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-/*
- * reg_add_sub.c
- *
- * Functions to add or subtract two registers and put the result in a third.
- *
- * Copyright (C) 1992,1993,1994
- * W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
- * Australia. E-mail billm@vaxc.cc.monash.edu.au
- * All rights reserved.
- *
- * This copyright notice covers the redistribution and use of the
- * FPU emulator developed by W. Metzenthen. It covers only its use
- * in the 386BSD, FreeBSD and NetBSD operating systems. Any other
- * use is not permitted under this copyright.
- *
- * 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 include information specifying
- * that source code for the emulator is freely available and include
- * either:
- * a) an offer to provide the source code for a nominal distribution
- * fee, or
- * b) list at least two alternative methods whereby the source
- * can be obtained, e.g. a publically accessible bulletin board
- * and an anonymous ftp site from which the software can be
- * downloaded.
- * 3. All advertising materials specifically mentioning features or use of
- * this emulator must acknowledge that it was developed by W. Metzenthen.
- * 4. The name of W. Metzenthen may not be used to endorse or promote
- * products derived from this software without specific prior written
- * permission.
- *
- * THIS SOFTWARE IS PROVIDED ``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
- * W. METZENTHEN 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.
- *
- *
- * The purpose of this copyright, based upon the Berkeley copyright, is to
- * ensure that the covered software remains freely available to everyone.
- *
- * The software (with necessary differences) is also available, but under
- * the terms of the GNU copyleft, for the Linux operating system and for
- * the djgpp ms-dos extender.
- *
- * W. Metzenthen June 1994.
- *
- *
- * $FreeBSD$
- *
- */
-
-/*---------------------------------------------------------------------------+
- | For each function, the destination may be any FPU_REG, including one of |
- | the source FPU_REGs. |
- +---------------------------------------------------------------------------*/
-
-#include <gnu/i386/fpemul/reg_constant.h>
-#include <gnu/i386/fpemul/control_w.h>
-
-
-void
-reg_add(FPU_REG * a, FPU_REG * b, FPU_REG * dest, int control_w)
-{
- int diff;
-
- if (!(a->tag | b->tag)) {
- /* Both registers are valid */
- if (!(a->sign ^ b->sign)) {
- /* signs are the same */
- reg_u_add(a, b, dest, control_w);
- dest->sign = a->sign;
- return;
- }
- /* The signs are different, so do a subtraction */
- diff = a->exp - b->exp;
- if (!diff) {
- diff = a->sigh - b->sigh; /* Works only if ms bits
- * are identical */
- if (!diff) {
- diff = a->sigl > b->sigl;
- if (!diff)
- diff = -(a->sigl < b->sigl);
- }
- }
- if (diff > 0) {
- reg_u_sub(a, b, dest, control_w);
- dest->sign = a->sign;
- } else
- if (diff == 0) {
- reg_move(&CONST_Z, dest);
- /* sign depends upon rounding mode */
- dest->sign = ((control_w & CW_RC) != RC_DOWN)
- ? SIGN_POS : SIGN_NEG;
- } else {
- reg_u_sub(b, a, dest, control_w);
- dest->sign = b->sign;
- }
- return;
- } else {
- if ((a->tag == TW_NaN) || (b->tag == TW_NaN)) {
- real_2op_NaN(a, b, dest);
- return;
- } else
- if (a->tag == TW_Zero) {
- if (b->tag == TW_Zero) {
- char different_signs = a->sign ^ b->sign;
- /* Both are zero, result will be zero. */
- reg_move(a, dest);
- if (different_signs) {
- /* Signs are different. */
- /* Sign of answer depends upon
