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 hx, hy, hz, ix, iy, n, sx; 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 nan_mix_op(x, y, *)/nan_mix_op(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) 48 ix = subnormal_ilogbf(hx); 49 else 50 ix = (hx>>23)-127; 51 52 /* determine iy = ilogb(y) */ 53 if(hy<0x00800000) 54 iy = subnormal_ilogbf(hy); 55 else 56 iy = (hy>>23)-127; 57 58 /* set up {hx,lx}, {hy,ly} and align y to x */ 59 if(ix >= -126) 60 hx = 0x00800000|(0x007fffff&hx); 61 else { /* subnormal x, shift x to normal */ 62 n = -126-ix; 63 hx = hx<<n; 64 } 65 if(iy >= -126) 66 hy = 0x00800000|(0x007fffff&hy); 67 else { /* subnormal y, shift y to normal */ 68 n = -126-iy; 69 hy = hy<<n; 70 } 71 72 /* fix point fmod */ 73 n = ix - iy; 74 while(n--) { 75 hz=hx-hy; 76 if(hz<0){hx = hx+hx;} 77 else { 78 if(hz==0) /* return sign(x)*0 */ 79 return Zero[(u_int32_t)sx>>31]; 80 hx = hz+hz; 81 } 82 } 83 hz=hx-hy; 84 if(hz>=0) {hx=hz;} 85 86 /* convert back to floating value and restore the sign */ 87 if(hx==0) /* return sign(x)*0 */ 88 return Zero[(u_int32_t)sx>>31]; 89 while(hx<0x00800000) { /* normalize x */ 90 hx = hx+hx; 91 iy -= 1; 92 } 93 if(iy>= -126) { /* normalize output */ 94 hx = ((hx-0x00800000)|((iy+127)<<23)); 95 SET_FLOAT_WORD(x,hx|sx); 96 } else { /* subnormal output */ 97 n = -126 - iy; 98 hx >>= n; 99 SET_FLOAT_WORD(x,hx|sx); 100 x *= one; /* create necessary signal */ 101 } 102 return x; /* exact output */ 103 } 104