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| -rw-r--r-- | Cargo.toml | 1 | ||||
| -rw-r--r-- | crates/std_float/Cargo.toml | 13 | ||||
| -rw-r--r-- | crates/std_float/src/lib.rs | 165 |
3 files changed, 179 insertions, 0 deletions
diff --git a/Cargo.toml b/Cargo.toml index 3f1abd73519..9802386e456 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -2,5 +2,6 @@ members = [ "crates/core_simd", + "crates/std_float", "crates/test_helpers", ] diff --git a/crates/std_float/Cargo.toml b/crates/std_float/Cargo.toml new file mode 100644 index 00000000000..82f66b8dcb7 --- /dev/null +++ b/crates/std_float/Cargo.toml @@ -0,0 +1,13 @@ +[package] +name = "std_float" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +core_simd = { path = "../core_simd" } + +[features] +default = ["as_crate"] +as_crate = [] diff --git a/crates/std_float/src/lib.rs b/crates/std_float/src/lib.rs new file mode 100644 index 00000000000..4bd4d4c05e3 --- /dev/null +++ b/crates/std_float/src/lib.rs @@ -0,0 +1,165 @@ +#![cfg_attr(feature = "as_crate", no_std)] // We are std! +#![cfg_attr( + feature = "as_crate", + feature(platform_intrinsics), + feature(portable_simd) +)] +#[cfg(not(feature = "as_crate"))] +use core::simd; +#[cfg(feature = "as_crate")] +use core_simd::simd; + +use simd::{LaneCount, Simd, SupportedLaneCount}; + +#[cfg(feature = "as_crate")] +mod experimental { + pub trait Sealed {} +} + +#[cfg(feature = "as_crate")] +use experimental as sealed; + +use crate::sealed::Sealed; + +// "platform intrinsics" are essentially "codegen intrinsics" +// each of these may be scalarized and lowered to a libm call +extern "platform-intrinsic" { + // ceil + fn simd_ceil<T>(x: T) -> T; + + // floor + fn simd_floor<T>(x: T) -> T; + + // round + fn simd_round<T>(x: T) -> T; + + // trunc + fn simd_trunc<T>(x: T) -> T; + + // fsqrt + fn simd_fsqrt<T>(x: T) -> T; + + // fma + fn simd_fma<T>(x: T, y: T, z: T) -> T; +} + +/// This trait provides a possibly-temporary implementation of float functions +/// that may, in the absence of hardware support, canonicalize to calling an +/// operating system's `math.h` dynamically-loaded library (also known as a +/// shared object). As these conditionally require runtime support, they +/// should only appear in binaries built assuming OS support: `std`. +/// +/// However, there is no reason SIMD types, in general, need OS support, +/// as for many architectures an embedded binary may simply configure that +/// support itself. This means these types must be visible in `core` +/// but have these functions available in `std`. +/// +/// [`f32`] and [`f64`] achieve a similar trick by using "lang items", but +/// due to compiler limitations, it is harder to implement this approach for +/// abstract data types like [`Simd`]. From that need, this trait is born. +/// +/// It is possible this trait will be replaced in some manner in the future, +/// when either the compiler or its supporting runtime functions are improved. +/// For now this trait is available to permit experimentation with SIMD float +/// operations that may lack hardware support, such as `mul_add`. +pub trait StdFloat: Sealed + Sized { + /// Fused multiply-add. Computes `(self * a) + b` with only one rounding error, + /// yielding a more accurate result than an unfused multiply-add. + /// + /// Using `mul_add` *may* be more performant than an unfused multiply-add if the target + /// architecture has a dedicated `fma` CPU instruction. However, this is not always + /// true, and will be heavily dependent on designing algorithms with specific target + /// hardware in mind. + #[inline] + #[must_use = "method returns a new vector and does not mutate the original value"] + fn mul_add(self, a: Self, b: Self) -> Self { + unsafe { simd_fma(self, a, b) } + } + + /// Produces a vector where every lane has the square root value + /// of the equivalently-indexed lane in `self` + #[inline] + #[must_use = "method returns a new vector and does not mutate the original value"] + fn sqrt(self) -> Self { + unsafe { simd_fsqrt(self) } + } + + /// Returns the smallest integer greater than or equal to each lane. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn ceil(self) -> Self { + unsafe { simd_ceil(self) } + } + + /// Returns the largest integer value less than or equal to each lane. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn floor(self) -> Self { + unsafe { simd_floor(self) } + } + + /// Rounds to the nearest integer value. Ties round toward zero. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn round(self) -> Self { + unsafe { simd_round(self) } + } + + /// Returns the floating point's integer value, with its fractional part removed. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn trunc(self) -> Self { + unsafe { simd_trunc(self) } + } + + /// Returns the floating point's fractional value, with its integer part removed. + #[must_use = "method returns a new vector and does not mutate the original value"] + fn fract(self) -> Self; +} + +impl<const N: usize> Sealed for Simd<f32, N> where LaneCount<N>: SupportedLaneCount {} +impl<const N: usize> Sealed for Simd<f64, N> where LaneCount<N>: SupportedLaneCount {} + +// We can safely just use all the defaults. +impl<const N: usize> StdFloat for Simd<f32, N> +where + LaneCount<N>: SupportedLaneCount, +{ + /// Returns the floating point's fractional value, with its integer part removed. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn fract(self) -> Self { + self - self.trunc() + } +} + +impl<const N: usize> StdFloat for Simd<f64, N> +where + LaneCount<N>: SupportedLaneCount, +{ + /// Returns the floating point's fractional value, with its integer part removed. + #[must_use = "method returns a new vector and does not mutate the original value"] + #[inline] + fn fract(self) -> Self { + self - self.trunc() + } +} + +#[cfg(test)] +mod tests { + use super::*; + use simd::*; + + #[test] + fn everything_works() { + let x = f32x4::from_array([0.1, 0.5, 0.6, -1.5]); + let x2 = x + x; + let _xc = x.ceil(); + let _xf = x.floor(); + let _xr = x.round(); + let _xt = x.trunc(); + let _xfma = x.mul_add(x, x); + let _xsqrt = x.sqrt(); + let _ = x2.abs() * x2; + } +} |