** libgcc support for software floating point.
** Copyright (C) 1991 by Pipeline Associates, Inc. All rights reserved.
** Permission is granted to do *anything* you want with this file,
** commercial or otherwise, provided this message remains intact. So there!
** I would appreciate receiving any updates/patches/changes that anyone
** makes, and am willing to be the repository for said changes (am I
** making a big mistake?).
Warning! Only single-precision is actually implemented. This file
won't really be much use until double-precision is supported.
However, once that is done, this file might eventually become a
replacement for libgcc1.c. It might also make possible
cross-compilation for an IEEE target machine from a non-IEEE
If you'd like to work on completing this, please talk to rms@gnu.ai.mit.edu.
** Pipeline Associates, Inc.
** pipeline!phw@motown.com or
** uunet!motown!pipeline!phw
** 05/01/91 -- V1.0 -- first release to gcc mailing lists
** 05/04/91 -- V1.1 -- added float and double prototypes and return values
** -- fixed problems with adding and subtracting zero
** -- fixed rounding in truncdfsf2
** -- fixed SWAP define and tested on 386
** The following are routines that replace the libgcc soft floating point
** routines that are called automatically when -msoft-float is selected.
** The support single and double precision IEEE format, with provisions
** for byte-swapped machines (tested on 386). Some of the double-precision
** routines work at full precision, but most of the hard ones simply punt
** and call the single precision routines, producing a loss of accuracy.
** long long support is not assumed or included.
** Overall accuracy is close to IEEE (actually 68882) for single-precision
** arithmetic. I think there may still be a 1 in 1000 chance of a bit
** being rounded the wrong way during a multiply. I'm not fussy enough to
** bother with it, but if anyone is, knock yourself out.
** Efficiency has only been addressed where it was obvious that something
** would make a big difference. Anyone who wants to do this right for
** best speed should go in and rewrite in assembler.
** I have tested this only on a 68030 workstation and 386/ix integrated
/* the following deal with IEEE single-precision numbers */
#define SIGNBIT 0x80000000
#define SIGN(fp) ((fp) & SIGNBIT)
#define EXP(fp) (((fp) >> 23) & 0xFF)
#define MANT(fp) (((fp) & 0x7FFFFF) | HIDDEN)
#define PACK(s,e,m) ((s) | ((e) << 23) | (m))
/* the following deal with IEEE double-precision numbers */
#define HIDDEND (1 << 20)
#define EXPD(fp) (((fp.l.upper) >> 20) & 0x7FF)
#define SIGND(fp) ((fp.l.upper) & SIGNBIT)
#define MANTD(fp) (((((fp.l.upper) & 0xFFFFF) | HIDDEND) << 10) | \
/* define SWAP for 386/960 reverse-byte-order brain-damaged CPUs */
__addsf3 (float a1
, float a2
)
register long mant1
, mant2
;
register union float_long fl1
, fl2
;
/* check for zero args */
/* do everything in excess precision so's we can round later */
mant1
= MANT (fl1
.l
) << 6;
mant2
= MANT (fl2
.l
) << 6;
while (!(mant1
& 0xE0000000))
mant1
+= (mant1
& 0x40) ? 0x20 : 0x1F;
/* lose extra precision */
/* turn off hidden bit */
/* pack up and go home */
fl1
.l
= PACK (sign
, exp1
, mant1
);
/* subtract two floats */
__subsf3 (float a1
, float a2
)
register union float_long fl1
, fl2
;
/* check for zero args */
/* twiddle sign bit and add */
