So I guess its not in the open right now.
I wonder if its going to be specific to their chips, because the Xtensa architecture is highly configurable and so there isn't really a single target, but potentially many.
So I imagine there would be lots of nice maker opportunities when that support comes out, not only for Rust, but for other LLVM frontends as well.
I noticed whilst writing a verilog implementation - seeing the @PC+ relative modes for immediate data made me dig out my PDP-11 reference card.
The number of addressing modes has been halved, gaining a bit for register encoding, and the status register is now in the register file (R2), and R3 is used to generate various constants depending on mode.
Compare and contrast:
* https://en.wikipedia.org/wiki/PDP-11_architecture#CPU_regist... * https://en.wikipedia.org/wiki/TI_MSP430#MSP430_CPU
Accepts a .hex so you can use whatever toolchain you want.
MSP430 support is HUGE. In case you don't know, that's a well-known very low-power microcontroller.
edit: this might be the only current platform that's <32 bits. I know there was some work on supporting the 8-bit AVR architecture, but MSP430 gets rust a lot closer to super-low-power applications.