Make the @micropython.native decorator no-op if support isn't enabled

When adding the ability for boards to turn on the `@micropython.native`, `viper`, and `asm_thumb` decorators it was pointed out that it's somewhat awkward to write libraries and drivers that can take advantage of this since the decorators raise `SyntaxErrors` if they aren't enabled. In the case of `viper` and `asm_thumb` this behavior makes sense as they require writing non-normative code. Drivers could have a normal and viper/thumb implementation and implement them as such:

```python
try:
    import _viper_impl as _impl
except SyntaxError:
    import _python_impl as _impl

def do_thing():
    return _impl.do_thing()
```

For `native`, however, this behavior and the pattern to work around it is less than ideal. Since `native` code should also be valid Python code (although not necessarily the other way around) using the pattern above means *duplicating* the Python implementation and adding `@micropython.native` in the code. This is an unnecessary maintenance burden.

This commit *modifies* the behavior of the `@micropython.native` decorator. On boards with `CIRCUITPY_ENABLE_MPY_NATIVE` turned on it operates as usual. On boards with it turned off it does *nothing*- it doesn't raise a `SyntaxError` and doesn't apply optimizations. This means we can write our drivers/libraries once and take advantage of speedups on boards where they are enabled.
crypto-aes
Thea Flowers 3 years ago
parent e560b419f8
commit 84e1d7f304
No known key found for this signature in database
GPG Key ID: 3CA6321E8CACD921

@ -775,13 +775,22 @@ STATIC bool compile_built_in_decorator(compiler_t *comp, int name_len, mp_parse_
qstr attr = MP_PARSE_NODE_LEAF_ARG(name_nodes[1]);
if (attr == MP_QSTR_bytecode) {
*emit_options = MP_EMIT_OPT_BYTECODE;
#if MICROPY_EMIT_NATIVE
// @micropython.native decorator.
} else if (attr == MP_QSTR_native) {
// Different from MicroPython: native doesn't raise SyntaxError if native support isn't
// compiled, it just passes through the function unmodified.
#if MICROPY_EMIT_NATIVE
*emit_options = MP_EMIT_OPT_NATIVE_PYTHON;
#else
return true;
#endif
#if MICROPY_EMIT_NATIVE
// @micropython.viper decorator.
} else if (attr == MP_QSTR_viper) {
*emit_options = MP_EMIT_OPT_VIPER;
#endif
#endif
#if MICROPY_EMIT_INLINE_ASM
// @micropython.asm_thumb decorator.
} else if (attr == ASM_DECORATOR_QSTR) {
*emit_options = MP_EMIT_OPT_ASM;
#endif

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