cosmopolitan/libc/tinymath/cosf.c

/*-*- mode:c;indent-tabs-mode:t;c-basic-offset:8;tab-width:8;coding:utf-8   -*-│
│ vi: set noet ft=c ts=8 sw=8 fenc=utf-8                                   :vi │
╚──────────────────────────────────────────────────────────────────────────────╝
│                                                                              │
│  Musl Libc                                                                   │
│  Copyright © 2005-2014 Rich Felker, et al.                                   │
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│  Permission is hereby granted, free of charge, to any person obtaining       │
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│  "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:                                                   │
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│  The above copyright notice and this permission notice shall be              │
│  included in all copies or substantial portions of the Software.             │
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│  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,             │
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│  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY        │
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╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/math.h"
#include "libc/tinymath/complex.internal.h"
#include "libc/tinymath/feval.internal.h"
#include "libc/tinymath/kernel.internal.h"

asm(".ident\t\"\\n\\n\
fdlibm (fdlibm license)\\n\
Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.\"");
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 */

/* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */
/*
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 * Optimized by Bruce D. Evans.
 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

/* Small multiples of pi/2 rounded to double precision. */
static const double
c1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
c2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
c3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
c4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */

/**
 * Returns cosine of 𝑥.
 * @note should take about 5ns
 */
float cosf(float x)
{
	double y;
	uint32_t ix;
	unsigned n, sign;

	GET_FLOAT_WORD(ix, x);
	sign = ix >> 31;
	ix &= 0x7fffffff;

	if (ix <= 0x3f490fda) {  /* |x| ~<= pi/4 */
		if (ix < 0x39800000) {  /* |x| < 2**-12 */
			/* raise inexact if x != 0 */
			FORCE_EVAL(x + 0x1p120f);
			return 1.0f;
		}
		return __cosdf(x);
	}
	if (ix <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
		if (ix > 0x4016cbe3)  /* |x|  ~> 3*pi/4 */
			return -__cosdf(sign ? x+c2pio2 : x-c2pio2);
		else {
			if (sign)
				return __sindf(x + c1pio2);
			else
				return __sindf(c1pio2 - x);
		}
	}
	if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
		if (ix > 0x40afeddf)  /* |x| ~> 7*pi/4 */
			return __cosdf(sign ? x+c4pio2 : x-c4pio2);
		else {
			if (sign)
				return __sindf(-x - c3pio2);
			else
				return __sindf(x - c3pio2);
		}
	}

	/* cos(Inf or NaN) is NaN */
	if (ix >= 0x7f800000)
		return x-x;

	/* general argument reduction needed */
	n = __rem_pio2f(x,&y);
	switch (n&3) {
	case 0: return  __cosdf(y);
	case 1: return  __sindf(-y);
	case 2: return -__cosdf(y);
	default:
		return  __sindf(y);
	}
}