[dev.link] use per package filenames to build pclntab

In order to prevent renumbering of filenames in pclntab generation, use
the per-package file list (previously only used for DWARF generation) as
file-indices. This is the largest step to eliminate renumbering of
filenames in pclntab.

Note, this is probably not the final state of the file table within the
object file. In this form, the linker loads all filenames for all
objects. I'll move to storing the filenames as regular string
symbols,and defaulting all string symbols to using the larger hash value
to make generation of pcln simplest, and most memory friendly.

Change-Id: I23daafa3f4b4535076e23100200ae0e7163aafe0
Reviewed-on: https://go-review.googlesource.com/c/go/+/245485
Run-TryBot: Jeremy Faller <jeremy@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

src/cmd/internal/goobj/read.go

@@ -107,7 +107,7 @@ type Func struct {
 	PCInline Data                            // PC → inline tree index map
 	PCData   []Data                          // PC → runtime support data map
 	FuncData []FuncData                      // non-PC-specific runtime support data
-	File     []string   // paths indexed by PCFile
+	File     map[goobj2.CUFileIndex]struct{} // set of files used in this function
 	InlTree  []InlinedCall
 }
 
@@ -123,7 +123,7 @@ type FuncData struct {
 // See cmd/internal/obj.InlTree for details.
 type InlinedCall struct {
 	Parent   int64
-	File     string
+	File     goobj2.CUFileIndex
 	Line     int64
 	Func     SymID
 	ParentPC int64
@@ -138,7 +138,7 @@ type Package struct {
 	MaxVersion int64           // maximum Version in any SymID in Syms
 	Arch       string          // architecture
 	Native     []*NativeReader // native object data (e.g. ELF)
-	DWARFFileList []string        // List of files for the DWARF .debug_lines section
+	FileList   []string        // List of files for this package.
 }
 
 type NativeReader struct {

src/cmd/internal/goobj/readnew.go

@@ -75,6 +75,12 @@ func (r *objReader) readNew() {
 
 	// Read things for the current goobj API for now.
 
+	// File names
+	r.p.FileList = make([]string, rr.NFile())
+	for i := range r.p.FileList {
+		r.p.FileList[i] = rr.File(i)
+	}
+
 	// Symbols
 	pcdataBase := start + rr.PcdataBase()
 	ndef := uint32(rr.NSym() + rr.NHashed64def() + rr.NHasheddef() + rr.NNonpkgdef())
@@ -166,7 +172,7 @@ func (r *objReader) readNew() {
 			PCInline: Data{int64(pcdataBase + info.Pcinline), int64(info.Pcdata[0] - info.Pcinline)},
 			PCData:   make([]Data, len(info.Pcdata)-1), // -1 as we appended one above
 			FuncData: make([]FuncData, len(info.Funcdataoff)),
-			File:     make([]string, len(info.File)),
+			File:     make(map[goobj2.CUFileIndex]struct{}, len(info.File)),
 			InlTree:  make([]InlinedCall, len(info.InlTree)),
 		}
 		sym.Func = f
@@ -177,15 +183,14 @@ func (r *objReader) readNew() {
 			symID := resolveSymRef(funcdata[k])
 			f.FuncData[k] = FuncData{symID, int64(info.Funcdataoff[k])}
 		}
-		for k := range f.File {
+		for _, k := range info.File {
-			symID := resolveSymRef(info.File[k])
+			f.File[k] = struct{}{}
-			f.File[k] = symID.Name
 		}
 		for k := range f.InlTree {
 			inl := &info.InlTree[k]
 			f.InlTree[k] = InlinedCall{
 				Parent:   int64(inl.Parent),
-				File:     resolveSymRef(inl.File).Name,
+				File:     inl.File,
 				Line:     int64(inl.Line),
 				Func:     resolveSymRef(inl.Func),
 				ParentPC: int64(inl.ParentPC),

src/cmd/internal/goobj2/funcinfo.go

@@ -10,6 +10,10 @@ import (
 	"encoding/binary"
 )
 
