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 "math.h" 17 #include "math_private.h" 18 19 static const float 20 one = 1.0000000000e+00, /* 0x3F800000 */ 21 pi = 3.1415925026e+00, /* 0x40490fda */ 22 pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */ 23 static volatile float 24 pio2_lo = 7.5497894159e-08; /* 0x33a22168 */ 25 static const float 26 pS0 = 1.6666586697e-01, 27 pS1 = -4.2743422091e-02, 28 pS2 = -8.6563630030e-03, 29 qS1 = -7.0662963390e-01; 30 31 float 32 acosf(float x) 33 { 34 float z,p,q,r,w,s,c,df; 35 int32_t hx,ix; 36 GET_FLOAT_WORD(hx,x); 37 ix = hx&0x7fffffff; 38 if(ix>=0x3f800000) { /* |x| >= 1 */ 39 if(ix==0x3f800000) { /* |x| == 1 */ 40 if(hx>0) return 0.0; /* acos(1) = 0 */ 41 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 42 } 43 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 44 } 45 if(ix<0x3f000000) { /* |x| < 0.5 */ 46 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ 47 z = x*x; 48 p = z*(pS0+z*(pS1+z*pS2)); 49 q = one+z*qS1; 50 r = p/q; 51 return pio2_hi - (x - (pio2_lo-x*r)); 52 } else if (hx<0) { /* x < -0.5 */ 53 z = (one+x)*(float)0.5; 54 p = z*(pS0+z*(pS1+z*pS2)); 55 q = one+z*qS1; 56 s = sqrtf(z); 57 r = p/q; 58 w = r*s-pio2_lo; 59 return pi - (float)2.0*(s+w); 60 } else { /* x > 0.5 */ 61 int32_t idf; 62 z = (one-x)*(float)0.5; 63 s = sqrtf(z); 64 df = s; 65 GET_FLOAT_WORD(idf,df); 66 SET_FLOAT_WORD(df,idf&0xfffff000); 67 c = (z-df*df)/(s+df); 68 p = z*(pS0+z*(pS1+z*pS2)); 69 q = one+z*qS1; 70 r = p/q; 71 w = r*s+c; 72 return (float)2.0*(df+w); 73 } 74 } 75