math/big: optimize mulAddVWW on arm64 for better performance
Unroll the cycle 4 times to reduce load overhead.
Benchmarks:
name old time/op new time/op delta
MulAddVWW/1-8 15.9ns ± 0% 11.9ns ± 0% -24.92% (p=0.000 n=8+8)
MulAddVWW/2-8 16.1ns ± 0% 13.9ns ± 1% -13.82% (p=0.000 n=8+8)
MulAddVWW/3-8 18.9ns ± 0% 17.3ns ± 0% -8.47% (p=0.000 n=8+8)
MulAddVWW/4-8 21.7ns ± 0% 19.5ns ± 0% -10.14% (p=0.000 n=8+8)
MulAddVWW/5-8 25.1ns ± 0% 22.5ns ± 0% -10.27% (p=0.000 n=8+8)
MulAddVWW/10-8 41.6ns ± 0% 40.0ns ± 0% -3.79% (p=0.000 n=8+8)
MulAddVWW/100-8 368ns ± 0% 363ns ± 0% -1.36% (p=0.000 n=8+8)
MulAddVWW/1000-8 3.52µs ± 0% 3.52µs ± 0% -0.14% (p=0.000 n=8+8)
MulAddVWW/10000-8 35.1µs ± 0% 35.1µs ± 0% -0.01% (p=0.000 n=7+6)
MulAddVWW/100000-8 351µs ± 0% 351µs ± 0% +0.15% (p=0.038 n=8+8)
Change-Id: I052a4db286ac6e4f3293289c7e9a82027da0405e
Reviewed-on: https://go-review.googlesource.com/c/go/+/155780
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
diff --git a/src/math/big/arith_arm64.s b/src/math/big/arith_arm64.s
index bb23751..114d5f6 100644
--- a/src/math/big/arith_arm64.s
+++ b/src/math/big/arith_arm64.s
@@ -363,16 +363,51 @@
MOVD x+24(FP), R2
MOVD y+48(FP), R3
MOVD r+56(FP), R4
+ // c, z = x * y + r
+ TBZ $0, R0, two
+ MOVD.P 8(R2), R5
+ MUL R3, R5, R7
+ UMULH R3, R5, R8
+ ADDS R4, R7
+ ADC $0, R8, R4 // c, z[i] = x[i] * y + r
+ MOVD.P R7, 8(R1)
+ SUB $1, R0
+two:
+ TBZ $1, R0, loop
+ LDP.P 16(R2), (R5, R6)
+ MUL R3, R5, R10
+ UMULH R3, R5, R11
+ ADDS R4, R10
+ MUL R3, R6, R12
+ UMULH R3, R6, R13
+ ADCS R12, R11
+ ADC $0, R13, R4
+
+ STP.P (R10, R11), 16(R1)
+ SUB $2, R0
loop:
CBZ R0, done
- MOVD.P 8(R2), R5
- UMULH R5, R3, R7
- MUL R5, R3, R6
- ADDS R4, R6
- ADC $0, R7
- MOVD.P R6, 8(R1)
- MOVD R7, R4
- SUB $1, R0
+ LDP.P 32(R2), (R5, R6)
+ LDP -16(R2), (R7, R8)
+
+ MUL R3, R5, R10
+ UMULH R3, R5, R11
+ ADDS R4, R10
+ MUL R3, R6, R12
+ UMULH R3, R6, R13
+ ADCS R11, R12
+
+ MUL R3, R7, R14
+ UMULH R3, R7, R15
+ ADCS R13, R14
+ MUL R3, R8, R16
+ UMULH R3, R8, R17
+ ADCS R15, R16
+ ADC $0, R17, R4
+
+ STP.P (R10, R12), 32(R1)
+ STP (R14, R16), -16(R1)
+ SUB $4, R0
B loop
done:
MOVD R4, c+64(FP)
diff --git a/src/math/big/arith_test.go b/src/math/big/arith_test.go
index 8a64321..d28f680 100644
--- a/src/math/big/arith_test.go
+++ b/src/math/big/arith_test.go
@@ -371,6 +371,24 @@
}
}
+func BenchmarkMulAddVWW(b *testing.B) {
+ for _, n := range benchSizes {
+ if isRaceBuilder && n > 1e3 {
+ continue
+ }
+ z := make([]Word, n+1)
+ x := rndV(n)
+ y := rndW()
+ r := rndW()
+ b.Run(fmt.Sprint(n), func(b *testing.B) {
+ b.SetBytes(int64(n * _W))
+ for i := 0; i < b.N; i++ {
+ mulAddVWW(z, x, y, r)
+ }
+ })
+ }
+}
+
func BenchmarkAddMulVVW(b *testing.B) {
for _, n := range benchSizes {
if isRaceBuilder && n > 1e3 {
