xref: /openbmc/qemu/libdecnumber/dpd/decimal32.c (revision 09125c5e)
1 /* Decimal 32-bit format module for the decNumber C Library.
2    Copyright (C) 2005, 2007 Free Software Foundation, Inc.
3    Contributed by IBM Corporation.  Author Mike Cowlishaw.
4 
5    This file is part of GCC.
6 
7    GCC is free software; you can redistribute it and/or modify it under
8    the terms of the GNU General Public License as published by the Free
9    Software Foundation; either version 2, or (at your option) any later
10    version.
11 
12    In addition to the permissions in the GNU General Public License,
13    the Free Software Foundation gives you unlimited permission to link
14    the compiled version of this file into combinations with other
15    programs, and to distribute those combinations without any
16    restriction coming from the use of this file.  (The General Public
17    License restrictions do apply in other respects; for example, they
18    cover modification of the file, and distribution when not linked
19    into a combine executable.)
20 
21    GCC is distributed in the hope that it will be useful, but WITHOUT ANY
22    WARRANTY; without even the implied warranty of MERCHANTABILITY or
23    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
24    for more details.
25 
26    You should have received a copy of the GNU General Public License
27    along with GCC; see the file COPYING.  If not, write to the Free
28    Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
29    02110-1301, USA.  */
30 
31 /* ------------------------------------------------------------------ */
32 /* Decimal 32-bit format module					      */
33 /* ------------------------------------------------------------------ */
34 /* This module comprises the routines for decimal32 format numbers.   */
35 /* Conversions are supplied to and from decNumber and String.	      */
36 /*								      */
37 /* This is used when decNumber provides operations, either for all    */
38 /* operations or as a proxy between decNumber and decSingle.	      */
39 /*								      */
40 /* Error handling is the same as decNumber (qv.).		      */
41 /* ------------------------------------------------------------------ */
42 #include "qemu/osdep.h"
43 
44 #include "libdecnumber/dconfig.h"
45 #define	 DECNUMDIGITS  7      /* make decNumbers with space for 7 */
46 #include "libdecnumber/decNumber.h"
47 #include "libdecnumber/decNumberLocal.h"
48 #include "libdecnumber/dpd/decimal32.h"
49 
50 /* Utility tables and routines [in decimal64.c] */
51 extern const uInt   COMBEXP[32], COMBMSD[32];
52 extern const uByte  BIN2CHAR[4001];
53 
54 extern void decDigitsToDPD(const decNumber *, uInt *, Int);
55 extern void decDigitsFromDPD(decNumber *, const uInt *, Int);
56 
57 #if DECTRACE || DECCHECK
58 void decimal32Show(const decimal32 *);		  /* for debug */
59 extern void decNumberShow(const decNumber *);	  /* .. */
60 #endif
61 
62 /* Useful macro */
63 /* Clear a structure (e.g., a decNumber) */
64 #define DEC_clear(d) memset(d, 0, sizeof(*d))
65 
66 /* ------------------------------------------------------------------ */
67 /* decimal32FromNumber -- convert decNumber to decimal32	      */
68 /*								      */
69 /*   ds is the target decimal32					      */
70 /*   dn is the source number (assumed valid)			      */
71 /*   set is the context, used only for reporting errors		      */
72 /*								      */
73 /* The set argument is used only for status reporting and for the     */
74 /* rounding mode (used if the coefficient is more than DECIMAL32_Pmax */
75 /* digits or an overflow is detected).	If the exponent is out of the */
