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util/deephash: delete slow path (#5423)

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Every implementation of typeHasherFunc always returns true,
which implies that the slow path is no longer executed.
Delete it.

h.hashValueWithType(v, ti, ...) is deleted as it is equivalent to:
	ti.hasher()(h, v)

h.hashValue(v, ...) is deleted as it is equivalent to:
	ti := getTypeInfo(v.Type())
	ti.hasher()(h, v)

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai 2022-08-26 17:46:22 -07:00 committed by GitHub
parent 3d328b82ee
commit 531ccca648
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 49 additions and 229 deletions
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265
util/deephash/deephash.go
View File

@ -24,7 +24,6 @@
"crypto/sha256"
"encoding/binary"
"encoding/hex"
"fmt"
"math"
"net/netip"
"reflect"
@ -151,7 +150,8 @@ func Hash(v any) (s Sum) {
// the initial reflect.ValueOf from an interface value effectively strips
// the interface box off so we have to do it at the top level by hand.
h.hashType(va.Type())
h.hashValue(va, false)
ti := getTypeInfo(va.Type())
ti.hasher()(h, va)
}
return h.sum()
}
@ -180,12 +180,12 @@ func HasherForType[T any]() func(T) Sum {
if rv.Kind() == reflect.Pointer && !rv.IsNil() {
va := addressableValue{rv.Elem()} // dereferenced pointer is always addressable
h.hashType(va.Type())
h.hashValueWithType(va, tiElem, false)
tiElem.hasher()(h, va)
} else {
va := newAddressableValue(rv.Type())
va.Set(rv)
h.hashType(va.Type())
h.hashValueWithType(va, ti, false)
ti.hasher()(h, va)
}
}
return h.sum()
@ -202,14 +202,6 @@ func Update(last *Sum, v any) (changed bool) {
return changed
}
var appenderToType = reflect.TypeOf((*appenderTo)(nil)).Elem()
type appenderTo interface {
AppendTo([]byte) []byte
}
var uint8Type = reflect.TypeOf(byte(0))
// typeInfo describes properties of a type.
//
// A non-nil typeInfo is populated into the typeHasher map
@ -218,7 +210,6 @@ type appenderTo interface {
// This is used for recursive types.
type typeInfo struct {
rtype reflect.Type
canMemHash bool
isRecursive bool
// elemTypeInfo is the element type's typeInfo.
@ -233,8 +224,7 @@ type typeInfo struct {
hashFuncLazy typeHasherFunc // nil until created
}
// returns ok if it was handled; else slow path runs
type typeHasherFunc func(h *hasher, v addressableValue) (ok bool)
type typeHasherFunc func(h *hasher, v addressableValue)
var typeInfoMap sync.Map // map[reflect.Type]*typeInfo
var typeInfoMapPopulate sync.Mutex // just for adding to typeInfoMap
@ -248,53 +238,44 @@ func (ti *typeInfo) buildHashFuncOnce() {
ti.hashFuncLazy = genTypeHasher(ti)
}
func (h *hasher) hashBoolv(v addressableValue) bool {
func (h *hasher) hashBoolv(v addressableValue) {
var b byte
if v.Bool() {
b = 1
}
h.HashUint8(b)
return true
}
func (h *hasher) hashUint8v(v addressableValue) bool {
func (h *hasher) hashUint8v(v addressableValue) {
h.HashUint8(uint8(v.Uint()))
return true
}
func (h *hasher) hashInt8v(v addressableValue) bool {
func (h *hasher) hashInt8v(v addressableValue) {
h.HashUint8(uint8(v.Int()))
return true
}
func (h *hasher) hashUint16v(v addressableValue) bool {
func (h *hasher) hashUint16v(v addressableValue) {
h.HashUint16(uint16(v.Uint()))
return true
}
func (h *hasher) hashInt16v(v addressableValue) bool {
func (h *hasher) hashInt16v(v addressableValue) {
h.HashUint16(uint16(v.Int()))
return true
}
func (h *hasher) hashUint32v(v addressableValue) bool {
func (h *hasher) hashUint32v(v addressableValue) {
h.HashUint32(uint32(v.Uint()))
return true
}
func (h *hasher) hashInt32v(v addressableValue) bool {
func (h *hasher) hashInt32v(v addressableValue) {
h.HashUint32(uint32(v.Int()))
return true
}
func (h *hasher) hashUint64v(v addressableValue) bool {
func (h *hasher) hashUint64v(v addressableValue) {
h.HashUint64(v.Uint())
return true
}
func (h *hasher) hashInt64v(v addressableValue) bool {
func (h *hasher) hashInt64v(v addressableValue) {
h.HashUint64(uint64(v.Int()))
return true
}
// fieldInfo describes a struct field.
