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

https://github.com/aicjofs/android_kernel_lge_v500_20d
C | 518 lines | 331 code | 24 blank | 163 comment | 69 complexity | 7229ce3f62d01d50c1380743a0daa622 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/sfadd.c		$Revision: 1.1 $
 26 *
 27 *  Purpose:
 28 *	Single_add: add two single precision values.
 29 *
 30 *  External Interfaces:
 31 *	sgl_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 "sgl_float.h"
 44
 45/*
 46 * Single_add: add two single precision values.
 47 */
 48int
 49sgl_fadd(
 50    sgl_floating_point *leftptr,
 51    sgl_floating_point *rightptr,
 52    sgl_floating_point *dstptr,
 53    unsigned int *status)
 54    {
 55    register unsigned int left, right, result, extent;
 56    register unsigned int signless_upper_left, signless_upper_right, save;
 57    
 58    
 59    register int result_exponent, right_exponent, diff_exponent;
 60    register int sign_save, jumpsize;
 61    register boolean inexact = FALSE;
 62    register boolean underflowtrap;
 63        
 64    /* Create local copies of the numbers */
 65    left = *leftptr;
 66    right = *rightptr;
 67
 68    /* A zero "save" helps discover equal operands (for later),  *
 69     * and is used in swapping operands (if needed).             */
 70    Sgl_xortointp1(left,right,/*to*/save);
 71
 72    /*
 73     * check first operand for NaN's or infinity
 74     */
 75    if ((result_exponent = Sgl_exponent(left)) == SGL_INFINITY_EXPONENT)
 76	{
 77	if (Sgl_iszero_mantissa(left)) 
 78	    {
 79	    if (Sgl_isnotnan(right)) 
 80		{
 81		if (Sgl_isinfinity(right) && save!=0) 
 82		    {
 83		    /* 
 84		     * invalid since operands are opposite signed infinity's
 85		     */
 86		    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
 87                    Set_invalidflag();
 88                    Sgl_makequietnan(result);
 89		    *dstptr = result;
 90		    return(NOEXCEPTION);
 91		    }
 92		/*
 93	 	 * return infinity
 94	 	 */
 95		*dstptr = left;
 96		return(NOEXCEPTION);
 97		}
 98	    }
 99	else 
100	    {
101            /*
102             * is NaN; signaling or quiet?
103             */
104            if (Sgl_isone_signaling(left)) 
105		{
106               	/* trap if INVALIDTRAP enabled */
107		if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
108        	/* make NaN quiet */
109        	Set_invalidflag();
110        	Sgl_set_quiet(left);
111        	}
112	    /* 
113	     * is second operand a signaling NaN? 
114	     */
115	    else if (Sgl_is_signalingnan(right)) 
116		{
117        	/* trap if INVALIDTRAP enabled */
118               	if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
119		/* make NaN quiet */
120		Set_invalidflag();
121		Sgl_set_quiet(right);
122		*dstptr = right;
123		return(NOEXCEPTION);
124		}
125	    /*
126 	     * return quiet NaN
127 	     */
128 	    *dstptr = left;
129 	    return(NOEXCEPTION);
130	    }
131	} /* End left NaN or Infinity processing */
132    /*
133     * check second operand for NaN's or infinity
134     */
135    if (Sgl_isinfinity_exponent(right)) 
136	{
137	if (Sgl_iszero_mantissa(right)) 
138	    {
139	    /* return infinity */
140	    *dstptr = right;
141	    return(NOEXCEPTION);
142	    }
143        /*
144         * is NaN; signaling or quiet?
