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