cosmopolitan/libc/tinymath/floor.c

/*-*- 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 "libc/math.h"
#include "libc/runtime/fenv.h"
#include "libc/tinymath/internal.h"
#include "third_party/intel/smmintrin.internal.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

#if FLT_EVAL_METHOD==0 || FLT_EVAL_METHOD==1
#define EPS DBL_EPSILON
#elif FLT_EVAL_METHOD==2
#define EPS LDBL_EPSILON
#endif
static const double_t toint = 1/EPS;

/**
 * Returns largest integral value not greater than 𝑥.
 */
double floor(double x)
{
#ifdef __aarch64__

	asm("frintm\t%d0,%d1" : "=w"(x) : "w"(x));
	return x;

#elif defined(__powerpc64__) && defined(_ARCH_PWR5X)

	asm("frim\t%0,%1" : "=d"(x) : "d"(x));
	return x;

#elif defined(__s390x__) && (defined(__HTM__) || __ARCH__ >= 9)

	asm("fidbra\t%0,7,%1,4" : "=f"(x) : "f"(x));
	return x;

#elif defined(__x86_64__) && defined(__SSE4_1__)

	asm("roundsd\t%2,%1,%0"
	    : "=x"(x)
	    : "x"(x), "i"(_MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC));
	return x;

#else

	union {double f; uint64_t i;} u = {x};
	int e = u.i >> 52 & 0x7ff;
	double_t y;

	if (e >= 0x3ff+52 || x == 0)
		return x;
	/* y = int(x) - x, where int(x) is an integer neighbor of x */
	if (u.i >> 63)
		y = x - toint + toint - x;
	else
		y = x + toint - toint - x;
	/* special case because of non-nearest rounding modes */
	if (e <= 0x3ff-1) {
		FORCE_EVAL(y);
		return u.i >> 63 ? -1 : 0;
	}
	if (y > 0)
		return x + y - 1;
	return x + y;

#endif /* __aarch64__ */
}