/* $OpenBSD: fpu_rem.c,v 1.2 1996/05/09 22:20:48 niklas Exp $ */ /* $NetBSD: fpu_rem.c,v 1.3 1996/04/30 12:02:54 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 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) { 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 */ goto Step9; } 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); }