76 /* valid range then Overflow or Underflow will be raised.	      */
77 /* After Underflow a subnormal result is possible.		      */
78 /*								      */
79 /* DEC_Clamped is set if the number has to be 'folded down' to fit,   */
80 /* by reducing its exponent and multiplying the coefficient by a      */
81 /* power of ten, or if the exponent on a zero had to be clamped.      */
82 /* ------------------------------------------------------------------ */
decimal32FromNumber(decimal32 * d32,const decNumber * dn,decContext * set)83 decimal32 * decimal32FromNumber(decimal32 *d32, const decNumber *dn,
84 			      decContext *set) {
85   uInt status=0;		   /* status accumulator */
86   Int ae;			   /* adjusted exponent */
87   decNumber  dw;		   /* work */
88   decContext dc;		   /* .. */
89   uInt *pu;			   /* .. */
90   uInt comb, exp;		   /* .. */
91   uInt targ=0;			   /* target 32-bit */
92 
93   /* If the number has too many digits, or the exponent could be */
94   /* out of range then reduce the number under the appropriate */
95   /* constraints.  This could push the number to Infinity or zero, */
96   /* so this check and rounding must be done before generating the */
97   /* decimal32] */
98   ae=dn->exponent+dn->digits-1;		     /* [0 if special] */
99   if (dn->digits>DECIMAL32_Pmax		     /* too many digits */
100    || ae>DECIMAL32_Emax			     /* likely overflow */
101    || ae<DECIMAL32_Emin) {		     /* likely underflow */
102     decContextDefault(&dc, DEC_INIT_DECIMAL32); /* [no traps] */
103     dc.round=set->round;		     /* use supplied rounding */
104     decNumberPlus(&dw, dn, &dc);	     /* (round and check) */
105     /* [this changes -0 to 0, so enforce the sign...] */
106     dw.bits|=dn->bits&DECNEG;
107     status=dc.status;			     /* save status */
108     dn=&dw;				     /* use the work number */
109     } /* maybe out of range */
110 
111   if (dn->bits&DECSPECIAL) {			  /* a special value */
112     if (dn->bits&DECINF) targ=DECIMAL_Inf<<24;
113      else {					  /* sNaN or qNaN */
114       if ((*dn->lsu!=0 || dn->digits>1)		  /* non-zero coefficient */
115        && (dn->digits<DECIMAL32_Pmax)) {	  /* coefficient fits */
116 	decDigitsToDPD(dn, &targ, 0);
117 	}
118       if (dn->bits&DECNAN) targ|=DECIMAL_NaN<<24;
119        else targ|=DECIMAL_sNaN<<24;
120       } /* a NaN */
121     } /* special */
122 
123    else { /* is finite */
124     if (decNumberIsZero(dn)) {		     /* is a zero */
125       /* set and clamp exponent */
126       if (dn->exponent<-DECIMAL32_Bias) {
127 	exp=0;				     /* low clamp */
128 	status|=DEC_Clamped;
129 	}
130        else {
131 	exp=dn->exponent+DECIMAL32_Bias;     /* bias exponent */
132 	if (exp>DECIMAL32_Ehigh) {	     /* top clamp */
133 	  exp=DECIMAL32_Ehigh;
134 	  status|=DEC_Clamped;
135 	  }
136 	}
137       comb=(exp>>3) & 0x18;		/* msd=0, exp top 2 bits .. */
138       }
139      else {				/* non-zero finite number */
140       uInt msd;				/* work */
141       Int pad=0;			/* coefficient pad digits */
142 
143       /* the dn is known to fit, but it may need to be padded */
144       exp=(uInt)(dn->exponent+DECIMAL32_Bias);	  /* bias exponent */
145       if (exp>DECIMAL32_Ehigh) {		  /* fold-down case */
146 	pad=exp-DECIMAL32_Ehigh;
147 	exp=DECIMAL32_Ehigh;			  /* [to maximum] */
148 	status|=DEC_Clamped;
149 	}
150 
151       /* fastpath common case */
152       if (DECDPUN==3 && pad==0) {
153 	targ=BIN2DPD[dn->lsu[0]];
154 	if (dn->digits>3) targ|=(uInt)(BIN2DPD[dn->lsu[1]])<<10;
155 	msd=(dn->digits==7 ? dn->lsu[2] : 0);
156 	}
157        else { /* general case */
