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freebsd/sys/gnu/i386/fpemul/reg_add_sub.c
Peter Wemm c3aac50f28 $Id$ -> $FreeBSD$
1999-08-28 01:08:13 +00:00

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8.7 KiB
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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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