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      1 /* itbl-ops.c
      2    Copyright (C) 1997-2014 Free Software Foundation, Inc.
      3 
      4    This file is part of GAS, the GNU Assembler.
      5 
      6    GAS is free software; you can redistribute it and/or modify
      7    it under the terms of the GNU General Public License as published by
      8    the Free Software Foundation; either version 3, or (at your option)
      9    any later version.
     10 
     11    GAS is distributed in the hope that it will be useful,
     12    but WITHOUT ANY WARRANTY; without even the implied warranty of
     13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     14    GNU General Public License for more details.
     15 
     16    You should have received a copy of the GNU General Public License
     17    along with GAS; see the file COPYING.  If not, write to the Free
     18    Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
     19    02110-1301, USA.  */
     20 
     21 /*======================================================================*/
     22 /*
     23  * Herein lies the support for dynamic specification of processor
     24  * instructions and registers.  Mnemonics, values, and formats for each
     25  * instruction and register are specified in an ascii file consisting of
     26  * table entries.  The grammar for the table is defined in the document
     27  * "Processor instruction table specification".
     28  *
     29  * Instructions use the gnu assembler syntax, with the addition of
     30  * allowing mnemonics for register.
     31  * Eg. "func $2,reg3,0x100,symbol ; comment"
     32  * 	func - opcode name
     33  * 	$n - register n
     34  * 	reg3 - mnemonic for processor's register defined in table
     35  * 	0xddd..d - immediate value
     36  * 	symbol - address of label or external symbol
     37  *
     38  * First, itbl_parse reads in the table of register and instruction
     39  * names and formats, and builds a list of entries for each
     40  * processor/type combination.  lex and yacc are used to parse
     41  * the entries in the table and call functions defined here to
     42  * add each entry to our list.
     43  *
     44  * Then, when assembling or disassembling, these functions are called to
     45  * 1) get information on a processor's registers and
     46  * 2) assemble/disassemble an instruction.
     47  * To assemble(disassemble) an instruction, the function
     48  * itbl_assemble(itbl_disassemble) is called to search the list of
     49  * instruction entries, and if a match is found, uses the format
     50  * described in the instruction entry structure to complete the action.
     51  *
     52  * Eg. Suppose we have a Mips coprocessor "cop3" with data register "d2"
     53  * and we want to define function "pig" which takes two operands.
     54  *
     55  * Given the table entries:
     56  * 	"p3 insn pig 0x1:24-21 dreg:20-16 immed:15-0"
     57  * 	"p3 dreg d2 0x2"
     58  * and that the instruction encoding for coprocessor pz has encoding:
     59  * 	#define MIPS_ENCODE_COP_NUM(z) ((0x21|(z<<1))<<25)
     60  * 	#define ITBL_ENCODE_PNUM(pnum) MIPS_ENCODE_COP_NUM(pnum)
     61  *
     62  * a structure to describe the instruction might look something like:
     63  *      struct itbl_entry = {
     64  *      e_processor processor = e_p3
     65  *      e_type type = e_insn
     66  *      char *name = "pig"
     67  *      uint value = 0x1
     68  *      uint flags = 0
     69  *      struct itbl_range range = 24-21
     70  *      struct itbl_field *field = {
     71  *              e_type type = e_dreg
     72  *              struct itbl_range range = 20-16
     73  *              struct itbl_field *next = {
     74  *                      e_type type = e_immed
     75  *                      struct itbl_range range = 15-0
     76  *                      struct itbl_field *next = 0
     77  *                      };
     78  *              };
     79  *      struct itbl_entry *next = 0
     80  *      };
     81  *
     82  * And the assembler instructions:
     83  * 	"pig d2,0x100"
     84  * 	"pig $2,0x100"
     85  *
     86  * would both assemble to the hex value:
     87  * 	"0x4e220100"
     88  *
     89  */
     90 
     91 #include "as.h"
     92 #include "itbl-ops.h"
     93 #include <itbl-parse.h>
     94 
     95 /* #define DEBUG */
     96 
     97 #ifdef DEBUG
     98 #include <assert.h>
     99 #define ASSERT(x) gas_assert (x)
    100 #define DBG(x) printf x
    101 #else
    102 #define ASSERT(x)
    103 #define DBG(x)
    104 #endif
    105 
    106 #ifndef min
    107 #define min(a,b) (a<b?a:b)
    108 #endif
    109 
    110 int itbl_have_entries = 0;
    111 
    112 /*======================================================================*/
    113 /* structures for keeping itbl format entries */
    114 
    115 struct itbl_range {
    116   int sbit;			/* mask starting bit position */
    117   int ebit;			/* mask ending bit position */
    118 };
    119 
    120 struct itbl_field {
    121   e_type type;			/* dreg/creg/greg/immed/symb */
    122   struct itbl_range range;	/* field's bitfield range within instruction */
    123   unsigned long flags;		/* field flags */
    124   struct itbl_field *next;	/* next field in list */
    125 };
    126 
    127 /* These structures define the instructions and registers for a processor.
