| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame^] | 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 |
| 7 | * software is freely granted, provided that this notice |
| 8 | * is preserved. |
| 9 | * ==================================================== |
| 10 | */ |
| 11 | |
| 12 | /* |
| 13 | * double logb(x) |
| 14 | * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
| 15 | * Use ilogb instead. |
| 16 | */ |
| 17 | |
| 18 | #include "math.h" |
| 19 | #include "math_private.h" |
| 20 | |
| 21 | double logb(double x) |
| 22 | { |
| 23 | int32_t lx,ix; |
| 24 | EXTRACT_WORDS(ix,lx,x); |
| 25 | ix &= 0x7fffffff; /* high |x| */ |
| 26 | if((ix|lx)==0) return -1.0/fabs(x); |
| 27 | if(ix>=0x7ff00000) return x*x; |
| 28 | if((ix>>=20)==0) /* IEEE 754 logb */ |
| 29 | return -1022.0; |
| 30 | else |
| 31 | return (double) (ix-1023); |
| 32 | } |
| 33 | libm_hidden_def(logb) |