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| author | Trevor Gross <tmgross@umich.edu> | 2025-04-19 21:09:49 +0000 |
|---|---|---|
| committer | Trevor Gross <t.gross35@gmail.com> | 2025-04-19 17:20:24 -0400 |
| commit | 8b8bd8a0fd75e43a9b282284b849e651828ceec2 (patch) | |
| tree | cc6eba464cba2cb43a51c912a97029a01572a7e0 /library/compiler-builtins/libm/src/math/generic | |
| parent | 911a70381a9e7c84400b156e3cbcd805f3e64034 (diff) | |
| download | rust-8b8bd8a0fd75e43a9b282284b849e651828ceec2.tar.gz rust-8b8bd8a0fd75e43a9b282284b849e651828ceec2.zip | |
libm: Flatten the `libm/libm` directory
Diffstat (limited to 'library/compiler-builtins/libm/src/math/generic')
18 files changed, 1623 insertions, 0 deletions
diff --git a/library/compiler-builtins/libm/src/math/generic/ceil.rs b/library/compiler-builtins/libm/src/math/generic/ceil.rs new file mode 100644 index 00000000000..5c5bb47638f --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/ceil.rs @@ -0,0 +1,168 @@ +/* SPDX-License-Identifier: MIT */ +/* origin: musl src/math/ceilf.c */ + +//! Generic `ceil` algorithm. +//! +//! Note that this uses the algorithm from musl's `ceilf` rather than `ceil` or `ceill` because +//! performance seems to be better (based on icount) and it does not seem to experience rounding +//! errors on i386. + +use super::super::support::{FpResult, Status}; +use super::super::{Float, Int, IntTy, MinInt}; + +#[inline] +pub fn ceil<F: Float>(x: F) -> F { + ceil_status(x).val +} + +#[inline] +pub fn ceil_status<F: Float>(x: F) -> FpResult<F> { + let zero = IntTy::<F>::ZERO; + + let mut ix = x.to_bits(); + let e = x.exp_unbiased(); + + // If the represented value has no fractional part, no truncation is needed. + if e >= F::SIG_BITS as i32 { + return FpResult::ok(x); + } + + let status; + let res = if e >= 0 { + // |x| >= 1.0 + let m = F::SIG_MASK >> e.unsigned(); + if (ix & m) == zero { + // Portion to be masked is already zero; no adjustment needed. + return FpResult::ok(x); + } + + // Otherwise, raise an inexact exception. + status = Status::INEXACT; + + if x.is_sign_positive() { + ix += m; + } + + ix &= !m; + F::from_bits(ix) + } else { + // |x| < 1.0, raise an inexact exception since truncation will happen (unless x == 0). + if ix & F::SIG_MASK == F::Int::ZERO { + status = Status::OK; + } else { + status = Status::INEXACT; + } + + if x.is_sign_negative() { + // -1.0 < x <= -0.0; rounding up goes toward -0.0. + F::NEG_ZERO + } else if ix << 1 != zero { + // 0.0 < x < 1.0; rounding up goes toward +1.0. + F::ONE + } else { + // +0.0 remains unchanged + x + } + }; + + FpResult::new(res, status) +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::support::Hexf; + + /// Test against https://en.cppreference.com/w/cpp/numeric/math/ceil + fn spec_test<F: Float>(cases: &[(F, F, Status)]) { + let roundtrip = [F::ZERO, F::ONE, F::NEG_ONE, F::NEG_ZERO, F::INFINITY, F::NEG_INFINITY]; + + for x in roundtrip { + let FpResult { val, status } = ceil_status(x); + assert_biteq!(val, x, "{}", Hexf(x)); + assert_eq!(status, Status::OK, "{}", Hexf(x)); + } + + for &(x, res, res_stat) in cases { + let FpResult { val, status } = ceil_status(x); + assert_biteq!(val, res, "{}", Hexf(x)); + assert_eq!(status, res_stat, "{}", Hexf(x)); + } + } + + /* Skipping f16 / f128 "sanity_check"s due to rejected literal lexing at MSRV */ + + #[test] + #[cfg(f16_enabled)] + fn spec_tests_f16() { + let cases = [ + (0.1, 1.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 1.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 2.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 2.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f16>(&cases); + } + + #[test] + fn sanity_check_f32() { + assert_eq!(ceil(1.1f32), 2.0); + assert_eq!(ceil(2.9f32), 3.0); + } + + #[test] + fn spec_tests_f32() { + let cases = [ + (0.1, 1.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 1.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 2.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 2.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f32>(&cases); + } + + #[test] + fn sanity_check_f64() { + assert_eq!(ceil(1.1f64), 2.0); + assert_eq!(ceil(2.9f64), 3.0); + } + + #[test] + fn spec_tests_f64() { + let cases = [ + (0.1, 1.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 1.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 2.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 2.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f64>(&cases); + } + + #[test] + #[cfg(f128_enabled)] + fn spec_tests_f128() { + let cases = [ + (0.1, 1.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 1.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 2.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 2.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f128>(&cases); + } +} diff --git a/library/compiler-builtins/libm/src/math/generic/copysign.rs b/library/compiler-builtins/libm/src/math/generic/copysign.rs new file mode 100644 index 00000000000..a61af22f04a --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/copysign.rs @@ -0,0 +1,11 @@ +use super::super::Float; + +/// Copy the sign of `y` to `x`. +#[inline] +pub fn copysign<F: Float>(x: F, y: F) -> F { + let mut ux = x.to_bits(); + let uy = y.to_bits(); + ux &= !F::SIGN_MASK; + ux |= uy & F::SIGN_MASK; + F::from_bits(ux) +} diff --git a/library/compiler-builtins/libm/src/math/generic/fabs.rs b/library/compiler-builtins/libm/src/math/generic/fabs.rs new file mode 100644 index 00000000000..0fa0edf9b87 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fabs.rs @@ -0,0 +1,8 @@ +use super::super::Float; + +/// Absolute value. +#[inline] +pub fn fabs<F: Float>(x: F) -> F { + let abs_mask = !F::SIGN_MASK; + F::from_bits(x.to_bits() & abs_mask) +} diff --git a/library/compiler-builtins/libm/src/math/generic/fdim.rs b/library/compiler-builtins/libm/src/math/generic/fdim.rs new file mode 100644 index 00000000000..a63007b191c --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fdim.rs @@ -0,0 +1,6 @@ +use super::super::Float; + +#[inline] +pub fn fdim<F: Float>(x: F, y: