* Extensive changes to permit symbols to contain any expression

[deliverable/binutils-gdb.git] / gas / config / tc-tahoe.c

/* tc-tahoe.c
   Not part of GAS yet. */

#include "as.h"
#include "obstack.h"

/* this bit glommed from tahoe-inst.h */

typedef unsigned char byte;
typedef byte tahoe_opcodeT;

/*
 * This is part of tahoe-ins-parse.c & friends.
 * We want to parse a tahoe instruction text into a tree defined here.
 */

#define TIT_MAX_OPERANDS (4)    /* maximum number of operands in one
                                   single tahoe instruction */

struct top                      /* tahoe instruction operand */
{
  int top_ndx;                  /* -1, or index register. eg 7=[R7] */
  int top_reg;                  /* -1, or register number. eg 7 = R7 or (R7) */
  byte top_mode;                /* Addressing mode byte. This byte, defines
                                   which of the 11 modes opcode is. */

  char top_access;              /* Access type wanted for this opperand
                                   'b'branch ' 'no-instruction 'amrvw' */
  char top_width;               /* Operand width expected, one of "bwlq?-:!" */

  char *top_error;              /* Say if operand is inappropriate         */

  segT seg_of_operand;          /* segment as returned by expression()*/

  expressionS exp_of_operand;   /* The expression as parsed by expression()*/

  byte top_dispsize;            /* Number of bytes in the displacement if we
                                   can figure it out */
};

/* The addressing modes for an operand. These numbers are the acutal values
   for certain modes, so be carefull if you screw with them. */
#define TAHOE_DIRECT_REG (0x50)
#define TAHOE_REG_DEFERRED (0x60)

#define TAHOE_REG_DISP (0xE0)
#define TAHOE_REG_DISP_DEFERRED (0xF0)

#define TAHOE_IMMEDIATE (0x8F)
#define TAHOE_IMMEDIATE_BYTE (0x88)
#define TAHOE_IMMEDIATE_WORD (0x89)
#define TAHOE_IMMEDIATE_LONGWORD (0x8F)
#define TAHOE_ABSOLUTE_ADDR (0x9F)

#define TAHOE_DISPLACED_RELATIVE (0xEF)
#define TAHOE_DISP_REL_DEFERRED (0xFF)

#define TAHOE_AUTO_DEC (0x7E)
#define TAHOE_AUTO_INC (0x8E)
#define TAHOE_AUTO_INC_DEFERRED (0x9E)
/* INDEXED_REG is decided by the existance or lack of a [reg] */

/* These are encoded into top_width when top_access=='b'
   and it's a psuedo op.*/
#define TAHOE_WIDTH_ALWAYS_JUMP      '-'
#define TAHOE_WIDTH_CONDITIONAL_JUMP '?'
#define TAHOE_WIDTH_BIG_REV_JUMP     '!'
#define TAHOE_WIDTH_BIG_NON_REV_JUMP ':'

/* The hex code for certain tahoe commands and modes.
   This is just for readability. */
#define TAHOE_JMP (0x71)
#define TAHOE_PC_REL_LONG (0xEF)
#define TAHOE_BRB (0x11)
#define TAHOE_BRW (0x13)
/* These, when 'ored' with, or added to, a register number,
   set up the number for the displacement mode. */
#define TAHOE_PC_OR_BYTE (0xA0)
#define TAHOE_PC_OR_WORD (0xC0)
#define TAHOE_PC_OR_LONG (0xE0)

struct tit                      /* get it out of the sewer, it stands for
                                   tahoe instruction tree (Geeze!) */
{
  tahoe_opcodeT tit_opcode;     /* The opcode. */
  byte tit_operands;            /* How many operands are here. */
  struct top tit_operand[TIT_MAX_OPERANDS];     /* Operands */
  char *tit_error;              /* "" or fatal error text */
};

/* end: tahoe-inst.h */

/* tahoe.c - tahoe-specific -
   Not part of gas yet.
   */

#include "opcode/tahoe.h"

/* This is the number to put at the beginning of the a.out file */
long omagic = OMAGIC;

/* These chars start a comment anywhere in a source file (except inside
   another comment or a quoted string. */
const char comment_chars[] = "#;";

/* These chars only start a comment at the beginning of a line. */
const char line_comment_chars[] = "#";

/* Chars that can be used to separate mant from exp in floating point nums */
const char EXP_CHARS[] = "eE";

/* Chars that mean this number is a floating point constant
   as in 0f123.456
   or    0d1.234E-12 (see exp chars above)
   Note: The Tahoe port doesn't support floating point constants. This is
         consistant with 'as' If it's needed, I can always add it later. */
const char FLT_CHARS[] = "df";

/* Also be aware that MAXIMUM_NUMBER_OF_CHARS_FOR_FLOAT may have to be
   changed in read.c .  Ideally it shouldn't have to know about it at all,
   but nothing is ideal around here.
   (The tahoe has plenty of room, so the change currently isn't needed.)
   */

static struct tit t;            /* A tahoe instruction after decoding. */

void float_cons ();
/* A table of pseudo ops (sans .), the function called, and an integer op
   that the function is called with. */

const pseudo_typeS md_pseudo_table[] =
{
  {"dfloat", float_cons, 'd'},
  {"ffloat", float_cons, 'f'},
  {0}
};
\f
/*
 * For Tahoe, relative addresses of "just the right length" are pretty easy.
 * The branch displacement is always the last operand, even in
 * synthetic instructions.
 * For Tahoe, we encode the relax_substateTs (in e.g. fr_substate) as:
 *
 *                  4       3       2       1       0        bit number
 *      ---/ /--+-------+-------+-------+-------+-------+
 *              |     what state ?      |  how long ?   |
 *      ---/ /--+-------+-------+-------+-------+-------+
 *
 * The "how long" bits are 00=byte, 01=word, 10=long.
 * This is a Un*x convention.
 * Not all lengths are legit for a given value of (what state).
 * The four states are listed below.
 * The "how long" refers merely to the displacement length.
 * The address usually has some constant bytes in it as well.
 *

States for Tahoe address relaxing.
1.      TAHOE_WIDTH_ALWAYS_JUMP (-)
        Format: "b-"
        Tahoe opcodes are:      (Hex)
                jr              11
                jbr             11
        Simple branch.
        Always, 1 byte opcode, then displacement/absolute.
        If word or longword, change opcode to brw or jmp.

        
2.      TAHOE_WIDTH_CONDITIONAL_JUMP (?)
        J<cond> where <cond> is a simple flag test.
        Format: "b?"
        Tahoe opcodes are:      (Hex)
                jneq/jnequ      21
                jeql/jeqlu      31
                jgtr            41
                jleq            51
                jgeq            81
                jlss            91
                jgtru           a1
                jlequ           b1
                jvc             c1
                jvs             d1
                jlssu/jcs       e1
                jgequ/jcc       f1
        Always, you complement 4th bit to reverse the condition.
        Always, 1-byte opcode, then 1-byte displacement.

3.      TAHOE_WIDTH_BIG_REV_JUMP (!)
        Jbc/Jbs where cond tests a memory bit.
        Format: "rlvlb!"
        Tahoe opcodes are:      (Hex)
                jbs             0e
                jbc             1e
        Always, you complement 4th bit to reverse the condition.
        Always, 1-byte opcde, longword, longword-address, 1-word-displacement

4.      TAHOE_WIDTH_BIG_NON_REV_JUMP (:)
        JaoblXX/Jbssi
        Format: "rlmlb:"
        Tahoe opcodes are:      (Hex)
                aojlss          2f
                jaoblss         2f
                aojleq          3f
                jaobleq         3f
                jbssi           5f
        Always, we cannot reverse the sense of the branch; we have a word
        displacement.

We need to modify the opcode is for class 1, 2 and 3 instructions.
After relax() we may complement the 4th bit of 2 or 3 to reverse sense of
branch.

