add directory gnu
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gohigh
581
gnu/gcc/gcc-2.2.2/floatlib.c
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581
gnu/gcc/gcc-2.2.2/floatlib.c
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/*
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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 0x80000000
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#define HIDDEN (1 << 23)
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#define SIGN(fp) ((fp) & SIGNBIT)
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#define EXP(fp) (((fp) >> 23) & 0xFF)
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#define MANT(fp) (((fp) & 0x7FFFFF) | HIDDEN)
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#define PACK(s,e,m) ((s) | ((e) << 23) | (m))
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/* the following deal with IEEE double-precision numbers */
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#define EXCESSD 1022
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#define HIDDEND (1 << 20)
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#define EXPD(fp) (((fp.l.upper) >> 20) & 0x7FF)
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#define SIGND(fp) ((fp.l.upper) & SIGNBIT)
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#define MANTD(fp) (((((fp.l.upper) & 0xFFFFF) | HIDDEND) << 10) | \
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(fp.l.lower >> 22))
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/* define SWAP for 386/960 reverse-byte-order brain-damaged CPUs */
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union double_long
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{
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double d;
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#ifdef SWAP
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struct {
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unsigned long lower;
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long upper;
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} l;
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#else
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struct {
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long upper;
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unsigned long lower;
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} l;
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#endif
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};
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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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/* add two floats */
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float
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__addsf3 (float a1, float a2)
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{
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register long mant1, mant2;
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register union float_long fl1, fl2;
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register int exp1, exp2;
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int sign = 0;
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fl1.f = a1;
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fl2.f = a2;
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/* check for zero args */
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if (!fl1.l)
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return (fl2.f);
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if (!fl2.l)
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return (fl1.f);
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exp1 = EXP (fl1.l);
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exp2 = EXP (fl2.l);
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if (exp1 > exp2 + 25)
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return (fl1.l);
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if (exp2 > exp1 + 25)
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return (fl2.l);
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/* do everything in excess precision so's we can round later */
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mant1 = MANT (fl1.l) << 6;
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mant2 = MANT (fl2.l) << 6;
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if (SIGN (fl1.l))
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mant1 = -mant1;
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if (SIGN (fl2.l))
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mant2 = -mant2;
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if (exp1 > exp2)
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{
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mant2 >>= exp1 - exp2;
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}
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else
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{
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mant1 >>= exp2 - exp1;
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exp1 = exp2;
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}
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mant1 += mant2;
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if (mant1 < 0)
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{
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mant1 = -mant1;
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sign = SIGNBIT;
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}
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else if (!mant1)
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return (0);
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/* normalize up */
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while (!(mant1 & 0xE0000000))
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{
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mant1 <<= 1;
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exp1--;
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}
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/* normalize down? */
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if (mant1 & (1 << 30))
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{
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mant1 >>= 1;
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exp1++;
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}
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/* round to even */
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mant1 += (mant1 & 0x40) ? 0x20 : 0x1F;
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/* normalize down? */
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if (mant1 & (1 << 30))
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{
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mant1 >>= 1;
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exp1++;
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}
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/* lose extra precision */
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mant1 >>= 6;
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/* turn off hidden bit */
