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go/test/escape_reflect.go
Kyle Xiao 7ba074fe43 reflect: remove calling mapiterkey, mapiterelem 
It makes use of the hiter structure which matches runtime.hiter's.

This change mainly improves the performance of Next method of MapIter.

goos: darwin
goarch: arm64
pkg: reflect
cpu: Apple M2
              │  ./old.txt  │              ./new.txt              │
              │   sec/op    │   sec/op     vs base                │
MapIterNext-8   61.95n ± 0%   54.95n ± 0%  -11.28% (p=0.000 n=10)

for the change of `test/escape_reflect.go`:
removing mapiterkey, mapiterelem would cause leaking MapIter content
when calling SetIterKey and SetIterValue,
and this may cause map bucket to be allocated on heap instead of stack.
Reproduce:
```
{
  m := map[int]int{1: 2} // escapes to heap after this change
  it := reflect.ValueOf(m).MapRange()
  it.Next()
  var k, v int
  reflect.ValueOf(&k).Elem().SetIterKey(it)
  reflect.ValueOf(&v).Elem().SetIterValue(it)
  println(k, v)
}
```
This CL would not introduce abi.NoEscape to fix this. It may need futher
optimization and tests on hiter field usage and its escape analysis.

Fixes #69416

Change-Id: Ibaa33bcf86228070b4a505b9512680791aa59f04
Reviewed-on: https://go-review.googlesource.com/c/go/+/612616
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
2024-09-18 20:57:20 +00:00