F) -> F { + if x <= y { F::ZERO } else { x - y } +} diff --git a/library/compiler-builtins/libm/src/math/generic/floor.rs b/library/compiler-builtins/libm/src/math/generic/floor.rs new file mode 100644 index 00000000000..2438046254f --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/floor.rs @@ -0,0 +1,151 @@ +/* SPDX-License-Identifier: MIT + * origin: musl src/math/floor.c */ + +//! Generic `floor` algorithm. +//! +//! Note that this uses the algorithm from musl's `floorf` rather than `floor` or `floorl` because +//! performance seems to be better (based on icount) and it does not seem to experience rounding +//! errors on i386. + +use super::super::support::{FpResult, Status}; +use super::super::{Float, Int, IntTy, MinInt}; + +#[inline] +pub fn floor<F: Float>(x: F) -> F { + floor_status(x).val +} + +#[inline] +pub fn floor_status<F: Float>(x: F) -> FpResult<F> { + let zero = IntTy::<F>::ZERO; + + let mut ix = x.to_bits(); + let e = x.exp_unbiased(); + + // If the represented value has no fractional part, no truncation is needed. + if e >= F::SIG_BITS as i32 { + return FpResult::ok(x); + } + + let status; + let res = if e >= 0 { + // |x| >= 1.0 + let m = F::SIG_MASK >> e.unsigned(); + if ix & m == zero { + // Portion to be masked is already zero; no adjustment needed. + return FpResult::ok(x); + } + + // Otherwise, raise an inexact exception. + status = Status::INEXACT; + + if x.is_sign_negative() { + ix += m; + } + + ix &= !m; + F::from_bits(ix) + } else { + // |x| < 1.0, raise an inexact exception since truncation will happen. + if ix & F::SIG_MASK == F::Int::ZERO { + status = Status::OK; + } else { + status = Status::INEXACT; + } + + if x.is_sign_positive() { + // 0.0 <= x < 1.0; rounding down goes toward +0.0. + F::ZERO + } else if ix << 1 != zero { + // -1.0 < x < 0.0; rounding down goes toward -1.0. + F::NEG_ONE + } else { + // -0.0 remains unchanged + x + } + }; + + FpResult::new(res, status) +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::support::Hexf; + + /// Test against https://en.cppreference.com/w/cpp/numeric/math/floor + fn spec_test<F: Float>(cases: &[(F, F, Status)]) { + let roundtrip = [F::ZERO, F::ONE, F::NEG_ONE, F::NEG_ZERO, F::INFINITY, F::NEG_INFINITY]; + + for x in roundtrip { + let FpResult { val, status } = floor_status(x); + assert_biteq!(val, x, "{}", Hexf(x)); + assert_eq!(status, Status::OK, "{}", Hexf(x)); + } + + for &(x, res, res_stat) in cases { + let FpResult { val, status } = floor_status(x); + assert_biteq!(val, res, "{}", Hexf(x)); + assert_eq!(status, res_stat, "{}", Hexf(x)); + } + } + + /* Skipping f16 / f128 "sanity_check"s and spec cases due to rejected literal lexing at MSRV */ + + #[test] + #[cfg(f16_enabled)] + fn spec_tests_f16() { + let cases = []; + spec_test::<f16>(&cases); + } + + #[test] + fn sanity_check_f32() { + assert_eq!(floor(0.5f32), 0.0); + assert_eq!(floor(1.1f32), 1.0); + assert_eq!(floor(2.9f32), 2.0); + } + + #[test] + fn spec_tests_f32() { + let cases = [ + (0.1, 0.0, Status::INEXACT), + (-0.1, -1.0, Status::INEXACT), + (0.9, 0.0, Status::INEXACT), + (-0.9, -1.0, Status::INEXACT), + (1.1, 1.0, Status::INEXACT), + (-1.1, -2.0, Status::INEXACT), + (1.9, 1.0, Status::INEXACT), + (-1.9, -2.0, Status::INEXACT), + ]; + spec_test::<f32>(&cases); + } + + #[test] + fn sanity_check_f64() { + assert_eq!(floor(1.1f64), 1.0); + assert_eq!(floor(2.9f64), 2.0); + } + + #[test] + fn spec_tests_f64() { + let cases = [ + (0.1, 0.0, Status::INEXACT), + (-0.1, -1.0, Status::INEXACT), + (0.9, 0.0, Status::INEXACT), + (-0.9, -1.0, Status::INEXACT), + (1.1, 1.0, Status::INEXACT), + (-1.1, -2.0, Status::INEXACT), + (1.9, 1.0, Status::INEXACT), + (-1.9, -2.0, Status::INEXACT), + ]; + spec_test::<f64>(&cases); + } + + #[test] + #[cfg(f128_enabled)] + fn spec_tests_f128() { + let cases = []; + spec_test::<f128>(&cases); + } +} diff --git a/library/compiler-builtins/libm/src/math/generic/fmax.rs b/library/compiler-builtins/libm/src/math/generic/fmax.rs new file mode 100644 index 00000000000..bf3f847e89b --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fmax.rs @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2011 `maxNum`. This has been superseded by IEEE 754-2019 `maximumNumber`. +//! +//! Per the spec, returns the canonicalized result of: +//! - `x` if `x > y` +//! - `y` if `y > x` +//! - The other number if one is NaN +//! - Otherwise, either `x` or `y`, canonicalized +//! - -0.0 and +0.0 may be disregarded (unlike newer operations) +//! +//! Excluded from our implementation is sNaN handling. +//! +//! More on the differences: [link]. +//! +//! [link]: https://grouper.ieee.org/groups/msc/ANSI_IEEE-Std-754-2019/background/minNum_maxNum_Removal_Demotion_v3.pdf + +use super::super::Float; + +#[inline] +pub fn fmax<F: Float>(x: F, y: F) -> F { + let res = if x.is_nan() || x < y { y } else { x }; + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fmaximum.rs b/library/compiler-builtins/libm/src/math/generic/fmaximum.rs new file mode 100644 index 00000000000..387055af29c --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fmaximum.rs @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2019 `maximum`. +//! +//! Per the spec, returns the canonicalized result of: +//! - `x` if `x > y` +//! - `y` if `y > x` +//! - qNaN if either operation is NaN +//! - Logic following +0.0 > -0.0 +//! +//! Excluded from our implementation is sNaN handling. + +use super::super::Float; + +#[inline] +pub fn fmaximum<F: Float>(x: F, y: F) -> F { + let res = if x.is_nan() { + x + } else if y.is_nan() { + y + } else if x > y || (y.to_bits() == F::NEG_ZERO.to_bits() && x.is_sign_positive()) { + x + } else { + y + }; + + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fmaximum_num.rs b/library/compiler-builtins/libm/src/math/generic/fmaximum_num.rs new file mode 100644 index 00000000000..f7efdde80ea --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fmaximum_num.rs @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2019 `maximumNumber`. +//! +//! Per the spec, returns: +//! - `x` if `x > y` +//! - `y` if `y > x` +//! - Non-NaN