Meng Zhuo (Gerrit)

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Mar 12, 2025, 10:21:25 AM3/12/25

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internal/bytealg: vector implementation of count 1 byte for riscv64

This CL provide a vector implementation of count 1 byte

goos: linux
goarch: riscv64
pkg: bytes
cpu: Spacemit(R) X60
                │         sec/op         │   sec/op     vs base                │
CountSingle/10               42.12n ± 0%   44.49n ± 0%   +5.64% (p=0.000 n=10)
CountSingle/32               85.74n ± 0%   44.49n ± 0%  -48.11% (p=0.000 n=10)
CountSingle/4K              8371.5n ± 0%   396.7n ± 0%  -95.26% (p=0.000 n=10)
CountSingle/4M              8929.1µ ± 0%   756.9µ ± 0%  -91.52% (p=0.000 n=10)
CountSingle/64M             159.78m ± 0%   13.89m ± 0%  -91.30% (p=0.000 n=10)
geomean                      33.65µ        6.073µ       -81.95%

                │ /root/scalar_count.log │         /root/vector_count.log          │
                │          B/s           │      B/s       vs base                  │
CountSingle/10              226.4Mi ± 0%    214.3Mi ± 0%     -5.34% (p=0.000 n=10)
CountSingle/32              355.9Mi ± 0%    685.9Mi ± 0%    +92.71% (p=0.000 n=10)
CountSingle/4K              466.6Mi ± 0%   9846.5Mi ± 0%  +2010.19% (p=0.000 n=10)
CountSingle/4M              448.0Mi ± 0%   5284.9Mi ± 0%  +1079.74% (p=0.000 n=10)
CountSingle/64M             400.5Mi ± 0%   4606.2Mi ± 0%  +1049.98% (p=0.000 n=10)
geomean                     368.0Mi         1.991Gi        +454.08%

Change-Id: If88361e8fc2293fc73d4aa5d95903770516918f4

Change diff

diff --git a/src/internal/bytealg/count_riscv64.s b/src/internal/bytealg/count_riscv64.s
index 3f255cd..344427e 100644
--- a/src/internal/bytealg/count_riscv64.s
+++ b/src/internal/bytealg/count_riscv64.s
@@ -2,48 +2,53 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+#include "asm_riscv64.h"
 #include "go_asm.h"
 #include "textflag.h"
 
-TEXT ·Count<ABIInternal>(SB),NOSPLIT,$0-40
-	// X10 = b_base
-	// X11 = b_len
-	// X12 = b_cap (unused)
-	// X13 = byte to count (want in X12)
-	AND	$0xff, X13, X12
-	MOV	ZERO, X14	// count
-	ADD	X10, X11	// end
+TEXT ·Count<ABIInternal>(SB),NOSPLIT|NOFRAME,$0
+	MOV	X13, X12 // b_cap not used
+	JMP	count<>(SB)
 
-	PCALIGN	$16
-loop:
-	BEQ	X10, X11, done
-	MOVBU	(X10), X15
-	ADD	$1, X10
-	BNE	X12, X15, loop
-	ADD	$1, X14
-	JMP	loop
+TEXT ·CountString<ABIInternal>(SB),NOSPLIT|NOFRAME,$0
+	JMP	count<>(SB)
 
-done:
-	MOV	X14, X10
-	RET
-
-TEXT ·CountString<ABIInternal>(SB),NOSPLIT,$0-32
-	// X10 = s_base
+TEXT count<>(SB),NOSPLIT|NOFRAME,$0-0
+	// X10 = s_base, return as counter
 	// X11 = s_len
 	// X12 = byte to count
-	AND	$0xff, X12
-	MOV	ZERO, X14	// count
-	ADD	X10, X11	// end
+	MOV	X10, X14	// src pointer
+	MOV	ZERO, X10	// reset counter
+	AND	$0xff, X12, X12 // make sure it's a byte to compare
+	SUB	$8, X11, X5
+	BLEZ	X5, count_scalar
+#ifndef hasV
+	MOVB	internal∕cpu·RISCV64+const_offsetRISCV64HasV(SB), X5
+	BEQZ	X5, count_scalar
+#endif
+	PCALIGN	$16
+count_vector_loop:
+	VSETVLI	X11, E8, M8, TA, MA, X5
+	VLE8V	(X14), V8
+	VMSEQVX	X12, V8, V0
+	VCPOPM	V0, X15
+	ADD	X15, X10	// add counter
+	ADD	X5, X14
+	SUB	X5, X11, X11
+	BEQZ	X11, done
+	JMP	count_vector_loop
 