return __addsf3 (a1
, fl2
.f
);
__cmpsf2 (float a1
, float a2
)
register union float_long fl1
, fl2
;
if (SIGN (fl1
.l
) && SIGN (fl2
.l
))
/* multiply two floats */
__mulsf3 (float a1
, float a2
)
register union float_long fl1
, fl2
;
register unsigned long result
;
/* compute sign and exponent */
sign
= SIGN (fl1
.l
) ^ SIGN (fl2
.l
);
exp
= EXP (fl1
.l
) - EXCESS
;
/* the multiply is done as one 16x16 multiply and two 16x8 multiples */
result
= (fl1
.l
>> 8) * (fl2
.l
>> 8);
result
+= ((fl1
.l
& 0xFF) * (fl2
.l
>> 8)) >> 8;
result
+= ((fl2
.l
& 0xFF) * (fl1
.l
>> 8)) >> 8;
/* pack up and go home */
fl1
.l
= PACK (sign
, exp
, result
);
__divsf3 (float a1
, float a2
)
register union float_long fl1
, fl2
;
exp
= EXP (fl1
.l
) - EXP (fl2
.l
) + EXCESS
;
sign
= SIGN (fl1
.l
) ^ SIGN (fl2
.l
);
return (sign
? 0xFFFFFFFF : 0x7FFFFFFF);
/* this assures we have 25 bits of precision in the end */
/* now we perform repeated subtraction of fl2.l from fl1.l */
/* pack up and go home */
fl1
.l
= PACK (sign
, exp
, result
);
/* convert int to double */
__floatsidf (register long a1
)
register int sign
= 0, exp
= 31 + EXCESSD
;
dl
.l
.upper
= dl
.l
.lower
= 0;
/* pack up and go home */
dl
.l
.upper
|= (a1
>> 10) & ~HIDDEND
;
register union float_long fl1
;
register union double_long dl1
;
if (!dl1
.l
.upper
&& !dl1
.l
.lower
)
/* convert float to double */
register union float_long fl1
;
register union double_long dl
;
dl
.l
.upper
= dl
.l
.lower
= 0;
dl
.l
.upper
= SIGN (fl1
.l
);
exp
= EXP (fl1
.l
) - EXCESS
+ EXCESSD
;
dl
.l
.upper
|= (MANT (fl1
.l
) & ~HIDDEN
) >> 3;
dl
.l
.lower
= MANT (fl1
.l
) << 29;
/* convert double to float */
register union float_long fl
;
register union double_long dl1
;
if (!dl1
.l
.upper
&& !dl1
.l
.lower
)
exp
= EXPD (dl1
) - EXCESSD
+ EXCESS
;
/* shift double mantissa 6 bits so we can round */
/* now round and shift down */
/* did the round overflow? */
/* pack up and go home */
fl
.l
= PACK (SIGND (dl1
), exp
, mant
);
/* compare two doubles */
__cmpdf2 (double a1
, double a2
)
register union double_long dl1
, dl2
;
if (SIGND (dl1
) && SIGND (dl2
))
if (dl1
.l
.upper
< dl2
.l
.upper
)
if (dl1
.l
.upper
> dl2
.l
.upper
)
if (dl1
.l
.lower
< dl2
.l
.lower
)
if (dl1
.l
.lower
> dl2
.l
.lower
)
/* convert double to int */
register union double_long dl1
;
if (!dl1
.l
.upper
&& !dl1
.l
.lower
)
exp
= EXPD (dl1
) - EXCESSD
- 31;
return (0x7FFFFFFF | SIGND (dl1
)); /* largest integer */
/* shift down until exp = 0 or l = 0 */
if (exp
< 0 && exp
> -32 && l
)
return (SIGND (dl1
) ? -l
: l
);
/* convert double to unsigned int */
long __fixunsdfsi (double a1
)
register union double_long dl1
;
register unsigned long l
;
if (!dl1
.l
.upper
&& !dl1
.l
.lower
)
exp
= EXPD (dl1
) - EXCESSD
- 32;
l
= (((((dl1
.l
.upper
) & 0xFFFFF) | HIDDEND
) << 11) | (dl1
.l
.lower
>> 21));
return (0xFFFFFFFF); /* largest integer */
/* shift down until exp = 0 or l = 0 */
if (exp
< 0 && exp
> -32 && l
)
/* For now, the hard double-precision routines simply
punt and do it in single */
__adddf3 (double a1
, double a2
)
return ((float) a1
+ (float) a2
);
/* subtract two doubles */
__subdf3 (double a1
, double a2
)
return ((float) a1
- (float) a2
);
/* multiply two doubles */
__muldf3 (double a1
, double a2
)
return ((float) a1
* (float) a2
);
__divdf3 (double a1
, double a2
)
return ((float) a1
/ (float) a2
);