[dev.link] cmd/link: experiment new reloc accessors in deadcode pass
There is a small speedup:
(linking cmd/compile)
name old time/op new time/op delta
Deadcode 57.1ms ± 1% 53.5ms ± 1% -6.44% (p=0.008 n=5+5)
With this, we don't need a slice to read the relocations, reduce
some allocations.
name old alloc/op new alloc/op delta
Deadcode 4.16MB ± 0% 3.84MB ± 0% -7.85% (p=0.008 n=5+5)
Change-Id: Icd41c05682ba3f293a8cb9d2fe818e39d7276e5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/222244
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/src/cmd/internal/goobj2/objfile.go b/src/cmd/internal/goobj2/objfile.go
index 6d9b0f9..d5a9b4a 100644
--- a/src/cmd/internal/goobj2/objfile.go
+++ b/src/cmd/internal/goobj2/objfile.go
@@ -321,6 +321,15 @@
return SymRef{binary.LittleEndian.Uint32(r[14:]), binary.LittleEndian.Uint32(r[18:])}
}
+func (r *Reloc2) Set(off int32, size uint8, typ uint8, add int64, sym SymRef) {
+ binary.LittleEndian.PutUint32(r[:], uint32(off))
+ r[4] = size
+ r[5] = typ
+ binary.LittleEndian.PutUint64(r[6:], uint64(add))
+ binary.LittleEndian.PutUint32(r[14:], sym.PkgIdx)
+ binary.LittleEndian.PutUint32(r[18:], sym.SymIdx)
+}
+
// Aux symbol info.
type Aux struct {
Type uint8
diff --git a/src/cmd/link/internal/ld/deadcode2.go b/src/cmd/link/internal/ld/deadcode2.go
index 4733f47..a7a41e3 100644
--- a/src/cmd/link/internal/ld/deadcode2.go
+++ b/src/cmd/link/internal/ld/deadcode2.go
@@ -37,7 +37,6 @@
ctxt *Link
ldr *loader.Loader
wq workQueue
- rtmp []loader.Reloc
ifaceMethod map[methodsig]bool // methods declared in reached interfaces
markableMethods []methodref2 // methods of reached types
@@ -86,9 +85,9 @@
// but we do keep the symbols it refers to.
exportsIdx := d.ldr.Lookup("go.plugin.exports", 0)
if exportsIdx != 0 {
- d.ReadRelocSyms(exportsIdx)
- for i := 0; i < len(d.rtmp); i++ {
- d.mark(d.rtmp[i].Sym, 0)
+ relocs := d.ldr.Relocs(exportsIdx)
+ for i := 0; i < relocs.Count; i++ {
+ d.mark(relocs.At2(i).Sym(), 0)
}
}
}
@@ -119,7 +118,6 @@
}
func (d *deadcodePass2) flood() {
- symRelocs := []loader.Reloc{}
auxSyms := []loader.Sym{}
for !d.wq.empty() {
symIdx := d.wq.pop()
@@ -128,22 +126,11 @@
isgotype := d.ldr.IsGoType(symIdx)
relocs := d.ldr.Relocs(symIdx)
- // For non-type symbols, we only need the target and the reloc
- // type, so don't read other fields.
- // For type symbols we may need all fields for interface
- // satisfaction check.
- // TODO: we don't even need the reloc type for non-type non-dwarf
- // symbols.