@ -349,7 +330,7 @@ type structHasher struct {
fields []fieldInfo
}
func (sh structHasher) hash(h *hasher, v addressableValue) bool {
func (sh structHasher) hash(h *hasher, v addressableValue) {
base := v.Addr().UnsafePointer()
for _, f := range sh.fields {
if f.canMemHash {
@ -357,25 +338,21 @@ func (sh structHasher) hash(h *hasher, v addressableValue) bool {
continue
}
va := addressableValue{v.Field(f.index)} // field is addressable if parent struct is addressable
if !f.typeInfo.hasher()(h, va) {
return false
}
f.typeInfo.hasher()(h, va)
}
return true
}
// genHashPtrToMemoryRange returns a hasher where the reflect.Value is a Ptr to
// the provided eleType.
func genHashPtrToMemoryRange(eleType reflect.Type) typeHasherFunc {
size := eleType.Size()
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
if v.IsNil() {
h.HashUint8(0) // indicates nil
} else {
h.HashUint8(1) // indicates visiting a pointer
h.HashBytes(unsafe.Slice((*byte)(v.UnsafePointer()), size))
}
return true
}
}
@ -431,24 +408,23 @@ func genTypeHasher(ti *typeInfo) typeHasherFunc {
return genHashStructFields(t)
}
case reflect.Map:
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
if v.IsNil() {
h.HashUint8(0) // indicates nil
return true
return
}
if ti.isRecursive {
ptr := pointerOf(v)
if idx, ok := h.visitStack.seen(ptr); ok {
h.HashUint8(2) // indicates cycle
h.HashUint64(uint64(idx))
return true
return
}
h.visitStack.push(ptr)
defer h.visitStack.pop(ptr)
}
h.HashUint8(1) // indicates visiting a map
h.hashMap(v, ti, ti.isRecursive)
return true
}
case reflect.Pointer:
et := t.Elem()
@ -456,78 +432,72 @@ func genTypeHasher(ti *typeInfo) typeHasherFunc {
return genHashPtrToMemoryRange(et)
}
eti := getTypeInfo(et)
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
if v.IsNil() {
h.HashUint8(0) // indicates nil
return true
return
}
if ti.isRecursive {
ptr := pointerOf(v)
if idx, ok := h.visitStack.seen(ptr); ok {
h.HashUint8(2) // indicates cycle
h.HashUint64(uint64(idx))
return true
return
}
h.visitStack.push(ptr)
defer h.visitStack.pop(ptr)
}
h.HashUint8(1) // indicates visiting a pointer
va := addressableValue{v.Elem()} // dereferenced pointer is always addressable
return eti.hasher()(h, va)
eti.hasher()(h, va)
}
case reflect.Interface:
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
if v.IsNil() {
h.HashUint8(0) // indicates nil
return true
return
}
va := newAddressableValue(v.Elem().Type())
va.Set(v.Elem())
h.HashUint8(1) // indicates visiting interface value
h.hashType(va.Type())
h.hashValue(va, true)
return true
ti := getTypeInfo(va.Type())
ti.hasher()(h, va)
}
default: // Func, Chan, UnsafePointer
return noopHasherFunc
}
}
// hashString hashes v, of kind String.