 	PCALIGN	$16
-loop:
-	BEQ	X10, X11, done
-	MOVBU	(X10), X15
-	ADD	$1, X10
-	BNE	X12, X15, loop
+count_scalar:
+	ADD	X14, X11	// end pointer
+	PCALIGN	$16
+count_scalar_loop:
+	BEQ	X14, X11, done
+	MOVBU	(X14), X15
 	ADD	$1, X14
-	JMP	loop
+	BNE	X12, X15, count_scalar_loop
+	ADD	$1, X10
+	JMP	count_scalar_loop
 
 done:
-	MOV	X14, X10
 	RET

Change information

Files:

M src/internal/bytealg/count_riscv64.s

Change size: M

Delta: 1 file changed, 37 insertions(+), 32 deletions(-)

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Meng Zhuo (Gerrit)

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Mar 13, 2025, 4:51:13 AM3/13/25

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Mark Ryan (Gerrit)

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Mar 13, 2025, 8:29:22 AM3/13/25

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Patchset-level comments

File-level comment, Patchset 1 (Latest):

Mark Ryan . unresolved

I tested this locally and it seems to work fine. I also see the expected speedups. We need to wait until https://go-review.googlesource.com/c/go/+/646779/6 and https://go-review.googlesource.com/c/go/+/646775/6 are merged before merging this.

File src/internal/bytealg/count_riscv64.s

Line 22, Patchset 1 (Latest): AND $0xff, X12, X12 // make sure it's a byte to compare

Mark Ryan . unresolved

AND $0xff, X12

Line 23, Patchset 1 (Latest): SUB $8, X11, X5

Mark Ryan . resolved

This looks a little low and the benchmarks in the commit message (the degradation in CountSingle/10) suggests that this might indeed be the case. However, I did benchmark this locally on a banana Pi with GORISCV64=rva23u64 and I didn't see any slowdown in CountSingle/10 so maybe it's okay.

Line 37, Patchset 1 (Latest): SUB X5, X11, X11

Mark Ryan . unresolved

SUB X5,X11

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Meng Zhuo (Gerrit)

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May 7, 2025, 3:39:34 AM5/7/25

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Meng Zhuo uploaded patch set #2 to this change.

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May 7, 2025, 3:41:58 AM5/7/25

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File-level comment, Patchset 1:

Mark Ryan . resolved

I tested this locally and it seems to work fine. I also see the expected speedups. We need to wait until https://go-review.googlesource.com/c/go/+/646779/6 and https://go-review.googlesource.com/c/go/+/646775/6 are merged before merging this.

Meng Zhuo

Also CL 646736, for hasV const.

File src/internal/bytealg/count_riscv64.s

Line 22, Patchset 1: AND $0xff, X12, X12 // make sure it's a byte to compare

Mark Ryan . resolved

AND $0xff, X12

Meng Zhuo

Done

Line 37, Patchset 1: SUB X5, X11, X11

Mark Ryan . resolved

SUB X5,X11

Meng Zhuo

Done

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File src/internal/bytealg/count_riscv64.s

Line 34, Patchset 3 (Latest): VMSEQVX X13, V8, V0

Pengcheng Wang . unresolved

We should avoid V0 here according to https://riscv-optimization-guide.riseproject.dev/#_avoid_using_v0_for_non_mask_operations.

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[go] internal/bytealg: vector implementation of count 1 byte for riscv64

Meng Zhuo (Gerrit)

Meng Zhuo has uploaded the change for review

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Change diff

Change information

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Meng Zhuo (Gerrit)

New activity on the change

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Mark Ryan (Gerrit)

Mark Ryan added 4 comments

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Meng Zhuo (Gerrit)

Meng Zhuo uploaded new patchset

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Meng Zhuo (Gerrit)

Meng Zhuo voted and added 3 comments

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3 comments

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Meng Zhuo (Gerrit)

Meng Zhuo voted Commit-Queue+1

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