96 lines
1.8 KiB
Rust
96 lines
1.8 KiB
Rust
use core::ops::{Add, Mul, Neg};
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pub fn abs<T>(x: T) -> T
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where
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T: PartialOrd + Default + Neg<Output = T>,
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{
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if x >= T::default() {
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x
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} else {
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-x
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}
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}
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// These are implemented here because core::f32 doesn't have them (yet).
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// They are naive and don't handle inf/nan.
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// `compiler-intrinsics`/llvm should have better (robust, universal, and
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// faster) implementations.
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pub fn copysign<T>(x: T, y: T) -> T
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where
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T: PartialOrd + Default + Neg<Output = T>,
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{
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if (x >= T::default() && y >= T::default())
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|| (x <= T::default() && y <= T::default())
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{
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x
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} else {
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-x
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}
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}
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#[cfg(not(feature = "nightly"))]
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pub fn max<T>(x: T, y: T) -> T
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where
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T: PartialOrd,
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{
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if x > y {
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x
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} else {
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y
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}
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}
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#[cfg(not(feature = "nightly"))]
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pub fn min<T>(x: T, y: T) -> T
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where
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T: PartialOrd,
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{
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if x < y {
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x
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} else {
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y
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}
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}
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#[cfg(feature = "nightly")]
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pub fn max(x: f32, y: f32) -> f32 {
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core::intrinsics::maxnumf32(x, y)
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}
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#[cfg(feature = "nightly")]
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pub fn min(x: f32, y: f32) -> f32 {
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core::intrinsics::minnumf32(x, y)
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}
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// Multiply-accumulate vectors `x` and `a`.
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//
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// A.k.a. dot product.
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// Rust/LLVM optimize this nicely.
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pub fn macc<T>(y0: T, x: &[T], a: &[T]) -> T
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where
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T: Add<Output = T> + Mul<Output = T> + Copy,
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{
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x.iter()
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.zip(a)
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.map(|(x, a)| *x * *a)
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.fold(y0, |y, xa| y + xa)
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}
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/// Combine high and low i32 into a single downscaled i32, saturating the type.
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pub fn saturating_scale(lo: i32, hi: i32, shift: u32) -> i32 {
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debug_assert!(shift & 31 == shift);
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let shift_hi = 31 - shift;
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debug_assert!(shift_hi & 31 == shift_hi);
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let over = hi >> shift;
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if over < -1 {
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i32::MIN
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} else if over > 0 {
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i32::MAX
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} else {
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(lo >> shift) + (hi << shift_hi)
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}
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}
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