- * rounding mode. */
- dest->sign = ((control_w & CW_RC) != RC_DOWN)
- ? SIGN_POS : SIGN_NEG;
- }
- } else {
-#ifdef DENORM_OPERAND
- if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(b, dest);
- }
- return;
- } else
- if (b->tag == TW_Zero) {
-#ifdef DENORM_OPERAND
- if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(a, dest);
- return;
- } else
- if (a->tag == TW_Infinity) {
- if (b->tag != TW_Infinity) {
-#ifdef DENORM_OPERAND
- if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(a, dest);
- return;
- }
- if (a->sign == b->sign) {
- /* They are both + or
- * - infinity */
- reg_move(a, dest);
- return;
- }
- arith_invalid(dest); /* Infinity-Infinity is
- * undefined. */
- return;
- } else
- if (b->tag == TW_Infinity) {
-#ifdef DENORM_OPERAND
- if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(b, dest);
- return;
- }
- }
-#ifdef PARANOID
- EXCEPTION(EX_INTERNAL | 0x101);
-#endif
-}
-
-
-/* Subtract b from a. (a-b) -> dest */
-void
-reg_sub(FPU_REG * a, FPU_REG * b, FPU_REG * dest, int control_w)
-{
- int diff;
-
- if (!(a->tag | b->tag)) {
- /* Both registers are valid */
- diff = a->exp - b->exp;
- if (!diff) {
- diff = a->sigh - b->sigh; /* Works only if ms bits
- * are identical */
- if (!diff) {
- diff = a->sigl > b->sigl;
- if (!diff)
- diff = -(a->sigl < b->sigl);
- }
- }
- switch (a->sign * 2 + b->sign) {
- case 0: /* P - P */
- case 3: /* N - N */
- if (diff > 0) {
- reg_u_sub(a, b, dest, control_w);
- dest->sign = a->sign;
- } else
- if (diff == 0) {
-#ifdef DENORM_OPERAND
- if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(&CONST_Z, dest);
- /* sign depends upon rounding mode */
- dest->sign = ((control_w & CW_RC) != RC_DOWN)
- ? SIGN_POS : SIGN_NEG;
- } else {
- reg_u_sub(b, a, dest, control_w);
- dest->sign = a->sign ^ SIGN_POS ^ SIGN_NEG;
- }
- return;
- case 1: /* P - N */
- reg_u_add(a, b, dest, control_w);
- dest->sign = SIGN_POS;
- return;
- case 2: /* N - P */
- reg_u_add(a, b, dest, control_w);
- dest->sign = SIGN_NEG;
- return;
- }
- } else {
- if ((a->tag == TW_NaN) || (b->tag == TW_NaN)) {
- real_2op_NaN(a, b, dest);
- return;
- } else
- if (b->tag == TW_Zero) {
- if (a->tag == TW_Zero) {
- char same_signs = !(a->sign ^ b->sign);
- /* Both are zero, result will be zero. */
- reg_move(a, dest); /* Answer for different
- * signs. */
- if (same_signs) {
- /* Sign depends upon rounding
- * mode */
- dest->sign = ((control_w & CW_RC) != RC_DOWN)
- ? SIGN_POS : SIGN_NEG;
- }
- } else {
-#ifdef DENORM_OPERAND
- if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(a, dest);
- }
- return;
- } else
- if (a->tag == TW_Zero) {
-#ifdef DENORM_OPERAND
- if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(b, dest);
- dest->sign ^= SIGN_POS ^ SIGN_NEG;
- return;
- } else
- if (a->tag == TW_Infinity) {
- if (b->tag != TW_Infinity) {
-#ifdef DENORM_OPERAND
- if ((b->tag == TW_Valid) && (b->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(a, dest);
- return;
- }
- /* Both args are Infinity */
- if (a->sign == b->sign) {
- arith_invalid(dest); /* Infinity-Infinity is
- * undefined. */
- return;
- }
- reg_move(a, dest);
- return;
- } else
- if (b->tag == TW_Infinity) {
-#ifdef DENORM_OPERAND
- if ((a->tag == TW_Valid) && (a->exp <= EXP_UNDER) &&
- denormal_operand())
- return;
-#endif /* DENORM_OPERAND */
- reg_move(b, dest);
- dest->sign ^= SIGN_POS ^ SIGN_NEG;
- return;
- }
- }
-#ifdef PARANOID
- EXCEPTION(EX_INTERNAL | 0x110);
-#endif
-}
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