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 //__FBSDID("$FreeBSD: src/lib/msun/src/e_fmodf.c,v 1.7 2008/02/22 02:30:34 das Exp $"); 18 19 /* 20 * __ieee754_fmodf(x,y) 21 * Return x mod y in exact arithmetic 22 * Method: shift and subtract 23 */ 24 25 #include "openlibm.h" 26 #include "math_private.h" 27 28 static const float one = 1.0, Zero[] = {0.0, -0.0,}; 29 30 float 31 __ieee754_fmodf(float x, float y) 32 { 33 int32_t n,hx,hy,hz,ix,iy,sx,i; 34 35 GET_FLOAT_WORD(hx,x); 36 GET_FLOAT_WORD(hy,y); 37 sx = hx&0x80000000; /* sign of x */ 38 hx ^=sx; /* |x| */ 39 hy &= 0x7fffffff; /* |y| */ 40 41 /* purge off exception values */ 42 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ 43 (hy>0x7f800000)) /* or y is NaN */ 44 return (x*y)/(x*y); 45 if(hx<hy) return x; /* |x|<|y| return x */ 46 if(hx==hy) 47 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 48 49 /* determine ix = ilogb(x) */ 50 if(hx<0x00800000) { /* subnormal x */ 51 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; 52 } else ix = (hx>>23)-127; 53 54 /* determine iy = ilogb(y) */ 55 if(hy<0x00800000) { /* subnormal y */ 56 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; 57 } else iy = (hy>>23)-127; 58 59 /* set up {hx,lx}, {hy,ly} and align y to x */ 60 if(ix >= -126) 61 hx = 0x00800000|(0x007fffff&hx); 62 else { /* subnormal x, shift x to normal */ 63 n = -126-ix; 64 hx = hx<<n; 65 } 66 if(iy >= -126) 67 hy = 0x00800000|(0x007fffff&hy); 68 else { /* subnormal y, shift y to normal */ 69 n = -126-iy; 70 hy = hy<<n; 71 } 72 73 /* fix point fmod */ 74 n = ix - iy; 75 while(n--) { 76 hz=hx-hy; 77 if(hz<0){hx = hx+hx;} 78 else { 79 if(hz==0) /* return sign(x)*0 */ 80 return Zero[(u_int32_t)sx>>31]; 81 hx = hz+hz; 82 } 83 } 84 hz=hx-hy; 85 if(hz>=0) {hx=hz;} 86 87 /* convert back to floating value and restore the sign */ 88 if(hx==0) /* return sign(x)*0 */ 89 return Zero[(u_int32_t)sx>>31]; 90 while(hx<0x00800000) { /* normalize x */ 91 hx = hx+hx; 92 iy -= 1; 93 } 94 if(iy>= -126) { /* normalize output */ 95 hx = ((hx-0x00800000)|((iy+127)<<23)); 96 SET_FLOAT_WORD(x,hx|sx); 97 } else { /* subnormal output */ 98 n = -126 - iy; 99 hx >>= n; 100 SET_FLOAT_WORD(x,hx|sx); 101 x *= one; /* create necessary signal */ 102 } 103 return x; /* exact output */ 104 } 105