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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* e_fmodf.c -- float version of e_fmod.c. |
| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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| 3 | */ |
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| 4 | |||
| 5 | /* |
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| 6 | * ==================================================== |
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 8 | * |
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 10 | * Permission to use, copy, modify, and distribute this |
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| 11 | * software is freely granted, provided that this notice |
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| 12 | * is preserved. |
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| 13 | * ==================================================== |
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| 14 | */ |
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| 15 | |||
| 16 | #ifndef lint |
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| 17 | static char rcsid[] = "$\Id: e_fmodf.c,v 1.2 1995/05/30 05:48:11 rgrimes Exp $"; |
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| 18 | #endif |
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| 19 | |||
| 20 | /* |
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| 21 | * __ieee754_fmodf(x,y) |
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| 22 | * Return x mod y in exact arithmetic |
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| 23 | * Method: shift and subtract |
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| 24 | */ |
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| 25 | |||
| 26 | #include "math.h" |
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| 27 | #include "math_private.h" |
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| 28 | |||
| 29 | #ifdef __STDC__ |
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| 30 | static const float one = 1.0, Zero[] = {0.0, -0.0,}; |
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| 31 | #else |
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| 32 | static float one = 1.0, Zero[] = {0.0, -0.0,}; |
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| 33 | #endif |
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| 34 | |||
| 35 | #ifdef __STDC__ |
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| 36 | float __ieee754_fmodf(float x, float y) |
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| 37 | #else |
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| 38 | float __ieee754_fmodf(x,y) |
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| 39 | float x,y ; |
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| 40 | #endif |
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| 41 | { |
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| 42 | int32_t n,hx,hy,hz,ix,iy,sx,i; |
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| 43 | |||
| 44 | GET_FLOAT_WORD(hx,x); |
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| 45 | GET_FLOAT_WORD(hy,y); |
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| 46 | sx = hx&0x80000000; /* sign of x */ |
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| 47 | hx ^=sx; /* |x| */ |
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| 48 | hy &= 0x7fffffff; /* |y| */ |
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| 49 | |||
| 50 | /* purge off exception values */ |
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| 51 | if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ |
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| 52 | (hy>0x7f800000)) /* or y is NaN */ |
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| 53 | return (x*y)/(x*y); |
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| 54 | if(hx<hy) return x; /* |x|<|y| return x */ |
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| 55 | if(hx==hy) |
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| 56 | return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ |
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| 57 | |||
| 58 | /* determine ix = ilogb(x) */ |
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| 59 | if(hx<0x00800000) { /* subnormal x */ |
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| 60 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
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| 61 | } else ix = (hx>>23)-127; |
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| 62 | |||
| 63 | /* determine iy = ilogb(y) */ |
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| 64 | if(hy<0x00800000) { /* subnormal y */ |
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| 65 | for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; |
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| 66 | } else iy = (hy>>23)-127; |
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| 67 | |||
| 68 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
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| 69 | if(ix >= -126) |
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| 70 | hx = 0x00800000|(0x007fffff&hx); |
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| 71 | else { /* subnormal x, shift x to normal */ |
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| 72 | n = -126-ix; |
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| 73 | hx = hx<<n; |
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| 74 | } |
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| 75 | if(iy >= -126) |
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| 76 | hy = 0x00800000|(0x007fffff&hy); |
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| 77 | else { /* subnormal y, shift y to normal */ |
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| 78 | n = -126-iy; |
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| 79 | hy = hy<<n; |
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| 80 | } |
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| 81 | |||
| 82 | /* fix point fmod */ |
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| 83 | n = ix - iy; |
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| 84 | while(n--) { |
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| 85 | hz=hx-hy; |
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| 86 | if(hz<0){hx = hx+hx;} |
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| 87 | else { |
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| 88 | if(hz==0) /* return sign(x)*0 */ |
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| 89 | return Zero[(u_int32_t)sx>>31]; |
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| 90 | hx = hz+hz; |
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| 91 | } |
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| 92 | } |
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| 93 | hz=hx-hy; |
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| 94 | if(hz>=0) {hx=hz;} |
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| 95 | |||
| 96 | /* convert back to floating value and restore the sign */ |
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| 97 | if(hx==0) /* return sign(x)*0 */ |
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| 98 | return Zero[(u_int32_t)sx>>31]; |
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| 99 | while(hx<0x00800000) { /* normalize x */ |
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| 100 | hx = hx+hx; |
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| 101 | iy -= 1; |
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| 102 | } |
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| 103 | if(iy>= -126) { /* normalize output */ |
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| 104 | hx = ((hx-0x00800000)|((iy+127)<<23)); |
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| 105 | SET_FLOAT_WORD(x,hx|sx); |
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| 106 | } else { /* subnormal output */ |
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| 107 | n = -126 - iy; |
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| 108 | hx >>= n; |
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| 109 | SET_FLOAT_WORD(x,hx|sx); |
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| 110 | x *= one; /* create necessary signal */ |
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| 111 | } |
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| 112 | return x; /* exact output */ |
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| 113 | } |