mirror of
https://github.com/golang/go
synced 2024-11-07 12:36:27 -07:00
[dev.link] cmd/link: move some work after deadcode
This is in preparation of delaying loading symbol content to after dead code elimination. Change-Id: Ia4ce82d9a42cc1a76c82f6d0eb9a54b0325ee3ba Reviewed-on: https://go-review.googlesource.com/c/go/+/197061 Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Jeremy Faller <jeremy@golang.org>
This commit is contained in:
Cherry Zhang
parent
6051fd0ad9
commit
e63c1df348
@ -415,37 +415,110 @@ func (ctxt *Link) loadlib() {
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}
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}
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switch ctxt.BuildMode {
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case BuildModeCShared, BuildModePlugin:
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s := ctxt.Syms.Lookup("runtime.islibrary", 0)
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s.Type = sym.SNOPTRDATA
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s.Attr |= sym.AttrDuplicateOK
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s.AddUint8(1)
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case BuildModeCArchive:
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s := ctxt.Syms.Lookup("runtime.isarchive", 0)
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s.Type = sym.SNOPTRDATA
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s.Attr |= sym.AttrDuplicateOK
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s.AddUint8(1)
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}
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iscgo = ctxt.Syms.ROLookup("x_cgo_init", 0) != nil
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// We now have enough information to determine the link mode.
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determineLinkMode(ctxt)
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// Recalculate pe parameters now that we have ctxt.LinkMode set.
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// Now that we know the link mode, trim the dynexp list.
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x := sym.AttrCgoExportDynamic
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if ctxt.LinkMode == LinkExternal {
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x = sym.AttrCgoExportStatic
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}
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w := 0
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for i := range dynexp {
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if dynexp[i].Attr&x != 0 {
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dynexp[w] = dynexp[i]
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w++
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}
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}
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dynexp = dynexp[:w]
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// Resolve ABI aliases in the list of cgo-exported functions.
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// This is necessary because we load the ABI0 symbol for all
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// cgo exports.
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for i, s := range dynexp {
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if s.Type != sym.SABIALIAS {
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continue
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}
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t := resolveABIAlias(s)
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t.Attr |= s.Attr
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t.SetExtname(s.Extname())
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dynexp[i] = t
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}
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// In internal link mode, read the host object files.
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if ctxt.LinkMode == LinkInternal {
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// Drop all the cgo_import_static declarations.
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// Turns out we won't be needing them.
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for _, s := range ctxt.Syms.Allsym {
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if s.Type == sym.SHOSTOBJ {
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// If a symbol was marked both
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// cgo_import_static and cgo_import_dynamic,
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// then we want to make it cgo_import_dynamic
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// now.
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if s.Extname() != "" && s.Dynimplib() != "" && !s.Attr.CgoExport() {
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s.Type = sym.SDYNIMPORT
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} else {
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s.Type = 0
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}
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}
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}
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hostobjs(ctxt)
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// If we have any undefined symbols in external
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// objects, try to read them from the libgcc file.
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any := false
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for _, s := range ctxt.Syms.Allsym {
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for i := range s.R {
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r := &s.R[i] // Copying sym.Reloc has measurable impact on performance
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if r.Sym != nil && r.Sym.Type == sym.SXREF && r.Sym.Name != ".got" {
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any = true
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break
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}
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}
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}
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if any {
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if *flagLibGCC == "" {
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*flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
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}
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if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
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// On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
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// In this case we fail to load libgcc.a and can encounter link
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// errors - see if we can find libcompiler_rt.a instead.
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*flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
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}
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if *flagLibGCC != "none" {
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hostArchive(ctxt, *flagLibGCC)
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}
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if ctxt.HeadType == objabi.Hwindows {
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Peinit(ctxt)
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if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
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hostArchive(ctxt, p)
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}
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if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
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hostArchive(ctxt, p)
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}
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// TODO: maybe do something similar to peimporteddlls to collect all lib names
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// and try link them all to final exe just like libmingwex.a and libmingw32.a:
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/*
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for:
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#cgo windows LDFLAGS: -lmsvcrt -lm
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import:
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libmsvcrt.a libm.a
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*/
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}
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}
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} else {
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hostlinksetup(ctxt)
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}
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if ctxt.HeadType == objabi.Hdarwin && ctxt.LinkMode == LinkExternal {
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*FlagTextAddr = 0
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}
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// We've loaded all the code now.
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ctxt.Loaded = true
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if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && objabi.GOOS != "aix" {
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toc := ctxt.Syms.Lookup(".TOC.", 0)
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toc.Type = sym.SDYNIMPORT
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}
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// Record whether we can use plugins.
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ctxt.canUsePlugins = (ctxt.Syms.ROLookup("plugin.Open", sym.SymVerABIInternal) != nil)
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if ctxt.LinkMode == LinkExternal && !iscgo && ctxt.LibraryByPkg["runtime/cgo"] == nil && !(objabi.GOOS == "darwin" && (ctxt.Arch.Family == sys.AMD64 || ctxt.Arch.Family == sys.I386)) {
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// This indicates a user requested -linkmode=external.