- if isgotype {
- symRelocs = relocs.ReadAll(symRelocs)
- } else {
- symRelocs = relocs.ReadSyms(symRelocs)
- }
if isgotype {
p := d.ldr.Data(symIdx)
if len(p) != 0 && decodetypeKind(d.ctxt.Arch, p)&kindMask == kindInterface {
- for _, sig := range d.decodeIfaceMethods2(d.ldr, d.ctxt.Arch, symIdx, symRelocs) {
+ for _, sig := range d.decodeIfaceMethods2(d.ldr, d.ctxt.Arch, symIdx, &relocs) {
if d.ctxt.Debugvlog > 1 {
d.ctxt.Logf("reached iface method: %s\n", sig)
}
@@ -154,11 +141,12 @@
var methods []methodref2
for i := 0; i < relocs.Count; i++ {
- r := symRelocs[i]
- if r.Type == objabi.R_WEAKADDROFF {
+ r := relocs.At2(i)
+ t := r.Type()
+ if t == objabi.R_WEAKADDROFF {
continue
}
- if r.Type == objabi.R_METHODOFF {
+ if t == objabi.R_METHODOFF {
if i+2 >= relocs.Count {
panic("expect three consecutive R_METHODOFF relocs")
}
@@ -166,13 +154,13 @@
i += 2
continue
}
- if r.Type == objabi.R_USETYPE {
+ if t == objabi.R_USETYPE {
// type symbol used for DWARF. we need to load the symbol but it may not
// be otherwise reachable in the program.
// do nothing for now as we still load all type symbols.
continue
}
- d.mark(r.Sym, symIdx)
+ d.mark(r.Sym(), symIdx)
}
auxSyms = d.ldr.ReadAuxSyms(symIdx, auxSyms)
for i := 0; i < len(auxSyms); i++ {
@@ -194,7 +182,7 @@
// Decode runtime type information for type methods
// to help work out which methods can be called
// dynamically via interfaces.
- methodsigs := d.decodetypeMethods2(d.ldr, d.ctxt.Arch, symIdx, symRelocs)
+ methodsigs := d.decodetypeMethods2(d.ldr, d.ctxt.Arch, symIdx, &relocs)
if len(methods) != len(methodsigs) {
panic(fmt.Sprintf("%q has %d method relocations for %d methods", d.ldr.SymName(symIdx), len(methods), len(methodsigs)))
}
@@ -227,10 +215,10 @@
}
func (d *deadcodePass2) markMethod(m methodref2) {
- d.ReadRelocSyms(m.src)
- d.mark(d.rtmp[m.r].Sym, m.src)
- d.mark(d.rtmp[m.r+1].Sym, m.src)
- d.mark(d.rtmp[m.r+2].Sym, m.src)
+ relocs := d.ldr.Relocs(m.src)
+ d.mark(relocs.At2(m.r).Sym(), m.src)
+ d.mark(relocs.At2(m.r+1).Sym(), m.src)
+ d.mark(relocs.At2(m.r+2).Sym(), m.src)
}
func deadcode2(ctxt *Link) {
@@ -313,15 +301,15 @@
// the function type.
//
// Conveniently this is the layout of both runtime.method and runtime.imethod.
-func (d *deadcodePass2) decodeMethodSig2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, symRelocs []loader.Reloc, off, size, count int) []methodsig {
+func (d *deadcodePass2) decodeMethodSig2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, off, size, count int) []methodsig {
var buf bytes.Buffer
var methods []methodsig
for i := 0; i < count; i++ {
- buf.WriteString(decodetypeName2(ldr, symIdx, symRelocs, off))
- mtypSym := decodeRelocSym2(ldr, symIdx, symRelocs, int32(off+4))
+ buf.WriteString(decodetypeName3(ldr, symIdx, relocs, off))
+ mtypSym := decodeRelocSym3(ldr, symIdx, relocs, int32(off+4))
// FIXME: add some sort of caching here, since we may see some of the
// same symbols over time for param types.
