1 /* ef_fmod.c -- float version of e_fmod.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian (at) 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 * __ieee754_fmodf(x,y) 18 * Return x mod y in exact arithmetic 19 * Method: shift and subtract 20 */ 21 22 #include "fdlibm.h" 23 24 #ifdef __STDC__ 25 static const float one = 1.0, Zero[] = {0.0, -0.0,}; 26 #else 27 static float one = 1.0, Zero[] = {0.0, -0.0,}; 28 #endif 29 30 #ifdef __STDC__ 31 float __ieee754_fmodf(float x, float y) 32 #else 33 float __ieee754_fmodf(x,y) 34 float x,y ; 35 #endif 36 { 37 __int32_t n,hx,hy,hz,ix,iy,sx,i; 38 39 GET_FLOAT_WORD(hx,x); 40 GET_FLOAT_WORD(hy,y); 41 sx = hx&0x80000000; /* sign of x */ 42 hx ^=sx; /* |x| */ 43 hy &= 0x7fffffff; /* |y| */ 44 45 /* purge off exception values */ 46 if(FLT_UWORD_IS_ZERO(hy)|| 47 !FLT_UWORD_IS_FINITE(hx)|| 48 FLT_UWORD_IS_NAN(hy)) 49 return (x*y)/(x*y); 50 if(hx<hy) return x; /* |x|<|y| return x */ 51 if(hx==hy) 52 return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ 53 54 /* Note: y cannot be zero if we reach here. */ 55 56 /* determine ix = ilogb(x) */ 57 if(FLT_UWORD_IS_SUBNORMAL(hx)) { /* subnormal x */ 58 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; 59 } else ix = (hx>>23)-127; 60 61 /* determine iy = ilogb(y) */ 62 if(FLT_UWORD_IS_SUBNORMAL(hy)) { /* subnormal y */ 63 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; 64 } else iy = (hy>>23)-127; 65 66 /* set up {hx,lx}, {hy,ly} and align y to x */ 67 if(ix >= -126) 68 hx = 0x00800000|(0x007fffff&hx); 69 else { /* subnormal x, shift x to normal */ 70 n = -126-ix; 71 hx = hx<<n; 72 } 73 if(iy >= -126) 74 hy = 0x00800000|(0x007fffff&hy); 75 else { /* subnormal y, shift y to normal */ 76 n = -126-iy; 77 hy = hy<<n; 78 } 79 80 /* fix point fmod */ 81 n = ix - iy; 82 while(n--) { 83 hz=hx-hy; 84 if(hz<0){hx = hx+hx;} 85 else { 86 if(hz==0) /* return sign(x)*0 */ 87 return Zero[(__uint32_t)sx>>31]; 88 hx = hz+hz; 89 } 90 } 91 hz=hx-hy; 92 if(hz>=0) {hx=hz;} 93 94 /* convert back to floating value and restore the sign */ 95 if(hx==0) /* return sign(x)*0 */ 96 return Zero[(__uint32_t)sx>>31]; 97 while(hx<0x00800000) { /* normalize x */ 98 hx = hx+hx; 99 iy -= 1; 100 } 101 if(iy>= -126) { /* normalize output */ 102 hx = ((hx-0x00800000)|((iy+127)<<23)); 103 SET_FLOAT_WORD(x,hx|sx); 104 } else { /* subnormal output */ 105 /* If denormals are not supported, this code will generate a 106 zero representation. */ 107 n = -126 - iy; 108 hx >>= n; 109 SET_FLOAT_WORD(x,hx|sx); 110 x *= one; /* create necessary signal */ 111 } 112 return x; /* exact output */ 113 } 114
