From 2cdcc4150bc577e0b40a9cedaaa7c8301f2860cd Mon Sep 17 00:00:00 2001
From: Meng Zhuo <mengzhuo@iscas.ac.cn>
Date: Fri, 14 Nov 2025 12:47:35 +0800
Subject: cmd/compile: fold negation into multiplication
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goos: linux
goarch: riscv64
pkg: cmd/compile/internal/test
cpu: Spacemit(R) X60
        │ /root/mul.base.log │          /root/mul.new.log          │
        │       sec/op       │   sec/op     vs base                │
MulNeg           6.426µ ± 0%   4.501µ ± 0%  -29.96% (p=0.000 n=10)
Mul2Neg          9.000µ ± 0%   6.431µ ± 0%  -28.54% (p=0.000 n=10)
Mul2             1.263µ ± 0%   1.263µ ± 0%        ~ (p=1.000 n=10)
MulNeg2          1.577µ ± 0%   1.577µ ± 0%        ~ (p=0.211 n=10)
geomean          3.276µ        2.756µ       -15.89%

goos: linux
goarch: amd64
pkg: cmd/compile/internal/test
cpu: AMD EPYC 7532 32-Core Processor
        │ /root/base  │              /root/new              │
        │   sec/op    │   sec/op     vs base                │
MulNeg    691.9n ± 1%   319.4n ± 0%  -53.83% (p=0.000 n=10)
Mul2Neg   630.0n ± 0%   629.6n ± 0%   -0.07% (p=0.000 n=10)
Mul2      438.1n ± 0%   438.1n ± 0%        ~ (p=0.728 n=10)
MulNeg2   439.3n ± 0%   439.4n ± 0%        ~ (p=0.656 n=10)
geomean   538.2n        443.6n       -17.58%

Change-Id: Ice8e6c8d1e8e3009ba8a0b1b689205174e199019
Reviewed-on: https://go-review.googlesource.com/c/go/+/720180
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>
---
 test/codegen/arithmetic.go | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

(limited to 'test/codegen')

diff --git a/test/codegen/arithmetic.go b/test/codegen/arithmetic.go
index 42d5d2ef65..6b2c5529e1 100644
--- a/test/codegen/arithmetic.go
+++ b/test/codegen/arithmetic.go
@@ -318,13 +318,19 @@ func MergeMuls5(a, n int) int {
 // Multiplications folded negation
 
 func FoldNegMul(a int) int {
-	// loong64:"SUBVU" "ALSLV [$]2" "ALSLV [$]1"
-	return (-a) * 11
+	// amd64:"IMUL3Q [$]-11" -"NEGQ"
+	// arm64:"MOVD [$]-11" "MUL" -"NEG"
+	// loong64:"ALSLV [$]2" "SUBVU" "ALSLV [$]4"
+	// riscv64:"MOV [$]-11" "MUL" -"NEG"
+	return -a * 11
 }
 
 func Fold2NegMul(a, b int) int {
+	// amd64:"IMULQ" -"NEGQ"
+	// arm64:"MUL" -"NEG"
 	// loong64:"MULV" -"SUBVU R[0-9], R0,"
-	return (-a) * (-b)
+	// riscv64:"MUL" -"NEG"
+	return -a * -b
 }
 
 // -------------- //
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