291 lines
7.9 KiB
C
291 lines
7.9 KiB
C
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/*
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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/sfrem.c $Revision: 1.1 $
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*
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* Purpose:
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* Single Precision Floating-point Remainder
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*
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* External Interfaces:
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* sgl_frem(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 "sgl_float.h"
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/*
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* Single Precision Floating-point Remainder
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*/
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int
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sgl_frem (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
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sgl_floating_point * dstptr, unsigned int *status)
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{
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register unsigned int opnd1, opnd2, result;
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register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
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register boolean roundup = FALSE;
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opnd1 = *srcptr1;
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opnd2 = *srcptr2;
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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 ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
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if (Sgl_iszero_mantissa(opnd1)) {
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if (Sgl_isnotnan(opnd2)) {
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/* invalid since first operand is infinity */
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if (Is_invalidtrap_enabled())
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return(INVALIDEXCEPTION);
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Set_invalidflag();
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Sgl_makequietnan(result);
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*dstptr = result;
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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 (Sgl_isone_signaling(opnd1)) {
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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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Sgl_set_quiet(opnd1);
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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 (Sgl_is_signalingnan(opnd2)) {
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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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Sgl_set_quiet(opnd2);
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*dstptr = opnd2;
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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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*dstptr = opnd1;
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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 ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
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if (Sgl_iszero_mantissa(opnd2)) {
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/*
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* return first operand
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*/
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*dstptr = opnd1;
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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 (Sgl_isone_signaling(opnd2)) {
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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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Sgl_set_quiet(opnd2);
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}
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/*
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* return quiet NaN
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*/
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*dstptr = opnd2;
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return(NOEXCEPTION);
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}
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/*
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* check second operand for zero
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*/
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if (Sgl_iszero_exponentmantissa(opnd2)) {
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/* invalid since second operand is zero */
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if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
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Set_invalidflag();
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Sgl_makequietnan(result);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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/*
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* get sign of result
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*/
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result = opnd1;
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/*
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* check for denormalized operands
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*/
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if (opnd1_exponent == 0) {
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/* check for zero */
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if (Sgl_iszero_mantissa(opnd1)) {
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*dstptr = opnd1;
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return(NOEXCEPTION);
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}
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/* normalize, then continue */
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opnd1_exponent = 1;
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Sgl_normalize(opnd1,opnd1_exponent);
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}
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else {
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Sgl_clear_signexponent_set_hidden(opnd1);
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}
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if (opnd2_exponent == 0) {
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/* normalize, then continue */
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opnd2_exponent = 1;
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Sgl_normalize(opnd2,opnd2_exponent);
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}
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else {
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Sgl_clear_signexponent_set_hidden(opnd2);
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}
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/* find result exponent and divide step loop count */
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dest_exponent = opnd2_exponent - 1;
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stepcount = opnd1_exponent - opnd2_exponent;
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/*
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* check for opnd1/opnd2 < 1
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*/
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if (stepcount < 0) {
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/*
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* check for opnd1/opnd2 > 1/2
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*
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* In this case n will round to 1, so
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* r = opnd1 - opnd2
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*/
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if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
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Sgl_all(result) = ~Sgl_all(result); /* set sign */
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/* align opnd2 with opnd1 */
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Sgl_leftshiftby1(opnd2);
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Sgl_subtract(opnd2,opnd1,opnd2);
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/* now normalize */
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while (Sgl_iszero_hidden(opnd2)) {
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Sgl_leftshiftby1(opnd2);
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dest_exponent--;
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}
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Sgl_set_exponentmantissa(result,opnd2);
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goto testforunderflow;
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}
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/*
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* opnd1/opnd2 <= 1/2
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*
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* In this case n will round to zero, so
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* r = opnd1
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*/
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Sgl_set_exponentmantissa(result,opnd1);
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dest_exponent = opnd1_exponent;
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goto testforunderflow;
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}
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/*
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* Generate result
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*
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* Do iterative subtract until remainder is less than operand 2.
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*/
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while (stepcount-- > 0 && Sgl_all(opnd1)) {
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if (Sgl_isnotlessthan(opnd1,opnd2))
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Sgl_subtract(opnd1,opnd2,opnd1);
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Sgl_leftshiftby1(opnd1);
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}
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/*
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* Do last subtract, then determine which way to round if remainder
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* is exactly 1/2 of opnd2
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*/
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if (Sgl_isnotlessthan(opnd1,opnd2)) {
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Sgl_subtract(opnd1,opnd2,opnd1);
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roundup = TRUE;
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}
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if (stepcount > 0 || Sgl_iszero(opnd1)) {
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/* division is exact, remainder is zero */
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Sgl_setzero_exponentmantissa(result);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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/*
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* Check for cases where opnd1/opnd2 < n
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*
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* In this case the result's sign will be opposite that of
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* opnd1. The mantissa also needs some correction.
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*/
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Sgl_leftshiftby1(opnd1);
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if (Sgl_isgreaterthan(opnd1,opnd2)) {
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Sgl_invert_sign(result);
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Sgl_subtract((opnd2<<1),opnd1,opnd1);
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}
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/* check for remainder being exactly 1/2 of opnd2 */
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else if (Sgl_isequal(opnd1,opnd2) && roundup) {
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Sgl_invert_sign(result);
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}
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/* normalize result's mantissa */
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while (Sgl_iszero_hidden(opnd1)) {
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dest_exponent--;
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Sgl_leftshiftby1(opnd1);
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}
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Sgl_set_exponentmantissa(result,opnd1);
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/*
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* Test for underflow
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*/
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testforunderflow:
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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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Sgl_setwrapped_exponent(result,dest_exponent,unfl);
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*dstptr = result;
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/* frem is always exact */
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return(UNDERFLOWEXCEPTION);
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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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if (dest_exponent >= (1 - SGL_P)) {
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Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
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}
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else {
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Sgl_setzero_exponentmantissa(result);
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}
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}
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else Sgl_set_exponent(result,dest_exponent);
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*dstptr = result;
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return(NOEXCEPTION);
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}
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