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[dev.link] cmd/link: record go.itablink symbols during object file read

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Change the new loader to keep a note of the set of "go.itablink.*"
symbols (using a small map), and add a method that clients can use to
query whether a given global index corresponds to a "go.itablink.*"
sym. This eliminates one instance of raw symbol name reading/matching
during new deadcode, which should produce a minor speedup.

Change-Id: I5915773a3f33c16099ccd68592dbba783d909bc9
Reviewed-on: https://go-review.googlesource.com/c/go/+/201400
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2019-10-16 09:29:56 -04:00
parent 8011051361
commit 6cbf37b30b
2 changed files with 16 additions and 3 deletions
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3
src/cmd/link/internal/ld/deadcode2.go
View File

@ -11,7 +11,6 @@ import (
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"fmt"
"strings"
"unicode"
)
@ -226,7 +225,7 @@ func deadcode2(ctxt *Link) {
// (When BuildModeShared, always keep itablinks.)
for i := 1; i < n; i++ {
s := loader.Sym(i)
if strings.HasPrefix(ldr.RawSymName(s), "go.itablink.") { // TODO: use an attribute instread of checking name
if ldr.IsItabLink(s) {
relocs := ldr.Relocs(s)
if relocs.Count > 0 && ldr.Reachable.Has(relocs.At(0).Sym) {
ldr.Reachable.Set(s)

16
src/cmd/link/internal/loader/loader.go
View File

@ -100,6 +100,8 @@ type Loader struct {
symsByName map[nameVer]Sym // map symbol name to index
overwrite map[Sym]Sym // overwrite[i]=j if symbol j overwrites symbol i
itablink map[Sym]struct{} // itablink[j] defined if j is go.itablink.*
objByPkg map[string]*oReader // map package path to its Go object reader
Syms []*sym.Symbol // indexed symbols. XXX we still make sym.Symbol for now.
@ -114,6 +116,7 @@ func NewLoader() *Loader {
symsByName: make(map[nameVer]Sym),
objByPkg: make(map[string]*oReader),
overwrite: make(map[Sym]Sym),
itablink: make(map[Sym]struct{}),
}
}
@ -369,6 +372,14 @@ func (l *Loader) IsGoType(i Sym) bool {
return l.SymAttr(i)&goobj2.SymFlagGoType != 0
}
// Returns whether this is a "go.itablink.*" symbol.
func (l *Loader) IsItabLink(i Sym) bool {
if _, ok := l.itablink[i]; ok {
return true
}
return false
}
// Returns the symbol content of the i-th symbol. i is global index.
func (l *Loader) Data(i Sym) []byte {
if l.isExternal(i) {
@ -491,7 +502,10 @@ func (l *Loader) Preload(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *
}
v := abiToVer(osym.ABI, localSymVersion)
dupok := osym.Dupok()
l.AddSym(name, v, istart+Sym(i), or, dupok, sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)])
added := l.AddSym(name, v, istart+Sym(i), or, dupok, sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)])
if added && strings.HasPrefix(name, "go.itablink.") {
l.itablink[istart+Sym(i)] = struct{}{}
}
}
// The caller expects us consuming all the data