assemble.c

/* assemble.c   code generation for the Netwide Assembler
 *
 * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
 * Julian Hall. All rights reserved. The software is
 * redistributable under the licence given in the file "Licence"
 * distributed in the NASM archive.
 *
 * the actual codes (C syntax, i.e. octal):
 * \0            - terminates the code. (Unless it's a literal of course.)
 * \1, \2, \3    - that many literal bytes follow in the code stream
 * \4, \6        - the POP/PUSH (respectively) codes for CS, DS, ES, SS
 *                 (POP is never used for CS) depending on operand 0
 * \5, \7        - the second byte of POP/PUSH codes for FS, GS, depending
 *                 on operand 0
 * \10, \11, \12 - a literal byte follows in the code stream, to be added
 *                 to the register value of operand 0, 1 or 2
 * \17           - encodes the literal byte 0. (Some compilers don't take
 *                 kindly to a zero byte in the _middle_ of a compile time
 *                 string constant, so I had to put this hack in.)
 * \14, \15, \16 - a signed byte immediate operand, from operand 0, 1 or 2
 * \20, \21, \22 - a byte immediate operand, from operand 0, 1 or 2
 * \24, \25, \26 - an unsigned byte immediate operand, from operand 0, 1 or 2
 * \30, \31, \32 - a word immediate operand, from operand 0, 1 or 2
 * \34, \35, \36 - select between \3[012] and \4[012] depending on 16/32 bit
 *                 assembly mode or the operand-size override on the operand
 * \37           - a word constant, from the _segment_ part of operand 0
 * \40, \41, \42 - a long immediate operand, from operand 0, 1 or 2
 * \44, \45, \46 - select between \3[012] and \4[012] depending on 16/32 bit
 *                 assembly mode or the address-size override on the operand
 * \50, \51, \52 - a byte relative operand, from operand 0, 1 or 2
 * \60, \61, \62 - a word relative operand, from operand 0, 1 or 2
 * \64, \65, \66 - select between \6[012] and \7[012] depending on 16/32 bit
 *                 assembly mode or the operand-size override on the operand
 * \70, \71, \72 - a long relative operand, from operand 0, 1 or 2
 * \1ab          - a ModRM, calculated on EA in operand a, with the spare
 *                 field the register value of operand b.
 * \130,\131,\132 - an immediate word or signed byte for operand 0, 1, or 2
 * \133,\134,\135 - or 2 (s-field) into next opcode byte if operand 0, 1, or 2
 *		    is a signed byte rather than a word.
 * \140,\141,\142 - an immediate dword or signed byte for operand 0, 1, or 2
 * \143,\144,\145 - or 2 (s-field) into next opcode byte if operand 0, 1, or 2
 *		    is a signed byte rather than a dword.
 * \2ab          - a ModRM, calculated on EA in operand a, with the spare
 *                 field equal to digit b.
 * \30x          - might be an 0x67 byte, depending on the address size of
 *                 the memory reference in operand x.
 * \310          - indicates fixed 16-bit address size, i.e. optional 0x67.
 * \311          - indicates fixed 32-bit address size, i.e. optional 0x67.
 * \312		 - (disassembler only) marker on LOOP, LOOPxx instructions.
 * \320          - indicates fixed 16-bit operand size, i.e. optional 0x66.
 * \321          - indicates fixed 32-bit operand size, i.e. optional 0x66.
 * \322          - indicates that this instruction is only valid when the
 *                 operand size is the default (instruction to disassembler,
 *                 generates no code in the assembler)
 * \330          - a literal byte follows in the code stream, to be added
 *                 to the condition code value of the instruction.
 * \331		 - instruction not valid with REP prefix.  Hint for
 *                 disassembler only; for SSE instructions.
 * \332		 - disassemble a rep (0xF3 byte) prefix as repe not rep.
 * \333		 - REP prefix (0xF3 byte); for SSE instructions.  Not encoded
 *		   as a literal byte in order to aid the disassembler.
 * \340          - reserve <operand 0> bytes of uninitialised storage.
 *                 Operand 0 had better be a segmentless constant.
 * \370,\371,\372 - match only if operand 0 meets byte jump criteria.
 *		   370 is used for Jcc, 371 is used for JMP.
 * \373		 - assemble 0x03 if bits==16, 0x05 if bits==32;
 *		   used for conditional jump over longer jump
 */

#include <stdio.h>
#include <string.h>

#include "nasm.h"
#include "nasmlib.h"
#include "assemble.h"
#include "insns.h"
#include "preproc.h"

extern struct itemplate *nasm_instructions[];

typedef struct {
    int sib_present;            /* is a SIB byte necessary? */
    int bytes;                  /* # of bytes of offset needed */
    int size;                   /* lazy - this is sib+bytes+1 */
    unsigned char modrm, sib;   /* the bytes themselves */
} ea;

static unsigned long cpu;       /* cpu level received from nasm.c */
static efunc errfunc;
static struct ofmt *outfmt;
static ListGen *list;

static long calcsize(long, long, int, insn *, const char *);
static void gencode(long, long, int, insn *, const char *, long);
static int regval(operand * o);
static int matches(struct itemplate *, insn *);
static ea *process_ea(operand *, ea *, int, int, int);
static int chsize(operand *, int);

/*
 * This routine wrappers the real output format's output routine,
 * in order to pass a copy of the data off to the listing file
 * generator at the same time.
 */
static void out(long offset, long segto, const void *data,
                unsigned long type, long segment, long wrt)
{
    static long lineno = 0;     /* static!!! */
    static char *lnfname = NULL;

    if ((type & OUT_TYPMASK) == OUT_ADDRESS) {
        if (segment != NO_SEG || wrt != NO_SEG) {
            /*
             * This address is relocated. We must write it as
             * OUT_ADDRESS, so there's no work to be done here.
             */
            list->output(offset, data, type);
        } else {
            unsigned char p[4], *q = p;
            /*
             * This is a non-relocated address, and we're going to
             * convert it into RAWDATA format.
             */
            if ((type & OUT_SIZMASK) == 4) {
                WRITELONG(q, *(long *)data);
                list->output(offset, p, OUT_RAWDATA + 4);
            } else {
                WRITESHORT(q, *(long *)data);
                list->output(offset, p, OUT_RAWDATA + 2);
            }
        }
    } else if ((type & OUT_TYPMASK) == OUT_RAWDATA) {
        list->output(offset, data, type);
    } else if ((type & OUT_TYPMASK) == OUT_RESERVE) {
        list->output(offset, NULL, type);
    } else if ((type & OUT_TYPMASK) == OUT_REL2ADR ||
               (type & OUT_TYPMASK) == OUT_REL4ADR) {
        list->output(offset, data, type);
    }