We sometimes store context in the operand literal. This way we can figure out
after relax() what the original addressing mode was. (Was is pc_rel, or
pc_rel_disp? That sort of thing.) */
\f
/* These displacements are relative to the START address of the
   displacement which is at the start of the displacement, not the end of
   the instruction. The hardware pc_rel is at the end of the instructions.
   That's why all the displacements have the length of the displacement added
   to them. (WF + length(word))

   The first letter is Byte, Word.
   2nd letter is Forward, Backward. */
#define BF (1+ 127)
#define BB (1+-128)
#define WF (2+ 32767)
#define WB (2+-32768)
/* Dont need LF, LB because they always reach. [They are coded as 0.] */

#define C(a,b) ENCODE_RELAX(a,b)
/* This macro has no side-effects. */
#define ENCODE_RELAX(what,length) (((what) << 2) + (length))
#define RELAX_STATE(what) ((what) >> 2)
#define RELAX_LENGTH(length) ((length) && 3)

#define STATE_ALWAYS_BRANCH             (1)
#define STATE_CONDITIONAL_BRANCH        (2)
#define STATE_BIG_REV_BRANCH            (3)
#define STATE_BIG_NON_REV_BRANCH        (4)
#define STATE_PC_RELATIVE               (5)

#define STATE_BYTE                      (0)
#define STATE_WORD                      (1)
#define STATE_LONG                      (2)
#define STATE_UNDF                      (3)     /* Symbol undefined in pass1 */

/* This is the table used by gas to figure out relaxing modes. The fields are
   forward_branch reach, backward_branch reach, number of bytes it would take,
   where the next biggest branch is. */
const relax_typeS
  md_relax_table[] =
{
  {
    1, 1, 0, 0
  },                            /* error sentinel   0,0 */
  {
    1, 1, 0, 0
  },                            /* unused           0,1 */
  {
    1, 1, 0, 0
  },                            /* unused           0,2 */
  {
    1, 1, 0, 0
  },                            /* unused           0,3 */
/* Unconditional branch cases "jrb"
     The relax part is the actual displacement */
  {
    BF, BB, 1, C (1, 1)
  },                            /* brb B`foo        1,0 */
  {
    WF, WB, 2, C (1, 2)
  },                            /* brw W`foo        1,1 */
  {
    0, 0, 5, 0
  },                            /* Jmp L`foo        1,2 */
  {
    1, 1, 0, 0
  },                            /* unused           1,3 */
/* Reversible Conditional Branch. If the branch won't reach, reverse
     it, and jump over a brw or a jmp that will reach. The relax part is the
     actual address. */
  {
    BF, BB, 1, C (2, 1)
  },                            /* b<cond> B`foo    2,0 */
  {
    WF + 2, WB + 2, 4, C (2, 2)
  },                            /* brev over, brw W`foo, over: 2,1 */
  {
    0, 0, 7, 0
  },                            /* brev over, jmp L`foo, over: 2,2 */
  {
    1, 1, 0, 0
  },                            /* unused           2,3 */
/* Another type of reversable branch. But this only has a word
     displacement. */
  {
    1, 1, 0, 0
  },                            /* unused           3,0 */
  {
    WF, WB, 2, C (3, 2)
  },                            /* jbX W`foo        3,1 */
  {
    0, 0, 8, 0
  },                            /* jrevX over, jmp L`foo, over:  3,2 */
  {
    1, 1, 0, 0
  },                            /* unused           3,3 */
/* These are the non reversable branches, all of which have a word
     displacement. If I can't reach, branch over a byte branch, to a
     jump that will reach. The jumped branch jumps over the reaching
     branch, to continue with the flow of the program. It's like playing
     leap frog. */
  {
    1, 1, 0, 0
  },                            /* unused           4,0 */
  {
    WF, WB, 2, C (4, 2)
  },                            /* aobl_ W`foo      4,1 */
  {
    0, 0, 10, 0
  },                            /*aobl_ W`hop,br over,hop: jmp L^foo,over 4,2*/
  {
    1, 1, 0, 0
  },                            /* unused           4,3 */
/* Normal displacement mode, no jumping or anything like that.
     The relax points to one byte before the address, thats why all
     the numbers are up by one. */
  {
    BF + 1, BB + 1, 2, C (5, 1)
  },                            /* B^"foo"          5,0 */
  {
    WF + 1, WB + 1, 3, C (5, 2)
  },                            /* W^"foo"          5,1 */
  {
    0, 0, 5, 0
  },                            /* L^"foo"          5,2 */
  {
    1, 1, 0, 0
  },                            /* unused           5,3 */
};

#undef C
#undef BF
#undef BB
#undef WF
#undef WB
/* End relax stuff */
\f
static struct hash_control *op_hash = NULL;     /* handle of the OPCODE hash table
                                                   NULL means any use before md_begin() will
                                                   crash */

/* Init function. Build the hash table. */
void
md_begin ()
{
  struct tot *tP;
  char *errorval = "";
  int synthetic_too = 1;        /* If 0, just use real opcodes. */

  if ((op_hash = hash_new ()))
    {
      for (tP = totstrs; *tP->name && !*errorval; tP++)
        {
          errorval = hash_insert (op_hash, tP->name, &tP->detail);
        }
      if (synthetic_too)
        {
          for (tP = synthetic_totstrs; *tP->name && !*errorval; tP++)
            {
              errorval = hash_insert (op_hash, tP->name, &tP->detail);
            }
        }
    }
  else
    {
      errorval = "Virtual memory exceeded";
    }
  if (*errorval)
    as_fatal (errorval);
}                               /* md_begin */

void
md_end ()
{
}                               /* md_end */
\f
int
md_parse_option (argP, cntP, vecP)
     char **argP;
     int *cntP;
     char ***vecP;
{
  char *temp_name;              /* name for -t or -d options */
  char opt;

  switch (**argP)
    {
    case 'a':
      as_warn ("The -a option doesn't exits. (Dispite what the man page says!");

    case 'J':
      as_warn ("JUMPIFY (-J) not implemented, use psuedo ops instead.");
      break;

    case 'S':
      as_warn ("SYMBOL TABLE not implemented");
      break;                    /* SYMBOL TABLE not implemented */

    case 'T':
      as_warn ("TOKEN TRACE not implemented");
      break;                    /* TOKEN TRACE not implemented */

    case 'd':
    case 't':
      opt = **argP;
      if (**argP)
        {                       /* Rest of argument is filename. */
          temp_name = *argP;
          while (**argP)
            (*argP)++;
        }
      else if (*cntP)
        {
          while (**argP)
            (*argP)++;
          --(*cntP);
          temp_name = *++(*vecP);
          **vecP = NULL;        /* Remember this is not a file-name. */
        }
      else
        {
          as_warn ("I expected a filename after -%c.", opt);
          temp_name = "{absent}";
        }

      if (opt == 'd')
        as_warn ("Displacement length %s ignored!", temp_name);
      else
        as_warn ("I don't need or use temp. file \"%s\".", temp_name);
      break;

    case 'V':
      as_warn ("I don't use an interpass file! -V ignored");
      break;

    default:
      return 0;

    }
  return 1;
}
\f
/* The functions in this section take numbers in the machine format, and
   munges them into Tahoe byte order.
   They exist primarily for cross assembly purpose. */
void                            /* Knows about order of bytes in address. */
md_number_to_chars (con, value, nbytes)
     char con[];                /* Return 'nbytes' of chars here. */
     valueT value;              /* The value of the bits. */
     int nbytes;                /* Number of bytes in the output. */
{
  int n = nbytes;
  valueT v = value;

  con += nbytes - 1;            /* Tahoes is (Bleah!) big endian */
  while (nbytes--)
    {
      *con-- = value;           /* Lint wants & MASK_CHAR. */
      value >>= BITS_PER_CHAR;
    }
  /* XXX line number probably botched for this warning message. */
  if (value != 0 && value != -1)
    as_warn ("Displacement (%ld) long for instruction field length (%d).", v, n);
}

#ifdef comment
void                            /* Knows about order of bytes in address. */
md_number_to_imm (con, value, nbytes)
     char con[];                /* Return 'nbytes' of chars here. */
     long int value;            /* The value of the bits. */
     int nbytes;                /* Number of bytes in the output. */
{
  md_number_to_chars (con, value, nbytes);
}

#endif /* comment */

void
tc_apply_fix (fixP, val)
     fixS *fixP;
     long val;
{
  /*    char *place = fixP->fx_where + fixP->fx_frag->fr_literal; */
  /* should never be called */
  know (0);
  return;
}                               /* tc_apply_fix() */

void                            /* Knows about order of bytes in address. */
md_number_to_disp (con, value, nbytes)
     char con[];                /* Return 'nbytes' of chars here. */
     long int value;            /* The value of the bits. */
     int nbytes;                /* Number of bytes in the output. */
{
  md_number_to_chars (con, value, nbytes);
}

void                            /* Knows about order of bytes in address. */
md_number_to_field (con, value, nbytes)
     char con[];                /* Return 'nbytes' of chars here. */
     long int value;            /* The value of the bits. */
     int nbytes;                /* Number of bytes in the output. */
{
  md_number_to_chars (con, value, nbytes);
}

/* Put the bits in an order that a tahoe will understand, despite the ordering
   of the native machine.
   On Tahoe: first 4 bytes are normal unsigned big endian long,
   next three bytes are symbolnum, in kind of 3 byte big endian (least sig. byte last).
   The last byte is broken up with bit 7 as pcrel,
        bits 6 & 5 as length,
        bit 4 as extern and the last nibble as 'undefined'. */

