Mercurial > sdl-ios-xcode
annotate src/libm/s_scalbn.c @ 2847:7d020441fa81
Don't hardcode RECT for fragment program texture targets.
Now we can generate what a given system needs when compiling the shader.
author | Ryan C. Gordon <icculus@icculus.org> |
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date | Sun, 07 Dec 2008 07:06:34 +0000 |
parents | a98604b691c8 |
children | dc1eb82ffdaa |
rev | line source |
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Expanded the libm support and put it into a separate directory.
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1 /* @(#)s_scalbn.c 5.1 93/09/24 */ |
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2 /* |
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3 * ==================================================== |
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4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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5 * |
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6 * Developed at SunPro, a Sun Microsystems, Inc. business. |
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7 * Permission to use, copy, modify, and distribute this |
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8 * software is freely granted, provided that this notice |
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9 * is preserved. |
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10 * ==================================================== |
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11 */ |
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12 |
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13 #if defined(LIBM_SCCS) && !defined(lint) |
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14 static char rcsid[] = |
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15 "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $"; |
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16 #endif |
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17 |
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18 /* |
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19 * scalbn (double x, int n) |
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20 * scalbn(x,n) returns x* 2**n computed by exponent |
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21 * manipulation rather than by actually performing an |
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22 * exponentiation or a multiplication. |
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23 */ |
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24 |
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25 #include "math.h" |
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26 #include "math_private.h" |
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27 |
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28 libm_hidden_proto(copysign) |
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29 #ifdef __STDC__ |
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30 static const double |
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31 #else |
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32 static double |
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33 #endif |
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34 two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ |
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35 twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ |
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36 huge = 1.0e+300, tiny = 1.0e-300; |
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37 |
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38 libm_hidden_proto(scalbn) |
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39 #ifdef __STDC__ |
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40 double scalbn(double x, int n) |
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41 #else |
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42 double scalbn(x, n) |
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43 double x; |
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44 int n; |
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45 #endif |
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46 { |
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47 int32_t k, hx, lx; |
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48 EXTRACT_WORDS(hx, lx, x); |
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49 k = (hx & 0x7ff00000) >> 20; /* extract exponent */ |
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50 if (k == 0) { /* 0 or subnormal x */ |
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51 if ((lx | (hx & 0x7fffffff)) == 0) |
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52 return x; /* +-0 */ |
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53 x *= two54; |
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54 GET_HIGH_WORD(hx, x); |
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55 k = ((hx & 0x7ff00000) >> 20) - 54; |
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56 if (n < -50000) |
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57 return tiny * x; /*underflow */ |
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58 } |
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59 if (k == 0x7ff) |
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60 return x + x; /* NaN or Inf */ |
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61 k = k + n; |
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62 if (k > 0x7fe) |
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63 return huge * copysign(huge, x); /* overflow */ |
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64 if (k > 0) { /* normal result */ |
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65 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); |
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66 return x; |
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67 } |
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68 if (k <= -54) { |
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69 if (n > 50000) /* in case integer overflow in n+k */ |
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70 return huge * copysign(huge, x); /*overflow */ |
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71 else |
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72 return tiny * copysign(tiny, x); /*underflow */ |
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73 } |
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74 k += 54; /* subnormal result */ |
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75 SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); |
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76 return x * twom54; |
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77 } |
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78 |
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79 libm_hidden_def(scalbn) |