易于阅读的Golang汇编输出？

Question

I'm interested in examining the x86 assembly output of the standard Go compiler to see if my code is really being converted into reasonably efficient assembly code; hopefully, by profiling and examining the assembly output, I could get a clue as to where/how I should rewrite my Go code for maximum performance. But when I examine the code using the -S flag, Go spits out a mess! I'd like two things:

1. Is there a way to make the Go compiler dump the assembly output into a file, not just print it out on Terminal?

2. Also, is there a way to make the Go compiler separate out the assembly code into separate functions, with labels? I know some functions may be inlined and hence not appear in the assembly code. What I'm seeing know is just a homogenous blob of assembly which is almost impossible to understand.

Answer 1

1. You can redirect the output to a file like this:

   go tool 6g -S file.go > file.s
   

2. You can disable the optimization with -N:

   go tool 6g -S -N file.go
   

Alternatively, you can use gccgo:

gccgo -S -O0 -masm=intel test.go

which will generate test.s. You can play with the -O0/1/2/3 to see the different optimizations.