158 	decDigitsToDPD(dn, &targ, pad);
159 	/* save and clear the top digit */
160 	msd=targ>>20;
161 	targ&=0x000fffff;
162 	}
163 
164       /* create the combination field */
165       if (msd>=8) comb=0x18 | ((exp>>5) & 0x06) | (msd & 0x01);
166 	     else comb=((exp>>3) & 0x18) | msd;
167       }
168     targ|=comb<<26;		   /* add combination field .. */
169     targ|=(exp&0x3f)<<20;	   /* .. and exponent continuation */
170     } /* finite */
171 
172   if (dn->bits&DECNEG) targ|=0x80000000;  /* add sign bit */
173 
174   /* now write to storage; this is endian */
175   pu=(uInt *)d32->bytes;	   /* overlay */
176   *pu=targ;			   /* directly store the int */
177 
178   if (status!=0) decContextSetStatus(set, status); /* pass on status */
179   /* decimal32Show(d32); */
180   return d32;
181   } /* decimal32FromNumber */
182 
183 /* ------------------------------------------------------------------ */
184 /* decimal32ToNumber -- convert decimal32 to decNumber		      */
185 /*   d32 is the source decimal32				      */
186 /*   dn is the target number, with appropriate space		      */
187 /* No error is possible.					      */
188 /* ------------------------------------------------------------------ */
decimal32ToNumber(const decimal32 * d32,decNumber * dn)189 decNumber * decimal32ToNumber(const decimal32 *d32, decNumber *dn) {
190   uInt msd;			   /* coefficient MSD */
191   uInt exp;			   /* exponent top two bits */
192   uInt comb;			   /* combination field */
193   uInt sour;			   /* source 32-bit */
194   const uInt *pu;		   /* work */
195 
196   /* load source from storage; this is endian */
197   pu=(const uInt *)d32->bytes;	   /* overlay */
198   sour=*pu;			   /* directly load the int */
199 
200   comb=(sour>>26)&0x1f;		   /* combination field */
201 
202   decNumberZero(dn);		   /* clean number */
203   if (sour&0x80000000) dn->bits=DECNEG; /* set sign if negative */
204 
205   msd=COMBMSD[comb];		   /* decode the combination field */
206   exp=COMBEXP[comb];		   /* .. */
207 
208   if (exp==3) {			   /* is a special */
209     if (msd==0) {
210       dn->bits|=DECINF;
211       return dn;		   /* no coefficient needed */
212       }
213     else if (sour&0x02000000) dn->bits|=DECSNAN;
214     else dn->bits|=DECNAN;
215     msd=0;			   /* no top digit */
216     }
217    else {			   /* is a finite number */
218     dn->exponent=(exp<<6)+((sour>>20)&0x3f)-DECIMAL32_Bias; /* unbiased */
219     }
220 
221   /* get the coefficient */
222   sour&=0x000fffff;		   /* clean coefficient continuation */
223   if (msd) {			   /* non-zero msd */
224     sour|=msd<<20;		   /* prefix to coefficient */
225     decDigitsFromDPD(dn, &sour, 3); /* process 3 declets */
226     return dn;
227     }
228   /* msd=0 */
229   if (!sour) return dn;		   /* easy: coefficient is 0 */
230   if (sour&0x000ffc00)		   /* need 2 declets? */
231     decDigitsFromDPD(dn, &sour, 2); /* process 2 declets */
232    else
233     decDigitsFromDPD(dn, &sour, 1); /* process 1 declet */
234   return dn;
235   } /* decimal32ToNumber */
236 
237 /* ------------------------------------------------------------------ */
238 /* to-scientific-string -- conversion to numeric string		      */
239 /* to-engineering-string -- conversion to numeric string	      */
240 /*								      */
241 /*   decimal32ToString(d32, string);				      */
242 /*   decimal32ToEngString(d32, string);				      */
243 /*								      */
244 /*  d32 is the decimal32 format number to convert		      */
245 /*  string is the string where the result will be laid out	      */
246 /*								      */
247 /*  string must be at least 24 characters			      */
