[dev.link] cmd/link/internal/loader: expand methods for FuncInfo

Expand the methods for the FuncInfo helper, to support reading the
contents of an object file FuncInfo aux symbol using the new style
(that is to say, incrementally and without allocating slices to hold
the various bits).

Change-Id: I953d72c4a53f98c840e6b25b08fd33dc4a833dd5
Reviewed-on: https://go-review.googlesource.com/c/go/+/227585
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/internal/goobj2/funcinfo.go

@@ -100,8 +100,49 @@ func (a *FuncInfo) Read(b []byte) {
 	}
 }
 
-// Accessors reading only some fields.
-// TODO: more accessors.
+// FuncInfoLengths is a cache containing a roadmap of offsets and
+// lengths for things within a serialized FuncInfo. Each length field
+// stores the number of items (e.g. files, inltree nodes, etc), and the
+// corresponding "off" field stores the byte offset of the start of
+// the items in question.
+type FuncInfoLengths struct {
+	NumPcdata      uint32
+	PcdataOff      uint32
+	NumFuncdataoff uint32
+	FuncdataoffOff uint32
+	NumFile        uint32
+	FileOff        uint32
+	NumInlTree     uint32
+	InlTreeOff     uint32
+	Initialized    bool
+}
+
+func (*FuncInfo) ReadFuncInfoLengths(b []byte) FuncInfoLengths {
+	var result FuncInfoLengths
+
+	const numpcdataOff = 24
+	result.NumPcdata = binary.LittleEndian.Uint32(b[numpcdataOff:])
+	result.PcdataOff = numpcdataOff + 4
+
+	numfuncdataoffOff := result.PcdataOff + 4*(result.NumPcdata+1)
+	result.NumFuncdataoff = binary.LittleEndian.Uint32(b[numfuncdataoffOff:])
+	result.FuncdataoffOff = numfuncdataoffOff + 4
+
+	numfileOff := result.FuncdataoffOff + 4*result.NumFuncdataoff
+	result.NumFile = binary.LittleEndian.Uint32(b[numfileOff:])
+	result.FileOff = numfileOff + 4
+
+	const symRefSize = 4 + 4
+	numinltreeOff := result.FileOff + symRefSize*result.NumFile
+	result.NumInlTree = binary.LittleEndian.Uint32(b[numinltreeOff:])
+	result.InlTreeOff = numinltreeOff + 4
+
+	result.Initialized = true
+
+	return result
+}
+
+func (*FuncInfo) ReadArgs(b []byte) uint32 { return binary.LittleEndian.Uint32(b) }
 
 func (*FuncInfo) ReadLocals(b []byte) uint32 { return binary.LittleEndian.Uint32(b[4:]) }
 
@@ -110,6 +151,43 @@ func (*FuncInfo) ReadPcsp(b []byte) (uint32, uint32) {
 	return binary.LittleEndian.Uint32(b[8:]), binary.LittleEndian.Uint32(b[12:])
 }
 
+// return start and end offsets.
+func (*FuncInfo) ReadPcfile(b []byte) (uint32, uint32) {
+	return binary.LittleEndian.Uint32(b[12:]), binary.LittleEndian.Uint32(b[16:])
+}
+
+// return start and end offsets.
+func (*FuncInfo) ReadPcline(b []byte) (uint32, uint32) {
+	return binary.LittleEndian.Uint32(b[16:]), binary.LittleEndian.Uint32(b[20:])
+}
+
+// return start and end offsets.
+func (*FuncInfo) ReadPcinline(b []byte, pcdataoffset uint32) (uint32, uint32) {
+	return binary.LittleEndian.Uint32(b[20:]), binary.LittleEndian.Uint32(b[pcdataoffset:])
+}
+
+// return start and end offsets.
+func (*FuncInfo) ReadPcdata(b []byte, pcdataoffset uint32, k uint32) (uint32, uint32) {
+	return binary.LittleEndian.Uint32(b[pcdataoffset+4*k:]), binary.LittleEndian.Uint32(b[pcdataoffset+4+4*k:])
+}
+
+func (*FuncInfo) ReadFuncdataoff(b []byte, funcdataofffoff uint32, k uint32) int64 {
+	return int64(binary.LittleEndian.Uint32(b[funcdataofffoff+4*k:]))
+}
+
+func (*FuncInfo) ReadFile(b []byte, filesoff uint32, k uint32) SymRef {
+	p := binary.LittleEndian.Uint32(b[filesoff+8*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
+	var result InlTreeNode
+	result.Read(b[inltreeoff+k*inlTreeNodeSize:])
+	return result
+}
+
 // InlTreeNode is the serialized form of FileInfo.InlTree.
 type InlTreeNode struct {
 	Parent   int32

