bytes, internal/bytealg: simplify Equal
The compiler has advanced enough that it is cheaper
to convert to strings than to go through the assembly
trampolines to call runtime.memequal.
Simplify Equal accordingly, and cull dead code from bytealg.
While we're here, simplify Equal's documentation.
Fixes #31587
Change-Id: Ie721d33f9a6cbd86b1d873398b20e7882c2c63e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/173323
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/bytes/bytes.go b/src/bytes/bytes.go
index 22aeded..9d58658 100644
--- a/src/bytes/bytes.go
+++ b/src/bytes/bytes.go
@@ -12,23 +12,12 @@
"unicode/utf8"
)
-// Equal returns a boolean reporting whether a and b
+// Equal reports whether a and b
// are the same length and contain the same bytes.
// A nil argument is equivalent to an empty slice.
func Equal(a, b []byte) bool {
- return bytealg.Equal(a, b)
-}
-
-func equalPortable(a, b []byte) bool {
- if len(a) != len(b) {
- return false
- }
- for i, c := range a {
- if c != b[i] {
- return false
- }
- }
- return true
+ // Neither cmd/compile nor gccgo allocates for these string conversions.
+ return string(a) == string(b)
}
// Compare returns an integer comparing two byte slices lexicographically.
diff --git a/src/bytes/bytes_test.go b/src/bytes/bytes_test.go
index 340810f..4c50755 100644
--- a/src/bytes/bytes_test.go
+++ b/src/bytes/bytes_test.go
@@ -51,15 +51,17 @@
}
func TestEqual(t *testing.T) {
- for _, tt := range compareTests {
- eql := Equal(tt.a, tt.b)
- if eql != (tt.i == 0) {
- t.Errorf(`Equal(%q, %q) = %v`, tt.a, tt.b, eql)
+ // Run the tests and check for allocation at the same time.
+ allocs := testing.AllocsPerRun(10, func() {
+ for _, tt := range compareTests {
+ eql := Equal(tt.a, tt.b)
+ if eql != (tt.i == 0) {
+ t.Errorf(`Equal(%q, %q) = %v`, tt.a, tt.b, eql)
+ }
}
- eql = EqualPortable(tt.a, tt.b)
- if eql != (tt.i == 0) {
- t.Errorf(`EqualPortable(%q, %q) = %v`, tt.a, tt.b, eql)
- }
+ })
+ if allocs > 0 {
+ t.Errorf("Equal allocated %v times", allocs)
}
}
@@ -572,11 +574,6 @@
benchBytes(b, sizes, bmEqual(Equal))
}
-func BenchmarkEqualPort(b *testing.B) {
- sizes := []int{1, 6, 32, 4 << 10, 4 << 20, 64 << 20}
- benchBytes(b, sizes, bmEqual(EqualPortable))
-}
-
func bmEqual(equal func([]byte, []byte) bool) func(b *testing.B, n int) {
return func(b *testing.B, n int) {
if len(bmbuf) < 2*n {
diff --git a/src/bytes/export_test.go b/src/bytes/export_test.go
index f61523e..b65428d 100644
--- a/src/bytes/export_test.go
+++ b/src/bytes/export_test.go
@@ -6,4 +6,3 @@
// Export func for testing
var IndexBytePortable = indexBytePortable
-var EqualPortable = equalPortable
diff --git a/src/cmd/vet/all/whitelist/arm.txt b/src/cmd/vet/all/whitelist/arm.txt
index abcb38b..81a1f18 100644
--- a/src/cmd/vet/all/whitelist/arm.txt
+++ b/src/cmd/vet/all/whitelist/arm.txt
@@ -12,4 +12,3 @@
runtime/tls_arm.s: [arm] _initcgo: function _initcgo missing Go declaration
runtime/internal/atomic/asm_arm.s: [arm] cas: function cas missing Go declaration
-internal/bytealg/equal_arm.s: [arm] Equal: invalid MOVW of ret+24(FP); bool is 1-byte value
diff --git a/src/internal/bytealg/equal_386.s b/src/internal/bytealg/equal_386.s
index ad7da0e..8723363 100644
--- a/src/internal/bytealg/equal_386.s
+++ b/src/internal/bytealg/equal_386.s
@@ -5,24 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT,$0-25
- MOVL a_len+4(FP), BX
- MOVL b_len+16(FP), CX
- CMPL BX, CX
- JNE neq
- MOVL a_base+0(FP), SI
- MOVL b_base+12(FP), DI
- CMPL SI, DI