    /*
     * this call to src_get determines when we call the
     * debug-format-specific "linenum" function
     * it updates lineno and lnfname to the current values
     * returning 0 if "same as last time", -2 if lnfname
     * changed, and the amount by which lineno changed,
     * if it did. thus, these variables must be static
     */

    if (src_get(&lineno, &lnfname)) {
        outfmt->current_dfmt->linenum(lnfname, lineno, segto);
    }

    outfmt->output(segto, data, type, segment, wrt);
}

static int jmp_match(long segment, long offset, int bits,
                     insn * ins, const char *code)
{
    long isize;
    unsigned char c = code[0];

    if (c != 0370 && c != 0371)
        return 0;
    if (ins->oprs[0].opflags & OPFLAG_FORWARD) {
        if ((optimizing < 0 || (ins->oprs[0].type & STRICT))
            && c == 0370)
            return 1;
        else
            return (pass0 == 0);        /* match a forward reference */
    }
    isize = calcsize(segment, offset, bits, ins, code);
    if (ins->oprs[0].segment != segment)
        return 0;
    isize = ins->oprs[0].offset - offset - isize;       /* isize is now the delta */
    if (isize >= -128L && isize <= 127L)
        return 1;               /* it is byte size */

    return 0;
}

long assemble(long segment, long offset, int bits, unsigned long cp,
              insn * instruction, struct ofmt *output, efunc error,
              ListGen * listgen)
{
    struct itemplate *temp;
    int j;
    int size_prob;
    long insn_end;
    long itimes;
    long start = offset;
    long wsize = 0;             /* size for DB etc. */

    errfunc = error;            /* to pass to other functions */
    cpu = cp;
    outfmt = output;            /* likewise */
    list = listgen;             /* and again */

    switch (instruction->opcode) {
    case -1:
        return 0;
    case I_DB:
        wsize = 1;
        break;
    case I_DW:
        wsize = 2;
        break;
    case I_DD:
        wsize = 4;
        break;
    case I_DQ:
        wsize = 8;
        break;
    case I_DT:
        wsize = 10;
        break;
    }

    if (wsize) {
        extop *e;
        long t = instruction->times;
        if (t < 0)
            errfunc(ERR_PANIC,
                    "instruction->times < 0 (%ld) in assemble()", t);

        while (t--) {           /* repeat TIMES times */
            for (e = instruction->eops; e; e = e->next) {
                if (e->type == EOT_DB_NUMBER) {
                    if (wsize == 1) {
                        if (e->segment != NO_SEG)
                            errfunc(ERR_NONFATAL,
                                    "one-byte relocation attempted");
                        else {
                            unsigned char out_byte = e->offset;
                            out(offset, segment, &out_byte,
                                OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                        }
                    } else if (wsize > 5) {
                        errfunc(ERR_NONFATAL, "integer supplied to a D%c"
                                " instruction", wsize == 8 ? 'Q' : 'T');
                    } else
                        out(offset, segment, &e->offset,
                            OUT_ADDRESS + wsize, e->segment, e->wrt);
                    offset += wsize;
                } else if (e->type == EOT_DB_STRING) {
                    int align;

                    out(offset, segment, e->stringval,
                        OUT_RAWDATA + e->stringlen, NO_SEG, NO_SEG);
                    align = e->stringlen % wsize;

                    if (align) {
                        align = wsize - align;
                        out(offset, segment, "\0\0\0\0\0\0\0\0",
                            OUT_RAWDATA + align, NO_SEG, NO_SEG);
                    }
                    offset += e->stringlen + align;
                }
            }
            if (t > 0 && t == instruction->times - 1) {
                /*
                 * Dummy call to list->output to give the offset to the
                 * listing module.
                 */
                list->output(offset, NULL, OUT_RAWDATA);
                list->uplevel(LIST_TIMES);
            }
        }
        if (instruction->times > 1)
            list->downlevel(LIST_TIMES);
        return offset - start;
    }

    if (instruction->opcode == I_INCBIN) {
        static char fname[FILENAME_MAX];
        FILE *fp;
        long len;
        char *prefix = "", *combine;
        char **pPrevPath = NULL;

        len = FILENAME_MAX - 1;
        if (len > instruction->eops->stringlen)
            len = instruction->eops->stringlen;
        strncpy(fname, instruction->eops->stringval, len);
        fname[len] = '\0';

        while (1) {             /* added by alexfru: 'incbin' uses include paths */
            combine = nasm_malloc(strlen(prefix) + len + 1);
            strcpy(combine, prefix);
            strcat(combine, fname);

            if ((fp = fopen(combine, "rb")) != NULL) {
                nasm_free(combine);
                break;
            }

            nasm_free(combine);
            pPrevPath = pp_get_include_path_ptr(pPrevPath);
            if (pPrevPath == NULL)
                break;
            prefix = *pPrevPath;
        }

        if (fp == NULL)
            error(ERR_NONFATAL, "`incbin': unable to open file `%s'",
                  fname);
        else if (fseek(fp, 0L, SEEK_END) < 0)
            error(ERR_NONFATAL, "`incbin': unable to seek on file `%s'",
                  fname);
        else {
            static char buf[2048];
            long t = instruction->times;
            long base = 0;

            len = ftell(fp);
            if (instruction->eops->next) {
                base = instruction->eops->next->offset;
                len -= base;
                if (instruction->eops->next->next &&
                    len > instruction->eops->next->next->offset)
                    len = instruction->eops->next->next->offset;
            }
            /*
             * Dummy call to list->output to give the offset to the
             * listing module.
             */
            list->output(offset, NULL, OUT_RAWDATA);
            list->uplevel(LIST_INCBIN);
            while (t--) {
                long l;

