/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│vi: set et ft=c ts=8 tw=8 fenc=utf-8                                       :vi│
╚──────────────────────────────────────────────────────────────────────────────╝
│                                                                              │
│  Musl Libc                                                                   │
│  Copyright © 2005-2014 Rich Felker, et al.                                   │
│                                                                              │
│  Permission is hereby granted, free of charge, to any person obtaining       │
│  a copy of this software and associated documentation files (the             │
│  "Software"), to deal in the Software without restriction, including         │
│  without limitation the rights to use, copy, modify, merge, publish,         │
│  distribute, sublicense, and/or sell copies of the Software, and to          │
│  permit persons to whom the Software is furnished to do so, subject to       │
│  the following conditions:                                                   │
│                                                                              │
│  The above copyright notice and this permission notice shall be              │
│  included in all copies or substantial portions of the Software.             │
│                                                                              │
│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
│  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF          │
│  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.      │
│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
│  CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,        │
│  TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE           │
│  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                      │
│                                                                              │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "third_party/libcxx/math.h"

asm(".ident\t\"\\n\\n\
Musl libc (MIT License)\\n\
Copyright 2005-2014 Rich Felker, et. al.\"");
asm(".include \"libc/disclaimer.inc\"");
// clang-format off

/**
 * Does (𝑥 rem 𝑦) w/ round()-style rounding.
 * @return remainder ∈ (-|𝑦|,|𝑦|) in %xmm0
 * @define 𝑥-trunc(𝑥/𝑦)*𝑦
 */
double fmod(double x, double y)
{
	union {double f; uint64_t i;} ux = {x}, uy = {y};
	int ex = ux.i>>52 & 0x7ff;
	int ey = uy.i>>52 & 0x7ff;
	int sx = ux.i>>63;
	uint64_t i;

	/* in the followings uxi should be ux.i, but then gcc wrongly adds */
	/* float load/store to inner loops ruining performance and code size */
	uint64_t uxi = ux.i;

	if (uy.i<<1 == 0 || isnan(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;
	}

	/* normalize x and y */
	if (!ex) {
		for (i = uxi<<12; i>>63 == 0; ex--, i <<= 1);
		uxi <<= -ex + 1;
	} else {
		uxi &= -1ULL >> 12;
		uxi |= 1ULL << 52;
	}
	if (!ey) {
		for (i = uy.i<<12; i>>63 == 0; ey--, i <<= 1);
		uy.i <<= -ey + 1;
	} else {
		uy.i &= -1ULL >> 12;
		uy.i |= 1ULL << 52;
	}

	/* x mod y */
	for (; ex > ey; ex--) {
		i = uxi - uy.i;
		if (i >> 63 == 0) {
			if (i == 0)
				return 0*x;
			uxi = i;
		}
		uxi <<= 1;
	}
	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 -= 1ULL << 52;
		uxi |= (uint64_t)ex << 52;
	} else {
		uxi >>= -ex + 1;
	}
	uxi |= (uint64_t)sx << 63;
	ux.i = uxi;
	return ux.f;
}