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@ -464,24 +537,92 @@ func (ctxt *Link) loadlib() {
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}
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}
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if ctxt.LinkMode == LinkInternal {
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// Drop all the cgo_import_static declarations.
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// Turns out we won't be needing them.
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for _, s := range ctxt.Syms.Allsym {
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if s.Type == sym.SHOSTOBJ {
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// If a symbol was marked both
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// cgo_import_static and cgo_import_dynamic,
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// then we want to make it cgo_import_dynamic
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// now.
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if s.Extname() != "" && s.Dynimplib() != "" && !s.Attr.CgoExport() {
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s.Type = sym.SDYNIMPORT
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} else {
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s.Type = 0
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importcycles()
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// put symbols into Textp
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// do it in postorder so that packages are laid down in dependency order
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// internal first, then everything else
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ctxt.Library = postorder(ctxt.Library)
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for _, doInternal := range [2]bool{true, false} {
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for _, lib := range ctxt.Library {
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if isRuntimeDepPkg(lib.Pkg) != doInternal {
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continue
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}
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ctxt.Textp = append(ctxt.Textp, lib.Textp...)
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for _, s := range lib.DupTextSyms {
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if !s.Attr.OnList() {
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ctxt.Textp = append(ctxt.Textp, s)
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s.Attr |= sym.AttrOnList
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// dupok symbols may be defined in multiple packages. its
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// associated package is chosen sort of arbitrarily (the
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// first containing package that the linker loads). canonicalize
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// it here to the package with which it will be laid down
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// in text.
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s.File = objabi.PathToPrefix(lib.Pkg)
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}
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}
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}
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}
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if len(ctxt.Shlibs) > 0 {
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// We might have overwritten some functions above (this tends to happen for the
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// autogenerated type equality/hashing functions) and we don't want to generated
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// pcln table entries for these any more so remove them from Textp.
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textp := make([]*sym.Symbol, 0, len(ctxt.Textp))
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for _, s := range ctxt.Textp {
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if s.Type != sym.SDYNIMPORT {
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textp = append(textp, s)
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}
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}
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ctxt.Textp = textp
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}
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}
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// Set up flags and special symbols depending on the platform build mode.
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func (ctxt *Link) linksetup() {
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switch ctxt.BuildMode {
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case BuildModeCShared, BuildModePlugin:
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s := ctxt.Syms.Lookup("runtime.islibrary", 0)
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s.Type = sym.SNOPTRDATA
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s.Attr |= sym.AttrDuplicateOK
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s.AddUint8(1)
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case BuildModeCArchive:
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s := ctxt.Syms.Lookup("runtime.isarchive", 0)
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s.Type = sym.SNOPTRDATA
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s.Attr |= sym.AttrDuplicateOK
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s.AddUint8(1)
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}
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// Recalculate pe parameters now that we have ctxt.LinkMode set.
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if ctxt.HeadType == objabi.Hwindows {
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Peinit(ctxt)
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}
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if ctxt.HeadType == objabi.Hdarwin && ctxt.LinkMode == LinkExternal {
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*FlagTextAddr = 0
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}
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// If there are no dynamic libraries needed, gcc disables dynamic linking.
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// Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
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// assumes that a dynamic binary always refers to at least one dynamic library.
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// Rather than be a source of test cases for glibc, disable dynamic linking
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// the same way that gcc would.
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//
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// Exception: on OS X, programs such as Shark only work with dynamic
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// binaries, so leave it enabled on OS X (Mach-O) binaries.
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// Also leave it enabled on Solaris which doesn't support
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// statically linked binaries.
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if ctxt.BuildMode == BuildModeExe {
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if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
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*FlagD = true
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}
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}
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if ctxt.LinkMode == LinkExternal && ctxt.Arch.Family == sys.PPC64 && objabi.GOOS != "aix" {
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toc := ctxt.Syms.Lookup(".TOC.", 0)
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toc.Type = sym.SDYNIMPORT
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}
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// The Android Q linker started to complain about underalignment of the our TLS
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// section. We don't actually use the section on android, so dont't
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// generate it.
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@ -542,93 +683,6 @@ func (ctxt *Link) loadlib() {
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moduledata.Attr |= sym.AttrReachable
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ctxt.Moduledata = moduledata
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// Now that we know the link mode, trim the dynexp list.
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x := sym.AttrCgoExportDynamic
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if ctxt.LinkMode == LinkExternal {
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x = sym.AttrCgoExportStatic
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}
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w := 0
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for i := range dynexp {
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if dynexp[i].Attr&x != 0 {
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dynexp[w] = dynexp[i]
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w++
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}
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}
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dynexp = dynexp[:w]
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// In internal link mode, read the host object files.
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if ctxt.LinkMode == LinkInternal {
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hostobjs(ctxt)
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// If we have any undefined symbols in external
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// objects, try to read them from the libgcc file.
