| Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 1 | /* e_acosf.c -- float version of e_acos.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
| 3 | */ |
| 4 | |
| 5 | /* |
| 6 | * ==================================================== |
| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 8 | * |
| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
| 10 | * Permission to use, copy, modify, and distribute this |
| 11 | * software is freely granted, provided that this notice |
| 12 | * is preserved. |
| 13 | * ==================================================== |
| 14 | */ |
| 15 | |
| 16 | #include <sys/cdefs.h> |
| 17 | __FBSDID("$FreeBSD$"); |
| 18 | |
| 19 | #include "math.h" |
| 20 | #include "math_private.h" |
| 21 | |
| 22 | static const float |
| 23 | one = 1.0000000000e+00, /* 0x3F800000 */ |
| 24 | pi = 3.1415925026e+00, /* 0x40490fda */ |
| 25 | pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */ |
| 26 | static volatile float |
| 27 | pio2_lo = 7.5497894159e-08; /* 0x33a22168 */ |
| 28 | static const float |
| 29 | pS0 = 1.6666586697e-01, |
| 30 | pS1 = -4.2743422091e-02, |
| 31 | pS2 = -8.6563630030e-03, |
| 32 | qS1 = -7.0662963390e-01; |
| 33 | |
| 34 | float |
| 35 | __ieee754_acosf(float x) |
| 36 | { |
| 37 | float z,p,q,r,w,s,c,df; |
| 38 | int32_t hx,ix; |
| 39 | GET_FLOAT_WORD(hx,x); |
| 40 | ix = hx&0x7fffffff; |
| 41 | if(ix>=0x3f800000) { /* |x| >= 1 */ |
| 42 | if(ix==0x3f800000) { /* |x| == 1 */ |
| 43 | if(hx>0) return 0.0; /* acos(1) = 0 */ |
| 44 | else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ |
| 45 | } |
| 46 | return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
| 47 | } |
| 48 | if(ix<0x3f000000) { /* |x| < 0.5 */ |
| 49 | if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ |
| 50 | z = x*x; |
| 51 | p = z*(pS0+z*(pS1+z*pS2)); |
| 52 | q = one+z*qS1; |
| 53 | r = p/q; |
| 54 | return pio2_hi - (x - (pio2_lo-x*r)); |
| 55 | } else if (hx<0) { /* x < -0.5 */ |
| 56 | z = (one+x)*(float)0.5; |
| 57 | p = z*(pS0+z*(pS1+z*pS2)); |
| 58 | q = one+z*qS1; |
| 59 | s = sqrtf(z); |
| 60 | r = p/q; |
| 61 | w = r*s-pio2_lo; |
| 62 | return pi - (float)2.0*(s+w); |
| 63 | } else { /* x > 0.5 */ |
| 64 | int32_t idf; |
| 65 | z = (one-x)*(float)0.5; |
| 66 | s = sqrtf(z); |
| 67 | df = s; |
| 68 | GET_FLOAT_WORD(idf,df); |
| 69 | SET_FLOAT_WORD(df,idf&0xfffff000); |
| 70 | c = (z-df*df)/(s+df); |
| 71 | p = z*(pS0+z*(pS1+z*pS2)); |
| 72 | q = one+z*qS1; |
| 73 | r = p/q; |
| 74 | w = r*s+c; |
| 75 | return (float)2.0*(df+w); |
| 76 | } |
| 77 | } |