From: Keith Randall <khr@golang.org>
Date: Mon, 22 Feb 2016 21:20:38 +0000 (-0800)
Subject: runtime: unify memeq and memequal
X-Git-Tag: go1.7beta1~1775
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bd70bd9cb2f458b23222083a3a11190f080af7fd;p=gostls13.git

runtime: unify memeq and memequal

They do the same thing, except memequal also has the short-circuit
check if the two pointers are equal.

A) We might as well always do the short-circuit check, it is only 2 instructions.
B) The extra function call (memequal->memeq) is expensive.

benchmark                 old ns/op     new ns/op     delta
BenchmarkArrayEqual-8     8.56          5.31          -37.97%

No noticeable affect on the former memeq user (maps).

Fixes #14302

Change-Id: I85d1ada59ed11e64dd6c54667f79d32cc5f81948
Reviewed-on: https://go-review.googlesource.com/19843
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
---

diff --git a/src/runtime/alg.go b/src/runtime/alg.go
index 541649c62d..9e19119f4a 100644
--- a/src/runtime/alg.go
+++ b/src/runtime/alg.go
@@ -172,13 +172,6 @@ func nilinterhash(p unsafe.Pointer, h uintptr) uintptr {
 	}
 }
 
-func memequal(p, q unsafe.Pointer, size uintptr) bool {
-	if p == q {
-		return true
-	}
-	return memeq(p, q, size)
-}
-
 func memequal0(p, q unsafe.Pointer) bool {
 	return true
 }
diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index 4181859724..9237d57f24 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -1239,12 +1239,18 @@ TEXT ·checkASM(SB),NOSPLIT,$0-1
 	SETEQ	ret+0(FP)
 	RET
 
-TEXT runtime·memeq(SB),NOSPLIT,$0-13
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$0-13
 	MOVL	a+0(FP), SI
 	MOVL	b+4(FP), DI
+	CMPL	SI, DI
+	JEQ	eq
 	MOVL	size+8(FP), BX
 	LEAL	ret+12(FP), AX
 	JMP	runtime·memeqbody(SB)
+eq:
+	MOVB    $1, ret+12(FP)
+	RET
 
 // memequal_varlen(a, b unsafe.Pointer) bool
 TEXT runtime·memequal_varlen(SB),NOSPLIT,$0-9
diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 5094812a05..98a8e839ed 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -1269,12 +1269,18 @@ DATA shifts<>+0xf0(SB)/8, $0x0807060504030201
 DATA shifts<>+0xf8(SB)/8, $0xff0f0e0d0c0b0a09
 GLOBL shifts<>(SB),RODATA,$256
 
-TEXT runtime·memeq(SB),NOSPLIT,$0-25
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$0-25
 	MOVQ	a+0(FP), SI
 	MOVQ	b+8(FP), DI
+	CMPQ	SI, DI
+	JEQ	eq
 	MOVQ	size+16(FP), BX
 	LEAQ	ret+24(FP), AX
 	JMP	runtime·memeqbody(SB)
+eq:
+	MOVB	$1, ret+24(FP)
+	RET
 
 // memequal_varlen(a, b unsafe.Pointer) bool
 TEXT runtime·memequal_varlen(SB),NOSPLIT,$0-17
diff --git a/src/runtime/asm_amd64p32.s b/src/runtime/asm_amd64p32.s
index ecbc5975bb..ae7a53821b 100644
--- a/src/runtime/asm_amd64p32.s
+++ b/src/runtime/asm_amd64p32.s
@@ -573,13 +573,19 @@ TEXT runtime·aeshash64(SB),NOSPLIT,$0-20
 	MOVL	AX, ret+16(FP)
 	RET
 
-TEXT runtime·memeq(SB),NOSPLIT,$0-17
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$0-13
 	MOVL	a+0(FP), SI
 	MOVL	b+4(FP), DI
+	CMPL	SI, DI
+	JEQ	eq
 	MOVL	size+8(FP), BX
 	CALL	runtime·memeqbody(SB)
 	MOVB	AX, ret+16(FP)
 	RET
+eq:
+	MOVB    $1, ret+16(FP)
+	RET
 
