Merge #1382

1382: rp: hook up softfloat intrinsics to bootrom r=Dirbaio a=pennae

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.

includes a minor bit of refactoring to make it easier to check which bits we've copied from rp2040-hal and which we haven't.

Co-authored-by: pennae <github@quasiparticle.net>

embassy-rp/src/float/add_sub.rs

@@ -0,0 +1,92 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/add_sub.rs
+
+use super::{Float, Int};
+use crate::rom_data;
+
+trait ROMAdd {
+    fn rom_add(self, b: Self) -> Self;
+}
+
+impl ROMAdd for f32 {
+    fn rom_add(self, b: Self) -> Self {
+        rom_data::float_funcs::fadd(self, b)
+    }
+}
+
+impl ROMAdd for f64 {
+    fn rom_add(self, b: Self) -> Self {
+        rom_data::double_funcs::dadd(self, b)
+    }
+}
+
+fn add<F: Float + ROMAdd>(a: F, b: F) -> F {
+    if a.is_not_finite() {
+        if b.is_not_finite() {
+            let class_a = a.repr() & (F::SIGNIFICAND_MASK | F::SIGN_MASK);
+            let class_b = b.repr() & (F::SIGNIFICAND_MASK | F::SIGN_MASK);
+
+            if class_a == F::Int::ZERO && class_b == F::Int::ZERO {
+                // inf + inf = inf
+                return a;
+            }
+            if class_a == F::SIGN_MASK && class_b == F::SIGN_MASK {
+                // -inf + (-inf) = -inf
+                return a;
+            }
+
+            // Sign mismatch, or either is NaN already
+            return F::NAN;
+        }
+
+        // [-]inf/NaN + X = [-]inf/NaN
+        return a;
+    }
+
+    if b.is_not_finite() {
+        // X + [-]inf/NaN = [-]inf/NaN
+        return b;
+    }
+
+    a.rom_add(b)
+}
+
+intrinsics! {
+    #[alias = __addsf3vfp]
+    #[aeabi = __aeabi_fadd]
+    extern "C" fn __addsf3(a: f32, b: f32) -> f32 {
+        add(a, b)
+    }
+
+    #[bootrom_v2]
+    #[alias = __adddf3vfp]
+    #[aeabi = __aeabi_dadd]
+    extern "C" fn __adddf3(a: f64, b: f64) -> f64 {
+        add(a, b)
+    }
+
+    // The ROM just implements subtraction the same way, so just do it here
+    // and save the work of implementing more complicated NaN/inf handling.
+
+    #[alias = __subsf3vfp]
+    #[aeabi = __aeabi_fsub]
+    extern "C" fn __subsf3(a: f32, b: f32) -> f32 {
+        add(a, -b)
+    }
+
+    #[bootrom_v2]
+    #[alias = __subdf3vfp]
+    #[aeabi = __aeabi_dsub]
+    extern "C" fn __subdf3(a: f64, b: f64) -> f64 {
+        add(a, -b)
+    }
+
+    extern "aapcs" fn __aeabi_frsub(a: f32, b: f32) -> f32 {
+        add(b, -a)
+    }
+
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_drsub(a: f64, b: f64) -> f64 {
+        add(b, -a)
+    }
+}