if one operand is NaN +//! - Logic following +0.0 > -0.0 +//! - Either `x` or `y` if `x == y` and the signs are the same +//! - qNaN if either operand is a NaN +//! +//! Excluded from our implementation is sNaN handling. + +use super::super::Float; + +#[inline] +pub fn fmaximum_num<F: Float>(x: F, y: F) -> F { + let res = + if x.is_nan() || x < y || (x.to_bits() == F::NEG_ZERO.to_bits() && y.is_sign_positive()) { + y + } else { + x + }; + + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fmin.rs b/library/compiler-builtins/libm/src/math/generic/fmin.rs new file mode 100644 index 00000000000..cd3caeee4f2 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fmin.rs @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2008 `minNum`. This has been superseded by IEEE 754-2019 `minimumNumber`. +//! +//! Per the spec, returns the canonicalized result of: +//! - `x` if `x < y` +//! - `y` if `y < x` +//! - The other number if one is NaN +//! - Otherwise, either `x` or `y`, canonicalized +//! - -0.0 and +0.0 may be disregarded (unlike newer operations) +//! +//! Excluded from our implementation is sNaN handling. +//! +//! More on the differences: [link]. +//! +//! [link]: https://grouper.ieee.org/groups/msc/ANSI_IEEE-Std-754-2019/background/minNum_maxNum_Removal_Demotion_v3.pdf + +use super::super::Float; + +#[inline] +pub fn fmin<F: Float>(x: F, y: F) -> F { + let res = if y.is_nan() || x < y { x } else { y }; + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fminimum.rs b/library/compiler-builtins/libm/src/math/generic/fminimum.rs new file mode 100644 index 00000000000..4ddb3645506 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fminimum.rs @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2019 `minimum`. +//! +//! Per the spec, returns the canonicalized result of: +//! - `x` if `x < y` +//! - `y` if `y < x` +//! - qNaN if either operation is NaN +//! - Logic following +0.0 > -0.0 +//! +//! Excluded from our implementation is sNaN handling. + +use super::super::Float; + +#[inline] +pub fn fminimum<F: Float>(x: F, y: F) -> F { + let res = if x.is_nan() { + x + } else if y.is_nan() { + y + } else if x < y || (x.to_bits() == F::NEG_ZERO.to_bits() && y.is_sign_positive()) { + x + } else { + y + }; + + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fminimum_num.rs b/library/compiler-builtins/libm/src/math/generic/fminimum_num.rs new file mode 100644 index 00000000000..441c204a921 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fminimum_num.rs @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: MIT OR Apache-2.0 */ +//! IEEE 754-2019 `minimum`. +//! +//! Per the spec, returns: +//! - `x` if `x < y` +//! - `y` if `y < x` +//! - Non-NaN if one operand is NaN +//! - Logic following +0.0 > -0.0 +//! - Either `x` or `y` if `x == y` and the signs are the same +//! - qNaN if either operand is a NaN +//! +//! Excluded from our implementation is sNaN handling. + +use super::super::Float; + +#[inline] +pub fn fminimum_num<F: Float>(x: F, y: F) -> F { + let res = + if y.is_nan() || x < y || (x.to_bits() == F::NEG_ZERO.to_bits() && y.is_sign_positive()) { + x + } else { + y + }; + + // Canonicalize + res * F::ONE +} diff --git a/library/compiler-builtins/libm/src/math/generic/fmod.rs b/library/compiler-builtins/libm/src/math/generic/fmod.rs new file mode 100644 index 00000000000..6414bbd2508 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/fmod.rs @@ -0,0 +1,84 @@ +/* SPDX-License-Identifier: MIT */ +/* origin: musl src/math/fmod.c. Ported to generic Rust algorithm in 2025, TG. */ + +use super::super::{CastFrom, Float, Int, MinInt}; + +#[inline] +pub fn fmod<F: Float>(x: F, y: F) -> F { + let zero = F::Int::ZERO; + let one = F::Int::ONE; + let mut ix = x.to_bits(); + let mut iy = y.to_bits(); + let mut ex = x.ex().signed(); + let mut ey = y.ex().signed(); + let sx = ix & F::SIGN_MASK; + + if iy << 1 == zero || y.is_nan() || ex == F::EXP_SAT as i32 { + return (x * y) / (x * y); + } + + if ix << 1 <= iy << 1 { + if ix << 1 == iy << 1 { + return F::ZERO * x; + } + return x; + } + + /* normalize x and y */ + if ex == 0 { + let i = ix << (F::EXP_BITS + 1); + ex -= i.leading_zeros() as i32; + ix <<= -ex + 1; + } else { + ix &= F::Int::MAX >> F::EXP_BITS; + ix |= one << F::SIG_BITS; + } + + if ey == 0 { + let i = iy << (F::EXP_BITS + 1); + ey -= i.leading_zeros() as i32; + iy <<= -ey + 1; + } else { + iy &= F::Int::MAX >> F::EXP_BITS; + iy |= one << F::SIG_BITS; + } + + /* x mod y */ + while ex > ey { + let i = ix.wrapping_sub(iy); + if i >> (F::BITS - 1) == zero { + if i == zero { + return F::ZERO * x; + } + ix = i; + } + + ix <<= 1; + ex -= 1; + } + + let i = ix.wrapping_sub(iy); + if i >> (F::BITS - 1) == zero { + if i == zero { + return F::ZERO * x; + } + + ix = i; + } + + let shift = ix.leading_zeros().saturating_sub(F::EXP_BITS); + ix <<= shift; + ex -= shift as i32; + + /* scale result */ + if ex > 0 { + ix -= one << F::SIG_BITS; + ix |= F::Int::cast_from(ex) << F::SIG_BITS; + } else { + ix >>= -ex + 1; + } + + ix |= sx; + + F::from_bits(ix) +} diff --git a/library/compiler-builtins/libm/src/math/generic/mod.rs b/library/compiler-builtins/libm/src/math/generic/mod.rs new file mode 100644 index 00000000000..35846351a6e --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/mod.rs @@ -0,0 +1,38 @@ +// Note: generic functions are marked `#[inline]` because, even though generic functions are +// typically inlined, this does not seem to always be the case. + +mod ceil; +mod copysign; +mod fabs; +mod fdim; +mod floor; +mod fmax; +mod fmaximum; +mod fmaximum_num; +mod fmin; +mod fminimum; +mod fminimum_num; +mod fmod; +mod rint; +mod round; +mod scalbn; +mod sqrt; +mod trunc; + +pub use ceil::ceil; +pub use copysign::copysign; +pub use fabs::fabs; +pub use fdim::fdim; +pub use floor::floor; +pub use fmax::fmax; +pub use fmaximum::fmaximum; +pub use fmaximum_num::fmaximum_num; +pub use fmin::fmin; +pub use fminimum::fminimum; +pub use fminimum_num::fminimum_num; +pub use fmod::fmod; +pub use rint::rint_round; +pub use round::round; +pub use scalbn::scalbn; +pub use sqrt::sqrt; +pub use trunc::trunc; diff --git a/library/compiler-builtins/libm/src/math/generic/rint.rs b/library/compiler-builtins/libm/src/math/generic/rint.rs new file mode 100644 index 00000000000..9cdeb1185a8 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/rint.rs @@ -0,0 +1,120 @@ +/* SPDX-License-Identifier: MIT */ +/* origin: musl src/math/rint.c */ + +use super::super::Float; +use super::super::support::{FpResult, Round}; + +/// IEEE 754-2019 `roundToIntegralExact`, which respects rounding mode and raises inexact if +/// applicable. +#[inline] +pub fn rint_round<F: Float>(x: F, _round: Round) -> FpResult<F> { + let toint = F::ONE / F::EPSILON; + let e = x.ex(); + let positive = x.is_sign_positive(); + + // On i386 `force_eval!