| 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 | s64 ieee754dp_tlong(ieee754dp x) |
| 31 | { |
| 32 | COMPXDP; |
| 33 | |
| 34 | CLEARCX; |
| 35 | |
| 36 | EXPLODEXDP; |
| 37 | FLUSHXDP; |
| 38 | |
| 39 | switch (xc) { |
| 40 | case IEEE754_CLASS_SNAN: |
| 41 | case IEEE754_CLASS_QNAN: |
| 42 | case IEEE754_CLASS_INF: |
| 43 | SETCX(IEEE754_INVALID_OPERATION); |
| 44 | return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x); |
| 45 | case IEEE754_CLASS_ZERO: |
| 46 | return 0; |
| 47 | case IEEE754_CLASS_DNORM: |
| 48 | case IEEE754_CLASS_NORM: |
| 49 | break; |
| 50 | } |
| 51 | if (xe >= 63) { |
| 52 | /* look for valid corner case */ |
| 53 | if (xe == 63 && xs && xm == DP_HIDDEN_BIT) |
| 54 | return -0x8000000000000000LL; |
| 55 | /* Set invalid. We will only use overflow for floating |
| 56 | point overflow */ |
| 57 | SETCX(IEEE754_INVALID_OPERATION); |
| 58 | return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x); |
| 59 | } |
| 60 | /* oh gawd */ |
| 61 | if (xe > DP_MBITS) { |
| 62 | xm <<= xe - DP_MBITS; |
| 63 | } else if (xe < DP_MBITS) { |
| 64 | u64 residue; |
| 65 | int round; |
| 66 | int sticky; |
| 67 | int odd; |
| 68 | |
| 69 | if (xe < -1) { |
| 70 | residue = xm; |
| 71 | round = 0; |
| 72 | sticky = residue != 0; |
| 73 | xm = 0; |
| 74 | } |
| 75 | else { |
| 76 | /* Shifting a u64 64 times does not work, |
| 77 | * so we do it in two steps. Be aware that xe |
| 78 | * may be -1 */ |
| 79 | residue = xm << (xe + 1); |
| 80 | residue <<= 63 - DP_MBITS; |
| 81 | round = (residue >> 63) != 0; |
| 82 | sticky = (residue << 1) != 0; |
| 83 | xm >>= DP_MBITS - xe; |
| 84 | } |
| 85 | odd = (xm & 0x1) != 0x0; |
| 86 | switch (ieee754_csr.rm) { |
| 87 | case IEEE754_RN: |
| 88 | if (round && (sticky || odd)) |
| 89 | xm++; |
| 90 | break; |
| 91 | case IEEE754_RZ: |
| 92 | break; |
| 93 | case IEEE754_RU: /* toward +Infinity */ |
| 94 | if ((round || sticky) && !xs) |
| 95 | xm++; |
| 96 | break; |
| 97 | case IEEE754_RD: /* toward -Infinity */ |
| 98 | if ((round || sticky) && xs) |
| 99 | xm++; |
| 100 | break; |
| 101 | } |
| 102 | if ((xm >> 63) != 0) { |
| 103 | /* This can happen after rounding */ |
| 104 | SETCX(IEEE754_INVALID_OPERATION); |
| 105 | return ieee754di_xcpt(ieee754di_indef(), "dp_tlong", x); |
| 106 | } |
| 107 | if (round || sticky) |
| 108 | SETCX(IEEE754_INEXACT); |
| 109 | } |
| 110 | if (xs) |
| 111 | return -xm; |
| 112 | else |
| 113 | return xm; |
| 114 | } |
| 115 | |
| 116 | |
| 117 | u64 ieee754dp_tulong(ieee754dp x) |
| 118 | { |
| 119 | ieee754dp hb = ieee754dp_1e63(); |
| 120 | |
| 121 | /* what if x < 0 ?? */ |
| 122 | if (ieee754dp_lt(x, hb)) |
| 123 | return (u64) ieee754dp_tlong(x); |
| 124 | |
| 125 | return (u64) ieee754dp_tlong(ieee754dp_sub(x, hb)) | |
| 126 | (1ULL << 63); |
| 127 | } |