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strings: add asm version of Index() for short strings on amd64
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Currently we have special case for 1-byte strings,
This extends this to strings shorter than 32 bytes on amd64.
Results (broadwell):

name                 old time/op  new time/op  delta
IndexRune-4          57.4ns ± 0%  57.5ns ± 0%   +0.10%        (p=0.000 n=20+19)
IndexRuneFastPath-4  20.4ns ± 0%  20.4ns ± 0%     ~     (all samples are equal)
Index-4              21.0ns ± 0%  21.8ns ± 0%   +3.81%        (p=0.000 n=20+20)
LastIndex-4          7.07ns ± 1%  6.98ns ± 0%   -1.21%        (p=0.000 n=20+16)
IndexByte-4          18.3ns ± 0%  18.3ns ± 0%     ~     (all samples are equal)
IndexHard1-4         1.46ms ± 0%  0.39ms ± 0%  -73.06%        (p=0.000 n=16+16)
IndexHard2-4         1.46ms ± 0%  0.30ms ± 0%  -79.55%        (p=0.000 n=18+18)
IndexHard3-4         1.46ms ± 0%  0.66ms ± 0%  -54.68%        (p=0.000 n=19+19)
LastIndexHard1-4     1.46ms ± 0%  1.46ms ± 0%   -0.01%        (p=0.036 n=18+20)
LastIndexHard2-4     1.46ms ± 0%  1.46ms ± 0%     ~           (p=0.588 n=19+19)
LastIndexHard3-4     1.46ms ± 0%  1.46ms ± 0%     ~           (p=0.283 n=17+20)
IndexTorture-4       11.1µs ± 0%  11.1µs ± 0%   +0.01%        (p=0.000 n=18+17)

Change-Id: I892781549f558f698be4e41f9f568e3d0611efb5
Reviewed-on: https://go-review.googlesource.com/16430
Reviewed-by: Keith Randall <[email protected]>
Run-TryBot: Ilya Tocar <[email protected]>
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@TocarIP @randall77
TocarIP authored and randall77 committed Nov 3, 2015
1 parent 1870572 commit 95333ae
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Showing 5 changed files with 311 additions and 37 deletions.
162 changes: 162 additions & 0 deletions src/runtime/asm_amd64.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1725,6 +1725,168 @@ big_loop_avx2_exit:
JMP loop