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mant1 &= ~HIDDEN;
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/* pack up and go home */
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fl1.l = PACK (sign, exp1, mant1);
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return (fl1.f);
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}
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/* subtract two floats */
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float
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__subsf3 (float a1, float a2)
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{
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register union float_long fl1, fl2;
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fl1.f = a1;
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fl2.f = a2;
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||||
|
||||
/* check for zero args */
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||||
if (!fl2.l)
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return (fl1.f);
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if (!fl1.l)
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return (-fl2.f);
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/* twiddle sign bit and add */
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fl2.l ^= SIGNBIT;
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return __addsf3 (a1, fl2.f);
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}
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|
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/* compare two floats */
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long
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__cmpsf2 (float a1, float a2)
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{
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register union float_long fl1, fl2;
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fl1.f = a1;
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fl2.f = a2;
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||||
|
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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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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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/* multiply two floats */
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float
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__mulsf3 (float a1, float a2)
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{
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register union float_long fl1, fl2;
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register unsigned long result;
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register int exp;
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int sign;
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fl1.f = a1;
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fl2.f = a2;
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if (!fl1.l || !fl2.l)
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return (0);
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/* compute sign and exponent */
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sign = SIGN (fl1.l) ^ SIGN (fl2.l);
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exp = EXP (fl1.l) - EXCESS;
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exp += EXP (fl2.l);
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fl1.l = MANT (fl1.l);
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fl2.l = MANT (fl2.l);
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/* the multiply is done as one 16x16 multiply and two 16x8 multiples */
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result = (fl1.l >> 8) * (fl2.l >> 8);
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result += ((fl1.l & 0xFF) * (fl2.l >> 8)) >> 8;
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result += ((fl2.l & 0xFF) * (fl1.l >> 8)) >> 8;
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if (result & 0x80000000)
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{
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/* round */
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result += 0x80;
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result >>= 8;
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}
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else
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{
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/* round */
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result += 0x40;
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result >>= 7;
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exp--;
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}
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result &= ~HIDDEN;
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/* pack up and go home */
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fl1.l = PACK (sign, exp, result);
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return (fl1.f);
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}
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/* divide two floats */
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float
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__divsf3 (float a1, float a2)
|
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{
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register union float_long fl1, fl2;
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register int result;
|
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register int mask;
|
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register int exp, sign;
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fl1.f = a1;
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fl2.f = a2;
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/* subtract exponents */
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exp = EXP (fl1.l) - EXP (fl2.l) + EXCESS;
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/* compute sign */
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sign = SIGN (fl1.l) ^ SIGN (fl2.l);
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/* divide by zero??? */
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if (!fl2.l)
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/* return NaN or -NaN */
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return (sign ? 0xFFFFFFFF : 0x7FFFFFFF);
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||||
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||||
/* numerator zero??? */
|
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if (!fl1.l)
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return (0);
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/* now get mantissas */
|
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fl1.l = MANT (fl1.l);
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fl2.l = MANT (fl2.l);
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|
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/* this assures we have 25 bits of precision in the end */
|
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if (fl1.l < fl2.l)
