[dev.link] cmd/link: directly use loader.ExtReloc in ELF relocation generation
Convert the part that uses relocations to use loader.ExtReloc
directly. It still uses sym.Symbols for now, but not sym.Relocs.
This reduces some memory usage: linking cmd/compile with external
linking,
name old allocs/op new allocs/op delta
Loadlibfull_GC 52.2MB ± 0% 13.9MB ± 0% -73.40% (p=0.008 n=5+5)
name old live-B new live-B delta
Loadlibfull_GC 75.5M ± 0% 61.9M ± 0% -18.02% (p=0.008 n=5+5)
Change-Id: I317ecbf516063c42b255b2caba310ea6281342d7
Reviewed-on: https://go-review.googlesource.com/c/go/+/231319
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/src/cmd/link/internal/amd64/asm.go b/src/cmd/link/internal/amd64/asm.go
index e2c33b8..c2d5470 100644
--- a/src/cmd/link/internal/amd64/asm.go
+++ b/src/cmd/link/internal/amd64/asm.go
@@ -393,36 +393,38 @@
return false
}
-func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
+func elfreloc2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym, r loader.ExtRelocView, sectoff int64) bool {
ctxt.Out.Write64(uint64(sectoff))
- elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
- switch r.Type {
+ xsym := ldr.Syms[r.Xsym]
+ elfsym := ld.ElfSymForReloc(ctxt, xsym)
+ siz := r.Siz()
+ switch r.Type() {
default:
return false
case objabi.R_ADDR, objabi.R_DWARFSECREF:
- if r.Siz == 4 {
+ if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_32) | uint64(elfsym)<<32)
- } else if r.Siz == 8 {
+ } else if siz == 8 {
ctxt.Out.Write64(uint64(elf.R_X86_64_64) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_TLS_LE:
- if r.Siz == 4 {
+ if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_TPOFF32) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_TLS_IE:
- if r.Siz == 4 {
+ if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_GOTTPOFF) | uint64(elfsym)<<32)
} else {
return false
}
case objabi.R_CALL:
- if r.Siz == 4 {
- if r.Xsym.Type == sym.SDYNIMPORT {
+ if siz == 4 {
+ if xsym.Type == sym.SDYNIMPORT {
if ctxt.DynlinkingGo() {
ctxt.Out.Write64(uint64(elf.R_X86_64_PLT32) | uint64(elfsym)<<32)
} else {
@@ -435,8 +437,8 @@
return false
}
case objabi.R_PCREL:
- if r.Siz == 4 {
- if r.Xsym.Type == sym.SDYNIMPORT && r.Xsym.ElfType() == elf.STT_FUNC {
+ if siz == 4 {
+ if xsym.Type == sym.SDYNIMPORT && xsym.ElfType() == elf.STT_FUNC {
ctxt.Out.Write64(uint64(elf.R_X86_64_PLT32) | uint64(elfsym)<<32)
} else {
ctxt.Out.Write64(uint64(elf.R_X86_64_PC32) | uint64(elfsym)<<32)
@@ -445,7 +447,7 @@
return false
}
case objabi.R_GOTPCREL:
- if r.Siz == 4 {
+ if siz == 4 {
ctxt.Out.Write64(uint64(elf.R_X86_64_GOTPCREL) | uint64(elfsym)<<32)
} else {
return false
diff --git a/src/cmd/link/internal/amd64/obj.go b/src/cmd/link/internal/amd64/obj.go
index 1fbbf60..645547c 100644
--- a/src/cmd/link/internal/amd64/obj.go
+++ b/src/cmd/link/internal/amd64/obj.go
@@ -52,7 +52,7 @@
Archrelocvariant: archrelocvariant,
Asmb: asmb,
Asmb2: asmb2,
- Elfreloc1: elfreloc1,
+ Elfreloc2: elfreloc2,
Elfsetupplt: elfsetupplt,
Gentext2: gentext2,
Machoreloc1: machoreloc1,
diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 83f100c..78298be 100644
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1374,6 +1374,11 @@
}
func elfrelocsect(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
+ if !ctxt.IsAMD64() {
+ elfrelocsect2(ctxt, sect, syms)
+ return
+ }
+
// If main section is SHT_NOBITS, nothing to relocate.