embassy-rp/src/float/cmp.rs

@@ -0,0 +1,201 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/cmp.rs
+
+use super::Float;
+use crate::rom_data;
+
+trait ROMCmp {
+    fn rom_cmp(self, b: Self) -> i32;
+}
+
+impl ROMCmp for f32 {
+    fn rom_cmp(self, b: Self) -> i32 {
+        rom_data::float_funcs::fcmp(self, b)
+    }
+}
+
+impl ROMCmp for f64 {
+    fn rom_cmp(self, b: Self) -> i32 {
+        rom_data::double_funcs::dcmp(self, b)
+    }
+}
+
+fn le_abi<F: Float + ROMCmp>(a: F, b: F) -> i32 {
+    if a.is_nan() || b.is_nan() {
+        1
+    } else {
+        a.rom_cmp(b)
+    }
+}
+
+fn ge_abi<F: Float + ROMCmp>(a: F, b: F) -> i32 {
+    if a.is_nan() || b.is_nan() {
+        -1
+    } else {
+        a.rom_cmp(b)
+    }
+}
+
+intrinsics! {
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[alias = __eqsf2, __ltsf2, __nesf2]
+    extern "C" fn __lesf2(a: f32, b: f32) -> i32 {
+        le_abi(a, b)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[alias = __eqdf2, __ltdf2, __nedf2]
+    extern "C" fn __ledf2(a: f64, b: f64) -> i32 {
+        le_abi(a, b)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[alias = __gtsf2]
+    extern "C" fn __gesf2(a: f32, b: f32) -> i32 {
+        ge_abi(a, b)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[alias = __gtdf2]
+    extern "C" fn __gedf2(a: f64, b: f64) -> i32 {
+        ge_abi(a, b)
+    }
+
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_fcmple(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) <= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_fcmpge(a: f32, b: f32) -> i32 {
+        (ge_abi(a, b) >= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_fcmpeq(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) == 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_fcmplt(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) < 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_fcmpgt(a: f32, b: f32) -> i32 {
+        (ge_abi(a, b) > 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_dcmple(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) <= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_dcmpge(a: f64, b: f64) -> i32 {
+        (ge_abi(a, b) >= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_dcmpeq(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) == 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_dcmplt(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) < 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "aapcs" fn __aeabi_dcmpgt(a: f64, b: f64) -> i32 {
+        (ge_abi(a, b) > 0) as i32
+    }
+
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __gesf2vfp(a: f32, b: f32) -> i32 {
+        (ge_abi(a, b) >= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __gedf2vfp(a: f64, b: f64) -> i32 {
+        (ge_abi(a, b) >= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __gtsf2vfp(a: f32, b: f32) -> i32 {
+        (ge_abi(a, b) > 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __gtdf2vfp(a: f64, b: f64) -> i32 {
+        (ge_abi(a, b) > 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __ltsf2vfp(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) < 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __ltdf2vfp(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) < 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __lesf2vfp(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) <= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __ledf2vfp(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) <= 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __nesf2vfp(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) != 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __nedf2vfp(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) != 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __eqsf2vfp(a: f32, b: f32) -> i32 {
+        (le_abi(a, b) == 0) as i32
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    extern "C" fn __eqdf2vfp(a: f64, b: f64) -> i32 {
+        (le_abi(a, b) == 0) as i32
+    }
+}