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

@@ -1532,10 +1532,15 @@ type FuncInfo struct {
 	l       *Loader
 	r       *oReader
 	data    []byte
+	lengths goobj2.FuncInfoLengths
 }
 
 func (fi *FuncInfo) Valid() bool { return fi.r != nil }
 
+func (fi *FuncInfo) Args() int {
+	return int((*goobj2.FuncInfo)(nil).ReadArgs(fi.data))
+}
+
 func (fi *FuncInfo) Locals() int {
 	return int((*goobj2.FuncInfo)(nil).ReadLocals(fi.data))
 }
@@ -1545,7 +1550,122 @@ func (fi *FuncInfo) Pcsp() []byte {
 	return fi.r.BytesAt(fi.r.PcdataBase()+pcsp, int(end-pcsp))
 }
 
-// TODO: more accessors.
+func (fi *FuncInfo) Pcfile() []byte {
+	pcf, end := (*goobj2.FuncInfo)(nil).ReadPcfile(fi.data)
+	return fi.r.BytesAt(fi.r.PcdataBase()+pcf, int(end-pcf))
+}
+
+func (fi *FuncInfo) Pcline() []byte {
+	pcln, end := (*goobj2.FuncInfo)(nil).ReadPcline(fi.data)
+	return fi.r.BytesAt(fi.r.PcdataBase()+pcln, int(end-pcln))
+}
+
+// Preload has to be called prior to invoking the various methods
+// below related to pcdata, funcdataoff, files, and inltree nodes.
+func (fi *FuncInfo) Preload() {
+	fi.lengths = (*goobj2.FuncInfo)(nil).ReadFuncInfoLengths(fi.data)
+}
+
+func (fi *FuncInfo) Pcinline() []byte {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	pcinl, end := (*goobj2.FuncInfo)(nil).ReadPcinline(fi.data, fi.lengths.PcdataOff)
+	return fi.r.BytesAt(fi.r.PcdataBase()+pcinl, int(end-pcinl))
+}
+
+func (fi *FuncInfo) NumPcdata() uint32 {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	return fi.lengths.NumPcdata
+}
+
+func (fi *FuncInfo) Pcdata(k int) []byte {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	pcdat, end := (*goobj2.FuncInfo)(nil).ReadPcdata(fi.data, fi.lengths.PcdataOff, uint32(k))
+	return fi.r.BytesAt(fi.r.PcdataBase()+pcdat, int(end-pcdat))
+}
+
+func (fi *FuncInfo) NumFuncdataoff() uint32 {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	return fi.lengths.NumFuncdataoff
+}
+
+func (fi *FuncInfo) Funcdataoff(k int) int64 {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	return (*goobj2.FuncInfo)(nil).ReadFuncdataoff(fi.data, fi.lengths.FuncdataoffOff, uint32(k))
+}
+
+func (fi *FuncInfo) Funcdata(fnsym Sym, syms []Sym) []Sym {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	if int(fi.lengths.NumFuncdataoff) > cap(syms) {
+		syms = make([]Sym, 0, fi.lengths.NumFuncdataoff)
+	} else {
+		syms = syms[:0]
+	}
+	r, li := fi.l.toLocal(fnsym)
+	auxs := r.Auxs2(li)
+	for j := range auxs {
+		a := &auxs[j]
+		if a.Type() == goobj2.AuxFuncdata {
+			syms = append(syms, fi.l.resolve(fi.r, a.Sym()))
+		}
+	}
+	return syms
+}
+
+func (fi *FuncInfo) NumFile() uint32 {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	return fi.lengths.NumFile
+}
+
+func (fi *FuncInfo) File(k int) Sym {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	sr := (*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
+	Line     int32
+	Func     Sym
+	ParentPC int32
+}
+
+func (fi *FuncInfo) NumInlTree() uint32 {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	return fi.lengths.NumInlTree
+}
+
+func (fi *FuncInfo) InlTree(k int) InlTreeNode {
+	if !fi.lengths.Initialized {
+		panic("need to call Preload first")
+	}
+	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),
+		Line:     node.Line,
+		Func:     fi.l.resolve(fi.r, node.Func),
+		ParentPC: node.ParentPC,
+	}
+}
 
 func (l *Loader) FuncInfo(i Sym) FuncInfo {
 	var r *oReader
@@ -1566,7 +1686,7 @@ func (l *Loader) FuncInfo(i Sym) FuncInfo {
 		a := &auxs[j]
 		if a.Type() == goobj2.AuxFuncInfo {
 			b := r.Data(int(a.Sym().SymIdx))
-			return FuncInfo{l, r, b}
+			return FuncInfo{l, r, b, goobj2.FuncInfoLengths{}}
 		}
 	}
 	return FuncInfo{}