+// CUFileIndex is used to index the filenames that are stored in the
+// per-package/per-CU FileList.
+type CUFileIndex uint32
+
 // FuncInfo is serialized as a symbol (aux symbol). The symbol data is
 // the binary encoding of the struct below.
 //
@@ -26,7 +30,7 @@ type FuncInfo struct {
 	Pcdata      []uint32
 	PcdataEnd   uint32
 	Funcdataoff []uint32
-	File        []SymRef // TODO: just use string?
+	File        []CUFileIndex
 
 	InlTree []InlTreeNode
 }
@@ -57,8 +61,7 @@ func (a *FuncInfo) Write(w *bytes.Buffer) {
 	}
 	writeUint32(uint32(len(a.File)))
 	for _, f := range a.File {
-		writeUint32(f.PkgIdx)
+		writeUint32(uint32(f))
-		writeUint32(f.SymIdx)
 	}
 	writeUint32(uint32(len(a.InlTree)))
 	for i := range a.InlTree {
@@ -93,9 +96,9 @@ func (a *FuncInfo) Read(b []byte) {
 		a.Funcdataoff[i] = readUint32()
 	}
 	filelen := readUint32()
-	a.File = make([]SymRef, filelen)
+	a.File = make([]CUFileIndex, filelen)
 	for i := range a.File {
-		a.File[i] = SymRef{readUint32(), readUint32()}
+		a.File[i] = CUFileIndex(readUint32())
 	}
 	inltreelen := readUint32()
 	a.InlTree = make([]InlTreeNode, inltreelen)
@@ -136,8 +139,7 @@ func (*FuncInfo) ReadFuncInfoLengths(b []byte) FuncInfoLengths {
 	result.NumFile = binary.LittleEndian.Uint32(b[numfileOff:])
 	result.FileOff = numfileOff + 4
 
-	const symRefSize = 4 + 4
+	numinltreeOff := result.FileOff + 4*result.NumFile
-	numinltreeOff := result.FileOff + symRefSize*result.NumFile
 	result.NumInlTree = binary.LittleEndian.Uint32(b[numinltreeOff:])
 	result.InlTreeOff = numinltreeOff + 4
 
@@ -181,14 +183,12 @@ func (*FuncInfo) ReadFuncdataoff(b []byte, funcdataofffoff uint32, k uint32) int
 	return int64(binary.LittleEndian.Uint32(b[funcdataofffoff+4*k:]))
 }
 
-func (*FuncInfo) ReadFile(b []byte, filesoff uint32, k uint32) SymRef {
+func (*FuncInfo) ReadFile(b []byte, filesoff uint32, k uint32) CUFileIndex {
-	p := binary.LittleEndian.Uint32(b[filesoff+8*k:])
+	return CUFileIndex(binary.LittleEndian.Uint32(b[filesoff+4*k:]))
-	s := binary.LittleEndian.Uint32(b[filesoff+4+8*k:])
-	return SymRef{p, s}
 }
 
 func (*FuncInfo) ReadInlTree(b []byte, inltreeoff uint32, k uint32) InlTreeNode {
-	const inlTreeNodeSize = 4 * 7
+	const inlTreeNodeSize = 4 * 6
 	var result InlTreeNode
 	result.Read(b[inltreeoff+k*inlTreeNodeSize:])
 	return result
@@ -197,7 +197,7 @@ func (*FuncInfo) ReadInlTree(b []byte, inltreeoff uint32, k uint32) InlTreeNode
 // InlTreeNode is the serialized form of FileInfo.InlTree.
 type InlTreeNode struct {
 	Parent   int32
-	File     SymRef
+	File     CUFileIndex
 	Line     int32
 	Func     SymRef
 	ParentPC int32
@@ -210,8 +210,7 @@ func (inl *InlTreeNode) Write(w *bytes.Buffer) {
 		w.Write(b[:])
 	}
 	writeUint32(uint32(inl.Parent))
-	writeUint32(inl.File.PkgIdx)
+	writeUint32(uint32(inl.File))
-	writeUint32(inl.File.SymIdx)
 	writeUint32(uint32(inl.Line))
 	writeUint32(inl.Func.PkgIdx)
 	writeUint32(inl.Func.SymIdx)
@@ -226,7 +225,7 @@ func (inl *InlTreeNode) Read(b []byte) []byte {
 		return x
 	}
 	inl.Parent = int32(readUint32())
-	inl.File = SymRef{readUint32(), readUint32()}
+	inl.File = CUFileIndex(readUint32())
 	inl.Line = int32(readUint32())
 	inl.Func = SymRef{readUint32(), readUint32()}
 	inl.ParentPC = int32(readUint32())

