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#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn remquo(mut x: f64, mut y: f64) -> (f64, i32) {
let ux: u64 = x.to_bits();
let mut uy: u64 = y.to_bits();
let mut ex = ((ux >> 52) & 0x7ff) as i32;
let mut ey = ((uy >> 52) & 0x7ff) as i32;
let sx = (ux >> 63) != 0;
let sy = (uy >> 63) != 0;
let mut q: u32;
let mut i: u64;
let mut uxi: u64 = ux;
if (uy << 1) == 0 || y.is_nan() || ex == 0x7ff {
return ((x * y) / (x * y), 0);
}
if (ux << 1) == 0 {
return (x, 0);
}
/* normalize x and y */
if ex == 0 {
i = uxi << 12;
while (i >> 63) == 0 {
ex -= 1;
i <<= 1;
}
uxi <<= -ex + 1;
} else {
uxi &= (!0) >> 12;
uxi |= 1 << 52;
}
if ey == 0 {
i = uy << 12;
while (i >> 63) == 0 {
ey -= 1;
i <<= 1;
}
uy <<= -ey + 1;
} else {
uy &= (!0) >> 12;
uy |= 1 << 52;
}
q = 0;
if ex + 1 != ey {
if ex < ey {
return (x, 0);
}
/* x mod y */
while ex > ey {
i = uxi.wrapping_sub(uy);
if (i >> 63) == 0 {
uxi = i;
q += 1;
}
uxi <<= 1;
q <<= 1;
ex -= 1;
}
i = uxi.wrapping_sub(uy);
if (i >> 63) == 0 {
uxi = i;
q += 1;
}
if uxi == 0 {
ex = -60;
} else {
while (uxi >> 52) == 0 {
uxi <<= 1;
ex -= 1;
}
}
}
/* scale result and decide between |x| and |x|-|y| */
if ex > 0 {
uxi -= 1 << 52;
uxi |= (ex as u64) << 52;
} else {
uxi >>= -ex + 1;
}
x = f64::from_bits(uxi);
if sy {
y = -y;
}
if ex == ey || (ex + 1 == ey && (2.0 * x > y || (2.0 * x == y && (q % 2) != 0))) {
x -= y;
// TODO: this matches musl behavior, but it is incorrect
q = q.wrapping_add(1);
}
q &= 0x7fffffff;
let quo = if sx ^ sy { -(q as i32) } else { q as i32 };
if sx {
(-x, quo)
} else {
(x, quo)
}
}
#[cfg(test)]
mod tests {
use super::remquo;
#[test]
fn test_q_overflow() {
// 0xc000000000000001, 0x04c0000000000004
let _ = remquo(-2.0000000000000004, 8.406091369059082e-286);
}
}
|
