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/arch/parisc/math-emu/sfrem.c

https://bitbucket.org/evzijst/gittest
C | 290 lines | 143 code | 14 blank | 133 comment | 46 complexity | d3b85df6c02da1019fb95ef2ab24c8d5 MD5 | raw file
  1/*
  2 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
  3 *
  4 * Floating-point emulation code
  5 *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
  6 *
  7 *    This program is free software; you can redistribute it and/or modify
  8 *    it under the terms of the GNU General Public License as published by
  9 *    the Free Software Foundation; either version 2, or (at your option)
 10 *    any later version.
 11 *
 12 *    This program is distributed in the hope that it will be useful,
 13 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 *    GNU General Public License for more details.
 16 *
 17 *    You should have received a copy of the GNU General Public License
 18 *    along with this program; if not, write to the Free Software
 19 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 20 */
 21/*
 22 * BEGIN_DESC
 23 *
 24 *  File:
 25 *	@(#)	pa/spmath/sfrem.c		$Revision: 1.1 $
 26 *
 27 *  Purpose:
 28 *	Single Precision Floating-point Remainder
 29 *
 30 *  External Interfaces:
 31 *	sgl_frem(srcptr1,srcptr2,dstptr,status)
 32 *
 33 *  Internal Interfaces:
 34 *
 35 *  Theory:
 36 *	<<please update with a overview of the operation of this file>>
 37 *
 38 * END_DESC
 39*/
 40
 41
 42
 43#include "float.h"
 44#include "sgl_float.h"
 45
 46/*
 47 *  Single Precision Floating-point Remainder
 48 */
 49
 50int
 51sgl_frem (sgl_floating_point * srcptr1, sgl_floating_point * srcptr2,
 52	  sgl_floating_point * dstptr, unsigned int *status)
 53{
 54	register unsigned int opnd1, opnd2, result;
 55	register int opnd1_exponent, opnd2_exponent, dest_exponent, stepcount;
 56	register boolean roundup = FALSE;
 57
 58	opnd1 = *srcptr1;
 59	opnd2 = *srcptr2;
 60	/*
 61	 * check first operand for NaN's or infinity
 62	 */
 63	if ((opnd1_exponent = Sgl_exponent(opnd1)) == SGL_INFINITY_EXPONENT) {
 64		if (Sgl_iszero_mantissa(opnd1)) {
 65			if (Sgl_isnotnan(opnd2)) {
 66				/* invalid since first operand is infinity */
 67				if (Is_invalidtrap_enabled()) 
 68                                	return(INVALIDEXCEPTION);
 69                                Set_invalidflag();
 70                                Sgl_makequietnan(result);
 71				*dstptr = result;
 72				return(NOEXCEPTION);
 73			}
 74		}
 75		else {
 76                	/*
 77                 	 * is NaN; signaling or quiet?
 78                 	 */
 79                	if (Sgl_isone_signaling(opnd1)) {
 80                        	/* trap if INVALIDTRAP enabled */
 81                        	if (Is_invalidtrap_enabled()) 
 82                            		return(INVALIDEXCEPTION);
 83                        	/* make NaN quiet */
 84                        	Set_invalidflag();
 85                        	Sgl_set_quiet(opnd1);
 86                	}
 87			/* 
 88			 * is second operand a signaling NaN? 
 89			 */
 90			else if (Sgl_is_signalingnan(opnd2)) {
 91                        	/* trap if INVALIDTRAP enabled */
 92                        	if (Is_invalidtrap_enabled()) 
 93                            		return(INVALIDEXCEPTION);
 94                        	/* make NaN quiet */
 95                        	Set_invalidflag();
 96                        	Sgl_set_quiet(opnd2);
 97                		*dstptr = opnd2;
 98                		return(NOEXCEPTION);
 99			}
100                	/*
101                 	 * return quiet NaN
102                 	 */
103                	*dstptr = opnd1;
104                	return(NOEXCEPTION);
105		}
106	} 
107	/*
108	 * check second operand for NaN's or infinity
109	 */
110	if ((opnd2_exponent = Sgl_exponent(opnd2)) == SGL_INFINITY_EXPONENT) {
111		if (Sgl_iszero_mantissa(opnd2)) {
112			/*
113			 * return first operand
114			 */
115                	*dstptr = opnd1;
116			return(NOEXCEPTION);
117		}
118                /*
119                 * is NaN; signaling or quiet?
