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Add fmod implementation for nolibc.

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This commit is contained in:
Christoffer Lerno
2024-08-29 20:04:59 +02:00
parent 3d83316b03
commit bc267e22bd
2 changed files with 79 additions and 0 deletions
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78
lib/std/math/math_nolibc/__fmod.c3 Normal file
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module std::math::nolibc @if(env::NO_LIBC);
union DoubleInternal
{
double f;
ulong i;
}
// Based on the musl implementation
fn double fmod(double x, double y) @extern("fmod") @weak @nostrip
{
DoubleInternal ux = { .f = x };
DoubleInternal uy = { .f = y };
int ex = (int)((ux.i >> 52) & 0x7ff);
int ey = (int)((uy.i >> 52) & 0x7ff);
int sx = (int)(ux.i >> 63);
ulong uxi = ux.i;
if (uy.i << 1 == 0 || math::is_nan(y) || ex == 0x7ff) return (x * y)/(x * y);
if (uxi << 1 <= uy.i << 1)
{
if (uxi << 1 == uy.i << 1) return 0 * x;
return x;
}
if (!ex)
{
for (ulong i = uxi << 12; i >> 63 == 0; ex--, i <<= 1);
uxi <<= -ex + 1;
}
else
{
uxi &= -1UL >> 12;
uxi |= 1UL << 52;
}
if (!ey)
{
for (ulong i = uy.i << 12; i >> 63 == 0; ey--, i <<= 1);
uy.i <<= -ey + 1;
}
else
{
uy.i &= -1UL >> 12;
uy.i |= 1UL << 52;
}
/* x mod y */
for (; ex > ey; ex--)
{
ulong i = uxi - uy.i;
if (i >> 63 == 0)
{
if (i == 0) return 0 * x;
uxi = i;
}
uxi <<= 1;
}
ulong i = uxi - uy.i;
if (i >> 63 == 0)
{
if (i == 0) return 0*x;
uxi = i;
}
for (; uxi>>52 == 0; uxi <<= 1, ex--);
/* scale result */
if (ex > 0)
{
uxi -= 1UL << 52;
uxi |= (ulong)ex << 52;
}
else
{
uxi >>= -ex + 1;
}
uxi |= (ulong)sx << 63;
ux.i = uxi;
return ux.f;
}