2018-03-02 07:16:27 -07:00
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// asmcheck
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package codegen
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import "math/bits"
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2018-03-05 11:46:18 -07:00
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// ----------------------- //
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// bits.LeadingZeros //
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// ----------------------- //
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func LeadingZeros(n uint) int {
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2018-03-08 09:43:55 -07:00
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-05 11:46:18 -07:00
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return bits.LeadingZeros(n)
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}
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func LeadingZeros64(n uint64) int {
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2018-03-08 09:43:55 -07:00
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-05 11:46:18 -07:00
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return bits.LeadingZeros64(n)
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}
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func LeadingZeros32(n uint32) int {
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cmd/compile: optimize LeadingZeros(16|32) on amd64
Introduce Len8 and Len16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
Also use and optimize the Len32 lowering, along the same lines.
Leave Len8 unused for the moment; a subsequent CL will enable it.
For 16 and 32 bits, this leads to a speed-up.
name old time/op new time/op delta
LeadingZeros16-8 1.42ns ± 5% 1.23ns ± 5% -13.42% (p=0.000 n=20+20)
LeadingZeros32-8 1.25ns ± 5% 1.03ns ± 5% -17.63% (p=0.000 n=20+16)
Code:
func f16(x uint16) { z = bits.LeadingZeros16(x) }
func f32(x uint32) { z = bits.LeadingZeros32(x) }
Before:
"".f16 STEXT nosplit size=38 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BSRQ AX, AX
0x000c 00012 (x.go:8) MOVQ $-1, CX
0x0013 00019 (x.go:8) CMOVQEQ CX, AX
0x0017 00023 (x.go:8) ADDQ $-15, AX
0x001b 00027 (x.go:8) NEGQ AX
0x001e 00030 (x.go:8) MOVQ AX, "".z(SB)
0x0025 00037 (x.go:8) RET
"".f32 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) BSRQ AX, AX
0x0008 00008 (x.go:9) MOVQ $-1, CX
0x000f 00015 (x.go:9) CMOVQEQ CX, AX
0x0013 00019 (x.go:9) ADDQ $-31, AX
0x0017 00023 (x.go:9) NEGQ AX
0x001a 00026 (x.go:9) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:9) RET
After:
"".f16 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:8) BSRL AX, AX
0x000f 00015 (x.go:8) ADDQ $-16, AX
0x0013 00019 (x.go:8) NEGQ AX
0x0016 00022 (x.go:8) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:8) RET
"".f32 STEXT nosplit size=28 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) LEAQ 1(AX)(AX*1), AX
0x0009 00009 (x.go:9) BSRQ AX, AX
0x000d 00013 (x.go:9) ADDQ $-32, AX
0x0011 00017 (x.go:9) NEGQ AX
0x0014 00020 (x.go:9) MOVQ AX, "".z(SB)
0x001b 00027 (x.go:9) RET
Change-Id: I6c93c173752a7bfdeab8be30777ae05a736e1f4b
Reviewed-on: https://go-review.googlesource.com/108941
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:54:45 -06:00
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// amd64:"BSRQ","LEAQ",-"CMOVQEQ"
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2018-03-08 09:43:55 -07:00
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-05 11:46:18 -07:00
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return bits.LeadingZeros32(n)
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}
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func LeadingZeros16(n uint16) int {
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cmd/compile: optimize LeadingZeros(16|32) on amd64
Introduce Len8 and Len16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
Also use and optimize the Len32 lowering, along the same lines.
Leave Len8 unused for the moment; a subsequent CL will enable it.
For 16 and 32 bits, this leads to a speed-up.
