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linux/arch/parisc/math-emu/dfdiv.c
Linus Torvalds 1da177e4c3 Linux-2.6.12-rc2 
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00

401 lines
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/*
* Linux/PA-RISC Project (http://www.parisc-linux.org/)
*
* Floating-point emulation code
* Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* BEGIN_DESC
*
* File:
* @(#) pa/spmath/dfdiv.c $Revision: 1.1 $
*
* Purpose:
* Double Precision Floating-point Divide
*
* External Interfaces:
* dbl_fdiv(srcptr1,srcptr2,dstptr,status)
*
* Internal Interfaces:
*
* Theory:
* <<please update with a overview of the operation of this file>>
*
* END_DESC
*/
#include "float.h"
#include "dbl_float.h"
/*
* Double Precision Floating-point Divide
*/
int
dbl_fdiv (dbl_floating_point * srcptr1, dbl_floating_point * srcptr2,
dbl_floating_point * dstptr, unsigned int *status)
{
register unsigned int opnd1p1, opnd1p2, opnd2p1, opnd2p2;
register unsigned int opnd3p1, opnd3p2, resultp1, resultp2;
register int dest_exponent, count;
register boolean inexact = FALSE, guardbit = FALSE, stickybit = FALSE;
boolean is_tiny;
Dbl_copyfromptr(srcptr1,opnd1p1,opnd1p2);
Dbl_copyfromptr(srcptr2,opnd2p1,opnd2p2);
/*
* set sign bit of result
*/
if (Dbl_sign(opnd1p1) ^ Dbl_sign(opnd2p1))
Dbl_setnegativezerop1(resultp1);
else Dbl_setzerop1(resultp1);
/*
* check first operand for NaN's or infinity
*/
if (Dbl_isinfinity_exponent(opnd1p1)) {
if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
if (Dbl_isnotnan(opnd2p1,opnd2p2)) {
if (Dbl_isinfinity(opnd2p1,opnd2p2)) {
/*
* invalid since both operands
* are infinity
*/
if (Is_invalidtrap_enabled())
return(INVALIDEXCEPTION);
Set_invalidflag();
Dbl_makequietnan(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
/*
* return infinity
*/
Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
}
else {
/*
* is NaN; signaling or quiet?
*/
if (Dbl_isone_signaling(opnd1p1)) {
/* trap if INVALIDTRAP enabled */
if (Is_invalidtrap_enabled())
return(INVALIDEXCEPTION);
/* make NaN quiet */
Set_invalidflag();
Dbl_set_quiet(opnd1p1);
}
/*
* is second operand a signaling NaN?
*/
else if (Dbl_is_signalingnan(opnd2p1)) {
/* trap if INVALIDTRAP enabled */
if (Is_invalidtrap_enabled())
return(INVALIDEXCEPTION);
/* make NaN quiet */
Set_invalidflag();
Dbl_set_quiet(opnd2p1);
Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
return(NOEXCEPTION);
}
/*
* return quiet NaN
*/
Dbl_copytoptr(opnd1p1,opnd1p2,dstptr);
return(NOEXCEPTION);
}
}
/*
* check second operand for NaN's or infinity
*/
if (Dbl_isinfinity_exponent(opnd2p1)) {
if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
/*
* return zero
*/
Dbl_setzero_exponentmantissa(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
/*
* is NaN; signaling or quiet?