#if comment
void
md_ri_to_chars (ri_p, ri)
     struct relocation_info *ri_p, ri;
{
  byte the_bytes[sizeof (struct relocation_info)];
  /* The reason I can't just encode these directly into ri_p is that
     ri_p may point to ri. */

  /* This is easy */
  md_number_to_chars (the_bytes, ri.r_address, sizeof (ri.r_address));

  /* now the fun stuff */
  the_bytes[4] = (ri.r_symbolnum >> 16) & 0x0ff;
  the_bytes[5] = (ri.r_symbolnum >> 8) & 0x0ff;
  the_bytes[6] = ri.r_symbolnum & 0x0ff;
  the_bytes[7] = (((ri.r_extern << 4) & 0x10) | ((ri.r_length << 5) & 0x60) |
                  ((ri.r_pcrel << 7) & 0x80)) & 0xf0;

  bcopy (the_bytes, (char *) ri_p, sizeof (struct relocation_info));
}

#endif /* comment */

/* Put the bits in an order that a tahoe will understand, despite the ordering
   of the native machine.
   On Tahoe: first 4 bytes are normal unsigned big endian long,
   next three bytes are symbolnum, in kind of 3 byte big endian (least sig. byte last).
   The last byte is broken up with bit 7 as pcrel,
        bits 6 & 5 as length,
        bit 4 as extern and the last nibble as 'undefined'. */

void 
tc_aout_fix_to_chars (where, fixP, segment_address_in_file)
     char *where;
     fixS *fixP;
     relax_addressT segment_address_in_file;
{
  long r_symbolnum;

  know (fixP->fx_addsy != NULL);

  md_number_to_chars (where,
       fixP->fx_frag->fr_address + fixP->fx_where - segment_address_in_file,
                      4);

  r_symbolnum = (S_IS_DEFINED (fixP->fx_addsy)
                 ? S_GET_TYPE (fixP->fx_addsy)
                 : fixP->fx_addsy->sy_number);

  where[4] = (r_symbolnum >> 16) & 0x0ff;
  where[5] = (r_symbolnum >> 8) & 0x0ff;
  where[6] = r_symbolnum & 0x0ff;
  where[7] = (((is_pcrel (fixP) << 7) & 0x80)
              | ((((fixP->fx_type == FX_8 || fixP->fx_type == FX_PCREL8
                    ? 0
                    : (fixP->fx_type == FX_16 || fixP->fx_type == FX_PCREL16
                       ? 1
                    : (fixP->fx_type == FX_32 || fixP->fx_type == FX_PCREL32
                       ? 2
                       : 42)))) << 5) & 0x60)
              | ((!S_IS_DEFINED (fixP->fx_addsy) << 4) & 0x10));

  return;
}                               /* tc_aout_fix_to_chars() */

/* Relocate byte stuff */
\f
/* This is for broken word. */
const int md_short_jump_size = 3;

void
md_create_short_jump (ptr, from_addr, to_addr, frag, to_symbol)
     char *ptr;
     addressT from_addr, to_addr;
     fragS *frag;
     symbolS *to_symbol;
{
  valueT offset;

  offset = to_addr - (from_addr + 1);
  *ptr++ = TAHOE_BRW;
  md_number_to_chars (ptr, offset, 2);
}

const int md_long_jump_size = 6;
const int md_reloc_size = 8;    /* Size of relocation record */

void
md_create_long_jump (ptr, from_addr, to_addr, frag, to_symbol)
     char *ptr;
     addressT from_addr, to_addr;
     fragS *frag;
     symbolS *to_symbol;
{
  valueT offset;

  offset = to_addr - (from_addr + 4);
  *ptr++ = TAHOE_JMP;
  *ptr++ = TAHOE_PC_REL_LONG;
  md_number_to_chars (ptr, offset, 4);
}
\f
/*
 *                      md_estimate_size_before_relax()
 *
 * Called just before relax().
 * Any symbol that is now undefined will not become defined, so we assumed
 * that it will be resolved by the linker.
 * Return the correct fr_subtype in the frag, for relax()
 * Return the initial "guess for fr_var" to caller. (How big I think this
 * will be.)
 * The guess for fr_var is ACTUALLY the growth beyond fr_fix.
 * Whatever we do to grow fr_fix or fr_var contributes to our returned value.
 * Although it may not be explicit in the frag, pretend fr_var starts with a
 * 0 value.
 */
int
md_estimate_size_before_relax (fragP, segment_type)
     register fragS *fragP;
     segT segment_type;         /* N_DATA or N_TEXT. */
{
  register char *p;
  register int old_fr_fix;
  /*  int pc_rel; FIXME: remove this */

  old_fr_fix = fragP->fr_fix;
  switch (fragP->fr_subtype)
    {
    case ENCODE_RELAX (STATE_PC_RELATIVE, STATE_UNDF):
      if (S_GET_SEGMENT (fragP->fr_symbol) == segment_type)
        {
          /* The symbol was in the same segment as the opcode, and it's
         a real pc_rel case so it's a relaxable case. */
          fragP->fr_subtype = ENCODE_RELAX (STATE_PC_RELATIVE, STATE_BYTE);
        }
      else
        {
          /* This case is still undefined, so asume it's a long word for the
         linker to fix. */
          p = fragP->fr_literal + old_fr_fix;
          *p |= TAHOE_PC_OR_LONG;
          /* We now know how big it will be, one long word. */
          fragP->fr_fix += 1 + 4;
          fix_new (fragP, old_fr_fix + 1, fragP->fr_symbol,
                   fragP->fr_offset, FX_PCREL32, NULL);
          frag_wane (fragP);
        }
      break;

    case ENCODE_RELAX (STATE_CONDITIONAL_BRANCH, STATE_UNDF):
      if (S_GET_SEGMENT (fragP->fr_symbol) == segment_type)
        {
          fragP->fr_subtype = ENCODE_RELAX (STATE_CONDITIONAL_BRANCH, STATE_BYTE);
        }
      else
        {
          p = fragP->fr_literal + old_fr_fix;
          *fragP->fr_opcode ^= 0x10;    /* Reverse sense of branch. */
          *p++ = 6;
          *p++ = TAHOE_JMP;
          *p++ = TAHOE_PC_REL_LONG;
          fragP->fr_fix += 1 + 1 + 1 + 4;
          fix_new (fragP, old_fr_fix + 3, fragP->fr_symbol,
                   fragP->fr_offset, FX_PCREL32, NULL);
          frag_wane (fragP);
        }
      break;

    case ENCODE_RELAX (STATE_BIG_REV_BRANCH, STATE_UNDF):
      if (S_GET_SEGMENT (fragP->fr_symbol) == segment_type)
        {
          fragP->fr_subtype =
            ENCODE_RELAX (STATE_BIG_REV_BRANCH, STATE_WORD);
        }
      else
        {
          p = fragP->fr_literal + old_fr_fix;
          *fragP->fr_opcode ^= 0x10;    /* Reverse sense of branch. */
          *p++ = 0;
          *p++ = 6;
          *p++ = TAHOE_JMP;
          *p++ = TAHOE_PC_REL_LONG;
          fragP->fr_fix += 2 + 2 + 4;
          fix_new (fragP, old_fr_fix + 4, fragP->fr_symbol,
                   fragP->fr_offset, FX_PCREL32, NULL);
          frag_wane (fragP);
        }
      break;

    case ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH, STATE_UNDF):
      if (S_GET_SEGMENT (fragP->fr_symbol) == segment_type)
        {
          fragP->fr_subtype = ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH, STATE_WORD);
        }
      else
        {
          p = fragP->fr_literal + old_fr_fix;
          *p++ = 2;
          *p++ = 0;
          *p++ = TAHOE_BRB;
          *p++ = 6;
          *p++ = TAHOE_JMP;
          *p++ = TAHOE_PC_REL_LONG;
          fragP->fr_fix += 2 + 2 + 2 + 4;
          fix_new (fragP, old_fr_fix + 6, fragP->fr_symbol,
                   fragP->fr_offset, FX_PCREL32, NULL);
          frag_wane (fragP);
        }
      break;

    case ENCODE_RELAX (STATE_ALWAYS_BRANCH, STATE_UNDF):
      if (S_GET_SEGMENT (fragP->fr_symbol) == segment_type)
        {
          fragP->fr_subtype = ENCODE_RELAX (STATE_ALWAYS_BRANCH, STATE_BYTE);
        }
      else
        {
          p = fragP->fr_literal + old_fr_fix;
          *fragP->fr_opcode = TAHOE_JMP;
          *p++ = TAHOE_PC_REL_LONG;
          fragP->fr_fix += 1 + 4;
          fix_new (fragP, old_fr_fix + 1, fragP->fr_symbol,
                   fragP->fr_offset, FX_PCREL32, NULL);
          frag_wane (fragP);
        }
      break;