src/cmd/internal/goobj2/objfile.go

@@ -38,7 +38,7 @@ import (
 //
 //    PkgIndex [...]string // referenced packages by index
 //
-//    DwarfFiles [...]string
+//    Files [...]string
 //
 //    SymbolDefs [...]struct {
 //       Name  string
@@ -177,7 +177,7 @@ const (
 const (
 	BlkAutolib = iota
 	BlkPkgIdx
-	BlkDwarfFile
+	BlkFile
 	BlkSymdef
 	BlkHashed64def
 	BlkHasheddef
@@ -686,12 +686,12 @@ func (r *Reader) Pkg(i int) string {
 	return r.StringRef(off)
 }
 
-func (r *Reader) NDwarfFile() int {
+func (r *Reader) NFile() int {
-	return int(r.h.Offsets[BlkDwarfFile+1]-r.h.Offsets[BlkDwarfFile]) / stringRefSize
+	return int(r.h.Offsets[BlkFile+1]-r.h.Offsets[BlkFile]) / stringRefSize
 }
 
-func (r *Reader) DwarfFile(i int) string {
+func (r *Reader) File(i int) string {
-	off := r.h.Offsets[BlkDwarfFile] + uint32(i)*stringRefSize
+	off := r.h.Offsets[BlkFile] + uint32(i)*stringRefSize
 	return r.StringRef(off)
 }
 

src/cmd/internal/obj/dwarf.go

@@ -32,18 +32,6 @@ const (
 func (ctxt *Link) generateDebugLinesSymbol(s, lines *LSym) {
 	dctxt := dwCtxt{ctxt}
 
-	// The Pcfile table is used to generate the debug_lines section, and the file
-	// indices for that data could differ from the files we write out for the
-	// debug_lines section. Here we generate a LUT between those two indices.
-	fileNums := make(map[int32]int64)
-	for i, filename := range s.Func.Pcln.File {
-		if symbolIndex := ctxt.PosTable.FileIndex(filename); symbolIndex >= 0 {
-			fileNums[int32(i)] = int64(symbolIndex) + 1
-		} else {
-			panic(fmt.Sprintf("First time we've seen filename: %q", filename))
-		}
-	}
-
 	// Emit a LNE_set_address extended opcode, so as to establish the
 	// starting text address of this function.
 	dctxt.AddUint8(lines, 0)

src/cmd/internal/obj/line.go

@@ -22,3 +22,9 @@ func linkgetlineFromPos(ctxt *Link, xpos src.XPos) (f string, l int32) {
 	// TODO(gri) Should this use relative or absolute line number?
 	return pos.SymFilename(), int32(pos.RelLine())
 }
+
+// getFileIndexAndLine returns the file index (local to the CU), and the line number for a position.
+func getFileIndexAndLine(ctxt *Link, xpos src.XPos) (int, int32) {
+	f, l := linkgetlineFromPos(ctxt, xpos)
+	return ctxt.PosTable.FileIndex(f), l
+}

src/cmd/internal/obj/link.go

@@ -631,9 +631,7 @@ type Pcln struct {
 	Pcdata      []Pcdata
 	Funcdata    []*LSym
 	Funcdataoff []int64
-	File        []string
+	UsedFiles   map[goobj2.CUFileIndex]struct{} // file indices used while generating pcfile
-	Lastfile    string
-	Lastindex   int
 	InlTree     InlTree                         // per-function inlining tree extracted from the global tree
 }
 

src/cmd/internal/obj/objfile2.go

@@ -16,6 +16,7 @@ import (
 	"fmt"
 	"io"
 	"path/filepath"
+	"sort"
 	"strings"
 )
 