func (h *hasher) hashString(v addressableValue) bool {
func (h *hasher) hashString(v addressableValue) {
s := v.String()
h.HashUint64(uint64(len(s)))
h.HashString(s)
return true
}
func (h *hasher) hashFloat32v(v addressableValue) bool {
func (h *hasher) hashFloat32v(v addressableValue) {
h.HashUint32(math.Float32bits(float32(v.Float())))
return true
}
func (h *hasher) hashFloat64v(v addressableValue) bool {
func (h *hasher) hashFloat64v(v addressableValue) {
h.HashUint64(math.Float64bits(v.Float()))
return true
}
func (h *hasher) hashComplex64v(v addressableValue) bool {
func (h *hasher) hashComplex64v(v addressableValue) {
c := complex64(v.Complex())
h.HashUint32(math.Float32bits(real(c)))
h.HashUint32(math.Float32bits(imag(c)))
return true
}
func (h *hasher) hashComplex128v(v addressableValue) bool {
func (h *hasher) hashComplex128v(v addressableValue) {
c := v.Complex()
h.HashUint64(math.Float64bits(real(c)))
h.HashUint64(math.Float64bits(imag(c)))
return true
}
// hashTimev hashes v, of kind time.Time.
func (h *hasher) hashTimev(v addressableValue) bool {
func (h *hasher) hashTimev(v addressableValue) {
// Include the zone offset (but not the name) to keep
// Hash(t1) == Hash(t2) being semantically equivalent to
// t1.Format(time.RFC3339Nano) == t2.Format(time.RFC3339Nano).
@ -536,11 +506,10 @@ func (h *hasher) hashTimev(v addressableValue) bool {
h.HashUint64(uint64(t.Unix()))
h.HashUint32(uint32(t.Nanosecond()))
h.HashUint32(uint32(offset))
return true
}
// hashAddrv hashes v, of type netip.Addr.
func (h *hasher) hashAddrv(v addressableValue) bool {
func (h *hasher) hashAddrv(v addressableValue) {
// The formatting of netip.Addr covers the
// IP version, the address, and the optional zone name (for v6).
// This is equivalent to a1.MarshalBinary() == a2.MarshalBinary().
@ -560,40 +529,34 @@ func (h *hasher) hashAddrv(v addressableValue) bool {
h.HashUint64(binary.LittleEndian.Uint64(b[8:]))
h.HashString(z)
}
return true
}
// hashSliceMem hashes v, of kind Slice, with a memhash-able element type.
func (h *hasher) hashSliceMem(v addressableValue) bool {
func (h *hasher) hashSliceMem(v addressableValue) {
vLen := v.Len()
h.HashUint64(uint64(vLen))
if vLen == 0 {
return true
return
}
h.HashBytes(unsafe.Slice((*byte)(v.UnsafePointer()), v.Type().Elem().Size()*uintptr(vLen)))
return true
}
func genHashArrayMem(n int, arraySize uintptr, efu *typeInfo) typeHasherFunc {
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
h.HashBytes(unsafe.Slice((*byte)(v.Addr().UnsafePointer()), arraySize))
return true
}
}
func genHashArrayElements(n int, eti *typeInfo) typeHasherFunc {
return func(h *hasher, v addressableValue) bool {
return func(h *hasher, v addressableValue) {
for i := 0; i < n; i++ {
va := addressableValue{v.Index(i)} // element is addressable if parent array is addressable
if !eti.hasher()(h, va) {
return false
}
eti.hasher()(h, va)
}
return true
}
}
func noopHasherFunc(h *hasher, v addressableValue) bool { return true }
func noopHasherFunc(h *hasher, v addressableValue) {}
func genHashArray(t reflect.Type, eti *typeInfo) typeHasherFunc {
if t.Size() == 0 {
@ -615,16 +578,13 @@ type sliceElementHasher struct {