` must be used to force rounding via storage to memory. Otherwise, + // the excess precission from x87 would cause an incorrect final result. + let force = |x| { + if cfg!(x86_no_sse) && (F::BITS == 32 || F::BITS == 64) { force_eval!(x) } else { x } + }; + + let res = if e >= F::EXP_BIAS + F::SIG_BITS { + // No fractional part; exact result can be returned. + x + } else { + // Apply a net-zero adjustment that nudges `y` in the direction of the rounding mode. For + // Rust this is always nearest, but ideally it would take `round` into account. + let y = if positive { + force(force(x) + toint) - toint + } else { + force(force(x) - toint) + toint + }; + + if y == F::ZERO { + // A zero result takes the sign of the input. + if positive { F::ZERO } else { F::NEG_ZERO } + } else { + y + } + }; + + FpResult::ok(res) +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::support::{Hexf, Status}; + + fn spec_test<F: Float>(cases: &[(F, F, Status)]) { + let roundtrip = [F::ZERO, F::ONE, F::NEG_ONE, F::NEG_ZERO, F::INFINITY, F::NEG_INFINITY]; + + for x in roundtrip { + let FpResult { val, status } = rint_round(x, Round::Nearest); + assert_biteq!(val, x, "rint_round({})", Hexf(x)); + assert_eq!(status, Status::OK, "{}", Hexf(x)); + } + + for &(x, res, res_stat) in cases { + let FpResult { val, status } = rint_round(x, Round::Nearest); + assert_biteq!(val, res, "rint_round({})", Hexf(x)); + assert_eq!(status, res_stat, "{}", Hexf(x)); + } + } + + #[test] + #[cfg(f16_enabled)] + fn spec_tests_f16() { + let cases = []; + spec_test::<f16>(&cases); + } + + #[test] + fn spec_tests_f32() { + let cases = [ + (0.1, 0.0, Status::OK), + (-0.1, -0.0, Status::OK), + (0.5, 0.0, Status::OK), + (-0.5, -0.0, Status::OK), + (0.9, 1.0, Status::OK), + (-0.9, -1.0, Status::OK), + (1.1, 1.0, Status::OK), + (-1.1, -1.0, Status::OK), + (1.5, 2.0, Status::OK), + (-1.5, -2.0, Status::OK), + (1.9, 2.0, Status::OK), + (-1.9, -2.0, Status::OK), + (2.8, 3.0, Status::OK), + (-2.8, -3.0, Status::OK), + ]; + spec_test::<f32>(&cases); + } + + #[test] + fn spec_tests_f64() { + let cases = [ + (0.1, 0.0, Status::OK), + (-0.1, -0.0, Status::OK), + (0.5, 0.0, Status::OK), + (-0.5, -0.0, Status::OK), + (0.9, 1.0, Status::OK), + (-0.9, -1.0, Status::OK), + (1.1, 1.0, Status::OK), + (-1.1, -1.0, Status::OK), + (1.5, 2.0, Status::OK), + (-1.5, -2.0, Status::OK), + (1.9, 2.0, Status::OK), + (-1.9, -2.0, Status::OK), + (2.8, 3.0, Status::OK), + (-2.8, -3.0, Status::OK), + ]; + spec_test::<f64>(&cases); + } + + #[test] + #[cfg(f128_enabled)] + fn spec_tests_f128() { + let cases = []; + spec_test::<f128>(&cases); + } +} diff --git a/library/compiler-builtins/libm/src/math/generic/round.rs b/library/compiler-builtins/libm/src/math/generic/round.rs new file mode 100644 index 00000000000..01314ac70c2 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/round.rs @@ -0,0 +1,83 @@ +use super::super::{Float, MinInt}; +use super::{copysign, trunc}; + +#[inline] +pub fn round<F: Float>(x: F) -> F { + let f0p5 = F::from_parts(false, F::EXP_BIAS - 1, F::Int::ZERO); // 0.5 + let f0p25 = F::from_parts(false, F::EXP_BIAS - 2, F::Int::ZERO); // 0.25 + + trunc(x + copysign(f0p5 - f0p25 * F::EPSILON, x)) +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + #[cfg(f16_enabled)] + fn zeroes_f16() { + assert_biteq!(round(0.0_f16), 0.0_f16); + assert_biteq!(round(-0.0_f16), -0.0_f16); + } + + #[test] + #[cfg(f16_enabled)] + fn sanity_check_f16() { + assert_eq!(round(-1.0_f16), -1.0); + assert_eq!(round(2.8_f16), 3.0); + assert_eq!(round(-0.5_f16), -1.0); + assert_eq!(round(0.5_f16), 1.0); + assert_eq!(round(-1.5_f16), -2.0); + assert_eq!(round(1.5_f16), 2.0); + } + + #[test] + fn zeroes_f32() { + assert_biteq!(round(0.0_f32), 0.0_f32); + assert_biteq!(round(-0.0_f32), -0.0_f32); + } + + #[test] + fn sanity_check_f32() { + assert_eq!(round(-1.0_f32), -1.0); + assert_eq!(round(2.8_f32), 3.0); + assert_eq!(round(-0.5_f32), -1.0); + assert_eq!(round(0.5_f32), 1.0); + assert_eq!(round(-1.5_f32), -2.0); + assert_eq!(round(1.5_f32), 2.0); + } + + #[test] + fn zeroes_f64() { + assert_biteq!(round(0.0_f64), 0.0_f64); + assert_biteq!(round(-0.0_f64), -0.0_f64); + } + + #[test] + fn sanity_check_f64() { + assert_eq!(round(-1.0_f64), -1.0); + assert_eq!(round(2.8_f64), 3.0); + assert_eq!(round(-0.5_f64), -1.0); + assert_eq!(round(0.5_f64), 1.0); + assert_eq!(round(-1.5_f64), -2.0); + assert_eq!(round(1.5_f64), 2.0); + } + + #[test] + #[cfg(f128_enabled)] + fn zeroes_f128() { + assert_biteq!(round(0.0_f128), 0.0_f128); + assert_biteq!(round(-0.0_f128), -0.0_f128); + } + + #[test] + #[cfg(f128_enabled)] + fn sanity_check_f128() { + assert_eq!(round(-1.0_f128), -1.0); + assert_eq!(round(2.8_f128), 3.0); + assert_eq!(round(-0.5_f128), -1.0); + assert_eq!(round(0.5_f128), 1.0); + assert_eq!(round(-1.5_f128), -2.0); + assert_eq!