@@ -69,9 +70,9 @@ func WriteObjFile(ctxt *Link, b *bio.Writer) {
 		w.StringRef(pkg)
 	}
 
-	// DWARF file table
+	// File table (for DWARF and pcln generation).
-	h.Offsets[goobj2.BlkDwarfFile] = w.Offset()
+	h.Offsets[goobj2.BlkFile] = w.Offset()
-	for _, f := range ctxt.PosTable.DebugLinesFileTable() {
+	for _, f := range ctxt.PosTable.FileTable() {
 		w.StringRef(filepath.ToSlash(f))
 	}
 
@@ -248,20 +249,9 @@ func (w *writer) StringTable() {
 		}
 		w.AddString(s.Name)
 	})
-	w.ctxt.traverseSyms(traverseDefs, func(s *LSym) {
+
-		if s.Type != objabi.STEXT {
+	// All filenames are in the postable.
-			return
+	for _, f := range w.ctxt.PosTable.FileTable() {
-		}
-		pc := &s.Func.Pcln
-		for _, f := range pc.File {
-			w.AddString(filepath.ToSlash(f))
-		}
-		for _, call := range pc.InlTree.nodes {
-			f, _ := linkgetlineFromPos(w.ctxt, call.Pos)
-			w.AddString(filepath.ToSlash(f))
-		}
-	})
-	for _, f := range w.ctxt.PosTable.DebugLinesFileTable() {
 		w.AddString(filepath.ToSlash(f))
 	}
 }
@@ -594,18 +584,19 @@ func genFuncInfoSyms(ctxt *Link) {
 		for i, x := range pc.Funcdataoff {
 			o.Funcdataoff[i] = uint32(x)
 		}
-		o.File = make([]goobj2.SymRef, len(pc.File))
+		i := 0
-		for i, f := range pc.File {
+		o.File = make([]goobj2.CUFileIndex, len(pc.UsedFiles))
-			fsym := ctxt.Lookup(f)
+		for f := range pc.UsedFiles {
-			o.File[i] = makeSymRef(fsym)
+			o.File[i] = f
+			i++
 		}
+		sort.Slice(o.File, func(i, j int) bool { return o.File[i] < o.File[j] })
 		o.InlTree = make([]goobj2.InlTreeNode, len(pc.InlTree.nodes))
 		for i, inl := range pc.InlTree.nodes {
-			f, l := linkgetlineFromPos(ctxt, inl.Pos)
+			f, l := getFileIndexAndLine(ctxt, inl.Pos)
-			fsym := ctxt.Lookup(f)
 			o.InlTree[i] = goobj2.InlTreeNode{
 				Parent:   int32(inl.Parent),
-				File:     makeSymRef(fsym),
+				File:     goobj2.CUFileIndex(f),
 				Line:     l,
 				Func:     makeSymRef(inl.Func),
 				ParentPC: inl.ParentPC,

src/cmd/internal/obj/pcln.go

@@ -5,6 +5,7 @@
 package obj
 
 import (
+	"cmd/internal/goobj2"
 	"encoding/binary"
 	"log"
 )
@@ -130,28 +131,13 @@ func pctofileline(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg
 	if p.As == ATEXT || p.As == ANOP || p.Pos.Line() == 0 || phase == 1 {
 		return oldval
 	}
-	f, l := linkgetlineFromPos(ctxt, p.Pos)
+	f, l := getFileIndexAndLine(ctxt, p.Pos)
 	if arg == nil {
 		return l
 	}
 	pcln := arg.(*Pcln)
-
+	pcln.UsedFiles[goobj2.CUFileIndex(f)] = struct{}{}
-	if f == pcln.Lastfile {
+	return int32(f)
-		return int32(pcln.Lastindex)
-	}
-
-	for i, file := range pcln.File {
-		if file == f {
-			pcln.Lastfile = f
-			pcln.Lastindex = i
-			return int32(i)
-		}
-	}
-	i := len(pcln.File)
-	pcln.File = append(pcln.File, f)
-	pcln.Lastfile = f
-	pcln.Lastindex = i
-	return int32(i)
 }
 