*/
if (Dbl_isone_signaling(opnd2p1)) {
/* trap if INVALIDTRAP enabled */
if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
/* make NaN quiet */
Set_invalidflag();
Dbl_set_quiet(opnd2p1);
}
/*
* return quiet NaN
*/
Dbl_copytoptr(opnd2p1,opnd2p2,dstptr);
return(NOEXCEPTION);
}
/*
* check for division by zero
*/
if (Dbl_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
/* invalid since both operands are zero */
if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
Set_invalidflag();
Dbl_makequietnan(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
if (Is_divisionbyzerotrap_enabled())
return(DIVISIONBYZEROEXCEPTION);
Set_divisionbyzeroflag();
Dbl_setinfinity_exponentmantissa(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
/*
* Generate exponent
*/
dest_exponent = Dbl_exponent(opnd1p1) - Dbl_exponent(opnd2p1) + DBL_BIAS;
/*
* Generate mantissa
*/
if (Dbl_isnotzero_exponent(opnd1p1)) {
/* set hidden bit */
Dbl_clear_signexponent_set_hidden(opnd1p1);
}
else {
/* check for zero */
if (Dbl_iszero_mantissa(opnd1p1,opnd1p2)) {
Dbl_setzero_exponentmantissa(resultp1,resultp2);
Dbl_copytoptr(resultp1,resultp2,dstptr);
return(NOEXCEPTION);
}
/* is denormalized, want to normalize */
Dbl_clear_signexponent(opnd1p1);
Dbl_leftshiftby1(opnd1p1,opnd1p2);
Dbl_normalize(opnd1p1,opnd1p2,dest_exponent);
}
/* opnd2 needs to have hidden bit set with msb in hidden bit */
if (Dbl_isnotzero_exponent(opnd2p1)) {
Dbl_clear_signexponent_set_hidden(opnd2p1);
}
else {
/* is denormalized; want to normalize */
Dbl_clear_signexponent(opnd2p1);
Dbl_leftshiftby1(opnd2p1,opnd2p2);
while (Dbl_iszero_hiddenhigh7mantissa(opnd2p1)) {
dest_exponent+=8;
Dbl_leftshiftby8(opnd2p1,opnd2p2);
}
if (Dbl_iszero_hiddenhigh3mantissa(opnd2p1)) {
dest_exponent+=4;
Dbl_leftshiftby4(opnd2p1,opnd2p2);
}
while (Dbl_iszero_hidden(opnd2p1)) {
dest_exponent++;
Dbl_leftshiftby1(opnd2p1,opnd2p2);
}
}
/* Divide the source mantissas */
/*
* A non-restoring divide algorithm is used.
*/
Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
Dbl_setzero(opnd3p1,opnd3p2);
for (count=1; count <= DBL_P && (opnd1p1 || opnd1p2); count++) {
Dbl_leftshiftby1(opnd1p1,opnd1p2);
Dbl_leftshiftby1(opnd3p1,opnd3p2);
if (Dbl_iszero_sign(opnd1p1)) {
Dbl_setone_lowmantissap2(opnd3p2);
Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
}
else {
Twoword_add(opnd1p1, opnd1p2, opnd2p1, opnd2p2);
}
}
if (count <= DBL_P) {
Dbl_leftshiftby1(opnd3p1,opnd3p2);
Dbl_setone_lowmantissap2(opnd3p2);
Dbl_leftshift(opnd3p1,opnd3p2,(DBL_P-count));
if (Dbl_iszero_hidden(opnd3p1)) {
Dbl_leftshiftby1(opnd3p1,opnd3p2);
dest_exponent--;
}
}
else {
if (Dbl_iszero_hidden(opnd3p1)) {
/* need to get one more bit of result */
Dbl_leftshiftby1(opnd1p1,opnd1p2);
Dbl_leftshiftby1(opnd3p1,opnd3p2);
if (Dbl_iszero_sign(opnd1p1)) {
Dbl_setone_lowmantissap2(opnd3p2);
Twoword_subtract(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
}
else {
Twoword_add(opnd1p1,opnd1p2,opnd2p1,opnd2p2);
}
dest_exponent--;
}
if (Dbl_iszero_sign(opnd1p1)) guardbit = TRUE;
stickybit = Dbl_allp1(opnd1p1) || Dbl_allp2(opnd1p2);
}
inexact = guardbit | stickybit;
