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

https://github.com/aicjofs/android_kernel_lge_v500_20d
C | 524 lines | 336 code | 23 blank | 165 comment | 69 complexity | 4c8963783eb47ae57e1c6aa6f6d3fc89 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/dfadd.c		$Revision: 1.1 $
 26 *
 27 *  Purpose:
 28 *	Double_add: add two double precision values.
 29 *
 30 *  External Interfaces:
 31 *	dbl_fadd(leftptr, rightptr, 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#include "float.h"
 43#include "dbl_float.h"
 44
 45/*
 46 * Double_add: add two double precision values.
 47 */
 48dbl_fadd(
 49    dbl_floating_point *leftptr,
 50    dbl_floating_point *rightptr,
 51    dbl_floating_point *dstptr,
 52    unsigned int *status)
 53{
 54    register unsigned int signless_upper_left, signless_upper_right, save;
 55    register unsigned int leftp1, leftp2, rightp1, rightp2, extent;
 56    register unsigned int resultp1 = 0, resultp2 = 0;
 57    
 58    register int result_exponent, right_exponent, diff_exponent;
 59    register int sign_save, jumpsize;
 60    register boolean inexact = FALSE;
 61    register boolean underflowtrap;
 62        
 63    /* Create local copies of the numbers */
 64    Dbl_copyfromptr(leftptr,leftp1,leftp2);
 65    Dbl_copyfromptr(rightptr,rightp1,rightp2);
 66
 67    /* A zero "save" helps discover equal operands (for later),  *
 68     * and is used in swapping operands (if needed).             */
 69    Dbl_xortointp1(leftp1,rightp1,/*to*/save);
 70
 71    /*
 72     * check first operand for NaN's or infinity
 73     */
 74    if ((result_exponent = Dbl_exponent(leftp1)) == DBL_INFINITY_EXPONENT)
 75	{
 76	if (Dbl_iszero_mantissa(leftp1,leftp2)) 
 77	    {
 78	    if (Dbl_isnotnan(rightp1,rightp2)) 
 79		{
 80		if (Dbl_isinfinity(rightp1,rightp2) && save!=0) 
 81		    {
 82		    /* 
 83		     * invalid since operands are opposite signed infinity's
 84		     */
 85		    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
 86                    Set_invalidflag();
 87                    Dbl_makequietnan(resultp1,resultp2);
 88		    Dbl_copytoptr(resultp1,resultp2,dstptr);
 89		    return(NOEXCEPTION);
 90		    }
 91		/*
 92	 	 * return infinity
 93	 	 */
 94		Dbl_copytoptr(leftp1,leftp2,dstptr);
 95		return(NOEXCEPTION);
 96		}
 97	    }
 98	else 
 99	    {
100            /*
101             * is NaN; signaling or quiet?
102             */
103            if (Dbl_isone_signaling(leftp1)) 
104		{
105               	/* trap if INVALIDTRAP enabled */
106		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
107        	/* make NaN quiet */
108        	Set_invalidflag();
109        	Dbl_set_quiet(leftp1);
110        	}
111	    /* 
112	     * is second operand a signaling NaN? 
113	     */
114	    else if (Dbl_is_signalingnan(rightp1)) 
115		{
116        	/* trap if INVALIDTRAP enabled */
117               	if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
118		/* make NaN quiet */
119		Set_invalidflag();
120		Dbl_set_quiet(rightp1);
121		Dbl_copytoptr(rightp1,rightp2,dstptr);
122		return(NOEXCEPTION);
123		}
124	    /*
125 	     * return quiet NaN
126 	     */
127	    Dbl_copytoptr(leftp1,leftp2,dstptr);
128 	    return(NOEXCEPTION);
129	    }
130	} /* End left NaN or Infinity processing */
131    /*
132     * check second operand for NaN's or infinity
133     */
134    if (Dbl_isinfinity_exponent(rightp1)) 
135	{
136	if (Dbl_iszero_mantissa(rightp1,rightp2)) 
137	    {
138	    /* return infinity */
139	    Dbl_copytoptr(rightp1,rightp2,dstptr);
140	    return(NOEXCEPTION);
141	    }
142        /*
143         * is NaN; signaling or quiet?