(round(1.5_f128), 2.0); + } +} diff --git a/library/compiler-builtins/libm/src/math/generic/scalbn.rs b/library/compiler-builtins/libm/src/math/generic/scalbn.rs new file mode 100644 index 00000000000..a45db1b4a02 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/scalbn.rs @@ -0,0 +1,121 @@ +use super::super::{CastFrom, CastInto, Float, IntTy, MinInt}; + +/// Scale the exponent. +/// +/// From N3220: +/// +/// > The scalbn and scalbln functions compute `x * b^n`, where `b = FLT_RADIX` if the return type +/// > of the function is a standard floating type, or `b = 10` if the return type of the function +/// > is a decimal floating type. A range error occurs for some finite x, depending on n. +/// > +/// > [...] +/// > +/// > * `scalbn(±0, n)` returns `±0`. +/// > * `scalbn(x, 0)` returns `x`. +/// > * `scalbn(±∞, n)` returns `±∞`. +/// > +/// > If the calculation does not overflow or underflow, the returned value is exact and +/// > independent of the current rounding direction mode. +#[inline] +pub fn scalbn<F: Float>(mut x: F, mut n: i32) -> F +where + u32: CastInto<F::Int>, + F::Int: CastFrom<i32>, + F::Int: CastFrom<u32>, +{ + let zero = IntTy::<F>::ZERO; + + // Bits including the implicit bit + let sig_total_bits = F::SIG_BITS + 1; + + // Maximum and minimum values when biased + let exp_max = F::EXP_MAX; + let exp_min = F::EXP_MIN; + + // 2 ^ Emax, maximum positive with null significand (0x1p1023 for f64) + let f_exp_max = F::from_parts(false, F::EXP_BIAS << 1, zero); + + // 2 ^ Emin, minimum positive normal with null significand (0x1p-1022 for f64) + let f_exp_min = F::from_parts(false, 1, zero); + + // 2 ^ sig_total_bits, moltiplier to normalize subnormals (0x1p53 for f64) + let f_pow_subnorm = F::from_parts(false, sig_total_bits + F::EXP_BIAS, zero); + + /* + * The goal is to multiply `x` by a scale factor that applies `n`. However, there are cases + * where `2^n` is not representable by `F` but the result should be, e.g. `x = 2^Emin` with + * `n = -EMin + 2` (one out of range of 2^Emax). To get around this, reduce the magnitude of + * the final scale operation by prescaling by the max/min power representable by `F`. + */ + + if n > exp_max { + // Worse case positive `n`: `x` is the minimum subnormal value, the result is `F::MAX`. + // This can be reached by three scaling multiplications (two here and one final). + debug_assert!(-exp_min + F::SIG_BITS as i32 + exp_max <= exp_max * 3); + + x *= f_exp_max; + n -= exp_max; + if n > exp_max { + x *= f_exp_max; + n -= exp_max; + if n > exp_max { + n = exp_max; + } + } + } else if n < exp_min { + // When scaling toward 0, the prescaling is limited to a value that does not allow `x` to + // go subnormal. This avoids double rounding. + if F::BITS > 16 { + // `mul` s.t. `!(x * mul).is_subnormal() ∀ x` + let mul = f_exp_min * f_pow_subnorm; + let add = -exp_min - sig_total_bits as i32; + + // Worse case negative `n`: `x` is the maximum positive value, the result is `F::MIN`. + // This must be reachable by three scaling multiplications (two here and one final). + debug_assert!(-exp_min + F::SIG_BITS as i32 + exp_max <= add * 2 + -exp_min); + + x *= mul; + n += add; + + if n < exp_min { + x *= mul; + n += add; + + if n < exp_min { + n = exp_min; + } + } + } else { + // `f16` is unique compared to other float types in that the difference between the + // minimum exponent and the significand bits (`add = -exp_min - sig_total_bits`) is + // small, only three. The above method depend on decrementing `n` by `add` two times; + // for other float types this works out because `add` is a substantial fraction of + // the exponent range. For `f16`, however, 3 is relatively small compared to the + // exponent range (which is 39), so that requires ~10 prescale rounds rather than two. + // + // Work aroudn this by using a different algorithm that calculates the prescale + // dynamically based on the maximum possible value. This adds more operations per round + // since it needs to construct the scale, but works better in the general case. + let add = -(n + sig_total_bits as i32).clamp(exp_min, sig_total_bits as i32); + let mul = F::from_parts(false, (F::EXP_BIAS as i32 - add) as u32, zero); + + x *= mul; + n += add; + + if n < exp_min { + let add = -(n + sig_total_bits as i32).clamp(exp_min, sig_total_bits as i32); + let mul = F::from_parts(false, (F::EXP_BIAS as i32 - add) as u32, zero); + + x *= mul; + n += add; + + if n < exp_min { + n = exp_min; + } + } + } + } + + let scale = F::from_parts(false, (F::EXP_BIAS as i32 + n) as u32, zero); + x * scale +} diff --git a/library/compiler-builtins/libm/src/math/generic/sqrt.rs b/library/compiler-builtins/libm/src/math/generic/sqrt.rs new file mode 100644 index 00000000000..ec9ff22df20 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/sqrt.rs @@ -0,0 +1,537 @@ +/* SPDX-License-Identifier: MIT */ +/* origin: musl src/math/sqrt.c. Ported to generic Rust algorithm in 2025, TG. */ + +//! Generic square root algorithm. +//! +//! This routine operates around `m_u2`, a U.2 (fixed point with two integral bits) mantissa +//! within the range [1, 4). A table lookup provides an initial estimate, then goldschmidt +//! iterations at various widths are used to approach the real values. +//! +//! For the iterations, `r` is a U0 number that approaches `1/sqrt(m_u2)`, and `s` is a U2 number +//! that approaches `sqrt(m_u2)`. Recall that m_u2 ∈ [1, 4). +//! +//! With Newton-Raphson iterations, this would be: +//! +//! - `w = r * r w ~ 1 / m` +//! - `u = 3 - m * w u ~ 3 - m * w = 3 - m / m = 2` +//! - `r = r * u / 2 r ~ r` +//! +//! (Note that the righthand column does not show anything analytically meaningful (i.e. r ~ r), +//! since the value of performing one iteration is in reducing the error representable by `~`). +//! +//! Instead of Newton-Raphson iterations, Goldschmidt iterations are used to calculate +//! `s = m * r`: +//! +//! - `s = m * r s ~ m / sqrt(m)` +//! - `u = 3 - s * r u ~ 3 - (m / sqrt(m)) * (1 / sqrt(m)) = 3 - m / m = 2` +//! - `r = r * u / 2 r ~ r` +//! - `s = s * u / 2 s ~ s` +//! +//! The above is precise because it uses the original value `m`. There is also a faster version +//! that performs fewer steps but does not use `m`: +//! +//! - `u = 3 - s * r u ~ 3 - 1` +//! - `r = r * u / 2 r ~ r` +//! - `s = s * u / 2 s ~ s` +//! +//! Rounding errors accumulate faster with the second version, so it is only used for subsequent +//! iterations within the same width integer. The first version is always used for the first +//! iteration at a new width in order to avoid this accumulation. +//! +//! Goldschmidt