Exploring escape analysis in Go

escape_analysis_test.go

package main

import (
	"fmt"
	"strconv"
	"testing"
)

type Int int

func (i Int) String() string {
	return strconv.Itoa(int(i))
}

type Int2 int

func (i *Int2) String() string {
	return strconv.Itoa(int(*i))
}

func BenchmarkEscapeInterface(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var i Int = 10
		var s fmt.Stringer = i
		s.String()
	}
}

func BenchmarkEscapeConcreteValue(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var i Int = 10
		i.String()
	}
}

func BenchmarkEscapeConcretePointer(b *testing.B) {
	for i := 0; i < b.N; i++ {
		var i Int2 = 10
		i.String()
	}
}

func sum() int {
	var ints [10]int
	for i := 0; i < len(ints); i++ {
		ints[0] = i + 1
	}
	sum := 0
	for _, x := range ints {
		sum += x
	}
	return sum
}

func BenchmarkEscapeArray(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = sum()
	}
}

type Inner struct {
	Slice  []int
	String string
	Int    int
}

type Struct struct {
	Int    int
	String string
	Nested Inner
}

func (s Struct) AddThings() int {
	return s.Int + len(s.String) + len(s.Nested.Slice) + len(s.Nested.String) +
		s.Nested.Int
}

func BenchmarkEscapeStruct(b *testing.B) {
	for i := 0; i < b.N; i++ {
		s := Struct{
			Int:    42,
			String: "Hello",
			Nested: Inner{
				Slice:  []int{0, 1, 2},
				String: "World!",
				Int:    42,
			},
		}
		_ = s.AddThings()
	}
}