (l *Loader) NAux(i Sym) int {
 	r, li := l.ToLocal(i)