projects / uclibc-ng.git / blame
| Commit | Line | Data |
|---|---|---|
| 7ce331c0 EA |
1 | /* |
| 2 | * ==================================================== | |
| 3 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
| 4 | * | |
| 5 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
| 6 | * Permission to use, copy, modify, and distribute this | |
| c4e44e97 | 7 | * software is freely granted, provided that this notice |
| 7ce331c0 EA |
8 | * is preserved. |
| 9 | * ==================================================== | |
| 10 | */ | |
| 11 | ||
| 7ce331c0 EA |
12 | /* |
| 13 | * rint(x) | |
| 14 | * Return x rounded to integral value according to the prevailing | |
| 15 | * rounding mode. | |
| 16 | * Method: | |
| 17 | * Using floating addition. | |
| 18 | * Exception: | |
| 19 | * Inexact flag raised if x not equal to rint(x). | |
| 20 | */ | |
| 21 | ||
| 22 | #include "math.h" | |
| 23 | #include "math_private.h" | |
| 24 | ||
| 7ce331c0 | 25 | static const double |
| 7ce331c0 EA |
26 | TWO52[2]={ |
| 27 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ | |
| 28 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ | |
| 29 | }; | |
| 30 | ||
| 38b7304e | 31 | double rint(double x) |
| 7ce331c0 | 32 | { |
| c61c6d98 | 33 | int32_t i0, _j0, sx; |
| 7ce331c0 | 34 | u_int32_t i,i1; |
| 4435b3ae DV |
35 | double t; |
| 36 | /* We use w = x + 2^52; t = w - 2^52; trick to round x to integer. | |
| 37 | * This trick requires that compiler does not optimize it | |
| 38 | * by keeping intermediate result w in a register wider than double. | |
| 39 | * Declaring w volatile assures that value gets truncated to double | |
| 40 | * (unfortunately, it also forces store+load): | |
| 41 | */ | |
| 42 | volatile double w; | |
| 43 | ||
| 7ce331c0 | 44 | EXTRACT_WORDS(i0,i1,x); |
| 4435b3ae | 45 | /* Unbiased exponent */ |
| c61c6d98 | 46 | _j0 = ((((u_int32_t)i0) >> 20)&0x7ff)-0x3ff; |
| 4435b3ae | 47 | |
| c61c6d98 | 48 | if (_j0 > 51) { |
| 4435b3ae | 49 | //Why bother? Just returning x works too |
| c61c6d98 | 50 | //if (_j0 == 0x400) /* inf or NaN */ |
| 4435b3ae DV |
51 | // return x+x; |
| 52 | return x; /* x is integral */ | |
| 53 | } | |
| 54 | ||
| 55 | /* Sign */ | |
| 56 | sx = ((u_int32_t)i0) >> 31; | |
| 57 | ||
| c61c6d98 PM |
58 | if (_j0<20) { |
| 59 | if (_j0<0) { /* |x| < 1 */ | |
| 4435b3ae | 60 | if (((i0&0x7fffffff)|i1)==0) return x; |
| 7ce331c0 EA |
61 | i1 |= (i0&0x0fffff); |
| 62 | i0 &= 0xfffe0000; | |
| 63 | i0 |= ((i1|-i1)>>12)&0x80000; | |
| 64 | SET_HIGH_WORD(x,i0); | |
| 4435b3ae DV |
65 | w = TWO52[sx]+x; |
| 66 | t = w-TWO52[sx]; | |
| 7ce331c0 EA |
67 | GET_HIGH_WORD(i0,t); |
| 68 | SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); | |
| 4435b3ae | 69 | return t; |
| 7ce331c0 | 70 | } else { |
| c61c6d98 | 71 | i = (0x000fffff)>>_j0; |
| 4435b3ae | 72 | if (((i0&i)|i1)==0) return x; /* x is integral */ |
| 7ce331c0 | 73 | i>>=1; |
| 4435b3ae | 74 | if (((i0&i)|i1)!=0) { |
| c61c6d98 PM |
75 | if (_j0==19) i1 = 0x40000000; |
| 76 | else i0 = (i0&(~i))|((0x20000)>>_j0); | |
| 7ce331c0 EA |
77 | } |
| 78 | } | |
| 7ce331c0 | 79 | } else { |
| c61c6d98 | 80 | i = ((u_int32_t)(0xffffffff))>>(_j0-20); |
| 4435b3ae | 81 | if ((i1&i)==0) return x; /* x is integral */ |
| 7ce331c0 | 82 | i>>=1; |
| c61c6d98 | 83 | if ((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(_j0-20)); |
| 7ce331c0 EA |
84 | } |
| 85 | INSERT_WORDS(x,i0,i1); | |
| 86 | w = TWO52[sx]+x; | |
| 87 | return w-TWO52[sx]; | |
| 88 | } | |
| 9cc29786 | 89 | libm_hidden_def(rint) |
| 30bd4a6c DV |
90 | |
| 91 | strong_alias(rint, nearbyint) | |
| 92 | libm_hidden_def(nearbyint) |