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| Rev | Author | Line No. | Line |
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| 3362 | Serge | 1 | |
| 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 | FUNCTION |
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| 14 | < |
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| 15 | INDEX |
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| 16 | rint |
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| 17 | INDEX |
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| 18 | rintf |
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| 19 | |||
| 20 | |||
| 21 | #include |
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| 22 | double rint(double <[x]>); |
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| 23 | float rintf(float <[x]>); |
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| 24 | |||
| 25 | |||
| 26 | The < |
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| 27 | floating-point format, using the current rounding direction. They |
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| 28 | raise the "inexact" floating-point exception if the result differs |
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| 29 | in value from the argument. See the < |
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| 30 | same function with the "inexact" floating-point exception never being |
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| 31 | raised. Newlib does not directly support floating-point exceptions. |
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| 32 | The < |
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| 33 | raised in hardware implementations that support it, even though Newlib |
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| 34 | does not provide access. |
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| 35 | |||
| 36 | |||
| 37 | <[x]> rounded to an integral value, using the current rounding direction. |
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| 38 | |||
| 39 | |||
| 40 | ANSI C, POSIX |
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| 41 | |||
| 42 | |||
| 43 | < |
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| 44 | |||
| 45 | |||
| 46 | |||
| 47 | |||
| 48 | * rint(x) |
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| 49 | * Return x rounded to integral value according to the prevailing |
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| 50 | * rounding mode. |
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| 51 | * Method: |
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| 52 | * Using floating addition. |
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| 53 | * Whenever a fraction is present, if the second or any following bit after |
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| 54 | * the radix point is set, limit to the second radix point to avoid |
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| 55 | * possible double rounding in the TWO52 +- steps (in case guard bits are |
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| 56 | * used). Specifically, if have any, chop off bits past the 2nd place and |
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| 57 | * set the second place. |
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| 58 | * (e.g. 2.0625=0b10.0001 => 0b10.01=2.25; |
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| 59 | * 2.3125=0b10.011 => 0b10.01=2.25; |
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| 60 | * 1.5625= 0b1.1001 => 0b1.11=1.75; |
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| 61 | * 1.9375= 0b1.1111 => 0b1.11=1.75. |
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| 62 | * Pseudo-code: if(x.frac & ~0b0.10) x.frac = (x.frac & 0b0.11) | 0b0.01;). |
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| 63 | * Exception: |
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| 64 | * Inexact flag raised if x not equal to rint(x). |
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| 65 | */ |
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| 66 | |||
| 67 | |||
| 68 | |||
| 69 | |||
| 70 | |||
| 71 | |||
| 72 | static const double |
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| 73 | #else |
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| 74 | static double |
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| 75 | #endif |
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| 76 | TWO52[2]={ |
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| 77 | 4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */ |
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| 78 | -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */ |
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| 79 | }; |
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| 80 | |||
| 81 | |||
| 82 | double rint(double x) |
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| 83 | #else |
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| 84 | double rint(x) |
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| 85 | double x; |
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| 86 | #endif |
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| 87 | { |
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| 88 | __int32_t i0,j0,sx; |
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| 89 | __uint32_t i,i1; |
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| 90 | double t; |
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| 91 | volatile double w; |
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| 92 | EXTRACT_WORDS(i0,i1,x); |
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| 93 | sx = (i0>>31)&1; /* sign */ |
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| 94 | j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent */ |
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| 95 | if(j0<20) { /* no integral bits in LS part */ |
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| 96 | if(j0<0) { /* x is fractional or 0 */ |
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| 97 | if(((i0&0x7fffffff)|i1)==0) return x; /* x == 0 */ |
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| 98 | i1 |= (i0&0x0fffff); |
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| 99 | i0 &= 0xfffe0000; |
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| 100 | i0 |= ((i1|-i1)>>12)&0x80000; |
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| 101 | SET_HIGH_WORD(x,i0); |
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| 102 | w = TWO52[sx]+x; |
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| 103 | t = w-TWO52[sx]; |
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| 104 | GET_HIGH_WORD(i0,t); |
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| 105 | SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31)); |
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| 106 | return t; |
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| 107 | } else { /* x has integer and maybe fraction */ |
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| 108 | i = (0x000fffff)>>j0; |
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| 109 | if(((i0&i)|i1)==0) return x; /* x is integral */ |
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| 110 | i>>=1; |
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| 111 | if(((i0&i)|i1)!=0) { |
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| 112 | /* 2nd or any later bit after radix is set */ |
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| 113 | if(j0==19) i1 = 0x80000000; else i1 = 0; |
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| 114 | i0 = (i0&(~i))|((0x40000)>>j0); |
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| 115 | } |
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| 116 | } |
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| 117 | } else if (j0>51) { |
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| 118 | if(j0==0x400) return x+x; /* inf or NaN */ |
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| 119 | else return x; /* x is integral */ |
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| 120 | } else { |
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| 121 | i = ((__uint32_t)(0xffffffff))>>(j0-20); |
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| 122 | if((i1&i)==0) return x; /* x is integral */ |
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| 123 | i>>=1; |
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| 124 | if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20)); |
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| 125 | } |
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| 126 | INSERT_WORDS(x,i0,i1); |
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| 127 | w = TWO52[sx]+x; |
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| 128 | return w-TWO52[sx]; |
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| 129 | } |
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| 130 | |||
| 131 | |||
| 132 | > |