| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* IEEE754 floating point arithmetic |
| 2 | * double precision: common utilities |
| 3 | */ |
| 4 | /* |
| 5 | * MIPS floating point support |
| 6 | * Copyright (C) 1994-2000 Algorithmics Ltd. |
| 7 | * http://www.algor.co.uk |
| 8 | * |
| 9 | * ######################################################################## |
| 10 | * |
| 11 | * This program is free software; you can distribute it and/or modify it |
| 12 | * under the terms of the GNU General Public License (Version 2) as |
| 13 | * published by the Free Software Foundation. |
| 14 | * |
| 15 | * This program is distributed in the hope it will be useful, but WITHOUT |
| 16 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 17 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 18 | * for more details. |
| 19 | * |
| 20 | * You should have received a copy of the GNU General Public License along |
| 21 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 22 | * 59 Temple Place - Suite 330, Boston MA 02111-1307, USA. |
| 23 | * |
| 24 | * ######################################################################## |
| 25 | */ |
| 26 | |
| 27 | |
| 28 | #include "ieee754dp.h" |
| 29 | |
| 30 | /* modf function is always exact for a finite number |
| 31 | */ |
| 32 | ieee754dp ieee754dp_modf(ieee754dp x, ieee754dp * ip) |
| 33 | { |
| 34 | COMPXDP; |
| 35 | |
| 36 | CLEARCX; |
| 37 | |
| 38 | EXPLODEXDP; |
| 39 | |
| 40 | switch (xc) { |
| 41 | case IEEE754_CLASS_SNAN: |
| 42 | case IEEE754_CLASS_QNAN: |
| 43 | case IEEE754_CLASS_INF: |
| 44 | case IEEE754_CLASS_ZERO: |
| 45 | *ip = x; |
| 46 | return x; |
| 47 | case IEEE754_CLASS_DNORM: |
| 48 | /* far to small */ |
| 49 | *ip = ieee754dp_zero(xs); |
| 50 | return x; |
| 51 | case IEEE754_CLASS_NORM: |
| 52 | break; |
| 53 | } |
| 54 | if (xe < 0) { |
| 55 | *ip = ieee754dp_zero(xs); |
| 56 | return x; |
| 57 | } |
| 58 | if (xe >= DP_MBITS) { |
| 59 | *ip = x; |
| 60 | return ieee754dp_zero(xs); |
| 61 | } |
| 62 | /* generate ipart mantissa by clearing bottom bits |
| 63 | */ |
| 64 | *ip = builddp(xs, xe + DP_EBIAS, |
| 65 | ((xm >> (DP_MBITS - xe)) << (DP_MBITS - xe)) & |
| 66 | ~DP_HIDDEN_BIT); |
| 67 | |
| 68 | /* generate fpart mantissa by clearing top bits |
| 69 | * and normalizing (must be able to normalize) |
| 70 | */ |
| 71 | xm = (xm << (64 - (DP_MBITS - xe))) >> (64 - (DP_MBITS - xe)); |
| 72 | if (xm == 0) |
| 73 | return ieee754dp_zero(xs); |
| 74 | |
| 75 | while ((xm >> DP_MBITS) == 0) { |
| 76 | xm <<= 1; |
| 77 | xe--; |
| 78 | } |
| 79 | return builddp(xs, xe + DP_EBIAS, xm & ~DP_HIDDEN_BIT); |
| 80 | } |