eti *typeInfo
}
func (seh sliceElementHasher) hash(h *hasher, v addressableValue) bool {
func (seh sliceElementHasher) hash(h *hasher, v addressableValue) {
vLen := v.Len()
h.HashUint64(uint64(vLen))
for i := 0; i < vLen; i++ {
va := addressableValue{v.Index(i)} // slice elements are always addressable
if !seh.eti.hasher()(h, va) {
return false
}
seh.eti.hasher()(h, va)
}
return true
}
func getTypeInfo(t reflect.Type) *typeInfo {
@ -651,7 +611,6 @@ func getTypeInfoLocked(t reflect.Type, incomplete map[reflect.Type]*typeInfo) *t
ti := &typeInfo{
rtype: t,
isRecursive: typeIsRecursive(t),
canMemHash: typeIsMemHashable(t),
}
incomplete[t] = ti
@ -666,140 +625,6 @@ func getTypeInfoLocked(t reflect.Type, incomplete map[reflect.Type]*typeInfo) *t
return ti
}
func (h *hasher) hashValue(v addressableValue, forceCycleChecking bool) {
if !v.IsValid() {
return
}
ti := getTypeInfo(v.Type())
h.hashValueWithType(v, ti, forceCycleChecking)
}
func (h *hasher) hashValueWithType(v addressableValue, ti *typeInfo, forceCycleChecking bool) {
doCheckCycles := forceCycleChecking || ti.isRecursive
if ti.hasher()(h, v) {
return
}
// Generic handling.
switch v.Kind() {
default:
panic(fmt.Sprintf("unhandled kind %v for type %v", v.Kind(), v.Type()))
case reflect.Ptr:
if v.IsNil() {
h.HashUint8(0) // indicates nil
return
}
if doCheckCycles {
ptr := pointerOf(v)
if idx, ok := h.visitStack.seen(ptr); ok {
h.HashUint8(2) // indicates cycle
h.HashUint64(uint64(idx))
return
}
h.visitStack.push(ptr)
defer h.visitStack.pop(ptr)
}
h.HashUint8(1) // indicates visiting a pointer
va := addressableValue{v.Elem()} // dereferenced pointer is always addressable
h.hashValueWithType(va, ti.elemTypeInfo, doCheckCycles)
case reflect.Struct:
for i, n := 0, v.NumField(); i < n; i++ {
va := addressableValue{v.Field(i)} // field is addressable if parent struct is addressable
h.hashValue(va, doCheckCycles)
}
case reflect.Slice, reflect.Array:
vLen := v.Len()
if v.Kind() == reflect.Slice {
h.HashUint64(uint64(vLen))
}
if v.Type().Elem() == uint8Type && v.CanInterface() {
if vLen > 0 && vLen <= scratchSize {
// If it fits in scratch, avoid the Interface allocation.
// It seems tempting to do this for all sizes, doing
// scratchSize bytes at a time, but reflect.Slice seems
// to allocate, so it's not a win.
n := reflect.Copy(reflect.ValueOf(&h.scratch).Elem(), v.Value)
h.HashBytes(h.scratch[:n])
return
}
fmt.Fprintf(h, "%s", v.Interface())
return
}
for i := 0; i < vLen; i++ {
// TODO(dsnet): Perform cycle detection for slices,
// which is functionally a list of pointers.
// See https://github.com/google/go-cmp/blob/402949e8139bb890c71a707b6faf6dd05c92f4e5/cmp/compare.go#L438-L450
va := addressableValue{v.Index(i)} // slice elements are always addressable
h.hashValueWithType(va, ti.elemTypeInfo, doCheckCycles)
}
case reflect.Interface:
if v.IsNil() {
h.HashUint8(0) // indicates nil
return
}
// TODO: Use a valueCache here?
va := newAddressableValue(v.Elem().Type())
va.Set(v.Elem())
h.HashUint8(1) // indicates visiting interface value
h.hashType(va.Type())
h.hashValue(va, doCheckCycles)
case reflect.Map:
// Check for cycle.