145         */
146        if (Sgl_isone_signaling(right)) 
147	    {
148            /* trap if INVALIDTRAP enabled */
149	    if (Is_invalidtrap_enabled()) return(INVALIDEXCEPTION);
150	    /* make NaN quiet */
151	    Set_invalidflag();
152	    Sgl_set_quiet(right);
153	    }
154	/*
155	 * return quiet NaN
156 	 */
157	*dstptr = right;
158	return(NOEXCEPTION);
159    	} /* End right NaN or Infinity processing */
160
161    /* Invariant: Must be dealing with finite numbers */
162
163    /* Compare operands by removing the sign */
164    Sgl_copytoint_exponentmantissa(left,signless_upper_left);
165    Sgl_copytoint_exponentmantissa(right,signless_upper_right);
166
167    /* sign difference selects add or sub operation. */
168    if(Sgl_ismagnitudeless(signless_upper_left,signless_upper_right))
169	{
170	/* Set the left operand to the larger one by XOR swap *
171	 *  First finish the first word using "save"          */
172	Sgl_xorfromintp1(save,right,/*to*/right);
173	Sgl_xorfromintp1(save,left,/*to*/left);
174	result_exponent = Sgl_exponent(left);
175	}
176    /* Invariant:  left is not smaller than right. */ 
177
178    if((right_exponent = Sgl_exponent(right)) == 0)
179        {
180	/* Denormalized operands.  First look for zeroes */
181	if(Sgl_iszero_mantissa(right)) 
182	    {
183	    /* right is zero */
184	    if(Sgl_iszero_exponentmantissa(left))
185		{
186		/* Both operands are zeros */
187		if(Is_rounding_mode(ROUNDMINUS))
188		    {
189		    Sgl_or_signs(left,/*with*/right);
190		    }
191		else
192		    {
193		    Sgl_and_signs(left,/*with*/right);
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 = Sgl_signextendedsign(left);
205		    Sgl_leftshiftby1(left);
206		    Sgl_normalize(left,result_exponent);
207		    Sgl_set_sign(left,/*using*/sign_save);
208		    Sgl_setwrapped_exponent(left,result_exponent,unfl);
209		    *dstptr = left;
210		    return(UNDERFLOWEXCEPTION);
211		    }
212		}
213	    *dstptr = left;
214	    return(NOEXCEPTION);
215	    }
216
217	/* Neither are zeroes */
218	Sgl_clear_sign(right);	/* Exponent is already cleared */
219	if(result_exponent == 0 )
220	    {
221	    /* Both operands are denormalized.  The result must be exact
222	     * and is simply calculated.  A sum could become normalized and a
223	     * difference could cancel to a true zero. */
224	    if( (/*signed*/int) save < 0 )
225		{
226		Sgl_subtract(left,/*minus*/right,/*into*/result);
227		if(Sgl_iszero_mantissa(result))
228		    {
229		    if(Is_rounding_mode(ROUNDMINUS))
230			{
231			Sgl_setone_sign(result);
232			}
233		    else
234			{
235			Sgl_setzero_sign(result);
236			}
237		    *dstptr = result;
238		    return(NOEXCEPTION);
239		    }
240		}
241	    else
242		{
243		Sgl_addition(left,right,/*into*/result);
244		if(Sgl_isone_hidden(result))
245		    {
246		    *dstptr = result;
247		    return(NOEXCEPTION);
248		    }
249		}
250	    if(Is_underflowtrap_enabled())
251		{
252		/* need to normalize result */
253	    	sign_save = Sgl_signextendedsign(result);
254		Sgl_leftshiftby1(result);
255		Sgl_normalize(result,result_exponent);
256		Sgl_set_sign(result,/*using*/sign_save);
257                Sgl_setwrapped_exponent(result,result_exponent,unfl);
258		*dstptr = result;
259		return(UNDERFLOWEXCEPTION);
260		}
261	    *dstptr = result;
262	    return(NOEXCEPTION);
263	    }
264	right_exponent = 1;	/* Set exponent to reflect different bias
265				 * with denomalized numbers. */
266	}
267    else
268	{
269	Sgl_clear_signexponent_set_hidden(right);
270	}
271    Sgl_clear_exponent_set_hidden(left);
272    diff_exponent = result_exponent - right_exponent;
273
274    /* 
275     * Special case alignment of operands that would force alignment 
276     * beyond the extent of the extension.  A further optimization
277     * could special case this but only reduces the path length for this
278     * infrequent case.
279     */
280    if(diff_exponent > SGL_THRESHOLD)
281	{
282	diff_exponent = SGL_THRESHOLD;
283	}
284    
285    /* Align right operand by shifting to right */
286    Sgl_right_align(/*operand*/right,/*shifted by*/diff_exponent,
287     /*and lower to*/extent);
288
289    /* Treat sum and difference of the operands separately. */
290    if( (/*signed*/int) save < 0 )
291	{
292	/*
293	 * Difference of the two operands.  Their can be no overflow.  A
294	 * borrow can occur out of the hidden bit and force a post
295	 * normalization phase.
