This manifested as incorrect error messages from mpy-cross, like
```
$ mpy-cross doesnotexist.py
OSError: [Errno 2] cno such file/director
```
The remaining bits in `b` must be shifted to the correct position before
entering the loop.
For most (all?) actual builds, compress_max_length_bits was 8 and the
problem went unnoticed.
This switches stage2 to C and uses Jinja to change the C code based
on flash settings from https://github.com/adafruit/nvm.toml. It
produces the fastest settings for the given set of external flashes.
Flash size is no longer hard coded so switching flashes with similar
capabilities but different sizes should *just work*.
This PR also places "ITCM" code in RAM to save the XIP cache for
code execution. Further optimization is possible. A blink code.py
still requires a number of flash fetches every blink.
Fixes#4041
Instead of counting words in make, which is slightly awful, notice that
possible_devices is local to external_flash.c, so we can declare the array
with an automatic bound, and then get the count as the element-count
(MP_ARRAY_SIZE) of the array.
Since EXTERNAL_FLASH_DEVICE_COUNT is no longer a global macro, switch
a few sites to using EXTERNAL_FLASH_DEVICES in `#if` checks instead.
This adds some additional code in mkfs which doesn't seem necessary, and
Disabling it saves 172 bytes flash.
Testing performed: Using a Feather M0 Adalogger, checked that
* an sdcard could still be mounted (using adafruit_sdcard)
* os.listdir() of "/" and "/sd" worked
* CIRCUITPY still mounted
This is a first go at it, done by naive replacing of all array
operations with corresponding operations on the list. Note that
there is a lot of unnecessary type conversions, here. Also, list_pop
has been copied, because it's decalerd STATIC in py/objlist.h
Since we want to expose the list of group's children to the user,
we should only have the original objects in it, without any other
additional data, and compute the native object as needed.
This saves about 60 bytes (Feather M4 went from 45040 -> 45100 bytes free)
66 bytes of data eliminated, but 6 bytes paid back to initialize the length
field.