248 /*								      */
249 /*  No error is possible, and no status can be set.		      */
250 /* ------------------------------------------------------------------ */
decimal32ToEngString(const decimal32 * d32,char * string)251 char * decimal32ToEngString(const decimal32 *d32, char *string){
252   decNumber dn;				/* work */
253   decimal32ToNumber(d32, &dn);
254   decNumberToEngString(&dn, string);
255   return string;
256   } /* decimal32ToEngString */
257 
decimal32ToString(const decimal32 * d32,char * string)258 char * decimal32ToString(const decimal32 *d32, char *string){
259   uInt msd;			   /* coefficient MSD */
260   Int  exp;			   /* exponent top two bits or full */
261   uInt comb;			   /* combination field */
262   char *cstart;			   /* coefficient start */
263   char *c;			   /* output pointer in string */
264   const uInt *pu;		   /* work */
265   const uByte *u;		   /* .. */
266   char *s, *t;			   /* .. (source, target) */
267   Int  dpd;			   /* .. */
268   Int  pre, e;			   /* .. */
269   uInt sour;			   /* source 32-bit */
270 
271   /* load source from storage; this is endian */
272   pu=(const uInt *)d32->bytes;	   /* overlay */
273   sour=*pu;			   /* directly load the int */
274 
275   c=string;			   /* where result will go */
276   if (((Int)sour)<0) *c++='-';	   /* handle sign */
277 
278   comb=(sour>>26)&0x1f;		   /* combination field */
279   msd=COMBMSD[comb];		   /* decode the combination field */
280   exp=COMBEXP[comb];		   /* .. */
281 
282   if (exp==3) {
283     if (msd==0) {		   /* infinity */
284       strcpy(c,	  "Inf");
285       strcpy(c+3, "inity");
286       return string;		   /* easy */
287       }
288     if (sour&0x02000000) *c++='s'; /* sNaN */
289     strcpy(c, "NaN");		   /* complete word */
290     c+=3;			   /* step past */
291     if ((sour&0x000fffff)==0) return string; /* zero payload */
292     /* otherwise drop through to add integer; set correct exp */
293     exp=0; msd=0;		   /* setup for following code */
294     }
295    else exp=(exp<<6)+((sour>>20)&0x3f)-DECIMAL32_Bias; /* unbiased */
296 
297   /* convert 7 digits of significand to characters */
298   cstart=c;			   /* save start of coefficient */
299   if (msd) *c++='0'+(char)msd;	   /* non-zero most significant digit */
300 
301   /* Now decode the declets.  After extracting each one, it is */
302   /* decoded to binary and then to a 4-char sequence by table lookup; */
303   /* the 4-chars are a 1-char length (significant digits, except 000 */
304   /* has length 0).  This allows us to left-align the first declet */
305   /* with non-zero content, then remaining ones are full 3-char */
306   /* length.  We use fixed-length memcpys because variable-length */
307   /* causes a subroutine call in GCC.  (These are length 4 for speed */
308   /* and are safe because the array has an extra terminator byte.) */
309   #define dpd2char u=&BIN2CHAR[DPD2BIN[dpd]*4];			  \
310 		   if (c!=cstart) {memcpy(c, u+1, 4); c+=3;}	  \
311 		    else if (*u)  {memcpy(c, u+4-*u, 4); c+=*u;}
312 
313   dpd=(sour>>10)&0x3ff;		   /* declet 1 */
314   dpd2char;
315   dpd=(sour)&0x3ff;		   /* declet 2 */
316   dpd2char;
317 
318   if (c==cstart) *c++='0';	   /* all zeros -- make 0 */
319 
320   if (exp==0) {			   /* integer or NaN case -- easy */
321     *c='\0';			   /* terminate */
322     return string;
323     }
324 
325   /* non-0 exponent */
326   e=0;				   /* assume no E */
327   pre=c-cstart+exp;
328   /* [here, pre-exp is the digits count (==1 for zero)] */
329   if (exp>0 || pre<-5) {	   /* need exponential form */
