236 lines
6.1 KiB
C
236 lines
6.1 KiB
C
/* $NetBSD: fpu_rem.c,v 1.1 1995/11/03 04:47:17 briggs Exp $ */
|
|
|
|
/*
|
|
* Copyright (c) 1995 Ken Nakata
|
|
* All rights reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution.
|
|
* 3. Neither the name of the author nor the names of its contributors
|
|
* may be used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
* SUCH DAMAGE.
|
|
*
|
|
* @(#)fpu_rem.c 10/24/95
|
|
*/
|
|
|
|
#include <sys/types.h>
|
|
#include <sys/signal.h>
|
|
#include <machine/frame.h>
|
|
|
|
#include "fpu_emulate.h"
|
|
|
|
/*
|
|
* ALGORITHM
|
|
*
|
|
* Step 1. Save and strip signs of X and Y: signX := sign(X),
|
|
* signY := sign(Y), X := *X*, Y := *Y*,
|
|
* signQ := signX EOR signY. Record whether MOD or REM
|
|
* is requested.
|
|
*
|
|
* Step 2. Set L := expo(X)-expo(Y), k := 0, Q := 0.
|
|
* If (L < 0) then
|
|
* R := X, go to Step 4.
|
|
* else
|
|
* R := 2^(-L)X, j := L.
|
|
* endif
|
|
*
|
|
* Step 3. Perform MOD(X,Y)
|
|
* 3.1 If R = Y, go to Step 9.
|
|
* 3.2 If R > Y, then { R := R - Y, Q := Q + 1}
|
|
* 3.3 If j = 0, go to Step 4.
|
|
* 3.4 k := k + 1, j := j - 1, Q := 2Q, R := 2R. Go to
|
|
* Step 3.1.
|
|
*
|
|
* Step 4. At this point, R = X - QY = MOD(X,Y). Set
|
|
* Last_Subtract := false (used in Step 7 below). If
|
|
* MOD is requested, go to Step 6.
|
|
*
|
|
* Step 5. R = MOD(X,Y), but REM(X,Y) is requested.
|
|
* 5.1 If R < Y/2, then R = MOD(X,Y) = REM(X,Y). Go to
|
|
* Step 6.
|
|
* 5.2 If R > Y/2, then { set Last_Subtract := true,
|
|
* Q := Q + 1, Y := signY*Y }. Go to Step 6.
|
|
* 5.3 This is the tricky case of R = Y/2. If Q is odd,
|
|
* then { Q := Q + 1, signX := -signX }.
|
|
*
|
|
* Step 6. R := signX*R.
|
|
*
|
|
* Step 7. If Last_Subtract = true, R := R - Y.
|
|
*
|
|
* Step 8. Return signQ, last 7 bits of Q, and R as required.
|
|
*
|
|
* Step 9. At this point, R = 2^(-j)*X - Q Y = Y. Thus,
|
|
* X = 2^(j)*(Q+1)Y. set Q := 2^(j)*(Q+1),
|
|
* R := 0. Return signQ, last 7 bits of Q, and R.
|
|
*/
|
|
|
|
static struct fpn * __fpu_modrem __P((struct fpemu *fe, int modrem));
|
|
|
|
static struct fpn *
|
|
__fpu_modrem(fe, modrem)
|
|
struct fpemu *fe;
|
|
int modrem;
|
|
{
|
|
static struct fpn X, Y;
|
|
struct fpn *x, *y, *r;
|
|
u_int signX, signY, signQ;
|
|
int i, j, k, l, q;
|
|
int Last_Subtract;
|
|
|
|
CPYFPN(&X, &fe->fe_f1);
|
|
CPYFPN(&Y, &fe->fe_f2);
|
|
x = &X;
|
|
y = &Y;
|
|
r = &fe->fe_f2;
|
|
|
|
/*
|
|
* Step 1
|
|
*/
|
|
signX = x->fp_sign;
|
|
signY = y->fp_sign;
|
|