- JEQ eq
- LEAL ret+24(FP), AX
- JMP memeqbody<>(SB)
-neq:
- MOVB $0, ret+24(FP)
- RET
-eq:
- MOVB $1, ret+24(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT,$0-13
MOVL a+0(FP), SI
diff --git a/src/internal/bytealg/equal_amd64.s b/src/internal/bytealg/equal_amd64.s
index fa82589..c816409 100644
--- a/src/internal/bytealg/equal_amd64.s
+++ b/src/internal/bytealg/equal_amd64.s
@@ -5,24 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT,$0-49
- MOVQ a_len+8(FP), BX
- MOVQ b_len+32(FP), CX
- CMPQ BX, CX
- JNE neq
- MOVQ a_base+0(FP), SI
- MOVQ b_base+24(FP), DI
- CMPQ SI, DI
- JEQ eq
- LEAQ ret+48(FP), AX
- JMP memeqbody<>(SB)
-neq:
- MOVB $0, ret+48(FP)
- RET
-eq:
- MOVB $1, ret+48(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT,$0-25
MOVQ a+0(FP), SI
diff --git a/src/internal/bytealg/equal_amd64p32.s b/src/internal/bytealg/equal_amd64p32.s
index 00d5c0a..cd369c6 100644
--- a/src/internal/bytealg/equal_amd64p32.s
+++ b/src/internal/bytealg/equal_amd64p32.s
@@ -5,25 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT,$0-25
- MOVL a_len+4(FP), BX
- MOVL b_len+16(FP), CX
- CMPL BX, CX
- JNE neq
- MOVL a_base+0(FP), SI
- MOVL b_base+12(FP), DI
- CMPL SI, DI
- JEQ eq
- CALL memeqbody<>(SB)
- MOVB AX, ret+24(FP)
- RET
-neq:
- MOVB $0, ret+24(FP)
- RET
-eq:
- MOVB $1, ret+24(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT,$0-17
MOVL a+0(FP), SI
diff --git a/src/internal/bytealg/equal_arm.s b/src/internal/bytealg/equal_arm.s
index b8f2b69..a6c4369 100644
--- a/src/internal/bytealg/equal_arm.s
+++ b/src/internal/bytealg/equal_arm.s
@@ -5,27 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT,$0-25
- MOVW a_len+4(FP), R1
- MOVW b_len+16(FP), R3
- CMP R1, R3 // unequal lengths are not equal
- B.NE notequal
- CMP $0, R1 // short path to handle 0-byte case
- B.EQ equal
-
- MOVW a_base+0(FP), R0
- MOVW b_base+12(FP), R2
- MOVW $ret+24(FP), R7
- B memeqbody<>(SB)
-equal:
- MOVW $1, R0
- MOVB R0, ret+24(FP)
- RET
-notequal:
- MOVW $0, R0
- MOVBU R0, ret+24(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-13
MOVW a+0(FP), R0
diff --git a/src/internal/bytealg/equal_arm64.s b/src/internal/bytealg/equal_arm64.s
index 2c6af01..01aa7b7 100644
--- a/src/internal/bytealg/equal_arm64.s
+++ b/src/internal/bytealg/equal_arm64.s
@@ -5,26 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT,$0-49
- MOVD a_len+8(FP), R1
- MOVD b_len+32(FP), R3
- CMP R1, R3
- // unequal lengths are not equal
- BNE not_equal
- // short path to handle 0-byte case
- CBZ R1, equal
- MOVD a_base+0(FP), R0
- MOVD b_base+24(FP), R2
- MOVD $ret+48(FP), R8
- B memeqbody<>(SB)
-equal:
- MOVD $1, R0
- MOVB R0, ret+48(FP)
- RET
-not_equal:
- MOVB ZR, ret+48(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-25
MOVD size+16(FP), R1
diff --git a/src/internal/bytealg/equal_generic.go b/src/internal/bytealg/equal_generic.go
new file mode 100644
index 0000000..59bdf8f
--- /dev/null
+++ b/src/internal/bytealg/equal_generic.go
@@ -0,0 +1,18 @@
+// Copyright 2019 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.
+
+package bytealg
+
+// Equal reports whether a and b
+// are the same length and contain the same bytes.
+// A nil argument is equivalent to an empty slice.
+//
+// Equal is equivalent to bytes.Equal.
+// It is provided here for convenience,
+// because some packages cannot depend on bytes.
+func Equal(a, b []byte) bool {
+ // Neither cmd/compile nor gccgo allocates for these string conversions.
+ // There is a test for this in package bytes.