name old time/op new time/op delta
LeadingZeros16-8 1.42ns ± 5% 1.23ns ± 5% -13.42% (p=0.000 n=20+20)
LeadingZeros32-8 1.25ns ± 5% 1.03ns ± 5% -17.63% (p=0.000 n=20+16)
Code:
func f16(x uint16) { z = bits.LeadingZeros16(x) }
func f32(x uint32) { z = bits.LeadingZeros32(x) }
Before:
"".f16 STEXT nosplit size=38 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BSRQ AX, AX
0x000c 00012 (x.go:8) MOVQ $-1, CX
0x0013 00019 (x.go:8) CMOVQEQ CX, AX
0x0017 00023 (x.go:8) ADDQ $-15, AX
0x001b 00027 (x.go:8) NEGQ AX
0x001e 00030 (x.go:8) MOVQ AX, "".z(SB)
0x0025 00037 (x.go:8) RET
"".f32 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) BSRQ AX, AX
0x0008 00008 (x.go:9) MOVQ $-1, CX
0x000f 00015 (x.go:9) CMOVQEQ CX, AX
0x0013 00019 (x.go:9) ADDQ $-31, AX
0x0017 00023 (x.go:9) NEGQ AX
0x001a 00026 (x.go:9) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:9) RET
After:
"".f16 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:8) BSRL AX, AX
0x000f 00015 (x.go:8) ADDQ $-16, AX
0x0013 00019 (x.go:8) NEGQ AX
0x0016 00022 (x.go:8) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:8) RET
"".f32 STEXT nosplit size=28 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) LEAQ 1(AX)(AX*1), AX
0x0009 00009 (x.go:9) BSRQ AX, AX
0x000d 00013 (x.go:9) ADDQ $-32, AX
0x0011 00017 (x.go:9) NEGQ AX
0x0014 00020 (x.go:9) MOVQ AX, "".z(SB)
0x001b 00027 (x.go:9) RET
Change-Id: I6c93c173752a7bfdeab8be30777ae05a736e1f4b
Reviewed-on: https://go-review.googlesource.com/108941
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:54:45 -06:00
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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2018-03-08 09:43:55 -07:00
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-05 11:46:18 -07:00
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return bits.LeadingZeros16(n)
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}
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func LeadingZeros8(n uint8) int {
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cmd/compile: use intrinsic for LeadingZeros8 on amd64
The previous change sped up the pure computation form of LeadingZeros8.
This places it somewhat close to the table lookup form.
Depending on something that varies from toolchain to toolchain
(alignment, perhaps?), the slowdown from ditching the table lookup
is either 20% or 5%.
This benchmark is the best case scenario for the table lookup:
It is in the L1 cache already.
I think we're close enough that we can switch to the computational version,
and trust that the memory effects and binary size savings will be worth it.
Code:
func f8(x uint8) { z = bits.LeadingZeros8(x) }
Before:
"".f8 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) LEAQ math/bits.len8tab(SB), CX
0x000f 00015 (x.go:7) MOVBLZX (CX)(AX*1), AX
0x0013 00019 (x.go:7) ADDQ $-8, AX
0x0017 00023 (x.go:7) NEGQ AX
0x001a 00026 (x.go:7) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:7) RET
After:
"".f8 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:7) BSRL AX, AX
0x000f 00015 (x.go:7) ADDQ $-8, AX
0x0013 00019 (x.go:7) NEGQ AX
0x0016 00022 (x.go:7) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:7) RET
Change-Id: Icc7db50a7820fb9a3da8a816d6b6940d7f8e193e
Reviewed-on: https://go-review.googlesource.com/108942
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 16:38:50 -06:00
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// amd64:"BSRL","LEAL",-"CMOVQEQ"
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2018-03-08 09:43:55 -07:00
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-05 11:46:18 -07:00
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return bits.LeadingZeros8(n)
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}
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2018-03-02 07:16:27 -07:00
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// --------------- //
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// bits.Len* //
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// --------------- //
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func Len(n uint) int {
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2018-03-08 09:43:55 -07:00
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-02 07:16:27 -07:00
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return bits.Len(n)
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}
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func Len64(n uint64) int {
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2018-03-08 09:43:55 -07:00
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// amd64:"BSRQ"
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-02 07:16:27 -07:00
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return bits.Len64(n)
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}
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func Len32(n uint32) int {
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cmd/compile: optimize LeadingZeros(16|32) on amd64
Introduce Len8 and Len16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
Also use and optimize the Len32 lowering, along the same lines.
Leave Len8 unused for the moment; a subsequent CL will enable it.
For 16 and 32 bits, this leads to a speed-up.