    128  * If the type is an instruction, the structure defines the format of an
    129  * instruction where the fields are the list of operands.
    130  * The flags field below uses the same values as those defined in the
    131  * gnu assembler and are machine specific.  */
    132 struct itbl_entry {
    133   e_processor processor;	/* processor number */
    134   e_type type;			/* dreg/creg/greg/insn */
    135   char *name;			/* mnemionic name for insn/register */
    136   unsigned long value;		/* opcode/instruction mask/register number */
    137   unsigned long flags;		/* effects of the instruction */
    138   struct itbl_range range;	/* bit range within instruction for value */
    139   struct itbl_field *fields;	/* list of operand definitions (if any) */
    140   struct itbl_entry *next;	/* next entry */
    141 };
    142 
    143 /* local data and structures */
    144 
    145 static int itbl_num_opcodes = 0;
    146 /* Array of entries for each processor and entry type */
    147 static struct itbl_entry *entries[e_nprocs][e_ntypes];
    148 
    149 /* local prototypes */
    150 static unsigned long build_opcode (struct itbl_entry *e);
    151 static e_type get_type (int yytype);
    152 static e_processor get_processor (int yyproc);
    153 static struct itbl_entry **get_entries (e_processor processor,
    154 					e_type type);
    155 static struct itbl_entry *find_entry_byname (e_processor processor,
    156 					e_type type, char *name);
    157 static struct itbl_entry *find_entry_byval (e_processor processor,
    158 			e_type type, unsigned long val, struct itbl_range *r);
    159 static struct itbl_entry *alloc_entry (e_processor processor,
    160 		e_type type, char *name, unsigned long value);
    161 static unsigned long apply_range (unsigned long value, struct itbl_range r);
    162 static unsigned long extract_range (unsigned long value, struct itbl_range r);
    163 static struct itbl_field *alloc_field (e_type type, int sbit,
    164 					int ebit, unsigned long flags);
    165 
    166 /*======================================================================*/
    167 /* Interfaces to the parser */
    168 
    169 /* Open the table and use lex and yacc to parse the entries.
