304 lines
8.9 KiB
C
304 lines
8.9 KiB
C
/*
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* reg_add_sub.c
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*
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* Functions to add or subtract two registers and put the result in a third.
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*
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* Copyright (C) 1992,1993,1994
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* W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
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* Australia. E-mail billm@vaxc.cc.monash.edu.au
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* All rights reserved.
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*
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* This copyright notice covers the redistribution and use of the
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* FPU emulator developed by W. Metzenthen. It covers only its use
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* in the 386BSD, FreeBSD and NetBSD operating systems. Any other
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* use is not permitted under this copyright.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must include information specifying
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* that source code for the emulator is freely available and include
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* either:
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* a) an offer to provide the source code for a nominal distribution
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* fee, or
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* b) list at least two alternative methods whereby the source
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* can be obtained, e.g. a publically accessible bulletin board
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* and an anonymous ftp site from which the software can be
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* downloaded.
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* 3. All advertising materials specifically mentioning features or use of
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* this emulator must acknowledge that it was developed by W. Metzenthen.
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* 4. The name of W. Metzenthen may not be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
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* W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*
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* The purpose of this copyright, based upon the Berkeley copyright, is to
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* ensure that the covered software remains freely available to everyone.
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*
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* The software (with necessary differences) is also available, but under
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* the terms of the GNU copyleft, for the Linux operating system and for
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* the djgpp ms-dos extender.
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*
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* W. Metzenthen June 1994.
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*
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*
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* $Id: reg_add_sub.c,v 1.3 1994/06/10 07:44:44 rich Exp $
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*
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*/
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/*---------------------------------------------------------------------------+
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| For each function, the destination may be any FPU_REG, including one of |
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| the source FPU_REGs. |
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+---------------------------------------------------------------------------*/
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#include <gnu/i386/fpemul/exception.h>
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#include <gnu/i386/fpemul/reg_constant.h>
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#include <gnu/i386/fpemul/fpu_emu.h>
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#include <gnu/i386/fpemul/control_w.h>
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#include <gnu/i386/fpemul/fpu_system.h>
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void
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reg_add(FPU_REG * a, FPU_REG * b, FPU_REG * dest, int control_w)
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{
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int diff;
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if (!(a->tag | b->tag)) {
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/* Both registers are valid */
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if (!(a->sign ^ b->sign)) {
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/* signs are the same */
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reg_u_add(a, b, dest, control_w);
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dest->sign = a->sign;
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return;
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}
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/* The signs are different, so do a subtraction */
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diff = a->exp - b->exp;
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if (!diff) {
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diff = a->sigh - b->sigh; /* Works only if ms bits
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* are identical */
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if (!diff) {
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diff = a->sigl > b->sigl;
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if (!diff)
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diff = -(a->sigl < b->sigl);
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}
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}
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if (diff > 0) {
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reg_u_sub(a, b, dest, control_w);
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dest->sign = a->sign;
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} else
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if (diff == 0) {
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reg_move(&CONST_Z, dest);
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/* sign depends upon rounding mode */
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dest->sign = ((control_w & CW_RC) != RC_DOWN)
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? SIGN_POS : SIGN_NEG;
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} else {
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reg_u_sub(b, a, dest, control_w);
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dest->sign = b->sign;
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}
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return;
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} else {
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if ((a->tag == TW_NaN) || (b->tag == TW_NaN)) {
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real_2op_NaN(a, b, dest);
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return;
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} else
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if (a->tag == TW_Zero) {
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if (b->tag == TW_Zero) {
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char different_signs = a->sign ^ b->sign;
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/* Both are zero, result will be zero. */
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reg_move(a, dest);
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if (different_signs) {
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/* Signs are different. */
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/* Sign of answer depends upon
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* rounding mode. */
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dest->sign = ((control_w & CW_RC) != RC_DOWN)
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? SIGN_POS : SIGN_NEG;
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}
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} else {
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#ifdef DENORM_OPERAND
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if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(b, dest);
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}
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return;
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} else
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if (b->tag == TW_Zero) {
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#ifdef DENORM_OPERAND
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if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(a, dest);
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return;
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} else
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if (a->tag == TW_Infinity) {