name old time/op new time/op delta
LeadingZeros16-8 1.42ns ± 5% 1.23ns ± 5% -13.42% (p=0.000 n=20+20)
LeadingZeros32-8 1.25ns ± 5% 1.03ns ± 5% -17.63% (p=0.000 n=20+16)
Code:
func f16(x uint16) { z = bits.LeadingZeros16(x) }
func f32(x uint32) { z = bits.LeadingZeros32(x) }
Before:
"".f16 STEXT nosplit size=38 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BSRQ AX, AX
0x000c 00012 (x.go:8) MOVQ $-1, CX
0x0013 00019 (x.go:8) CMOVQEQ CX, AX
0x0017 00023 (x.go:8) ADDQ $-15, AX
0x001b 00027 (x.go:8) NEGQ AX
0x001e 00030 (x.go:8) MOVQ AX, "".z(SB)
0x0025 00037 (x.go:8) RET
"".f32 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) BSRQ AX, AX
0x0008 00008 (x.go:9) MOVQ $-1, CX
0x000f 00015 (x.go:9) CMOVQEQ CX, AX
0x0013 00019 (x.go:9) ADDQ $-31, AX
0x0017 00023 (x.go:9) NEGQ AX
0x001a 00026 (x.go:9) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:9) RET
After:
"".f16 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:8) BSRL AX, AX
0x000f 00015 (x.go:8) ADDQ $-16, AX
0x0013 00019 (x.go:8) NEGQ AX
0x0016 00022 (x.go:8) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:8) RET
"".f32 STEXT nosplit size=28 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) LEAQ 1(AX)(AX*1), AX
0x0009 00009 (x.go:9) BSRQ AX, AX
0x000d 00013 (x.go:9) ADDQ $-32, AX
0x0011 00017 (x.go:9) NEGQ AX
0x0014 00020 (x.go:9) MOVQ AX, "".z(SB)
0x001b 00027 (x.go:9) RET
Change-Id: I6c93c173752a7bfdeab8be30777ae05a736e1f4b
Reviewed-on: https://go-review.googlesource.com/108941
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:54:45 -06:00
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// amd64:"BSRQ","LEAQ",-"CMOVQEQ"
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2018-03-08 09:43:55 -07:00
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// s390x:"FLOGR"
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// arm:"CLZ" arm64:"CLZ"
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// mips:"CLZ"
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2018-03-02 07:16:27 -07:00
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return bits.Len32(n)
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}
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func Len16(n uint16) int {
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cmd/compile: optimize LeadingZeros(16|32) on amd64
Introduce Len8 and Len16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
Also use and optimize the Len32 lowering, along the same lines.
Leave Len8 unused for the moment; a subsequent CL will enable it.
For 16 and 32 bits, this leads to a speed-up.
name old time/op new time/op delta
LeadingZeros16-8 1.42ns ± 5% 1.23ns ± 5% -13.42% (p=0.000 n=20+20)
LeadingZeros32-8 1.25ns ± 5% 1.03ns ± 5% -17.63% (p=0.000 n=20+16)
Code:
func f16(x uint16) { z = bits.LeadingZeros16(x) }
func f32(x uint32) { z = bits.LeadingZeros32(x) }
Before:
"".f16 STEXT nosplit size=38 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BSRQ AX, AX
0x000c 00012 (x.go:8) MOVQ $-1, CX
0x0013 00019 (x.go:8) CMOVQEQ CX, AX
0x0017 00023 (x.go:8) ADDQ $-15, AX
0x001b 00027 (x.go:8) NEGQ AX
0x001e 00030 (x.go:8) MOVQ AX, "".z(SB)
0x0025 00037 (x.go:8) RET
"".f32 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) BSRQ AX, AX
0x0008 00008 (x.go:9) MOVQ $-1, CX
0x000f 00015 (x.go:9) CMOVQEQ CX, AX
0x0013 00019 (x.go:9) ADDQ $-31, AX
0x0017 00023 (x.go:9) NEGQ AX
0x001a 00026 (x.go:9) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:9) RET
After:
"".f16 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:8) BSRL AX, AX
0x000f 00015 (x.go:8) ADDQ $-16, AX
0x0013 00019 (x.go:8) NEGQ AX
0x0016 00022 (x.go:8) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:8) RET
"".f32 STEXT nosplit size=28 args=0x8 locals=0x0
0x0000 00000 (x.go:9) TEXT "".f32(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:9) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:9) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:9) MOVL "".x+8(SP), AX
0x0004 00004 (x.go:9) LEAQ 1(AX)(AX*1), AX
0x0009 00009 (x.go:9) BSRQ AX, AX
0x000d 00013 (x.go:9) ADDQ $-32, AX
0x0011 00017 (x.go:9) NEGQ AX
0x0014 00020 (x.go:9) MOVQ AX, "".z(SB)
0x001b 00027 (x.go:9) RET
Change-Id: I6c93c173752a7bfdeab8be30777ae05a736e1f4b
Reviewed-on: https://go-review.googlesource.com/108941
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:54:45 -06:00
|
|
|
// amd64:"BSRL","LEAL",-"CMOVQEQ"
|
2018-03-08 09:43:55 -07:00
|
|
|
// s390x:"FLOGR"
|
|
|
|
// arm:"CLZ" arm64:"CLZ"
|
|
|
|
// mips:"CLZ"
|
2018-03-02 07:16:27 -07:00
|
|
|
return bits.Len16(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func Len8(n uint8) int {
|
cmd/compile: use intrinsic for LeadingZeros8 on amd64
The previous change sped up the pure computation form of LeadingZeros8.
