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