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// errorcheck -0 -m -l
// Copyright 2022 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.
// Test escape analysis for reflect Value operations.
package escape
import (
"reflect"
"unsafe"
)
var sink interface{}
func typ(x int) any {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Type()
}
func kind(x int) reflect.Kind {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Kind()
}
func int1(x int) int {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return int(v.Int())
}
func ptr(x *int) *int { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x)
return (*int)(v.UnsafePointer())
}
func bytes1(x []byte) byte { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Bytes()[0]
}
// Unfortunate: should only escape content. x (the interface storage) should not escape.
func bytes2(x []byte) []byte { // ERROR "leaking param: x$"
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Bytes()
}
func string1(x string) string { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.String()
}
func string2(x int) string {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.String()
}
// Unfortunate: should only escape to result.
func interface1(x any) any { // ERROR "leaking param: x$"
v := reflect.ValueOf(x)
return v.Interface()
}
func interface2(x int) any {
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Interface()
}
// Unfortunate: should not escape.
func interface3(x int) int {
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Interface().(int)
}
// Unfortunate: should only escape to result.
func interface4(x *int) any { // ERROR "leaking param: x$"
v := reflect.ValueOf(x)
return v.Interface()
}
func addr(x *int) reflect.Value { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x).Elem()
return v.Addr()
}
// functions returning pointer as uintptr have to escape.
func uintptr1(x *int) uintptr { // ERROR "leaking param: x$"
v := reflect.ValueOf(x)
return v.Pointer()
}
func unsafeaddr(x *int) uintptr { // ERROR "leaking param: x$"
v := reflect.ValueOf(x).Elem()
return v.UnsafeAddr()
}
func ifacedata(x any) [2]uintptr { // ERROR "moved to heap: x"
v := reflect.ValueOf(&x).Elem()
return v.InterfaceData()
}
func can(x int) bool {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.CanAddr() || v.CanInt() || v.CanSet() || v.CanInterface()
}
func is(x int) bool {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.IsValid() || v.IsNil() || v.IsZero()
}
func is2(x [2]int) bool {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.IsValid() || v.IsNil() || v.IsZero()
}
func is3(x struct{ a, b int }) bool {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.IsValid() || v.IsNil() || v.IsZero()
}
func overflow(x int) bool {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.OverflowInt(1 << 62)
}
func len1(x []int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Len()
}
func len2(x [3]int) int {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Len()
}
func len3(x string) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Len()
}
func len4(x map[int]int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x)
return v.Len()
}
func len5(x chan int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x)
return v.Len()
}
func cap1(x []int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Cap()
}
func cap2(x [3]int) int {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Cap()
}
func cap3(x chan int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x)
return v.Cap()
}
func setlen(x *[]int, n int) { // ERROR "x does not escape"
v := reflect.ValueOf(x).Elem()
v.SetLen(n)
}
func setcap(x *[]int, n int) { // ERROR "x does not escape"
v := reflect.ValueOf(x).Elem()
v.SetCap(n)
}
// Unfortunate: x doesn't need to escape to heap, just to result.
func slice1(x []byte) []byte { // ERROR "leaking param: x$"
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Slice(1, 2).Bytes()
}
// Unfortunate: x doesn't need to escape to heap, just to result.
func slice2(x string) string { // ERROR "leaking param: x$"
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Slice(1, 2).String()
}
func slice3(x [10]byte) []byte {
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Slice(1, 2).Bytes()
}
func elem1(x *int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x)
return int(v.Elem().Int())
}
func elem2(x *string) string { // ERROR "leaking param: x to result ~r0 level=1"
v := reflect.ValueOf(x)
return string(v.Elem().String())
}
type S struct {
A int
B *int
C string
}
func (S) M() {}
func field1(x S) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return int(v.Field(0).Int())
}
func field2(x S) string { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Field(2).String()
}
func numfield(x S) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.NumField()
}
func index1(x []int) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return int(v.Index(0).Int())
}
// Unfortunate: should only leak content (level=1)
func index2(x []string) string { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Index(0).String()
}
func index3(x [3]int) int {
v := reflect.ValueOf(x) // ERROR "x does not escape"
return int(v.Index(0).Int())
}
func index4(x [3]string) string { // ERROR "leaking param: x to result ~r0 level=0"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.Index(0).String()
}
func index5(x string) byte { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return byte(v.Index(0).Uint())
}
// Unfortunate: x (the interface storage) doesn't need to escape as the function takes a scalar arg.
func call1(f func(int), x int) { // ERROR "leaking param: f$"
fv := reflect.ValueOf(f)
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
fv.Call([]reflect.Value{v}) // ERROR "\[\]reflect\.Value{\.\.\.} does not escape"
}
func call2(f func(*int), x *int) { // ERROR "leaking param: f$" "leaking param: x$"
fv := reflect.ValueOf(f)
v := reflect.ValueOf(x)
fv.Call([]reflect.Value{v}) // ERROR "\[\]reflect.Value{\.\.\.} does not escape"
}
func method(x S) reflect.Value { // ERROR "leaking param: x$"
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Method(0)
}
func nummethod(x S) int { // ERROR "x does not escape"
