mirror of
https://github.com/golang/go
synced 2024-11-23 06:00:08 -07:00
304f769ffc
Current optimization: When we copy a->b and then b->c, we might as well copy a->c instead of b->c (then b might be dead and go away). *Except* if a is a volatile location (might be clobbered by a call). In that case, we really do want to copy a immediately, because there might be a call before we can do the a->c copy. User calls can't happen in between, because the rule matches up the memory states. But calls inserted for memory barriers, particularly runtime.typedmemmove, can. (I guess we could introduce a register-calling-convention version of runtime.typedmemmove, but that seems a bigger change than this one.) Fixes #43570 Change-Id: Ifa518bb1a6f3a8dd46c352d4fd54ea9713b3eb1a Reviewed-on: https://go-review.googlesource.com/c/go/+/282492 Trust: Keith Randall <khr@golang.org> Trust: Josh Bleecher Snyder <josharian@gmail.com> Run-TryBot: Keith Randall <khr@golang.org> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
41 lines
661 B
Go
41 lines
661 B
Go
// run
|
|
|
|
// Copyright 2021 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package main
|
|
|
|
import "fmt"
|
|
|
|
type T [8]*int
|
|
|
|
//go:noinline
|
|
func f(x int) T {
|
|
return T{}
|
|
}
|
|
|
|
//go:noinline
|
|
func g(x int, t T) {
|
|
if t != (T{}) {
|
|
panic(fmt.Sprintf("bad: %v", t))
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
const N = 10000
|
|
var q T
|
|
func() {
|
|
for i := 0; i < N; i++ {
|
|
q = f(0)
|
|
g(0, q)
|
|
sink = make([]byte, 1024)
|
|
}
|
|
}()
|
|
// Note that the closure is a trick to get the write to q to be a
|
|
// write to a pointer that is known to be non-nil and requires
|
|
// a write barrier.
|
|
}
|
|
|
|
var sink []byte
|