This is just support for the chip, no boards are currently supported.
However, you can use this target on a custom board.
Notes:
- This required a new runtime and machine implementation, because the
hardware is actually very different (and much nicer than older
AVRs!).
- I had to update gen-device-avr to support this chip. This also
affects the generated output of other AVRs, but I checked all chips
we support and there shouldn't be any backwards incompatible
changes.
- I did not implement peripherals like UART, I2C, SPI, etc because I
don't need them. That is left to do in the future.
You can flash these chips with only a UART and a 1kOhm resistor, which
is really nice (no special hardware needed). Here is the program I've
used for this purpose: https://pypi.org/project/pymcuprog/
This basically reverts https://github.com/tinygo-org/tinygo/pull/3357
and replaces it with a different mechanism to get to the same goal.
I do not think filtering tags like this is a good idea: it's the wrong
part of the compiler to be concerned with such tags (that part sets
tags, but doesn't modify existing tags). Instead, I've written the
//go:build lines in such a way that it has the same effect: WASI
defaults to leveldb, everything else defaults to fnv, and it's possible
to override the default using build tags.
* Rename pinetime-devkit0 to pinetime because the production device is
almost the same hardware (the only noticeable difference is a
different accelerometer, which isn't part of the board file).
* Remove the UART and set serial to none. The UART uses a lot of
current by default, so it seems better to disable it.
This is a breaking change, but honestly I think I'm the only one who has
ever actually used TinyGo for the PineTime and I'm fine with this
change :)
The only thing that's different between all these chips is the flash
size, which can easily be passed as a linker flag instead. This removes
a bunch of duplicate code in an uncommon language (linker script).
I've also fixed a few boards with incorrect flash sizes:
* nano-rp2040 has 16MB instead of 2MB
* macropad-rp2040 has 8MB instead of 2MB
* gopher-badge has 8MB instead of 1MB
machine/stm32, nrf: implement machine.Flash
Implements the machine.Flash interface using the same definition as the tinyfs BlockDevice.
This implementation covers the stm32f4, stm32l4, stm32wlx, nrf51, nrf52, and nrf528xx processors.
This allows you to expand {tmpDir} in the json "emulator" field, and
uses it in wasmtime instead of custom TMPDIR mapping logic.
Before, we had custom logic for wasmtime to create a separate tmpDir
when running go tests. This overwrite the TMPDIR variable when running,
after making a mount point. A simpler way to accomplish the end goal of
writing temp files is to use wasmtime's map-dir instead. When code is
compiled to wasm with the wasi target, tempDir is always /tmp, so we
don't need to add variables (since we know what it is). Further, the
test code is the same between normal go and run through wasmtime. So, we
don't need to make a separate temp dir first, and avoiding that reduces
logic, as well makes it easier to swap out the emulator (for wazero
which has no depedencies). To map the correct directory, this introduces
a {tmpDir} token whose value is the host-specific value taken from
`os.TempDir()`.
The motivation I have for this isn't so much to clean up the wasmtime
code, but allow wazero to execute the same tests. After this change, the
only thing needed to pass tests is to change the emulator, due to
differences in how wazero deals with relative lookups (they aren't
restricted by default, so there's not a huge amount of custom logic
needed).
In other words, installing wazero from main, `make tinygo-test-wasi`
works with no other changes except this PR and patching
`targets/wasi.json`.
```json
"emulator": "wazero run -mount=.:/ -mount={tmpDir}:/tmp {}",
```
On that note, if there's a way to override the emulator via arg or env,
this would be even better, but in any case patching json is fine.
Signed-off-by: Adrian Cole <adrian@tetrate.io>
ThinLTO results in a small code size reduction, which is nice
(especially on these very small chips). It also brings us one step
closer to using ThinLTO everywhere.
I found that .data is not correctly initialized with firmware images
that use over 64kB of flash. The problem is that the data in .data
(which is stored in flash, and copied to RAM at reset) is beyond the
64kB limit and must therefore be loaded using the elpm instruction
instead of the lpm instruction.
I encountered this issue while getting testdata/math.go to work for AVR.