signQ = (signX ^ signY);
|
|
x->fp_sign = y->fp_sign = 0;
|
|
|
|
/*
|
|
* Step 2
|
|
*/
|
|
l = x->fp_exp - y->fp_exp;
|
|
k = 0;
|
|
q = 0;
|
|
if (l < 0) {
|
|
goto Step4;
|
|
} else {
|
|
CPYFPN(r, x);
|
|
r->fp_exp -= l;
|
|
j = l;
|
|
|
|
/*
|
|
* Step 3
|
|
*/
|
|
while (y->fp_exp != r->fp_exp || y->fp_mant[0] != r->fp_mant[0] ||
|
|
y->fp_mant[1] != r->fp_mant[1] ||
|
|
y->fp_mant[2] != r->fp_mant[2] ||
|
|
y->fp_mant[3] != r->fp_mant[3]) {
|
|
|
|
/* Step 3.2 */
|
|
if (y->fp_exp < r->fp_exp || y->fp_mant[0] < r->fp_mant[0] ||
|
|
y->fp_mant[1] < r->fp_mant[1] ||
|
|
y->fp_mant[2] < r->fp_mant[2] ||
|
|
y->fp_mant[3] < r->fp_mant[3]) {
|
|
CPYFPN(&fe->fe_f1, r);
|
|
CPYFPN(&fe->fe_f2, y);
|
|
fe->fe_f2.fp_sign = 1;
|
|
r = fpu_add(fe);
|
|
q++;
|
|
}
|
|
|
|
/* Step 3.3 */
|
|
if (j == 0)
|
|
goto Step4;
|
|
|
|
/* Step 3.4 */
|
|
k++;
|
|
j--;
|
|
q += q;
|
|
r->fp_exp++;
|
|
}
|
|
/* Step 9 */
|
|
|
|
}
|
|
Step4:
|
|
Last_Subtract = 0;
|
|
if (modrem == 0)
|
|
goto Step6;
|
|
|
|
/*
|
|
* Step 5
|
|
*/
|
|
/* Step 5.1 */
|
|
if (r->fp_exp + 1 < y->fp_exp ||
|
|
r->fp_exp + 1 == y->fp_exp &&
|
|
(r->fp_mant[0] < y->fp_mant[0] || r->fp_mant[1] < y->fp_mant[1] ||
|
|
r->fp_mant[2] < y->fp_mant[3] || r->fp_mant[4] < y->fp_mant[4]))
|
|
/* if r < y/2 */
|
|
goto Step6;
|
|
/* Step 5.2 */
|
|
if (r->fp_exp + 1 != y->fp_exp ||
|
|
r->fp_mant[0] != y->fp_mant[0] || r->fp_mant[1] != y->fp_mant[1] ||
|
|
r->fp_mant[2] != y->fp_mant[2] || r->fp_mant[3] != y->fp_mant[3]) {
|
|
/* if (!(r < y/2) && !(r == y/2)) */
|
|
Last_Subtract = 1;
|
|
q++;
|
|
y->fp_sign = signY;
|
|
} else {
|
|
/* Step 5.3 */
|
|
/* r == y/2 */
|
|
if (q % 2) {
|
|
q++;
|
|
signX = !signX;
|
|
}
|
|
}
|
|
|
|
Step6:
|
|
r->fp_sign = signX;
|
|
|
|
/*
|
|
* Step 7
|
|
*/
|
|
if (Last_Subtract) {
|
|
CPYFPN(&fe->fe_f1, r);
|
|
CPYFPN(&fe->fe_f2, y);
|
|
fe->fe_f2.fp_sign = !y->fp_sign;
|
|
r = fpu_add(fe);
|
|
}
|
|
/*
|
|
* Step 8
|
|
*/
|
|
q &= 0x7f;
|
|
q |= (signQ << 7);
|
|
fe->fe_fpframe->fpf_fpsr =
|
|
fe->fe_fpsr =
|
|
(fe->fe_fpsr & ~FPSR_QTT) | (q << 16);
|
|
return r;
|
|
|
|
Step9:
|
|
fe->fe_f1.fp_class = FPC_ZERO;
|
|
q++;
|
|
q &= 0x7f;
|
|
q |= (signQ << 7);
|
|
fe->fe_fpframe->fpf_fpsr =
|
|
fe->fe_fpsr =
|
|
(fe->fe_fpsr & ~FPSR_QTT) | (q << 16);
|
|
return &fe->fe_f1;
|
|
}
|
|
|
|
struct fpn *
|
|
fpu_rem(fe)
|
|
struct fpemu *fe;
|
|
{
|
|
return __fpu_modrem(fe, 1);
|
|
}
|
|
|
|
struct fpn *
|
|
fpu_mod(fe)
|
|
struct fpemu *fe;
|
|
{
|
|
return __fpu_modrem(fe, 0);
|
|
}
|