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Merge pull request rust-lang/libm#252 from jethrogb/issue-242

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Fix substract with borrow in FMA
This commit is contained in:
Lokathor 2021-06-24 20:23:34 -06:00 • committed by GitHub
commit 777b8fa251
2 changed files with 14 additions and 6 deletions
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16
library/compiler-builtins/libm/src/math/fma.rs
View file

@ -122,9 +122,9 @@ pub fn fma(x: f64, y: f64, z: f64) -> f64 {
rhi += zhi + (rlo < zlo) as u64;
} else {
/* r -= z */
let t = rlo;
rlo = rlo.wrapping_sub(zlo);
rhi = rhi.wrapping_sub(zhi.wrapping_sub((t < rlo) as u64));
let (res, borrow) = rlo.overflowing_sub(zlo);
rlo = res;
rhi = rhi.wrapping_sub(zhi.wrapping_add(borrow as u64));
if (rhi >> 63) != 0 {
rlo = (-(rlo as i64)) as u64;
rhi = (-(rhi as i64)) as u64 - (rlo != 0) as u64;
@ -218,6 +218,14 @@ mod tests {
-0.00000000000000022204460492503126,
);
assert_eq!(fma(-0.992, -0.992, -0.992), -0.00793599999988632,);
assert_eq!(fma(-0.992, -0.992, -0.992), -0.007936000000000007,);
}
#[test]
fn fma_sbb() {
assert_eq!(
fma(-(1.0 - f64::EPSILON), f64::MIN, f64::MIN),
-3991680619069439e277
);
}
}

4
library/compiler-builtins/libm/src/math/pow.rs
View file

@ -604,7 +604,7 @@ mod tests {
// Factoring -1 out:
// (negative anything ^ integer should be (-1 ^ integer) * (positive anything ^ integer))
&[POS_ZERO, NEG_ZERO, POS_ONE, NEG_ONE, POS_EVENS, NEG_EVENS]
(&[POS_ZERO, NEG_ZERO, POS_ONE, NEG_ONE, POS_EVENS, NEG_EVENS])
.iter()
.for_each(|int_set| {
int_set.iter().for_each(|int| {
@ -616,7 +616,7 @@ mod tests {
// Negative base (imaginary results):
// (-anything except 0 and Infinity ^ non-integer should be NAN)
&NEG[1..(NEG.len() - 1)].iter().for_each(|set| {
(&NEG[1..(NEG.len() - 1)]).iter().for_each(|set| {
set.iter().for_each(|val| {
test_sets(&ALL[3..7], &|v: f64| pow(*val, v), &|_| NAN);
})