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BAN/LibC: Move ldexp, scalbn to libc

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They are now implemented with float decompostion to modify the exponent
bits directly
This commit is contained in:
Bananymous
2026-07-10 00:44:28 +03:00
parent f0e95ffe48
commit efb25e5666
2 changed files with 35 additions and 34 deletions
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30
BAN/include/BAN/Math.h
View File

@@ -309,36 +309,6 @@ namespace BAN::Math
return exp2<T>(y * log2<T>(x));
}
template<floating_point T>
inline constexpr T scalbn(T x, int n)
{
asm("fscale" : "+t"(x) : "u"(static_cast<T>(n)));
return x;
}
template<floating_point T>
inline constexpr T ldexp(T x, int y)
{
const bool exp_sign = y < 0;
if (exp_sign)
y = -y;
T exp = (T)1.0;
T mult = (T)2.0;
while (y)
{
if (y & 1)
exp *= mult;
mult *= mult;
y >>= 1;
}
if (exp_sign)
exp = (T)1.0 / exp;
return x * exp;
}
template<floating_point T>
inline constexpr T sqrt(T x)
{

39
userspace/libraries/LibC/math.cpp
View File

@@ -1,5 +1,6 @@
#include <BAN/Math.h>
#include <errno.h>
#include <math.h>
#include <stddef.h>
@@ -156,6 +157,36 @@ static T1 nextafter_impl(T1 x, T2 y)
return decompose.raw;
}
template<BAN::floating_point T>
static T ldexp_impl(T x, long e)
{
// scalb{,l}n
static_assert(FLT_RADIX == 2);
if (e == 0 || x == (T)0.0 || isnan(x) || !isfinite(x))
return x;
// TODO: handle subnormals
FloatDecompose<T> decompose(x);
if (e < 0 && decompose.bits.exponent < -e)
{
errno = ERANGE;
return BAN::Math::copysign((T)0.0, x);
}
if (e > 0 && decompose.bits.exponent > decompose.exponent_max - e)
{
errno = ERANGE;
return BAN::Math::copysign(BAN::numeric_limits<T>::infinity(), x);
}
decompose.bits.exponent += e;
return decompose.raw;
}
static long double tgamma_impl(long double x)
{
constexpr long double pi = BAN::numbers::pi_v<long double>;
@@ -199,7 +230,7 @@ static long double erf_impl(long double x)
{
long double sum = 0.0L;
for (size_t n = 0; n < 100; n++)
sum += x / (2.0L * n + 1.0L) * BAN::Math::ldexp(-x * x, n) / tgamma_impl(n + 1.0L);
sum += x / (2.0L * n + 1.0L) * ldexp_impl(-x * x, n) / tgamma_impl(n + 1.0L);
constexpr long double sqrt_pi = 1.77245385090551602729L;
return 2.0L / sqrt_pi * sum;
@@ -237,7 +268,7 @@ BAN_FUNC2_TYPE(frexp, int*)
BAN_FUNC2(hypot)
FUNC_EXPR1_RET(ilogb, int, BAN::Math::logb(a))
// j0, j1, jn
BAN_FUNC2_TYPE(ldexp, int)
FUNC_EXPR2_TYPE(ldexp, int, ldexp_impl(a, b));
FUNC_EXPR1(lgamma, BAN::Math::log(BAN::Math::abs(tgamma_impl(a))))
FUNC_EXPR1_RET(llrint, long long, BAN::Math::rint(a))
FUNC_EXPR1_RET(llround, long long, BAN::Math::round(a))
@@ -260,8 +291,8 @@ BAN_FUNC2(remainder)
// remquo
BAN_FUNC1(rint)
FUNC_EXPR1(round, ({ if (!isfinite(a)) return a; BAN::Math::round(a); }))
FUNC_EXPR2_TYPE(scalbln, long, BAN::Math::scalbn(a, b))
FUNC_EXPR2_TYPE(scalbn, int, BAN::Math::scalbn(a, b))
FUNC_EXPR2_TYPE(scalbln, long, ldexp_impl(a, b))
FUNC_EXPR2_TYPE(scalbn, int, ldexp_impl(a, b))
BAN_FUNC1(sin)
BAN_FUNC1(sinh)
BAN_FUNC1(sqrt)