vendor/compiler_builtins/libm/src/math/sincos.rs

   1 /* origin: FreeBSD /usr/src/lib/msun/src/s_sin.c */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 use super::{get_high_word, k_cos, k_sin, rem_pio2};
  14
  15 pub fn sincos(x: f64) -> (f64, f64) {
  16     let s: f64;
  17     let c: f64;
  18     let mut ix: u32;
  19
  20     ix = get_high_word(x);
  21     ix &= 0x7fffffff;
  22
  23     /* |x| ~< pi/4 */
  24     if ix <= 0x3fe921fb {
  25         /* if |x| < 2**-27 * sqrt(2) */
  26         if ix < 0x3e46a09e {
  27             /* raise inexact if x!=0 and underflow if subnormal */
  28             let x1p120 = f64::from_bits(0x4770000000000000); // 0x1p120 == 2^120
  29             if ix < 0x00100000 {
  30                 force_eval!(x / x1p120);
  31             } else {
  32                 force_eval!(x + x1p120);
  33             }
  34             return (x, 1.0);
  35         }
  36         return (k_sin(x, 0.0, 0), k_cos(x, 0.0));
  37     }
  38
  39     /* sincos(Inf or NaN) is NaN */
  40     if ix >= 0x7ff00000 {
  41         let rv = x - x;
  42         return (rv, rv);
  43     }
  44
  45     /* argument reduction needed */
  46     let (n, y0, y1) = rem_pio2(x);
  47     s = k_sin(y0, y1, 1);
  48     c = k_cos(y0, y1);
  49     match n & 3 {
  50         0 => (s, c),
  51         1 => (c, -s),
  52         2 => (-s, -c),
  53         3 => (-c, s),
  54         #[cfg(feature = "checked")]
  55         _ => unreachable!(),
  56         #[cfg(not(feature = "checked"))]
  57         _ => (0.0, 1.0),
  58     }
  59 }