embassy-rp/src/float/conv.rs

@@ -0,0 +1,157 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/conv.rs
+
+use super::Float;
+use crate::rom_data;
+
+// Some of these are also not connected in the Pico SDK.  This is probably
+// because the ROM version actually does a fixed point conversion, just with
+// the fractional width set to zero.
+
+intrinsics! {
+    // Not connected in the Pico SDK
+    #[slower_than_default]
+    #[aeabi = __aeabi_i2f]
+    extern "C" fn __floatsisf(i: i32) -> f32 {
+        rom_data::float_funcs::int_to_float(i)
+    }
+
+    // Not connected in the Pico SDK
+    #[slower_than_default]
+    #[aeabi = __aeabi_i2d]
+    extern "C" fn __floatsidf(i: i32) -> f64 {
+        rom_data::double_funcs::int_to_double(i)
+    }
+
+    // Questionable gain
+    #[aeabi = __aeabi_l2f]
+    extern "C" fn __floatdisf(i: i64) -> f32 {
+        rom_data::float_funcs::int64_to_float(i)
+    }
+
+    #[bootrom_v2]
+    #[aeabi = __aeabi_l2d]
+    extern "C" fn __floatdidf(i: i64) -> f64 {
+        rom_data::double_funcs::int64_to_double(i)
+    }
+
+    // Not connected in the Pico SDK
+    #[slower_than_default]
+    #[aeabi = __aeabi_ui2f]
+    extern "C" fn __floatunsisf(i: u32) -> f32 {
+        rom_data::float_funcs::uint_to_float(i)
+    }
+
+    // Questionable gain
+    #[bootrom_v2]
+    #[aeabi = __aeabi_ui2d]
+    extern "C" fn __floatunsidf(i: u32) -> f64 {
+        rom_data::double_funcs::uint_to_double(i)
+    }
+
+    // Questionable gain
+    #[bootrom_v2]
+    #[aeabi = __aeabi_ul2f]
+    extern "C" fn __floatundisf(i: u64) -> f32 {
+        rom_data::float_funcs::uint64_to_float(i)
+    }
+
+    #[bootrom_v2]
+    #[aeabi = __aeabi_ul2d]
+    extern "C" fn __floatundidf(i: u64) -> f64 {
+        rom_data::double_funcs::uint64_to_double(i)
+    }
+
+
+    // The Pico SDK does some optimization here (e.x. fast paths for zero and
+    // one), but we can just directly connect it.
+    #[aeabi = __aeabi_f2iz]
+    extern "C" fn __fixsfsi(f: f32) -> i32 {
+        rom_data::float_funcs::float_to_int(f)
+    }
+
+    #[bootrom_v2]
+    #[aeabi = __aeabi_f2lz]
+    extern "C" fn __fixsfdi(f: f32) -> i64 {
+        rom_data::float_funcs::float_to_int64(f)
+    }
+
+    // Not connected in the Pico SDK
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[aeabi = __aeabi_d2iz]
+    extern "C" fn __fixdfsi(f: f64) -> i32 {
+        rom_data::double_funcs::double_to_int(f)
+    }
+
+    // Like with the 32 bit version, there's optimization that we just
+    // skip.
+    #[bootrom_v2]
+    #[aeabi = __aeabi_d2lz]
+    extern "C" fn __fixdfdi(f: f64) -> i64 {
+        rom_data::double_funcs::double_to_int64(f)
+    }
+
+    #[slower_than_default]
+    #[aeabi = __aeabi_f2uiz]
+    extern "C" fn __fixunssfsi(f: f32) -> u32 {
+        rom_data::float_funcs::float_to_uint(f)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[aeabi = __aeabi_f2ulz]
+    extern "C" fn __fixunssfdi(f: f32) -> u64 {
+        rom_data::float_funcs::float_to_uint64(f)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[aeabi = __aeabi_d2uiz]
+    extern "C" fn __fixunsdfsi(f: f64) -> u32 {
+        rom_data::double_funcs::double_to_uint(f)
+    }
+
+    #[slower_than_default]
+    #[bootrom_v2]
+    #[aeabi = __aeabi_d2ulz]
+    extern "C" fn __fixunsdfdi(f: f64) -> u64 {
+        rom_data::double_funcs::double_to_uint64(f)
+    }
+
+    #[bootrom_v2]
+    #[alias = __extendsfdf2vfp]
+    #[aeabi = __aeabi_f2d]
+    extern "C" fn  __extendsfdf2(f: f32) -> f64 {
+        if f.is_not_finite() {
+            return f64::from_repr(
+                // Not finite
+                f64::EXPONENT_MASK |
+                // Preserve NaN or inf
+                ((f.repr() & f32::SIGNIFICAND_MASK) as u64) |
+                // Preserve sign
+                ((f.repr() & f32::SIGN_MASK) as u64) << (f64::BITS-f32::BITS)
+            );
+        }
+        rom_data::float_funcs::float_to_double(f)
+    }
+
+    #[bootrom_v2]
+    #[alias = __truncdfsf2vfp]
+    #[aeabi = __aeabi_d2f]
+    extern "C" fn __truncdfsf2(f: f64) -> f32 {
+        if f.is_not_finite() {
+            let mut repr: u32 =
+                // Not finite
+                f32::EXPONENT_MASK |
+                // Preserve sign
+                ((f.repr() & f64::SIGN_MASK) >> (f64::BITS-f32::BITS)) as u32;
+            // Set NaN
+            if  (f.repr() & f64::SIGNIFICAND_MASK) != 0 {
+                repr |= 1;
+            }
+            return f32::from_repr(repr);
+        }
+        rom_data::double_funcs::double_to_float(f)
+    }
+}

