| 1 | /* |
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| 2 | * ==================================================== |
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| 3 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 4 | * |
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| 5 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 6 | * Permission to use, copy, modify, and distribute this |
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| 7 | * software is freely granted, provided that this notice |
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| 8 | * is preserved. |
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| 9 | * ==================================================== |
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| 10 | */ |
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| 11 | |
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| 12 | /* |
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| 13 | * Modified for ALMOS-MKH OS at UPMC, France, August 2018. (Alain Greiner) |
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| 14 | */ |
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| 15 | |
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| 16 | /* |
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| 17 | * rint(x) |
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| 18 | * Return x rounded to integral value according to the prevailing |
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| 19 | * rounding mode. |
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| 20 | * Method: |
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| 21 | * Using floating addition. |
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| 22 | * Exception: |
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| 23 | * Inexact flag raised if x not equal to rint(x). |
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| 24 | */ |
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| 25 | |
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| 26 | #include "math.h" |
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| 27 | #include "math_private.h" |
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| 28 | |
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| 29 | static const double |
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| 30 | TWO52[2]={ |
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| 31 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
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| 32 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
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| 33 | }; |
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| 34 | |
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| 35 | double rint(double x) |
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| 36 | { |
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| 37 | int32_t i0, j0, sx; |
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| 38 | uint32_t i,i1; |
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| 39 | double t; |
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| 40 | /* We use w = x + 2^52; t = w - 2^52; trick to round x to integer. |
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| 41 | * This trick requires that compiler does not optimize it |
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| 42 | * by keeping intermediate result w in a register wider than double. |
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| 43 | * Declaring w volatile assures that value gets truncated to double |
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| 44 | * (unfortunately, it also forces store+load): |
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| 45 | */ |
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| 46 | volatile double w; |
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| 47 | |
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| 48 | EXTRACT_WORDS(i0,i1,x); |
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| 49 | /* Unbiased exponent */ |
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| 50 | j0 = ((((uint32_t)i0) >> 20)&0x7ff)-0x3ff; |
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| 51 | |
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| 52 | if (j0 > 51) { |
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| 53 | //Why bother? Just returning x works too |
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| 54 | //if (j0 == 0x400) /* inf or NaN */ |
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| 55 | // return x+x; |
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| 56 | return x; /* x is integral */ |
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| 57 | } |
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| 58 | |
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| 59 | /* Sign */ |
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| 60 | sx = ((uint32_t)i0) >> 31; |
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| 61 | |
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| 62 | if (j0<20) { |
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| 63 | if (j0<0) { /* |x| < 1 */ |
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| 64 | if (((i0&0x7fffffff)|i1)==0) return x; |
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| 65 | i1 |= (i0&0x0fffff); |
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| 66 | i0 &= 0xfffe0000; |
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| 67 | i0 |= ((i1|-i1)>>12)&0x80000; |
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| 68 | SET_HIGH_WORD(x,i0); |
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| 69 | w = TWO52[sx]+x; |
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| 70 | t = w-TWO52[sx]; |
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| 71 | GET_HIGH_WORD(i0,t); |
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| 72 | SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); |
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| 73 | return t; |
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| 74 | } else { |
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| 75 | i = (0x000fffff)>>j0; |
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| 76 | if (((i0&i)|i1)==0) return x; /* x is integral */ |
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| 77 | i>>=1; |
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| 78 | if (((i0&i)|i1)!=0) { |
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| 79 | if (j0==19) i1 = 0x40000000; |
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| 80 | else i0 = (i0&(~i))|((0x20000)>>j0); |
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| 81 | } |
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| 82 | } |
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| 83 | } else { |
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| 84 | i = ((uint32_t)(0xffffffff))>>(j0-20); |
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| 85 | if ((i1&i)==0) return x; /* x is integral */ |
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| 86 | i>>=1; |
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| 87 | if ((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); |
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| 88 | } |
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| 89 | INSERT_WORDS(x,i0,i1); |
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| 90 | w = TWO52[sx]+x; |
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| 91 | return w-TWO52[sx]; |
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| 92 | } |
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