101 lines
2.7 KiB
C
101 lines
2.7 KiB
C
/*---------------------------------------------------------------------------+
|
|
| reg_u_mul.c |
|
|
| $Id: reg_u_mul.c,v 1.5 2003-05-15 16:11:29 sshwarts Exp $
|
|
| |
|
|
| Core multiplication routine |
|
|
| |
|
|
| Copyright (C) 1992,1993,1995,1997,1999 |
|
|
| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
|
|
| E-mail billm@melbpc.org.au |
|
|
| |
|
|
| |
|
|
+---------------------------------------------------------------------------*/
|
|
|
|
/*---------------------------------------------------------------------------+
|
|
| Basic multiplication routine. |
|
|
| Does not check the resulting exponent for overflow/underflow |
|
|
| |
|
|
| Internal working is at approx 128 bits. |
|
|
| Result is rounded to nearest 53 or 64 bits, using "nearest or even". |
|
|
+---------------------------------------------------------------------------*/
|
|
|
|
#include "exception.h"
|
|
#include "fpu_emu.h"
|
|
#include "control_w.h"
|
|
|
|
|
|
int FPU_u_mul(const FPU_REG *a, const FPU_REG *b, FPU_REG *c, u16 cw,
|
|
u_char sign, int expon)
|
|
{
|
|
u64 mu, ml, mi;
|
|
u32 lh, ll, th, tl;
|
|
|
|
#ifdef PARANOID
|
|
if (! (a->sigh & 0x80000000) || ! (b->sigh & 0x80000000))
|
|
{
|
|
EXCEPTION(EX_INTERNAL|0x205);
|
|
}
|
|
#endif
|
|
|
|
ml = a->sigl;
|
|
ml *= b->sigl;
|
|
ll = ml;
|
|
lh = ml >> 32;
|
|
|
|
mu = a->sigh;
|
|
mu *= b->sigh;
|
|
|
|
mi = a->sigh;
|
|
mi *= b->sigl;
|
|
tl = mi;
|
|
th = mi >> 32;
|
|
lh += tl;
|
|
if (tl > lh)
|
|
mu ++;
|
|
mu += th;
|
|
|
|
mi = a->sigl;
|
|
mi *= b->sigh;
|
|
tl = mi;
|
|
th = mi >> 32;
|
|
lh += tl;
|
|
if (tl > lh)
|
|
mu ++;
|
|
mu += th;
|
|
|
|
ml = lh;
|
|
ml <<= 32;
|
|
ml += ll;
|
|
|
|
expon -= EXP_BIAS-1;
|
|
if (expon <= EXP_WAY_UNDER)
|
|
expon = EXP_WAY_UNDER;
|
|
|
|
/* if the addition of signed 16-bit values overflowed, substitute
|
|
the maximum positive exponent to force FPU_round to produce overflow */
|
|
if (expon > 0x7FFE)
|
|
expon = 0x7FFE;
|
|
|
|
c->exp = expon;
|
|
|
|
if (! (mu & BX_CONST64(0x8000000000000000)))
|
|
{
|
|
mu <<= 1;
|
|
if (ml & BX_CONST64(0x8000000000000000))
|
|
mu |= 1;
|
|
ml <<= 1;
|
|
c->exp --;
|
|
}
|
|
|
|
ll = ml;
|
|
lh = ml >> 32;
|
|
|
|
if (ll)
|
|
lh |= 1;
|
|
|
|
c->sigl = mu;
|
|
c->sigh = mu >> 32;
|
|
|
|
return FPU_round(c, lh, 0, cw, sign);
|
|
}
|