// Also nothing to relocate in .shstrtab.
if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
@@ -1394,6 +1399,7 @@
}
}
+ ldr := ctxt.loader
eaddr := int32(sect.Vaddr + sect.Length)
for _, s := range syms {
if !s.Attr.Reachable() {
@@ -1402,24 +1408,23 @@
if s.Value >= int64(eaddr) {
break
}
- for ri := range s.R {
- r := &s.R[ri]
- if r.Done {
+ i := loader.Sym(s.SymIdx)
+ relocs := ldr.ExtRelocs(i)
+ for ri := 0; ri < relocs.Count(); ri++ {
+ r := relocs.At(ri)
+ if r.Xsym == 0 {
+ Errorf(s, "missing xsym in relocation %v", ldr.SymName(r.Sym()))
continue
}
- if r.Xsym == nil {
- Errorf(s, "missing xsym in relocation %#v %#v", r.Sym.Name, s)
- continue
- }
- esr := ElfSymForReloc(ctxt, r.Xsym)
+ esr := ElfSymForReloc(ctxt, ldr.Syms[r.Xsym])
if esr == 0 {
- Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Sym.Name, r.Xsym.Name, r.Sym.Type, r.Sym.Type)
+ Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.Syms[r.Sym()].Name, ldr.Syms[r.Xsym].Name, ldr.Syms[r.Sym()].Type, ldr.Syms[r.Sym()].Type)
}
- if !r.Xsym.Attr.Reachable() {
- Errorf(s, "unreachable reloc %d (%s) target %v", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Xsym.Name)
+ if !ldr.AttrReachable(r.Xsym) {
+ Errorf(s, "unreachable reloc %d (%s) target %v", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.Syms[r.Xsym].Name)
}
- if !thearch.Elfreloc1(ctxt, r, int64(uint64(s.Value+int64(r.Off))-sect.Vaddr)) {
- Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Siz, r.Sym.Name)
+ if !thearch.Elfreloc2(ctxt, ldr, i, r, int64(uint64(s.Value+int64(r.Off()))-sect.Vaddr)) {
+ Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), r.Siz(), ldr.Syms[r.Sym()].Name)
}
}
}
diff --git a/src/cmd/link/internal/ld/elf2.go b/src/cmd/link/internal/ld/elf2.go
index 3f7d72b..07b64cf 100644
--- a/src/cmd/link/internal/ld/elf2.go
+++ b/src/cmd/link/internal/ld/elf2.go
@@ -23,3 +23,57 @@
elfstr[nelfstr].off = off
nelfstr++
}
+
+func elfrelocsect2(ctxt *Link, sect *sym.Section, syms []*sym.Symbol) {
+ // If main section is SHT_NOBITS, nothing to relocate.
+ // Also nothing to relocate in .shstrtab.