                fseek(fp, base, SEEK_SET);
                l = len;
                while (l > 0) {
                    long m =
                        fread(buf, 1, (l > sizeof(buf) ? sizeof(buf) : l),
                              fp);
                    if (!m) {
                        /*
                         * This shouldn't happen unless the file
                         * actually changes while we are reading
                         * it.
                         */
                        error(ERR_NONFATAL,
                              "`incbin': unexpected EOF while"
                              " reading file `%s'", fname);
                        t = 0;  /* Try to exit cleanly */
                        break;
                    }
                    out(offset, segment, buf, OUT_RAWDATA + m,
                        NO_SEG, NO_SEG);
                    l -= m;
                }
            }
            list->downlevel(LIST_INCBIN);
            if (instruction->times > 1) {
                /*
                 * Dummy call to list->output to give the offset to the
                 * listing module.
                 */
                list->output(offset, NULL, OUT_RAWDATA);
                list->uplevel(LIST_TIMES);
                list->downlevel(LIST_TIMES);
            }
            fclose(fp);
            return instruction->times * len;
        }
        return 0;               /* if we're here, there's an error */
    }

    size_prob = FALSE;
    temp = nasm_instructions[instruction->opcode];
    while (temp->opcode != -1) {
        int m = matches(temp, instruction);
        if (m == 99)
            m += jmp_match(segment, offset, bits, instruction, temp->code);

        if (m == 100) {         /* matches! */
            const char *codes = temp->code;
            long insn_size = calcsize(segment, offset, bits,
                                      instruction, codes);
            itimes = instruction->times;
            if (insn_size < 0)  /* shouldn't be, on pass two */
                error(ERR_PANIC, "errors made it through from pass one");
            else
                while (itimes--) {
                    for (j = 0; j < instruction->nprefix; j++) {
                        unsigned char c = 0;
                        switch (instruction->prefixes[j]) {
                        case P_LOCK:
                            c = 0xF0;
                            break;
                        case P_REPNE:
                        case P_REPNZ:
                            c = 0xF2;
                            break;
                        case P_REPE:
                        case P_REPZ:
                        case P_REP:
                            c = 0xF3;
                            break;
                        case R_CS:
                            c = 0x2E;
                            break;
                        case R_DS:
                            c = 0x3E;
                            break;
                        case R_ES:
                            c = 0x26;
                            break;
                        case R_FS:
                            c = 0x64;
                            break;
                        case R_GS:
                            c = 0x65;
                            break;
                        case R_SS:
                            c = 0x36;
                            break;
                        case R_SEGR6:
                        case R_SEGR7:
                            error(ERR_NONFATAL,
                                  "segr6 and segr7 cannot be used as prefixes");
                            break;
                        case P_A16:
                            if (bits != 16)
                                c = 0x67;
                            break;
                        case P_A32:
                            if (bits != 32)
                                c = 0x67;
                            break;
                        case P_O16:
                            if (bits != 16)
                                c = 0x66;
                            break;
                        case P_O32:
                            if (bits != 32)
                                c = 0x66;
                            break;
                        default:
                            error(ERR_PANIC, "invalid instruction prefix");
                        }
                        if (c != 0) {
                            out(offset, segment, &c, OUT_RAWDATA + 1,
                                NO_SEG, NO_SEG);
                            offset++;
                        }
                    }
                    insn_end = offset + insn_size;
                    gencode(segment, offset, bits, instruction, codes,
                            insn_end);
                    offset += insn_size;
                    if (itimes > 0 && itimes == instruction->times - 1) {
                        /*
                         * Dummy call to list->output to give the offset to the
                         * listing module.
                         */
                        list->output(offset, NULL, OUT_RAWDATA);
                        list->uplevel(LIST_TIMES);
                    }
                }
            if (instruction->times > 1)
                list->downlevel(LIST_TIMES);
            return offset - start;
        } else if (m > 0 && m > size_prob) {
            size_prob = m;
        }
        temp++;
    }

    if (temp->opcode == -1) {   /* didn't match any instruction */
        if (size_prob == 1)     /* would have matched, but for size */
            error(ERR_NONFATAL, "operation size not specified");
        else if (size_prob == 2)
            error(ERR_NONFATAL, "mismatch in operand sizes");
        else if (size_prob == 3)
            error(ERR_NONFATAL, "no instruction for this cpu level");
        else
            error(ERR_NONFATAL,
                  "invalid combination of opcode and operands");
    }
    return 0;
}

long insn_size(long segment, long offset, int bits, unsigned long cp,
               insn * instruction, efunc error)
{
    struct itemplate *temp;

    errfunc = error;            /* to pass to other functions */
    cpu = cp;

    if (instruction->opcode == -1)
        return 0;

    if (instruction->opcode == I_DB ||
        instruction->opcode == I_DW ||
        instruction->opcode == I_DD ||
        instruction->opcode == I_DQ || instruction->opcode == I_DT) {
        extop *e;
        long isize, osize, wsize = 0;   /* placate gcc */

        isize = 0;
        switch (instruction->opcode) {
        case I_DB:
            wsize = 1;
            break;
        case I_DW:
            wsize = 2;
            break;
        case I_DD:
            wsize = 4;
            break;
        case I_DQ:
            wsize = 8;
            break;
        case I_DT:
            wsize = 10;
            break;
        }

        for (e = instruction->eops; e; e = e->next) {
            long align;

            osize = 0;
            if (e->type == EOT_DB_NUMBER)
                osize = 1;
            else if (e->type == EOT_DB_STRING)
                osize = e->stringlen;

            align = (-osize) % wsize;
            if (align < 0)
                align += wsize;
            isize += osize + align;
        }
        return isize * instruction->times;
    }

    if (instruction->opcode == I_INCBIN) {
        char fname[FILENAME_MAX];
        FILE *fp;
        long len;
        char *prefix = "", *combine;
        char **pPrevPath = NULL;

        len = FILENAME_MAX - 1;
        if (len > instruction->eops->stringlen)
            len = instruction->eops->stringlen;
        strncpy(fname, instruction->eops->stringval, len);
        fname[len] = '\0';

        while (1) {             /* added by alexfru: 'incbin' uses include paths */
            combine = nasm_malloc(strlen(prefix) + len + 1);
            strcpy(combine, prefix);
            strcat(combine, fname);

            if ((fp = fopen(combine, "rb")) != NULL) {
                nasm_free(combine);
                break;
            }

            nasm_free(combine);
            pPrevPath = pp_get_include_path_ptr(pPrevPath);
            if (pPrevPath == NULL)
                break;
            prefix = *pPrevPath;
        }