v := reflect.ValueOf(x) // ERROR "x does not escape"
return v.NumMethod()
}
// Unfortunate: k doesn't need to escape.
func mapindex(m map[string]string, k string) string { // ERROR "m does not escape" "leaking param: k$"
mv := reflect.ValueOf(m)
kv := reflect.ValueOf(k) // ERROR "k escapes to heap"
return mv.MapIndex(kv).String()
}
func mapkeys(m map[string]string) []reflect.Value { // ERROR "m does not escape"
mv := reflect.ValueOf(m)
return mv.MapKeys()
}
func mapiter1(m map[string]string) *reflect.MapIter { // ERROR "leaking param: m$"
mv := reflect.ValueOf(m)
return mv.MapRange()
}
func mapiter2(m map[string]string) string { // ERROR "leaking param: m$"
mv := reflect.ValueOf(m)
it := mv.MapRange()
if it.Next() {
return it.Key().String()
}
return ""
}
func mapiter3(m map[string]string, it *reflect.MapIter) { // ERROR "leaking param: m$" "it does not escape"
mv := reflect.ValueOf(m)
it.Reset(mv)
}
func recv1(ch chan string) string { // ERROR "ch does not escape"
v := reflect.ValueOf(ch)
r, _ := v.Recv()
return r.String()
}
func recv2(ch chan string) string { // ERROR "ch does not escape"
v := reflect.ValueOf(ch)
r, _ := v.TryRecv()
return r.String()
}
// Unfortunate: x (the interface storage) doesn't need to escape.
func send1(ch chan string, x string) { // ERROR "ch does not escape" "leaking param: x$"
vc := reflect.ValueOf(ch)
vx := reflect.ValueOf(x) // ERROR "x escapes to heap"
vc.Send(vx)
}
// Unfortunate: x (the interface storage) doesn't need to escape.
func send2(ch chan string, x string) bool { // ERROR "ch does not escape" "leaking param: x$"
vc := reflect.ValueOf(ch)
vx := reflect.ValueOf(x) // ERROR "x escapes to heap"
return vc.TrySend(vx)
}
func close1(ch chan string) { // ERROR "ch does not escape"
v := reflect.ValueOf(ch)
v.Close()
}
func select1(ch chan string) string { // ERROR "leaking param: ch$"
v := reflect.ValueOf(ch)
cas := reflect.SelectCase{Dir: reflect.SelectRecv, Chan: v}
_, r, _ := reflect.Select([]reflect.SelectCase{cas}) // ERROR "\[\]reflect.SelectCase{...} does not escape"
return r.String()
}
// Unfortunate: x (the interface storage) doesn't need to escape.
func select2(ch chan string, x string) { // ERROR "leaking param: ch$" "leaking param: x$"
vc := reflect.ValueOf(ch)
vx := reflect.ValueOf(x) // ERROR "x escapes to heap"
cas := reflect.SelectCase{Dir: reflect.SelectSend, Chan: vc, Send: vx}
reflect.Select([]reflect.SelectCase{cas}) // ERROR "\[\]reflect.SelectCase{...} does not escape"
}
var (
intTyp = reflect.TypeOf(int(0)) // ERROR "0 does not escape"
uintTyp = reflect.TypeOf(uint(0)) // ERROR "uint\(0\) does not escape"
stringTyp = reflect.TypeOf(string("")) // ERROR ".. does not escape"
bytesTyp = reflect.TypeOf([]byte{}) // ERROR "\[\]byte{} does not escape"
)
// Unfortunate: should not escape.
func convert1(x int) uint {
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return uint(v.Convert(uintTyp).Uint())
}
// Unfortunate: should only escape content to result.
func convert2(x []byte) string { // ERROR "leaking param: x$"
v := reflect.ValueOf(x) // ERROR "x escapes to heap"
return v.Convert(stringTyp).String()
}
// Unfortunate: v doesn't need to leak, x (the interface storage) doesn't need to escape.
func set1(v reflect.Value, x int) { // ERROR "leaking param: v$"
vx := reflect.ValueOf(x) // ERROR "x escapes to heap"
v.Set(vx)
}
// Unfortunate: a can be stack allocated, x (the interface storage) doesn't need to escape.
func set2(x int) int64 {
var a int // ERROR "moved to heap: a"
v := reflect.ValueOf(&a).Elem()
vx := reflect.ValueOf(x) // ERROR "x escapes to heap"
v.Set(vx)
return v.Int()
}
func set3(v reflect.Value, x int) { // ERROR "v does not escape"
v.SetInt(int64(x))
}
func set4(x int) int {
var a int
v := reflect.ValueOf(&a).Elem() // a should not escape, no error printed
v.SetInt(int64(x))
return int(v.Int())
}
func set5(v reflect.Value, x string) { // ERROR "v does not escape" "leaking param: x$"
v.SetString(x)
}
func set6(v reflect.Value, x []byte) { // ERROR "v does not escape" "leaking param: x$"
v.SetBytes(x)
}
func set7(v reflect.Value, x unsafe.Pointer) { // ERROR "v does not escape" "leaking param: x$"
v.SetPointer(x)
}
func setmapindex(m map[string]string, k, e string) { // ERROR "m does not escape" "leaking param: k$" "leaking param: e$"
mv := reflect.ValueOf(m)
kv := reflect.ValueOf(k) // ERROR "k escapes to heap"
ev := reflect.ValueOf(e) // ERROR "e escapes to heap"
mv.SetMapIndex(kv, ev)
}
// Unfortunate: k doesn't need to escape.
func mapdelete(m map[string]string, k string) { // ERROR "m does not escape" "leaking param: k$"
mv := reflect.ValueOf(m)
kv := reflect.ValueOf(k) // ERROR "k escapes to heap"
mv.SetMapIndex(kv, reflect.Value{})
}
// Unfortunate: v doesn't need to leak.
func setiterkey1(v reflect.Value, it *reflect.MapIter) { // ERROR "leaking param: v$" "leaking param content: it$"
v.SetIterKey(it)
}
// Unfortunate: v doesn't need to leak.
func setiterkey2(v reflect.Value, m map[string]string) { // ERROR "leaking param: v$" "leaking param: m$"
it := reflect.ValueOf(m).MapRange()
v.SetIterKey(it)
}
// Unfortunate: v doesn't need to leak.
func setitervalue1(v reflect.Value, it *reflect.MapIter) { // ERROR "leaking param: v$" "leaking param content: it$"
v.SetIterValue(it)
}
// Unfortunate: v doesn't need to leak.
func setitervalue2(v reflect.Value, m map[string]string) { // ERROR "leaking param: v$" "leaking param: m$"
it := reflect.ValueOf(m).MapRange()
v.SetIterValue(it)
}
// Unfortunate: s doesn't need escape, only leak to result.
// And x (interface storage) doesn't need to escape.
func append1(s []int, x int) []int { // ERROR "leaking param: s$"
sv := reflect.ValueOf(s) // ERROR "s escapes to heap"
xv := reflect.ValueOf(x) // ERROR "x escapes to heap"
rv := reflect.Append(sv, xv) // ERROR "... argument does not escape"
return rv.Interface().([]int)
}
// Unfortunate: s doesn't need escape, only leak to result.
func append2(s, x []int) []int { // ERROR "leaking param: s$" "x does not escape"
sv := reflect.ValueOf(s) // ERROR "s escapes to heap"
xv := reflect.ValueOf(x) // ERROR "x does not escape"
rv := reflect.AppendSlice(sv, xv)
return rv.Interface().([]int)
}
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