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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* @(#)s_rint.c 5.1 93/09/24 */ |
| 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 | |||
| 13 | #ifndef lint |
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| 14 | static char rcsid[] = "$\Id: s_rint.c,v 1.3.2.1 1997/02/23 11:03:20 joerg Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* |
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| 18 | * rint(x) |
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| 19 | * Return x rounded to integral value according to the prevailing |
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| 20 | * rounding mode. |
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| 21 | * Method: |
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| 22 | * Using floating addition. |
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| 23 | * Exception: |
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| 24 | * Inexact flag raised if x not equal to rint(x). |
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| 25 | */ |
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| 26 | |||
| 27 | #include "math.h" |
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| 28 | #include "math_private.h" |
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| 29 | |||
| 30 | /* |
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| 31 | * TWO23 is long double instead of double to avoid a bug in gcc. Without |
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| 32 | * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have double |
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| 33 | * precision and doesn't clip them to double precision when they are |
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| 34 | * assigned and returned. Use long double even in the !__STDC__ case in |
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| 35 | * case this is compiled with gcc -traditional. |
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| 36 | */ |
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| 37 | #ifdef __STDC__ |
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| 38 | static const long double |
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| 39 | #else |
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| 40 | static long double |
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| 41 | #endif |
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| 42 | TWO52[2]={ |
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| 43 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
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| 44 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
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| 45 | }; |
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| 46 | |||
| 47 | #ifdef __STDC__ |
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| 48 | double __generic_rint(double x) |
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| 49 | #else |
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| 50 | double __generic_rint(x) |
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| 51 | double x; |
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| 52 | #endif |
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| 53 | { |
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| 54 | int32_t i0,j0,sx; |
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| 55 | u_int32_t i,i1; |
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| 56 | double w,t; |
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| 57 | EXTRACT_WORDS(i0,i1,x); |
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| 58 | sx = (i0>>31)&1; |
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| 59 | j0 = ((i0>>20)&0x7ff)-0x3ff; |
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| 60 | if(j0<20) { |
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| 61 | if(j0<0) { |
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| 62 | if(((i0&0x7fffffff)|i1)==0) return x; |
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| 63 | i1 |= (i0&0x0fffff); |
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| 64 | i0 &= 0xfffe0000; |
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| 65 | i0 |= ((i1|-i1)>>12)&0x80000; |
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| 66 | SET_HIGH_WORD(x,i0); |
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| 67 | w = TWO52[sx]+x; |
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| 68 | t = w-TWO52[sx]; |
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| 69 | GET_HIGH_WORD(i0,t); |
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| 70 | SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); |
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| 71 | return t; |
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| 72 | } else { |
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| 73 | i = (0x000fffff)>>j0; |
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| 74 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
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| 75 | i>>=1; |
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| 76 | if(((i0&i)|i1)!=0) { |
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| 77 | if(j0==19) i1 = 0x40000000; else |
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| 78 | i0 = (i0&(~i))|((0x20000)>>j0); |
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| 79 | } |
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| 80 | } |
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| 81 | } else if (j0>51) { |
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| 82 | if(j0==0x400) return x+x; /* inf or NaN */ |
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| 83 | else return x; /* x is integral */ |
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| 84 | } else { |
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| 85 | i = ((u_int32_t)(0xffffffff))>>(j0-20); |
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| 86 | if((i1&i)==0) return x; /* x is integral */ |
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| 87 | i>>=1; |
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| 88 | if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); |
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| 89 | } |
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| 90 | INSERT_WORDS(x,i0,i1); |
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| 91 | w = TWO52[sx]+x; |
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| 92 | return w-TWO52[sx]; |
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| 93 | } |