144         */
145        if (Dbl_isone_signaling(rightp1)) 
146	    {
147            /* trap if INVALIDTRAP enabled */
148	    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
149	    /* make NaN quiet */
150	    Set_invalidflag();
151	    Dbl_set_quiet(rightp1);
152	    }
153	/*
154	 * return quiet NaN
155 	 */
156	Dbl_copytoptr(rightp1,rightp2,dstptr);
157	return(NOEXCEPTION);
158    	} /* End right NaN or Infinity processing */
159
160    /* Invariant: Must be dealing with finite numbers */
161
162    /* Compare operands by removing the sign */
163    Dbl_copytoint_exponentmantissap1(leftp1,signless_upper_left);
164    Dbl_copytoint_exponentmantissap1(rightp1,signless_upper_right);
165
166    /* sign difference selects add or sub operation. */
167    if(Dbl_ismagnitudeless(leftp2,rightp2,signless_upper_left,signless_upper_right))
168	{
169	/* Set the left operand to the larger one by XOR swap *
170	 *  First finish the first word using "save"          */
171	Dbl_xorfromintp1(save,rightp1,/*to*/rightp1);
172	Dbl_xorfromintp1(save,leftp1,/*to*/leftp1);
173     	Dbl_swap_lower(leftp2,rightp2);
174	result_exponent = Dbl_exponent(leftp1);
175	}
176    /* Invariant:  left is not smaller than right. */ 
177
178    if((right_exponent = Dbl_exponent(rightp1)) == 0)
179        {
180	/* Denormalized operands.  First look for zeroes */
181	if(Dbl_iszero_mantissa(rightp1,rightp2)) 
182	    {
183	    /* right is zero */
184	    if(Dbl_iszero_exponentmantissa(leftp1,leftp2))
185		{
186		/* Both operands are zeros */
187		if(Is_rounding_mode(ROUNDMINUS))
188		    {
189		    Dbl_or_signs(leftp1,/*with*/rightp1);
190		    }
191		else
192		    {
193		    Dbl_and_signs(leftp1,/*with*/rightp1);
194		    }
195		}
196	    else 
197		{
198		/* Left is not a zero and must be the result.  Trapped
199		 * underflows are signaled if left is denormalized.  Result
200		 * is always exact. */
201		if( (result_exponent == 0) && Is_underflowtrap_enabled() )
202		    {
203		    /* need to normalize results mantissa */
204	    	    sign_save = Dbl_signextendedsign(leftp1);
205		    Dbl_leftshiftby1(leftp1,leftp2);
206		    Dbl_normalize(leftp1,leftp2,result_exponent);
207		    Dbl_set_sign(leftp1,/*using*/sign_save);
208                    Dbl_setwrapped_exponent(leftp1,result_exponent,unfl);
209		    Dbl_copytoptr(leftp1,leftp2,dstptr);
210		    /* inexact = FALSE */
211		    return(UNDERFLOWEXCEPTION);
212		    }
213		}
214	    Dbl_copytoptr(leftp1,leftp2,dstptr);
215	    return(NOEXCEPTION);
216	    }
217
218	/* Neither are zeroes */
219	Dbl_clear_sign(rightp1);	/* Exponent is already cleared */
220	if(result_exponent == 0 )
221	    {
222	    /* Both operands are denormalized.  The result must be exact
223	     * and is simply calculated.  A sum could become normalized and a
224	     * difference could cancel to a true zero. */
225	    if( (/*signed*/int) save < 0 )
226		{
227		Dbl_subtract(leftp1,leftp2,/*minus*/rightp1,rightp2,
228		/*into*/resultp1,resultp2);
229		if(Dbl_iszero_mantissa(resultp1,resultp2))
230		    {
231		    if(Is_rounding_mode(ROUNDMINUS))
232			{
233			Dbl_setone_sign(resultp1);
234			}
235		    else
236			{
237			Dbl_setzero_sign(resultp1);
