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 #include <sys/cdefs.h> 14 /* 15 * fmod(x,y) 16 * Return x mod y in exact arithmetic 17 * Method: shift and subtract 18 */ 19 20 #include <float.h> 21 22 #include "math.h" 23 #include "math_private.h" 24 25 static const double one = 1.0, Zero[] = {0.0, -0.0,}; 26 27 double 28 fmod(double x, double y) 29 { 30 int32_t n,hx,hy,hz,ix,iy,sx,i; 31 u_int32_t lx,ly,lz; 32 33 EXTRACT_WORDS(hx,lx,x); 34 EXTRACT_WORDS(hy,ly,y); 35 sx = hx&0x80000000; /* sign of x */ 36 hx ^=sx; /* |x| */ 37 hy &= 0x7fffffff; /* |y| */ 38 39 /* purge off exception values */ 40 if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ 41 ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ 42 return nan_mix_op(x, y, *)/nan_mix_op(x, y, *); 43 if(hx<=hy) { 44 if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */ 45 if(lx==ly) 46 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 47 } 48 49 /* determine ix = ilogb(x) */ 50 if(hx<0x00100000) { /* subnormal x */ 51 if(hx==0) { 52 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1; 53 } else { 54 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1; 55 } 56 } else ix = (hx>>20)-1023; 57 58 /* determine iy = ilogb(y) */ 59 if(hy<0x00100000) { /* subnormal y */ 60 if(hy==0) { 61 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1; 62 } else { 63 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1; 64 } 65 } else iy = (hy>>20)-1023; 66 67 /* set up {hx,lx}, {hy,ly} and align y to x */ 68 if(ix >= -1022) 69 hx = 0x00100000|(0x000fffff&hx); 70 else { /* subnormal x, shift x to normal */ 71 n = -1022-ix; 72 if(n<=31) { 73 hx = (hx<<n)|(lx>>(32-n)); 74 lx <<= n; 75 } else { 76 hx = lx<<(n-32); 77 lx = 0; 78 } 79 } 80 if(iy >= -1022) 81 hy = 0x00100000|(0x000fffff&hy); 82 else { /* subnormal y, shift y to normal */ 83 n = -1022-iy; 84 if(n<=31) { 85 hy = (hy<<n)|(ly>>(32-n)); 86 ly <<= n; 87 } else { 88 hy = ly<<(n-32); 89 ly = 0; 90 } 91 } 92 93 /* fix point fmod */ 94 n = ix - iy; 95 while(n--) { 96 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; 97 if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;} 98 else { 99 if((hz|lz)==0) /* return sign(x)*0 */ 100 return Zero[(u_int32_t)sx>>31]; 101 hx = hz+hz+(lz>>31); lx = lz+lz; 102 } 103 } 104 hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; 105 if(hz>=0) {hx=hz;lx=lz;} 106 107 /* convert back to floating value and restore the sign */ 108 if((hx|lx)==0) /* return sign(x)*0 */ 109 return Zero[(u_int32_t)sx>>31]; 110 while(hx<0x00100000) { /* normalize x */ 111 hx = hx+hx+(lx>>31); lx = lx+lx; 112 iy -= 1; 113 } 114 if(iy>= -1022) { /* normalize output */ 115 hx = ((hx-0x00100000)|((iy+1023)<<20)); 116 INSERT_WORDS(x,hx|sx,lx); 117 } else { /* subnormal output */ 118 n = -1022 - iy; 119 if(n<=20) { 120 lx = (lx>>n)|((u_int32_t)hx<<(32-n)); 121 hx >>= n; 122 } else if (n<=31) { 123 lx = (hx<<(32-n))|(lx>>n); hx = sx; 124 } else { 125 lx = hx>>(n-32); hx = sx; 126 } 127 INSERT_WORDS(x,hx|sx,lx); 128 x *= one; /* create necessary signal */ 129 } 130 return x; /* exact output */ 131 } 132 133 #if (LDBL_MANT_DIG == 53) 134 __weak_reference(fmod, fmodl); 135 #endif 136