This places it somewhat close to the table lookup form.
Depending on something that varies from toolchain to toolchain
(alignment, perhaps?), the slowdown from ditching the table lookup
is either 20% or 5%.
This benchmark is the best case scenario for the table lookup:
It is in the L1 cache already.
I think we're close enough that we can switch to the computational version,
and trust that the memory effects and binary size savings will be worth it.
Code:
func f8(x uint8) { z = bits.LeadingZeros8(x) }
Before:
"".f8 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) LEAQ math/bits.len8tab(SB), CX
0x000f 00015 (x.go:7) MOVBLZX (CX)(AX*1), AX
0x0013 00019 (x.go:7) ADDQ $-8, AX
0x0017 00023 (x.go:7) NEGQ AX
0x001a 00026 (x.go:7) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:7) RET
After:
"".f8 STEXT nosplit size=30 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) LEAL 1(AX)(AX*1), AX
0x000c 00012 (x.go:7) BSRL AX, AX
0x000f 00015 (x.go:7) ADDQ $-8, AX
0x0013 00019 (x.go:7) NEGQ AX
0x0016 00022 (x.go:7) MOVQ AX, "".z(SB)
0x001d 00029 (x.go:7) RET
Change-Id: Icc7db50a7820fb9a3da8a816d6b6940d7f8e193e
Reviewed-on: https://go-review.googlesource.com/108942
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 16:38:50 -06:00
|
|
|
// amd64:"BSRL","LEAL",-"CMOVQEQ"
|
2018-03-08 09:43:55 -07:00
|
|
|
// s390x:"FLOGR"
|
|
|
|
// arm:"CLZ" arm64:"CLZ"
|
|
|
|
// mips:"CLZ"
|
2018-03-02 07:16:27 -07:00
|
|
|
return bits.Len8(n)
|
|
|
|
}
|
2018-03-06 01:39:14 -07:00
|
|
|
|
2018-03-06 04:55:41 -07:00
|
|
|
// -------------------- //
|
|
|
|
// bits.OnesCount //
|
|
|
|
// -------------------- //
|
|
|
|
|
|
|
|
func OnesCount(n uint) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"POPCNTQ",".*support_popcnt"
|
|
|
|
// arm64:"VCNT","VUADDLV"
|
2018-03-06 04:55:41 -07:00
|
|
|
return bits.OnesCount(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func OnesCount64(n uint64) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"POPCNTQ",".*support_popcnt"
|
|
|
|
// arm64:"VCNT","VUADDLV"
|
2018-03-06 04:55:41 -07:00
|
|
|
return bits.OnesCount64(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func OnesCount32(n uint32) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"POPCNTL",".*support_popcnt"
|
|
|
|
// arm64:"VCNT","VUADDLV"
|
2018-03-06 04:55:41 -07:00
|
|
|
return bits.OnesCount32(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func OnesCount16(n uint16) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"POPCNTL",".*support_popcnt"
|
|
|
|
// arm64:"VCNT","VUADDLV"
|
2018-03-06 04:55:41 -07:00
|
|
|
return bits.OnesCount16(n)
|
|
|
|
}
|
|
|
|
|
2018-03-06 12:10:35 -07:00
|
|
|
// ----------------------- //
|
|
|
|
// bits.ReverseBytes //
|
|
|
|
// ----------------------- //
|
|
|
|
|
|
|
|
func ReverseBytes(n uint) uint {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"BSWAPQ"
|
|
|
|
// s390x:"MOVDBR"
|
|
|
|
// arm64:"REV"
|
2018-03-06 12:10:35 -07:00
|
|
|
return bits.ReverseBytes(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func ReverseBytes64(n uint64) uint64 {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"BSWAPQ"