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if (b->tag != TW_Infinity) {
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#ifdef DENORM_OPERAND
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if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(a, dest);
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return;
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}
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if (a->sign == b->sign) {
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/* They are both + or
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* - infinity */
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reg_move(a, dest);
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return;
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}
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arith_invalid(dest); /* Infinity-Infinity is
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* undefined. */
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return;
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} else
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if (b->tag == TW_Infinity) {
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#ifdef DENORM_OPERAND
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if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(b, dest);
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return;
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}
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}
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#ifdef PARANOID
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EXCEPTION(EX_INTERNAL | 0x101);
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#endif
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}
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/* Subtract b from a. (a-b) -> dest */
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void
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reg_sub(FPU_REG * a, FPU_REG * b, FPU_REG * dest, int control_w)
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{
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int diff;
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if (!(a->tag | b->tag)) {
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/* Both registers are valid */
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diff = a->exp - b->exp;
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if (!diff) {
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diff = a->sigh - b->sigh; /* Works only if ms bits
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* are identical */
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if (!diff) {
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diff = a->sigl > b->sigl;
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if (!diff)
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diff = -(a->sigl < b->sigl);
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}
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}
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switch (a->sign * 2 + b->sign) {
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case 0: /* P - P */
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case 3: /* N - N */
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if (diff > 0) {
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reg_u_sub(a, b, dest, control_w);
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dest->sign = a->sign;
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} else
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if (diff == 0) {
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#ifdef DENORM_OPERAND
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if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(&CONST_Z, dest);
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/* sign depends upon rounding mode */
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dest->sign = ((control_w & CW_RC) != RC_DOWN)
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? SIGN_POS : SIGN_NEG;
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} else {
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reg_u_sub(b, a, dest, control_w);
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dest->sign = a->sign ^ SIGN_POS ^ SIGN_NEG;
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}
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return;
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case 1: /* P - N */
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reg_u_add(a, b, dest, control_w);
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dest->sign = SIGN_POS;
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return;
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case 2: /* N - P */
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reg_u_add(a, b, dest, control_w);
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dest->sign = SIGN_NEG;
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return;
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}
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} else {
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if ((a->tag == TW_NaN) || (b->tag == TW_NaN)) {
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real_2op_NaN(a, b, dest);
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return;
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} else
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if (b->tag == TW_Zero) {
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if (a->tag == TW_Zero) {
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char same_signs = !(a->sign ^ b->sign);
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/* Both are zero, result will be zero. */
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reg_move(a, dest); /* Answer for different
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* signs. */
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if (same_signs) {
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/* Sign depends upon rounding
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* mode */
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dest->sign = ((control_w & CW_RC) != RC_DOWN)
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? SIGN_POS : SIGN_NEG;
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}
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} else {
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#ifdef DENORM_OPERAND
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if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(a, dest);
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}
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return;
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} else
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if (a->tag == TW_Zero) {
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#ifdef DENORM_OPERAND
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if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(b, dest);
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dest->sign ^= SIGN_POS ^ SIGN_NEG;
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return;
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} else
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if (a->tag == TW_Infinity) {
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if (b->tag != TW_Infinity) {
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#ifdef DENORM_OPERAND
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if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(a, dest);
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return;
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}
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/* Both args are Infinity */
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if (a->sign == b->sign) {
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arith_invalid(dest); /* Infinity-Infinity is
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* undefined. */
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return;
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}
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reg_move(a, dest);
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return;
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} else
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if (b->tag == TW_Infinity) {
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#ifdef DENORM_OPERAND
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if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
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denormal_operand())
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return;
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#endif /* DENORM_OPERAND */
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reg_move(b, dest);
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dest->sign ^= SIGN_POS ^ SIGN_NEG;
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return;
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}
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}
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#ifdef PARANOID
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EXCEPTION(EX_INTERNAL | 0x110);
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#endif
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}
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