238			}
239		    Dbl_copytoptr(resultp1,resultp2,dstptr);
240		    return(NOEXCEPTION);
241		    }
242		}
243	    else
244		{
245		Dbl_addition(leftp1,leftp2,rightp1,rightp2,
246		/*into*/resultp1,resultp2);
247		if(Dbl_isone_hidden(resultp1))
248		    {
249		    Dbl_copytoptr(resultp1,resultp2,dstptr);
250		    return(NOEXCEPTION);
251		    }
252		}
253	    if(Is_underflowtrap_enabled())
254		{
255		/* need to normalize result */
256	    	sign_save = Dbl_signextendedsign(resultp1);
257		Dbl_leftshiftby1(resultp1,resultp2);
258		Dbl_normalize(resultp1,resultp2,result_exponent);
259		Dbl_set_sign(resultp1,/*using*/sign_save);
260                Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
261	        Dbl_copytoptr(resultp1,resultp2,dstptr);
262		/* inexact = FALSE */
263	        return(UNDERFLOWEXCEPTION);
264		}
265	    Dbl_copytoptr(resultp1,resultp2,dstptr);
266	    return(NOEXCEPTION);
267	    }
268	right_exponent = 1;	/* Set exponent to reflect different bias
269				 * with denomalized numbers. */
270	}
271    else
272	{
273	Dbl_clear_signexponent_set_hidden(rightp1);
274	}
275    Dbl_clear_exponent_set_hidden(leftp1);
276    diff_exponent = result_exponent - right_exponent;
277
278    /* 
279     * Special case alignment of operands that would force alignment 
280     * beyond the extent of the extension.  A further optimization
281     * could special case this but only reduces the path length for this
282     * infrequent case.
283     */
284    if(diff_exponent > DBL_THRESHOLD)
285	{
286	diff_exponent = DBL_THRESHOLD;
287	}
288    
289    /* Align right operand by shifting to right */
290    Dbl_right_align(/*operand*/rightp1,rightp2,/*shifted by*/diff_exponent,
291    /*and lower to*/extent);
292
293    /* Treat sum and difference of the operands separately. */
294    if( (/*signed*/int) save < 0 )
295	{
296	/*
297	 * Difference of the two operands.  Their can be no overflow.  A
298	 * borrow can occur out of the hidden bit and force a post
299	 * normalization phase.
300	 */
301	Dbl_subtract_withextension(leftp1,leftp2,/*minus*/rightp1,rightp2,
302	/*with*/extent,/*into*/resultp1,resultp2);
303	if(Dbl_iszero_hidden(resultp1))
304	    {
305	    /* Handle normalization */
306	    /* A straight forward algorithm would now shift the result
307	     * and extension left until the hidden bit becomes one.  Not
308	     * all of the extension bits need participate in the shift.
309	     * Only the two most significant bits (round and guard) are
310	     * needed.  If only a single shift is needed then the guard
311	     * bit becomes a significant low order bit and the extension
312	     * must participate in the rounding.  If more than a single 
313	     * shift is needed, then all bits to the right of the guard 
314	     * bit are zeros, and the guard bit may or may not be zero. */
315	    sign_save = Dbl_signextendedsign(resultp1);
316            Dbl_leftshiftby1_withextent(resultp1,resultp2,extent,resultp1,resultp2);
317
318            /* Need to check for a zero result.  The sign and exponent
319	     * fields have already been zeroed.  The more efficient test
320	     * of the full object can be used.