|
|
|
|
// s390x:"MOVDBR"
|
|
|
|
// arm64:"REV"
|
2018-03-06 12:10:35 -07:00
|
|
|
return bits.ReverseBytes64(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func ReverseBytes32(n uint32) uint32 {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"BSWAPL"
|
|
|
|
// s390x:"MOVWBR"
|
|
|
|
// arm64:"REVW"
|
2018-03-06 12:10:35 -07:00
|
|
|
return bits.ReverseBytes32(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func ReverseBytes16(n uint16) uint16 {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"ROLW"
|
2018-03-06 12:10:35 -07:00
|
|
|
return bits.ReverseBytes16(n)
|
|
|
|
}
|
|
|
|
|
2018-03-08 09:43:55 -07:00
|
|
|
// --------------------- //
|
|
|
|
// bits.RotateLeft //
|
|
|
|
// --------------------- //
|
|
|
|
|
|
|
|
func RotateLeft64(n uint64) uint64 {
|
|
|
|
// amd64:"ROLQ"
|
|
|
|
// arm64:"ROR"
|
|
|
|
// ppc64:"ROTL"
|
|
|
|
return bits.RotateLeft64(n, 37)
|
|
|
|
}
|
|
|
|
|
|
|
|
func RotateLeft32(n uint32) uint32 {
|
|
|
|
// amd64:"ROLL" 386:"ROLL"
|
|
|
|
// arm64:"RORW"
|
|
|
|
// ppc64:"ROTLW"
|
|
|
|
return bits.RotateLeft32(n, 9)
|
|
|
|
}
|
|
|
|
|
|
|
|
func RotateLeft16(n uint16) uint16 {
|
|
|
|
// amd64:"ROLW" 386:"ROLW"
|
|
|
|
return bits.RotateLeft16(n, 5)
|
|
|
|
}
|
|
|
|
|
|
|
|
func RotateLeft8(n uint8) uint8 {
|
|
|
|
// amd64:"ROLB" 386:"ROLB"
|
|
|
|
return bits.RotateLeft8(n, 5)
|
|
|
|
}
|
|
|
|
|
2018-03-06 01:39:14 -07:00
|
|
|
// ------------------------ //
|
|
|
|
// bits.TrailingZeros //
|
|
|
|
// ------------------------ //
|
|
|
|
|
|
|
|
func TrailingZeros(n uint) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ"
|
|
|
|
// s390x:"FLOGR"
|
2018-03-06 01:39:14 -07:00
|
|
|
return bits.TrailingZeros(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func TrailingZeros64(n uint64) int {
|
2018-03-08 09:43:55 -07:00
|
|
|
// amd64:"BSFQ","MOVL\t\\$64","CMOVQEQ"
|
|
|
|
// s390x:"FLOGR"
|
2018-03-06 01:39:14 -07:00
|
|
|
return bits.TrailingZeros64(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func TrailingZeros32(n uint32) int {
|
cmd/compile: add patterns for bit set/clear/complement on amd64
This patch completes implementation of BT(Q|L), and adds support
for BT(S|R|C)(Q|L).
Example of code changes from time.(*Time).addSec:
if t.wall&hasMonotonic != 0 {
0x1073465 488b08 MOVQ 0(AX), CX
0x1073468 4889ca MOVQ CX, DX
0x107346b 48c1e93f SHRQ $0x3f, CX
0x107346f 48c1e13f SHLQ $0x3f, CX
0x1073473 48f7c1ffffffff TESTQ $-0x1, CX
0x107347a 746b JE 0x10734e7
if t.wall&hasMonotonic != 0 {
0x1073435 488b08 MOVQ 0(AX), CX
0x1073438 480fbae13f BTQ $0x3f, CX
0x107343d 7363 JAE 0x10734a2
Another example:
t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic
0x10734c8 4881e1ffffff3f ANDQ $0x3fffffff, CX
0x10734cf 48c1e61e SHLQ $0x1e, SI
0x10734d3 4809ce ORQ CX, SI
0x10734d6 48b90000000000000080 MOVQ $0x8000000000000000, CX
0x10734e0 4809f1 ORQ SI, CX
0x10734e3 488908 MOVQ CX, 0(AX)
t.wall = t.wall&nsecMask | uint64(dsec)<<nsecShift | hasMonotonic
0x107348b 4881e2ffffff3f ANDQ $0x3fffffff, DX
0x1073492 48c1e61e SHLQ $0x1e, SI
0x1073496 4809f2 ORQ SI, DX
0x1073499 480fbaea3f BTSQ $0x3f, DX