        if (fp == NULL)
            error(ERR_NONFATAL, "`incbin': unable to open file `%s'",
                  fname);
        else if (fseek(fp, 0L, SEEK_END) < 0)
            error(ERR_NONFATAL, "`incbin': unable to seek on file `%s'",
                  fname);
        else {
            len = ftell(fp);
            fclose(fp);
            if (instruction->eops->next) {
                len -= instruction->eops->next->offset;
                if (instruction->eops->next->next &&
                    len > instruction->eops->next->next->offset) {
                    len = instruction->eops->next->next->offset;
                }
            }
            return instruction->times * len;
        }
        return 0;               /* if we're here, there's an error */
    }

    temp = nasm_instructions[instruction->opcode];
    while (temp->opcode != -1) {
        int m = matches(temp, instruction);
        if (m == 99)
            m += jmp_match(segment, offset, bits, instruction, temp->code);

        if (m == 100) {
            /* we've matched an instruction. */
            long isize;
            const char *codes = temp->code;
            int j;

            isize = calcsize(segment, offset, bits, instruction, codes);
            if (isize < 0)
                return -1;
            for (j = 0; j < instruction->nprefix; j++) {
                if ((instruction->prefixes[j] != P_A16 &&
                     instruction->prefixes[j] != P_O16 && bits == 16) ||
                    (instruction->prefixes[j] != P_A32 &&
                     instruction->prefixes[j] != P_O32 && bits == 32)) {
                    isize++;
                }
            }
            return isize * instruction->times;
        }
        temp++;
    }
    return -1;                  /* didn't match any instruction */
}

/* check that  opn[op]  is a signed byte of size 16 or 32,
					and return the signed value*/
static int is_sbyte(insn * ins, int op, int size)
{
    signed long v;
    int ret;

    ret = !(ins->forw_ref && ins->oprs[op].opflags) &&  /* dead in the water on forward reference or External */
        optimizing >= 0 &&
        !(ins->oprs[op].type & STRICT) &&
        ins->oprs[op].wrt == NO_SEG && ins->oprs[op].segment == NO_SEG;

    v = ins->oprs[op].offset;
    if (size == 16)
        v = (signed short)v;    /* sign extend if 16 bits */

    return ret && v >= -128L && v <= 127L;
}

static long calcsize(long segment, long offset, int bits,
                     insn * ins, const char *codes)
{
    long length = 0;
    unsigned char c;

    (void)segment;              /* Don't warn that this parameter is unused */
    (void)offset;               /* Don't warn that this parameter is unused */

    while (*codes)
        switch (c = *codes++) {
        case 01:
        case 02:
        case 03:
            codes += c, length += c;
            break;
        case 04:
        case 05:
        case 06:
        case 07:
            length++;
            break;
        case 010:
        case 011:
        case 012:
            codes++, length++;
            break;
        case 017:
            length++;
            break;
        case 014:
        case 015:
        case 016:
            length++;
            break;
        case 020:
        case 021:
        case 022:
            length++;
            break;
        case 024:
        case 025:
        case 026:
            length++;
            break;
        case 030:
        case 031:
        case 032:
            length += 2;
            break;
        case 034:
        case 035:
        case 036:
            if (ins->oprs[c - 034].type & (BITS16 | BITS32))
                length += (ins->oprs[c - 034].type & BITS16) ? 2 : 4;
            else
                length += (bits == 16) ? 2 : 4;
            break;
        case 037:
            length += 2;
            break;
        case 040:
        case 041:
        case 042:
            length += 4;
            break;
        case 044:
        case 045:
        case 046:
            length += ((ins->oprs[c - 044].addr_size ?
                        ins->oprs[c - 044].addr_size : bits) ==
                       16 ? 2 : 4);
            break;
        case 050:
        case 051:
        case 052:
            length++;
            break;
        case 060:
        case 061:
        case 062:
            length += 2;
            break;
        case 064:
        case 065:
        case 066:
            if (ins->oprs[c - 064].type & (BITS16 | BITS32))
                length += (ins->oprs[c - 064].type & BITS16) ? 2 : 4;
            else
                length += (bits == 16) ? 2 : 4;
            break;
        case 070:
        case 071:
        case 072:
            length += 4;
            break;
        case 0130:
        case 0131:
        case 0132:
            length += is_sbyte(ins, c - 0130, 16) ? 1 : 2;
            break;
        case 0133:
        case 0134:
        case 0135:
            codes += 2;
            length++;
            break;
        case 0140:
        case 0141:
        case 0142:
            length += is_sbyte(ins, c - 0140, 32) ? 1 : 4;
            break;
        case 0143:
        case 0144:
        case 0145:
            codes += 2;
            length++;
            break;
        case 0300:
        case 0301:
        case 0302:
            length += chsize(&ins->oprs[c - 0300], bits);
            break;
        case 0310:
            length += (bits == 32);
            break;
        case 0311:
            length += (bits == 16);
            break;
        case 0312:
            break;
        case 0320:
            length += (bits == 32);
            break;
        case 0321:
            length += (bits == 16);
            break;
        case 0322:
            break;
        case 0330:
            codes++, length++;
            break;
        case 0331:
        case 0332:
            break;
        case 0333:
            length++;
            break;
        case 0340:
        case 0341:
        case 0342:
            if (ins->oprs[0].segment != NO_SEG)
                errfunc(ERR_NONFATAL, "attempt to reserve non-constant"
                        " quantity of BSS space");
            else
                length += ins->oprs[0].offset << (c - 0340);
            break;
        case 0370:
        case 0371:
        case 0372:
            break;
        case 0373:
            length++;
            break;
        default:               /* can't do it by 'case' statements */
            if (c >= 0100 && c <= 0277) {       /* it's an EA */
                ea ea_data;
                if (!process_ea
                    (&ins->oprs[(c >> 3) & 7], &ea_data, bits, 0,
                     ins->forw_ref)) {
                    errfunc(ERR_NONFATAL, "invalid effective address");
                    return -1;
                } else
                    length += ea_data.size;
            } else
                errfunc(ERR_PANIC, "internal instruction table corrupt"
                        ": instruction code 0x%02X given", c);
        }
    return length;
}

