This commit follows the same logic as:
- https://github.com/rust-lang/compiler-builtins/pull/462
- https://github.com/rust-lang/compiler-builtins/pull/466
I've tested the changes by preparing a simple program:
```rust
fn calc() -> ... {
let x = hint::black_box(4u...); // 4u8, 4u16, 4u32, 4u64, 4u128 + signed
let y = hint::black_box(1u32);
// x >> y
// x << y
}
fn main() -> ! {
let dp = arduino_hal::Peripherals::take().unwrap();
let pins = arduino_hal::pins!(dp);
let mut serial = arduino_hal::default_serial!(dp, pins, 57600);
for b in calc().to_le_bytes() {
_ = ufmt::uwrite!(&mut serial, "{} ", b);
}
_ = ufmt::uwriteln!(&mut serial, "");
loop {
//
}
}
```
... switching types & operators in `calc()`, and observing the results;
what I ended up with was:
```
u32 << u32 - ok
u64 << u32 - ok
u128 << u32 - error (undefined reference to `__ashlti3')
i32 >> u32 - ok
i64 >> u32 - ok
i128 >> u32 - error (undefined reference to `__ashrti3')
u32 >> u32 - ok
u64 >> u32 - ok
u128 >> u32 - error (undefined reference to `__lshrti3')
(where "ok" = compiles and returns correct results)
```
As with multiplication and division, so do in here 128-bit operations
not work, because avr-gcc's standard library doesn't provide them (at
the same time, requiring that specific calling convention, making it
pretty difficult for compiler-builtins to jump in).
I think 128-bit operations non-working on an 8-bit controller is an
acceptable trade-off - 😇 - and so the entire fix in here is
just about skipping those functions.
d20eea4d47