+ if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
+ return
+ }
+ if sect.Name == ".shstrtab" {
+ return
+ }
+
+ sect.Reloff = uint64(ctxt.Out.Offset())
+ for i, s := range syms {
+ if !s.Attr.Reachable() {
+ continue
+ }
+ if uint64(s.Value) >= sect.Vaddr {
+ syms = syms[i:]
+ break
+ }
+ }
+
+ eaddr := int32(sect.Vaddr + sect.Length)
+ for _, s := range syms {
+ if !s.Attr.Reachable() {
+ continue
+ }
+ if s.Value >= int64(eaddr) {
+ break
+ }
+ for ri := range s.R {
+ r := &s.R[ri]
+ if r.Done {
+ continue
+ }
+ if r.Xsym == nil {
+ Errorf(s, "missing xsym in relocation %#v %#v", r.Sym.Name, s)
+ continue
+ }
+ esr := ElfSymForReloc(ctxt, r.Xsym)
+ if esr == 0 {
+ Errorf(s, "reloc %d (%s) to non-elf symbol %s (outer=%s) %d (%s)", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Sym.Name, r.Xsym.Name, r.Sym.Type, r.Sym.Type)
+ }
+ if !r.Xsym.Attr.Reachable() {
+ Errorf(s, "unreachable reloc %d (%s) target %v", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Xsym.Name)
+ }
+ if !thearch.Elfreloc1(ctxt, r, int64(uint64(s.Value+int64(r.Off))-sect.Vaddr)) {
+ Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Siz, r.Sym.Name)
+ }
+ }
+ }
+
+ sect.Rellen = uint64(ctxt.Out.Offset()) - sect.Reloff
+}
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index a328efd..3c60901 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -270,6 +270,7 @@
Asmb2 func(*Link)
Elfreloc1 func(*Link, *sym.Reloc, int64) bool
+ Elfreloc2 func(*Link, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
Gentext func(*Link)
Gentext2 func(*Link, *loader.Loader)
@@ -2825,9 +2826,9 @@
ctxt.Textp = textp
}
-func (ctxt *Link) loadlibfull(symGroupType []sym.SymKind, needReloc bool) {
+func (ctxt *Link) loadlibfull(symGroupType []sym.SymKind, needReloc, needExtReloc bool) {
// Load full symbol contents, resolve indexed references.
- ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms, needReloc)
+ ctxt.loader.LoadFull(ctxt.Arch, ctxt.Syms, needReloc, needExtReloc)
// Convert ctxt.Moduledata2 to ctxt.Moduledata, etc
if ctxt.Moduledata2 != 0 {
diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index 6bd6a8e..1ed8ccb 100644
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -335,10 +335,13 @@
// An exception is internal linking on Windows, see pe.go:addPEBaseRelocSym
// Wasm is another exception, where it applies text relocations in Asmb2.
needReloc := (ctxt.IsWindows() && ctxt.IsInternal()) || ctxt.IsWasm()
- ctxt.loadlibfull(symGroupType, needReloc) // XXX do it here for now
+ // On AMD64 ELF, we directly use the loader's ExtRelocs, so we don't
+ // need conversion. Otherwise we do.
+ needExtReloc := ctxt.IsExternal() && !(ctxt.IsAMD64() && ctxt.IsELF)
+ ctxt.loadlibfull(symGroupType, needReloc, needExtReloc) // XXX do it here for now
} else {
bench.Start("loadlibfull")
- ctxt.loadlibfull(symGroupType, true) // XXX do it here for now
+ ctxt.loadlibfull(symGroupType, true, false) // XXX do it here for now
bench.Start("reloc")
ctxt.reloc2()
}
diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go
index f4d9164..2627218 100644
--- a/src/cmd/link/internal/loader/loader.go
+++ b/src/cmd/link/internal/loader/loader.go
@@ -56,6 +56,14 @@
Xadd int64
}
+// ExtRelocView is a view of an external relocation.
+// It is intended to be constructed on the fly, such as ExtRelocs.At.
+// It is not the data structure used to store the payload internally.
+type ExtRelocView struct {
+ Reloc2
+ *ExtReloc
+}
+
// Reloc2 holds a "handle" to access a relocation record from an
// object file.
type Reloc2 struct {
@@ -1116,7 +1124,7 @@
l.outdata = make([][]byte, l.extStart)
}
-// SetExtRelocs sets the section of the i-th symbol. i is global index.
+// SetExtRelocs sets the external relocations of the i-th symbol. i is global index.
func (l *Loader) SetExtRelocs(i Sym, relocs []ExtReloc) {
l.extRelocs[i] = relocs
}
@@ -1699,6 +1707,24 @@
}
}
+// ExtRelocs returns the external relocations of the i-th symbol.
+func (l *Loader) ExtRelocs(i Sym) ExtRelocs {
+ return ExtRelocs{l.Relocs(i), l.extRelocs[i]}
+}
+
+// ExtRelocs represents the set of external relocations of a symbol.
