diff options
Diffstat (limited to 'library/compiler-builtins/libm/src/math/generic/fma.rs')
| -rw-r--r-- | library/compiler-builtins/libm/src/math/generic/fma.rs | 133 |
1 files changed, 4 insertions, 129 deletions
diff --git a/library/compiler-builtins/libm/src/math/generic/fma.rs b/library/compiler-builtins/libm/src/math/generic/fma.rs index 8856e63f596..aaf459d1b61 100644 --- a/library/compiler-builtins/libm/src/math/generic/fma.rs +++ b/library/compiler-builtins/libm/src/math/generic/fma.rs @@ -1,31 +1,9 @@ /* SPDX-License-Identifier: MIT */ /* origin: musl src/math/fma.c. Ported to generic Rust algorithm in 2025, TG. */ -use super::support::{DInt, FpResult, HInt, IntTy, Round, Status}; -use super::{CastFrom, CastInto, Float, Int, MinInt}; - -/// Fused multiply add (f64) -/// -/// Computes `(x*y)+z`, rounded as one ternary operation (i.e. calculated with infinite precision). -#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] -pub fn fma(x: f64, y: f64, z: f64) -> f64 { - select_implementation! { - name: fma, - use_arch: all(target_arch = "aarch64", target_feature = "neon"), - args: x, y, z, - } - - fma_round(x, y, z, Round::Nearest).val -} - -/// Fused multiply add (f128) -/// -/// Computes `(x*y)+z`, rounded as one ternary operation (i.e. calculated with infinite precision). -#[cfg(f128_enabled)] -#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] -pub fn fmaf128(x: f128, y: f128, z: f128) -> f128 { - fma_round(x, y, z, Round::Nearest).val -} +use crate::support::{ + CastFrom, CastInto, DInt, Float, FpResult, HInt, Int, IntTy, MinInt, Round, Status, +}; /// Fused multiply-add that works when there is not a larger float size available. Computes /// `(x * y) + z`. @@ -234,7 +212,7 @@ where } // Use our exponent to scale the final value. - FpResult::new(super::generic::scalbn(r, e), status) + FpResult::new(super::scalbn(r, e), status) } /// Representation of `F` that has handled subnormals. @@ -298,106 +276,3 @@ impl<F: Float> Norm<F> { self.e > Self::ZERO_INF_NAN as i32 } } - -#[cfg(test)] -mod tests { - use super::*; - - /// Test the generic `fma_round` algorithm for a given float. - fn spec_test<F>() - where - F: Float, - F: CastFrom<F::SignedInt>, - F: CastFrom<i8>, - F::Int: HInt, - u32: CastInto<F::Int>, - { - let x = F::from_bits(F::Int::ONE); - let y = F::from_bits(F::Int::ONE); - let z = F::ZERO; - - let fma = |x, y, z| fma_round(x, y, z, Round::Nearest).val; - - // 754-2020 says "When the exact result of (a × b) + c is non-zero yet the result of - // fusedMultiplyAdd is zero because of rounding, the zero result takes the sign of the - // exact result" - assert_biteq!(fma(x, y, z), F::ZERO); - assert_biteq!(fma(x, -y, z), F::NEG_ZERO); - assert_biteq!(fma(-x, y, z), F::NEG_ZERO); - assert_biteq!(fma(-x, -y, z), F::ZERO); - } - - #[test] - fn spec_test_f32() { - spec_test::<f32>(); - } - - #[test] - fn spec_test_f64() { - spec_test::<f64>(); - - let expect_underflow = [ - ( - hf64!("0x1.0p-1070"), - hf64!("0x1.0p-1070"), - hf64!("0x1.ffffffffffffp-1023"), - hf64!("0x0.ffffffffffff8p-1022"), - ), - ( - // FIXME: we raise underflow but this should only be inexact (based on C and - // `rustc_apfloat`). - hf64!("0x1.0p-1070"), - hf64!("0x1.0p-1070"), - hf64!("-0x1.0p-1022"), - hf64!("-0x1.0p-1022"), - ), - ]; - - for (x, y, z, res) in expect_underflow { - let FpResult { val, status } = fma_round(x, y, z, Round::Nearest); - assert_biteq!(val, res); - assert_eq!(status, Status::UNDERFLOW); - } - } - - #[test] - #[cfg(f128_enabled)] - fn spec_test_f128() { - spec_test::<f128>(); - } - - #[test] - fn fma_segfault() { - // These two inputs cause fma to segfault on release due to overflow: - assert_eq!( - fma( - -0.0000000000000002220446049250313, - -0.0000000000000002220446049250313, - -0.0000000000000002220446049250313 - ), - -0.00000000000000022204460492503126, - ); - - let result = fma(-0.992, -0.992, -0.992); - //force rounding to storage format on x87 to prevent superious errors. - #[cfg(all(target_arch = "x86", not(target_feature = "sse2")))] - let result = force_eval!(result); - assert_eq!(result, -0.007936000000000007,); - } - - #[test] - fn fma_sbb() { - assert_eq!( - fma(-(1.0 - f64::EPSILON), f64::MIN, f64::MIN), - -3991680619069439e277 - ); - } - - #[test] - fn fma_underflow() { - assert_eq!( - fma(1.1102230246251565e-16, -9.812526705433188e-305, 1.0894e-320), - 0.0, - ); - } -} |