Hi All,
I hope I can clear up some confusion as to the status of ARMv8/aarch64 support in the opensmalltalk-vm.
Executive summary: ARMv8 stack and cog VMs fully functional on e.g. Raspberry Pi 4, except for a special case in the FFI (structs containing all floats). The stack interpreter is functional on beta Apple Silicon. Work is in progress to get the Cogit VM working there-on.
Gory details:
The core VM works in both stack and cogit versions. A bug with integer multip-ly was fixed in early June that fixed bugs that appeared to be in large integer arithmetic (e.g. 100 factorial answered an incorrect value_. This bug was due to the Cogit not generating code that checked for overflow in integer multiple, and this was due to my having not noticed that ARMv8 does not set the overflow flag for integer multiple. The fix was to generate a proper checking sequence (the upper 64 bits of a 64x64=>128 bit multiply should be 0 or all ones).
The major known bug is in the FFI. The ARMv8 procedure calling standard defines Homogenous Floating Aggregates (HFAs) and Homogenous Vector Aggregates (HVAs). The former are e.g. C structs whose components are all floats or all doubles. The latter are structs whose components are all the same and of two to four scalar data types. If argument registers are available then values of these types will be passed *and* returned in registers.
The bug is that the ThreadedARMv8Plgin does not currently implement this mapping for floating-point values. This manifests in 6 ffi tests failing and two generating errors (provided the -failonffiexception VM argument is used; if it is not supplied, the VM crashes). While I don't have time to work on this at the moment, I'm sure that either Nicolas or myself will get to this before too long. But if your interface does not use HFAs or HVAs we believe the FFI is functional.
Fabio and I are currently working on Apple Silicon support, very much in our spare time. Apple Silicon is the same Apple gives to its own ARMv8 implementation, the A12 (used in beta macos hardware) and the A13. Currently we have the stack interpreter working, but not the Cogit. The issue right now is getting the lldb debugger to debug the Cogit so we can correctly set up memory at startup, Apple having introduced, or rather ported, the iPhone security architecture to MacOS, meaning that jitting code and debugging are carefully controlled actions that need :entitlements" setting in an executable. So far I *think* the entitlements are being set correctly, but for some reason lldb is still not able to launch or attach to either the stack or the cog VMs. So while we're stuck at the moment, Apple is quite responsive in its beta programme and I'm two messages deep in the exchange on getting lldb to work. So I expect progress soon.
Locked