embassy-rp/src/float/div.rs

@@ -0,0 +1,141 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/conv.rs
+
+use super::Float;
+use crate::rom_data;
+
+// Make sure this stays as a separate call, because when it's inlined the
+// compiler will move the save of the registers used to contain the divider
+// state into the function prologue.  That save and restore (push/pop) takes
+// longer than the actual division, so doing it in the common case where
+// they are not required wastes a lot of time.
+#[inline(never)]
+#[cold]
+fn save_divider_and_call<F, R>(f: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    let sio = rp_pac::SIO;
+
+    unsafe {
+        // Since we can't save the signed-ness of the calculation, we have to make
+        // sure that there's at least an 8 cycle delay before we read the result.
+        // The Pico SDK ensures this by using a 6 cycle push and two 1 cycle reads.
+        // Since we can't be sure the Rust implementation will optimize to the same,
+        // just use an explicit wait.
+        while !sio.div().csr().read().ready() {}
+
+        // Read the quotient last, since that's what clears the dirty flag
+        let dividend = sio.div().udividend().read();
+        let divisor = sio.div().udivisor().read();
+        let remainder = sio.div().remainder().read();
+        let quotient = sio.div().quotient().read();
+
+        // If we get interrupted here (before a write sets the DIRTY flag) its fine, since
+        // we have the full state, so the interruptor doesn't have to restore it.  Once the
+        // write happens and the DIRTY flag is set, the interruptor becomes responsible for
+        // restoring our state.
+        let result = f();
+
+        // If we are interrupted here, then the interruptor will start an incorrect calculation
+        // using a wrong divisor, but we'll restore the divisor and result ourselves correctly.
+        // This sets DIRTY, so any interruptor will save the state.
+        sio.div().udividend().write_value(dividend);
+        // If we are interrupted here, the the interruptor may start the calculation using
+        // incorrectly signed inputs, but we'll restore the result ourselves.
+        // This sets DIRTY, so any interruptor will save the state.
+        sio.div().udivisor().write_value(divisor);
+        // If we are interrupted here, the interruptor will have restored everything but the
+        // quotient may be wrongly signed.  If the calculation started by the above writes is
+        // still ongoing it is stopped, so it won't replace the result we're restoring.
+        // DIRTY and READY set, but only DIRTY matters to make the interruptor save the state.
+        sio.div().remainder().write_value(remainder);
+        // State fully restored after the quotient write.  This sets both DIRTY and READY, so
+        // whatever we may have interrupted can read the result.
+        sio.div().quotient().write_value(quotient);
+
+        result
+    }
+}
+
+fn save_divider<F, R>(f: F) -> R
+where
+    F: FnOnce() -> R,
+{
+    let sio = rp_pac::SIO;
+    if unsafe { !sio.div().csr().read().dirty() } {
+        // Not dirty, so nothing is waiting for the calculation.  So we can just
+        // issue it directly without a save/restore.
+        f()
+    } else {
+        save_divider_and_call(f)
+    }
+}
+
+trait ROMDiv {
+    fn rom_div(self, b: Self) -> Self;
+}
+
+impl ROMDiv for f32 {
+    fn rom_div(self, b: Self) -> Self {
+        // ROM implementation uses the hardware divider, so we have to save it
+        save_divider(|| rom_data::float_funcs::fdiv(self, b))
+    }
+}
+
+impl ROMDiv for f64 {
+    fn rom_div(self, b: Self) -> Self {
+        // ROM implementation uses the hardware divider, so we have to save it
+        save_divider(|| rom_data::double_funcs::ddiv(self, b))
+    }
+}
+
+fn div<F: Float + ROMDiv>(a: F, b: F) -> F {
+    if a.is_not_finite() {
+        if b.is_not_finite() {
+            // inf/NaN / inf/NaN = NaN
+            return F::NAN;
+        }
+
+        if b.is_zero() {
+            // inf/NaN / 0 = NaN
+            return F::NAN;
+        }
+
+        return if b.is_sign_negative() {
+            // [+/-]inf/NaN / (-X) = [-/+]inf/NaN
+            a.negate()
+        } else {
+            // [-]inf/NaN / X = [-]inf/NaN
+            a
+        };
+    }
+
+    if b.is_nan() {
+        // X / NaN = NaN
+        return b;
+    }
+
+    // ROM handles X / 0 = [-]inf and X / [-]inf = [-]0, so we only
+    // need to catch 0 / 0
+    if b.is_zero() && a.is_zero() {
+        return F::NAN;
+    }
+
+    a.rom_div(b)
+}
+
+intrinsics! {
+    #[alias = __divsf3vfp]
+    #[aeabi = __aeabi_fdiv]
+    extern "C" fn __divsf3(a: f32, b: f32) -> f32 {
+        div(a, b)
+    }
+
+    #[bootrom_v2]
+    #[alias = __divdf3vfp]
+    #[aeabi = __aeabi_ddiv]
+    extern "C" fn __divdf3(a: f64, b: f64) -> f64 {
+        div(a, b)
+    }
+}