296	 */
297	Sgl_subtract_withextension(left,/*minus*/right,/*with*/extent,/*into*/result);
298	if(Sgl_iszero_hidden(result))
299	    {
300	    /* Handle normalization */
301	    /* A straightforward algorithm would now shift the result
302	     * and extension left until the hidden bit becomes one.  Not
303	     * all of the extension bits need participate in the shift.
304	     * Only the two most significant bits (round and guard) are
305	     * needed.  If only a single shift is needed then the guard
306	     * bit becomes a significant low order bit and the extension
307	     * must participate in the rounding.  If more than a single 
308	     * shift is needed, then all bits to the right of the guard 
309	     * bit are zeros, and the guard bit may or may not be zero. */
310	    sign_save = Sgl_signextendedsign(result);
311            Sgl_leftshiftby1_withextent(result,extent,result);
312
313            /* Need to check for a zero result.  The sign and exponent
314	     * fields have already been zeroed.  The more efficient test
315	     * of the full object can be used.
316	     */
317    	    if(Sgl_iszero(result))
318		/* Must have been "x-x" or "x+(-x)". */
319		{
320		if(Is_rounding_mode(ROUNDMINUS)) Sgl_setone_sign(result);
321		*dstptr = result;
322		return(NOEXCEPTION);
323		}
324	    result_exponent--;
325	    /* Look to see if normalization is finished. */
326	    if(Sgl_isone_hidden(result))
327		{
328		if(result_exponent==0)
329		    {
330		    /* Denormalized, exponent should be zero.  Left operand *
331 		     * was normalized, so extent (guard, round) was zero    */
332		    goto underflow;
333		    }
334		else
335		    {
336		    /* No further normalization is needed. */
337		    Sgl_set_sign(result,/*using*/sign_save);
338	    	    Ext_leftshiftby1(extent);
339		    goto round;
340		    }
341		}
342
343	    /* Check for denormalized, exponent should be zero.  Left    * 
344	     * operand was normalized, so extent (guard, round) was zero */
345	    if(!(underflowtrap = Is_underflowtrap_enabled()) &&
346	       result_exponent==0) goto underflow;
347
348	    /* Shift extension to complete one bit of normalization and
349	     * update exponent. */
350	    Ext_leftshiftby1(extent);
351
352	    /* Discover first one bit to determine shift amount.  Use a
353	     * modified binary search.  We have already shifted the result
354	     * one position right and still not found a one so the remainder
355	     * of the extension must be zero and simplifies rounding. */
356	    /* Scan bytes */
357	    while(Sgl_iszero_hiddenhigh7mantissa(result))
358		{
359		Sgl_leftshiftby8(result);
360		if((result_exponent -= 8) <= 0  && !underflowtrap)
361		    goto underflow;
362		}
363	    /* Now narrow it down to the nibble */
364	    if(Sgl_iszero_hiddenhigh3mantissa(result))
365		{
366		/* The lower nibble contains the normalizing one */
367		Sgl_leftshiftby4(result);
368		if((result_exponent -= 4) <= 0 && !underflowtrap)
369		    goto underflow;
370		}
371	    /* Select case were first bit is set (already normalized)
372	     * otherwise select the proper shift. */
373	    if((jumpsize = Sgl_hiddenhigh3mantissa(result)) > 7)
374		{
375		/* Already normalized */
376		if(result_exponent <= 0) goto underflow;
377		Sgl_set_sign(result,/*using*/sign_save);
378		Sgl_set_exponent(result,/*using*/result_exponent);
379		*dstptr = result;
380		return(NOEXCEPTION);
381		}
382	    Sgl_sethigh4bits(result,/*using*/sign_save);
383	    switch(jumpsize) 
384		{
385		case 1:
386		    {
387		    Sgl_leftshiftby3(result);
388		    result_exponent -= 3;
389		    break;
390		    }
391		case 2:
392		case 3:
393		    {
394		    Sgl_leftshiftby2(result);
395		    result_exponent -= 2;
396		    break;
397		    }
398		case 4:
399		case 5:
400		case 6:
401		case 7:
402		    {
403		    Sgl_leftshiftby1(result);
404		    result_exponent -= 1;
405		    break;
406		    }
407		}
408	    if(result_exponent > 0) 
409		{
410		Sgl_set_exponent(result,/*using*/result_exponent);
411		*dstptr = result;
412		return(NOEXCEPTION); /* Sign bit is already set */
413		}
414	    /* Fixup potential underflows */
415	  underflow:
416	    if(Is_underflowtrap_enabled())
417		{
418		Sgl_set_sign(result,sign_save);
419                Sgl_setwrapped_exponent(result,result_exponent,unfl);
420		*dstptr = result;
421		/* inexact = FALSE; */
422		return(UNDERFLOWEXCEPTION);
423		}
424	    /* 
425	     * Since we cannot get an inexact denormalized result,
426	     * we can now return.