|
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{
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fl1.l <<= 1;
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exp--;
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}
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||||
|
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/* now we perform repeated subtraction of fl2.l from fl1.l */
|
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mask = 0x1000000;
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||||
result = 0;
|
||||
while (mask)
|
||||
{
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||||
if (fl1.l >= fl2.l)
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{
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result |= mask;
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fl1.l -= fl2.l;
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}
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fl1.l <<= 1;
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mask >>= 1;
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}
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/* round */
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result += 1;
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||||
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/* normalize down */
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||||
exp++;
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result >>= 1;
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||||
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result &= ~HIDDEN;
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||||
|
||||
/* pack up and go home */
|
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fl1.l = PACK (sign, exp, result);
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return (fl1.f);
|
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}
|
||||
|
||||
/* convert int to double */
|
||||
double
|
||||
__floatsidf (register long a1)
|
||||
{
|
||||
register int sign = 0, exp = 31 + EXCESSD;
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||||
union double_long dl;
|
||||
|
||||
if (!a1)
|
||||
{
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||||
dl.l.upper = dl.l.lower = 0;
|
||||
return (dl.d);
|
||||
}
|
||||
|
||||
if (a1 < 0)
|
||||
{
|
||||
sign = SIGNBIT;
|
||||
a1 = -a1;
|
||||
}
|
||||
|
||||
while (a1 < 0x1000000)
|
||||
{
|
||||
a1 <<= 4;
|
||||
exp -= 4;
|
||||
}
|
||||
|
||||
while (a1 < 0x40000000)
|
||||
{
|
||||
a1 <<= 1;
|
||||
exp--;
|
||||
}
|
||||
|
||||
/* pack up and go home */
|
||||
dl.l.upper = sign;
|
||||
dl.l.upper |= exp << 20;
|
||||
dl.l.upper |= (a1 >> 10) & ~HIDDEND;
|
||||
dl.l.lower = a1 << 22;
|
||||
|
||||
return (dl.d);
|
||||
}
|
||||
|
||||
/* negate a float */
|
||||
float
|
||||
__negsf2 (float a1)
|
||||
{
|
||||
register union float_long fl1;
|
||||
|
||||
fl1.f = a1;
|
||||
if (!fl1.l)
|
||||
return (0);
|
||||
|
||||
fl1.l ^= SIGNBIT;
|
||||
return (fl1.f);
|
||||
}
|
||||
|
||||
/* negate a double */
|
||||
double
|
||||
__negdf2 (double a1)
|
||||
{
|
||||
register union double_long dl1;
|
||||
|
||||
dl1.d = a1;
|
||||
|
||||
if (!dl1.l.upper && !dl1.l.lower)
|
||||
return (dl1.d);
|
||||
|
||||
dl1.l.upper ^= SIGNBIT;
|
||||
return (dl1.d);
|
||||
}
|
||||
|
||||
/* convert float to double */
|
||||
double
|
||||
__extendsfdf2 (float a1)
|
||||
{
|
||||
register union float_long fl1;
|
||||
register union double_long dl;
|
||||
register int exp;
|
||||
|
||||
fl1.f = a1;
|
||||
|
||||
if (!fl1.l)
|
||||
{
|
||||
dl.l.upper = dl.l.lower = 0;
|
||||
return (dl.d);
|
||||
}
|
||||
|
||||
dl.l.upper = SIGN (fl1.l);
|
||||
exp = EXP (fl1.l) - EXCESS + EXCESSD;
|
||||
dl.l.upper |= exp << 20;
|
||||
dl.l.upper |= (MANT (fl1.l) & ~HIDDEN) >> 3;
|
||||
dl.l.lower = MANT (fl1.l) << 29;
|
||||
|
||||
return (dl.d);
|
||||
}
|
||||
|
||||
/* convert double to float */
|
||||
float
|
||||
__truncdfsf2 (double a1)
|
||||
{
|
||||
register int exp;
|
||||
register long mant;
|
||||
register union float_long fl;
|
||||
register union double_long dl1;
|
||||
|
||||
dl1.d = a1;
|
||||
|
||||
if (!dl1.l.upper && !dl1.l.lower)
|
||||
return (0);
|
||||
|
||||
exp = EXPD (dl1) - EXCESSD + EXCESS;
|
||||
|
||||
/* shift double mantissa 6 bits so we can round */
|
||||
mant = MANTD (dl1) >> 6;
|
||||
|
||||
/* now round and shift down */
|
||||
mant += 1;
|
||||
mant >>= 1;
|
||||
|
||||
/* did the round overflow? */
|
||||
if (mant & 0xFF000000)
|
||||
{
|
||||
mant >>= 1;
|
||||
exp++;
|
||||
}
|
||||
|
||||
mant &= ~HIDDEN;
|
||||
|
||||
/* pack up and go home */
|
||||
fl.l = PACK (SIGND (dl1), exp, mant);
|
||||
return (fl.f);
|
||||
}
|
||||
|
||||
/* compare two doubles */
|
||||
long
|
||||
__cmpdf2 (double a1, double a2)
|
||||
{
|
||||
register union double_long dl1, dl2;
|
||||
|
||||
dl1.d = a1;
|
||||
dl2.d = a2;
|
||||
|
||||
if (SIGND (dl1) && SIGND (dl2))
|
||||
{
|
||||
dl1.l.upper ^= SIGNBIT;
|
||||
dl2.l.upper ^= SIGNBIT;
|
||||
}
|
||||
if (dl1.l.upper < dl2.l.upper)
|
||||
return (-1);
|
||||
if (dl1.l.upper > dl2.l.upper)
|
||||
return (1);
|
||||
if (dl1.l.lower < dl2.l.lower)
|
||||
return (-1);
|
||||
if (dl1.l.lower > dl2.l.lower)
|
||||
return (1);
|
||||
return (0);
|
||||
}
|
||||
|
||||
/* convert double to int */
|
||||
long
|
||||
__fixdfsi (double a1)
|
||||
{
|
||||
register union double_long dl1;
|
||||
register int exp;
|
||||
register long l;
|
||||
|
||||
dl1.d = a1;
|
||||
|
||||
if (!dl1.l.upper && !dl1.l.lower)
|
||||
return (0);
|
||||
|
||||
exp = EXPD (dl1) - EXCESSD - 31;
|
||||
l = MANTD (dl1);
|
||||
|
||||
if (exp > 0)
|
||||
return (0x7FFFFFFF | SIGND (dl1)); /* largest integer */
|
||||
|
||||
/* shift down until exp = 0 or l = 0 */
|
||||
if (exp < 0 && exp > -32 && l)
|
||||
l >>= -exp;
|
||||
else
|
||||
return (0);
|
||||
|
||||
return (SIGND (dl1) ? -l : l);
|
||||
}
|
||||
|
||||
/* convert double to unsigned int */
|
||||
unsigned
|
||||
long __fixunsdfsi (double a1)
|
||||
{
|
||||
register union double_long dl1;
|
||||
register int exp;
|
||||
register unsigned long l;
|
||||
|
||||
dl1.d = a1;
|
||||
|
||||
if (!dl1.l.upper && !dl1.l.lower)
|
||||
return (0);
|
||||
|
||||
exp = EXPD (dl1) - EXCESSD - 32;
|
||||
l = (((((dl1.l.upper) & 0xFFFFF) | HIDDEND) << 11) | (dl1.l.lower >> 21));
|
||||
|
||||
if (exp > 0)
|
||||
return (0xFFFFFFFF); /* largest integer */
|
||||
|
||||
/* shift down until exp = 0 or l = 0 */
|
||||
if (exp < 0 && exp > -32 && l)
|
||||
l >>= -exp;
|
||||
else
|
||||
return (0);
|
||||
|
||||
return (l);
|
||||
}
|
||||
|
||||
/* For now, the hard double-precision routines simply
|
||||
punt and do it in single */
|
||||
/* addtwo doubles */
|
||||
double
|
||||
__adddf3 (double a1, double a2)
|
||||
{
|
||||
return ((float) a1 + (float) a2);
|
||||
}
|
||||
|
||||
/* subtract two doubles */
|
||||
double
|
||||
__subdf3 (double a1, double a2)
|
||||
{
|
||||
return ((float) a1 - (float) a2);
|
||||
}
|
||||
|
||||
/* multiply two doubles */
|
||||
double
|
||||
__muldf3 (double a1, double a2)
|
||||
{
|
||||
return ((float) a1 * (float) a2);
|
||||
}
|
||||
|
||||
/* divide two doubles */
|
||||
double
|
||||
__divdf3 (double a1, double a2)
|
||||
{
|
||||
return ((float) a1 / (float) a2);
|
||||
}
|
||||
Reference in New Issue
Block a user