// TODO: Also use this in bytes.Index
TEXT strings·indexShortStr(SB),NOSPLIT,$0-40
MOVQ s+0(FP), DI
MOVQ s_len+8(FP), CX
MOVQ c+16(FP), AX
MOVQ c_len+24(FP), BX
CMPQ BX, CX
JA fail
CMPQ BX, $2
JA _3_or_more
MOVW (AX), AX
LEAQ -1(DI)(CX*1), CX
loop2:
MOVW (DI), SI
CMPW SI,AX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop2
JMP fail
_3_or_more:
CMPQ BX, $3
JA _4_or_more
MOVW 1(AX), DX
MOVW (AX), AX
LEAQ -2(DI)(CX*1), CX
loop3:
MOVW (DI), SI
CMPW SI,AX
JZ partial_success3
ADDQ $1,DI
CMPQ DI,CX
JB loop3
JMP fail
partial_success3:
MOVW 1(DI), SI
CMPW SI,DX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop3
JMP fail
_4_or_more:
CMPQ BX, $4
JA _5_or_more
MOVL (AX), AX
LEAQ -3(DI)(CX*1), CX
loop4:
MOVL (DI), SI
CMPL SI,AX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop4
JMP fail
_5_or_more:
CMPQ BX, $7
JA _8_or_more
LEAQ 1(DI)(CX*1), CX
SUBQ BX, CX
MOVL -4(AX)(BX*1), DX
MOVL (AX), AX
loop5to7:
MOVL (DI), SI
CMPL SI,AX
JZ partial_success5to7
ADDQ $1,DI
CMPQ DI,CX
JB loop5to7
JMP fail
partial_success5to7:
MOVL -4(BX)(DI*1), SI
CMPL SI,DX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop5to7
JMP fail
_8_or_more:
CMPQ BX, $8
JA _9_or_more
MOVQ (AX), AX
LEAQ -7(DI)(CX*1), CX
loop8:
MOVQ (DI), SI
CMPQ SI,AX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop8
JMP fail
_9_or_more:
CMPQ BX, $16
JA _16_or_more
LEAQ 1(DI)(CX*1), CX
SUBQ BX, CX
MOVQ -8(AX)(BX*1), DX
MOVQ (AX), AX
loop9to15:
MOVQ (DI), SI
CMPQ SI,AX
JZ partial_success9to15
ADDQ $1,DI
CMPQ DI,CX
JB loop9to15
JMP fail
partial_success9to15:
MOVQ -8(BX)(DI*1), SI
CMPQ SI,DX
JZ success
ADDQ $1,DI
CMPQ DI,CX
JB loop9to15
JMP fail
_16_or_more:
CMPQ BX, $16
JA _17_to_31
MOVOU (AX), X1
LEAQ -15(DI)(CX*1), CX
loop16:
MOVOU (DI), X2
PCMPEQB X1, X2
PMOVMSKB X2, SI
CMPQ SI, $0xffff
JE success
ADDQ $1,DI
CMPQ DI,CX
JB loop16
JMP fail
_17_to_31:
LEAQ 1(DI)(CX*1), CX
SUBQ BX, CX
MOVOU -16(AX)(BX*1), X0
MOVOU (AX), X1
loop17to31:
MOVOU (DI), X2
PCMPEQB X1,X2
PMOVMSKB X2, SI
CMPQ SI, $0xffff
JE partial_success17to31
ADDQ $1,DI
CMPQ DI,CX
JB loop17to31
JMP fail
partial_success17to31:
MOVOU -16(BX)(DI*1), X3
PCMPEQB X0, X3
PMOVMSKB X3, SI
CMPQ SI, $0xffff
JE success
ADDQ $1,DI
CMPQ DI,CX
JB loop17to31
fail:
MOVQ $-1, ret+32(FP)
RET
success:
SUBQ s+0(FP), DI
MOVQ DI, ret+32(FP)
RET


TEXT bytes·IndexByte(SB),NOSPLIT,$0-40
MOVQ s+0(FP), SI
MOVQ s_len+8(FP), BX
Expand Down
37 changes: 0 additions & 37 deletions src/strings/strings.go
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Original file line number Diff line number Diff line change
Expand Up @@ -143,43 +143,6 @@ func ContainsRune(s string, r rune) bool {
return IndexRune(s, r) >= 0
}

// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
func Index(s, sep string) int {
n := len(sep)
switch {
case n == 0:
return 0
case n == 1:
return IndexByte(s, sep[0])
case n == len(s):
if sep == s {
return 0
}
return -1
case n > len(s):
return -1
}
// Rabin-Karp search
hashsep, pow := hashStr(sep)
var h uint32
for i := 0; i < n; i++ {
h = h*primeRK + uint32(s[i])
}
if h == hashsep && s[:n] == sep {
return 0
}
for i := n; i < len(s); {
h *= primeRK
h += uint32(s[i])
h -= pow * uint32(s[i-n])
i++
if h == hashsep && s[i-n:i] == sep {
return i - n
}
}
return -1
}

// LastIndex returns the index of the last instance of sep in s, or -1 if sep is not present in s.
func LastIndex(s, sep string) int {
n := len(sep)
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49 changes: 49 additions & 0 deletions src/strings/strings_amd64.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,49 @@
// Copyright 2015 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 strings

// indexShortStr returns the index of the first instance of c in s, or -1 if c is not present in s.
// indexShortStr requires 2 <= len(c) <= shortStringLen
func indexShortStr(s, c string) int // ../runtime/asm_$GOARCH.s
const shortStringLen = 31

// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
func Index(s, sep string) int {
n := len(sep)
switch {
case n == 0:
return 0
case n == 1:
return IndexByte(s, sep[0])
case n <= shortStringLen:
return indexShortStr(s, sep)
case n == len(s):
if sep == s {
return 0
}
return -1
case n > len(s):
return -1
}
// Rabin-Karp search
hashsep, pow := hashStr(sep)
var h uint32
for i := 0; i < n; i++ {
h = h*primeRK + uint32(s[i])
}
if h == hashsep && s[:n] == sep {
return 0
}
for i := n; i < len(s); {
h *= primeRK
h += uint32(s[i])
h -= pow * uint32(s[i-n])
i++
if h == hashsep && s[i-n:i] == sep {
return i - n
}
}
return -1
}
47 changes: 47 additions & 0 deletions src/strings/strings_generic.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,47 @@
// Copyright 2015 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.