 // memequal_varlen(a, b unsafe.Pointer) bool
 TEXT runtime·memequal_varlen(SB),NOSPLIT,$0-9
diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s
index 07894a3a72..5d0206d1c9 100644
--- a/src/runtime/asm_arm.s
+++ b/src/runtime/asm_arm.s
@@ -750,13 +750,16 @@ TEXT runtime·memhash_varlen(SB),NOSPLIT,$16-12
 	MOVW	R0, ret+8(FP)
 	RET
 
-TEXT runtime·memeq(SB),NOSPLIT,$-4-13
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$-4-13
 	MOVW	a+0(FP), R1
 	MOVW	b+4(FP), R2
 	MOVW	size+8(FP), R3
 	ADD	R1, R3, R6
 	MOVW	$1, R0
 	MOVB	R0, ret+12(FP)
+	CMP	R1, R2
+	RET.EQ
 loop:
 	CMP	R1, R6
 	RET.EQ
@@ -779,7 +782,7 @@ TEXT runtime·memequal_varlen(SB),NOSPLIT,$16-9
 	MOVW	R0, 4(R13)
 	MOVW	R1, 8(R13)
 	MOVW	R2, 12(R13)
-	BL	runtime·memeq(SB)
+	BL	runtime·memequal(SB)
 	MOVB	16(R13), R0
 	MOVB	R0, ret+8(FP)
 	RET
@@ -866,7 +869,7 @@ loop:
 	MOVB	R8, v+16(FP)
 	RET
 
-// TODO: share code with memeq?
+// TODO: share code with memequal?
 TEXT bytes·Equal(SB),NOSPLIT,$0-25
 	MOVW	a_len+4(FP), R1
 	MOVW	b_len+16(FP), R3
diff --git a/src/runtime/asm_arm64.s b/src/runtime/asm_arm64.s
index ab5d5b5e5f..5a5c64c270 100644
--- a/src/runtime/asm_arm64.s
+++ b/src/runtime/asm_arm64.s
@@ -765,13 +765,16 @@ TEXT runtime·memhash_varlen(SB),NOSPLIT,$40-24
 	MOVD	R3, ret+16(FP)
 	RET
 
-TEXT runtime·memeq(SB),NOSPLIT,$-8-25
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$-8-25
 	MOVD	a+0(FP), R1
 	MOVD	b+8(FP), R2
 	MOVD	size+16(FP), R3
 	ADD	R1, R3, R6
 	MOVD	$1, R0
 	MOVB	R0, ret+24(FP)
+	CMP	R1, R2
+	BEQ	done
 loop:
 	CMP	R1, R6
 	BEQ	done
@@ -794,7 +797,7 @@ TEXT runtime·memequal_varlen(SB),NOSPLIT,$40-17
 	MOVD	R3, 8(RSP)
 	MOVD	R4, 16(RSP)
 	MOVD	R5, 24(RSP)
-	BL	runtime·memeq(SB)
+	BL	runtime·memequal(SB)
 	MOVBU	32(RSP), R3
 	MOVB	R3, ret+16(FP)
 	RET
@@ -929,7 +932,7 @@ notfound:
 	MOVD	R0, ret+24(FP)
 	RET
 
-// TODO: share code with memeq?
+// TODO: share code with memequal?
 TEXT bytes·Equal(SB),NOSPLIT,$0-49
 	MOVD	a_len+8(FP), R1
 	MOVD	b_len+32(FP), R3
diff --git a/src/runtime/asm_mips64x.s b/src/runtime/asm_mips64x.s
index 08482fed23..80cea8587a 100644
--- a/src/runtime/asm_mips64x.s
+++ b/src/runtime/asm_mips64x.s
@@ -647,9 +647,11 @@ TEXT runtime·aeshash64(SB),NOSPLIT,$-8-0
 TEXT runtime·aeshashstr(SB),NOSPLIT,$-8-0
 	MOVW	(R0), R1
 
