cmd/internal/goobj, cmd/link: remove funcdataoff

FUNCDATA is always a symbol reference with 0 offset. Assert the
offset is 0 and remove funcdataoff.

Change-Id: I326815365c9db5aeef6b869df5d78a9957bc16a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/352894
Trust: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>

6 files changed, 62 insertions, 102 deletions

diff --git a/src/cmd/internal/goobj/funcinfo.go b/src/cmd/internal/goobj/funcinfo.go
index 6e7970fb74..59cb957fa7 100644
--- a/src/cmd/internal/goobj/funcinfo.go
+++ b/src/cmd/internal/goobj/funcinfo.go
@@ -21,11 +21,8 @@ type FuncInfo struct {
 	Locals   uint32
 	FuncID   objabi.FuncID
 	FuncFlag objabi.FuncFlag
-
-	Funcdataoff []uint32
-	File        []CUFileIndex
-
-	InlTree []InlTreeNode
+	File     []CUFileIndex
+	InlTree  []InlTreeNode
 }
 
 func (a *FuncInfo) Write(w *bytes.Buffer) {
@@ -45,10 +42,6 @@ func (a *FuncInfo) Write(w *bytes.Buffer) {
 	writeUint8(0) // pad to uint32 boundary
 	writeUint8(0)
 
-	writeUint32(uint32(len(a.Funcdataoff)))
-	for _, x := range a.Funcdataoff {
-		writeUint32(x)
-	}
 	writeUint32(uint32(len(a.File)))
 	for _, f := range a.File {
 		writeUint32(uint32(f))
@@ -65,25 +58,19 @@ func (a *FuncInfo) Write(w *bytes.Buffer) {
 // corresponding "off" field stores the byte offset of the start of
 // the items in question.
 type FuncInfoLengths struct {
-	NumFuncdataoff uint32
-	FuncdataoffOff uint32
-	NumFile        uint32
-	FileOff        uint32
-	NumInlTree     uint32
-	InlTreeOff     uint32
-	Initialized    bool
+	NumFile     uint32
+	FileOff     uint32
+	NumInlTree  uint32
+	InlTreeOff  uint32
+	Initialized bool
 }
 
 func (*FuncInfo) ReadFuncInfoLengths(b []byte) FuncInfoLengths {
 	var result FuncInfoLengths
 
-	// Offset to the number of funcdataoff values. This value is determined by counting
+	// Offset to the number of the file table. This value is determined by counting
 	// the number of bytes until we write funcdataoff to the file.
-	const numfuncdataoffOff = 12
-	result.NumFuncdataoff = binary.LittleEndian.Uint32(b[numfuncdataoffOff:])
-	result.FuncdataoffOff = numfuncdataoffOff + 4
-
-	numfileOff := result.FuncdataoffOff + 4*result.NumFuncdataoff
+	const numfileOff = 12
 	result.NumFile = binary.LittleEndian.Uint32(b[numfileOff:])
 	result.FileOff = numfileOff + 4
 
@@ -104,10 +91,6 @@ func (*FuncInfo) ReadFuncID(b []byte) objabi.FuncID { return objabi.FuncID(b[8])
 
 func (*FuncInfo) ReadFuncFlag(b []byte) objabi.FuncFlag { return objabi.FuncFlag(b[9]) }
 
-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) CUFileIndex {
 	return CUFileIndex(binary.LittleEndian.Uint32(b[filesoff+4*k:]))
 }
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 82ff5994d1..abb37416cc 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -830,15 +830,14 @@ func (*LSym) CanBeAnSSAAux() {}
 
 type Pcln struct {
 	// Aux symbols for pcln
-	Pcsp        *LSym
-	Pcfile      *LSym
-	Pcline      *LSym
-	Pcinline    *LSym
-	Pcdata      []*LSym
-	Funcdata    []*LSym
-	Funcdataoff []int64
-	UsedFiles   map[goobj.CUFileIndex]struct{} // file indices used while generating pcfile
-	InlTree     InlTree                        // per-function inlining tree extracted from the global tree
+	Pcsp      *LSym
+	Pcfile    *LSym
+	Pcline    *LSym
+	Pcinline  *LSym
+	Pcdata    []*LSym
+	Funcdata  []*LSym
+	UsedFiles map[goobj.CUFileIndex]struct{} // file indices used while generating pcfile
+	InlTree   InlTree                        // per-function inlining tree extracted from the global tree
 }
 
 type Reloc struct {
diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index bed32198d7..3d8d69f069 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -671,10 +671,6 @@ func genFuncInfoSyms(ctxt *Link) {
 			FuncFlag: fn.FuncFlag,
 		}
 		pc := &fn.Pcln
-		o.Funcdataoff = make([]uint32, len(pc.Funcdataoff))
-		for i, x := range pc.Funcdataoff {
-			o.Funcdataoff[i] = uint32(x)
-		}
 		i := 0
 		o.File = make([]goobj.CUFileIndex, len(pc.UsedFiles))
 		for f := range pc.UsedFiles {
diff --git a/src/cmd/internal/obj/pcln.go b/src/cmd/internal/obj/pcln.go
index 42c4a2a9d9..49b425b124 100644
--- a/src/cmd/internal/obj/pcln.go
+++ b/src/cmd/internal/obj/pcln.go
@@ -8,6 +8,7 @@ import (
 	"cmd/internal/goobj"
 	"cmd/internal/objabi"
 	"encoding/binary"
+	"fmt"
 	"log"
 )
 