+ return string(a) == string(b)
+}
diff --git a/src/internal/bytealg/equal_mips64x.s b/src/internal/bytealg/equal_mips64x.s
index a75b957..58dc430 100644
--- a/src/internal/bytealg/equal_mips64x.s
+++ b/src/internal/bytealg/equal_mips64x.s
@@ -9,32 +9,6 @@
#define REGCTXT R22
-TEXT ·Equal(SB),NOSPLIT,$0-49
- MOVV a_len+8(FP), R3
- MOVV b_len+32(FP), R4
- BNE R3, R4, noteq // unequal lengths are not equal
-
- MOVV a_base+0(FP), R1
- MOVV b_base+24(FP), R2
- ADDV R1, R3 // end
-
-loop:
- BEQ R1, R3, equal // reached the end
- MOVBU (R1), R6
- ADDV $1, R1
- MOVBU (R2), R7
- ADDV $1, R2
- BEQ R6, R7, loop
-
-noteq:
- MOVB R0, ret+48(FP)
- RET
-
-equal:
- MOVV $1, R1
- MOVB R1, ret+48(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-25
MOVV a+0(FP), R1
diff --git a/src/internal/bytealg/equal_mipsx.s b/src/internal/bytealg/equal_mipsx.s
index 70d579d..1cabc70 100644
--- a/src/internal/bytealg/equal_mipsx.s
+++ b/src/internal/bytealg/equal_mipsx.s
@@ -9,32 +9,6 @@
#define REGCTXT R22
-TEXT ·Equal(SB),NOSPLIT,$0-25
- MOVW a_len+4(FP), R3
- MOVW b_len+16(FP), R4
- BNE R3, R4, noteq // unequal lengths are not equal
-
- MOVW a_base+0(FP), R1
- MOVW b_base+12(FP), R2
- ADDU R1, R3 // end
-
-loop:
- BEQ R1, R3, equal // reached the end
- MOVBU (R1), R6
- ADDU $1, R1
- MOVBU (R2), R7
- ADDU $1, R2
- BEQ R6, R7, loop
-
-noteq:
- MOVB R0, ret+24(FP)
- RET
-
-equal:
- MOVW $1, R1
- MOVB R1, ret+24(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT,$0-13
MOVW a+0(FP), R1
diff --git a/src/internal/bytealg/equal_native.go b/src/internal/bytealg/equal_native.go
index 995f074..cf3a245 100644
--- a/src/internal/bytealg/equal_native.go
+++ b/src/internal/bytealg/equal_native.go
@@ -6,11 +6,6 @@
import "unsafe"
-// Note: there's no equal_generic.go because every platform must implement at least memequal_varlen in assembly.
-
-//go:noescape
-func Equal(a, b []byte) bool
-
// The declarations below generate ABI wrappers for functions
// implemented in assembly in this package but declared in another
// package.
diff --git a/src/internal/bytealg/equal_ppc64x.s b/src/internal/bytealg/equal_ppc64x.s
index 74ea348..18171ea 100644
--- a/src/internal/bytealg/equal_ppc64x.s
+++ b/src/internal/bytealg/equal_ppc64x.s
@@ -7,25 +7,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT|NOFRAME,$0-49
- MOVD a_len+8(FP), R4
- MOVD b_len+32(FP), R5
- CMP R5, R4 // unequal lengths are not equal
- BNE noteq
- MOVD a_base+0(FP), R3
- MOVD b_base+24(FP), R4
- MOVD $ret+48(FP), R10
- BR memeqbody<>(SB)
-
-noteq:
- MOVBZ $0,ret+48(FP)
- RET
-
-equal:
- MOVD $1,R3
- MOVBZ R3,ret+48(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-25
MOVD a+0(FP), R3
diff --git a/src/internal/bytealg/equal_s390x.s b/src/internal/bytealg/equal_s390x.s
index d772474..67f814d 100644
--- a/src/internal/bytealg/equal_s390x.s
+++ b/src/internal/bytealg/equal_s390x.s
@@ -5,18 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB),NOSPLIT|NOFRAME,$0-49
- MOVD a_len+8(FP), R2
- MOVD b_len+32(FP), R6
- MOVD a_base+0(FP), R3
- MOVD b_base+24(FP), R5
- LA ret+48(FP), R7
- CMPBNE R2, R6, notequal
- BR memeqbody<>(SB)
-notequal:
- MOVB $0, ret+48(FP)
- RET
-
// memequal(a, b unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-25
MOVD a+0(FP), R3
diff --git a/src/internal/bytealg/equal_wasm.s b/src/internal/bytealg/equal_wasm.s
index cac3fb2..a2b76c1 100644
--- a/src/internal/bytealg/equal_wasm.s
+++ b/src/internal/bytealg/equal_wasm.s
@@ -5,26 +5,6 @@
#include "go_asm.h"
#include "textflag.h"
-TEXT ·Equal(SB), NOSPLIT, $0-49
- MOVD a_len+8(FP), R0
- MOVD b_len+32(FP), R1
- Get R0
- Get R1
- I64Eq
- If
- Get SP
- I64Load a+0(FP)
- I64Load b+24(FP)
- Get R0
- Call memeqbody<>(SB)
- I64Store8 ret+48(FP)
- Else
- Get SP
- I64Const $0
- I64Store8 ret+48(FP)
- End
- RET
-
// memequal(p, q unsafe.Pointer, size uintptr) bool
TEXT runtime·memequal(SB), NOSPLIT, $0-25
Get SP
