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 #include "math.h" 18 #include "math_private.h" 19 20 static const float 21 one = 1.0000000000e+00, /* 0x3F800000 */ 22 pi = 3.1415925026e+00, /* 0x40490fda */ 23 pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */ 24 static volatile float 25 pio2_lo = 7.5497894159e-08; /* 0x33a22168 */ 26 static const float 27 pS0 = 1.6666586697e-01, 28 pS1 = -4.2743422091e-02, 29 pS2 = -8.6563630030e-03, 30 qS1 = -7.0662963390e-01; 31 32 float 33 acosf(float x) 34 { 35 float z,p,q,r,w,s,c,df; 36 int32_t hx,ix; 37 GET_FLOAT_WORD(hx,x); 38 ix = hx&0x7fffffff; 39 if(ix>=0x3f800000) { /* |x| >= 1 */ 40 if(ix==0x3f800000) { /* |x| == 1 */ 41 if(hx>0) return 0.0; /* acos(1) = 0 */ 42 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 43 } 44 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 45 } 46 if(ix<0x3f000000) { /* |x| < 0.5 */ 47 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ 48 z = x*x; 49 p = z*(pS0+z*(pS1+z*pS2)); 50 q = one+z*qS1; 51 r = p/q; 52 return pio2_hi - (x - (pio2_lo-x*r)); 53 } else if (hx<0) { /* x < -0.5 */ 54 z = (one+x)*(float)0.5; 55 p = z*(pS0+z*(pS1+z*pS2)); 56 q = one+z*qS1; 57 s = sqrtf(z); 58 r = p/q; 59 w = r*s-pio2_lo; 60 return pi - (float)2.0*(s+w); 61 } else { /* x > 0.5 */ 62 int32_t idf; 63 z = (one-x)*(float)0.5; 64 s = sqrtf(z); 65 df = s; 66 GET_FLOAT_WORD(idf,df); 67 SET_FLOAT_WORD(df,idf&0xfffff000); 68 c = (z-df*df)/(s+df); 69 p = z*(pS0+z*(pS1+z*pS2)); 70 q = one+z*qS1; 71 r = p/q; 72 w = r*s+c; 73 return (float)2.0*(df+w); 74 } 75 } 76