-TEXT runtime·memeq(SB),NOSPLIT,$-8-25
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT,$-8-25
 	MOVV	a+0(FP), R1
 	MOVV	b+8(FP), R2
+	BEQ	R1, R2, eq
 	MOVV	size+16(FP), R3
 	ADDV	R1, R3, R4
 loop:
@@ -666,6 +668,10 @@ test:
 
 	MOVB	R0, ret+24(FP)
 	RET
+eq:
+	MOVV	$1, R1
+	MOVB	R1, ret+24(FP)
+	RET
 
 // memequal_varlen(a, b unsafe.Pointer) bool
 TEXT runtime·memequal_varlen(SB),NOSPLIT,$40-17
@@ -676,7 +682,7 @@ TEXT runtime·memequal_varlen(SB),NOSPLIT,$40-17
 	MOVV	R1, 8(R29)
 	MOVV	R2, 16(R29)
 	MOVV	R3, 24(R29)
-	JAL	runtime·memeq(SB)
+	JAL	runtime·memequal(SB)
 	MOVBU	32(R29), R1
 	MOVB	R1, ret+16(FP)
 	RET
@@ -710,7 +716,7 @@ loop:
 	MOVB	R0, ret+32(FP)
 	RET
 
-// TODO: share code with memeq?
+// TODO: share code with memequal?
 TEXT bytes·Equal(SB),NOSPLIT,$0-49
 	MOVV	a_len+8(FP), R3
 	MOVV	b_len+32(FP), R4
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 50c4f2623c..f067b4a9b9 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -795,9 +795,12 @@ TEXT runtime·aeshash64(SB),NOSPLIT|NOFRAME,$0-0
 TEXT runtime·aeshashstr(SB),NOSPLIT|NOFRAME,$0-0
 	MOVW	(R0), R1
 
-TEXT runtime·memeq(SB),NOSPLIT|NOFRAME,$0-25
+// memequal(p, q unsafe.Pointer, size uintptr) bool
+TEXT runtime·memequal(SB),NOSPLIT|NOFRAME,$0-25
 	MOVD	a+0(FP), R3
 	MOVD	b+8(FP), R4
+	CMP	R3, R4
+	BEQ	eq
 	MOVD	size+16(FP), R5
 	SUB	$1, R3
 	SUB	$1, R4
@@ -816,6 +819,10 @@ test:
 
 	MOVB	R0, ret+24(FP)
 	RET
+eq:
+	MOVD	$1, R1
+	MOVB	R1, ret+24(FP)
+	RET
 
 // memequal_varlen(a, b unsafe.Pointer) bool
 TEXT runtime·memequal_varlen(SB),NOSPLIT,$40-17
@@ -827,7 +834,7 @@ TEXT runtime·memequal_varlen(SB),NOSPLIT,$40-17
 	MOVD	R3, FIXED_FRAME+0(R1)
 	MOVD	R4, FIXED_FRAME+8(R1)
 	MOVD	R5, FIXED_FRAME+16(R1)
-	BL	runtime·memeq(SB)
+	BL	runtime·memequal(SB)
 	MOVBZ	FIXED_FRAME+24(R1), R3
 	MOVB	R3, ret+16(FP)
 	RET
@@ -864,7 +871,7 @@ loop:
 	MOVB	R0, ret+32(FP)
 	RET
 