    default:
      break;
    }
  return (fragP->fr_var + fragP->fr_fix - old_fr_fix);
}                               /* md_estimate_size_before_relax() */
\f
/*
 *                      md_convert_frag();
 *
 * Called after relax() is finished.
 * In:  Address of frag.
 *      fr_type == rs_machine_dependent.
 *      fr_subtype is what the address relaxed to.
 *
 * Out: Any fixSs and constants are set up.
 *      Caller will turn frag into a ".space 0".
 */
void
md_convert_frag (headers, fragP)
     object_headers *headers;
     register fragS *fragP;
{
  register char *addressP;      /* -> _var to change. */
  register char *opcodeP;       /* -> opcode char(s) to change. */
  register short int length_code;       /* 2=long 1=word 0=byte */
  register short int extension = 0;     /* Size of relaxed address.
                                   Added to fr_fix: incl. ALL var chars. */
  register symbolS *symbolP;
  register long int where;
  register long int address_of_var;
  /* Where, in file space, is _var of *fragP? */
  register long int target_address;
  /* Where, in file space, does addr point? */

  know (fragP->fr_type == rs_machine_dependent);
  length_code = RELAX_LENGTH (fragP->fr_subtype);
  know (length_code >= 0 && length_code < 3);
  where = fragP->fr_fix;
  addressP = fragP->fr_literal + where;
  opcodeP = fragP->fr_opcode;
  symbolP = fragP->fr_symbol;
  know (symbolP);
  target_address = S_GET_VALUE (symbolP) + fragP->fr_offset;
  address_of_var = fragP->fr_address + where;
  switch (fragP->fr_subtype)
    {
    case ENCODE_RELAX (STATE_PC_RELATIVE, STATE_BYTE):
      /* *addressP holds the registers number, plus 0x10, if it's deferred
       mode. To set up the right mode, just OR the size of this displacement */
      /* Byte displacement. */
      *addressP++ |= TAHOE_PC_OR_BYTE;
      *addressP = target_address - (address_of_var + 2);
      extension = 2;
      break;

    case ENCODE_RELAX (STATE_PC_RELATIVE, STATE_WORD):
      /* Word displacement. */
      *addressP++ |= TAHOE_PC_OR_WORD;
      md_number_to_chars (addressP, target_address - (address_of_var + 3), 2);
      extension = 3;
      break;

    case ENCODE_RELAX (STATE_PC_RELATIVE, STATE_LONG):
      /* Long word displacement. */
      *addressP++ |= TAHOE_PC_OR_LONG;
      md_number_to_chars (addressP, target_address - (address_of_var + 5), 4);
      extension = 5;
      break;

    case ENCODE_RELAX (STATE_CONDITIONAL_BRANCH, STATE_BYTE):
      *addressP = target_address - (address_of_var + 1);
      extension = 1;
      break;

    case ENCODE_RELAX (STATE_CONDITIONAL_BRANCH, STATE_WORD):
      *opcodeP ^= 0x10;         /* Reverse sense of test. */
      *addressP++ = 3;          /* Jump over word branch */
      *addressP++ = TAHOE_BRW;
      md_number_to_chars (addressP, target_address - (address_of_var + 4), 2);
      extension = 4;
      break;

    case ENCODE_RELAX (STATE_CONDITIONAL_BRANCH, STATE_LONG):
      *opcodeP ^= 0x10;         /* Reverse sense of test. */
      *addressP++ = 6;
      *addressP++ = TAHOE_JMP;
      *addressP++ = TAHOE_PC_REL_LONG;
      md_number_to_chars (addressP, target_address, 4);
      extension = 7;
      break;

    case ENCODE_RELAX (STATE_ALWAYS_BRANCH, STATE_BYTE):
      *addressP = target_address - (address_of_var + 1);
      extension = 1;
      break;

    case ENCODE_RELAX (STATE_ALWAYS_BRANCH, STATE_WORD):
      *opcodeP = TAHOE_BRW;
      md_number_to_chars (addressP, target_address - (address_of_var + 2), 2);
      extension = 2;
      break;

    case ENCODE_RELAX (STATE_ALWAYS_BRANCH, STATE_LONG):
      *opcodeP = TAHOE_JMP;
      *addressP++ = TAHOE_PC_REL_LONG;
      md_number_to_chars (addressP, target_address - (address_of_var + 5), 4);
      extension = 5;
      break;

    case ENCODE_RELAX (STATE_BIG_REV_BRANCH, STATE_WORD):
      md_number_to_chars (addressP, target_address - (address_of_var + 2), 2);
      extension = 2;
      break;

    case ENCODE_RELAX (STATE_BIG_REV_BRANCH, STATE_LONG):
      *opcodeP ^= 0x10;
      *addressP++ = 0;
      *addressP++ = 6;
      *addressP++ = TAHOE_JMP;
      *addressP++ = TAHOE_PC_REL_LONG;
      md_number_to_chars (addressP, target_address, 4);
      extension = 8;
      break;

    case ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH, STATE_WORD):
      md_number_to_chars (addressP, target_address - (address_of_var + 2), 2);
      extension = 2;
      break;

    case ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH, STATE_LONG):
      *addressP++ = 0;
      *addressP++ = 2;
      *addressP++ = TAHOE_BRB;
      *addressP++ = 6;
      *addressP++ = TAHOE_JMP;
      *addressP++ = TAHOE_PC_REL_LONG;
      md_number_to_chars (addressP, target_address, 4);
      extension = 10;
      break;

    default:
      BAD_CASE (fragP->fr_subtype);
      break;
    }
  fragP->fr_fix += extension;
}                               /* md_convert_frag */
\f

/* This is the stuff for md_assemble. */
#define FP_REG 13
#define SP_REG 14
#define PC_REG 15
#define BIGGESTREG PC_REG

/*
 * Parse the string pointed to by START
 * If it represents a valid register, point START to the character after
 * the last valid register char, and return the register number (0-15).
 * If invalid, leave START alone, return -1.
 * The format has to be exact. I don't do things like eat leading zeros
 * or the like.
 * Note: This doesn't check for the next character in the string making
 * this invalid. Ex: R123 would return 12, it's the callers job to check
 * what start is point to apon return.
 *
 * Valid registers are R1-R15, %1-%15, FP (13), SP (14), PC (15)
 * Case doesn't matter.
 */
int
tahoe_reg_parse (start)
     char **start;              /* A pointer to the string to parse. */
{
  register char *regpoint = *start;
  register int regnum = -1;

  switch (*regpoint++)
    {
    case '%':                   /* Registers can start with a %,
                                   R or r, and then a number. */
    case 'R':
    case 'r':
      if (isdigit (*regpoint))
        {
          /* Got the first digit. */
          regnum = *regpoint++ - '0';
          if ((regnum == 1) && isdigit (*regpoint))
            {
              /* Its a two digit number. */
              regnum = 10 + (*regpoint++ - '0');
              if (regnum > BIGGESTREG)
                {               /* Number too big? */
                  regnum = -1;
                }
            }
        }
      break;
    case 'F':                   /* Is it the FP */
    case 'f':
      switch (*regpoint++)
        {
        case 'p':
        case 'P':
          regnum = FP_REG;
        }
      break;
    case 's':                   /* How about the SP */
    case 'S':
      switch (*regpoint++)
        {
        case 'p':
        case 'P':
          regnum = SP_REG;
        }
      break;
    case 'p':                   /* OR the PC even */
    case 'P':
      switch (*regpoint++)
        {
        case 'c':
        case 'C':
          regnum = PC_REG;
        }
      break;
    }