321	     */
322    	    if(Dbl_iszero(resultp1,resultp2))
323		/* Must have been "x-x" or "x+(-x)". */
324		{
325		if(Is_rounding_mode(ROUNDMINUS)) Dbl_setone_sign(resultp1);
326		Dbl_copytoptr(resultp1,resultp2,dstptr);
327		return(NOEXCEPTION);
328		}
329	    result_exponent--;
330	    /* Look to see if normalization is finished. */
331	    if(Dbl_isone_hidden(resultp1))
332		{
333		if(result_exponent==0)
334		    {
335		    /* Denormalized, exponent should be zero.  Left operand *
336		     * was normalized, so extent (guard, round) was zero    */
337		    goto underflow;
338		    }
339		else
340		    {
341		    /* No further normalization is needed. */
342		    Dbl_set_sign(resultp1,/*using*/sign_save);
343	    	    Ext_leftshiftby1(extent);
344		    goto round;
345		    }
346		}
347
348	    /* Check for denormalized, exponent should be zero.  Left    *
349	     * operand was normalized, so extent (guard, round) was zero */
350	    if(!(underflowtrap = Is_underflowtrap_enabled()) &&
351	       result_exponent==0) goto underflow;
352
353	    /* Shift extension to complete one bit of normalization and
354	     * update exponent. */
355	    Ext_leftshiftby1(extent);
356
357	    /* Discover first one bit to determine shift amount.  Use a
358	     * modified binary search.  We have already shifted the result
359	     * one position right and still not found a one so the remainder
360	     * of the extension must be zero and simplifies rounding. */
361	    /* Scan bytes */
362	    while(Dbl_iszero_hiddenhigh7mantissa(resultp1))
363		{
364		Dbl_leftshiftby8(resultp1,resultp2);
365		if((result_exponent -= 8) <= 0  && !underflowtrap)
366		    goto underflow;
367		}
368	    /* Now narrow it down to the nibble */
369	    if(Dbl_iszero_hiddenhigh3mantissa(resultp1))
370		{
371		/* The lower nibble contains the normalizing one */
372		Dbl_leftshiftby4(resultp1,resultp2);
373		if((result_exponent -= 4) <= 0 && !underflowtrap)
374		    goto underflow;
375		}
376	    /* Select case were first bit is set (already normalized)
377	     * otherwise select the proper shift. */
378	    if((jumpsize = Dbl_hiddenhigh3mantissa(resultp1)) > 7)
379		{
380		/* Already normalized */
381		if(result_exponent <= 0) goto underflow;
382		Dbl_set_sign(resultp1,/*using*/sign_save);
383		Dbl_set_exponent(resultp1,/*using*/result_exponent);
384		Dbl_copytoptr(resultp1,resultp2,dstptr);
385		return(NOEXCEPTION);
386		}
387	    Dbl_sethigh4bits(resultp1,/*using*/sign_save);
388	    switch(jumpsize) 
389		{
390		case 1:
391		    {
392		    Dbl_leftshiftby3(resultp1,resultp2);
393		    result_exponent -= 3;
394		    break;
395		    }
396		case 2:
397		case 3:
398		    {
399		    Dbl_leftshiftby2(resultp1,resultp2);
400		    result_exponent -= 2;
401		    break;
402		    }
403		case 4:
404		case 5:
405		case 6:
406		case 7:
407		    {
408		    Dbl_leftshiftby1(resultp1,resultp2);
409		    result_exponent -= 1;
410		    break;
411		    }
412		}
413	    if(result_exponent > 0) 
414		{
415		Dbl_set_exponent(resultp1,/*using*/result_exponent);
416		Dbl_copytoptr(resultp1,resultp2,dstptr);
417		return(NOEXCEPTION); 	/* Sign bit is already set */
418		}
419	    /* Fixup potential underflows */
420	  underflow:
421	    if(Is_underflowtrap_enabled())
422		{
423		Dbl_set_sign(resultp1,sign_save);
424                Dbl_setwrapped_exponent(resultp1,result_exponent,unfl);
425		Dbl_copytoptr(resultp1,resultp2,dstptr);
426		/* inexact = FALSE */
427		return(UNDERFLOWEXCEPTION);
428		}
429	    /* 
430	     * Since we cannot get an inexact denormalized result,
431	     * we can now return.