embassy-rp/src/float/functions.rs

@@ -0,0 +1,239 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/functions.rs
+
+use crate::float::{Float, Int};
+use crate::rom_data;
+
+trait ROMFunctions {
+    fn sqrt(self) -> Self;
+    fn ln(self) -> Self;
+    fn exp(self) -> Self;
+    fn sin(self) -> Self;
+    fn cos(self) -> Self;
+    fn tan(self) -> Self;
+    fn atan2(self, y: Self) -> Self;
+
+    fn to_trig_range(self) -> Self;
+}
+
+impl ROMFunctions for f32 {
+    fn sqrt(self) -> Self {
+        rom_data::float_funcs::fsqrt(self)
+    }
+
+    fn ln(self) -> Self {
+        rom_data::float_funcs::fln(self)
+    }
+
+    fn exp(self) -> Self {
+        rom_data::float_funcs::fexp(self)
+    }
+
+    fn sin(self) -> Self {
+        rom_data::float_funcs::fsin(self)
+    }
+
+    fn cos(self) -> Self {
+        rom_data::float_funcs::fcos(self)
+    }
+
+    fn tan(self) -> Self {
+        rom_data::float_funcs::ftan(self)
+    }
+
+    fn atan2(self, y: Self) -> Self {
+        rom_data::float_funcs::fatan2(self, y)
+    }
+
+    fn to_trig_range(self) -> Self {
+        // -128 < X < 128, logic from the Pico SDK
+        let exponent = (self.repr() & Self::EXPONENT_MASK) >> Self::SIGNIFICAND_BITS;
+        if exponent < 134 {
+            self
+        } else {
+            self % (core::f32::consts::PI * 2.0)
+        }
+    }
+}
+
+impl ROMFunctions for f64 {
+    fn sqrt(self) -> Self {
+        rom_data::double_funcs::dsqrt(self)
+    }
+
+    fn ln(self) -> Self {
+        rom_data::double_funcs::dln(self)
+    }
+
+    fn exp(self) -> Self {
+        rom_data::double_funcs::dexp(self)
+    }
+
+    fn sin(self) -> Self {
+        rom_data::double_funcs::dsin(self)
+    }
+
+    fn cos(self) -> Self {
+        rom_data::double_funcs::dcos(self)
+    }
+    fn tan(self) -> Self {
+        rom_data::double_funcs::dtan(self)
+    }
+
+    fn atan2(self, y: Self) -> Self {
+        rom_data::double_funcs::datan2(self, y)
+    }
+
+    fn to_trig_range(self) -> Self {
+        // -1024 < X < 1024, logic from the Pico SDK
+        let exponent = (self.repr() & Self::EXPONENT_MASK) >> Self::SIGNIFICAND_BITS;
+        if exponent < 1033 {
+            self
+        } else {
+            self % (core::f64::consts::PI * 2.0)
+        }
+    }
+}
+
+fn is_negative_nonzero_or_nan<F: Float>(f: F) -> bool {
+    let repr = f.repr();
+    if (repr & F::SIGN_MASK) != F::Int::ZERO {
+        // Negative, so anything other than exactly zero
+        return (repr & (!F::SIGN_MASK)) != F::Int::ZERO;
+    }
+    // NaN
+    (repr & (F::EXPONENT_MASK | F::SIGNIFICAND_MASK)) > F::EXPONENT_MASK
+}
+
+fn sqrt<F: Float + ROMFunctions>(f: F) -> F {