@@ -280,8 +281,6 @@ func linkpcln(ctxt *Link, cursym *LSym) {
 
 	pcln.Pcdata = make([]*LSym, npcdata)
 	pcln.Funcdata = make([]*LSym, nfuncdata)
-	pcln.Funcdataoff = make([]int64, nfuncdata)
-	pcln.Funcdataoff = pcln.Funcdataoff[:nfuncdata]
 
 	pcln.Pcsp = funcpctab(ctxt, cursym, "pctospadj", pctospadj, nil)
 	pcln.Pcfile = funcpctab(ctxt, cursym, "pctofile", pctofileline, pcln)
@@ -351,12 +350,10 @@ func linkpcln(ctxt *Link, cursym *LSym) {
 				continue
 			}
 			i := int(p.From.Offset)
-			pcln.Funcdataoff[i] = p.To.Offset
-			if p.To.Type != TYPE_CONST {
-				// TODO: Dedup.
-				//funcdata_bytes += p->to.sym->size;
-				pcln.Funcdata[i] = p.To.Sym
+			if p.To.Type != TYPE_MEM || p.To.Offset != 0 {
+				panic(fmt.Sprintf("bad funcdata: %v", p))
 			}
+			pcln.Funcdata[i] = p.To.Sym
 		}
 	}
 }
diff --git a/src/cmd/link/internal/ld/pcln.go b/src/cmd/link/internal/ld/pcln.go
index c8cd7bf09e..f319c10b5b 100644
--- a/src/cmd/link/internal/ld/pcln.go
+++ b/src/cmd/link/internal/ld/pcln.go
@@ -623,33 +623,24 @@ func (state *pclntab) generateFunctab(ctxt *Link, funcs []loader.Sym, inlSyms ma
 }
 
 // funcData returns the funcdata and offsets for the FuncInfo.
-// The funcdata and offsets are written into runtime.functab after each func
+// The funcdata are written into runtime.functab after each func
 // object. This is a helper function to make querying the FuncInfo object
 // cleaner.
 //
-// Note, the majority of fdOffsets are 0, meaning there is no offset between
-// the compiler's generated symbol, and what the runtime needs. They are
-// plumbed through for no loss of generality.
-//
 // NB: Preload must be called on the FuncInfo before calling.
-// NB: fdSyms and fdOffs are used as scratch space.
-func funcData(fi loader.FuncInfo, inlSym loader.Sym, fdSyms []loader.Sym, fdOffs []int64) ([]loader.Sym, []int64) {
-	fdSyms, fdOffs = fdSyms[:0], fdOffs[:0]
+// NB: fdSyms is used as scratch space.
+func funcData(ldr *loader.Loader, s loader.Sym, fi loader.FuncInfo, inlSym loader.Sym, fdSyms []loader.Sym) []loader.Sym {
+	fdSyms = fdSyms[:0]
 	if fi.Valid() {
-		numOffsets := int(fi.NumFuncdataoff())
-		for i := 0; i < numOffsets; i++ {
-			fdOffs = append(fdOffs, fi.Funcdataoff(i))
-		}
-		fdSyms = fi.Funcdata(fdSyms)
+		fdSyms = ldr.Funcdata(s, fdSyms)
 		if fi.NumInlTree() > 0 {
 			if len(fdSyms) < objabi.FUNCDATA_InlTree+1 {
 				fdSyms = append(fdSyms, make([]loader.Sym, objabi.FUNCDATA_InlTree+1-len(fdSyms))...)
-				fdOffs = append(fdOffs, make([]int64, objabi.FUNCDATA_InlTree+1-len(fdOffs))...)
 			}
 			fdSyms[objabi.FUNCDATA_InlTree] = inlSym
 		}
 	}
-	return fdSyms, fdOffs
+	return fdSyms
 }
 
 // calculateFunctabSize calculates the size of the pclntab, and the offsets in
@@ -673,7 +664,7 @@ func (state pclntab) calculateFunctabSize(ctxt *Link, funcs []loader.Sym) (int64
 		size += int64(state.funcSize)
 		if fi.Valid() {
 			fi.Preload()
-			numFuncData := int(fi.NumFuncdataoff())
+			numFuncData := ldr.NumFuncdata(s)
 			if fi.NumInlTree() > 0 {
 				if numFuncData < objabi.FUNCDATA_InlTree+1 {
 					numFuncData = objabi.FUNCDATA_InlTree + 1
@@ -738,7 +729,7 @@ func writePCToFunc(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, sta
 // generateFunctab.
 func (state *pclntab) writeFuncData(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSyms map[loader.Sym]loader.Sym, startLocations []uint32, setAddr pclnSetAddr, setUint pclnSetUint) {
 	ldr := ctxt.loader
-	funcdata, funcdataoff := []loader.Sym{}, []int64{}
+	funcdata := []loader.Sym{}
 	for i, s := range funcs {
 		fi := ldr.FuncInfo(s)
 		if !fi.Valid() {
@@ -748,18 +739,18 @@ func (state *pclntab) writeFuncData(ctxt *Link, sb *loader.SymbolBuilder, funcs
 