330     e=pre-1;			   /* calculate E value */
331     pre=1;			   /* assume one digit before '.' */
332     } /* exponential form */
333 
334   /* modify the coefficient, adding 0s, '.', and E+nn as needed */
335   s=c-1;			   /* source (LSD) */
336   if (pre>0) {			   /* ddd.ddd (plain), perhaps with E */
337     char *dotat=cstart+pre;
338     if (dotat<c) {		   /* if embedded dot needed... */
339       t=c;				/* target */
340       for (; s>=dotat; s--, t--) *t=*s; /* open the gap; leave t at gap */
341       *t='.';				/* insert the dot */
342       c++;				/* length increased by one */
343       }
344 
345     /* finally add the E-part, if needed; it will never be 0, and has */
346     /* a maximum length of 3 digits (E-101 case) */
347     if (e!=0) {
348       *c++='E';			   /* starts with E */
349       *c++='+';			   /* assume positive */
350       if (e<0) {
351 	*(c-1)='-';		   /* oops, need '-' */
352 	e=-e;			   /* uInt, please */
353 	}
354       u=&BIN2CHAR[e*4];		   /* -> length byte */
355       memcpy(c, u+4-*u, 4);	   /* copy fixed 4 characters [is safe] */
356       c+=*u;			   /* bump pointer appropriately */
357       }
358     *c='\0';			   /* add terminator */
359     /*printf("res %s\n", string); */
360     return string;
361     } /* pre>0 */
362 
363   /* -5<=pre<=0: here for plain 0.ddd or 0.000ddd forms (can never have E) */
364   t=c+1-pre;
365   *(t+1)='\0';				/* can add terminator now */
366   for (; s>=cstart; s--, t--) *t=*s;	/* shift whole coefficient right */
367   c=cstart;
368   *c++='0';				/* always starts with 0. */
369   *c++='.';
370   for (; pre<0; pre++) *c++='0';	/* add any 0's after '.' */
371   /*printf("res %s\n", string); */
372   return string;
373   } /* decimal32ToString */
374 
375 /* ------------------------------------------------------------------ */
376 /* to-number -- conversion from numeric string			      */
377 /*								      */
378 /*   decimal32FromString(result, string, set);			      */
379 /*								      */
380 /*  result  is the decimal32 format number which gets the result of   */
381 /*	    the conversion					      */
382 /*  *string is the character string which should contain a valid      */
383 /*	    number (which may be a special value)		      */
384 /*  set	    is the context					      */
385 /*								      */
386 /* The context is supplied to this routine is used for error handling */
387 /* (setting of status and traps) and for the rounding mode, only.     */
388 /* If an error occurs, the result will be a valid decimal32 NaN.      */
389 /* ------------------------------------------------------------------ */
decimal32FromString(decimal32 * result,const char * string,decContext * set)390 decimal32 * decimal32FromString(decimal32 *result, const char *string,
391 				decContext *set) {
392   decContext dc;			     /* work */
393   decNumber dn;				     /* .. */
394 
395   decContextDefault(&dc, DEC_INIT_DECIMAL32); /* no traps, please */
396   dc.round=set->round;			      /* use supplied rounding */
397 
398   decNumberFromString(&dn, string, &dc);     /* will round if needed */
399   decimal32FromNumber(result, &dn, &dc);
400   if (dc.status!=0) {			     /* something happened */
401     decContextSetStatus(set, dc.status);     /* .. pass it on */
402     }
403   return result;
404   } /* decimal32FromString */
405 
406 /* ------------------------------------------------------------------ */
407 /* decimal32IsCanonical -- test whether encoding is canonical	      */
408 /*   d32 is the source decimal32				      */
409 /*   returns 1 if the encoding of d32 is canonical, 0 otherwise	      */
