diff options
Diffstat (limited to 'vendor/libm/src/math/fmaf.rs')
| -rw-r--r-- | vendor/libm/src/math/fmaf.rs | 36 |
1 files changed, 23 insertions, 13 deletions
diff --git a/vendor/libm/src/math/fmaf.rs b/vendor/libm/src/math/fmaf.rs index e77e0fa4a..2848f2aee 100644 --- a/vendor/libm/src/math/fmaf.rs +++ b/vendor/libm/src/math/fmaf.rs @@ -29,8 +29,7 @@ use core::f32; use core::ptr::read_volatile; use super::fenv::{ - feclearexcept, fegetround, feraiseexcept, fesetround, fetestexcept, FE_INEXACT, FE_TONEAREST, - FE_TOWARDZERO, FE_UNDERFLOW, + feclearexcept, fegetround, feraiseexcept, fetestexcept, FE_INEXACT, FE_TONEAREST, FE_UNDERFLOW, }; /* @@ -46,7 +45,6 @@ use super::fenv::{ /// Computes `(x*y)+z`, rounded as one ternary operation: /// Computes the value (as if) to infinite precision and rounds once to the result format, /// according to the rounding mode characterized by the value of FLT_ROUNDS. -#[inline] #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] pub fn fmaf(x: f32, y: f32, mut z: f32) -> f32 { let xy: f64; @@ -92,16 +90,28 @@ pub fn fmaf(x: f32, y: f32, mut z: f32) -> f32 { * If result is inexact, and exactly halfway between two float values, * we need to adjust the low-order bit in the direction of the error. */ - fesetround(FE_TOWARDZERO); - // prevent `vxy + z` from being CSE'd with `xy + z` above - let vxy: f64 = unsafe { read_volatile(&xy) }; - let mut adjusted_result: f64 = vxy + z as f64; - fesetround(FE_TONEAREST); - if result == adjusted_result { - ui = adjusted_result.to_bits(); + let neg = ui >> 63 != 0; + let err = if neg == (z as f64 > xy) { + xy - result + z as f64 + } else { + z as f64 - result + xy + }; + if neg == (err < 0.0) { ui += 1; - adjusted_result = f64::from_bits(ui); + } else { + ui -= 1; + } + f64::from_bits(ui) as f32 +} + +#[cfg(test)] +mod tests { + #[test] + fn issue_263() { + let a = f32::from_bits(1266679807); + let b = f32::from_bits(1300234242); + let c = f32::from_bits(1115553792); + let expected = f32::from_bits(1501560833); + assert_eq!(super::fmaf(a, b, c), expected); } - z = adjusted_result as f32; - z } |