1 /* e_fmodf.c -- float version of e_fmod.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 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: e_fmodf.c,v 1.7 2002/05/26 22:01:49 wiz Exp $"); 19 #endif 20 21 /* 22 * __ieee754_fmodf(x,y) 23 * Return x mod y in exact arithmetic 24 * Method: shift and subtract 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 static const float one = 1.0, Zero[] = {0.0, -0.0,}; 31 32 float 33 __ieee754_fmodf(float x, float y) 34 { 35 int32_t n,hx,hy,hz,ix,iy,sx,i; 36 37 GET_FLOAT_WORD(hx,x); 38 GET_FLOAT_WORD(hy,y); 39 sx = hx&0x80000000; /* sign of x */ 40 hx ^=sx; /* |x| */ 41 hy &= 0x7fffffff; /* |y| */ 42 43 /* purge off exception values */ 44 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ 45 (hy>0x7f800000)) /* or y is NaN */ 46 return (x*y)/(x*y); 47 if(hx<hy) return x; /* |x|<|y| return x */ 48 if(hx==hy) 49 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 50 51 /* determine ix = ilogb(x) */ 52 if(hx<0x00800000) { /* subnormal x */ 53 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; 54 } else ix = (hx>>23)-127; 55 56 /* determine iy = ilogb(y) */ 57 if(hy<0x00800000) { /* subnormal y */ 58 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; 59 } else iy = (hy>>23)-127; 60 61 /* set up {hx,lx}, {hy,ly} and align y to x */ 62 if(ix >= -126) 63 hx = 0x00800000|(0x007fffff&hx); 64 else { /* subnormal x, shift x to normal */ 65 n = -126-ix; 66 hx = hx<<n; 67 } 68 if(iy >= -126) 69 hy = 0x00800000|(0x007fffff&hy); 70 else { /* subnormal y, shift y to normal */ 71 n = -126-iy; 72 hy = hy<<n; 73 } 74 75 /* fix point fmod */ 76 n = ix - iy; 77 while(n--) { 78 hz=hx-hy; 79 if(hz<0){hx = hx+hx;} 80 else { 81 if(hz==0) /* return sign(x)*0 */ 82 return Zero[(u_int32_t)sx>>31]; 83 hx = hz+hz; 84 } 85 } 86 hz=hx-hy; 87 if(hz>=0) {hx=hz;} 88 89 /* convert back to floating value and restore the sign */ 90 if(hx==0) /* return sign(x)*0 */ 91 return Zero[(u_int32_t)sx>>31]; 92 while(hx<0x00800000) { /* normalize x */ 93 hx = hx+hx; 94 iy -= 1; 95 } 96 if(iy>= -126) { /* normalize output */ 97 hx = ((hx-0x00800000)|((iy+127)<<23)); 98 SET_FLOAT_WORD(x,hx|sx); 99 } else { /* subnormal output */ 100 n = -126 - iy; 101 hx >>= n; 102 SET_FLOAT_WORD(x,hx|sx); 103 x *= one; /* create necessary signal */ 104 } 105 return x; /* exact output */ 106 } 107