[go-nuts] Unexported assembly function help

On Thu, Jun 6, 2013 at 1:04 PM, Jay Weisskopf wrote:
I cannot find any official documentation on how to write assembly functions
with a Go fallback. Based on what I can see in the standard library, the
convention goes something like this:

foo.go
------

func Foo(int) int // Defined in assembly

func foo(int) int { // Fallback version in Go
// ...
return 0
}


foo_GOARCH.s
------------

// func Foo(int) int
TEXT ·Foo(SB),7,$0
// ...
RET


Questions:

1) How does foo() actually get associated with Foo()? Does the tooling just
automatically look for a lowercase version? When I remove the assembly file,
I get a "missing function body" error, so there must be something about the
standard library examples.

On Thu, Jun 6, 2013 at 1:45 PM, Jay Weisskopf wrote:
Thanks. It seems much clearer to me after reading that. I was getting mixed
up about the fallback thing because I was previously looking at Sqrt, which
provides an implementation for each arch, while there also exists a full
sqrt() in Go, and I thought there was some kind of association. Maybe not in
that case.

So I should have all my bases covered (for now) so long as I provide a 386,
arm, and amd64 version? That is everything I see in the math package.

On 07/06/2013, at 6:04, Jay Weisskopf wrote:

I cannot find any official documentation on how to write assembly functions with a Go fallback. Based on what I can see in the standard library, the convention goes something like this:

foo.go
------
func Foo(int) int // Defined in assembly

func foo(int) int { // Fallback version in Go
// ...
return 0
}

foo_GOARCH.s
------------
// func Foo(int) int
TEXT ·Foo(SB),7,$0
// ...
RET

Questions:

1) How does foo() actually get associated with Foo()? Does the tooling just automatically look for a lowercase version? When I remove the assembly file, I get a "missing function body" error, so there must be something about the standard library examples.

2) Is it possible to create an unexported function like this? If the optimized function is now called foo(), what does the fallback get named?

3) Is the commented out func signature in the assembly file required by the tools or have any significance? I think I found that it didn't work without it.

Thanks,
Jay
--
You received this message because you are subscribed to the Google Groups "golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
For more options, visit https://groups.google.com/groups/opt_out.