static void gencode(long segment, long offset, int bits,
                    insn * ins, const char *codes, long insn_end)
{
    static char condval[] = {   /* conditional opcodes */
        0x7, 0x3, 0x2, 0x6, 0x2, 0x4, 0xF, 0xD, 0xC, 0xE, 0x6, 0x2,
        0x3, 0x7, 0x3, 0x5, 0xE, 0xC, 0xD, 0xF, 0x1, 0xB, 0x9, 0x5,
        0x0, 0xA, 0xA, 0xB, 0x8, 0x4
    };
    unsigned char c;
    unsigned char bytes[4];
    long data, size;

    while (*codes)
        switch (c = *codes++) {
        case 01:
        case 02:
        case 03:
            out(offset, segment, codes, OUT_RAWDATA + c, NO_SEG, NO_SEG);
            codes += c;
            offset += c;
            break;

        case 04:
        case 06:
            switch (ins->oprs[0].basereg) {
            case R_CS:
                bytes[0] = 0x0E + (c == 0x04 ? 1 : 0);
                break;
            case R_DS:
                bytes[0] = 0x1E + (c == 0x04 ? 1 : 0);
                break;
            case R_ES:
                bytes[0] = 0x06 + (c == 0x04 ? 1 : 0);
                break;
            case R_SS:
                bytes[0] = 0x16 + (c == 0x04 ? 1 : 0);
                break;
            default:
                errfunc(ERR_PANIC,
                        "bizarre 8086 segment register received");
            }
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset++;
            break;

        case 05:
        case 07:
            switch (ins->oprs[0].basereg) {
            case R_FS:
                bytes[0] = 0xA0 + (c == 0x05 ? 1 : 0);
                break;
            case R_GS:
                bytes[0] = 0xA8 + (c == 0x05 ? 1 : 0);
                break;
            default:
                errfunc(ERR_PANIC,
                        "bizarre 386 segment register received");
            }
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset++;
            break;

        case 010:
        case 011:
        case 012:
            bytes[0] = *codes++ + regval(&ins->oprs[c - 010]);
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 017:
            bytes[0] = 0;
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 014:
        case 015:
        case 016:
            if (ins->oprs[c - 014].offset < -128
                || ins->oprs[c - 014].offset > 127) {
                errfunc(ERR_WARNING, "signed byte value exceeds bounds");
            }

            if (ins->oprs[c - 014].segment != NO_SEG) {
                data = ins->oprs[c - 014].offset;
                out(offset, segment, &data, OUT_ADDRESS + 1,
                    ins->oprs[c - 014].segment, ins->oprs[c - 014].wrt);
            } else {
                bytes[0] = ins->oprs[c - 014].offset;
                out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

        case 020:
        case 021:
        case 022:
            if (ins->oprs[c - 020].offset < -256
                || ins->oprs[c - 020].offset > 255) {
                errfunc(ERR_WARNING, "byte value exceeds bounds");
            }
            if (ins->oprs[c - 020].segment != NO_SEG) {
                data = ins->oprs[c - 020].offset;
                out(offset, segment, &data, OUT_ADDRESS + 1,
                    ins->oprs[c - 020].segment, ins->oprs[c - 020].wrt);
            } else {
                bytes[0] = ins->oprs[c - 020].offset;
                out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

        case 024:
        case 025:
        case 026:
            if (ins->oprs[c - 024].offset < 0
                || ins->oprs[c - 024].offset > 255)
                errfunc(ERR_WARNING, "unsigned byte value exceeds bounds");
            if (ins->oprs[c - 024].segment != NO_SEG) {
                data = ins->oprs[c - 024].offset;
                out(offset, segment, &data, OUT_ADDRESS + 1,
                    ins->oprs[c - 024].segment, ins->oprs[c - 024].wrt);
            } else {
                bytes[0] = ins->oprs[c - 024].offset;
                out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

        case 030:
        case 031:
        case 032:
            if (ins->oprs[c - 030].segment == NO_SEG &&
                ins->oprs[c - 030].wrt == NO_SEG &&
                (ins->oprs[c - 030].offset < -65536L ||
                 ins->oprs[c - 030].offset > 65535L)) {
                errfunc(ERR_WARNING, "word value exceeds bounds");
            }
            data = ins->oprs[c - 030].offset;
            out(offset, segment, &data, OUT_ADDRESS + 2,
                ins->oprs[c - 030].segment, ins->oprs[c - 030].wrt);
            offset += 2;
            break;

        case 034:
        case 035:
        case 036:
            if (ins->oprs[c - 034].type & (BITS16 | BITS32))
                size = (ins->oprs[c - 034].type & BITS16) ? 2 : 4;
            else
                size = (bits == 16) ? 2 : 4;
            data = ins->oprs[c - 034].offset;
            if (size == 2 && (data < -65536L || data > 65535L))
                errfunc(ERR_WARNING, "word value exceeds bounds");
            out(offset, segment, &data, OUT_ADDRESS + size,
                ins->oprs[c - 034].segment, ins->oprs[c - 034].wrt);
            offset += size;
            break;

        case 037:
            if (ins->oprs[0].segment == NO_SEG)
                errfunc(ERR_NONFATAL, "value referenced by FAR is not"
                        " relocatable");
            data = 0L;
            out(offset, segment, &data, OUT_ADDRESS + 2,
                outfmt->segbase(1 + ins->oprs[0].segment),
                ins->oprs[0].wrt);
            offset += 2;
            break;

        case 040:
        case 041:
        case 042:
            data = ins->oprs[c - 040].offset;
            out(offset, segment, &data, OUT_ADDRESS + 4,
                ins->oprs[c - 040].segment, ins->oprs[c - 040].wrt);
            offset += 4;
            break;

        case 044:
        case 045:
        case 046:
            data = ins->oprs[c - 044].offset;
            size = ((ins->oprs[c - 044].addr_size ?
                     ins->oprs[c - 044].addr_size : bits) == 16 ? 2 : 4);
            if (size == 2 && (data < -65536L || data > 65535L))
                errfunc(ERR_WARNING, "word value exceeds bounds");
            out(offset, segment, &data, OUT_ADDRESS + size,
                ins->oprs[c - 044].segment, ins->oprs[c - 044].wrt);
            offset += size;
            break;