The following command mostly works with this patch, while it prints
garbage withtout it:
tinygo run -target=simavr -size=short -scheduler=none ./testdata/math.go
(This also requires a patch to picolibc to work, see
https://github.com/picolibc/picolibc/pull/371)
It still doesn't work entirely with this patch: some of the math
operations have an incorrect result. But at least it's an improvement as
it won't print garbage anymore.
- Use compiler-rt and picolibc instead of avr-libc.
- Use ld.lld instead of avr-ld (or avr-gcc).
This makes it much easier to get started with TinyGo on AVR because
installing these extra tools (gcc-avr, avr-libc) can be a hassle.
It also opens the door for future improvements such as ThinLTO.
There is a code size increase but I think it's worth it in the long run.
The code size increase can hopefully be reduced with improvements to the
LLVM AVR backend and to compiler-rt.
The Espressif fork of LLVM now has Xtensa support in the linker LLD.
(This support was written mosly by me). This means we don't have to use
the Espressif GNU toolchain anymore and makes installing TinyGo simpler.
In the future, this also paves the way for ThinLTO support. Right now it
is mostly just a way to simplify TinyGo installation and speed up CI
slightly.
This flag is necessary in LLVM 15 because it appears that LLVM 15 has
changed the default target ABI from lp64 to lp64d. This results in a
linker failure. Setting the "target-abi" forces the RISC-V backend to
use the intended target ABI.
Scanning of allocas was entirely broken on WebAssembly. The code
intended to do this was never run. There were also no tests.
Looking into this further, I found that it is actually not really
necessary to do that: the C stack can be scanned conservatively and in
fact this was already done for goroutine stacks (because they live on
the heap and are always referenced). It wasn't done for the system stack
however.
With these fixes, I believe code should be both faster *and* more
correct.
I found this in my work to get opaque pointers supported in LLVM 15,
because the code that was never reached now finally got run and was
actually quite buggy.
This prefix isn't actually used and only adds noise, so remove it.
It may have been useful on Linux that makes a distinction between
/dev/ttyACM* and /dev/ttyUSB* but it isn't now. Also, it's unlikely that
the same vid/pid pair will be shared between an acm and usb driver
anyway.
The needed stack size is hard to determine by the compiler. It will try,
but will fail in many common cases. Therefore, the runtime will pick a
fixed stack size.
There is a tradeoff between avoiding stack overflows and wasting RAM.
This tradeoff depends on the application: some don't need large stack
sizes but do need a lot of memory, while others need deep stacks but
aren't so memory constrained. That's why I've added a flag to do this on
the command line: https://github.com/tinygo-org/tinygo/pull/3159
It may be reasonable to use a different stack size per chip, for example
chips with lots of RAM could default to a larger stack size. But I don't
think it's a good idea to do this per board.
--allow-undefined can be a problem: it allows compiling code that will
fail when loaded. This change makes sure that if some symbols are
undefined, they are reported as an error by the linker.
Previously, people could get away with importing a function that was not
defined, like this:
func add(int a, int b) int
func test() {
println(add(3, 5))
}
This was always unintended but mostly worked. With this change, it isn't
possible anymore. Now every function needs to be marked with //export
explicitly:
//export add
func add(int a, int b) int
func test() {
println(add(3, 5))
}
As before, functions will be placed in the `env` module with the name
set from the `//export` tag. This can be overridden with
`//go:import-module`:
//go:import-module math
//export add
func add(int a, int b) int
func test() {
println(add(3, 5))
}
For the syscall/js package, I needed to give a list of symbols that are
undefined. This list is based on the JavaScript functions defined in
targets/wasm_exec.js.
This target was added purely for running tests, and it is currently
unused. When I try to use it, it causes runtime exceptions.
The replacement riscv-qemu is much better behaved.
This doesn't drop support for any actual hardware, the HiFive 1 B will
remain supported.
The Go tools only consider lowercase .s files to be assembly files. By
renaming these to uppercase .S files they won't be discovered by the Go
toolchain and listed as the SFiles to be assembled.
There is a difference between .s and .S: only uppercase .S will be
passed through the preprocessor. Doing that is normally safe, and
definitely safe in the case of these files.
