| /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */ |
| /* |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| * Optimized by Bruce D. Evans. |
| */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| use super::{k_cosf, k_sinf, rem_pio2f}; |
| |
| use core::f64::consts::FRAC_PI_2; |
| |
| /* Small multiples of pi/2 rounded to double precision. */ |
| const C1_PIO2: f64 = 1. * FRAC_PI_2; /* 0x3FF921FB, 0x54442D18 */ |
| const C2_PIO2: f64 = 2. * FRAC_PI_2; /* 0x400921FB, 0x54442D18 */ |
| const C3_PIO2: f64 = 3. * FRAC_PI_2; /* 0x4012D97C, 0x7F3321D2 */ |
| const C4_PIO2: f64 = 4. * FRAC_PI_2; /* 0x401921FB, 0x54442D18 */ |
| |
| #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] |
| pub fn cosf(x: f32) -> f32 { |
| let x64 = x as f64; |
| |
| let x1p120 = f32::from_bits(0x7b800000); // 0x1p120f === 2 ^ 120 |
| |
| let mut ix = x.to_bits(); |
| let sign = (ix >> 31) != 0; |
| ix &= 0x7fffffff; |
| |
| if ix <= 0x3f490fda { |
| /* |x| ~<= pi/4 */ |
| if ix < 0x39800000 { |
| /* |x| < 2**-12 */ |
| /* raise inexact if x != 0 */ |
| force_eval!(x + x1p120); |
| return 1.; |
| } |
| return k_cosf(x64); |
| } |
| if ix <= 0x407b53d1 { |
| /* |x| ~<= 5*pi/4 */ |
| if ix > 0x4016cbe3 { |
| /* |x| ~> 3*pi/4 */ |
| return -k_cosf(if sign { x64 + C2_PIO2 } else { x64 - C2_PIO2 }); |
| } else if sign { |
| return k_sinf(x64 + C1_PIO2); |
| } else { |
| return k_sinf(C1_PIO2 - x64); |
| } |
| } |
| if ix <= 0x40e231d5 { |
| /* |x| ~<= 9*pi/4 */ |
| if ix > 0x40afeddf { |
| /* |x| ~> 7*pi/4 */ |
| return k_cosf(if sign { x64 + C4_PIO2 } else { x64 - C4_PIO2 }); |
| } else if sign { |
| return k_sinf(-x64 - C3_PIO2); |
| } else { |
| return k_sinf(x64 - C3_PIO2); |
| } |
| } |
| |
| /* cos(Inf or NaN) is NaN */ |
| if ix >= 0x7f800000 { |
| return x - x; |
| } |
| |
| /* general argument reduction needed */ |
| let (n, y) = rem_pio2f(x); |
| match n & 3 { |
| 0 => k_cosf(y), |
| 1 => k_sinf(-y), |
| 2 => -k_cosf(y), |
| _ => k_sinf(y), |
| } |
| } |
