rp: hook up softfloat rom intrinsics

rp-hal has done this very well already, so we'll just copy their entire
impl again. only div.rs needed some massaging because our sio access
works a little differently, everything else worked as is.

tests/rp/.cargo/config.toml

@@ -1,6 +1,8 @@
 [unstable]
-build-std = ["core"]
-build-std-features = ["panic_immediate_abort"]
+# enabling these breaks the float tests during linking, with intrinsics
+# duplicated between embassy-rp and compilter_builtins
+#build-std = ["core"]
+#build-std-features = ["panic_immediate_abort"]
 
 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
 #runner = "teleprobe client run --target rpi-pico --elf"

tests/rp/Cargo.toml

@@ -8,7 +8,7 @@ license = "MIT OR Apache-2.0"
 embassy-sync = { version = "0.2.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["arch-cortex-m", "executor-thread", "defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt"] }
-embassy-rp = { version = "0.1.0", path = "../../embassy-rp", features = ["nightly", "defmt", "unstable-pac", "unstable-traits", "time-driver", "critical-section-impl"]  }
+embassy-rp = { version = "0.1.0", path = "../../embassy-rp", features = ["nightly", "defmt", "unstable-pac", "unstable-traits", "time-driver", "critical-section-impl", "intrinsics", "rom-v2-intrinsics"]  }
 embassy-futures = { version = "0.1.0", path = "../../embassy-futures" }
 
 defmt = "0.3.0"

tests/rp/src/bin/float.rs

@@ -0,0 +1,53 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_rp::pac;
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    embassy_rp::init(Default::default());
+    info!("Hello World!");
+
+    const PI_F: f32 = 3.1415926535f32;
+    const PI_D: f64 = 3.14159265358979323846f64;
+
+    unsafe {
+        pac::BUSCTRL
+            .perfsel(0)
+            .write(|r| r.set_perfsel(pac::busctrl::vals::Perfsel::ROM));
+    }
+
+    for i in 0..=360 {
+        let rad_f = (i as f32) * PI_F / 180.0;
+        info!(
+            "{}° float: {=f32} / {=f32} / {=f32} / {=f32}",
+            i,
+            rad_f,
+            rad_f - PI_F,
+            rad_f + PI_F,
+            rad_f % PI_F
+        );
+        let rad_d = (i as f64) * PI_D / 180.0;
+        info!(
+            "{}° double: {=f64} / {=f64} / {=f64} / {=f64}",
+            i,
+            rad_d,
+            rad_d - PI_D,
+            rad_d + PI_D,
+            rad_d % PI_D
+        );
+        Timer::after(Duration::from_millis(10)).await;
+    }
+
+    let rom_accesses = unsafe { pac::BUSCTRL.perfctr(0).read().perfctr() };
+    // every float operation used here uses at least 10 cycles
+    defmt::assert!(rom_accesses >= 360 * 12 * 10);
+
+    info!("Test OK");
+    cortex_m::asm::bkpt();
+}