+    if is_negative_nonzero_or_nan(f) {
+        F::NAN
+    } else {
+        f.sqrt()
+    }
+}
+
+fn ln<F: Float + ROMFunctions>(f: F) -> F {
+    if is_negative_nonzero_or_nan(f) {
+        F::NAN
+    } else {
+        f.ln()
+    }
+}
+
+fn exp<F: Float + ROMFunctions>(f: F) -> F {
+    if f.is_nan() {
+        F::NAN
+    } else {
+        f.exp()
+    }
+}
+
+fn sin<F: Float + ROMFunctions>(f: F) -> F {
+    if f.is_not_finite() {
+        F::NAN
+    } else {
+        f.to_trig_range().sin()
+    }
+}
+
+fn cos<F: Float + ROMFunctions>(f: F) -> F {
+    if f.is_not_finite() {
+        F::NAN
+    } else {
+        f.to_trig_range().cos()
+    }
+}
+
+fn tan<F: Float + ROMFunctions>(f: F) -> F {
+    if f.is_not_finite() {
+        F::NAN
+    } else {
+        f.to_trig_range().tan()
+    }
+}
+
+fn atan2<F: Float + ROMFunctions>(x: F, y: F) -> F {
+    if x.is_nan() || y.is_nan() {
+        F::NAN
+    } else {
+        x.to_trig_range().atan2(y)
+    }
+}
+
+// Name collisions
+mod intrinsics {
+    intrinsics! {
+        extern "C" fn sqrtf(f: f32) -> f32 {
+            super::sqrt(f)
+        }
+
+        #[bootrom_v2]
+        extern "C" fn sqrt(f: f64) -> f64 {
+            super::sqrt(f)
+        }
+
+        extern "C" fn logf(f: f32) -> f32 {
+            super::ln(f)
+        }
+
+        #[bootrom_v2]
+        extern "C" fn log(f: f64) -> f64 {
+            super::ln(f)
+        }
+
+        extern "C" fn expf(f: f32) -> f32 {
+            super::exp(f)
+        }
+
+        #[bootrom_v2]
+        extern "C" fn exp(f: f64) -> f64 {
+            super::exp(f)
+        }
+
+        #[slower_than_default]
+        extern "C" fn sinf(f: f32) -> f32 {
+            super::sin(f)
+        }
+
+        #[slower_than_default]
+        #[bootrom_v2]
+        extern "C" fn sin(f: f64) -> f64 {
+            super::sin(f)
+        }
+
+        #[slower_than_default]
+        extern "C" fn cosf(f: f32) -> f32 {
+            super::cos(f)
+        }
+
+        #[slower_than_default]
+        #[bootrom_v2]
+        extern "C" fn cos(f: f64) -> f64 {
+            super::cos(f)
+        }
+
+        #[slower_than_default]
+        extern "C" fn tanf(f: f32) -> f32 {
+            super::tan(f)
+        }
+
+        #[slower_than_default]
+        #[bootrom_v2]
+        extern "C" fn tan(f: f64) -> f64 {
+            super::tan(f)
+        }
+
+        // Questionable gain
+        #[bootrom_v2]
+        extern "C" fn atan2f(a: f32, b: f32) -> f32 {
+            super::atan2(a, b)
+        }
+
+        // Questionable gain
+        #[bootrom_v2]
+        extern "C" fn atan2(a: f64, b: f64) -> f64 {
+            super::atan2(a, b)
+        }
+    }
+}

