382 lines
11 KiB
C
382 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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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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/*
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* BEGIN_DESC
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*
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* File:
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* @(#) pa/spmath/dfmpy.c $Revision: 1.1 $
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*
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* Purpose:
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* Double Precision Floating-point Multiply
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*
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* External Interfaces:
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* dbl_fmpy(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 Multiply
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*/
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int
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dbl_fmpy(
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dbl_floating_point *srcptr1,
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dbl_floating_point *srcptr2,
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dbl_floating_point *dstptr,
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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_iszero_exponentmantissa(opnd2p1,opnd2p2)) {
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/*
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* invalid since operands are infinity
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* and zero
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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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if (Dbl_iszero_exponentmantissa(opnd1p1,opnd1p2)) {
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/* invalid since operands are zero & 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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Dbl_makequietnan(opnd2p1,opnd2p2);
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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 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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* 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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* 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, adjust exponent */
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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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/* check for zero */
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if (Dbl_iszero_mantissa(opnd2p1,opnd2p2)) {
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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(opnd2p1);
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Dbl_leftshiftby1(opnd2p1,opnd2p2);
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Dbl_normalize(opnd2p1,opnd2p2,dest_exponent);
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}
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/* Multiply two source mantissas together */
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/* make room for guard bits */
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Dbl_leftshiftby7(opnd2p1,opnd2p2);
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Dbl_setzero(opnd3p1,opnd3p2);
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/*
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* Four bits at a time are inspected in each loop, and a
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* simple shift and add multiply algorithm is used.
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*/
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for (count=1;count<=DBL_P;count+=4) {
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stickybit |= Dlow4p2(opnd3p2);
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Dbl_rightshiftby4(opnd3p1,opnd3p2);
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if (Dbit28p2(opnd1p2)) {
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/* Twoword_add should be an ADDC followed by an ADD. */
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Twoword_add(opnd3p1, opnd3p2, opnd2p1<<3 | opnd2p2>>29,
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opnd2p2<<3);
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}
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if (Dbit29p2(opnd1p2)) {
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Twoword_add(opnd3p1, opnd3p2, opnd2p1<<2 | opnd2p2>>30,
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opnd2p2<<2);
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}
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if (Dbit30p2(opnd1p2)) {
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Twoword_add(opnd3p1, opnd3p2, opnd2p1<<1 | opnd2p2>>31,
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opnd2p2<<1);
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}
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if (Dbit31p2(opnd1p2)) {
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Twoword_add(opnd3p1, opnd3p2, opnd2p1, opnd2p2);
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}
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Dbl_rightshiftby4(opnd1p1,opnd1p2);
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}
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if (Dbit3p1(opnd3p1)==0) {
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Dbl_leftshiftby1(opnd3p1,opnd3p2);
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}
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else {
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/* result mantissa >= 2. */
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dest_exponent++;
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}
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/* check for denormalized result */
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while (Dbit3p1(opnd3p1)==0) {
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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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* check for guard, sticky and inexact bits
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*/
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stickybit |= Dallp2(opnd3p2) << 25;
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guardbit = (Dallp2(opnd3p2) << 24) >> 31;
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inexact = guardbit | stickybit;
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/* align result mantissa */
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Dbl_rightshiftby8(opnd3p1,opnd3p2);
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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) {
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if (stickybit || 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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inexact = TRUE;
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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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}
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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 zero or smallest 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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/* check for inexact */
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Dbl_copytoptr(resultp1,resultp2,dstptr);
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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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