    170  * Return 1 for failure; 0 for success.  */
    171 
    172 int
    173 itbl_parse (char *insntbl)
    174 {
    175   extern FILE *yyin;
    176   extern int yyparse (void);
    177 
    178   yyin = fopen (insntbl, FOPEN_RT);
    179   if (yyin == 0)
    180     {
    181       printf ("Can't open processor instruction specification file \"%s\"\n",
    182 	      insntbl);
    183       return 1;
    184     }
    185 
    186   while (yyparse ())
    187     ;
    188 
    189   fclose (yyin);
    190   itbl_have_entries = 1;
    191   return 0;
    192 }
    193 
    194 /* Add a register entry */
    195 
    196 struct itbl_entry *
    197 itbl_add_reg (int yyprocessor, int yytype, char *regname,
    198 	      int regnum)
    199 {
    200   return alloc_entry (get_processor (yyprocessor), get_type (yytype), regname,
    201 		      (unsigned long) regnum);
    202 }
    203 
    204 /* Add an instruction entry */
    205 
    206 struct itbl_entry *
    207 itbl_add_insn (int yyprocessor, char *name, unsigned long value,
    208 	       int sbit, int ebit, unsigned long flags)
    209 {
    210   struct itbl_entry *e;
    211   e = alloc_entry (get_processor (yyprocessor), e_insn, name, value);
    212   if (e)
    213     {
    214       e->range.sbit = sbit;
    215       e->range.ebit = ebit;
    216       e->flags = flags;
    217       itbl_num_opcodes++;
    218     }
    219   return e;
    220 }
    221 
    222 /* Add an operand to an instruction entry */
    223 
    224 struct itbl_field *
    225 itbl_add_operand (struct itbl_entry *e, int yytype, int sbit,
    226 		  int ebit, unsigned long flags)
    227 {
    228   struct itbl_field *f, **last_f;
    229   if (!e)
    230     return 0;
    231   /* Add to end of fields' list.  */
    232   f = alloc_field (get_type (yytype), sbit, ebit, flags);
    233   if (f)
    234     {
    235       last_f = &e->fields;
    236       while (*last_f)
    237 	last_f = &(*last_f)->next;
    238       *last_f = f;
    239       f->next = 0;
    240     }
    241   return f;
    242 }
    243 
    244 /*======================================================================*/
    245 /* Interfaces for assembler and disassembler */
    246 
    247 #ifndef STAND_ALONE
    248 static void append_insns_as_macros (void);
    249 
    250 /* Initialize for gas.  */
    251 
    252 void
    253 itbl_init (void)
    254 {
    255   struct itbl_entry *e, **es;
    256   e_processor procn;
    257   e_type type;
    258 
    259   if (!itbl_have_entries)
    260     return;
    261 
    262   /* Since register names don't have a prefix, put them in the symbol table so
    263      they can't be used as symbols.  This simplifies argument parsing as
    264      we can let gas parse registers for us.  */
    265   /* Use symbol_create instead of symbol_new so we don't try to
    266      output registers into the object file's symbol table.  */
    267 
    268   for (type = e_regtype0; type < e_nregtypes; type++)
    269     for (procn = e_p0; procn < e_nprocs; procn++)
    270       {
    271 	es = get_entries (procn, type);
    272 	for (e = *es; e; e = e->next)
    273 	  {
    274 	    symbol_table_insert (symbol_create (e->name, reg_section,
    275 						e->value, &zero_address_frag));
    276 	  }
    277       }
    278   append_insns_as_macros ();
    279 }
    280 
    281 /* Append insns to opcodes table and increase number of opcodes
    282  * Structure of opcodes table:
    283  * struct itbl_opcode
    284  * {
    285  *   const char *name;
    286  *   const char *args; 		- string describing the arguments.
