[337] | 1 | /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */
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| 2 | /*
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| 3 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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| 4 | * Optimized by Bruce D. Evans.
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| 5 | */
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| 6 | /*
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| 7 | * ====================================================
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| 8 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 9 | *
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| 10 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 11 | * Permission to use, copy, modify, and distribute this
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| 12 | * software is freely granted, provided that this notice
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| 13 | * is preserved.
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| 14 | * ====================================================
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| 15 | */
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| 16 |
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| 17 | #include "libm.h"
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| 18 |
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| 19 | /* Small multiples of pi/2 rounded to double precision. */
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| 20 | static const double
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| 21 | c1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
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| 22 | c2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
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| 23 | c3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
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| 24 | c4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
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| 25 |
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| 26 | float cosf(float x)
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| 27 | {
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| 28 | double y;
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| 29 | uint32_t ix;
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| 30 | unsigned n, sign;
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| 31 |
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| 32 | GET_FLOAT_WORD(ix, x);
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| 33 | sign = ix >> 31;
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| 34 | ix &= 0x7fffffff;
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| 35 |
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| 36 | if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */
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| 37 | if (ix < 0x39800000) { /* |x| < 2**-12 */
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| 38 | /* raise inexact if x != 0 */
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| 39 | FORCE_EVAL(x + 0x1p120f);
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| 40 | return 1.0f;
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| 41 | }
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| 42 | return __cosdf(x);
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| 43 | }
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| 44 | if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
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| 45 | if (ix > 0x4016cbe3) /* |x| ~> 3*pi/4 */
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| 46 | return -__cosdf(sign ? x+c2pio2 : x-c2pio2);
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| 47 | else {
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| 48 | if (sign)
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| 49 | return __sindf(x + c1pio2);
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| 50 | else
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| 51 | return __sindf(c1pio2 - x);
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| 52 | }
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| 53 | }
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| 54 | if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
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| 55 | if (ix > 0x40afeddf) /* |x| ~> 7*pi/4 */
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| 56 | return __cosdf(sign ? x+c4pio2 : x-c4pio2);
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| 57 | else {
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| 58 | if (sign)
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| 59 | return __sindf(-x - c3pio2);
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| 60 | else
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| 61 | return __sindf(x - c3pio2);
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| 62 | }
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| 63 | }
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| 64 |
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| 65 | /* cos(Inf or NaN) is NaN */
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| 66 | if (ix >= 0x7f800000)
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| 67 | return x-x;
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| 68 |
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| 69 | /* general argument reduction needed */
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| 70 | n = __rem_pio2f(x,&y);
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| 71 | switch (n&3) {
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| 72 | case 0: return __cosdf(y);
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| 73 | case 1: return __sindf(-y);
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| 74 | case 2: return -__cosdf(y);
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| 75 | default:
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| 76 | return __sindf(y);
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| 77 | }
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| 78 | }
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