| /* origin: FreeBSD /usr/src/lib/msun/src/e_acosf.c */ |
| /* |
| * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| */ |
| /* |
| * ==================================================== |
| * 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. |
| * ==================================================== |
| */ |
| |
| #include "libm.h" |
| |
| static const float pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ |
| pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ |
| pS0 = 1.6666586697e-01, pS1 = -4.2743422091e-02, pS2 = -8.6563630030e-03, |
| qS1 = -7.0662963390e-01; |
| |
| static float R(float z) { |
| float_t p, q; |
| p = z * (pS0 + z * (pS1 + z * pS2)); |
| q = 1.0f + z * qS1; |
| return p / q; |
| } |
| |
| float acosf(float x) { |
| float z, w, s, c, df; |
| uint32_t hx, ix; |
| |
| GET_FLOAT_WORD(hx, x); |
| ix = hx & 0x7fffffff; |
| /* |x| >= 1 or nan */ |
| if (ix >= 0x3f800000) { |
| if (ix == 0x3f800000) { |
| if (hx >> 31) |
| return 2 * pio2_hi + 0x1p-120f; |
| return 0; |
| } |
| return 0 / (x - x); |
| } |
| /* |x| < 0.5 */ |
| if (ix < 0x3f000000) { |
| if (ix <= 0x32800000) /* |x| < 2**-26 */ |
| return pio2_hi + 0x1p-120f; |
| return pio2_hi - (x - (pio2_lo - x * R(x * x))); |
| } |
| /* x < -0.5 */ |
| if (hx >> 31) { |
| z = (1 + x) * 0.5f; |
| s = sqrtf(z); |
| w = R(z) * s - pio2_lo; |
| return 2 * (pio2_hi - (s + w)); |
| } |
| /* x > 0.5 */ |
| z = (1 - x) * 0.5f; |
| s = sqrtf(z); |
| GET_FLOAT_WORD(hx, s); |
| SET_FLOAT_WORD(df, hx & 0xfffff000); |
| c = (z - df * df) / (s + df); |
| w = R(z) * s + c; |
| return 2 * (df + w); |
| } |