    287  *   unsigned long match; 	- opcode, or ISA level if pinfo=INSN_MACRO
    288  *   unsigned long mask; 	- opcode mask, or macro id if pinfo=INSN_MACRO
    289  *   unsigned long pinfo; 	- insn flags, or INSN_MACRO
    290  * };
    291  * examples:
    292  *	{"li",      "t,i",  0x34000000, 0xffe00000, WR_t    },
    293  *	{"li",      "t,I",  0,    (int) M_LI,   INSN_MACRO  },
    294  */
    295 
    296 static char *form_args (struct itbl_entry *e);
    297 static void
    298 append_insns_as_macros (void)
    299 {
    300   struct ITBL_OPCODE_STRUCT *new_opcodes, *o;
    301   struct itbl_entry *e, **es;
    302   int n, size, new_size, new_num_opcodes;
    303 #ifdef USE_MACROS
    304   int id;
    305 #endif
    306 
    307   if (!itbl_have_entries)
    308     return;
    309 
    310   if (!itbl_num_opcodes)	/* no new instructions to add! */
    311     {
    312       return;
    313     }
    314   DBG (("previous num_opcodes=%d\n", ITBL_NUM_OPCODES));
    315 
    316   new_num_opcodes = ITBL_NUM_OPCODES + itbl_num_opcodes;
    317   ASSERT (new_num_opcodes >= itbl_num_opcodes);
    318 
    319   size = sizeof (struct ITBL_OPCODE_STRUCT) * ITBL_NUM_OPCODES;
    320   ASSERT (size >= 0);
    321   DBG (("I get=%d\n", size / sizeof (ITBL_OPCODES[0])));
    322 
    323   new_size = sizeof (struct ITBL_OPCODE_STRUCT) * new_num_opcodes;
    324   ASSERT (new_size > size);
    325 
    326   /* FIXME since ITBL_OPCODES culd be a static table,
    327 		we can't realloc or delete the old memory.  */
    328   new_opcodes = (struct ITBL_OPCODE_STRUCT *) malloc (new_size);
    329   if (!new_opcodes)
    330     {
    331       printf (_("Unable to allocate memory for new instructions\n"));
    332       return;
    333     }
    334   if (size)			/* copy preexisting opcodes table */
    335     memcpy (new_opcodes, ITBL_OPCODES, size);
    336 
    337   /* FIXME! some NUMOPCODES are calculated expressions.
    338 		These need to be changed before itbls can be supported.  */
    339 
    340 #ifdef USE_MACROS
    341   id = ITBL_NUM_MACROS;		/* begin the next macro id after the last */
    342 #endif
    343   o = &new_opcodes[ITBL_NUM_OPCODES];	/* append macro to opcodes list */
    344   for (n = e_p0; n < e_nprocs; n++)
    345     {
    346       es = get_entries (n, e_insn);
    347       for (e = *es; e; e = e->next)
    348 	{
    349 	  /* name,    args,   mask,       match,  pinfo
    350 		 * {"li",      "t,i",  0x34000000, 0xffe00000, WR_t    },
    351 		 * {"li",      "t,I",  0,    (int) M_LI,   INSN_MACRO  },
    352 		 * Construct args from itbl_fields.
    353 		*/
    354 	  o->name = e->name;
    355 	  o->args = strdup (form_args (e));
    356 	  o->mask = apply_range (e->value, e->range);
    357 	  /* FIXME how to catch during assembly? */
    358 	  /* mask to identify this insn */
    359 	  o->match = apply_range (e->value, e->range);
    360 	  o->pinfo = 0;
    361 
    362 #ifdef USE_MACROS
    363 	  o->mask = id++;	/* FIXME how to catch during assembly? */
    364 	  o->match = 0;		/* for macros, the insn_isa number */
    365 	  o->pinfo = INSN_MACRO;
    366 #endif
    367 
    368 	  /* Don't add instructions which caused an error */
    369 	  if (o->args)
    370 	    o++;
    371 	  else
    372 	    new_num_opcodes--;
    373 	}
    374     }
    375   ITBL_OPCODES = new_opcodes;
    376   ITBL_NUM_OPCODES = new_num_opcodes;
    377 
    378   /* FIXME
    379 		At this point, we can free the entries, as they should have
    380 		been added to the assembler's tables.
    381 		Don't free name though, since name is being used by the new
    382 		opcodes table.
    383 
    384 		Eventually, we should also free the new opcodes table itself
    385 		on exit.