  if (regnum != -1)
    {                           /* No error, so move string pointer */
      *start = regpoint;
    }
  return regnum;                /* Return results */
}                               /* tahoe_reg_parse */
\f
/*
 * This chops up an operand and figures out its modes and stuff.
 * It's a little touchy about extra characters.
 * Optex to start with one extra character so it can be overwritten for
 * the backward part of the parsing.
 * You can't put a bunch of extra characters in side to
 * make the command look cute. ie: * foo ( r1 ) [  r0 ]
 * If you like doing a lot of typing, try COBOL!
 * Actually, this parser is a little weak all around. It's designed to be
 * used with compliers, so I emphisise correct decoding of valid code quickly
 * rather that catching every possable error.
 * Note: This uses the expression function, so save input_line_pointer before
 * calling.
 *
 * Sperry defines the semantics of address modes (and values)
 * by a two-letter code, explained here.
 *
 *   letter 1:   access type
 *
 *     a         address calculation - no data access, registers forbidden
 *     b         branch displacement
 *     m         read - let go of bus - write back "modify"
 *     r         read
 *     w         write
 *     v         bit field address: like 'a' but registers are OK
 *
 *   letter 2:   data type (i.e. width, alignment)
 *
 *     b         byte
 *     w         word
 *     l         longword
 *     q         quadword (Even regs < 14 allowed) (if 12, you get a warning)
 *     -         unconditional synthetic jbr operand
 *     ?         simple synthetic reversable branch operand
 *     !         complex synthetic reversable branch operand
 *     :         complex synthetic non-reversable branch operand
 *
 * The '-?!:' letter 2's are not for external consumption. They are used
 * by GAS for psuedo ops relaxing code.
 *
 * After parsing topP has:
 *
 *   top_ndx:        -1, or the index register. eg 7=[R7]
 *   top_reg:        -1, or register number. eg 7 = R7 or (R7)
 *   top_mode:       The addressing mode byte. This byte, defines which of
 *                   the 11 modes opcode is.
 *   top_access:     Access type wanted for this opperand 'b'branch ' '
 *                   no-instruction 'amrvw'
 *   top_width:      Operand width expected, one of "bwlq?-:!"
 *   exp_of_operand: The expression as parsed by expression()
 *   top_dispsize:   Number of bytes in the displacement if we can figure it
 *                   out and it's relavent.
 *
 * Need syntax checks built.
 */

void
tip_op (optex, topP)
     char *optex;               /* The users text input, with one leading character */
     struct top *topP;          /* The tahoe instruction with some fields already set:
                         in: access, width
                         out: ndx, reg, mode, error, dispsize */

{
  int mode = 0;                 /* This operand's mode. */
  char segfault = *optex;       /* To keep the back parsing from freaking. */
  char *point = optex + 1;      /* Parsing from front to back. */
  char *end;                    /* Parsing from back to front. */
  int reg = -1;                 /* major register, -1 means absent */
  int imreg = -1;               /* Major register in immediate mode */
  int ndx = -1;                 /* index register number, -1 means absent */
  char dec_inc = ' ';           /* Is the SP auto-incremented '+' or
                                   auto-decremented '-' or neither ' '. */
  int immediate = 0;            /* 1 if '$' immediate mode */
  int call_width = 0;           /* If the caller casts the displacement */
  int abs_width = 0;            /* The width of the absolute displacment */
  int com_width = 0;            /* Displacement width required by branch */
  int deferred = 0;             /* 1 if '*' deferral is used */
  byte disp_size = 0;           /* How big is this operand. 0 == don't know */
  char *op_bad = "";            /* Bad operand error */

  char *tp, *temp, c;           /* Temporary holders */

  char access = topP->top_access;       /* Save on a deref. */
  char width = topP->top_width;

  int really_none = 0;          /* Empty expressions evaluate to 0
                                   but I need to know if it's there or not */
  expressionS *expP;            /* -> expression values for this operand */

  /* Does this command restrict the displacement size. */
  if (access == 'b')
    com_width = (width == 'b' ? 1 :
                 (width == 'w' ? 2 :
                  (width == 'l' ? 4 : 0)));

  *optex = '\0';                /* This is kind of a back stop for all
                                   the searches to fail on if needed.*/
  if (*point == '*')
    {                           /* A dereference? */
      deferred = 1;
      point++;
    }

  /* Force words into a certain mode */
  /* Bitch, Bitch, Bitch! */
  /*
   * Using the ^ operator is ambigous. If I have an absolute label
   * called 'w' set to, say 2, and I have the expression 'w^1', do I get
   * 1, forced to be in word displacement mode, or do I get the value of
   * 'w' or'ed with 1 (3 in this case).
   * The default is 'w' as an offset, so that's what I use.
   * Stick with `, it does the same, and isn't ambig.
   */

  if (*point != '\0' && ((point[1] == '^') || (point[1] == '`')))
    switch (*point)
      {
      case 'b':
      case 'B':
      case 'w':
      case 'W':
      case 'l':
      case 'L':
        if (com_width)
          as_warn ("Casting a branch displacement is bad form, and is ignored.");
        else
          {
            c = (isupper (*point) ? tolower (*point) : *point);
            call_width = ((c == 'b') ? 1 :
                          ((c == 'w') ? 2 : 4));
          }
        point += 2;
        break;
      }

  /* Setting immediate mode */
  if (*point == '$')
    {
      immediate = 1;
      point++;
    }

  /*
   * I've pulled off all the easy stuff off the front, move to the end and
   * yank.
   */

  for (end = point; *end != '\0'; end++)        /* Move to the end. */
    ;

  if (end != point)             /* Null string? */
    end--;

  if (end > point && *end == ' ' && end[-1] != '\'')
    end--;                      /* Hop white space */

  /* Is this an index reg. */
  if ((*end == ']') && (end[-1] != '\''))
    {
      temp = end;

      /* Find opening brace. */
      for (--end; (*end != '[' && end != point); end--)
        ;

      /* If I found the opening brace, get the index register number. */
      if (*end == '[')
        {
          tp = end + 1;         /* tp should point to the start of a reg. */
          ndx = tahoe_reg_parse (&tp);
          if (tp != temp)
            {                   /* Reg. parse error. */
              ndx = -1;
            }
          else
            {
              end--;            /* Found it, move past brace. */
            }
          if (ndx == -1)
            {
              op_bad = "Couldn't parse the [index] in this operand.";
              end = point;      /* Force all the rest of the tests to fail. */
            }
        }
      else
        {
          op_bad = "Couldn't find the opening '[' for the index of this operand.";
          end = point;          /* Force all the rest of the tests to fail. */
        }
    }

  /* Post increment? */
  if (*end == '+')
    {
      dec_inc = '+';
      /* was:    *end--; */
      end--;
    }

  /* register in parens? */
  if ((*end == ')') && (end[-1] != '\''))
    {
      temp = end;

      /* Find opening paren. */
      for (--end; (*end != '(' && end != point); end--)
        ;

      /* If I found the opening paren, get the register number. */
      if (*end == '(')
        {
          tp = end + 1;
          reg = tahoe_reg_parse (&tp);
          if (tp != temp)
            {
              /* Not a register, but could be part of the expression. */
              reg = -1;
              end = temp;       /* Rest the pointer back */
            }
          else
            {
              end--;            /* Found the reg. move before opening paren. */
            }
        }
      else
        {
          op_bad = "Couldn't find the opening '(' for the deref of this operand.";
          end = point;          /* Force all the rest of the tests to fail. */
        }
    }

  /* Pre decrement? */
  if (*end == '-')
    {
      if (dec_inc != ' ')
        {
          op_bad = "Operand can't be both pre-inc and post-dec.";
          end = point;
        }
      else
        {
          dec_inc = '-';
          /* was:      *end--; */
          end--;
        }
    }

  /*
   * Everything between point and end is the 'expression', unless it's
   * a register name.
   */

  c = end[1];
  end[1] = '\0';

  tp = point;
  imreg = tahoe_reg_parse (&point);     /* Get the immediate register
                                      if it is there.*/
  if (*point != '\0')
    {
      /* If there is junk after point, then the it's not immediate reg. */
      point = tp;
      imreg = -1;
    }

  if (imreg != -1 && reg != -1)
    op_bad = "I parsed 2 registers in this operand.";

  /*
   * Evaluate whats left of the expression to see if it's valid.
   * Note again: This assumes that the calling expression has saved
   * input_line_pointer. (Nag, nag, nag!)
   */

  if (*op_bad == '\0')
    {
      /* statement has no syntax goofs yet: lets sniff the expression */
      input_line_pointer = point;
      expP = &(topP->exp_of_operand);
      topP->seg_of_operand = expression (expP);
      switch (expP->X_op)
        {
        case O_absent:
          /* No expression. For BSD4.2 compatibility, missing expression is
             absolute 0 */
          expP->X_op = O_constant;
          expP->X_add_number = 0;
          really_none = 1;
        case O_constant:
          /* for SEG_ABSOLUTE, we shouldnt need to set X_op_symbol,
             X_add_symbol to any particular value. */
          /* But, we will program defensively. Since this situation occurs
             rarely so it costs us little to do so. */
          expP->X_add_symbol = NULL;
          expP->X_op_symbol = NULL;
          /* How many bytes are needed to express this abs value? */
          abs_width =
            ((((expP->X_add_number & 0xFFFFFF80) == 0) ||
              ((expP->X_add_number & 0xFFFFFF80) == 0xFFFFFF80)) ? 1 :
             (((expP->X_add_number & 0xFFFF8000) == 0) ||
              ((expP->X_add_number & 0xFFFF8000) == 0xFFFF8000)) ? 2 : 4);

        case O_symbol:
          break;

        default:
          /*
           * Major bug. We can't handle the case of a operator
           * expression in a synthetic opcode variable-length
           * instruction.  We don't have a frag type that is smart
           * enough to relax a operator, and so we just force all
           * operators to behave like SEG_PASS1s.  Clearly, if there is
           * a demand we can invent a new or modified frag type and
           * then coding up a frag for this case will be easy.
           */
          need_pass_2 = 1;
          op_bad = "Can't relocate expression error.";
          break;

        case O_big:
          /* This is an error. Tahoe doesn't allow any expressions
             bigger that a 32 bit long word. Any bigger has to be referenced
             by address. */
          op_bad = "Expression is too large for a 32 bits.";
          break;
        }
      if (*input_line_pointer != '\0')
        {
          op_bad = "Junk at end of expression.";
        }
    }

  end[1] = c;

