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/* Used by sinf, cosf and sincosf functions.
Copyright (C) 2018-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* The constants and polynomials for sine and cosine. */
typedef struct
{
double sign[4]; /* Sign of sine in quadrants 0..3. */
double hpi_inv; /* 2 / PI ( * 2^24 if !TOINT_INTRINSICS). */
double hpi; /* PI / 2. */
double c0, c1, c2, c3, c4; /* Cosine polynomial. */
double s1, s2, s3; /* Sine polynomial. */
} sincos_t;
/* Compute the sine and cosine of inputs X and X2 (X squared), using the
polynomial P and store the results in SINP and COSP. N is the quadrant,
if odd the cosine and sine polynomials are swapped. */
static inline void
sincosf_poly (double x, double x2, const sincos_t *p, int n, float *sinp,
float *cosp)
{
double x3, x4, x5, x6, s, c, c1, c2, s1;
x4 = x2 * x2;
x3 = x2 * x;
c2 = p->c3 + x2 * p->c4;
s1 = p->s2 + x2 * p->s3;
/* Swap sin/cos result based on quadrant. */
float *tmp = (n & 1 ? cosp : sinp);
cosp = (n & 1 ? sinp : cosp);
sinp = tmp;
c1 = p->c0 + x2 * p->c1;
x5 = x3 * x2;
x6 = x4 * x2;
s = x + x3 * p->s1;
c = c1 + x4 * p->c2;
*sinp = s + x5 * s1;
*cosp = c + x6 * c2;
}
/* Return the sine of inputs X and X2 (X squared) using the polynomial P.
N is the quadrant, and if odd the cosine polynomial is used. */
static inline float
sinf_poly (double x, double x2, const sincos_t *p, int n)
{
double x3, x4, x6, x7, s, c, c1, c2, s1;
if ((n & 1) == 0)
{
x3 = x * x2;
s1 = p->s2 + x2 * p->s3;
x7 = x3 * x2;
s = x + x3 * p->s1;
return s + x7 * s1;
}
else
{
x4 = x2 * x2;
c2 = p->c3 + x2 * p->c4;
c1 = p->c0 + x2 * p->c1;
x6 = x4 * x2;
c = c1 + x4 * p->c2;
return c + x6 * c2;
}
}
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