How is first function called?

[Arpit Aggarwal]

Hi Andrew,
Can you please tell me how the first function called in LLVM IR.
I just printed the control flow graph for the following go program using its LLVM IR produced through llgo

package main
func add(x int, y int) int {
    return x + y
}
func main(){
  x:=5
  y:=10
  y=add(x,y)
}

Can you please explain me a little about this external variable and how is the first function being called?
How is main.main called?
I have also attached the LLVM IR file (readable).

Thanks a lot in advance.

Regards
Arpit

[Andrew Wilkins]

On Mon, 22 May 2017 at 02:53 Arpit Aggarwal <arpit9...@gmail.com> wrote:

Hi Andrew,
Can you please tell me how the first function called in LLVM IR.
I just printed the control flow graph for the following go program using its LLVM IR produced through llgo

package main
func add(x int, y int) int {
    return x + y
}
func main(){
  x:=5
  y:=10
  y=add(x,y)
}

Can you please explain me a little about this external variable and how is the first function being called?
How is main.main called?

llgo uses the libgo runtime from gofrontend/gccgo, which takes care of the process startup: it defines the entry point that (indirectly) calls through to the "main" function, defined in the libgo runtime:

    https://github.com/llvm-mirror/llgo/blob/master/third_party/gofrontend/libgo/runtime/go-main.c#L36

That calls runtime_main, which does some initialisation and then calls main.main:

    https://github.com/llvm-mirror/llgo/blob/master/third_party/gofrontend/libgo/runtime/proc.c#L626

Cheers,

Andrew

I have also attached the LLVM IR file (readable).

Thanks a lot in advance.

Regards
Arpit

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[Arpit Aggarwal]

Thanks a lot Andrew.

Regards
Arpit