If the compiler in question supports the #line directive, it might not be too bad.
ARM controllers are (relatively) uniform and the svd files do a lot of the work by providing the mapping for the memory mapped peripherals.
Across other devices it becomes even more complicated. AVR devices, AFAIK, are not providing memory mapped flash. There are also differences in byte v page erasable flash and eeprom. How would something like this map to Rust? I don't know and I'm honestly skeptical of the practical use but there is a quite serious effort put into making the AVR backend for LLVM ready for use.
---
It really makes me wonder a lot about "embedded" programming and where it is heading. If I were to bet I'd say that there is a significant movement to employ more and more powerful "microcontrollers" in order to allow remove all the resource constraints typically associated with "embedded" programming.
Stuff like Esprino, MicroPython, huge layers of abstraction etc. are today kind of nice tools for learning and starting out -- but give it a few years and somebody will ship a successful product build around this. It doesn't matter that the BOM cost is higher, the current draw is larger and the complexity and security understanding decreased -- it enables a faster time to market and in the end that is what makes the business.
The same is happening in FPGA development.
The old-fashioned hardware folks say that "not how it's done" -- myself included. But you know what they say:
> When the wind of change blows, some build walls, while others build windmills.
I think consumers are still going to be cost-sensitive in quite a few markets so BOM will still be critical. I'd argue you're already seeing this with more than a few companies using Android + mid-tier ARMs when market time matters more than final cost.
There's probably just going to be less people that know how to do it, much in the same way native programming is today.
What?
Sure, the core is relatively uniform, but the peripherals are radically different between manufacturers.
If you look at a die photo and see what area goes to what, pretty quickly you conclude all microcontroller makers are just selling value-added flash memory.
https://semiengineering.com/mcu-sales-up-in-2017-and-2018/
As vvanders says, the hard data shows plenty of the market is still maximizing profit by using 8-bitters (33%) and 16-bitters (26%). That's a combined 59% of microcontrollers a 32-/64-bit-only language would be leaving on the table in terms of deployment. Even ATS language, much more difficult than Rust, has already been deployed on 8-bitters.
http://metasepi.org/doc/metasepi-icfp2015-arduino-ats.pdf
Hopefully, Rust stays adding whatever features are necessary to support this stuff. If not, the Haskell crowd can always grab it up with DSL's like Ivory:
https://ivorylang.org/ivory-introduction.html
EDIT to add: A link about 4-bit MCU market that still exists for anyone wondering what that part of the pie chart was about.
Sure, a 32-bit chip is bound to be bigger than an equivalent 8 or 16-bit one, but e.g. the pulpino project has designed a 32-bit one using only 11.6 kGE. Not very much nowadays. For comparison, according to someone from Atmel, the AVR core is 12k gates, and megaAVR is 20k gates (https://www.embeddedrelated.com/showthread/comp.arch.embedde... ).
Well, let me show you how low they get it so you know what your reusable-for-better-products micro would compete with:
http://www.microchip.com/ParamChartSearch/chart.aspx?branchI...
The smallest one is designed, masked, printed on silicon, packaged and sold in 5k quantities at 24 cents a chip at a profit! That's nuts! I can only imagine what the 4-bitters cost. The cheapest 32-bitter I found were 32-bit NXP's at 10,000 units for about 50 cents. So, they're getting there. It's an understatement, though, to say the manufacturing costs are highly competitive in this sector. :)
Even ignoring that, because llvm instruction set mismatch between versions, i can't feed the rust generated IR to their firmware generating tool.
If you see their language xC(https://en.wikipedia.org/wiki/XC_(programming_language), it extends C with various pointer types(restricted, movable, alias) for memory safety. Rust definitely is a good fit for this kind of development with borrow checker, traits etc.
Agreed, but I think long-term its certainly going to be easier doing that on the rust platform with a tool like cargo than the current state of affairs.
Maybe if rust just concentrated on the hobbyist/prototypers at first i.e. arduino / rasberry pi, to make that experience as great and pain free as possible and really showcase what can be done with rust and cargo. That would at least make it a viable tool for professors teaching the next gen of engineers and all the startups/prototypers/hobbiests.