 // pcinlineState holds the state used to create a function's inlining
@@ -263,6 +249,7 @@ func pctopcdata(ctxt *Link, sym *LSym, oldval int32, p *Prog, phase int32, arg i
 
 func linkpcln(ctxt *Link, cursym *LSym) {
 	pcln := &cursym.Func.Pcln
+	pcln.UsedFiles = make(map[goobj2.CUFileIndex]struct{})
 
 	npcdata := 0
 	nfuncdata := 0

src/cmd/internal/obj/sym.go

@@ -367,8 +367,9 @@ func (ctxt *Link) traverseFuncAux(flag traverseFlag, fsym *LSym, fn func(parent
 			fn(fsym, d)
 		}
 	}
-	for _, f := range pc.File {
+	files := ctxt.PosTable.FileTable()
-		if filesym := ctxt.Lookup(f); filesym != nil {
+	for f := range pc.UsedFiles {
+		if filesym := ctxt.Lookup(files[f]); filesym != nil {
 			fn(fsym, filesym)
 		}
 	}

src/cmd/internal/objfile/goobj.go

@@ -135,7 +135,7 @@ func (f *goobjFile) PCToLine(pc uint64) (string, int, *gosym.Func) {
 			return "", 0, nil
 		}
 		fileID := int(pcValue(pcfile, pc-uint64(s.Data.Offset), arch))
-		fileName := s.Func.File[fileID]
+		fileName := f.goobj.FileList[fileID]
 		pcline := make([]byte, s.Func.PCLine.Size)
 		_, err = f.f.ReadAt(pcline, s.Func.PCLine.Offset)
 		if err != nil {

src/cmd/internal/src/xpos.go

@@ -163,8 +163,8 @@ func (t *PosTable) FileIndex(filename string) int {
 	return -1
 }
 
-// DebugLinesFiles returns the file table for the debug_lines DWARF section.
+// FileTable returns a slice of all files used to build this package.
-func (t *PosTable) DebugLinesFileTable() []string {
+func (t *PosTable) FileTable() []string {
 	// Create a LUT of the global package level file indices. This table is what
 	// is written in the debug_lines header, the file[N] will be referenced as
 	// N+1 in the debug_lines table.

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

@@ -1224,7 +1224,7 @@ func (d *dwctxt) writelines(unit *sym.CompilationUnit, lineProlog loader.Sym) []
 
 	// Copy over the file table.
 	fileNums := make(map[string]int)
-	for i, name := range unit.DWARFFileTable {
+	for i, name := range unit.FileTable {
 		name := expandFile(name)
 		if len(name) == 0 {
 			// Can't have empty filenames, and having a unique

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

@@ -5,6 +5,7 @@
 package ld
 
 import (
+	"cmd/internal/goobj2"
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
@@ -32,7 +33,7 @@ import (
 type oldPclnState struct {
 	ldr            *loader.Loader
 	deferReturnSym loader.Sym
-	numberedFiles  map[loader.Sym]int64
+	numberedFiles  map[string]int64
 	filepaths      []string
 }
 
@@ -88,7 +89,7 @@ func makeOldPclnState(ctxt *Link) *oldPclnState {
 	state := &oldPclnState{
 		ldr:            ldr,
 		deferReturnSym: drs,
-		numberedFiles:  make(map[loader.Sym]int64),
+		numberedFiles:  make(map[string]int64),
 		// NB: initial entry in filepaths below is to reserve the zero value,
 		// so that when we do a map lookup in numberedFiles fails, it will not
 		// return a value slot in filepaths.
@@ -153,30 +154,37 @@ func ftabaddstring(ftab *loader.SymbolBuilder, s string) int32 {
 }
 