0x107349e 488910 MOVQ DX, 0(AX)
Go1 benchmarks seem unaffected, and I would be surprised
otherwise:
name old time/op new time/op delta
BinaryTree17-4 2.64s ± 4% 2.56s ± 9% -2.92% (p=0.008 n=9+9)
Fannkuch11-4 2.90s ± 1% 2.95s ± 3% +1.76% (p=0.010 n=10+9)
FmtFprintfEmpty-4 35.3ns ± 1% 34.5ns ± 2% -2.34% (p=0.004 n=9+8)
FmtFprintfString-4 57.0ns ± 1% 58.4ns ± 5% +2.52% (p=0.029 n=9+10)
FmtFprintfInt-4 59.8ns ± 3% 59.8ns ± 6% ~ (p=0.565 n=10+10)
FmtFprintfIntInt-4 93.9ns ± 3% 91.2ns ± 5% -2.94% (p=0.014 n=10+9)
FmtFprintfPrefixedInt-4 107ns ± 6% 104ns ± 6% ~ (p=0.099 n=10+10)
FmtFprintfFloat-4 187ns ± 3% 188ns ± 3% ~ (p=0.505 n=10+9)
FmtManyArgs-4 410ns ± 1% 415ns ± 6% ~ (p=0.649 n=8+10)
GobDecode-4 5.30ms ± 3% 5.27ms ± 3% ~ (p=0.436 n=10+10)
GobEncode-4 4.62ms ± 5% 4.47ms ± 2% -3.24% (p=0.001 n=9+10)
Gzip-4 197ms ± 4% 193ms ± 3% ~ (p=0.123 n=10+10)
Gunzip-4 30.4ms ± 3% 30.1ms ± 3% ~ (p=0.481 n=10+10)
HTTPClientServer-4 76.3µs ± 1% 76.0µs ± 1% ~ (p=0.236 n=8+9)
JSONEncode-4 10.5ms ± 9% 10.3ms ± 3% ~ (p=0.280 n=10+10)
JSONDecode-4 42.3ms ±10% 41.3ms ± 2% ~ (p=0.053 n=9+10)
Mandelbrot200-4 3.80ms ± 2% 3.72ms ± 2% -2.15% (p=0.001 n=9+10)
GoParse-4 2.88ms ±10% 2.81ms ± 2% ~ (p=0.247 n=10+10)
RegexpMatchEasy0_32-4 69.5ns ± 4% 68.6ns ± 2% ~ (p=0.171 n=10+10)
RegexpMatchEasy0_1K-4 165ns ± 3% 162ns ± 3% ~ (p=0.137 n=10+10)
RegexpMatchEasy1_32-4 65.7ns ± 6% 64.4ns ± 2% -2.02% (p=0.037 n=10+10)
RegexpMatchEasy1_1K-4 278ns ± 2% 279ns ± 3% ~ (p=0.991 n=8+9)
RegexpMatchMedium_32-4 99.3ns ± 3% 98.5ns ± 4% ~ (p=0.457 n=10+9)
RegexpMatchMedium_1K-4 30.1µs ± 1% 30.4µs ± 2% ~ (p=0.173 n=8+10)
RegexpMatchHard_32-4 1.40µs ± 2% 1.41µs ± 4% ~ (p=0.565 n=10+10)
RegexpMatchHard_1K-4 42.5µs ± 1% 41.5µs ± 3% -2.13% (p=0.002 n=8+9)
Revcomp-4 332ms ± 4% 328ms ± 5% ~ (p=0.720 n=9+10)
Template-4 48.3ms ± 2% 49.6ms ± 3% +2.56% (p=0.002 n=8+10)
TimeParse-4 252ns ± 2% 249ns ± 3% ~ (p=0.116 n=9+10)
TimeFormat-4 262ns ± 4% 252ns ± 3% -4.01% (p=0.000 n=9+10)
name old speed new speed delta
GobDecode-4 145MB/s ± 3% 146MB/s ± 3% ~ (p=0.436 n=10+10)
GobEncode-4 166MB/s ± 5% 172MB/s ± 2% +3.28% (p=0.001 n=9+10)
Gzip-4 98.6MB/s ± 4% 100.4MB/s ± 3% ~ (p=0.123 n=10+10)
Gunzip-4 639MB/s ± 3% 645MB/s ± 3% ~ (p=0.481 n=10+10)
JSONEncode-4 185MB/s ± 8% 189MB/s ± 3% ~ (p=0.280 n=10+10)
JSONDecode-4 46.0MB/s ± 9% 47.0MB/s ± 2% +2.21% (p=0.046 n=9+10)
GoParse-4 20.1MB/s ± 9% 20.6MB/s ± 2% ~ (p=0.239 n=10+10)
RegexpMatchEasy0_32-4 460MB/s ± 4% 467MB/s ± 2% ~ (p=0.165 n=10+10)
RegexpMatchEasy0_1K-4 6.19GB/s ± 3% 6.28GB/s ± 3% ~ (p=0.165 n=10+10)
RegexpMatchEasy1_32-4 487MB/s ± 5% 497MB/s ± 2% +2.00% (p=0.043 n=10+10)
RegexpMatchEasy1_1K-4 3.67GB/s ± 2% 3.67GB/s ± 3% ~ (p=0.963 n=8+9)
RegexpMatchMedium_32-4 10.1MB/s ± 3% 10.1MB/s ± 4% ~ (p=0.435 n=10+9)
RegexpMatchMedium_1K-4 34.0MB/s ± 1% 33.7MB/s ± 2% ~ (p=0.173 n=8+10)
RegexpMatchHard_32-4 22.9MB/s ± 2% 22.7MB/s ± 4% ~ (p=0.565 n=10+10)
RegexpMatchHard_1K-4 24.0MB/s ± 3% 24.7MB/s ± 3% +2.64% (p=0.001 n=9+9)
Revcomp-4 766MB/s ± 4% 775MB/s ± 5% ~ (p=0.720 n=9+10)
Template-4 40.2MB/s ± 2% 39.2MB/s ± 3% -2.47% (p=0.002 n=8+10)
The rules match ~1800 times during all.bash.