432	     */
433	    Dbl_fix_overshift(resultp1,resultp2,(1-result_exponent),extent);
434	    Dbl_clear_signexponent(resultp1);
435	    Dbl_set_sign(resultp1,sign_save);
436	    Dbl_copytoptr(resultp1,resultp2,dstptr);
437	    return(NOEXCEPTION);
438	    } /* end if(hidden...)... */
439	/* Fall through and round */
440	} /* end if(save < 0)... */
441    else 
442	{
443	/* Add magnitudes */
444	Dbl_addition(leftp1,leftp2,rightp1,rightp2,/*to*/resultp1,resultp2);
445	if(Dbl_isone_hiddenoverflow(resultp1))
446	    {
447	    /* Prenormalization required. */
448	    Dbl_rightshiftby1_withextent(resultp2,extent,extent);
449	    Dbl_arithrightshiftby1(resultp1,resultp2);
450	    result_exponent++;
451	    } /* end if hiddenoverflow... */
452	} /* end else ...add magnitudes... */
453    
454    /* Round the result.  If the extension is all zeros,then the result is
455     * exact.  Otherwise round in the correct direction.  No underflow is
456     * possible. If a postnormalization is necessary, then the mantissa is
457     * all zeros so no shift is needed. */
458  round:
459    if(Ext_isnotzero(extent))
460	{
461	inexact = TRUE;
462	switch(Rounding_mode())
463	    {
464	    case ROUNDNEAREST: /* The default. */
465	    if(Ext_isone_sign(extent))
466		{
467		/* at least 1/2 ulp */
468		if(Ext_isnotzero_lower(extent)  ||
469		  Dbl_isone_lowmantissap2(resultp2))
470		    {
471		    /* either exactly half way and odd or more than 1/2ulp */
472		    Dbl_increment(resultp1,resultp2);
473		    }
474		}
475	    break;
476
477	    case ROUNDPLUS:
478	    if(Dbl_iszero_sign(resultp1))
479		{
480		/* Round up positive results */
481		Dbl_increment(resultp1,resultp2);
482		}
483	    break;
484	    
485	    case ROUNDMINUS:
486	    if(Dbl_isone_sign(resultp1))
487		{
488		/* Round down negative results */
489		Dbl_increment(resultp1,resultp2);
490		}
491	    
492	    case ROUNDZERO:;
493	    /* truncate is simple */
494	    } /* end switch... */
495	if(Dbl_isone_hiddenoverflow(resultp1)) result_exponent++;
496	}
497    if(result_exponent == DBL_INFINITY_EXPONENT)
498        {
499        /* Overflow */
500        if(Is_overflowtrap_enabled())
501	    {
502	    Dbl_setwrapped_exponent(resultp1,result_exponent,ovfl);
503	    Dbl_copytoptr(resultp1,resultp2,dstptr);
504	    if (inexact)
505		if (Is_inexacttrap_enabled())
506			return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
507		else Set_inexactflag();
508	    return(OVERFLOWEXCEPTION);
509	    }
510        else
511	    {
512	    inexact = TRUE;
513	    Set_overflowflag();
514	    Dbl_setoverflow(resultp1,resultp2);
515	    }
516	}
517    else Dbl_set_exponent(resultp1,result_exponent);
518    Dbl_copytoptr(resultp1,resultp2,dstptr);
519    if(inexact) 
520	if(Is_inexacttrap_enabled())
521	    return(INEXACTEXCEPTION);
522	else Set_inexactflag();
523    return(NOEXCEPTION);
524}