1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
|
// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Removal of dead code and data.
package main
import "cmd/internal/goobj"
// dead removes unreachable code and data from the program.
// It is basically a mark-sweep garbage collection: traverse all the
// symbols reachable from the entry (startSymID) and then delete
// the rest.
func (p *Prog) dead() {
p.Dead = make(map[goobj.SymID]bool)
reachable := make(map[goobj.SymID]bool)
p.walkDead(p.startSym, reachable)
for sym := range p.Syms {
if !reachable[sym] {
delete(p.Syms, sym)
p.Dead[sym] = true
}
}
for sym := range p.Missing {
if !reachable[sym] {
delete(p.Missing, sym)
p.Dead[sym] = true
}
}
p.SymOrder = removeDead(p.SymOrder, reachable)
for _, pkg := range p.Packages {
pkg.Syms = removeDead(pkg.Syms, reachable)
}
}
// walkDead traverses the symbols reachable from sym, adding them to reachable.
// The caller has verified that reachable[sym] = false.
func (p *Prog) walkDead(sym goobj.SymID, reachable map[goobj.SymID]bool) {
reachable[sym] = true
s := p.Syms[sym]
if s == nil {
return
}
for i := range s.Reloc {
r := &s.Reloc[i]
if !reachable[r.Sym] {
p.walkDead(r.Sym, reachable)
}
}
if s.Func != nil {
for _, fdata := range s.Func.FuncData {
if fdata.Sym.Name != "" && !reachable[fdata.Sym] {
p.walkDead(fdata.Sym, reachable)
}
}
}
}
// removeDead removes unreachable (dead) symbols from syms,
// returning a shortened slice using the same underlying array.
func removeDead(syms []*Sym, reachable map[goobj.SymID]bool) []*Sym {
keep := syms[:0]
for _, sym := range syms {
if reachable[sym.SymID] {
keep = append(keep, sym)
}
}
return keep
}
|