  /* I'm done, so restore optex */
  *optex = segfault;


  /*
   * At this point in the game, we (in theory) have all the components of
   * the operand at least parsed. Now it's time to check for syntax/semantic
   * errors, and build the mode.
   * This is what I have:
   *   deferred = 1 if '*'
   *   call_width = 0,1,2,4
   *   abs_width = 0,1,2,4
   *   com_width = 0,1,2,4
   *   immediate = 1 if '$'
   *   ndx = -1 or reg num
   *   dec_inc = '-' or '+' or ' '
   *   reg = -1 or reg num
   *   imreg = -1 or reg num
   *   topP->exp_of_operand
   *   really_none
   */
  /* Is there a displacement size? */
  disp_size = (call_width ? call_width :
               (com_width ? com_width :
                abs_width ? abs_width : 0));

  if (*op_bad == '\0')
    {
      if (imreg != -1)
        {
          /* Rn */
          mode = TAHOE_DIRECT_REG;
          if (deferred || immediate || (dec_inc != ' ') ||
              (reg != -1) || !really_none)
            op_bad = "Syntax error in direct register mode.";
          else if (ndx != -1)
            op_bad = "You can't index a register in direct register mode.";
          else if (imreg == SP_REG && access == 'r')
            op_bad =
              "SP can't be the source operand with direct register addressing.";
          else if (access == 'a')
            op_bad = "Can't take the address of a register.";
          else if (access == 'b')
            op_bad = "Direct Register can't be used in a branch.";
          else if (width == 'q' && ((imreg % 2) || (imreg > 13)))
            op_bad = "For quad access, the register must be even and < 14.";
          else if (call_width)
            op_bad = "You can't cast a direct register.";

          if (*op_bad == '\0')
            {
              /* No errors, check for warnings */
              if (width == 'q' && imreg == 12)
                as_warn ("Using reg 14 for quadwords can tromp the FP register.");

              reg = imreg;
            }

          /* We know: imm = -1 */
        }
      else if (dec_inc == '-')
        {
          /* -(SP) */
          mode = TAHOE_AUTO_DEC;
          if (deferred || immediate || !really_none)
            op_bad = "Syntax error in auto-dec mode.";
          else if (ndx != -1)
            op_bad = "You can't have an index auto dec mode.";
          else if (access == 'r')
            op_bad = "Auto dec mode cant be used for reading.";
          else if (reg != SP_REG)
            op_bad = "Auto dec only works of the SP register.";
          else if (access == 'b')
            op_bad = "Auto dec can't be used in a branch.";
          else if (width == 'q')
            op_bad = "Auto dec won't work with quadwords.";

          /* We know: imm = -1, dec_inc != '-' */
        }
      else if (dec_inc == '+')
        {
          if (immediate || !really_none)
            op_bad = "Syntax error in one of the auto-inc modes.";
          else if (deferred)
            {
              /* *(SP)+ */
              mode = TAHOE_AUTO_INC_DEFERRED;
              if (reg != SP_REG)
                op_bad = "Auto inc deferred only works of the SP register.";
              else if (ndx != -1)
                op_bad = "You can't have an index auto inc deferred mode.";
              else if (access == 'b')
                op_bad = "Auto inc can't be used in a branch.";
            }
          else
            {
              /* (SP)+ */
              mode = TAHOE_AUTO_INC;
              if (access == 'm' || access == 'w')
                op_bad = "You can't write to an auto inc register.";
              else if (reg != SP_REG)
                op_bad = "Auto inc only works of the SP register.";
              else if (access == 'b')
                op_bad = "Auto inc can't be used in a branch.";
              else if (width == 'q')
                op_bad = "Auto inc won't work with quadwords.";
              else if (ndx != -1)
                op_bad = "You can't have an index in auto inc mode.";
            }

          /* We know: imm = -1, dec_inc == ' ' */
        }
      else if (reg != -1)
        {
          if ((ndx != -1) && (reg == SP_REG))
            op_bad = "You can't index the sp register.";
          if (deferred)
            {
              /* *<disp>(Rn) */
              mode = TAHOE_REG_DISP_DEFERRED;
              if (immediate)
                op_bad = "Syntax error in register displaced mode.";
            }
          else if (really_none)
            {
              /* (Rn) */
              mode = TAHOE_REG_DEFERRED;
              /* if reg = SP then cant be indexed */
            }
          else
            {
              /* <disp>(Rn) */
              mode = TAHOE_REG_DISP;
            }

          /* We know: imm = -1, dec_inc == ' ', Reg = -1 */
        }
      else
        {
          if (really_none)
            op_bad = "An offest is needed for this operand.";
          if (deferred && immediate)
            {
              /* *$<ADDR> */
              mode = TAHOE_ABSOLUTE_ADDR;
              disp_size = 4;
            }
          else if (immediate)
            {
              /* $<disp> */
              mode = TAHOE_IMMEDIATE;
              if (ndx != -1)
                op_bad = "You can't index a register in immediate mode.";
              if (access == 'a')
                op_bad = "Immediate access can't be used as an address.";
              /* ponder the wisdom of a cast because it doesn't do any good. */
            }
          else if (deferred)
            {
              /* *<disp> */
              mode = TAHOE_DISP_REL_DEFERRED;
            }
          else
            {
              /* <disp> */
              mode = TAHOE_DISPLACED_RELATIVE;
            }
        }
    }

  /*
   * At this point, all the errors we can do have be checked for.
   * We can build the 'top'. */

  topP->top_ndx = ndx;
  topP->top_reg = reg;
  topP->top_mode = mode;
  topP->top_error = op_bad;
  topP->top_dispsize = disp_size;
}                               /* tip_op */
\f
/*
 *                  t i p ( )
 *
 * This converts a string into a tahoe instruction.
 * The string must be a bare single instruction in tahoe (with BSD4 frobs)
 * format.
 * It provides at most one fatal error message (which stops the scan)
 * some warning messages as it finds them.
 * The tahoe instruction is returned in exploded form.
 *
 * The exploded instruction is returned to a struct tit of your choice.
 * #include "tahoe-inst.h" to know what a struct tit is.
 *
 */

static void
tip (titP, instring)
     struct tit *titP;          /* We build an exploded instruction here. */
     char *instring;            /* Text of a vax instruction: we modify. */
{
  register struct tot_wot *twP = NULL;  /* How to bit-encode this opcode. */
  register char *p;             /* 1/skip whitespace.2/scan vot_how */
  register char *q;             /*  */
  register unsigned char count; /* counts number of operands seen */
  register struct top *operandp;/* scan operands in struct tit */
  register char *alloperr = ""; /* error over all operands */
  register char c;              /* Remember char, (we clobber it
                                   with '\0' temporarily). */
  char *save_input_line_pointer;

  if (*instring == ' ')
    ++instring;                 /* Skip leading whitespace. */
  for (p = instring; *p && *p != ' '; p++)
    ;                           /* MUST end in end-of-string or
                                   exactly 1 space. */
  /* Scanned up to end of operation-code. */
  /* Operation-code is ended with whitespace. */
  if (p == instring)
    {
      titP->tit_error = "No operator";
      count = 0;
      titP->tit_opcode = 0;
    }
  else
    {
      c = *p;
      *p = '\0';
      /*
     * Here with instring pointing to what better be an op-name, and p
     * pointing to character just past that.
     * We trust instring points to an op-name, with no whitespace.
     */
      twP = (struct tot_wot *) hash_find (op_hash, instring);
      *p = c;                   /* Restore char after op-code. */
      if (twP == 0)
        {
          titP->tit_error = "Unknown operator";
          count = 0;
          titP->tit_opcode = 0;
        }
      else
        {
          /*
       * We found a match! So lets pick up as many operands as the
       * instruction wants, and even gripe if there are too many.
       * We expect comma to seperate each operand.
       * We let instring track the text, while p tracks a part of the
       * struct tot.
       */