120                 */
121                if (Sgl_isone_signaling(opnd2)) {
122                        /* trap if INVALIDTRAP enabled */
123                        if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
124                        /* make NaN quiet */
125                        Set_invalidflag();
126                        Sgl_set_quiet(opnd2);
127                }
128                /*
129                 * return quiet NaN
130                 */
131                *dstptr = opnd2;
132                return(NOEXCEPTION);
133	}
134	/*
135	 * check second operand for zero
136	 */
137	if (Sgl_iszero_exponentmantissa(opnd2)) {
138		/* invalid since second operand is zero */
139		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
140                Set_invalidflag();
141                Sgl_makequietnan(result);
142		*dstptr = result;
143		return(NOEXCEPTION);
144	}
145
146	/* 
147	 * get sign of result
148	 */
149	result = opnd1;  
150
151	/* 
152	 * check for denormalized operands
153	 */
154	if (opnd1_exponent == 0) {
155		/* check for zero */
156		if (Sgl_iszero_mantissa(opnd1)) {
157			*dstptr = opnd1;
158			return(NOEXCEPTION);
159		}
160		/* normalize, then continue */
161		opnd1_exponent = 1;
162		Sgl_normalize(opnd1,opnd1_exponent);
163	}
164	else {
165		Sgl_clear_signexponent_set_hidden(opnd1);
166	}
167	if (opnd2_exponent == 0) {
168		/* normalize, then continue */
169		opnd2_exponent = 1;
170		Sgl_normalize(opnd2,opnd2_exponent);
171	}
172	else {
173		Sgl_clear_signexponent_set_hidden(opnd2);
174	}
175
176	/* find result exponent and divide step loop count */
177	dest_exponent = opnd2_exponent - 1;
178	stepcount = opnd1_exponent - opnd2_exponent;
179
180	/*
181	 * check for opnd1/opnd2 < 1
182	 */
183	if (stepcount < 0) {
184		/*
185		 * check for opnd1/opnd2 > 1/2
186		 *
187		 * In this case n will round to 1, so 
188		 *    r = opnd1 - opnd2 
189		 */
190		if (stepcount == -1 && Sgl_isgreaterthan(opnd1,opnd2)) {
191			Sgl_all(result) = ~Sgl_all(result);   /* set sign */
192			/* align opnd2 with opnd1 */
193			Sgl_leftshiftby1(opnd2); 
194			Sgl_subtract(opnd2,opnd1,opnd2);
195			/* now normalize */
196                	while (Sgl_iszero_hidden(opnd2)) {
197                        	Sgl_leftshiftby1(opnd2);
198                        	dest_exponent--;
199			}
200			Sgl_set_exponentmantissa(result,opnd2);
201			goto testforunderflow;
202		}
203		/*
204		 * opnd1/opnd2 <= 1/2
205		 *
206		 * In this case n will round to zero, so 
207		 *    r = opnd1
208		 */
209		Sgl_set_exponentmantissa(result,opnd1);
210		dest_exponent = opnd1_exponent;
211		goto testforunderflow;
212	}
213
214	/*
215	 * Generate result
216	 *
217	 * Do iterative subtract until remainder is less than operand 2.
218	 */
219	while (stepcount-- > 0 && Sgl_all(opnd1)) {
220		if (Sgl_isnotlessthan(opnd1,opnd2))
221			Sgl_subtract(opnd1,opnd2,opnd1);
222		Sgl_leftshiftby1(opnd1);
223	}
224	/*
225	 * Do last subtract, then determine which way to round if remainder 
226	 * is exactly 1/2 of opnd2 
227	 */
228	if (Sgl_isnotlessthan(opnd1,opnd2)) {
229		Sgl_subtract(opnd1,opnd2,opnd1);
230		roundup = TRUE;
231	}
232	if (stepcount > 0 || Sgl_iszero(opnd1)) {
233		/* division is exact, remainder is zero */
234		Sgl_setzero_exponentmantissa(result);
235		*dstptr = result;
236		return(NOEXCEPTION);
237	}
238
239	/* 
240	 * Check for cases where opnd1/opnd2 < n 
241	 *
242	 * In this case the result's sign will be opposite that of
243	 * opnd1.  The mantissa also needs some correction.
244	 */
245	Sgl_leftshiftby1(opnd1);
246	if (Sgl_isgreaterthan(opnd1,opnd2)) {
247		Sgl_invert_sign(result);
248		Sgl_subtract((opnd2<<1),opnd1,opnd1);
249	}
250	/* check for remainder being exactly 1/2 of opnd2 */
251	else if (Sgl_isequal(opnd1,opnd2) && roundup) { 
252		Sgl_invert_sign(result);
253	}
254
255	/* normalize result's mantissa */
256        while (Sgl_iszero_hidden(opnd1)) {
257                dest_exponent--;
258                Sgl_leftshiftby1(opnd1);
259        }
260	Sgl_set_exponentmantissa(result,opnd1);
261
262        /* 
263         * Test for underflow
264         */
265    testforunderflow:
266	if (dest_exponent <= 0) {
267                /* trap if UNDERFLOWTRAP enabled */
268                if (Is_underflowtrap_enabled()) {
269                        /*
270                         * Adjust bias of result
271                         */
272                        Sgl_setwrapped_exponent(result,dest_exponent,unfl);
273			*dstptr = result;
274			/* frem is always exact */
275			return(UNDERFLOWEXCEPTION);
276                }
277                /*
278                 * denormalize result or set to signed zero
279                 */
280                if (dest_exponent >= (1 - SGL_P)) {
281			Sgl_rightshift_exponentmantissa(result,1-dest_exponent);
282                }
283                else {
284			Sgl_setzero_exponentmantissa(result);
285		}
286	}
287	else Sgl_set_exponent(result,dest_exponent);
288	*dstptr = result;
289	return(NOEXCEPTION);
290}