 // numberfile assigns a file number to the file if it hasn't been assigned already.
-func (state *oldPclnState) numberfile(file loader.Sym) int64 {
+// This funciton looks at a CU's file at index [i], and if it's a new filename,
+// stores that filename in the global file table, and adds it to the map lookup
+// for renumbering pcfile.
+func (state *oldPclnState) numberfile(cu *sym.CompilationUnit, i goobj2.CUFileIndex) int64 {
+	file := cu.FileTable[i]
 	if val, ok := state.numberedFiles[file]; ok {
 		return val
 	}
-	sn := state.ldr.SymName(file)
+	path := file
-	path := sn[len(src.FileSymPrefix):]
+	if strings.HasPrefix(path, src.FileSymPrefix) {
+		path = file[len(src.FileSymPrefix):]
+	}
 	val := int64(len(state.filepaths))
 	state.numberedFiles[file] = val
 	state.filepaths = append(state.filepaths, expandGoroot(path))
 	return val
 }
 
-func (state *oldPclnState) fileVal(file loader.Sym) int64 {
+func (state *oldPclnState) fileVal(cu *sym.CompilationUnit, i int32) int64 {
+	file := cu.FileTable[i]
 	if val, ok := state.numberedFiles[file]; ok {
 		return val
 	}
 	panic("should have been numbered first")
 }
 
-func (state *oldPclnState) renumberfiles(ctxt *Link, fi loader.FuncInfo, d *sym.Pcdata) {
+func (state *oldPclnState) renumberfiles(ctxt *Link, cu *sym.CompilationUnit, fi loader.FuncInfo, d *sym.Pcdata) {
 	// Give files numbers.
 	nf := fi.NumFile()
 	for i := uint32(0); i < nf; i++ {
-		state.numberfile(fi.File(int(i)))
+		state.numberfile(cu, fi.File(int(i)))
 	}
 
 	buf := make([]byte, binary.MaxVarintLen32)
@@ -191,10 +199,10 @@ func (state *oldPclnState) renumberfiles(ctxt *Link, fi loader.FuncInfo, d *sym.
 		if oldval == -1 {
 			val = -1
 		} else {
-			if oldval < 0 || oldval >= int32(nf) {
+			if oldval < 0 || oldval >= int32(len(cu.FileTable)) {
 				log.Fatalf("bad pcdata %d", oldval)
 			}
-			val = int32(state.fileVal(fi.File(int(oldval))))
+			val = int32(state.fileVal(cu, oldval))
 		}
 
 		dv := val - newval
@@ -287,7 +295,7 @@ func (state *oldPclnState) computeDeferReturn(target *Target, s loader.Sym) uint
 
 // genInlTreeSym generates the InlTree sym for a function with the
 // specified FuncInfo.
-func (state *oldPclnState) genInlTreeSym(fi loader.FuncInfo, arch *sys.Arch, newState *pclntab) loader.Sym {
+func (state *oldPclnState) genInlTreeSym(cu *sym.CompilationUnit, fi loader.FuncInfo, arch *sys.Arch, newState *pclntab) loader.Sym {
 	ldr := state.ldr
 	its := ldr.CreateExtSym("", 0)
 	inlTreeSym := ldr.MakeSymbolUpdater(its)
@@ -305,7 +313,7 @@ func (state *oldPclnState) genInlTreeSym(fi loader.FuncInfo, arch *sys.Arch, new
 		// might overlap exactly so that only the innermost file
 		// appears in the Pcfile table. In that case, this assigns
 		// the outer file a number.
-		val := state.numberfile(call.File)
+		val := state.numberfile(cu, call.File)
 		nameoff, ok := newState.funcNameOffset[call.Func]
 		if !ok {
 			panic("couldn't find function name offset")
@@ -603,11 +611,12 @@ func (ctxt *Link) pclntab(container loader.Bitmap) *pclntab {
 		deferreturn := oldState.computeDeferReturn(&ctxt.Target, s)
 		off = int32(ftab.SetUint32(ctxt.Arch, int64(off), deferreturn))
 
