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 #include <sys/cdefs.h> 17 #if defined(LIBM_SCCS) && !defined(lint) 18 __RCSID("$NetBSD: e_fmodf.c,v 1.6 1999/07/02 15:37:39 simonb Exp $"); 19 #endif 20 21 /* 22 * __ieee754_fmodf(x,y) 23 * Return x mod y in exact arithmetic 24 * Method: shift and subtract 25 */ 26 27 #include "math.h" 28 #include "math_private.h" 29 30 #ifdef __STDC__ 31 static const float one = 1.0, Zero[] = {0.0, -0.0,}; 32 #else 33 static float one = 1.0, Zero[] = {0.0, -0.0,}; 34 #endif 35 36 #ifdef __STDC__ 37 float __ieee754_fmodf(float x, float y) 38 #else 39 float __ieee754_fmodf(x,y) 40 float x,y ; 41 #endif 42 { 43 int32_t n,hx,hy,hz,ix,iy,sx,i; 44 45 GET_FLOAT_WORD(hx,x); 46 GET_FLOAT_WORD(hy,y); 47 sx = hx&0x80000000; /* sign of x */ 48 hx ^=sx; /* |x| */ 49 hy &= 0x7fffffff; /* |y| */ 50 51 /* purge off exception values */ 52 if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ 53 (hy>0x7f800000)) /* or y is NaN */ 54 return (x*y)/(x*y); 55 if(hx<hy) return x; /* |x|<|y| return x */ 56 if(hx==hy) 57 return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ 58 59 /* determine ix = ilogb(x) */ 60 if(hx<0x00800000) { /* subnormal x */ 61 for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; 62 } else ix = (hx>>23)-127; 63 64 /* determine iy = ilogb(y) */ 65 if(hy<0x00800000) { /* subnormal y */ 66 for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; 67 } else iy = (hy>>23)-127; 68 69 /* set up {hx,lx}, {hy,ly} and align y to x */ 70 if(ix >= -126) 71 hx = 0x00800000|(0x007fffff&hx); 72 else { /* subnormal x, shift x to normal */ 73 n = -126-ix; 74 hx = hx<<n; 75 } 76 if(iy >= -126) 77 hy = 0x00800000|(0x007fffff&hy); 78 else { /* subnormal y, shift y to normal */ 79 n = -126-iy; 80 hy = hy<<n; 81 } 82 83 /* fix point fmod */ 84 n = ix - iy; 85 while(n--) { 86 hz=hx-hy; 87 if(hz<0){hx = hx+hx;} 88 else { 89 if(hz==0) /* return sign(x)*0 */ 90 return Zero[(u_int32_t)sx>>31]; 91 hx = hz+hz; 92 } 93 } 94 hz=hx-hy; 95 if(hz>=0) {hx=hz;} 96 97 /* convert back to floating value and restore the sign */ 98 if(hx==0) /* return sign(x)*0 */ 99 return Zero[(u_int32_t)sx>>31]; 100 while(hx<0x00800000) { /* normalize x */ 101 hx = hx+hx; 102 iy -= 1; 103 } 104 if(iy>= -126) { /* normalize output */ 105 hx = ((hx-0x00800000)|((iy+127)<<23)); 106 SET_FLOAT_WORD(x,hx|sx); 107 } else { /* subnormal output */ 108 n = -126 - iy; 109 hx >>= n; 110 SET_FLOAT_WORD(x,hx|sx); 111 x *= one; /* create necessary signal */ 112 } 113 return x; /* exact output */ 114 } 115