Fixes #18943
Change-Id: I64be1ada34e89c486dfd935bf429b35652117ed4
Reviewed-on: https://go-review.googlesource.com/94766
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
2018-02-17 05:54:03 -07:00
|
|
|
// amd64:"BTSQ\\t\\$32","BSFQ"
|
2018-03-08 09:43:55 -07:00
|
|
|
// s390x:"FLOGR","MOVWZ"
|
2018-03-06 01:39:14 -07:00
|
|
|
return bits.TrailingZeros32(n)
|
|
|
|
}
|
|
|
|
|
|
|
|
func TrailingZeros16(n uint16) int {
|
cmd/compile: optimize TrailingZeros(8|16) on amd64
Introduce Ctz8 and Ctz16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
name old time/op new time/op delta
TrailingZeros8-8 1.33ns ± 6% 0.84ns ± 3% -36.90% (p=0.000 n=20+20)
TrailingZeros16-8 1.26ns ± 5% 0.84ns ± 5% -33.50% (p=0.000 n=20+18)
Code:
func f8(x uint8) { z = bits.TrailingZeros8(x) }
func f16(x uint16) { z = bits.TrailingZeros16(x) }
Before:
"".f8 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) BTSQ $8, AX
0x000d 00013 (x.go:7) BSFQ AX, AX
0x0011 00017 (x.go:7) MOVL $64, CX
0x0016 00022 (x.go:7) CMOVQEQ CX, AX
0x001a 00026 (x.go:7) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:7) RET
"".f16 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BTSQ $16, AX
0x000d 00013 (x.go:8) BSFQ AX, AX
0x0011 00017 (x.go:8) MOVL $64, CX
0x0016 00022 (x.go:8) CMOVQEQ CX, AX
0x001a 00026 (x.go:8) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:8) RET
After:
"".f8 STEXT nosplit size=20 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) BTSL $8, AX
0x0009 00009 (x.go:7) BSFL AX, AX
0x000c 00012 (x.go:7) MOVQ AX, "".z(SB)
0x0013 00019 (x.go:7) RET
"".f16 STEXT nosplit size=20 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) BTSL $16, AX
0x0009 00009 (x.go:8) BSFL AX, AX
0x000c 00012 (x.go:8) MOVQ AX, "".z(SB)
0x0013 00019 (x.go:8) RET
Change-Id: I0551e357348de2b724737d569afd6ac9f5c3aa11
Reviewed-on: https://go-review.googlesource.com/108940
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:46:41 -06:00
|
|
|
// amd64:"BSFL","BTSL\\t\\$16"
|
2018-03-08 09:43:55 -07:00
|
|
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// s390x:"FLOGR","OR\t\\$65536"
|
2018-03-06 01:39:14 -07:00
|
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return bits.TrailingZeros16(n)
|
|
|
|
}
|
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|
|
|
|
func TrailingZeros8(n uint8) int {
|
cmd/compile: optimize TrailingZeros(8|16) on amd64
Introduce Ctz8 and Ctz16 ops and provide optimized lowerings for them.
amd64 only for this CL, although it wouldn't surprise me
if other architectures also admit of optimized lowerings.
