go tool compile称为编译命令，用来生成对象文件，生成对象文件最后通过go tool link命令链接成可执行文件。
编译命名用法示例如下：
go tool compile [flags] file...
在使用编译命令时候，我们可以设置GOOS 和 GOARCH环境变量来指定目标操作系统和系统架构。这个和go build命令是一致的。
go tool compile支持的选项有：
| 选项 | 说明 |
|---|---|
| -D path | Set relative path for local imports. |
| -I dir1 -I dir2 | Search for imported packages in dir1, dir2, etc, after consulting $GOROOT/pkg/$GOOS_$GOARCH. |
| -L | Show complete file path in error messages. |
| -N | Disable optimizations. |
| -S | Print assembly listing to standard output (code only). |
| -S -S | Print assembly listing to standard output (code and data). |
| -V | Print compiler version and exit. |
| -asmhdr file | Write assembly header to file. |
| -asan | Insert calls to C/C++ address sanitizer. |
| -buildid id | Record id as the build id in the export metadata. |
| -blockprofile file | Write block profile for the compilation to file. |
| -c int | Concurrency during compilation. Set 1 for no concurrency (default is 1). |
| -complete | Assume package has no non-Go components. |
| -cpuprofile file | Write a CPU profile for the compilation to file. |
| -dynlink | Allow references to Go symbols in shared libraries (experimental). |
| -e | Remove the limit on the number of errors reported (default limit is 10). |
| -goversion string | Specify required go tool version of the runtime. Exits when the runtime go version does not match goversion. |
| -h | Halt with a stack trace at the first error detected. |
| -importcfg file | Read import configuration from file. In the file, set importmap, packagefile to specify import resolution. |
| -installsuffix suffix | Look for packages in $GOROOT/pkg/$GOOS_$GOARCH_suffix instead of $GOROOT/pkg/$GOOS_$GOARCH. |
| -l | Disable inlining. |
| -lang version | Set language version to compile, as in -lang=go1.12. Default is current version. |
| -linkobj file | Write linker-specific object to file and compiler-specific object to usual output file (as specified by -o). Without this flag, the -o output is a combination of both linker and compiler input. |
| -m | Print optimization decisions. Higher values or repetition produce more detail. |
| -memprofile file | Write memory profile for the compilation to file. |
| -memprofilerate rate | Set runtime.MemProfileRate for the compilation to rate. |
| -msan | Insert calls to C/C++ memory sanitizer. |
| -mutexprofile file | Write mutex profile for the compilation to file. |
| -nolocalimports | Disallow local (relative) imports. |
| -o file | Write object to file (default file.o or, with -pack, file.a). |
| -p path | Set expected package import path for the code being compiled, and diagnose imports that would cause a circular dependency. |
| -pack | Write a package (archive) file rather than an object file |
| -race | Compile with race detector enabled. |
| -s | Warn about composite literals that can be simplified. |
| -shared | Generate code that can be linked into a shared library. |
| -spectre list | Enable spectre mitigations in list (all, index, ret). |
| -traceprofile file | Write an execution trace to file. |
| -trimpath prefix | Remove prefix from recorded source file paths. |
Go 编译器可以读取来自注释里面的指令，这些指令称为编译指令，这些编译指令往往以//go:开头。
由于历史缘故，line指令并不是由//go:开头。它通常出现在机器码生成时候，这样编译器或者调试器才能报告出原始输入文件的位置。比如查看cgo编译过程中的中间文件会出现(go tool cgo xxx.go)。
noescape = no + escape。noescape意味着禁止逃逸，该编译指令后面必须跟着函数声明(没有函数体)。该函数的具体实现是由汇编实现的。
该指令后面必须跟一个函数声明。它表明该函数的 uintptr 参数是一个指针指，需要将其分配到堆上，来保证调用期间不被回收，造成悬挂现象。
//go:noinline 指令后面必须跟一个函数定义。它指定不对该函数进行内联优化。这通常仅在特殊运行时函数或调试编译器时需要。
//go:noinline
func add(a, b int) int {
return a + b
}
func main() {
c := add(3, 5)
fmt.Println(c)
}内联优化的优点：
- 减少函数调用的开销，提高执行速度，毕竟call指令是比较耗时的。
- 消除分支，并改善空间局部性和指令顺序性，同样可以提高性能
内联优化并不是银弹，如果有大量重复代码，反而会降低CPU缓存命中率。需要注意的是Go编译器没有强制使用内联优化的编译指令。
该指令后面必须跟一个函数声明。它指定函数的内存访问必须被竞争检测器忽略。这最常用于在调用竞争检测器运行时不安全时调用的低级代码。
该指令后面必须跟一个函数声明。它指定函数必须省略其通常的堆栈溢出检查。当调用 goroutine 被抢占是不安全的时候，这最常被调用的低级运行时代码使用。
Go中gorountine的栈初始大小为2K，正常情况下每个函数最开始部分都有一个堆栈检测的序言指令，执行函数前检查goroune栈是否需要扩容。
该指令用来将源代码localname符号链接到源代码中的importpath.name符号。由于该指令破坏了类型系统和软件包的模块化，因此使用的时候，需要导入unsafe包。
import "unsafe"
//go:linkname zerobase runtime.zerobase
var zerobase uintptr // 使用go:linkname编译指令，将zerobase变量指向runtime.zerobase该指令是用于构建约束(build constraint)，它是在Go1.17版本中引入，之前版本都是通过+build来实现的。Go1.17中，为了兼容性，两者都需要保留，否则编译不通过。
//go:build linux && 386
// +build linux,386
func add(a, b int) int {
return a + b
}