On Thu, Feb 12, 2009 at 1:32 AM, Andreas Raab andreas.raab@gmx.de wrote:
Folks -
Has anyone tried porting the FFI to 64 bit? I'm loosely considering using a 64bit VM for our servers but I do need the FFI (mostly for ODBC integration) and I've never looked at any of the ABIs. Alternatively, is it reasonable to try to use 64bit libs from within a 32bit Squeak VM?
Depends on what one wants to pass through the FFI. On x86-64/EMT64 structure passing conventions are efficient and complex, distributing structure fields across integer and floating-point registers. It is possible to interpret such calls given a type signature for the structure to be passed (I did it for VisualWorks) but it is not easy and it is slow. I would counsel writing a proper ABI compiler in Smalltalk that generates e.g. RTL that is either interpreted or compiled by the VM to make the actual call.
In theory the use of 64-bit libs, provided one has the relevant FFI support should work fine. Smalltalk has the ability to deal with 64-bit and 128-bit values easily. But one does have to write all the support.
To get acquainted with the de facto standard x86-64 ABI read the System V Application Binary Interface AMD64 Architecture Processor Supplement http://www.x86-64.org/documentation/abi-0.98.pdf pages 13 through 22 (section Function Calling Sequence) paying particular attention to the 3 1/2 page algorithm for marshalling :)
and start going to bed earlier ;)
Thanks for any info!
Cheers,
- Andreas