 		// funcdata, must be pointer-aligned and we're only int32-aligned.
 		// Missing funcdata will be 0 (nil pointer).
-		funcdata, funcdataoff := funcData(fi, inlSyms[s], funcdata, funcdataoff)
+		funcdata = funcData(ldr, s, fi, inlSyms[s], funcdata)
 		if len(funcdata) > 0 {
 			off := int64(startLocations[i] + state.funcSize + numPCData(ldr, s, fi)*4)
 			off = Rnd(off, int64(ctxt.Arch.PtrSize))
 			for j := range funcdata {
 				dataoff := off + int64(ctxt.Arch.PtrSize*j)
 				if funcdata[j] == 0 {
-					setUint(sb, ctxt.Arch, dataoff, uint64(funcdataoff[j]))
+					setUint(sb, ctxt.Arch, dataoff, 0)
 					continue
 				}
 				// TODO: Does this need deduping?
-				setAddr(sb, ctxt.Arch, dataoff, funcdata[j], funcdataoff[j])
+				setAddr(sb, ctxt.Arch, dataoff, funcdata[j], 0)
 			}
 		}
 	}
@@ -769,7 +760,7 @@ func (state *pclntab) writeFuncData(ctxt *Link, sb *loader.SymbolBuilder, funcs
 func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSyms map[loader.Sym]loader.Sym, startLocations, cuOffsets []uint32, nameOffsets map[loader.Sym]uint32) {
 	ldr := ctxt.loader
 	deferReturnSym := ldr.Lookup("runtime.deferreturn", abiInternalVer)
-	funcdata, funcdataoff := []loader.Sym{}, []int64{}
+	funcdata := []loader.Sym{}
 	var pcsp, pcfile, pcline, pcinline loader.Sym
 	var pcdata []loader.Sym
 
@@ -839,7 +830,7 @@ func writeFuncs(ctxt *Link, sb *loader.SymbolBuilder, funcs []loader.Sym, inlSym
 		off += 1 // pad
 
 		// nfuncdata must be the final entry.
-		funcdata, funcdataoff = funcData(fi, 0, funcdata, funcdataoff)
+		funcdata = funcData(ldr, s, fi, 0, funcdata)
 		off = uint32(sb.SetUint8(ctxt.Arch, int64(off), uint8(len(funcdata))))
 
 		// Output the pcdata.
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index ec145da26d..9b7888e940 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -1930,12 +1930,38 @@ func (l *Loader) NumPcdata(i Sym) int {
 	return n
 }
 
+// Returns all funcdata symbols of symbol i.
+// tmp is a scratch space.
+func (l *Loader) Funcdata(i Sym, tmp []Sym) []Sym {
+	fd := tmp[:0]
+	r, auxs := l.auxs(i)
+	for j := range auxs {
+		a := &auxs[j]
+		if a.Type() == goobj.AuxFuncdata {
+			fd = append(fd, l.resolve(r, a.Sym()))
+		}
+	}
+	return fd
+}
+
+// Returns the number of funcdata for symbol i.
+func (l *Loader) NumFuncdata(i Sym) int {
+	n := 0
+	_, auxs := l.auxs(i)
+	for j := range auxs {
+		a := &auxs[j]
+		if a.Type() == goobj.AuxFuncdata {
+			n++
+		}
+	}
+	return n
+}
+
 // FuncInfo provides hooks to access goobj.FuncInfo in the objects.
 type FuncInfo struct {
 	l       *Loader
 	r       *oReader
 	data    []byte
-	auxs    []goobj.Aux
 	lengths goobj.FuncInfoLengths
 }
 
@@ -1963,38 +1989,6 @@ func (fi *FuncInfo) Preload() {
 	fi.lengths = (*goobj.FuncInfo)(nil).ReadFuncInfoLengths(fi.data)
 }
 
-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 (*goobj.FuncInfo)(nil).ReadFuncdataoff(fi.data, fi.lengths.FuncdataoffOff, uint32(k))
-}
-
-func (fi *FuncInfo) Funcdata(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]
-	}
-	for j := range fi.auxs {
-		a := &fi.auxs[j]
-		if a.Type() == goobj.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")
@@ -2051,7 +2045,7 @@ func (l *Loader) FuncInfo(i Sym) FuncInfo {
 		a := &auxs[j]
 		if a.Type() == goobj.AuxFuncInfo {
 			b := r.Data(a.Sym().SymIdx)
-			return FuncInfo{l, r, b, auxs, goobj.FuncInfoLengths{}}
+			return FuncInfo{l, r, b, goobj.FuncInfoLengths{}}
 		}
 	}
 	return FuncInfo{}