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[dev.link] cmd/link: reuse slice memory in deadcode pass

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Reuse slice memory in the deadcode pass, reduce allocations.

Linking cmd/compile,

name           old alloc/op   new alloc/op   delta
Deadcode_GC      2.10MB ± 0%    1.41MB ± 0%  -32.61%  (p=0.008 n=5+5)

name           old allocs/op  new allocs/op  delta
Deadcode_GC       8.46k ± 0%     5.55k ± 0%  -34.45%  (p=0.008 n=5+5)

Change-Id: Ib9ba0928d68a65879007218697712b53acd3c5c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/236566
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-06-04 12:01:53 -04:00
parent 7179e426e2
commit 78b96db04e
1 changed files with 8 additions and 2 deletions
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10
src/cmd/link/internal/ld/deadcode.go
View file

@ -24,6 +24,8 @@ type deadcodePass struct {
ifaceMethod map[methodsig]bool // methods declared in reached interfaces
markableMethods []methodref // methods of reached types
reflectSeen bool // whether we have seen a reflect method call
methodsigstmp []methodsig // scratch buffer for decoding method signatures
}
func (d *deadcodePass) init() {
@ -92,6 +94,7 @@ func (d *deadcodePass) init() {
}
func (d *deadcodePass) flood() {
var methods []methodref
for !d.wq.empty() {
symIdx := d.wq.pop()
@ -112,7 +115,7 @@ func (d *deadcodePass) flood() {
}
}
var methods []methodref
methods = methods[:0]
for i := 0; i < relocs.Count(); i++ {
r := relocs.At2(i)
t := r.Type()
@ -330,7 +333,10 @@ func (m methodref) isExported() bool {
//
// Conveniently this is the layout of both runtime.method and runtime.imethod.
func (d *deadcodePass) decodeMethodSig(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, off, size, count int) []methodsig {
var methods = make([]methodsig, count)
if cap(d.methodsigstmp) < count {
d.methodsigstmp = append(d.methodsigstmp[:0], make([]methodsig, count)...)
}
var methods = d.methodsigstmp[:count]
for i := 0; i < count; i++ {
methods[i].name = decodetypeName(ldr, symIdx, relocs, off)
methods[i].typ = decodeRelocSym(ldr, symIdx, relocs, int32(off+4))