89 lines
3 KiB
C
89 lines
3 KiB
C
/*
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** libgcc support for software floating point.
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** Copyright (C) 1991 by Pipeline Associates, Inc. All rights reserved.
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** Permission is granted to do *anything* you want with this file,
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** commercial or otherwise, provided this message remains intact. So there!
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** I would appreciate receiving any updates/patches/changes that anyone
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** makes, and am willing to be the repository for said changes (am I
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** making a big mistake?).
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Warning! Only single-precision is actually implemented. This file
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won't really be much use until double-precision is supported.
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However, once that is done, this file might eventually become a
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replacement for libgcc1.c. It might also make possible
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cross-compilation for an IEEE target machine from a non-IEEE
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host such as a VAX.
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If you'd like to work on completing this, please talk to rms@gnu.ai.mit.edu.
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**
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** Pat Wood
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** Pipeline Associates, Inc.
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** pipeline!phw@motown.com or
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** sun!pipeline!phw or
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** uunet!motown!pipeline!phw
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**
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** 05/01/91 -- V1.0 -- first release to gcc mailing lists
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** 05/04/91 -- V1.1 -- added float and double prototypes and return values
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** -- fixed problems with adding and subtracting zero
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** -- fixed rounding in truncdfsf2
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** -- fixed SWAP define and tested on 386
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*/
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/*
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** The following are routines that replace the libgcc soft floating point
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** routines that are called automatically when -msoft-float is selected.
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** The support single and double precision IEEE format, with provisions
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** for byte-swapped machines (tested on 386). Some of the double-precision
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** routines work at full precision, but most of the hard ones simply punt
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** and call the single precision routines, producing a loss of accuracy.
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** long long support is not assumed or included.
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** Overall accuracy is close to IEEE (actually 68882) for single-precision
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** arithmetic. I think there may still be a 1 in 1000 chance of a bit
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** being rounded the wrong way during a multiply. I'm not fussy enough to
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** bother with it, but if anyone is, knock yourself out.
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**
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** Efficiency has only been addressed where it was obvious that something
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** would make a big difference. Anyone who wants to do this right for
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** best speed should go in and rewrite in assembler.
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**
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** I have tested this only on a 68030 workstation and 386/ix integrated
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** in with -msoft-float.
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*/
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/* the following deal with IEEE single-precision numbers */
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#define EXCESS 126
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#define SIGNBIT ((unsigned long)0x80000000)
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#define HIDDEN (unsigned long)(1 << 23)
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#define SIGN(fp) ((fp >> (8*sizeof(fp)-1)) & 1)
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#define EXP(fp) (((fp) >> 23) & (unsigned int) 0x00FF)
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#define MANT(fp) (((fp) & (unsigned long) 0x007FFFFF) | HIDDEN)
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#define PACK(s,e,m) ((s) | ((e) << 23) | (m))
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union float_long
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{
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float f;
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long l;
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};
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/* compare two floats */
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char
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__fsgt (float a1, float a2)
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{
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volatile union float_long fl1, fl2;
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fl1.f = a1;
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fl2.f = a2;
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if (SIGN (fl1.l) && SIGN (fl2.l))
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{
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fl1.l ^= SIGNBIT;
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fl2.l ^= SIGNBIT;
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}
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if (fl1.l > fl2.l)
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return (1);
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return (0);
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}
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