has the advantage over Newton-Raphson that `sqrt(x)` and `1/sqrt(x)` are +//! computed at the same time, i.e. there is no need to calculate `1/sqrt(x)` and invert it. + +use super::super::support::{FpResult, IntTy, Round, Status, cold_path}; +use super::super::{CastFrom, CastInto, DInt, Float, HInt, Int, MinInt}; + +#[inline] +pub fn sqrt<F>(x: F) -> F +where + F: Float + SqrtHelper, + F::Int: HInt, + F::Int: From<u8>, + F::Int: From<F::ISet2>, + F::Int: CastInto<F::ISet1>, + F::Int: CastInto<F::ISet2>, + u32: CastInto<F::Int>, +{ + sqrt_round(x, Round::Nearest).val +} + +#[inline] +pub fn sqrt_round<F>(x: F, _round: Round) -> FpResult<F> +where + F: Float + SqrtHelper, + F::Int: HInt, + F::Int: From<u8>, + F::Int: From<F::ISet2>, + F::Int: CastInto<F::ISet1>, + F::Int: CastInto<F::ISet2>, + u32: CastInto<F::Int>, +{ + let zero = IntTy::<F>::ZERO; + let one = IntTy::<F>::ONE; + + let mut ix = x.to_bits(); + + // Top is the exponent and sign, which may or may not be shifted. If the float fits into a + // `u32`, we can get by without paying shifting costs. + let noshift = F::BITS <= u32::BITS; + let (mut top, special_case) = if noshift { + let exp_lsb = one << F::SIG_BITS; + let special_case = ix.wrapping_sub(exp_lsb) >= F::EXP_MASK - exp_lsb; + (Exp::NoShift(()), special_case) + } else { + let top = u32::cast_from(ix >> F::SIG_BITS); + let special_case = top.wrapping_sub(1) >= F::EXP_SAT - 1; + (Exp::Shifted(top), special_case) + }; + + // Handle NaN, zero, and out of domain (<= 0) + if special_case { + cold_path(); + + // +/-0 + if ix << 1 == zero { + return FpResult::ok(x); + } + + // Positive infinity + if ix == F::EXP_MASK { + return FpResult::ok(x); + } + + // NaN or negative + if ix > F::EXP_MASK { + return FpResult::new(F::NAN, Status::INVALID); + } + + // Normalize subnormals by multiplying by 1.0 << SIG_BITS (e.g. 0x1p52 for doubles). + let scaled = x * F::from_parts(false, F::SIG_BITS + F::EXP_BIAS, zero); + ix = scaled.to_bits(); + match top { + Exp::Shifted(ref mut v) => { + *v = scaled.ex(); + *v = (*v).wrapping_sub(F::SIG_BITS); + } + Exp::NoShift(()) => { + ix = ix.wrapping_sub((F::SIG_BITS << F::SIG_BITS).cast()); + } + } + } + + // Reduce arguments such that `x = 4^e * m`: + // + // - m_u2 ∈ [1, 4), a fixed point U2.BITS number + // - 2^e is the exponent part of the result + let (m_u2, exp) = match top { + Exp::Shifted(top) => { + // We now know `x` is positive, so `top` is just its (biased) exponent + let mut e = top; + // Construct a fixed point representation of the mantissa. + let mut m_u2 = (ix | F::IMPLICIT_BIT) << F::EXP_BITS; + let even = (e & 1) != 0; + if even { + m_u2 >>= 1; + } + e = (e.wrapping_add(F::EXP_SAT >> 1)) >> 1; + (m_u2, Exp::Shifted(e)) + } + Exp::NoShift(()) => { + let even = ix & (one << F::SIG_BITS) != zero; + + // Exponent part of the return value + let mut e_noshift = ix >> 1; + // ey &= (F::EXP_MASK << 2) >> 2; // clear the top exponent bit (result = 1.0) + e_noshift += (F::EXP_MASK ^ (F::SIGN_MASK >> 1)) >> 1; + e_noshift &= F::EXP_MASK; + + let m1 = (ix << F::EXP_BITS) | F::SIGN_MASK; + let m0 = (ix << (F::EXP_BITS - 1)) & !F::SIGN_MASK; + let m_u2 = if even { m0 } else { m1 }; + + (m_u2, Exp::NoShift(e_noshift)) + } + }; + + // Extract the top 6 bits of the significand with the lowest bit of the exponent. + let i = usize::cast_from(ix >> (F::SIG_BITS - 6)) & 0b1111111; + + // Start with an initial guess for `r = 1 / sqrt(m)` from the table, and shift `m` as an + // initial value for `s = sqrt(m)`. See the module documentation for details. + let r1_u0: F::ISet1 = F::ISet1::cast_from(RSQRT_TAB[i]) << (F::ISet1::BITS - 16); + let s1_u2: F::ISet1 = ((m_u2) >> (F::BITS - F::ISet1::BITS)).cast(); + + // Perform iterations, if any, at quarter width (used for `f128`). + let (r1_u0, _s1_u2) = goldschmidt::<F, F::ISet1>(r1_u0, s1_u2, F::SET1_ROUNDS, false); + + // Widen values and perform iterations at half width (used for `f64` and `f128`). + let r2_u0: F::ISet2 = F::ISet2::from(r1_u0) << (F::ISet2::BITS - F::ISet1::BITS); + let s2_u2: F::ISet2 = ((m_u2) >> (F::BITS - F::ISet2::BITS)).cast(); + let (r2_u0, _s2_u2) = goldschmidt::<F, F::ISet2>(r2_u0, s2_u2, F::SET2_ROUNDS, false); + + // Perform final iterations at full width (used for all float types). + let r_u0: F::Int = F::Int::from(r2_u0) << (F::BITS - F::ISet2::BITS); + let s_u2: F::Int = m_u2; + let (_r_u0, s_u2) = goldschmidt::<F, F::Int>(r_u0, s_u2, F::FINAL_ROUNDS, true); + + // Shift back to mantissa position. + let mut m = s_u2 >> (F::EXP_BITS - 2); + + // The musl source includes the following comment (with literals replaced): + // + // > s < sqrt(m) < s + 0x1.09p-SIG_BITS + // > compute nearest rounded result: the nearest result to SIG_BITS bits is either s or + // > s+0x1p-SIG_BITS, we can decide by comparing (2^SIG_BITS s + 0.5)^2 to 2^(2*SIG_BITS) m. + // + // Expanding this with , with `SIG_BITS = p` and adjusting based on the operations done to + // `d0` and `d1`: + // + // - `2^(2p)m ≟ ((2^p)m + 0.5)^2` + // - `2^(2p)m ≟ 2^(2p)m^2 + (2^p)m + 0.25` + // - `2^(2p)m - m^2 ≟ (2^(2p) - 1)m^2 + (2^p)m + 0.25` + // - `(1 - 2^(2p))m + m^2 ≟ (1 - 2^(2p))m^2 + (1 - 2^p)m + 0.25` (?) + // + // I do not follow how the rounding bit is extracted from this comparison with the below + // operations. In any case, the algorithm is well tested. + + // The value needed to shift `m_u2` by to create `m*2^(2p)`. `2p = 2 * F::SIG_BITS`, + // `F::BITS - 2` accounts for the offset that `m_u2` already has. + let shift = 2 * F::SIG_BITS - (F::BITS - 2); + + // `2^(2p)m - m^2` + let d0 = (m_u2 << shift).wrapping_sub(m.wrapping_mul(m)); + // `m - 2^(2p)m + m^2` + let d1 = m.wrapping_sub(d0); + m += d1 >> (F::BITS - 1); + m &= F::SIG_MASK; + + match exp { + Exp::Shifted(e) => m |= IntTy::<F>::cast_from(e) << F::SIG_BITS, + Exp::NoShift(e) => m |= e, + }; + + let mut y = F::from_bits(m); + + // FIXME(f16): the fenv math does not work for `f16` + if F::BITS > 16 { + // Handle rounding and inexact. `(m + 1)^2 == 2^shift m` is exact; for all other cases, add + // a tiny value to cause fenv effects. + let d2 = d1.wrapping_add(m).wrapping_add(one); + let mut tiny = if d2 == zero { + cold_path(); + zero + } else { + F::IMPLICIT_BIT + }; + + tiny |= (d1 ^ d2) & F::SIGN_MASK; + let t = F::from_bits(tiny); + y = y + t; + } + + FpResult::ok(y) +} + +/// Multiply at the wider integer size, returning the high half. +fn wmulh<I: HInt>(a: I, b: I) -> I { + a.widen_mul(b).hi() +} + +/// Perform `count` goldschmidt iterations, returning `(r_u0, s_u?)