Re: [Caml-list] Closing the performance gap to C

[Alain Frisch <alain.frisch@lexifi.com>]

On 21/12/2016 15:45, Yotam Barnoy wrote:
> I think it's not worth the effort. You need to examine all the code
> dealing with a parameter (ie. its flow) to see if any generic function
> is called on that parameter.

This would be treated a bit like the stubs for optional arguments with a 
default value.  Any function taking float arguments or returning a float 
would be compiled to a specialized version with an unboxed calling 
convention plus a stub which implements the generic calling convention 
and delegate the call to the specialized version (or copy its body if it 
is small enough).  On call site, when the called function is known, one 
calls the specialized version instead.  This is a systematic, local 
compilation scheme, similar to other optimizations made in 
closure/cmmgen; it does not require a more global analysis nor a 
radically different representation of the code.

About the "it's not worth the effort": the effort has largely been done, 
since the ticket came with a working patch (some more effort would be 
needed to bring it up to date, though).  In my opinion, this seems like 
a rather low-hanging fruit with very immediate and significant gains. 
I'd rather have this soon than wait for flambda to become stable and 
usable on large projects.



-- Alain