88 lines
2.5 KiB
C
88 lines
2.5 KiB
C
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/* Used by sinf, cosf and sincosf functions.
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Copyright (C) 2018-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* The constants and polynomials for sine and cosine. */
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typedef struct
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{
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double sign[4]; /* Sign of sine in quadrants 0..3. */
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double hpi_inv; /* 2 / PI ( * 2^24 if !TOINT_INTRINSICS). */
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double hpi; /* PI / 2. */
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double c0, c1, c2, c3, c4; /* Cosine polynomial. */
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double s1, s2, s3; /* Sine polynomial. */
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} sincos_t;
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/* Compute the sine and cosine of inputs X and X2 (X squared), using the
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polynomial P and store the results in SINP and COSP. N is the quadrant,
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if odd the cosine and sine polynomials are swapped. */
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static inline void
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sincosf_poly (double x, double x2, const sincos_t *p, int n, float *sinp,
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float *cosp)
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{
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double x3, x4, x5, x6, s, c, c1, c2, s1;
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x4 = x2 * x2;
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x3 = x2 * x;
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c2 = p->c3 + x2 * p->c4;
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s1 = p->s2 + x2 * p->s3;
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/* Swap sin/cos result based on quadrant. */
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float *tmp = (n & 1 ? cosp : sinp);
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cosp = (n & 1 ? sinp : cosp);
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sinp = tmp;
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c1 = p->c0 + x2 * p->c1;
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x5 = x3 * x2;
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x6 = x4 * x2;
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s = x + x3 * p->s1;
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c = c1 + x4 * p->c2;
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*sinp = s + x5 * s1;
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*cosp = c + x6 * c2;
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}
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/* Return the sine of inputs X and X2 (X squared) using the polynomial P.
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N is the quadrant, and if odd the cosine polynomial is used. */
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static inline float
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sinf_poly (double x, double x2, const sincos_t *p, int n)
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{
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double x3, x4, x6, x7, s, c, c1, c2, s1;
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if ((n & 1) == 0)
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{
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x3 = x * x2;
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s1 = p->s2 + x2 * p->s3;
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x7 = x3 * x2;
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s = x + x3 * p->s1;
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return s + x7 * s1;
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}
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else
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{
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x4 = x2 * x2;
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c2 = p->c3 + x2 * p->c4;
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c1 = p->c0 + x2 * p->c1;
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x6 = x4 * x2;
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c = c1 + x4 * p->c2;
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return c + x6 * c2;
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}
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}
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