    386 	*/
    387 }
    388 
    389 static char *
    390 form_args (struct itbl_entry *e)
    391 {
    392   static char s[31];
    393   char c = 0, *p = s;
    394   struct itbl_field *f;
    395 
    396   ASSERT (e);
    397   for (f = e->fields; f; f = f->next)
    398     {
    399       switch (f->type)
    400 	{
    401 	case e_dreg:
    402 	  c = 'd';
    403 	  break;
    404 	case e_creg:
    405 	  c = 't';
    406 	  break;
    407 	case e_greg:
    408 	  c = 's';
    409 	  break;
    410 	case e_immed:
    411 	  c = 'i';
    412 	  break;
    413 	case e_addr:
    414 	  c = 'a';
    415 	  break;
    416 	default:
    417 	  c = 0;		/* ignore; unknown field type */
    418 	}
    419       if (c)
    420 	{
    421 	  if (p != s)
    422 	    *p++ = ',';
    423 	  *p++ = c;
    424 	}
    425     }
    426   *p = 0;
    427   return s;
    428 }
    429 #endif /* !STAND_ALONE */
    430 
    431 /* Get processor's register name from val */
    432 
    433 int
    434 itbl_get_reg_val (char *name, unsigned long *pval)
    435 {
    436   e_type t;
    437   e_processor p;
    438 
    439   for (p = e_p0; p < e_nprocs; p++)
    440     {
    441       for (t = e_regtype0; t < e_nregtypes; t++)
    442 	{
    443 	  if (itbl_get_val (p, t, name, pval))
    444 	    return 1;
    445 	}
    446     }
    447   return 0;
    448 }
    449 
    450 char *
    451 itbl_get_name (e_processor processor, e_type type, unsigned long val)
    452 {
    453   struct itbl_entry *r;
    454   /* type depends on instruction passed */
    455   r = find_entry_byval (processor, type, val, 0);
    456   if (r)
    457     return r->name;
    458   else
    459     return 0;			/* error; invalid operand */
    460 }
    461 
    462 /* Get processor's register value from name */
    463 
    464 int
    465 itbl_get_val (e_processor processor, e_type type, char *name,
    466 	      unsigned long *pval)
    467 {
    468   struct itbl_entry *r;
    469   /* type depends on instruction passed */
    470   r = find_entry_byname (processor, type, name);
    471   if (r == NULL)
    472     return 0;
    473   *pval = r->value;
    474   return 1;
    475 }
    476 
    477 /* Assemble instruction "name" with operands "s".
    478  * name - name of instruction
    479  * s - operands
    480  * returns - long word for assembled instruction */
    481 
    482 unsigned long
    483 itbl_assemble (char *name, char *s)
    484 {
    485   unsigned long opcode;
    486   struct itbl_entry *e = NULL;
    487   struct itbl_field *f;
    488   char *n;
    489   int processor;
    490 
    491   if (!name || !*name)
    492     return 0;			/* error!  must have an opcode name/expr */
    493 
    494   /* find entry in list of instructions for all processors */
    495   for (processor = 0; processor < e_nprocs; processor++)
    496     {
    497       e = find_entry_byname (processor, e_insn, name);
    498       if (e)
    499 	break;
    500     }
    501   if (!e)
    502     return 0;			/* opcode not in table; invalid instruction */
    503   opcode = build_opcode (e);
    504 
    505   /* parse opcode's args (if any) */
    506   for (f = e->fields; f; f = f->next)	/* for each arg, ...  */
    507     {
    508       struct itbl_entry *r;
    509       unsigned long value;
    510       if (!s || !*s)
    511 	return 0;		/* error - not enough operands */
    512       n = itbl_get_field (&s);
    513       /* n should be in form $n or 0xhhh (are symbol names valid?? */
    514       switch (f->type)
    515 	{
    516 	case e_dreg:
    517 	case e_creg:
    518 	case e_greg:
    519 	  /* Accept either a string name
    520 			 * or '$' followed by the register number */
    521 	  if (*n == '$')
    522 	    {
    523 	      n++;
    524 	      value = strtol (n, 0, 10);
    525 	      /* FIXME! could have "0l"... then what?? */
    526 	      if (value == 0 && *n != '0')
    527 		return 0;	/* error; invalid operand */
    528 	    }
    529 	  else
    530 	    {
    531 	      r = find_entry_byname (e->processor, f->type, n);
    532 	      if (r)
    533 		value = r->value;
    534 	      else
    535 		return 0;	/* error; invalid operand */
    536 	    }
    537 	  break;
    538 	case e_addr:
    539 	  /* use assembler's symbol table to find symbol */
    540 	  /* FIXME!! Do we need this?