410 /* No error is possible.					      */
411 /* ------------------------------------------------------------------ */
decimal32IsCanonical(const decimal32 * d32)412 uint32_t decimal32IsCanonical(const decimal32 *d32) {
413   decNumber dn;				/* work */
414   decimal32 canon;			/* .. */
415   decContext dc;			/* .. */
416   decContextDefault(&dc, DEC_INIT_DECIMAL32);
417   decimal32ToNumber(d32, &dn);
418   decimal32FromNumber(&canon, &dn, &dc);/* canon will now be canonical */
419   return memcmp(d32, &canon, DECIMAL32_Bytes)==0;
420   } /* decimal32IsCanonical */
421 
422 /* ------------------------------------------------------------------ */
423 /* decimal32Canonical -- copy an encoding, ensuring it is canonical   */
424 /*   d32 is the source decimal32				      */
425 /*   result is the target (may be the same decimal32)		      */
426 /*   returns result						      */
427 /* No error is possible.					      */
428 /* ------------------------------------------------------------------ */
decimal32Canonical(decimal32 * result,const decimal32 * d32)429 decimal32 * decimal32Canonical(decimal32 *result, const decimal32 *d32) {
430   decNumber dn;				/* work */
431   decContext dc;			/* .. */
432   decContextDefault(&dc, DEC_INIT_DECIMAL32);
433   decimal32ToNumber(d32, &dn);
434   decimal32FromNumber(result, &dn, &dc);/* result will now be canonical */
435   return result;
436   } /* decimal32Canonical */
437 
438 #if DECTRACE || DECCHECK
439 /* Macros for accessing decimal32 fields.  These assume the argument
440    is a reference (pointer) to the decimal32 structure, and the
441    decimal32 is in network byte order (big-endian) */
442 /* Get sign */
443 #define decimal32Sign(d)       ((unsigned)(d)->bytes[0]>>7)
444 
445 /* Get combination field */
446 #define decimal32Comb(d)       (((d)->bytes[0] & 0x7c)>>2)
447 
448 /* Get exponent continuation [does not remove bias] */
449 #define decimal32ExpCon(d)     ((((d)->bytes[0] & 0x03)<<4)	      \
450 			     | ((unsigned)(d)->bytes[1]>>4))
451 
452 /* Set sign [this assumes sign previously 0] */
453 #define decimal32SetSign(d, b) {				      \
454   (d)->bytes[0]|=((unsigned)(b)<<7);}
455 
456 /* Set exponent continuation [does not apply bias] */
457 /* This assumes range has been checked and exponent previously 0; */
458 /* type of exponent must be unsigned */
459 #define decimal32SetExpCon(d, e) {				      \
460   (d)->bytes[0]|=(uint8_t)((e)>>4);				      \
461   (d)->bytes[1]|=(uint8_t)(((e)&0x0F)<<4);}
462 
463 /* ------------------------------------------------------------------ */
464 /* decimal32Show -- display a decimal32 in hexadecimal [debug aid]    */
465 /*   d32 -- the number to show					      */
466 /* ------------------------------------------------------------------ */
467 /* Also shows sign/cob/expconfields extracted - valid bigendian only */
decimal32Show(const decimal32 * d32)468 void decimal32Show(const decimal32 *d32) {
469   char buf[DECIMAL32_Bytes*2+1];
470   Int i, j=0;
471 
472   if (DECLITEND) {
473     for (i=0; i<DECIMAL32_Bytes; i++, j+=2) {
474       sprintf(&buf[j], "%02x", d32->bytes[3-i]);
475       }
476     printf(" D32> %s [S:%d Cb:%02x Ec:%02x] LittleEndian\n", buf,
477 	   d32->bytes[3]>>7, (d32->bytes[3]>>2)&0x1f,
478 	   ((d32->bytes[3]&0x3)<<4)| (d32->bytes[2]>>4));
479     }
480    else {
481     for (i=0; i<DECIMAL32_Bytes; i++, j+=2) {
482       sprintf(&buf[j], "%02x", d32->bytes[i]);
483       }
484     printf(" D32> %s [S:%d Cb:%02x Ec:%02x] BigEndian\n", buf,
485 	   decimal32Sign(d32), decimal32Comb(d32), decimal32ExpCon(d32));
486     }
487   } /* decimal32Show */
488 #endif
489