        case 050:
        case 051:
        case 052:
            if (ins->oprs[c - 050].segment != segment)
                errfunc(ERR_NONFATAL,
                        "short relative jump outside segment");
            data = ins->oprs[c - 050].offset - insn_end;
            if (data > 127 || data < -128)
                errfunc(ERR_NONFATAL, "short jump is out of range");
            bytes[0] = data;
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 060:
        case 061:
        case 062:
            if (ins->oprs[c - 060].segment != segment) {
                data = ins->oprs[c - 060].offset;
                out(offset, segment, &data,
                    OUT_REL2ADR + insn_end - offset,
                    ins->oprs[c - 060].segment, ins->oprs[c - 060].wrt);
            } else {
                data = ins->oprs[c - 060].offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS + 2, NO_SEG, NO_SEG);
            }
            offset += 2;
            break;

        case 064:
        case 065:
        case 066:
            if (ins->oprs[c - 064].type & (BITS16 | BITS32))
                size = (ins->oprs[c - 064].type & BITS16) ? 2 : 4;
            else
                size = (bits == 16) ? 2 : 4;
            if (ins->oprs[c - 064].segment != segment) {
                long reltype = (size == 2 ? OUT_REL2ADR : OUT_REL4ADR);
                data = ins->oprs[c - 064].offset;
                out(offset, segment, &data, reltype + insn_end - offset,
                    ins->oprs[c - 064].segment, ins->oprs[c - 064].wrt);
            } else {
                data = ins->oprs[c - 064].offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS + size, NO_SEG, NO_SEG);
            }
            offset += size;
            break;

        case 070:
        case 071:
        case 072:
            if (ins->oprs[c - 070].segment != segment) {
                data = ins->oprs[c - 070].offset;
                out(offset, segment, &data,
                    OUT_REL4ADR + insn_end - offset,
                    ins->oprs[c - 070].segment, ins->oprs[c - 070].wrt);
            } else {
                data = ins->oprs[c - 070].offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS + 4, NO_SEG, NO_SEG);
            }
            offset += 4;
            break;

        case 0130:
        case 0131:
        case 0132:
            data = ins->oprs[c - 0130].offset;
            if (is_sbyte(ins, c - 0130, 16)) {
                bytes[0] = data;
                out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG,
                    NO_SEG);
                offset++;
            } else {
                if (ins->oprs[c - 0130].segment == NO_SEG &&
                    ins->oprs[c - 0130].wrt == NO_SEG &&
                    (data < -65536L || data > 65535L)) {
                    errfunc(ERR_WARNING, "word value exceeds bounds");
                }
                out(offset, segment, &data, OUT_ADDRESS + 2,
                    ins->oprs[c - 0130].segment, ins->oprs[c - 0130].wrt);
                offset += 2;
            }
            break;

        case 0133:
        case 0134:
        case 0135:
            codes++;
            bytes[0] = *codes++;
            if (is_sbyte(ins, c - 0133, 16))
                bytes[0] |= 2;  /* s-bit */
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset++;
            break;

        case 0140:
        case 0141:
        case 0142:
            data = ins->oprs[c - 0140].offset;
            if (is_sbyte(ins, c - 0140, 32)) {
                bytes[0] = data;
                out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG,
                    NO_SEG);
                offset++;
            } else {
                out(offset, segment, &data, OUT_ADDRESS + 4,
                    ins->oprs[c - 0140].segment, ins->oprs[c - 0140].wrt);
                offset += 4;
            }
            break;

        case 0143:
        case 0144:
        case 0145:
            codes++;
            bytes[0] = *codes++;
            if (is_sbyte(ins, c - 0143, 32))
                bytes[0] |= 2;  /* s-bit */
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset++;
            break;

        case 0300:
        case 0301:
        case 0302:
            if (chsize(&ins->oprs[c - 0300], bits)) {
                *bytes = 0x67;
                out(offset, segment, bytes,
                    OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0310:
            if (bits == 32) {
                *bytes = 0x67;
                out(offset, segment, bytes,
                    OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0311:
            if (bits == 16) {
                *bytes = 0x67;
                out(offset, segment, bytes,
                    OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0312:
            break;

        case 0320:
            if (bits == 32) {
                *bytes = 0x66;
                out(offset, segment, bytes,
                    OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0321:
            if (bits == 16) {
                *bytes = 0x66;
                out(offset, segment, bytes,
                    OUT_RAWDATA + 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0322:
            break;

        case 0330:
            *bytes = *codes++ ^ condval[ins->condition];
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 0331:
        case 0332:
            break;

        case 0333:
            *bytes = 0xF3;
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 0340:
        case 0341:
        case 0342:
            if (ins->oprs[0].segment != NO_SEG)
                errfunc(ERR_PANIC, "non-constant BSS size in pass two");
            else {
                long size = ins->oprs[0].offset << (c - 0340);
                if (size > 0)
                    out(offset, segment, NULL,
                        OUT_RESERVE + size, NO_SEG, NO_SEG);
                offset += size;
            }
            break;

        case 0370:
        case 0371:
        case 0372:
            break;

        case 0373:
            *bytes = bits == 16 ? 3 : 5;
            out(offset, segment, bytes, OUT_RAWDATA + 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        default:               /* can't do it by 'case' statements */
            if (c >= 0100 && c <= 0277) {       /* it's an EA */
                ea ea_data;
                int rfield;
                unsigned char *p;
                long s;

                if (c <= 0177)  /* pick rfield from operand b */
                    rfield = regval(&ins->oprs[c & 7]);
                else            /* rfield is constant */
                    rfield = c & 7;

                if (!process_ea
                    (&ins->oprs[(c >> 3) & 7], &ea_data, bits, rfield,
                     ins->forw_ref)) {
                    errfunc(ERR_NONFATAL, "invalid effective address");
                }

                p = bytes;
                *p++ = ea_data.modrm;
                if (ea_data.sib_present)
                    *p++ = ea_data.sib;

                s = p - bytes;
                out(offset, segment, bytes, OUT_RAWDATA + s,
                    NO_SEG, NO_SEG);

                switch (ea_data.bytes) {
                case 0:
                    break;
                case 1:
                    if (ins->oprs[(c >> 3) & 7].segment != NO_SEG) {
                        data = ins->oprs[(c >> 3) & 7].offset;
                        out(offset, segment, &data, OUT_ADDRESS + 1,
                            ins->oprs[(c >> 3) & 7].segment,
                            ins->oprs[(c >> 3) & 7].wrt);
                    } else {
                        *bytes = ins->oprs[(c >> 3) & 7].offset;
                        out(offset, segment, bytes, OUT_RAWDATA + 1,
                            NO_SEG, NO_SEG);
                    }
                    s++;
                    break;
                case 2:
                case 4:
                    data = ins->oprs[(c >> 3) & 7].offset;
                    out(offset, segment, &data,
                        OUT_ADDRESS + ea_data.bytes,
                        ins->oprs[(c >> 3) & 7].segment,
                        ins->oprs[(c >> 3) & 7].wrt);
                    s += ea_data.bytes;
                    break;
                }
                offset += s;
            } else
                errfunc(ERR_PANIC, "internal instruction table corrupt"
                        ": instruction code 0x%02X given", c);
        }
}