    541 				if so, what about relocs??
    542 				my_getExpression (&imm_expr, s);
    543 				return 0;	/-* error; invalid operand *-/
    544 				break;
    545 			*/
    546 	  /* If not a symbol, fall thru to IMMED */
    547 	case e_immed:
    548 	  if (*n == '0' && *(n + 1) == 'x')	/* hex begins 0x...  */
    549 	    {
    550 	      n += 2;
    551 	      value = strtol (n, 0, 16);
    552 	      /* FIXME! could have "0xl"... then what?? */
    553 	    }
    554 	  else
    555 	    {
    556 	      value = strtol (n, 0, 10);
    557 	      /* FIXME! could have "0l"... then what?? */
    558 	      if (value == 0 && *n != '0')
    559 		return 0;	/* error; invalid operand */
    560 	    }
    561 	  break;
    562 	default:
    563 	  return 0;		/* error; invalid field spec */
    564 	}
    565       opcode |= apply_range (value, f->range);
    566     }
    567   if (s && *s)
    568     return 0;			/* error - too many operands */
    569   return opcode;		/* done! */
    570 }
    571 
    572 /* Disassemble instruction "insn".
    573  * insn - instruction
    574  * s - buffer to hold disassembled instruction
    575  * returns - 1 if succeeded; 0 if failed
    576  */
    577 
    578 int
    579 itbl_disassemble (char *s, unsigned long insn)
    580 {
    581   e_processor processor;
    582   struct itbl_entry *e;
    583   struct itbl_field *f;
    584 
    585   if (!ITBL_IS_INSN (insn))
    586     return 0;			/* error */
    587   processor = get_processor (ITBL_DECODE_PNUM (insn));
    588 
    589   /* find entry in list */
    590   e = find_entry_byval (processor, e_insn, insn, 0);
    591   if (!e)
    592     return 0;			/* opcode not in table; invalid instruction */
    593   strcpy (s, e->name);
    594 
    595   /* Parse insn's args (if any).  */
    596   for (f = e->fields; f; f = f->next)	/* for each arg, ...  */
    597     {
    598       struct itbl_entry *r;
    599       unsigned long value;
    600       char s_value[20];
    601 
    602       if (f == e->fields)	/* First operand is preceded by tab.  */
    603 	strcat (s, "\t");
    604       else			/* ','s separate following operands.  */
    605 	strcat (s, ",");
    606       value = extract_range (insn, f->range);
    607       /* n should be in form $n or 0xhhh (are symbol names valid?? */
    608       switch (f->type)
    609 	{
    610 	case e_dreg:
    611 	case e_creg:
    612 	case e_greg:
    613 	  /* Accept either a string name
    614 	     or '$' followed by the register number.  */
    615 	  r = find_entry_byval (e->processor, f->type, value, &f->range);
    616 	  if (r)
    617 	    strcat (s, r->name);
    618 	  else
    619 	    {
    620 	      sprintf (s_value, "$%lu", value);
    621 	      strcat (s, s_value);
    622 	    }
    623 	  break;
    624 	case e_addr:
    625 	  /* Use assembler's symbol table to find symbol.  */
    626 	  /* FIXME!! Do we need this?  If so, what about relocs??  */
    627 	  /* If not a symbol, fall through to IMMED.  */
    628 	case e_immed:
    629 	  sprintf (s_value, "0x%lx", value);
    630 	  strcat (s, s_value);
    631 	  break;
    632 	default:
    633 	  return 0;		/* error; invalid field spec */
    634 	}
    635     }
    636   return 1;			/* Done!  */
    637 }
    638 
    639 /*======================================================================*/
    640 /*
    641  * Local functions for manipulating private structures containing
    642  * the names and format for the new instructions and registers
    643  * for each processor.
