mirror of
https://github.com/golang/go
synced 2024-09-04 23:44:16 +00:00
![philhofer](/assets/img/avatar_default.png)
With this change, code like h := sha1.New() h.Write(buf) sum := h.Sum() gets compiled into static calls rather than interface calls, because the compiler is able to prove that 'h' is really a *sha1.digest. The InterCall re-write rule hits a few dozen times during make.bash, and hundreds of times during all.bash. The most common pattern identified by the compiler is a constructor like func New() Interface { return &impl{...} } where the constructor gets inlined into the caller, and the result is used immediately. Examples include {sha1,md5,crc32,crc64,...}.New, base64.NewEncoder, base64.NewDecoder, errors.New, net.Pipe, and so on. Some existing benchmarks that change on darwin/amd64: Crc64/ISO4KB-8 2.67µs ± 1% 2.66µs ± 0% -0.36% (p=0.015 n=10+10) Crc64/ISO1KB-8 694ns ± 0% 690ns ± 1% -0.59% (p=0.001 n=10+10) Adler32KB-8 473ns ± 1% 471ns ± 0% -0.39% (p=0.010 n=10+9) On architectures like amd64, the reduction in code size appears to contribute more to benchmark improvements than just removing the indirect call, since that branch gets predicted accurately when called in a loop. Updates #19361 Change-Id: I57d4dc21ef40a05ec0fbd55a9bb0eb74cdc67a3d Reviewed-on: https://go-review.googlesource.com/38139 Run-TryBot: Philip Hofer <phofer@umich.edu> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Chase <drchase@google.com>
40 lines
599 B
Go
40 lines
599 B
Go
// errorcheck -0 -d=ssa/opt/debug=3
|
|
|
|
package main
|
|
|
|
// Trivial interface call devirtualization test.
|
|
|
|
type real struct {
|
|
value int
|
|
}
|
|
|
|
func (r *real) Value() int { return r.value }
|
|
|
|
type Valuer interface {
|
|
Value() int
|
|
}
|
|
|
|
type indirectiface struct {
|
|
a, b, c int
|
|
}
|
|
|
|
func (i indirectiface) Value() int {
|
|
return i.a + i.b + i.c
|
|
}
|
|
|
|
func main() {
|
|
var r Valuer
|
|
rptr := &real{value: 3}
|
|
r = rptr
|
|
|
|
if r.Value() != 3 { // ERROR "de-virtualizing call$"
|
|
panic("not 3")
|
|
}
|
|
|
|
// Can't do types that aren't "direct" interfaces (yet).
|
|
r = indirectiface{3, 4, 5}
|
|
if r.Value() != 12 {
|
|
panic("not 12")
|
|
}
|
|
}
|