- d.ReadRelocs(mtypSym)
+ mrelocs := ldr.Relocs(mtypSym)
mp := ldr.Data(mtypSym)
buf.WriteRune('(')
@@ -330,7 +318,7 @@
if i > 0 {
buf.WriteString(", ")
}
- a := decodetypeFuncInType2(ldr, arch, mtypSym, d.rtmp, i)
+ a := decodetypeFuncInType3(ldr, arch, mtypSym, &mrelocs, i)
buf.WriteString(ldr.SymName(a))
}
buf.WriteString(") (")
@@ -339,7 +327,7 @@
if i > 0 {
buf.WriteString(", ")
}
- a := decodetypeFuncOutType2(ldr, arch, mtypSym, d.rtmp, i)
+ a := decodetypeFuncOutType3(ldr, arch, mtypSym, &mrelocs, i)
buf.WriteString(ldr.SymName(a))
}
buf.WriteRune(')')
@@ -351,25 +339,26 @@
return methods
}
-func (d *deadcodePass2) decodeIfaceMethods2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, symRelocs []loader.Reloc) []methodsig {
+func (d *deadcodePass2) decodeIfaceMethods2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs) []methodsig {
p := ldr.Data(symIdx)
if decodetypeKind(arch, p)&kindMask != kindInterface {
panic(fmt.Sprintf("symbol %q is not an interface", ldr.SymName(symIdx)))
}
- rel := decodeReloc2(ldr, symIdx, symRelocs, int32(commonsize(arch)+arch.PtrSize))
- if rel.Sym == 0 {
+ rel := decodeReloc3(ldr, symIdx, relocs, int32(commonsize(arch)+arch.PtrSize))
+ s := rel.Sym()
+ if s == 0 {
return nil
}
- if rel.Sym != symIdx {
+ if s != symIdx {
panic(fmt.Sprintf("imethod slice pointer in %q leads to a different symbol", ldr.SymName(symIdx)))
}
- off := int(rel.Add) // array of reflect.imethod values
+ off := int(rel.Add()) // array of reflect.imethod values
numMethods := int(decodetypeIfaceMethodCount(arch, p))
sizeofIMethod := 4 + 4
- return d.decodeMethodSig2(ldr, arch, symIdx, symRelocs, off, sizeofIMethod, numMethods)
+ return d.decodeMethodSig2(ldr, arch, symIdx, relocs, off, sizeofIMethod, numMethods)
}
-func (d *deadcodePass2) decodetypeMethods2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, symRelocs []loader.Reloc) []methodsig {
+func (d *deadcodePass2) decodetypeMethods2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs) []methodsig {
p := ldr.Data(symIdx)
if !decodetypeHasUncommon(arch, p) {
panic(fmt.Sprintf("no methods on %q", ldr.SymName(symIdx)))
@@ -400,19 +389,5 @@
moff := int(decodeInuxi(arch, p[off+4+2+2:], 4))
off += moff // offset to array of reflect.method values
const sizeofMethod = 4 * 4 // sizeof reflect.method in program
- return d.decodeMethodSig2(ldr, arch, symIdx, symRelocs, off, sizeofMethod, mcount)
-}
-
-// readRelocs reads the relocations for the specified symbol into the
-// deadcode relocs work array. Use with care, since the work array
-// is a singleton.
-func (d *deadcodePass2) ReadRelocs(symIdx loader.Sym) {
- relocs := d.ldr.Relocs(symIdx)
- d.rtmp = relocs.ReadAll(d.rtmp)
-}
-
-// Like ReadRelocs, but only reads target symbols.
-func (d *deadcodePass2) ReadRelocSyms(symIdx loader.Sym) {
- relocs := d.ldr.Relocs(symIdx)
- d.rtmp = relocs.ReadSyms(d.rtmp)
+ return d.decodeMethodSig2(ldr, arch, symIdx, relocs, off, sizeofMethod, mcount)
}
diff --git a/src/cmd/link/internal/ld/decodesym2.go b/src/cmd/link/internal/ld/decodesym2.go
index 7896740..e93cc91 100644
--- a/src/cmd/link/internal/ld/decodesym2.go
+++ b/src/cmd/link/internal/ld/decodesym2.go
@@ -25,10 +25,24 @@
return loader.Reloc{}
}
+func decodeReloc3(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Reloc2 {
+ for j := 0; j < relocs.Count; j++ {
+ rel := relocs.At2(j)
+ if rel.Off() == off {
+ return rel
+ }
+ }
+ return loader.Reloc2{}
+}
+
func decodeRelocSym2(ldr *loader.Loader, symIdx loader.Sym, symRelocs []loader.Reloc, off int32) loader.Sym {
return decodeReloc2(ldr, symIdx, symRelocs, off).Sym
}
+func decodeRelocSym3(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Sym {
+ return decodeReloc3(ldr, symIdx, relocs, off).Sym()
+}
+
// decodetypeName2 decodes the name from a reflect.name.