    644  */
    645 
    646 /* Calculate instruction's opcode and function values from entry */
    647 
    648 static unsigned long
    649 build_opcode (struct itbl_entry *e)
    650 {
    651   unsigned long opcode;
    652 
    653   opcode = apply_range (e->value, e->range);
    654   opcode |= ITBL_ENCODE_PNUM (e->processor);
    655   return opcode;
    656 }
    657 
    658 /* Calculate absolute value given the relative value and bit position range
    659  * within the instruction.
    660  * The range is inclusive where 0 is least significant bit.
    661  * A range of { 24, 20 } will have a mask of
    662  * bit   3           2            1
    663  * pos: 1098 7654 3210 9876 5432 1098 7654 3210
    664  * bin: 0000 0001 1111 0000 0000 0000 0000 0000
    665  * hex:    0    1    f    0    0    0    0    0
    666  * mask: 0x01f00000.
    667  */
    668 
    669 static unsigned long
    670 apply_range (unsigned long rval, struct itbl_range r)
    671 {
    672   unsigned long mask;
    673   unsigned long aval;
    674   int len = MAX_BITPOS - r.sbit;
    675 
    676   ASSERT (r.sbit >= r.ebit);
    677   ASSERT (MAX_BITPOS >= r.sbit);
    678   ASSERT (r.ebit >= 0);
    679 
    680   /* create mask by truncating 1s by shifting */
    681   mask = 0xffffffff << len;
    682   mask = mask >> len;
    683   mask = mask >> r.ebit;
    684   mask = mask << r.ebit;
    685 
    686   aval = (rval << r.ebit) & mask;
    687   return aval;
    688 }
    689 
    690 /* Calculate relative value given the absolute value and bit position range
    691  * within the instruction.  */
    692 
    693 static unsigned long
    694 extract_range (unsigned long aval, struct itbl_range r)
    695 {
    696   unsigned long mask;
    697   unsigned long rval;
    698   int len = MAX_BITPOS - r.sbit;
    699 
    700   /* create mask by truncating 1s by shifting */
    701   mask = 0xffffffff << len;
    702   mask = mask >> len;
    703   mask = mask >> r.ebit;
    704   mask = mask << r.ebit;
    705 
    706   rval = (aval & mask) >> r.ebit;
    707   return rval;
    708 }
    709 
    710 /* Extract processor's assembly instruction field name from s;
    711  * forms are "n args" "n,args" or "n" */
    712 /* Return next argument from string pointer "s" and advance s.
    713  * delimiters are " ,()" */
    714 
    715 char *
    716 itbl_get_field (char **S)
    717 {
    718   static char n[128];
    719   char *s;
    720   int len;
    721 
    722   s = *S;
    723   if (!s || !*s)
    724     return 0;
    725   /* FIXME: This is a weird set of delimiters.  */
    726   len = strcspn (s, " \t,()");
    727   ASSERT (128 > len + 1);
    728   strncpy (n, s, len);
    729   n[len] = 0;
    730   if (s[len] == '\0')
    731     s = 0;			/* no more args */
    732   else
    733     s += len + 1;		/* advance to next arg */
    734 
    735   *S = s;
    736   return n;
    737 }
    738 
    739 /* Search entries for a given processor and type
    740  * to find one matching the name "n".
    741  * Return a pointer to the entry */
    742 
    743 static struct itbl_entry *
    744 find_entry_byname (e_processor processor,
    745 		   e_type type, char *n)
    746 {
    747   struct itbl_entry *e, **es;
    748 
    749   es = get_entries (processor, type);
    750   for (e = *es; e; e = e->next)	/* for each entry, ...  */
    751     {
    752       if (!strcmp (e->name, n))
    753 	return e;
    754     }
    755   return 0;
    756 }
    757 
    758 /* Search entries for a given processor and type
    759  * to find one matching the value "val" for the range "r".
    760  * Return a pointer to the entry.
    761  * This function is used for disassembling fields of an instruction.
