| yuezonghe | 824eb0c | 2024-06-27 02:32:26 -0700 | [diff] [blame^] | 1 | /* |
| 2 | ** libgcc support for software floating point. |
| 3 | ** Copyright (C) 1991 by Pipeline Associates, Inc. All rights reserved. |
| 4 | ** Permission is granted to do *anything* you want with this file, |
| 5 | ** commercial or otherwise, provided this message remains intact. So there! |
| 6 | ** I would appreciate receiving any updates/patches/changes that anyone |
| 7 | ** makes, and am willing to be the repository for said changes (am I |
| 8 | ** making a big mistake?). |
| 9 | |
| 10 | Warning! Only single-precision is actually implemented. This file |
| 11 | won't really be much use until double-precision is supported. |
| 12 | |
| 13 | However, once that is done, this file might eventually become a |
| 14 | replacement for libgcc1.c. It might also make possible |
| 15 | cross-compilation for an IEEE target machine from a non-IEEE |
| 16 | host such as a VAX. |
| 17 | |
| 18 | If you'd like to work on completing this, please talk to rms@gnu.ai.mit.edu. |
| 19 | |
| 20 | --> Double precision floating support added by James Carlson on 20 April 1998. |
| 21 | |
| 22 | ** |
| 23 | ** Pat Wood |
| 24 | ** Pipeline Associates, Inc. |
| 25 | ** pipeline!phw@motown.com or |
| 26 | ** sun!pipeline!phw or |
| 27 | ** uunet!motown!pipeline!phw |
| 28 | ** |
| 29 | ** 05/01/91 -- V1.0 -- first release to gcc mailing lists |
| 30 | ** 05/04/91 -- V1.1 -- added float and double prototypes and return values |
| 31 | ** -- fixed problems with adding and subtracting zero |
| 32 | ** -- fixed rounding in truncdfsf2 |
| 33 | ** -- fixed SWAP define and tested on 386 |
| 34 | */ |
| 35 | |
| 36 | /* |
| 37 | ** The following are routines that replace the libgcc soft floating point |
| 38 | ** routines that are called automatically when -msoft-float is selected. |
| 39 | ** The support single and double precision IEEE format, with provisions |
| 40 | ** for byte-swapped machines (tested on 386). Some of the double-precision |
| 41 | ** routines work at full precision, but most of the hard ones simply punt |
| 42 | ** and call the single precision routines, producing a loss of accuracy. |
| 43 | ** long long support is not assumed or included. |
| 44 | ** Overall accuracy is close to IEEE (actually 68882) for single-precision |
| 45 | ** arithmetic. I think there may still be a 1 in 1000 chance of a bit |
| 46 | ** being rounded the wrong way during a multiply. I'm not fussy enough to |
| 47 | ** bother with it, but if anyone is, knock yourself out. |
| 48 | ** |
| 49 | ** Efficiency has only been addressed where it was obvious that something |
| 50 | ** would make a big difference. Anyone who wants to do this right for |
| 51 | ** best speed should go in and rewrite in assembler. |
| 52 | ** |
| 53 | ** I have tested this only on a 68030 workstation and 386/ix integrated |
| 54 | ** in with -msoft-float. |
| 55 | */ |
| 56 | |
| 57 | #include "floatlib.h" |
| 58 | |
| 59 | /* convert double to int */ |
| 60 | long |
| 61 | __fixdfsi (double a1) |
| 62 | { |
| 63 | register union double_long dl1; |
| 64 | register int exp; |
| 65 | register long l; |
| 66 | |
| 67 | dl1.d = a1; |
| 68 | |
| 69 | if (!dl1.l.upper && !dl1.l.lower) |
| 70 | return (0); |
| 71 | |
| 72 | exp = EXPD (dl1) - EXCESSD - 31; |
| 73 | l = MANTD (dl1); |
| 74 | |
| 75 | if (exp > 0) |
| 76 | return SIGND(dl1) ? (1<<31) : ((1ul<<31)-1); |
| 77 | |
| 78 | /* shift down until exp = 0 or l = 0 */ |
| 79 | if (exp < 0 && exp > -32 && l) |
| 80 | l >>= -exp; |
| 81 | else |
| 82 | return (0); |
| 83 | |
| 84 | return (SIGND (dl1) ? -l : l); |
| 85 | } |