/*
* round result
*/
if (inexact && (dest_exponent > 0 || Is_underflowtrap_enabled())) {
Dbl_clear_signexponent(opnd3p1);
switch (Rounding_mode()) {
case ROUNDPLUS:
if (Dbl_iszero_sign(resultp1))
Dbl_increment(opnd3p1,opnd3p2);
break;
case ROUNDMINUS:
if (Dbl_isone_sign(resultp1))
Dbl_increment(opnd3p1,opnd3p2);
break;
case ROUNDNEAREST:
if (guardbit && (stickybit ||
Dbl_isone_lowmantissap2(opnd3p2))) {
Dbl_increment(opnd3p1,opnd3p2);
}
}
if (Dbl_isone_hidden(opnd3p1)) dest_exponent++;
}
Dbl_set_mantissa(resultp1,resultp2,opnd3p1,opnd3p2);
/*
* Test for overflow
*/
if (dest_exponent >= DBL_INFINITY_EXPONENT) {
/* trap if OVERFLOWTRAP enabled */
if (Is_overflowtrap_enabled()) {
/*
* Adjust bias of result
*/
Dbl_setwrapped_exponent(resultp1,dest_exponent,ovfl);
Dbl_copytoptr(resultp1,resultp2,dstptr);
if (inexact)
if (Is_inexacttrap_enabled())
return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
else Set_inexactflag();
return(OVERFLOWEXCEPTION);
}
Set_overflowflag();
/* set result to infinity or largest number */
Dbl_setoverflow(resultp1,resultp2);
inexact = TRUE;
}
/*
* Test for underflow
*/
else if (dest_exponent <= 0) {
/* trap if UNDERFLOWTRAP enabled */
if (Is_underflowtrap_enabled()) {
/*
* Adjust bias of result
*/
Dbl_setwrapped_exponent(resultp1,dest_exponent,unfl);
Dbl_copytoptr(resultp1,resultp2,dstptr);
if (inexact)
if (Is_inexacttrap_enabled())
return(UNDERFLOWEXCEPTION | INEXACTEXCEPTION);
else Set_inexactflag();
return(UNDERFLOWEXCEPTION);
}
/* Determine if should set underflow flag */
is_tiny = TRUE;
if (dest_exponent == 0 && inexact) {
switch (Rounding_mode()) {
case ROUNDPLUS:
if (Dbl_iszero_sign(resultp1)) {
Dbl_increment(opnd3p1,opnd3p2);
if (Dbl_isone_hiddenoverflow(opnd3p1))
is_tiny = FALSE;
Dbl_decrement(opnd3p1,opnd3p2);
}
break;
case ROUNDMINUS:
if (Dbl_isone_sign(resultp1)) {
Dbl_increment(opnd3p1,opnd3p2);
if (Dbl_isone_hiddenoverflow(opnd3p1))
is_tiny = FALSE;
Dbl_decrement(opnd3p1,opnd3p2);
}
break;
case ROUNDNEAREST:
if (guardbit && (stickybit ||
Dbl_isone_lowmantissap2(opnd3p2))) {
Dbl_increment(opnd3p1,opnd3p2);
if (Dbl_isone_hiddenoverflow(opnd3p1))
is_tiny = FALSE;
Dbl_decrement(opnd3p1,opnd3p2);
}
break;
}
}
/*
* denormalize result or set to signed zero
*/
stickybit = inexact;
Dbl_denormalize(opnd3p1,opnd3p2,dest_exponent,guardbit,
stickybit,inexact);
/* return rounded number */
if (inexact) {
switch (Rounding_mode()) {
case ROUNDPLUS:
if (Dbl_iszero_sign(resultp1)) {
Dbl_increment(opnd3p1,opnd3p2);
}
break;
case ROUNDMINUS:
if (Dbl_isone_sign(resultp1)) {
Dbl_increment(opnd3p1,opnd3p2);
}
break;
case ROUNDNEAREST:
if (guardbit && (stickybit ||
Dbl_isone_lowmantissap2(opnd3p2))) {
Dbl_increment(opnd3p1,opnd3p2);
}
break;
}
if (is_tiny) Set_underflowflag();
}
Dbl_set_exponentmantissa(resultp1,resultp2,opnd3p1,opnd3p2);
}
else Dbl_set_exponent(resultp1,dest_exponent);
Dbl_copytoptr(resultp1,resultp2,dstptr);
/* check for inexact */
if (inexact) {
if (Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
else Set_inexactflag();
}
return(NOEXCEPTION);
}
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