1 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunSoft, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 /* 14 * fmod(x,y) 15 * Return x mod y in exact arithmetic 16 * Method: shift and subtract 17 */ 18 19 #include <float.h> 20 21 #include "math.h" 22 #include "math_private.h" 23 24 static const double one = 1.0, Zero[] = {0.0, -0.0,}; 25 26 double 27 fmod(double x, double y) 28 { 29 int32_t hx, hy, hz, ix, iy, n, sx; 30 u_int32_t lx, ly, lz; 31 32 EXTRACT_WORDS(hx,lx,x); 33 EXTRACT_WORDS(hy,ly,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|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ 40 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ 41 return nan_mix_op(x, y, *)/nan_mix_op(x, y, *); 42 if(hx<=hy) { 43 if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */ 44 if(lx==ly) 45 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 46 } 47 48 /* determine ix = ilogb(x) */ 49 if(hx<0x00100000) 50 ix = subnormal_ilogb(hx, lx); 51 else 52 ix = (hx>>20)-1023; 53 54 /* determine iy = ilogb(y) */ 55 if(hy<0x00100000) 56 iy = subnormal_ilogb(hy, ly); 57 else 58 iy = (hy>>20)-1023; 59 60 /* set up {hx,lx}, {hy,ly} and align y to x */ 61 if(ix >= -1022) 62 hx = 0x00100000|(0x000fffff&hx); 63 else { /* subnormal x, shift x to normal */ 64 n = -1022-ix; 65 if(n<=31) { 66 hx = (hx<<n)|(lx>>(32-n)); 67 lx <<= n; 68 } else { 69 hx = lx<<(n-32); 70 lx = 0; 71 } 72 } 73 if(iy >= -1022) 74 hy = 0x00100000|(0x000fffff&hy); 75 else { /* subnormal y, shift y to normal */ 76 n = -1022-iy; 77 if(n<=31) { 78 hy = (hy<<n)|(ly>>(32-n)); 79 ly <<= n; 80 } else { 81 hy = ly<<(n-32); 82 ly = 0; 83 } 84 } 85 86 /* fix point fmod */ 87 n = ix - iy; 88 while(n--) { 89 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; 90 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;} 91 else { 92 if((hz|lz)==0) /* return sign(x)*0 */ 93 return Zero[(u_int32_t)sx>>31]; 94 hx = hz+hz+(lz>>31); lx = lz+lz; 95 } 96 } 97 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; 98 if(hz>=0) {hx=hz;lx=lz;} 99 100 /* convert back to floating value and restore the sign */ 101 if((hx|lx)==0) /* return sign(x)*0 */ 102 return Zero[(u_int32_t)sx>>31]; 103 while(hx<0x00100000) { /* normalize x */ 104 hx = hx+hx+(lx>>31); lx = lx+lx; 105 iy -= 1; 106 } 107 if(iy>= -1022) { /* normalize output */ 108 hx = ((hx-0x00100000)|((iy+1023)<<20)); 109 INSERT_WORDS(x,hx|sx,lx); 110 } else { /* subnormal output */ 111 n = -1022 - iy; 112 if(n<=20) { 113 lx = (lx>>n)|((u_int32_t)hx<<(32-n)); 114 hx >>= n; 115 } else if (n<=31) { 116 lx = (hx<<(32-n))|(lx>>n); hx = sx; 117 } else { 118 lx = hx>>(n-32); hx = sx; 119 } 120 INSERT_WORDS(x,hx|sx,lx); 121 x *= one; /* create necessary signal */ 122 } 123 return x; /* exact output */ 124 } 125 126 #if (LDBL_MANT_DIG == 53) 127 __weak_reference(fmod, fmodl); 128 #endif 129