#include "regvals.c"

static int regval(operand * o)
{
    if (o->basereg < EXPR_REG_START || o->basereg >= REG_ENUM_LIMIT) {
        errfunc(ERR_PANIC, "invalid operand passed to regval()");
    }
    return regvals[o->basereg];
}

static int matches(struct itemplate *itemp, insn * instruction)
{
    int i, size[3], asize, oprs, ret;

    ret = 100;

    /*
     * Check the opcode
     */
    if (itemp->opcode != instruction->opcode)
        return 0;

    /*
     * Count the operands
     */
    if (itemp->operands != instruction->operands)
        return 0;

    /*
     * Check that no spurious colons or TOs are present
     */
    for (i = 0; i < itemp->operands; i++)
        if (instruction->oprs[i].type & ~itemp->opd[i] & (COLON | TO))
            return 0;

    /*
     * Check that the operand flags all match up
     */
    for (i = 0; i < itemp->operands; i++)
        if (itemp->opd[i] & ~instruction->oprs[i].type ||
            ((itemp->opd[i] & SIZE_MASK) &&
             ((itemp->opd[i] ^ instruction->oprs[i].type) & SIZE_MASK))) {
            if ((itemp->opd[i] & ~instruction->oprs[i].type & NON_SIZE) ||
                (instruction->oprs[i].type & SIZE_MASK))
                return 0;
            else
/*		ret = 1;   */
                return 1;
        }

    /*
     * Check operand sizes
     */
    if (itemp->flags & IF_ARMASK) {
        size[0] = size[1] = size[2] = 0;

        switch (itemp->flags & IF_ARMASK) {
        case IF_AR0:
            i = 0;
            break;
        case IF_AR1:
            i = 1;
            break;
        case IF_AR2:
            i = 2;
            break;
        default:
            break;              /* Shouldn't happen */
        }
        if (itemp->flags & IF_SB) {
            size[i] = BITS8;
        } else if (itemp->flags & IF_SW) {
            size[i] = BITS16;
        } else if (itemp->flags & IF_SD) {
            size[i] = BITS32;
        }
    } else {
        asize = 0;
        if (itemp->flags & IF_SB) {
            asize = BITS8;
            oprs = itemp->operands;
        } else if (itemp->flags & IF_SW) {
            asize = BITS16;
            oprs = itemp->operands;
        } else if (itemp->flags & IF_SD) {
            asize = BITS32;
            oprs = itemp->operands;
        }
        size[0] = size[1] = size[2] = asize;
    }

    if (itemp->flags & (IF_SM | IF_SM2)) {
        oprs = (itemp->flags & IF_SM2 ? 2 : itemp->operands);
        asize = 0;
        for (i = 0; i < oprs; i++) {
            if ((asize = itemp->opd[i] & SIZE_MASK) != 0) {
                int j;
                for (j = 0; j < oprs; j++)
                    size[j] = asize;
                break;
            }
        }
    } else {
        oprs = itemp->operands;
    }

    for (i = 0; i < itemp->operands; i++)
        if (!(itemp->opd[i] & SIZE_MASK) &&
            (instruction->oprs[i].type & SIZE_MASK & ~size[i]))
/*	    ret = 2;  */
            return 2;

    /*
     * Check template is okay at the set cpu level
     */
    if ((itemp->flags & IF_PLEVEL) > cpu)
        return 3;

    /*
     * Check if special handling needed for Jumps
     */
    if ((unsigned char)(itemp->code[0]) >= 0370)
        return 99;

    return ret;
}

static ea *process_ea(operand * input, ea * output, int addrbits,
                      int rfield, int forw_ref)
{
    if (!(REGISTER & ~input->type)) {   /* it's a single register */
        static int regs[] = {
            R_AL, R_CL, R_DL, R_BL, R_AH, R_CH, R_DH, R_BH,
            R_AX, R_CX, R_DX, R_BX, R_SP, R_BP, R_SI, R_DI,
            R_EAX, R_ECX, R_EDX, R_EBX, R_ESP, R_EBP, R_ESI, R_EDI,
            R_MM0, R_MM1, R_MM2, R_MM3, R_MM4, R_MM5, R_MM6, R_MM7,
            R_XMM0, R_XMM1, R_XMM2, R_XMM3, R_XMM4, R_XMM5, R_XMM6, R_XMM7
        };
        int i;

        for (i = 0; i < elements(regs); i++)
            if (input->basereg == regs[i])
                break;
        if (i < elements(regs)) {
            output->sib_present = FALSE;        /* no SIB necessary */
            output->bytes = 0;  /* no offset necessary either */
            output->modrm = 0xC0 | (rfield << 3) | (i & 7);
        } else
            return NULL;
    } else {                    /* it's a memory reference */
        if (input->basereg == -1
            && (input->indexreg == -1 || input->scale == 0)) {
            /* it's a pure offset */
            if (input->addr_size)
                addrbits = input->addr_size;
            output->sib_present = FALSE;
            output->bytes = (addrbits == 32 ? 4 : 2);
            output->modrm = (addrbits == 32 ? 5 : 6) | (rfield << 3);
        } else {                /* it's an indirection */
            int i = input->indexreg, b = input->basereg, s = input->scale;
            long o = input->offset, seg = input->segment;
            int hb = input->hintbase, ht = input->hinttype;
            int t;

            if (s == 0)
                i = -1;         /* make this easy, at least */

            if (i == R_EAX || i == R_EBX || i == R_ECX || i == R_EDX
                || i == R_EBP || i == R_ESP || i == R_ESI || i == R_EDI
                || b == R_EAX || b == R_EBX || b == R_ECX || b == R_EDX
                || b == R_EBP || b == R_ESP || b == R_ESI || b == R_EDI) {
                /* it must be a 32-bit memory reference. Firstly we have
                 * to check that all registers involved are type Exx. */
                if (i != -1 && i != R_EAX && i != R_EBX && i != R_ECX
                    && i != R_EDX && i != R_EBP && i != R_ESP && i != R_ESI
                    && i != R_EDI)
                    return NULL;
                if (b != -1 && b != R_EAX && b != R_EBX && b != R_ECX
                    && b != R_EDX && b != R_EBP && b != R_ESP && b != R_ESI
                    && b != R_EDI)
                    return NULL;

