[dev.link] cmd/link: reuse slice memory in deadcode pass
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>
diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index 5aad748..d59b1f2 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -24,6 +24,8 @@
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) flood() {
+ var methods []methodref
for !d.wq.empty() {
symIdx := d.wq.pop()
@@ -112,7 +115,7 @@
}
}
- var methods []methodref
+ methods = methods[:0]
for i := 0; i < relocs.Count(); i++ {
r := relocs.At2(i)
t := r.Type()
@@ -330,7 +333,10 @@
//
// 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))
