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(hx>0) return 0.0; /* acos(1) = 0 */ 43 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 44 } else if(ix>0x3f800000) { /* |x| >= 1 */ 45 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 46 } 47 if(ix<0x3f000000) { /* |x| < 0.5 */ 48 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ 49 z = x*x; 50 p = z*(pS0+z*(pS1+z*pS2)); 51 q = one+z*qS1; 52 r = p/q; 53 return pio2_hi - (x - (pio2_lo-x*r)); 54 } else if (hx<0) { /* x < -0.5 */ 55 z = (one+x)*(float)0.5; 56 p = z*(pS0+z*(pS1+z*pS2)); 57 q = one+z*qS1; 58 s = __ieee754_sqrtf(z); 59 r = p/q; 60 w = r*s-pio2_lo; 61 return pi - (float)2.0*(s+w); 62 } else { /* x > 0.5 */ 63 int32_t idf; 64 z = (one-x)*(float)0.5; 65 s = __ieee754_sqrtf(z); 66 df = s; 67 GET_FLOAT_WORD(idf,df); 68 SET_FLOAT_WORD(df,idf&0xfffff000); 69 c = (z-df*df)/(s+df); 70 p = z*(pS0+z*(pS1+z*pS2)); 71 q = one+z*qS1; 72 r = p/q; 73 w = r*s+c; 74 return (float)2.0*(df+w); 75 } 76 } 77