if doCheckCycles {
ptr := pointerOf(v)
if idx, ok := h.visitStack.seen(ptr); ok {
h.HashUint8(2) // indicates cycle
h.HashUint64(uint64(idx))
return
}
h.visitStack.push(ptr)
defer h.visitStack.pop(ptr)
}
h.HashUint8(1) // indicates visiting a map
h.hashMap(v, ti, doCheckCycles)
case reflect.String:
s := v.String()
h.HashUint64(uint64(len(s)))
h.HashString(s)
case reflect.Bool:
if v.Bool() {
h.HashUint8(1)
} else {
h.HashUint8(0)
}
case reflect.Int8:
h.HashUint8(uint8(v.Int()))
case reflect.Int16:
h.HashUint16(uint16(v.Int()))
case reflect.Int32:
h.HashUint32(uint32(v.Int()))
case reflect.Int64, reflect.Int:
h.HashUint64(uint64(v.Int()))
case reflect.Uint8:
h.HashUint8(uint8(v.Uint()))
case reflect.Uint16:
h.HashUint16(uint16(v.Uint()))
case reflect.Uint32:
h.HashUint32(uint32(v.Uint()))
case reflect.Uint64, reflect.Uint, reflect.Uintptr:
h.HashUint64(uint64(v.Uint()))
case reflect.Float32:
h.HashUint32(math.Float32bits(float32(v.Float())))
case reflect.Float64:
h.HashUint64(math.Float64bits(float64(v.Float())))
case reflect.Complex64:
h.HashUint32(math.Float32bits(real(complex64(v.Complex()))))
h.HashUint32(math.Float32bits(imag(complex64(v.Complex()))))
case reflect.Complex128:
h.HashUint64(math.Float64bits(real(complex128(v.Complex()))))
h.HashUint64(math.Float64bits(imag(complex128(v.Complex()))))
}
}
type mapHasher struct {
h hasher
valKey, valElem valueCache // re-usable values for map iteration
@ -843,8 +668,8 @@ func (h *hasher) hashMap(v addressableValue, ti *typeInfo, checkCycles bool) {
k.SetIterKey(iter)
e.SetIterValue(iter)
mh.h.Reset()
mh.h.hashValueWithType(k, ti.keyTypeInfo, checkCycles)
mh.h.hashValueWithType(e, ti.elemTypeInfo, checkCycles)
ti.keyTypeInfo.hasher()(&mh.h, k)
ti.elemTypeInfo.hasher()(&mh.h, e)
sum.xor(mh.h.sum())
}
h.HashBytes(append(h.scratch[:0], sum.sum[:]...)) // append into scratch to avoid heap allocation

13
util/deephash/deephash_test.go
View File

@ -361,7 +361,6 @@ func TestGetTypeHasher(t *testing.T) {
tests := []struct {
name string
val any
want bool // set true automatically if out != ""
out string
out32 string // overwrites out if 32-bit
}{
@ -571,17 +570,11 @@ func TestGetTypeHasher(t *testing.T) {
hb := &hashBuffer{Hash: sha256.New()}
h := new(hasher)
h.Block512.Hash = hb
got := fn(h, va)
fn(h, va)
const ptrSize = 32 << uintptr(^uintptr(0)>>63)
if tt.out32 != "" && ptrSize == 32 {
tt.out = tt.out32
}
if tt.out != "" {
tt.want = true
}
if got != tt.want {
t.Fatalf("func returned %v; want %v", got, tt.want)
}
h.sum()
if got := string(hb.B); got != tt.out {
t.Fatalf("got %q; want %q", got, tt.out)
@ -688,7 +681,9 @@ type T struct {
hb := &hashBuffer{Hash: sha256.New()}
h := new(hasher)
h.Block512.Hash = hb
h.hashValue(addressableValue{reflect.ValueOf(&x).Elem()}, false)
v := addressableValue{reflect.ValueOf(&x).Elem()}
ti := getTypeInfo(v.Type())
ti.hasher()(h, v)
h.sum()
const want = "\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x1f"
if got := hb.B; string(got) != want {