Initial import from FreeBSD RELENG_4:

[dragonfly.git] / gnu / usr.bin / as / 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         */

  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. */
     long int value;            /* The value of the bits. */
     int nbytes;                /* Number of bytes in the output. */
{
  int n = nbytes;
  long int 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
    md_apply_fix(fixP, val)
fixS *fixP;
long val;
{
        char *place = fixP->fx_where + fixP->fx_frag->fr_literal;
        md_number_to_chars(place, val, fixP->fx_size);
        return;
} /* md_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;
{
        /*
         * In: length of relocation (or of address) in chars: 1, 2 or 4.
         * Out: GNU LD relocation length code: 0, 1, or 2.
         */

        static unsigned char nbytes_r_length[] = { 42, 0, 1, 42, 2 };
        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] = (((fixP->fx_pcrel << 7) & 0x80)
                    | ((nbytes_r_length[fixP->fx_size] << 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;
     long from_addr, to_addr;
     fragS *frag;
     symbolS *to_symbol;
{
  long 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;
     long from_addr, to_addr;
     fragS *frag;
     symbolS *to_symbol;
{
  long 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, 4, fragP->fr_symbol, 0,
               fragP->fr_offset, 1, NO_RELOC);
      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, 4, fragP->fr_symbol, 0,
               fragP->fr_offset, 1, NO_RELOC);
      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, 4, fragP->fr_symbol, 0,
               fragP->fr_offset, 1, NO_RELOC);
      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, 4, fragP->fr_symbol, 0,
               fragP->fr_offset, 1, NO_RELOC);
      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, 4, fragP->fr_symbol, 0,
               fragP->fr_offset, 1, NO_RELOC);
      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);
    switch (expression (expP)){
      /* If expression == SEG_PASS1, expression() will have set
         need_pass_2 = 1. */
    case SEG_ABSENT:
      /* No expression. For BSD4.2 compatibility, missing expression is
         absolute 0 */
      expP->X_seg = SEG_ABSOLUTE;
      expP->X_add_number = 0;
      really_none = 1;
    case SEG_ABSOLUTE:
      /* for SEG_ABSOLUTE, we shouldnt need to set X_subtract_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_subtract_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 SEG_TEXT:
    case SEG_DATA:
    case SEG_BSS:
    case SEG_UNKNOWN:
      break;

    case SEG_DIFFERENCE:
      /*
       * Major bug. We can't handle the case of a
       * SEG_DIFFERENCE expression in a synthetic opcode
       * variable-length instruction.
       * We don't have a frag type that is smart enough to
       * relax a SEG_DIFFERENCE, and so we just force all
       * SEG_DIFFERENCEs 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. SEG_DIFFERENCE was invented for the
       * .words after a CASE opcode, and was never intended for
       * instruction operands.
       */
      need_pass_2 = 1;
    case SEG_PASS1:
      op_bad = "Can't relocate expression error.";
      break;

    case SEG_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;

    default:
      as_fatal("Complier Bug: I got segment %d in tip_op.",expP->X_seg);
      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 = expP->X_seg;
      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, dispsize,
                     this_add_symbol, 0, this_add_number, 1, NO_RELOC);
          } 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, 4,
                     this_add_symbol, 0, this_add_number,
                     (to_seg != SEG_ABSOLUTE), NO_RELOC);
            /*
             * 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, 4,
                     this_add_symbol, 0, this_add_number,
                     (to_seg != SEG_ABSOLUTE), NO_RELOC);
            /* 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, 4,
                     this_add_symbol, 0, this_add_number,
                     (to_seg != SEG_ABSOLUTE), NO_RELOC);
            /*
             * 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, 4,
                     this_add_symbol, 0, this_add_number,
                     (to_seg != SEG_ABSOLUTE), NO_RELOC);
            /*
             * 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,
                     4, this_add_symbol,0,this_add_number,
                     0, NO_RELOC);
          }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,
                     dispsize, this_add_symbol,0,this_add_number,
                     pc_rel, NO_RELOC);
          }
          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. */
long md_section_align(segment, size)
segT segment;
long 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_size + fixP->fx_where + fixP->fx_frag->fr_address);
} /* md_pcrel_from() */

/* end of tc-tahoe.c */