embassy-rp/src/float/mod.rs

@@ -0,0 +1,149 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/mod.rs
+
+use core::ops;
+
+// Borrowed and simplified from compiler-builtins so we can use bit ops
+// on floating point without macro soup.
+pub(crate) trait Int:
+    Copy
+    + core::fmt::Debug
+    + PartialEq
+    + PartialOrd
+    + ops::AddAssign
+    + ops::SubAssign
+    + ops::BitAndAssign
+    + ops::BitOrAssign
+    + ops::BitXorAssign
+    + ops::ShlAssign<i32>
+    + ops::ShrAssign<u32>
+    + ops::Add<Output = Self>
+    + ops::Sub<Output = Self>
+    + ops::Div<Output = Self>
+    + ops::Shl<u32, Output = Self>
+    + ops::Shr<u32, Output = Self>
+    + ops::BitOr<Output = Self>
+    + ops::BitXor<Output = Self>
+    + ops::BitAnd<Output = Self>
+    + ops::Not<Output = Self>
+{
+    const ZERO: Self;
+}
+
+macro_rules! int_impl {
+    ($ty:ty) => {
+        impl Int for $ty {
+            const ZERO: Self = 0;
+        }
+    };
+}
+
+int_impl!(u32);
+int_impl!(u64);
+
+pub(crate) trait Float:
+    Copy
+    + core::fmt::Debug
+    + PartialEq
+    + PartialOrd
+    + ops::AddAssign
+    + ops::MulAssign
+    + ops::Add<Output = Self>
+    + ops::Sub<Output = Self>
+    + ops::Div<Output = Self>
+    + ops::Rem<Output = Self>
+{
+    /// A uint of the same with as the float
+    type Int: Int;
+
+    /// NaN representation for the float
+    const NAN: Self;
+
+    /// The bitwidth of the float type
+    const BITS: u32;
+
+    /// The bitwidth of the significand
+    const SIGNIFICAND_BITS: u32;
+
+    /// A mask for the sign bit
+    const SIGN_MASK: Self::Int;
+
+    /// A mask for the significand
+    const SIGNIFICAND_MASK: Self::Int;
+
+    /// A mask for the exponent
+    const EXPONENT_MASK: Self::Int;
+
+    /// Returns `self` transmuted to `Self::Int`
+    fn repr(self) -> Self::Int;
+
+    /// Returns a `Self::Int` transmuted back to `Self`
+    fn from_repr(a: Self::Int) -> Self;
+
+    /// Return a sign swapped `self`
+    fn negate(self) -> Self;
+
+    /// Returns true if `self` is either NaN or infinity
+    fn is_not_finite(self) -> bool {
+        (self.repr() & Self::EXPONENT_MASK) == Self::EXPONENT_MASK
+    }
+
+    /// Returns true if `self` is infinity
+    fn is_infinity(self) -> bool {
+        (self.repr() & (Self::EXPONENT_MASK | Self::SIGNIFICAND_MASK)) == Self::EXPONENT_MASK
+    }
+
+    /// Returns true if `self is NaN
+    fn is_nan(self) -> bool {
+        (self.repr() & (Self::EXPONENT_MASK | Self::SIGNIFICAND_MASK)) > Self::EXPONENT_MASK
+    }
+
+    /// Returns true if `self` is negative
+    fn is_sign_negative(self) -> bool {
+        (self.repr() & Self::SIGN_MASK) != Self::Int::ZERO
+    }
+
+    /// Returns true if `self` is zero (either sign)
+    fn is_zero(self) -> bool {
+        (self.repr() & (Self::SIGNIFICAND_MASK | Self::EXPONENT_MASK)) == Self::Int::ZERO
+    }
+}
+
+macro_rules! float_impl {
+    ($ty:ident, $ity:ident, $bits:expr, $significand_bits:expr) => {
+        impl Float for $ty {
+            type Int = $ity;
+
+            const NAN: Self = <$ty>::NAN;
+
+            const BITS: u32 = $bits;
+            const SIGNIFICAND_BITS: u32 = $significand_bits;
+
+            const SIGN_MASK: Self::Int = 1 << (Self::BITS - 1);
+            const SIGNIFICAND_MASK: Self::Int = (1 << Self::SIGNIFICAND_BITS) - 1;
+            const EXPONENT_MASK: Self::Int = !(Self::SIGN_MASK | Self::SIGNIFICAND_MASK);
+
+            fn repr(self) -> Self::Int {
+                self.to_bits()
+            }
+
+            fn from_repr(a: Self::Int) -> Self {
+                Self::from_bits(a)
+            }
+
+            fn negate(self) -> Self {
+                -self
+            }
+        }
+    };
+}
+
+float_impl!(f32, u32, 32, 23);
+float_impl!(f64, u64, 64, 52);
+
+mod add_sub;
+mod cmp;
+mod conv;
+mod div;
+mod functions;
+mod mul;

