| Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 1 | /*- |
| Elliott Hughes | c1e46b6 | 2023-07-19 14:06:31 -0700 | [diff] [blame] | 2 | * SPDX-License-Identifier: BSD-2-Clause |
| Elliott Hughes | 8da8ca4 | 2018-05-08 13:35:33 -0700 | [diff] [blame] | 3 | * |
| Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 4 | * Copyright (c) 2007 Steven G. Kargl |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * Redistribution and use in source and binary forms, with or without |
| 8 | * modification, are permitted provided that the following conditions |
| 9 | * are met: |
| 10 | * 1. Redistributions of source code must retain the above copyright |
| 11 | * notice unmodified, this list of conditions, and the following |
| 12 | * disclaimer. |
| 13 | * 2. Redistributions in binary form must reproduce the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer in the |
| 15 | * documentation and/or other materials provided with the distribution. |
| 16 | * |
| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | */ |
| 28 | |
| Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 29 | /* |
| 30 | * Limited testing on pseudorandom numbers drawn within [0:4e8] shows |
| 31 | * an accuracy of <= 1.5 ULP where 247024 values of x out of 40 million |
| 32 | * possibles resulted in tan(x) that exceeded 0.5 ULP (ie., 0.6%). |
| 33 | */ |
| 34 | |
| 35 | #include <float.h> |
| 36 | #ifdef __i386__ |
| 37 | #include <ieeefp.h> |
| 38 | #endif |
| 39 | |
| 40 | #include "math.h" |
| 41 | #include "math_private.h" |
| 42 | #if LDBL_MANT_DIG == 64 |
| 43 | #include "../ld80/e_rem_pio2l.h" |
| 44 | #elif LDBL_MANT_DIG == 113 |
| 45 | #include "../ld128/e_rem_pio2l.h" |
| 46 | #else |
| 47 | #error "Unsupported long double format" |
| 48 | #endif |
| 49 | |
| 50 | long double |
| 51 | tanl(long double x) |
| 52 | { |
| 53 | union IEEEl2bits z; |
| 54 | int e0, s; |
| 55 | long double y[2]; |
| 56 | long double hi, lo; |
| 57 | |
| 58 | z.e = x; |
| 59 | s = z.bits.sign; |
| 60 | z.bits.sign = 0; |
| 61 | |
| 62 | /* If x = +-0 or x is subnormal, then tan(x) = x. */ |
| 63 | if (z.bits.exp == 0) |
| 64 | return (x); |
| 65 | |
| 66 | /* If x = NaN or Inf, then tan(x) = NaN. */ |
| 67 | if (z.bits.exp == 32767) |
| 68 | return ((x - x) / (x - x)); |
| 69 | |
| 70 | ENTERI(); |
| 71 | |
| 72 | /* Optimize the case where x is already within range. */ |
| 73 | if (z.e < M_PI_4) { |
| 74 | hi = __kernel_tanl(z.e, 0, 0); |
| 75 | RETURNI(s ? -hi : hi); |
| 76 | } |
| 77 | |
| 78 | e0 = __ieee754_rem_pio2l(x, y); |
| 79 | hi = y[0]; |
| 80 | lo = y[1]; |
| 81 | |
| 82 | switch (e0 & 3) { |
| 83 | case 0: |
| 84 | case 2: |
| 85 | hi = __kernel_tanl(hi, lo, 0); |
| 86 | break; |
| 87 | case 1: |
| 88 | case 3: |
| 89 | hi = __kernel_tanl(hi, lo, 1); |
| 90 | break; |
| 91 | } |
| 92 | |
| 93 | RETURNI(hi); |
| 94 | } |