func decodetypeName2(ldr *loader.Loader, symIdx loader.Sym, symRelocs []loader.Reloc, off int) string {
r := decodeRelocSym2(ldr, symIdx, symRelocs, int32(off))
@@ -41,6 +55,17 @@
return string(data[3 : 3+namelen])
}
+func decodetypeName3(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int) string {
+ r := decodeRelocSym3(ldr, symIdx, relocs, int32(off))
+ if r == 0 {
+ return ""
+ }
+
+ data := ldr.Data(r)
+ namelen := int(uint16(data[1])<<8 | uint16(data[2]))
+ return string(data[3 : 3+namelen])
+}
+
func decodetypeFuncInType2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, symRelocs []loader.Reloc, i int) loader.Sym {
uadd := commonsize(arch) + 4
if arch.PtrSize == 8 {
@@ -52,10 +77,25 @@
return decodeRelocSym2(ldr, symIdx, symRelocs, int32(uadd+i*arch.PtrSize))
}
+func decodetypeFuncInType3(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
+ uadd := commonsize(arch) + 4
+ if arch.PtrSize == 8 {
+ uadd += 4
+ }
+ if decodetypeHasUncommon(arch, ldr.Data(symIdx)) {
+ uadd += uncommonSize()
+ }
+ return decodeRelocSym3(ldr, symIdx, relocs, int32(uadd+i*arch.PtrSize))
+}
+
func decodetypeFuncOutType2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, symRelocs []loader.Reloc, i int) loader.Sym {
return decodetypeFuncInType2(ldr, arch, symIdx, symRelocs, i+decodetypeFuncInCount(arch, ldr.Data(symIdx)))
}
+func decodetypeFuncOutType3(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
+ return decodetypeFuncInType3(ldr, arch, symIdx, relocs, i+decodetypeFuncInCount(arch, ldr.Data(symIdx)))
+}
+
func decodetypeArrayElem2(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
// FIXME: it's inefficient to read the relocations each time. Add some
// sort of cache here, or pass in the relocs. Alternatively we could
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index 979d944..102fee5 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -520,6 +520,12 @@
var rr *oReader
switch p := s.PkgIdx; p {
case goobj2.PkgIdxInvalid:
+ // {0, X} with non-zero X is never a valid sym reference from a Go object.
+ // We steal this space for symbol references from external objects.
+ // In this case, X is just the global index.
+ if l.isExtReader(r) {
+ return Sym(s.SymIdx)
+ }
if s.SymIdx != 0 {
panic("bad sym ref")
}
@@ -1448,10 +1454,14 @@
func (relocs *Relocs) At2(j int) Reloc2 {
if relocs.l.isExtReader(relocs.r) {
- // TODO: implement this. How? Maybe we can construct the reloc
- // data for external symbols in the same byte form as the one
- // in the object file?
- panic("not implemented")
+ pp := relocs.l.payloads[relocs.li]
+ r := pp.relocs[j]
+ // XXX populate a goobj2.Reloc from external reloc record.
+ // Ugly. Maybe we just want to use this format to store the
+ // reloc record in the first place?
+ var b goobj2.Reloc2
+ b.Set(r.Off, r.Size, uint8(r.Type), r.Add, goobj2.SymRef{PkgIdx: 0, SymIdx: uint32(r.Sym)})
+ return Reloc2{&b, relocs.r, relocs.l}
}
return Reloc2{relocs.r.Reloc2(relocs.li, j), relocs.r, relocs.l}
}