          count = 0;            /* no operands seen yet */
          instring = p + (*p != '\0');  /* point past the operation code */
          /* tip_op() screws with the input_line_pointer, so save it before
         I jump in */
          save_input_line_pointer = input_line_pointer;
          for (p = twP->args, operandp = titP->tit_operand;
               !*alloperr && *p;
               operandp++, p += 2)
            {
              /*
         * Here to parse one operand. Leave instring pointing just
         * past any one ',' that marks the end of this operand.
         */
              if (!p[1])
                as_fatal ("Compiler bug: ODD number of bytes in arg structure %s.",
                          twP->args);
              else if (*instring)
                {
                  for (q = instring; (*q != ',' && *q != '\0'); q++)
                    {
                      if (*q == '\'' && q[1] != '\0')   /* Jump quoted characters */
                        q++;
                    }
                  c = *q;
                  /*
           * Q points to ',' or '\0' that ends argument. C is that
           * character.
           */
                  *q = '\0';
                  operandp->top_access = p[0];
                  operandp->top_width = p[1];
                  tip_op (instring - 1, operandp);
                  *q = c;       /* Restore input text. */
                  if (*(operandp->top_error))
                    {
                      alloperr = operandp->top_error;
                    }
                  instring = q + (c ? 1 : 0);   /* next operand (if any) */
                  count++;      /*  won another argument, may have an operr */
                }
              else
                alloperr = "Not enough operands";
            }
          /* Restore the pointer. */
          input_line_pointer = save_input_line_pointer;

          if (!*alloperr)
            {
              if (*instring == ' ')
                instring++;     /* Skip whitespace. */
              if (*instring)
                alloperr = "Too many operands";
            }
          titP->tit_error = alloperr;
        }
    }

  titP->tit_opcode = twP->code; /* The op-code. */
  titP->tit_operands = count;
}                               /* tip */
\f
/* md_assemble() emit frags for 1 instruction */
void
md_assemble (instruction_string)
     char *instruction_string;  /* A string: assemble 1 instruction. */
{
  char *p;
  register struct top *operandP;/* An operand. Scans all operands. */
  /*  char c_save;      fixme: remove this line *//* What used to live after an expression. */
  /*  struct frag *fragP;       fixme: remove this line *//* Fragment of code we just made. */
  /*  register struct top *end_operandP; fixme: remove this line *//* -> slot just after last operand
                                        Limit of the for (each operand). */
  register expressionS *expP;   /* -> expression values for this operand */

  /* These refer to an instruction operand expression. */
  segT to_seg;                  /* Target segment of the address.        */

  register valueT this_add_number;
  register struct symbol *this_add_symbol;      /* +ve (minuend) symbol. */

  /*  tahoe_opcodeT opcode_as_number; fixme: remove this line *//* The opcode as a number. */
  char *opcodeP;                /* Where it is in a frag. */
  /*  char *opmodeP;    fixme: remove this line *//* Where opcode type is, in a frag. */

  int dispsize;                 /* From top_dispsize: tahoe_operand_width
                                   (in bytes) */
  int is_undefined;             /* 1 if operand expression's
                                   segment not known yet. */
  int pc_rel;                   /* Is this operand pc relative? */

  /* Decode the operand. */
  tip (&t, instruction_string);

  /*
   * Check to see if this operand decode properly.
   * Notice that we haven't made any frags yet.
   * If it goofed, then this instruction will wedge in any pass,
   * and we can safely flush it, without causing interpass symbol phase
   * errors. That is, without changing label values in different passes.
   */
  if (*t.tit_error)
    {
      as_warn ("Ignoring statement due to \"%s\"", t.tit_error);
    }
  else
    {
      /* We saw no errors in any operands - try to make frag(s) */
      /* Emit op-code. */
      /* Remember where it is, in case we want to modify the op-code later. */
      opcodeP = frag_more (1);
      *opcodeP = t.tit_opcode;
      /* Now do each operand. */
      for (operandP = t.tit_operand;
           operandP < t.tit_operand + t.tit_operands;
           operandP++)
        {                       /* for each operand */
          expP = &(operandP->exp_of_operand);
          if (operandP->top_ndx >= 0)
            {
              /* Indexed addressing byte
           Legality of indexed mode already checked: it is OK */
              FRAG_APPEND_1_CHAR (0x40 + operandP->top_ndx);
            }                   /* if(top_ndx>=0) */

          /* Here to make main operand frag(s). */
          this_add_number = expP->X_add_number;
          this_add_symbol = expP->X_add_symbol;
          to_seg = operandP->seg_of_operand;
          know (to_seg == SEG_UNKNOWN || \
                to_seg == SEG_ABSOLUTE || \
                to_seg == SEG_DATA || \
                to_seg == SEG_TEXT || \
                to_seg == SEG_BSS);
          is_undefined = (to_seg == SEG_UNKNOWN);
          /* Do we know how big this opperand is? */
          dispsize = operandP->top_dispsize;
          pc_rel = 0;
          /* Deal with the branch possabilities. (Note, this doesn't include
         jumps.)*/
          if (operandP->top_access == 'b')
            {
              /* Branches must be expressions. A psuedo branch can also jump to
           an absolute address. */
              if (to_seg == now_seg || is_undefined)
                {
                  /* If is_undefined, then it might BECOME now_seg by relax time. */
                  if (dispsize)
                    {
                      /* I know how big the branch is supposed to be (it's a normal
               branch), so I set up the frag, and let GAS do the rest. */
                      p = frag_more (dispsize);
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                               size_to_fx (dispsize, 1),
                               NULL);
                    }
                  else
                    {
                      /* (to_seg==now_seg || to_seg == SEG_UNKNOWN) && dispsize==0 */
                      /* If we don't know how big it is, then its a synthetic branch,
               so we set up a simple relax state. */
                      switch (operandP->top_width)
                        {
                        case TAHOE_WIDTH_CONDITIONAL_JUMP:
                          /* Simple (conditional) jump. I may have to reverse the
                 condition of opcodeP, and then jump to my destination.
                 I set 1 byte aside for the branch off set, and could need 6
                 more bytes for the pc_rel jump */
                          frag_var (rs_machine_dependent, 7, 1,
                                    ENCODE_RELAX (STATE_CONDITIONAL_BRANCH,
                                    is_undefined ? STATE_UNDF : STATE_BYTE),
                                 this_add_symbol, this_add_number, opcodeP);
                          break;
                        case TAHOE_WIDTH_ALWAYS_JUMP:
                          /* Simple (unconditional) jump. I may have to convert this to
                 a word branch, or an absolute jump. */
                          frag_var (rs_machine_dependent, 5, 1,
                                    ENCODE_RELAX (STATE_ALWAYS_BRANCH,
                                    is_undefined ? STATE_UNDF : STATE_BYTE),
                                 this_add_symbol, this_add_number, opcodeP);
                          break;
                          /* The smallest size for the next 2 cases is word. */
                        case TAHOE_WIDTH_BIG_REV_JUMP:
                          frag_var (rs_machine_dependent, 8, 2,
                                    ENCODE_RELAX (STATE_BIG_REV_BRANCH,
                                    is_undefined ? STATE_UNDF : STATE_WORD),
                                    this_add_symbol, this_add_number,
                                    opcodeP);
                          break;
                        case TAHOE_WIDTH_BIG_NON_REV_JUMP:
                          frag_var (rs_machine_dependent, 10, 2,
                                    ENCODE_RELAX (STATE_BIG_NON_REV_BRANCH,
                                    is_undefined ? STATE_UNDF : STATE_WORD),
                                    this_add_symbol, this_add_number,
                                    opcodeP);
                          break;
                        default:
                          as_fatal ("Compliler bug: Got a case (%d) I wasn't expecting.",
                                    operandP->top_width);
                        }
                    }
                }
              else
                {
                  /* to_seg != now_seg && to_seg != seg_unknown (still in branch)
             In other words, I'm jumping out of my segment so extend the
             branches to jumps, and let GAS fix them. */