embassy-rp/src/float/mul.rs

@@ -0,0 +1,70 @@
+// Credit: taken from `rp-hal` (also licensed Apache+MIT)
+// https://github.com/rp-rs/rp-hal/blob/main/rp2040-hal/src/float/mul.rs
+
+use super::Float;
+use crate::rom_data;
+
+trait ROMMul {
+    fn rom_mul(self, b: Self) -> Self;
+}
+
+impl ROMMul for f32 {
+    fn rom_mul(self, b: Self) -> Self {
+        rom_data::float_funcs::fmul(self, b)
+    }
+}
+
+impl ROMMul for f64 {
+    fn rom_mul(self, b: Self) -> Self {
+        rom_data::double_funcs::dmul(self, b)
+    }
+}
+
+fn mul<F: Float + ROMMul>(a: F, b: F) -> F {
+    if a.is_not_finite() {
+        if b.is_zero() {
+            // [-]inf/NaN * 0 = NaN
+            return F::NAN;
+        }
+
+        return if b.is_sign_negative() {
+            // [+/-]inf/NaN * (-X) = [-/+]inf/NaN
+            a.negate()
+        } else {
+            // [-]inf/NaN * X = [-]inf/NaN
+            a
+        };
+    }
+
+    if b.is_not_finite() {
+        if a.is_zero() {
+            // 0 * [-]inf/NaN = NaN
+            return F::NAN;
+        }
+
+        return if b.is_sign_negative() {
+            // (-X) * [+/-]inf/NaN = [-/+]inf/NaN
+            b.negate()
+        } else {
+            // X * [-]inf/NaN = [-]inf/NaN
+            b
+        };
+    }
+
+    a.rom_mul(b)
+}
+
+intrinsics! {
+    #[alias = __mulsf3vfp]
+    #[aeabi = __aeabi_fmul]
+    extern "C" fn __mulsf3(a: f32, b: f32) -> f32 {
+        mul(a, b)
+    }
+
+    #[bootrom_v2]
+    #[alias = __muldf3vfp]
+    #[aeabi = __aeabi_dmul]
+    extern "C" fn __muldf3(a: f64, b: f64) -> f64 {
+        mul(a, b)
+    }
+}

embassy-rp/src/lib.rs

@@ -12,6 +12,7 @@ mod intrinsics;
 
 pub mod adc;
 pub mod dma;
+mod float;
 pub mod gpio;
 pub mod i2c;
 pub mod interrupt;

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();
+}