Why is the performance of generic functions slightly worse in version 1.19?

Getting Help
1

Code

package main

import (
	"testing"
)

func Add[T int](a, b T) T {
	return a + b
}

func AddInterface(a, b interface{}) interface{} {
	return a.(int) + b.(int)
}

func AddInt(i, j int) int {
	return i + j
}

func BenchmarkAddGeneric(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = Add[int](i, i+1)
	}
}

func BenchmarkAddInterface(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = AddInterface(i, i+1)
	}
}

func BenchmarkAddInt(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = AddInt(i, i+1)
	}
}

go version go1.18.9 darwin/arm64

BenchmarkAddGeneric-10      	1000000000	         0.3187 ns/op
BenchmarkAddInterface-10    	1000000000	         0.3146 ns/op 
BenchmarkAddInt-10          	1000000000	         0.3162 ns/op

go version go1.19.9 darwin/arm64

BenchmarkAddGeneric-10      	1000000000	         0.9443 ns/op
BenchmarkAddInterface-10    	1000000000	         0.3174 ns/op
BenchmarkAddInt-10          	1000000000	         0.3143 ns/op

go version go1.20.5 darwin/arm64

BenchmarkAddGeneric-10      	1000000000	         0.3164 ns/op
BenchmarkAddInterface-10    	1000000000	         0.3152 ns/op
BenchmarkAddInt-10          	1000000000	         0.3162 ns/op
2

Hi @Ryo,

I can replicate your results, but I have no explanation. I would assume a bug in the runtime or the compiler that got fixed between 1.19.9 and 1.20.5.

3

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