diff options
Diffstat (limited to 'src/cmd/link/internal/ld/deadcode.go')
| -rw-r--r-- | src/cmd/link/internal/ld/deadcode.go | 96 |
1 files changed, 63 insertions, 33 deletions
diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go index 0269429723..d8813fa936 100644 --- a/src/cmd/link/internal/ld/deadcode.go +++ b/src/cmd/link/internal/ld/deadcode.go @@ -62,6 +62,12 @@ func (d *deadcodePass) init() { } } names = append(names, *flagEntrySymbol) + if !d.ctxt.linkShared && d.ctxt.BuildMode != BuildModePlugin { + // runtime.buildVersion and runtime.modinfo are referenced in .go.buildinfo section + // (see function buildinfo in data.go). They should normally be reachable from the + // runtime. Just make it explicit, in case. + names = append(names, "runtime.buildVersion", "runtime.modinfo") + } if d.ctxt.BuildMode == BuildModePlugin { names = append(names, objabi.PathToPrefix(*flagPluginPath)+"..inittask", objabi.PathToPrefix(*flagPluginPath)+".main", "go.plugin.tabs") @@ -106,39 +112,67 @@ func (d *deadcodePass) flood() { if isgotype { usedInIface = d.ldr.AttrUsedInIface(symIdx) - p := d.ldr.Data(symIdx) - if len(p) != 0 && decodetypeKind(d.ctxt.Arch, p)&kindMask == kindInterface { - for _, sig := range d.decodeIfaceMethods(d.ldr, d.ctxt.Arch, symIdx, &relocs) { - if d.ctxt.Debugvlog > 1 { - d.ctxt.Logf("reached iface method: %v\n", sig) - } - d.ifaceMethod[sig] = true - } - } } methods = methods[:0] for i := 0; i < relocs.Count(); i++ { r := relocs.At(i) t := r.Type() - if t == objabi.R_WEAKADDROFF { + switch t { + case objabi.R_WEAKADDROFF: continue - } - if t == objabi.R_METHODOFF { + case objabi.R_METHODOFF: if i+2 >= relocs.Count() { panic("expect three consecutive R_METHODOFF relocs") } if usedInIface { methods = append(methods, methodref{src: symIdx, r: i}) + // The method descriptor is itself a type descriptor, and + // it can be used to reach other types, e.g. by using + // reflect.Type.Method(i).Type.In(j). We need to traverse + // its child types with UsedInIface set. (See also the + // comment below.) + rs := r.Sym() + if !d.ldr.AttrUsedInIface(rs) { + d.ldr.SetAttrUsedInIface(rs, true) + if d.ldr.AttrReachable(rs) { + d.ldr.SetAttrReachable(rs, false) + d.mark(rs, symIdx) + } + } } i += 2 continue - } - if t == objabi.R_USETYPE { + case 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 + case objabi.R_USEIFACE: + // R_USEIFACE is a marker relocation that tells the linker the type is + // converted to an interface, i.e. should have UsedInIface set. See the + // comment below for why we need to unset the Reachable bit and re-mark it. + rs := r.Sym() + if !d.ldr.AttrUsedInIface(rs) { + d.ldr.SetAttrUsedInIface(rs, true) + if d.ldr.AttrReachable(rs) { + d.ldr.SetAttrReachable(rs, false) + d.mark(rs, symIdx) + } + } + continue + case objabi.R_USEIFACEMETHOD: + // R_USEIFACEMETHOD is a marker relocation that marks an interface + // method as used. + rs := r.Sym() + if d.ldr.SymType(rs) != sym.SDYNIMPORT { // don't decode DYNIMPORT symbol (we'll mark all exported methods anyway) + m := d.decodeIfaceMethod(d.ldr, d.ctxt.Arch, rs, r.Add()) + if d.ctxt.Debugvlog > 1 { + d.ctxt.Logf("reached iface method: %v\n", m) + } + d.ifaceMethod[m] = true + } + continue } rs := r.Sym() if isgotype && usedInIface && d.ldr.IsGoType(rs) && !d.ldr.AttrUsedInIface(rs) { @@ -161,13 +195,9 @@ func (d *deadcodePass) flood() { naux := d.ldr.NAux(symIdx) for i := 0; i < naux; i++ { a := d.ldr.Aux(symIdx, i) - if a.Type() == goobj.AuxGotype && !d.ctxt.linkShared { + if a.Type() == goobj.AuxGotype { // A symbol being reachable doesn't imply we need its // type descriptor. Don't mark it. - // TODO: when -linkshared, the GCProg generation code - // seems to need it. I'm not sure why. I think it could - // just reach to the type descriptor's data without - // requiring to mark it reachable. continue } d.mark(a.Sym(), symIdx) @@ -209,15 +239,21 @@ func (d *deadcodePass) mark(symIdx, parent loader.Sym) { if symIdx != 0 && !d.ldr.AttrReachable(symIdx) { d.wq.push(symIdx) d.ldr.SetAttrReachable(symIdx, true) - if objabi.Fieldtrack_enabled != 0 { + if objabi.Fieldtrack_enabled != 0 && d.ldr.Reachparent[symIdx] == 0 { d.ldr.Reachparent[symIdx] = parent } if *flagDumpDep { to := d.ldr.SymName(symIdx) if to != "" { + if d.ldr.AttrUsedInIface(symIdx) { + to += " <UsedInIface>" + } from := "_" if parent != 0 { from = d.ldr.SymName(parent) + if d.ldr.AttrUsedInIface(parent) { + from += " <UsedInIface>" + } } fmt.Printf("%s -> %s\n", from, to) } @@ -349,23 +385,17 @@ func (d *deadcodePass) decodeMethodSig(ldr *loader.Loader, arch *sys.Arch, symId return methods } -func (d *deadcodePass) decodeIfaceMethods(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs) []methodsig { +// Decode the method of interface type symbol symIdx at offset off. +func (d *deadcodePass) decodeIfaceMethod(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, off int64) methodsig { p := ldr.Data(symIdx) if decodetypeKind(arch, p)&kindMask != kindInterface { panic(fmt.Sprintf("symbol %q is not an interface", ldr.SymName(symIdx))) } - rel := decodeReloc(ldr, symIdx, relocs, int32(commonsize(arch)+arch.PtrSize)) - s := rel.Sym() - if s == 0 { - return nil - } - 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 - numMethods := int(decodetypeIfaceMethodCount(arch, p)) - sizeofIMethod := 4 + 4 - return d.decodeMethodSig(ldr, arch, symIdx, relocs, off, sizeofIMethod, numMethods) + relocs := ldr.Relocs(symIdx) + var m methodsig + m.name = decodetypeName(ldr, symIdx, &relocs, int(off)) + m.typ = decodeRelocSym(ldr, symIdx, &relocs, int32(off+4)) + return m } func (d *deadcodePass) decodetypeMethods(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs) []methodsig { |