e_acosf.cpp (2045B)
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 21 #include "math_private.h" 22 23 static const float 24 one = 1.0000000000e+00, /* 0x3F800000 */ 25 pi = 3.1415925026e+00, /* 0x40490fda */ 26 pio2_hi = 1.5707962513e+00; /* 0x3fc90fda */ 27 static volatile float 28 pio2_lo = 7.5497894159e-08; /* 0x33a22168 */ 29 static const float 30 pS0 = 1.6666586697e-01, 31 pS1 = -4.2743422091e-02, 32 pS2 = -8.6563630030e-03, 33 qS1 = -7.0662963390e-01; 34 35 float 36 __ieee754_acosf(float x) 37 { 38 float z,p,q,r,w,s,c,df; 39 int32_t hx,ix; 40 GET_FLOAT_WORD(hx,x); 41 ix = hx&0x7fffffff; 42 if(ix>=0x3f800000) { /* |x| >= 1 */ 43 if(ix==0x3f800000) { /* |x| == 1 */ 44 if(hx>0) return 0.0; /* acos(1) = 0 */ 45 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ 46 } 47 return (x-x)/(x-x); /* acos(|x|>1) is NaN */ 48 } 49 if(ix<0x3f000000) { /* |x| < 0.5 */ 50 if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/ 51 z = x*x; 52 p = z*(pS0+z*(pS1+z*pS2)); 53 q = one+z*qS1; 54 r = p/q; 55 return pio2_hi - (x - (pio2_lo-x*r)); 56 } else if (hx<0) { /* x < -0.5 */ 57 z = (one+x)*(float)0.5; 58 p = z*(pS0+z*(pS1+z*pS2)); 59 q = one+z*qS1; 60 s = sqrtf(z); 61 r = p/q; 62 w = r*s-pio2_lo; 63 return pi - (float)2.0*(s+w); 64 } else { /* x > 0.5 */ 65 int32_t idf; 66 z = (one-x)*(float)0.5; 67 s = sqrtf(z); 68 df = s; 69 GET_FLOAT_WORD(idf,df); 70 SET_FLOAT_WORD(df,idf&0xfffff000); 71 c = (z-df*df)/(s+df); 72 p = z*(pS0+z*(pS1+z*pS2)); 73 q = one+z*qS1; 74 r = p/q; 75 w = r*s+c; 76 return (float)2.0*(df+w); 77 } 78 }