`. +/// +/// - `r_u0` is the reciprocal `r ~ 1 / sqrt(m)`, as U0. +/// - `s_u2` is the square root, `s ~ sqrt(m)`, as U2. +/// - `count` is the number of iterations to perform. +/// - `final_set` should be true if this is the last round (same-sized integer). If so, the +/// returned `s` will be U3, for later shifting. Otherwise, the returned `s` is U2. +/// +/// Note that performance relies on the optimizer being able to unroll these loops (reasonably +/// trivial, `count` is a constant when called). +#[inline] +fn goldschmidt<F, I>(mut r_u0: I, mut s_u2: I, count: u32, final_set: bool) -> (I, I) +where + F: SqrtHelper, + I: HInt + From<u8>, +{ + let three_u2 = I::from(0b11u8) << (I::BITS - 2); + let mut u_u0 = r_u0; + + for i in 0..count { + // First iteration: `s = m*r` (`u_u0 = r_u0` set above) + // Subsequent iterations: `s=s*u/2` + s_u2 = wmulh(s_u2, u_u0); + + // Perform `s /= 2` if: + // + // 1. This is not the first iteration (the first iteration is `s = m*r`)... + // 2. ... and this is not the last set of iterations + // 3. ... or, if this is the last set, it is not the last iteration + // + // This step is not performed for the final iteration because the shift is combined with + // a later shift (moving `s` into the mantissa). + if i > 0 && (!final_set || i + 1 < count) { + s_u2 <<= 1; + } + + // u = 3 - s*r + let d_u2 = wmulh(s_u2, r_u0); + u_u0 = three_u2.wrapping_sub(d_u2); + + // r = r*u/2 + r_u0 = wmulh(r_u0, u_u0) << 1; + } + + (r_u0, s_u2) +} + +/// Representation of whether we shift the exponent into a `u32`, or modify it in place to save +/// the shift operations. +enum Exp<T> { + /// The exponent has been shifted to a `u32` and is LSB-aligned. + Shifted(u32), + /// The exponent is in its natural position in integer repr. + NoShift(T), +} + +/// Size-specific constants related to the square root routine. +pub trait SqrtHelper: Float { + /// Integer for the first set of rounds. If unused, set to the same type as the next set. + type ISet1: HInt + Into<Self::ISet2> + CastFrom<Self::Int> + From<u8>; + /// Integer for the second set of rounds. If unused, set to the same type as the next set. + type ISet2: HInt + From<Self::ISet1> + From<u8>; + + /// Number of rounds at `ISet1`. + const SET1_ROUNDS: u32 = 0; + /// Number of rounds at `ISet2`. + const SET2_ROUNDS: u32 = 0; + /// Number of rounds at `Self::Int`. + const FINAL_ROUNDS: u32; +} + +#[cfg(f16_enabled)] +impl SqrtHelper for f16 { + type ISet1 = u16; // unused + type ISet2 = u16; // unused + + const FINAL_ROUNDS: u32 = 2; +} + +impl SqrtHelper for f32 { + type ISet1 = u32; // unused + type ISet2 = u32; // unused + + const FINAL_ROUNDS: u32 = 3; +} + +impl SqrtHelper for f64 { + type ISet1 = u32; // unused + type ISet2 = u32; + + const SET2_ROUNDS: u32 = 2; + const FINAL_ROUNDS: u32 = 2; +} + +#[cfg(f128_enabled)] +impl SqrtHelper for f128 { + type ISet1 = u32; + type ISet2 = u64; + + const SET1_ROUNDS: u32 = 1; + const SET2_ROUNDS: u32 = 2; + const FINAL_ROUNDS: u32 = 2; +} + +/// A U0.16 representation of `1/sqrt(x)`. +/// +/// The index is a 7-bit number consisting of a single exponent bit and 6 bits of significand. +#[rustfmt::skip] +static RSQRT_TAB: [u16; 128] = [ + 0xb451, 0xb2f0, 0xb196, 0xb044, 0xaef9, 0xadb6, 0xac79, 0xab43, + 0xaa14, 0xa8eb, 0xa7c8, 0xa6aa, 0xa592, 0xa480, 0xa373, 0xa26b, + 0xa168, 0xa06a, 0x9f70, 0x9e7b, 0x9d8a, 0x9c9d, 0x9bb5, 0x9ad1, + 0x99f0, 0x9913, 0x983a, 0x9765, 0x9693, 0x95c4, 0x94f8, 0x9430, + 0x936b, 0x92a9, 0x91ea, 0x912e, 0x9075, 0x8fbe, 0x8f0a, 0x8e59, + 0x8daa, 0x8cfe, 0x8c54, 0x8bac, 0x8b07, 0x8a64, 0x89c4, 0x8925, + 0x8889, 0x87ee, 0x8756, 0x86c0, 0x862b, 0x8599, 0x8508, 0x8479, + 0x83ec, 0x8361, 0x82d8, 0x8250, 0x81c9, 0x8145, 0x80c2, 0x8040, + 0xff02, 0xfd0e, 0xfb25, 0xf947, 0xf773, 0xf5aa, 0xf3ea, 0xf234, + 0xf087, 0xeee3, 0xed47, 0xebb3, 0xea27, 0xe8a3, 0xe727, 0xe5b2, + 0xe443, 0xe2dc, 0xe17a, 0xe020, 0xdecb, 0xdd7d, 0xdc34, 0xdaf1, + 0xd9b3, 0xd87b, 0xd748, 0xd61a, 0xd4f1, 0xd3cd, 0xd2ad, 0xd192, + 0xd07b, 0xcf69, 0xce5b, 0xcd51, 0xcc4a, 0xcb48, 0xca4a, 0xc94f, + 0xc858, 0xc764, 0xc674, 0xc587, 0xc49d, 0xc3b7, 0xc2d4, 0xc1f4, + 0xc116, 0xc03c, 0xbf65, 0xbe90, 0xbdbe, 0xbcef, 0xbc23, 0xbb59, + 0xba91, 0xb9cc, 0xb90a, 0xb84a, 0xb78c, 0xb6d0, 0xb617, 0xb560, +]; + +#[cfg(test)] +mod tests { + use super::*; + + /// Test behavior specified in IEEE 754 `squareRoot`. + fn spec_test<F>() + where + F: Float + SqrtHelper, + F::Int: HInt, + F::Int: From<u8>, + F::Int: From<F::ISet2>, + F::Int: CastInto<F::ISet1>, + F::Int: CastInto<F::ISet2>, + u32: CastInto<F::Int>, + { + // Values that should return a NaN and raise invalid + let nan = [F::NEG_INFINITY, F::NEG_ONE, F::NAN, F::MIN]; + + // Values that return unaltered + let roundtrip = [F::ZERO, F::NEG_ZERO, F::INFINITY]; + + for x in nan { + let FpResult { val, status } = sqrt_round(x, Round::Nearest); + assert!(val.is_nan()); + assert!(status == Status::INVALID); + } + + for x in roundtrip { + let FpResult { val, status } = sqrt_round(x, Round::Nearest); + assert_biteq!(val, x); + assert!(status == Status::OK); + } + } + + #[test] + #[cfg(f16_enabled)] + fn sanity_check_f16() { + assert_biteq!(sqrt(100.0f16), 10.0); + assert_biteq!(sqrt(4.0f16), 2.0); + } + + #[test] + #[cfg(f16_enabled)] + fn spec_tests_f16() { + spec_test::<f16>(); + } + + #[test] + #[cfg(f16_enabled)] + #[allow(clippy::approx_constant)] + fn conformance_tests_f16() { + let cases = [ + (f16::PI, 0x3f17_u16), + // 10_000.0, using a hex literal for MSRV hack (Rust < 1.67 checks literal widths as + // part of the AST, so the `cfg` is irrelevant here). + (f16::from_bits(0x70e2), 0x5640_u16), + (f16::from_bits(0x0000000f), 0x13bf_u16), + (f16::INFINITY, f16::INFINITY.to_bits()), + ]; + + for (input, output) in cases { + assert_biteq!