+type ExtRelocs struct {
+ rs Relocs
+ es []ExtReloc
+}
+
+func (ers ExtRelocs) Count() int { return len(ers.es) }
+
+func (ers ExtRelocs) At(j int) ExtRelocView {
+ i := ers.es[j].Idx
+ return ExtRelocView{ers.rs.At2(i), &ers.es[j]}
+}
+
// RelocByOff implements sort.Interface for sorting relocations by offset.
type RelocByOff []Reloc
@@ -2033,7 +2059,7 @@
}
// Load full contents.
-func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc bool) {
+func (l *Loader) LoadFull(arch *sys.Arch, syms *sym.Symbols, needReloc, needExtReloc bool) {
// create all Symbols first.
l.growSyms(l.NSym())
l.growSects(l.NSym())
@@ -2047,7 +2073,7 @@
nr := 0 // total number of sym.Reloc's we'll need
for _, o := range l.objs[1:] {
- nr += loadObjSyms(l, syms, o.r, needReloc)
+ nr += loadObjSyms(l, syms, o.r, needReloc, needExtReloc)
}
// Make a first pass through the external symbols, making
@@ -2063,7 +2089,7 @@
if needReloc {
nr += len(pp.relocs)
}
- if int(i) < len(l.extRelocs) {
+ if needExtReloc && int(i) < len(l.extRelocs) {
nr += len(l.extRelocs[i])
}
// create and install the sym.Symbol here so that l.Syms will
@@ -2079,7 +2105,7 @@
// allocate a single large slab of relocations for all live symbols
if nr != 0 {
l.relocBatch = make([]sym.Reloc, nr)
- if len(l.extRelocs) != 0 {
+ if needExtReloc {
l.relocExtBatch = make([]sym.RelocExt, nr)
}
}
@@ -2102,8 +2128,9 @@
relocs := l.Relocs(i)
l.convertRelocations(i, &relocs, s, false)
}
-
- l.convertExtRelocs(s, i)
+ if needExtReloc {
+ l.convertExtRelocs(s, i)
+ }
// Copy data
s.P = pp.data
@@ -2114,7 +2141,7 @@
// load contents of defined symbols
for _, o := range l.objs[1:] {
- loadObjFull(l, o.r, needReloc)
+ loadObjFull(l, o.r, needReloc, needExtReloc)
}
// Sanity check: we should have consumed all batched allocations.
@@ -2170,17 +2197,21 @@
l.plt = nil
l.got = nil
l.dynid = nil
- l.relocVariant = nil
- l.extRelocs = nil
+ if needExtReloc { // converted to sym.Relocs, drop loader references
+ l.relocVariant = nil
+ l.extRelocs = nil
+ }
// Drop fields that are no longer needed.
for _, i := range l.extReader.syms {
pp := l.getPayload(i)
pp.name = ""
- pp.relocs = nil
- pp.reltypes = nil
pp.auxs = nil
pp.data = nil
+ if needExtReloc {
+ pp.relocs = nil
+ pp.reltypes = nil
+ }
}
}
@@ -2450,7 +2481,7 @@
// loadObjSyms creates sym.Symbol objects for the live Syms in the
// object corresponding to object reader "r". Return value is the
// number of sym.Reloc entries required for all the new symbols.
-func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader, needReloc bool) int {
+func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader, needReloc, needExtReloc bool) int {
nr := 0
for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
gi := r.syms[i]
@@ -2483,7 +2514,7 @@
if needReloc {
nr += r.NReloc(i)
}
- if int(gi) < len(l.extRelocs) {
+ if needExtReloc && int(gi) < len(l.extRelocs) {
nr += len(l.extRelocs[gi])
}
}
@@ -2690,7 +2721,7 @@
}
}
-func loadObjFull(l *Loader, r *oReader, needReloc bool) {
+func loadObjFull(l *Loader, r *oReader, needReloc, needExtReloc bool) {
for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
// A symbol may be a dup or overwritten. In this case, its
// content will actually be provided by a different object
@@ -2722,8 +2753,9 @@
l.relocBatch = batch[relocs.Count():]
l.convertRelocations(gi, &relocs, s, false)
}
-
- l.convertExtRelocs(s, gi)
+ if needExtReloc {
+ l.convertExtRelocs(s, gi)
+ }
// Aux symbol info
auxs := r.Auxs(i)