// +build !amd64

package strings

// TODO: implements short string optimization on non amd64 platforms
// and get rid of strings_amd64.go

// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
func Index(s, sep string) int {
n := len(sep)
switch {
case n == 0:
return 0
case n == 1:
return IndexByte(s, sep[0])
case n == len(s):
if sep == s {
return 0
}
return -1
case n > len(s):
return -1
}
// Rabin-Karp search
hashsep, pow := hashStr(sep)
var h uint32
for i := 0; i < n; i++ {
h = h*primeRK + uint32(s[i])
}
if h == hashsep && s[:n] == sep {
return 0
}
for i := n; i < len(s); {
h *= primeRK
h += uint32(s[i])
h -= pow * uint32(s[i-n])
i++
if h == hashsep && s[i-n:i] == sep {
return i - n
}
}
return -1
}
53 changes: 53 additions & 0 deletions src/strings/strings_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,59 @@ var indexTests = []IndexTest{
{"abc", "b", 1},
{"abc", "c", 2},
{"abc", "x", -1},
// test special cases in Index() for short strings
{"", "ab", -1},
{"bc", "ab", -1},
{"ab", "ab", 0},
{"xab", "ab", 1},
{"xab"[:2], "ab", -1},
{"", "abc", -1},
{"xbc", "abc", -1},
{"abc", "abc", 0},
{"xabc", "abc", 1},
{"xabc"[:3], "abc", -1},
{"xabxc", "abc", -1},
{"", "abcd", -1},
{"xbcd", "abcd", -1},
{"abcd", "abcd", 0},
{"xabcd", "abcd", 1},
{"xyabcd"[:5], "abcd", -1},
{"xbcqq", "abcqq", -1},
{"abcqq", "abcqq", 0},
{"xabcqq", "abcqq", 1},
{"xyabcqq"[:6], "abcqq", -1},
{"xabxcqq", "abcqq", -1},
{"xabcqxq", "abcqq", -1},
{"", "01234567", -1},
{"32145678", "01234567", -1},
{"01234567", "01234567", 0},
{"x01234567", "01234567", 1},
{"xx01234567"[:9], "01234567", -1},
{"", "0123456789", -1},
{"3214567844", "0123456789", -1},
{"0123456789", "0123456789", 0},
{"x0123456789", "0123456789", 1},
{"xyz0123456789"[:12], "0123456789", -1},
{"x01234567x89", "0123456789", -1},
{"", "0123456789012345", -1},
{"3214567889012345", "0123456789012345", -1},
{"0123456789012345", "0123456789012345", 0},
{"x0123456789012345", "0123456789012345", 1},
{"", "01234567890123456789", -1},
{"32145678890123456789", "01234567890123456789", -1},
{"01234567890123456789", "01234567890123456789", 0},
{"x01234567890123456789", "01234567890123456789", 1},
{"xyz01234567890123456789"[:22], "01234567890123456789", -1},
{"", "0123456789012345678901234567890", -1},
{"321456788901234567890123456789012345678911", "0123456789012345678901234567890", -1},
{"0123456789012345678901234567890", "0123456789012345678901234567890", 0},
{"x0123456789012345678901234567890", "0123456789012345678901234567890", 1},
{"xyz0123456789012345678901234567890"[:33], "0123456789012345678901234567890", -1},
{"", "01234567890123456789012345678901", -1},
{"32145678890123456789012345678901234567890211", "01234567890123456789012345678901", -1},
{"01234567890123456789012345678901", "01234567890123456789012345678901", 0},
{"x01234567890123456789012345678901", "01234567890123456789012345678901", 1},
{"xyz01234567890123456789012345678901"[:34], "01234567890123456789012345678901", -1},
}

var lastIndexTests = []IndexTest{
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