英文:
Go compiler tricks
问题
我在一次讲座中读到，Go编译器会主动删除输出二进制文件中未使用的代码。这个讲座中提到了一些在测试中有用的代码添加方法，但我找不到这个讲座的具体信息。是否有人对这个工作原理有更多了解？是否有关于高级测试技术的讲座？
英文:
I read in a talk that the Go compiler will aggressively remove code that isn't used in the output binary. The talk which I can't find used this for adding some code useful to testing. Does anybody have more information on how this works? Are there talks on advanced testing techniques?
答案1
得分: 0
Dave Cheney在他的基准测试博客文章中谈到了这个问题：
http://dave.cheney.net/2013/06/30/how-to-write-benchmarks-in-go（关于编译器优化的说明）
英文:
Dave Cheney talks about this in his benchmark blog article:
http://dave.cheney.net/2013/06/30/how-to-write-benchmarks-in-go (A note on compiler optimisations)
答案2
得分: 0
【Go语言的五个加速要素】
【Dave Cheney】
死代码消除
func Test() bool { return false }
func Expensive() {
if Test() {
// something expensive
}
}
在这个例子中，尽管函数Test总是返回false，但Expensive函数在不执行Test的情况下无法知道这一点。
当Test函数被内联时，我们得到以下代码：
func Expensive() {
if false {
// something expensive is
// now unreachable
}
}
编译器现在知道这段昂贵的代码是不可达的。
这不仅节省了调用Test的成本，还节省了编译或运行任何现在不可达的昂贵代码的成本。
例如，添加一些对测试有用的代码：
func Complicated() {
if Test() {
// something for testing
}
}
将Test从
func Test() bool { return false }
内联后
func Complicated() {
if false {
// something for testing
// unreachable
}
}
变为
func Test() bool { return true }
内联后
func Complicated() {
if true {
// something for testing
// reachable
}
}
可以用于包含仅用于测试的代码。
【1】：Go语言的五个加速要素
【2】：Dave Cheney
英文:
> Five things that make Go fast
>
> Dave Cheney
>
> Dead Code Elimination
>
> func Test() bool { return false }
>
> func Expensive() {
> if Test() {
> // something expensive
> }
> }
>
> In this example, although the function Test always returns false,
> Expensive cannot know that without executing it.
>
> When Test is inlined, we get something like this
>
> func Expensive() {
> if false {
> // something expensive is
> // now unreachable
> }
> }
>
> The compiler now knows that the expensive code is unreachable.
>
> Not only does this save the cost of calling Test, it saves compiling
> or running any of the expensive code that is now unreachable.
For example, adding some code useful to testing,
func Complicated() {
if Test() {
// something for testing
}
}
Switching Test from
func Test() bool { return false }
inlined
func Complicated() {
if false {
// something for testing
// unreachable
}
}
to
func Test() bool { return true }
inlined
func Complicated() {
if true {
// something for testing
// reachable
}
}
can be useful to include code just for testing.
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