    762  */
    763 
    764 static struct itbl_entry *
    765 find_entry_byval (e_processor processor, e_type type,
    766 		  unsigned long val, struct itbl_range *r)
    767 {
    768   struct itbl_entry *e, **es;
    769   unsigned long eval;
    770 
    771   es = get_entries (processor, type);
    772   for (e = *es; e; e = e->next)	/* for each entry, ...  */
    773     {
    774       if (processor != e->processor)
    775 	continue;
    776       /* For insns, we might not know the range of the opcode,
    777 	 * so a range of 0 will allow this routine to match against
    778 	 * the range of the entry to be compared with.
    779 	 * This could cause ambiguities.
    780 	 * For operands, we get an extracted value and a range.
    781 	 */
    782       /* if range is 0, mask val against the range of the compared entry.  */
    783       if (r == 0)		/* if no range passed, must be whole 32-bits
    784 			 * so create 32-bit value from entry's range */
    785 	{
    786 	  eval = apply_range (e->value, e->range);
    787 	  val &= apply_range (0xffffffff, e->range);
    788 	}
    789       else if ((r->sbit == e->range.sbit && r->ebit == e->range.ebit)
    790 	       || (e->range.sbit == 0 && e->range.ebit == 0))
    791 	{
    792 	  eval = apply_range (e->value, *r);
    793 	  val = apply_range (val, *r);
    794 	}
    795       else
    796 	continue;
    797       if (val == eval)
    798 	return e;
    799     }
    800   return 0;
    801 }
    802 
    803 /* Return a pointer to the list of entries for a given processor and type.  */
    804 
    805 static struct itbl_entry **
    806 get_entries (e_processor processor, e_type type)
    807 {
    808   return &entries[processor][type];
    809 }
    810 
    811 /* Return an integral value for the processor passed from yyparse.  */
    812 
    813 static e_processor
    814 get_processor (int yyproc)
    815 {
    816   /* translate from yacc's processor to enum */
    817   if (yyproc >= e_p0 && yyproc < e_nprocs)
    818     return (e_processor) yyproc;
    819   return e_invproc;		/* error; invalid processor */
    820 }
    821 
    822 /* Return an integral value for the entry type passed from yyparse.  */
    823 
    824 static e_type
    825 get_type (int yytype)
    826 {
    827   switch (yytype)
    828     {
    829       /* translate from yacc's type to enum */
    830     case INSN:
    831       return e_insn;
    832     case DREG:
    833       return e_dreg;
    834     case CREG:
    835       return e_creg;
    836     case GREG:
    837       return e_greg;
    838     case ADDR:
    839       return e_addr;
    840     case IMMED:
    841       return e_immed;
    842     default:
    843       return e_invtype;		/* error; invalid type */
    844     }
    845 }
    846 
    847 /* Allocate and initialize an entry */
    848 
    849 static struct itbl_entry *
    850 alloc_entry (e_processor processor, e_type type,
    851 	     char *name, unsigned long value)
    852 {
    853   struct itbl_entry *e, **es;
    854   if (!name)
    855     return 0;
    856   e = (struct itbl_entry *) malloc (sizeof (struct itbl_entry));
    857   if (e)
    858     {
    859       memset (e, 0, sizeof (struct itbl_entry));
    860       e->name = (char *) malloc (sizeof (strlen (name)) + 1);
    861       if (e->name)
    862 	strcpy (e->name, name);
    863       e->processor = processor;
    864       e->type = type;
    865       e->value = value;
    866       es = get_entries (e->processor, e->type);
    867       e->next = *es;
    868       *es = e;
    869     }
    870   return e;
    871 }
    872 
    873 /* Allocate and initialize an entry's field */
    874 
    875 static struct itbl_field *
    876 alloc_field (e_type type, int sbit, int ebit,
    877 	     unsigned long flags)
    878 {
    879   struct itbl_field *f;
    880   f = (struct itbl_field *) malloc (sizeof (struct itbl_field));
    881   if (f)
    882     {
    883       memset (f, 0, sizeof (struct itbl_field));
    884       f->type = type;
    885       f->range.sbit = sbit;
    886       f->range.ebit = ebit;
    887       f->flags = flags;
    888     }
    889   return f;
    890 }
    891