Hello gophers,
Does Go compiler has some optimizations for function and *method* calls
with `variadic` arguments? For example, this simple benchmark:
```
package main
import "testing"
func Do(xs ...int) (s int) {
for i, x := range xs {
s += i + x
}
return s
}
func BenchmarkDo(b *testing.B) {
for i := 0; i < b.N; i++ {
Do(i, i, i, i)
}
}
```
Provides these results:
```
BenchmarkDo-8 300000000 4.29 ns/op 0 B/op 0 allocs/op
```
That is, no allocation for slice of arguments is done. I may assume that
it is made by preparing `xs` slice on stack of `Do()`.
But, this example:
```
package main
import "testing"
type Doer interface {
Do(...int) int
}
type impl struct {}
func (impl) Do(xs ...int) (s int) {
for i, x := range xs {
s += i + x
}
return s
}
func BenchmarkDo(b *testing.B) {
var d Doer = impl{}
for i := 0; i < b.N; i++ {
d.Do(i, i, i, i)
}
}
```
Provides different results:
```
BenchmarkDo-8 300000000 25.8 ns/op 32 B/op 1 allocs/op
```
That is, I assume that this allocation is made for the slice of arguments.
Also, I may assume that this because the compiler does not knows exactly
which function it will call in a runtime.
Am I understand it right and are there any plans for preparing such
optimizations?
Regards,
Sergey.
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