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 /* 17 * fmodf(x,y) 18 * Return x mod y in exact arithmetic 19 * Method: shift and subtract 20 */ 21 22 #include "math.h" 23 #include "math_private.h" 24 25 static const float one = 1.0, Zero[] = {0.0, -0.0,}; 26 27 float 28 fmodf(float x, float y) 29 { 30 int32_t n,hx,hy,hz,ix,iy,sx,i; 31 32 GET_FLOAT_WORD(hx,x); 33 GET_FLOAT_WORD(hy,y); 34 sx = hx&0x80000000; /* sign of x */ 35 hx ^=sx; /* |x| */ 36 hy &= 0x7fffffff; /* |y| */ 37 38 /* purge off exception values */ 39 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ 40 (hy>0x7f800000)) /* or y is NaN */ 41 return (x*y)/(x*y); 42 if(hx<hy) return x; /* |x|<|y| return x */ 43 if(hx==hy) 44 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 45 46 /* determine ix = ilogb(x) */ 47 if(hx<0x00800000) { /* subnormal x */ 48 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; 49 } else ix = (hx>>23)-127; 50 51 /* determine iy = ilogb(y) */ 52 if(hy<0x00800000) { /* subnormal y */ 53 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; 54 } else iy = (hy>>23)-127; 55 56 /* set up {hx,lx}, {hy,ly} and align y to x */ 57 if(ix >= -126) 58 hx = 0x00800000|(0x007fffff&hx); 59 else { /* subnormal x, shift x to normal */ 60 n = -126-ix; 61 hx = hx<<n; 62 } 63 if(iy >= -126) 64 hy = 0x00800000|(0x007fffff&hy); 65 else { /* subnormal y, shift y to normal */ 66 n = -126-iy; 67 hy = hy<<n; 68 } 69 70 /* fix point fmod */ 71 n = ix - iy; 72 while(n--) { 73 hz=hx-hy; 74 if(hz<0){hx = hx+hx;} 75 else { 76 if(hz==0) /* return sign(x)*0 */ 77 return Zero[(u_int32_t)sx>>31]; 78 hx = hz+hz; 79 } 80 } 81 hz=hx-hy; 82 if(hz>=0) {hx=hz;} 83 84 /* convert back to floating value and restore the sign */ 85 if(hx==0) /* return sign(x)*0 */ 86 return Zero[(u_int32_t)sx>>31]; 87 while(hx<0x00800000) { /* normalize x */ 88 hx = hx+hx; 89 iy -= 1; 90 } 91 if(iy>= -126) { /* normalize output */ 92 hx = ((hx-0x00800000)|((iy+127)<<23)); 93 SET_FLOAT_WORD(x,hx|sx); 94 } else { /* subnormal output */ 95 n = -126 - iy; 96 hx >>= n; 97 SET_FLOAT_WORD(x,hx|sx); 98 x *= one; /* create necessary signal */ 99 } 100 return x; /* exact output */ 101 } 102