1 | /* ef_fmod.c -- float version of e_fmod.c. |
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2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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3 | */ |
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4 | |
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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 | |
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16 | /* |
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17 | * fmodf(x,y) |
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18 | * Return x mod y in exact arithmetic |
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19 | * Method: shift and subtract |
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20 | */ |
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21 | |
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22 | #include "fdlibm.h" |
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23 | #include "zmath.h" |
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24 | |
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25 | static const float one = 1.0, Zero[] = {0.0, -0.0,}; |
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26 | |
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27 | float |
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28 | fmodf (float x, |
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29 | float y) |
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30 | { |
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31 | __int32_t n,hx,hy,hz,ix,iy,sx,i; |
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32 | |
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33 | GET_FLOAT_WORD(hx,x); |
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34 | GET_FLOAT_WORD(hy,y); |
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35 | sx = hx&0x80000000; /* sign of x */ |
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36 | hx ^=sx; /* |x| */ |
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37 | hy &= 0x7fffffff; /* |y| */ |
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38 | |
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39 | /* purge off exception values */ |
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40 | if(hy==0||(hx>=0x7f800000)|| /* y=0,or x not finite */ |
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41 | (hy>0x7f800000)) /* or y is NaN */ |
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42 | return (x*y)/(x*y); |
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43 | if(hx<hy) return x; /* |x|<|y| return x */ |
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44 | if(hx==hy) |
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45 | return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ |
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46 | |
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47 | /* determine ix = ilogb(x) */ |
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48 | if(hx<0x00800000) { /* subnormal x */ |
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49 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
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50 | } else ix = (hx>>23)-127; |
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51 | |
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52 | /* determine iy = ilogb(y) */ |
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53 | if(hy<0x00800000) { /* subnormal y */ |
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54 | for (iy = -126,i=(hy<<8); i>=0; i<<=1) iy -=1; |
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55 | } else iy = (hy>>23)-127; |
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56 | |
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57 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
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58 | if(ix >= -126) |
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59 | hx = 0x00800000|(0x007fffff&hx); |
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60 | else { /* subnormal x, shift x to normal */ |
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61 | n = -126-ix; |
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62 | hx = hx<<n; |
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63 | } |
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64 | if(iy >= -126) |
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65 | hy = 0x00800000|(0x007fffff&hy); |
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66 | else { /* subnormal y, shift y to normal */ |
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67 | n = -126-iy; |
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68 | hy = hy<<n; |
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69 | } |
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70 | |
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71 | /* fix point fmod */ |
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72 | n = ix - iy; |
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73 | while(n--) { |
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74 | hz=hx-hy; |
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75 | if(hz<0){hx = hx+hx;} |
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76 | else { |
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77 | if(hz==0) /* return sign(x)*0 */ |
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78 | return Zero[(__uint32_t)sx>>31]; |
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79 | hx = hz+hz; |
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80 | } |
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81 | } |
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82 | hz=hx-hy; |
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83 | if(hz>=0) {hx=hz;} |
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84 | |
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85 | /* convert back to floating value and restore the sign */ |
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86 | if(hx==0) /* return sign(x)*0 */ |
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87 | return Zero[(__uint32_t)sx>>31]; |
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88 | while(hx<0x00800000) { /* normalize x */ |
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89 | hx = hx+hx; |
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90 | iy -= 1; |
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91 | } |
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92 | if(iy>= -126) { /* normalize output */ |
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93 | hx = ((hx-0x00800000)|((iy+127)<<23)); |
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94 | SET_FLOAT_WORD(x,hx|sx); |
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95 | } else { /* subnormal output */ |
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96 | n = -126 - iy; |
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97 | hx >>= n; |
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98 | SET_FLOAT_WORD(x,hx|sx); |
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99 | x *= one; /* create necessary signal */ |
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100 | } |
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101 | return x; /* exact output */ |
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102 | } |
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