301 lines
8.7 KiB
C
301 lines
8.7 KiB
C
/*
|
|
* 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
|
|
}
|