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reflect: tweak logic for 'case Array' in IsZero

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For 'case Array' in IsZero, check 'v.flag&flagIndir == 0' in the
first place, rename 'array' to 'typ' for consistency, and remove
stale comment.

Add line breaks for long sentence in isZero.

Change-Id: Id06d01fd61eefd205bf4626e6b920ae82b459455
GitHub-Last-Rev: 7225ca3f7b
GitHub-Pull-Request: golang/go#64270
Reviewed-on: https://go-review.googlesource.com/c/go/+/543656
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Jes Cok <xigua67damn@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Jes Cok 2023-11-20 13:37:33 +00:00 committed by Gopher Robot
parent dc094f9c96
commit 515f3c0da6
1 changed files with 18 additions and 12 deletions
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26
src/reflect/value.go
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@ -1598,24 +1598,23 @@ func (v Value) IsZero() bool {
case Complex64, Complex128: case Complex64, Complex128:
return v.Complex() == 0 return v.Complex() == 0
case Array: case Array:
array := (*abi.ArrayType)(unsafe.Pointer(v.typ()))
// Avoid performance degradation of small benchmarks.
// If the type is comparable, then compare directly with zero.
if array.Equal != nil && array.Size() <= maxZero {
if v.flag&flagIndir == 0 { if v.flag&flagIndir == 0 {
return v.ptr == nil return v.ptr == nil
} }
typ := (*abi.ArrayType)(unsafe.Pointer(v.typ()))
// If the type is comparable, then compare directly with zero.
if typ.Equal != nil && typ.Size() <= maxZero {
// v.ptr doesn't escape, as Equal functions are compiler generated // v.ptr doesn't escape, as Equal functions are compiler generated
// and never escape. The escape analysis doesn't know, as it is a // and never escape. The escape analysis doesn't know, as it is a
// function pointer call. // function pointer call.
return array.Equal(noescape(v.ptr), unsafe.Pointer(&zeroVal[0])) return typ.Equal(noescape(v.ptr), unsafe.Pointer(&zeroVal[0]))
} }
if array.TFlag&abi.TFlagRegularMemory != 0 { if typ.TFlag&abi.TFlagRegularMemory != 0 {
// For some types where the zero value is a value where all bits of this type are 0 // For some types where the zero value is a value where all bits of this type are 0
// optimize it. // optimize it.
return isZero(unsafe.Slice(((*byte)(v.ptr)), array.Size())) return isZero(unsafe.Slice(((*byte)(v.ptr)), typ.Size()))
} }
n := int(array.Len) n := int(typ.Len)
for i := 0; i < n; i++ { for i := 0; i < n; i++ {
if !v.Index(i).IsZero() { if !v.Index(i).IsZero() {
return false return false
@ -1663,7 +1662,7 @@ func isZero(b []byte) bool {
return true return true
} }
const n = 32 const n = 32
// Align memory addresses to 8 bytes // Align memory addresses to 8 bytes.
for uintptr(unsafe.Pointer(&b[0]))%8 != 0 { for uintptr(unsafe.Pointer(&b[0]))%8 != 0 {
if b[0] != 0 { if b[0] != 0 {
return false return false
@ -1690,7 +1689,14 @@ func isZero(b []byte) bool {
w = w[1:] w = w[1:]
} }
for len(w) >= n { for len(w) >= n {
if w[0] != 0 || w[1] != 0 || w[2] != 0 || w[3] != 0 || w[4] != 0 || w[5] != 0 || w[6] != 0 || w[7] != 0 || w[8] != 0 || w[9] != 0 || w[10] != 0 || w[11] != 0 || w[12] != 0 || w[13] != 0 || w[14] != 0 || w[15] != 0 || w[16] != 0 || w[17] != 0 || w[18] != 0 || w[19] != 0 || w[20] != 0 || w[21] != 0 || w[22] != 0 || w[23] != 0 || w[24] != 0 || w[25] != 0 || w[26] != 0 || w[27] != 0 || w[28] != 0 || w[29] != 0 || w[30] != 0 || w[31] != 0 { if w[0] != 0 || w[1] != 0 || w[2] != 0 || w[3] != 0 ||
w[4] != 0 || w[5] != 0 || w[6] != 0 || w[7] != 0 ||
w[8] != 0 || w[9] != 0 || w[10] != 0 || w[11] != 0 ||
w[12] != 0 || w[13] != 0 || w[14] != 0 || w[15] != 0 ||
w[16] != 0 || w[17] != 0 || w[18] != 0 || w[19] != 0 ||
w[20] != 0 || w[21] != 0 || w[22] != 0 || w[23] != 0 ||
w[24] != 0 || w[25] != 0 || w[26] != 0 || w[27] != 0 ||
w[28] != 0 || w[29] != 0 || w[30] != 0 || w[31] != 0 {
return false return false
} }
w = w[n:] w = w[n:]