+		cu := ldr.SymUnit(s)
 		if fi.Valid() {
 			pcsp = sym.Pcdata{P: fi.Pcsp()}
 			pcfile = sym.Pcdata{P: fi.Pcfile()}
 			pcline = sym.Pcdata{P: fi.Pcline()}
-			oldState.renumberfiles(ctxt, fi, &pcfile)
+			oldState.renumberfiles(ctxt, cu, fi, &pcfile)
 			if false {
 				// Sanity check the new numbering
 				it := obj.NewPCIter(uint32(ctxt.Arch.MinLC))
@@ -621,7 +630,7 @@ func (ctxt *Link) pclntab(container loader.Bitmap) *pclntab {
 		}
 
 		if fi.Valid() && fi.NumInlTree() > 0 {
-			its := oldState.genInlTreeSym(fi, ctxt.Arch, state)
+			its := oldState.genInlTreeSym(cu, fi, ctxt.Arch, state)
 			funcdata[objabi.FUNCDATA_InlTree] = its
 			pcdata[objabi.PCDATA_InlTreeIndex] = sym.Pcdata{P: fi.Pcinline()}
 		}

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

@@ -1961,17 +1961,16 @@ func (fi *FuncInfo) NumFile() uint32 {
 	return fi.lengths.NumFile
 }
 
-func (fi *FuncInfo) File(k int) Sym {
+func (fi *FuncInfo) File(k int) goobj2.CUFileIndex {
 	if !fi.lengths.Initialized {
 		panic("need to call Preload first")
 	}
-	sr := (*goobj2.FuncInfo)(nil).ReadFile(fi.data, fi.lengths.FileOff, uint32(k))
+	return (*goobj2.FuncInfo)(nil).ReadFile(fi.data, fi.lengths.FileOff, uint32(k))
-	return fi.l.resolve(fi.r, sr)
 }
 
 type InlTreeNode struct {
 	Parent   int32
-	File     Sym
+	File     goobj2.CUFileIndex
 	Line     int32
 	Func     Sym
 	ParentPC int32
@@ -1991,7 +1990,7 @@ func (fi *FuncInfo) InlTree(k int) InlTreeNode {
 	node := (*goobj2.FuncInfo)(nil).ReadInlTree(fi.data, fi.lengths.InlTreeOff, uint32(k))
 	return InlTreeNode{
 		Parent:   node.Parent,
-		File:     fi.l.resolve(fi.r, node.File),
+		File:     node.File,
 		Line:     node.Line,
 		Func:     fi.l.resolve(fi.r, node.Func),
 		ParentPC: node.ParentPC,
@@ -2060,10 +2059,10 @@ func (l *Loader) Preload(localSymVersion int, f *bio.Reader, lib *sym.Library, u
 	lib.Autolib = append(lib.Autolib, r.Autolib()...)
 
 	// DWARF file table
-	nfile := r.NDwarfFile()
+	nfile := r.NFile()
-	unit.DWARFFileTable = make([]string, nfile)
+	unit.FileTable = make([]string, nfile)
-	for i := range unit.DWARFFileTable {
+	for i := range unit.FileTable {
-		unit.DWARFFileTable[i] = r.DwarfFile(i)
+		unit.FileTable[i] = r.File(i)
 	}
 
 	l.addObj(lib.Pkg, or)

src/cmd/link/internal/sym/compilation_unit.go

@@ -25,7 +25,7 @@ type CompilationUnit struct {
 	PclnIndex int           // Index of this CU in pclntab
 	PCs       []dwarf.Range // PC ranges, relative to Textp[0]
 	DWInfo    *dwarf.DWDie  // CU root DIE
-	DWARFFileTable []string      // The file table used to generate the .debug_lines
+	FileTable []string      // The file table used in this compilation unit.
 
 	Consts    LoaderSym   // Package constants DIEs
 	FuncDIEs  []LoaderSym // Function DIE subtrees