( + sqrt(input), + f16::from_bits(output), + "input: {input:?} ({:#018x})", + input.to_bits() + ); + } + } + + #[test] + fn sanity_check_f32() { + assert_biteq!(sqrt(100.0f32), 10.0); + assert_biteq!(sqrt(4.0f32), 2.0); + } + + #[test] + fn spec_tests_f32() { + spec_test::<f32>(); + } + + #[test] + #[allow(clippy::approx_constant)] + fn conformance_tests_f32() { + let cases = [ + (f32::PI, 0x3fe2dfc5_u32), + (10000.0f32, 0x42c80000_u32), + (f32::from_bits(0x0000000f), 0x1b2f456f_u32), + (f32::INFINITY, f32::INFINITY.to_bits()), + ]; + + for (input, output) in cases { + assert_biteq!( + sqrt(input), + f32::from_bits(output), + "input: {input:?} ({:#018x})", + input.to_bits() + ); + } + } + + #[test] + fn sanity_check_f64() { + assert_biteq!(sqrt(100.0f64), 10.0); + assert_biteq!(sqrt(4.0f64), 2.0); + } + + #[test] + fn spec_tests_f64() { + spec_test::<f64>(); + } + + #[test] + #[allow(clippy::approx_constant)] + fn conformance_tests_f64() { + let cases = [ + (f64::PI, 0x3ffc5bf891b4ef6a_u64), + (10000.0, 0x4059000000000000_u64), + (f64::from_bits(0x0000000f), 0x1e7efbdeb14f4eda_u64), + (f64::INFINITY, f64::INFINITY.to_bits()), + ]; + + for (input, output) in cases { + assert_biteq!( + sqrt(input), + f64::from_bits(output), + "input: {input:?} ({:#018x})", + input.to_bits() + ); + } + } + + #[test] + #[cfg(f128_enabled)] + fn sanity_check_f128() { + assert_biteq!(sqrt(100.0f128), 10.0); + assert_biteq!(sqrt(4.0f128), 2.0); + } + + #[test] + #[cfg(f128_enabled)] + fn spec_tests_f128() { + spec_test::<f128>(); + } + + #[test] + #[cfg(f128_enabled)] + #[allow(clippy::approx_constant)] + fn conformance_tests_f128() { + let cases = [ + (f128::PI, 0x3fffc5bf891b4ef6aa79c3b0520d5db9_u128), + // 10_000.0, see `f16` for reasoning. + ( + f128::from_bits(0x400c3880000000000000000000000000), + 0x40059000000000000000000000000000_u128, + ), + (f128::from_bits(0x0000000f), 0x1fc9efbdeb14f4ed9b17ae807907e1e9_u128), + (f128::INFINITY, f128::INFINITY.to_bits()), + ]; + + for (input, output) in cases { + assert_biteq!( + sqrt(input), + f128::from_bits(output), + "input: {input:?} ({:#018x})", + input.to_bits() + ); + } + } +} diff --git a/library/compiler-builtins/libm/src/math/generic/trunc.rs b/library/compiler-builtins/libm/src/math/generic/trunc.rs new file mode 100644 index 00000000000..25414ecf426 --- /dev/null +++ b/library/compiler-builtins/libm/src/math/generic/trunc.rs @@ -0,0 +1,138 @@ +/* SPDX-License-Identifier: MIT + * origin: musl src/math/trunc.c */ + +use super::super::support::{FpResult, Status}; +use super::super::{Float, Int, IntTy, MinInt}; + +#[inline] +pub fn trunc<F: Float>(x: F) -> F { + trunc_status(x).val +} + +#[inline] +pub fn trunc_status<F: Float>(x: F) -> FpResult<F> { + let mut xi: F::Int = x.to_bits(); + let e: i32 = x.exp_unbiased(); + + // C1: The represented value has no fractional part, so no truncation is needed + if e >= F::SIG_BITS as i32 { + return FpResult::ok(x); + } + + let mask = if e < 0 { + // C2: If the exponent is negative, the result will be zero so we mask out everything + // except the sign. + F::SIGN_MASK + } else { + // C3: Otherwise, we mask out the last `e` bits of the significand. + !(F::SIG_MASK >> e.unsigned()) + }; + + // C4: If the to-be-masked-out portion is already zero, we have an exact result + if (xi & !mask) == IntTy::<F>::ZERO { + return FpResult::ok(x); + } + + // C5: Otherwise the result is inexact and we will truncate. Raise `FE_INEXACT`, mask the + // result, and return. + + let status = if xi & F::SIG_MASK == F::Int::ZERO { Status::OK } else { Status::INEXACT }; + xi &= mask; + FpResult::new(F::from_bits(xi), status) +} + +#[cfg(test)] +mod tests { + use super::*; + use crate::support::Hexf; + + fn spec_test<F: Float>(cases: &[(F, F, Status)]) { + let roundtrip = [F::ZERO, F::ONE, F::NEG_ONE, F::NEG_ZERO, F::INFINITY, F::NEG_INFINITY]; + + for x in roundtrip { + let FpResult { val, status } = trunc_status(x); + assert_biteq!(val, x, "{}", Hexf(x)); + assert_eq!(status, Status::OK, "{}", Hexf(x)); + } + + for &(x, res, res_stat) in cases { + let FpResult { val, status } = trunc_status(x); + assert_biteq!(val, res, "{}", Hexf(x)); + assert_eq!(status, res_stat, "{}", Hexf(x)); + } + } + + /* Skipping f16 / f128 "sanity_check"s and spec cases due to rejected literal lexing at MSRV */ + + #[test] + #[cfg(f16_enabled)] + fn spec_tests_f16() { + let cases = []; + spec_test::<f16>(&cases); + } + + #[test] + fn sanity_check_f32() { + assert_eq!(trunc(0.5f32), 0.0); + assert_eq!(trunc(1.1f32), 1.0); + assert_eq!(trunc(2.9f32), 2.0); + } + + #[test] + fn spec_tests_f32() { + let cases = [ + (0.1, 0.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 0.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 1.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 1.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f32>(&cases); + + assert_biteq!(trunc(1.1f32), 1.0); + assert_biteq!(trunc(1.1f64), 1.0); + + // C1 + assert_biteq!(trunc(hf32!("0x1p23")), hf32!("0x1p23")); + assert_biteq!(trunc(hf64!("0x1p52")), hf64!("0x1p52")); + assert_biteq!(trunc(hf32!("-0x1p23")), hf32!("-0x1p23")); + assert_biteq!(trunc(hf64!("-0x1p52")), hf64!("-0x1p52")); + + // C2 + assert_biteq!(trunc(hf32!("0x1p-1")), 0.0); + assert_biteq!(trunc(hf64!("0x1p-1")), 0.0); + assert_biteq!(trunc(hf32!("-0x1p-1")), -0.0); + assert_biteq!(trunc(hf64!("-0x1p-1")), -0.0); + } + + #[test] + fn sanity_check_f64() { + assert_eq!(trunc(1.1f64), 1.0); + assert_eq!(trunc(2.9f64), 2.0); + } + + #[test] + fn spec_tests_f64() { + let cases = [ + (0.1, 0.0, Status::INEXACT), + (-0.1, -0.0, Status::INEXACT), + (0.9, 0.0, Status::INEXACT), + (-0.9, -0.0, Status::INEXACT), + (1.1, 1.0, Status::INEXACT), + (-1.1, -1.0, Status::INEXACT), + (1.9, 1.0, Status::INEXACT), + (-1.9, -1.0, Status::INEXACT), + ]; + spec_test::<f64>(&cases); + } + + #[test] + #[cfg(f128_enabled)] + fn spec_tests_f128() { + let cases = []; + spec_test::<f128>(&cases); + } +} |