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any := false
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for _, s := range ctxt.Syms.Allsym {
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for i := range s.R {
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r := &s.R[i] // Copying sym.Reloc has measurable impact on performance
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if r.Sym != nil && r.Sym.Type == sym.SXREF && r.Sym.Name != ".got" {
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any = true
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break
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}
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}
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}
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if any {
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if *flagLibGCC == "" {
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*flagLibGCC = ctxt.findLibPathCmd("--print-libgcc-file-name", "libgcc")
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}
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if runtime.GOOS == "openbsd" && *flagLibGCC == "libgcc.a" {
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// On OpenBSD `clang --print-libgcc-file-name` returns "libgcc.a".
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// In this case we fail to load libgcc.a and can encounter link
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// errors - see if we can find libcompiler_rt.a instead.
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*flagLibGCC = ctxt.findLibPathCmd("--print-file-name=libcompiler_rt.a", "libcompiler_rt")
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}
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if *flagLibGCC != "none" {
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hostArchive(ctxt, *flagLibGCC)
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}
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if ctxt.HeadType == objabi.Hwindows {
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if p := ctxt.findLibPath("libmingwex.a"); p != "none" {
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hostArchive(ctxt, p)
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}
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if p := ctxt.findLibPath("libmingw32.a"); p != "none" {
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hostArchive(ctxt, p)
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}
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// TODO: maybe do something similar to peimporteddlls to collect all lib names
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// and try link them all to final exe just like libmingwex.a and libmingw32.a:
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/*
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for:
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#cgo windows LDFLAGS: -lmsvcrt -lm
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import:
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libmsvcrt.a libm.a
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*/
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}
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}
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} else {
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hostlinksetup(ctxt)
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}
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// We've loaded all the code now.
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ctxt.Loaded = true
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// Record whether we can use plugins.
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ctxt.canUsePlugins = (ctxt.Syms.ROLookup("plugin.Open", sym.SymVerABIInternal) != nil)
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// If there are no dynamic libraries needed, gcc disables dynamic linking.
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// Because of this, glibc's dynamic ELF loader occasionally (like in version 2.13)
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// assumes that a dynamic binary always refers to at least one dynamic library.
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// Rather than be a source of test cases for glibc, disable dynamic linking
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// the same way that gcc would.
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//
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// Exception: on OS X, programs such as Shark only work with dynamic
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// binaries, so leave it enabled on OS X (Mach-O) binaries.
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// Also leave it enabled on Solaris which doesn't support
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// statically linked binaries.
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if ctxt.BuildMode == BuildModeExe {
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if havedynamic == 0 && ctxt.HeadType != objabi.Hdarwin && ctxt.HeadType != objabi.Hsolaris {
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*FlagD = true
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}
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}
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// If package versioning is required, generate a hash of the
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// packages used in the link.
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if ctxt.BuildMode == BuildModeShared || ctxt.BuildMode == BuildModePlugin || ctxt.CanUsePlugins() {
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@ -646,59 +700,6 @@ func (ctxt *Link) loadlib() {
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got.Attr |= sym.AttrReachable
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}
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}
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importcycles()
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// put symbols into Textp
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// do it in postorder so that packages are laid down in dependency order
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// internal first, then everything else
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ctxt.Library = postorder(ctxt.Library)
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for _, doInternal := range [2]bool{true, false} {
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for _, lib := range ctxt.Library {
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if isRuntimeDepPkg(lib.Pkg) != doInternal {
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continue
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}
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ctxt.Textp = append(ctxt.Textp, lib.Textp...)
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for _, s := range lib.DupTextSyms {
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if !s.Attr.OnList() {
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ctxt.Textp = append(ctxt.Textp, s)
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s.Attr |= sym.AttrOnList
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// dupok symbols may be defined in multiple packages. its
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// associated package is chosen sort of arbitrarily (the
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// first containing package that the linker loads). canonicalize
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// it here to the package with which it will be laid down
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// in text.
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s.File = objabi.PathToPrefix(lib.Pkg)
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}
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}
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}
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}
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if len(ctxt.Shlibs) > 0 {
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// We might have overwritten some functions above (this tends to happen for the
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// autogenerated type equality/hashing functions) and we don't want to generated
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// pcln table entries for these any more so remove them from Textp.
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textp := make([]*sym.Symbol, 0, len(ctxt.Textp))
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for _, s := range ctxt.Textp {
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if s.Type != sym.SDYNIMPORT {
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textp = append(textp, s)
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}
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}
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ctxt.Textp = textp
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}
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// Resolve ABI aliases in the list of cgo-exported functions.
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// This is necessary because we load the ABI0 symbol for all
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// cgo exports.
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for i, s := range dynexp {
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if s.Type != sym.SABIALIAS {
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continue
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}
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t := resolveABIAlias(s)
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t.Attr |= s.Attr
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t.SetExtname(s.Extname())
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dynexp[i] = t
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}
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}
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// mangleTypeSym shortens the names of symbols that represent Go types
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@ -208,9 +208,10 @@ func Main(arch *sys.Arch, theArch Arch) {
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}
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ctxt.loadlib()
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ctxt.dostrdata()
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deadcode(ctxt)
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//ctxt.dumpsyms() // XXX
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ctxt.linksetup()
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ctxt.dostrdata()
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dwarfGenerateDebugInfo(ctxt)
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if objabi.Fieldtrack_enabled != 0 {
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fieldtrack(ctxt)
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