                  /* These are "branches" what will always be branches around a jump
             to the correct addresss in real life.
             If to_seg is SEG_ABSOLUTE, just encode the branch in,
             else let GAS fix the address. */

                  switch (operandP->top_width)
                    {
                      /* The theory:
               For SEG_ABSOLUTE, then mode is ABSOLUTE_ADDR, jump
               to that addresss (not pc_rel).
               For other segs, address is a long word PC rel jump. */
                    case TAHOE_WIDTH_CONDITIONAL_JUMP:
                      /* b<cond> */
                      /* To reverse the condition in a TAHOE branch,
               complement bit 4 */
                      *opcodeP ^= 0x10;
                      p = frag_more (7);
                      *p++ = 6;
                      *p++ = TAHOE_JMP;
                      *p++ = (operandP->top_mode ==
                              TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
                              TAHOE_PC_REL_LONG);
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
                      /*
             * Now (eg) BLEQ    1f
             *          JMP     foo
             *  1:
             */
                      break;
                    case TAHOE_WIDTH_ALWAYS_JUMP:
                      /* br, just turn it into a jump */
                      *opcodeP = TAHOE_JMP;
                      p = frag_more (5);
                      *p++ = (operandP->top_mode ==
                              TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
                              TAHOE_PC_REL_LONG);
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
                      /* Now (eg) JMP foo */
                      break;
                    case TAHOE_WIDTH_BIG_REV_JUMP:
                      p = frag_more (8);
                      *opcodeP ^= 0x10;
                      *p++ = 0;
                      *p++ = 6;
                      *p++ = TAHOE_JMP;
                      *p++ = (operandP->top_mode ==
                              TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
                              TAHOE_PC_REL_LONG);
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
                      /*
             * Now (eg) ACBx    1f
             *          JMP     foo
             *  1:
             */
                      break;
                    case TAHOE_WIDTH_BIG_NON_REV_JUMP:
                      p = frag_more (10);
                      *p++ = 0;
                      *p++ = 2;
                      *p++ = TAHOE_BRB;
                      *p++ = 6;
                      *p++ = TAHOE_JMP;
                      *p++ = (operandP->top_mode ==
                              TAHOE_ABSOLUTE_ADDR ? TAHOE_ABSOLUTE_ADDR :
                              TAHOE_PC_REL_LONG);
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                       (to_seg != SEG_ABSOLUTE) ? FX_PCREL32 : FX_32, NULL);
                      /*
             * Now (eg) xOBxxx  1f
             *          BRB     2f
             *  1:      JMP     @#foo
             *  2:
             */
                      break;
                    case 'b':
                    case 'w':
                      as_warn ("Real branch displacements must be expressions.");
                      break;
                    default:
                      as_fatal ("Complier error: I got an unknown synthetic branch :%c",
                                operandP->top_width);
                      break;
                    }
                }
            }
          else
            {
              /* It ain't a branch operand. */
              switch (operandP->top_mode)
                {
                  /* Auto-foo access, only works for one reg (SP)
             so the only thing needed is the mode. */
                case TAHOE_AUTO_DEC:
                case TAHOE_AUTO_INC:
                case TAHOE_AUTO_INC_DEFERRED:
                  FRAG_APPEND_1_CHAR (operandP->top_mode);
                  break;

                  /* Numbered Register only access. Only thing needed is the
             mode + Register number */
                case TAHOE_DIRECT_REG:
                case TAHOE_REG_DEFERRED:
                  FRAG_APPEND_1_CHAR (operandP->top_mode + operandP->top_reg);
                  break;

                  /* An absolute address. It's size is always 5 bytes.
             (mode_type + 4 byte address). */
                case TAHOE_ABSOLUTE_ADDR:
                  know ((this_add_symbol == NULL));
                  p = frag_more (5);
                  *p = TAHOE_ABSOLUTE_ADDR;
                  md_number_to_chars (p + 1, this_add_number, 4);
                  break;

                  /* Immediate data. If the size isn't known, then it's an address
             + and offset, which is 4 bytes big. */
                case TAHOE_IMMEDIATE:
                  if (this_add_symbol != NULL)
                    {
                      p = frag_more (5);
                      *p++ = TAHOE_IMMEDIATE_LONGWORD;
                      fix_new (frag_now, p - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                               FX_32, NULL);
                    }
                  else
                    {
                      /* It's a integer, and I know it's size. */
                      if ((unsigned) this_add_number < 0x40)
                        {
                          /* Will it fit in a literal? */
                          FRAG_APPEND_1_CHAR ((byte) this_add_number);
                        }
                      else
                        {
                          p = frag_more (dispsize + 1);
                          switch (dispsize)
                            {
                            case 1:
                              *p++ = TAHOE_IMMEDIATE_BYTE;
                              *p = (byte) this_add_number;
                              break;
                            case 2:
                              *p++ = TAHOE_IMMEDIATE_WORD;
                              md_number_to_chars (p, this_add_number, 2);
                              break;
                            case 4:
                              *p++ = TAHOE_IMMEDIATE_LONGWORD;
                              md_number_to_chars (p, this_add_number, 4);
                              break;
                            }
                        }
                    }
                  break;

                  /* Distance from the PC. If the size isn't known, we have to relax
             into it. The difference between this and disp(sp) is that
             this offset is pc_rel, and disp(sp) isn't.
             Note the drop through code. */

                case TAHOE_DISPLACED_RELATIVE:
                case TAHOE_DISP_REL_DEFERRED:
                  operandP->top_reg = PC_REG;
                  pc_rel = 1;

                  /* Register, plus a displacement mode. Save the register number,
             and weather its deffered or not, and relax the size if it isn't
             known. */
                case TAHOE_REG_DISP:
                case TAHOE_REG_DISP_DEFERRED:
                  if (operandP->top_mode == TAHOE_DISP_REL_DEFERRED ||
                      operandP->top_mode == TAHOE_REG_DISP_DEFERRED)
                    operandP->top_reg += 0x10;  /* deffered mode is always 0x10 higher
                                          than it's non-deffered sibling. */

                  /* Is this a value out of this segment?
             The first part of this conditional is a cludge to make gas
             produce the same output as 'as' when there is a lable, in
             the current segment, displaceing a register. It's strange,
             and no one in their right mind would do it, but it's easy
             to cludge. */
                  if ((dispsize == 0 && !pc_rel) ||
                      (to_seg != now_seg && !is_undefined && to_seg != SEG_ABSOLUTE))
                    dispsize = 4;

                  if (dispsize == 0)
                    {
                      /*
             * We have a SEG_UNKNOWN symbol, or the size isn't cast.
             * It might turn out to be in the same segment as
             * the instruction, permitting relaxation.
             */
                      p = frag_var (rs_machine_dependent, 5, 2,
                                    ENCODE_RELAX (STATE_PC_RELATIVE,
                                    is_undefined ? STATE_UNDF : STATE_BYTE),
                                    this_add_symbol, this_add_number, 0);
                      *p = operandP->top_reg;
                    }
                  else
                    {
                      /* Either this is an abs, or a cast. */
                      p = frag_more (dispsize + 1);
                      switch (dispsize)
                        {
                        case 1:
                          *p = TAHOE_PC_OR_BYTE + operandP->top_reg;
                          break;
                        case 2:
                          *p = TAHOE_PC_OR_WORD + operandP->top_reg;
                          break;
                        case 4:
                          *p = TAHOE_PC_OR_LONG + operandP->top_reg;
                          break;
                        };
                      fix_new (frag_now, p + 1 - frag_now->fr_literal,
                               this_add_symbol, this_add_number,
                               size_to_fx (dispsize, pc_rel), NULL);
                    }
                  break;
                default:
                  as_fatal ("Barf, bad mode %x\n", operandP->top_mode);
                }
            }
        }                       /* for(operandP) */
    }                           /* if(!need_pass_2 && !goofed) */
}                               /* tahoe_assemble() */


/* We have no need to default values of symbols. */

/* ARGSUSED */
symbolS *
md_undefined_symbol (name)
     char *name;
{
  return 0;
}                               /* md_undefined_symbol() */

/* Parse an operand that is machine-specific.
   We just return without modifying the expression if we have nothing
   to do. */

/* ARGSUSED */
void 
md_operand (expressionP)
     expressionS *expressionP;
{
}                               /* md_operand() */

/* Round up a section size to the appropriate boundary. */
valueT
md_section_align (segment, size)
     segT segment;
     valueT size;
{
  return ((size + 7) & ~7);     /* Round all sects to multiple of 8 */
}                               /* md_section_align() */

/* Exactly what point is a PC-relative offset relative TO?
   On the sparc, they're relative to the address of the offset, plus
   its size.  This gets us to the following instruction.
   (??? Is this right?  FIXME-SOON) */
long 
md_pcrel_from (fixP)
     fixS *fixP;
{
  return (((fixP->fx_type == FX_8
            || fixP->fx_type == FX_PCREL8)
           ? 1
           : ((fixP->fx_type == FX_16
               || fixP->fx_type == FX_PCREL16)
              ? 2
              : ((fixP->fx_type == FX_32
                  || fixP->fx_type == FX_PCREL32)
                 ? 4
                 : 0))) + fixP->fx_where + fixP->fx_frag->fr_address);
}                               /* md_pcrel_from() */

int 
tc_is_pcrel (fixP)
     fixS *fixP;
{
  /* should never be called */
  know (0);
  return (0);
}                               /* tc_is_pcrel() */

/* end of tc-tahoe.c */