427	     */
428	    Sgl_right_align(result,/*by*/(1-result_exponent),extent);
429	    Sgl_clear_signexponent(result);
430	    Sgl_set_sign(result,sign_save);
431	    *dstptr = result;
432	    return(NOEXCEPTION);
433	    } /* end if(hidden...)... */
434	/* Fall through and round */
435	} /* end if(save < 0)... */
436    else 
437	{
438	/* Add magnitudes */
439	Sgl_addition(left,right,/*to*/result);
440	if(Sgl_isone_hiddenoverflow(result))
441	    {
442	    /* Prenormalization required. */
443	    Sgl_rightshiftby1_withextent(result,extent,extent);
444	    Sgl_arithrightshiftby1(result);
445	    result_exponent++;
446	    } /* end if hiddenoverflow... */
447	} /* end else ...add magnitudes... */
448    
449    /* Round the result.  If the extension is all zeros,then the result is
450     * exact.  Otherwise round in the correct direction.  No underflow is
451     * possible. If a postnormalization is necessary, then the mantissa is
452     * all zeros so no shift is needed. */
453  round:
454    if(Ext_isnotzero(extent))
455	{
456	inexact = TRUE;
457	switch(Rounding_mode())
458	    {
459	    case ROUNDNEAREST: /* The default. */
460	    if(Ext_isone_sign(extent))
461		{
462		/* at least 1/2 ulp */
463		if(Ext_isnotzero_lower(extent)  ||
464		  Sgl_isone_lowmantissa(result))
465		    {
466		    /* either exactly half way and odd or more than 1/2ulp */
467		    Sgl_increment(result);
468		    }
469		}
470	    break;
471
472	    case ROUNDPLUS:
473	    if(Sgl_iszero_sign(result))
474		{
475		/* Round up positive results */
476		Sgl_increment(result);
477		}
478	    break;
479	    
480	    case ROUNDMINUS:
481	    if(Sgl_isone_sign(result))
482		{
483		/* Round down negative results */
484		Sgl_increment(result);
485		}
486	    
487	    case ROUNDZERO:;
488	    /* truncate is simple */
489	    } /* end switch... */
490	if(Sgl_isone_hiddenoverflow(result)) result_exponent++;
491	}
492    if(result_exponent == SGL_INFINITY_EXPONENT)
493        {
494        /* Overflow */
495        if(Is_overflowtrap_enabled())
496	    {
497	    Sgl_setwrapped_exponent(result,result_exponent,ovfl);
498	    *dstptr = result;
499	    if (inexact)
500		if (Is_inexacttrap_enabled())
501		    return(OVERFLOWEXCEPTION | INEXACTEXCEPTION);
502		else Set_inexactflag();
503	    return(OVERFLOWEXCEPTION);
504	    }
505        else
506	    {
507	    Set_overflowflag();
508	    inexact = TRUE;
509	    Sgl_setoverflow(result);
510	    }
511	}
512    else Sgl_set_exponent(result,result_exponent);
513    *dstptr = result;
514    if(inexact) 
515	if(Is_inexacttrap_enabled()) return(INEXACTEXCEPTION);
516	else Set_inexactflag();
517    return(NOEXCEPTION);
518    }