-// TODO: share code with memeq?
+// TODO: share code with memequal?
 TEXT bytes·Equal(SB),NOSPLIT,$0-49
 	MOVD	a_len+8(FP), R3
 	MOVD	b_len+32(FP), R4
diff --git a/src/runtime/hashmap_fast.go b/src/runtime/hashmap_fast.go
index 519dc77f71..f95ea3e1b7 100644
--- a/src/runtime/hashmap_fast.go
+++ b/src/runtime/hashmap_fast.go
@@ -216,7 +216,7 @@ func mapaccess1_faststr(t *maptype, h *hmap, ky string) unsafe.Pointer {
 				if k.len != key.len {
 					continue
 				}
-				if k.str == key.str || memeq(k.str, key.str, uintptr(key.len)) {
+				if k.str == key.str || memequal(k.str, key.str, uintptr(key.len)) {
 					return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+i*uintptr(t.valuesize))
 				}
 			}
@@ -254,7 +254,7 @@ func mapaccess1_faststr(t *maptype, h *hmap, ky string) unsafe.Pointer {
 		}
 		if keymaybe != bucketCnt {
 			k := (*stringStruct)(add(unsafe.Pointer(b), dataOffset+keymaybe*2*sys.PtrSize))
-			if memeq(k.str, key.str, uintptr(key.len)) {
+			if memequal(k.str, key.str, uintptr(key.len)) {
 				return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+keymaybe*uintptr(t.valuesize))
 			}
 		}
@@ -284,7 +284,7 @@ dohash:
 			if k.len != key.len {
 				continue
 			}
-			if k.str == key.str || memeq(k.str, key.str, uintptr(key.len)) {
+			if k.str == key.str || memequal(k.str, key.str, uintptr(key.len)) {
 				return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+i*uintptr(t.valuesize))
 			}
 		}
@@ -321,7 +321,7 @@ func mapaccess2_faststr(t *maptype, h *hmap, ky string) (unsafe.Pointer, bool) {
 				if k.len != key.len {
 					continue
 				}
-				if k.str == key.str || memeq(k.str, key.str, uintptr(key.len)) {
+				if k.str == key.str || memequal(k.str, key.str, uintptr(key.len)) {
 					return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+i*uintptr(t.valuesize)), true
 				}
 			}
@@ -357,7 +357,7 @@ func mapaccess2_faststr(t *maptype, h *hmap, ky string) (unsafe.Pointer, bool) {
 		}
 		if keymaybe != bucketCnt {
 			k := (*stringStruct)(add(unsafe.Pointer(b), dataOffset+keymaybe*2*sys.PtrSize))
-			if memeq(k.str, key.str, uintptr(key.len)) {
+			if memequal(k.str, key.str, uintptr(key.len)) {
 				return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+keymaybe*uintptr(t.valuesize)), true
 			}
 		}
@@ -387,7 +387,7 @@ dohash:
 			if k.len != key.len {
 				continue
 			}
-			if k.str == key.str || memeq(k.str, key.str, uintptr(key.len)) {
+			if k.str == key.str || memequal(k.str, key.str, uintptr(key.len)) {
 				return add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+i*uintptr(t.valuesize)), true
 			}
 		}
diff --git a/src/runtime/string_test.go b/src/runtime/string_test.go
index 150a25520a..37b75c1a89 100644
--- a/src/runtime/string_test.go
+++ b/src/runtime/string_test.go
@@ -102,6 +102,17 @@ func BenchmarkRuneIterate2(b *testing.B) {
 	}
 }
 
+func BenchmarkArrayEqual(b *testing.B) {
+	a1 := [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
+	a2 := [16]byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if a1 != a2 {
+			b.Fatal("not equal")
+		}
+	}
+}
+
 func TestStringW(t *testing.T) {
 	strings := []string{
 		"hello",
diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go
index f060182c22..6c28fd2e78 100644
--- a/src/runtime/stubs.go
+++ b/src/runtime/stubs.go
@@ -85,7 +85,7 @@ func fastrand1() uint32
 
 // in asm_*.s
 //go:noescape
-func memeq(a, b unsafe.Pointer, size uintptr) bool
+func memequal(a, b unsafe.Pointer, size uintptr) bool
 
 // noescape hides a pointer from escape analysis.  noescape is
 // the identity function but escape analysis doesn't think the