name old time/op new time/op delta
TrailingZeros8-8 1.33ns ± 6% 0.84ns ± 3% -36.90% (p=0.000 n=20+20)
TrailingZeros16-8 1.26ns ± 5% 0.84ns ± 5% -33.50% (p=0.000 n=20+18)
Code:
func f8(x uint8) { z = bits.TrailingZeros8(x) }
func f16(x uint16) { z = bits.TrailingZeros16(x) }
Before:
"".f8 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) MOVBLZX AL, AX
0x0008 00008 (x.go:7) BTSQ $8, AX
0x000d 00013 (x.go:7) BSFQ AX, AX
0x0011 00017 (x.go:7) MOVL $64, CX
0x0016 00022 (x.go:7) CMOVQEQ CX, AX
0x001a 00026 (x.go:7) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:7) RET
"".f16 STEXT nosplit size=34 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) MOVWLZX AX, AX
0x0008 00008 (x.go:8) BTSQ $16, AX
0x000d 00013 (x.go:8) BSFQ AX, AX
0x0011 00017 (x.go:8) MOVL $64, CX
0x0016 00022 (x.go:8) CMOVQEQ CX, AX
0x001a 00026 (x.go:8) MOVQ AX, "".z(SB)
0x0021 00033 (x.go:8) RET
After:
"".f8 STEXT nosplit size=20 args=0x8 locals=0x0
0x0000 00000 (x.go:7) TEXT "".f8(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:7) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:7) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:7) MOVBLZX "".x+8(SP), AX
0x0005 00005 (x.go:7) BTSL $8, AX
0x0009 00009 (x.go:7) BSFL AX, AX
0x000c 00012 (x.go:7) MOVQ AX, "".z(SB)
0x0013 00019 (x.go:7) RET
"".f16 STEXT nosplit size=20 args=0x8 locals=0x0
0x0000 00000 (x.go:8) TEXT "".f16(SB), NOSPLIT, $0-8
0x0000 00000 (x.go:8) FUNCDATA $0, gclocals·2a5305abe05176240e61b8620e19a815(SB)
0x0000 00000 (x.go:8) FUNCDATA $1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
0x0000 00000 (x.go:8) MOVWLZX "".x+8(SP), AX
0x0005 00005 (x.go:8) BTSL $16, AX
0x0009 00009 (x.go:8) BSFL AX, AX
0x000c 00012 (x.go:8) MOVQ AX, "".z(SB)
0x0013 00019 (x.go:8) RET
Change-Id: I0551e357348de2b724737d569afd6ac9f5c3aa11
Reviewed-on: https://go-review.googlesource.com/108940
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Keith Randall <khr@golang.org>
2018-04-23 15:46:41 -06:00
|
|
|
// amd64:"BSFL","BTSL\\t\\$8"
|
2018-03-08 09:43:55 -07:00
|
|
|
// s390x:"FLOGR","OR\t\\$256"
|
2018-03-06 01:39:14 -07:00
|
|
|
return bits.TrailingZeros8(n)
|
|
|
|
}
|
2018-04-25 12:52:06 -06:00
|
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|
|
// IterateBitsNN checks special handling of TrailingZerosNN when the input is known to be non-zero.
|
|
|
|
|
|
|
|
func IterateBits(n uint) int {
|
|
|
|
i := 0
|
|
|
|
for n != 0 {
|
|
|
|
// amd64:"BSFQ",-"CMOVEQ"
|
|
|
|
i += bits.TrailingZeros(n)
|
|
|
|
n &= n - 1
|
|
|
|
}
|
|
|
|
return i
|
|
|
|
}
|
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|
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func IterateBits64(n uint64) int {
|
|
|
|
i := 0
|
|
|
|
for n != 0 {
|
|
|
|
// amd64:"BSFQ",-"CMOVEQ"
|
|
|
|
i += bits.TrailingZeros64(n)
|
|
|
|
n &= n - 1
|
|
|
|
}
|
|
|
|
return i
|
|
|
|
}
|
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|
|
|
|
|
|
func IterateBits32(n uint32) int {
|
|
|
|
i := 0
|
|
|
|
for n != 0 {
|
|
|
|
// amd64:"BSFL",-"BTSQ"
|
|
|
|
i += bits.TrailingZeros32(n)
|
|
|
|
n &= n - 1
|
|
|
|
}
|
|
|
|
return i
|
|
|
|
}
|
|
|
|
|
|
|
|
func IterateBits16(n uint16) int {
|
|
|
|
i := 0
|
|
|
|
for n != 0 {
|
|
|
|
// amd64:"BSFL",-"BTSL"
|
|
|
|
i += bits.TrailingZeros16(n)
|
|
|
|
n &= n - 1
|
|
|
|
}
|
|
|
|
return i
|
|
|
|
}
|
|
|
|
|
|
|
|
func IterateBits8(n uint8) int {
|
|
|
|
i := 0
|
|
|
|
for n != 0 {
|
|
|
|
// amd64:"BSFL",-"BTSL"
|
|
|
|
i += bits.TrailingZeros8(n)
|
|
|
|
n &= n - 1
|
|
|
|
}
|
|
|
|
return i
|
|
|
|
}
|