                /* While we're here, ensure the user didn't specify WORD. */
                if (input->addr_size == 16)
                    return NULL;

                /* now reorganise base/index */
                if (s == 1 && b != i && b != -1 && i != -1 &&
                    ((hb == b && ht == EAH_NOTBASE)
                     || (hb == i && ht == EAH_MAKEBASE)))
                    t = b, b = i, i = t;        /* swap if hints say so */
                if (b == i)     /* convert EAX+2*EAX to 3*EAX */
                    b = -1, s++;
                if (b == -1 && s == 1 && !(hb == i && ht == EAH_NOTBASE))
                    b = i, i = -1;      /* make single reg base, unless hint */
                if (((s == 2 && i != R_ESP
                      && !(input->eaflags & EAF_TIMESTWO)) || s == 3
                     || s == 5 || s == 9) && b == -1)
                    b = i, s--; /* convert 3*EAX to EAX+2*EAX */
                if (i == -1 && b != R_ESP
                    && (input->eaflags & EAF_TIMESTWO))
                    i = b, b = -1, s = 1;
                /* convert [NOSPLIT EAX] to sib format with 0x0 displacement */
                if (s == 1 && i == R_ESP)       /* swap ESP into base if scale is 1 */
                    i = b, b = R_ESP;
                if (i == R_ESP
                    || (s != 1 && s != 2 && s != 4 && s != 8 && i != -1))
                    return NULL;        /* wrong, for various reasons */

                if (i == -1 && b != R_ESP) {    /* no SIB needed */
                    int mod, rm;
                    switch (b) {
                    case R_EAX:
                        rm = 0;
                        break;
                    case R_ECX:
                        rm = 1;
                        break;
                    case R_EDX:
                        rm = 2;
                        break;
                    case R_EBX:
                        rm = 3;
                        break;
                    case R_EBP:
                        rm = 5;
                        break;
                    case R_ESI:
                        rm = 6;
                        break;
                    case R_EDI:
                        rm = 7;
                        break;
                    case -1:
                        rm = 5;
                        break;
                    default:   /* should never happen */
                        return NULL;
                    }
                    if (b == -1 || (b != R_EBP && o == 0 &&
                                    seg == NO_SEG && !forw_ref &&
                                    !(input->eaflags &
                                      (EAF_BYTEOFFS | EAF_WORDOFFS))))
                        mod = 0;
                    else if (input->eaflags & EAF_BYTEOFFS ||
                             (o >= -128 && o <= 127 && seg == NO_SEG
                              && !forw_ref
                              && !(input->eaflags & EAF_WORDOFFS))) {
                        mod = 1;
                    } else
                        mod = 2;

                    output->sib_present = FALSE;
                    output->bytes = (b == -1 || mod == 2 ? 4 : mod);
                    output->modrm = (mod << 6) | (rfield << 3) | rm;
                } else {        /* we need a SIB */
                    int mod, scale, index, base;

                    switch (b) {
                    case R_EAX:
                        base = 0;
                        break;
                    case R_ECX:
                        base = 1;
                        break;
                    case R_EDX:
                        base = 2;
                        break;
                    case R_EBX:
                        base = 3;
                        break;
                    case R_ESP:
                        base = 4;
                        break;
                    case R_EBP:
                    case -1:
                        base = 5;
                        break;
                    case R_ESI:
                        base = 6;
                        break;
                    case R_EDI:
                        base = 7;
                        break;
                    default:   /* then what the smeg is it? */
                        return NULL;    /* panic */
                    }

                    switch (i) {
                    case R_EAX:
                        index = 0;
                        break;
                    case R_ECX:
                        index = 1;
                        break;
                    case R_EDX:
                        index = 2;
                        break;
                    case R_EBX:
                        index = 3;
                        break;
                    case -1:
                        index = 4;
                        break;
                    case R_EBP:
                        index = 5;
                        break;
                    case R_ESI:
                        index = 6;
                        break;
                    case R_EDI:
                        index = 7;
                        break;
                    default:   /* then what the smeg is it? */
                        return NULL;    /* panic */
                    }

                    if (i == -1)
                        s = 1;
                    switch (s) {
                    case 1:
                        scale = 0;
                        break;
                    case 2:
                        scale = 1;
                        break;
                    case 4:
                        scale = 2;
                        break;
                    case 8:
                        scale = 3;
                        break;
                    default:   /* then what the smeg is it? */
                        return NULL;    /* panic */
                    }

                    if (b == -1 || (b != R_EBP && o == 0 &&
                                    seg == NO_SEG && !forw_ref &&
                                    !(input->eaflags &
                                      (EAF_BYTEOFFS | EAF_WORDOFFS))))
                        mod = 0;
                    else if (input->eaflags & EAF_BYTEOFFS ||
                             (o >= -128 && o <= 127 && seg == NO_SEG
                              && !forw_ref
                              && !(input->eaflags & EAF_WORDOFFS)))
                        mod = 1;
                    else
                        mod = 2;

                    output->sib_present = TRUE;
                    output->bytes = (b == -1 || mod == 2 ? 4 : mod);
                    output->modrm = (mod << 6) | (rfield << 3) | 4;
                    output->sib = (scale << 6) | (index << 3) | base;
                }
            } else {            /* it's 16-bit */
                int mod, rm;

                /* check all registers are BX, BP, SI or DI */
                if ((b != -1 && b != R_BP && b != R_BX && b != R_SI
                     && b != R_DI) || (i != -1 && i != R_BP && i != R_BX
                                       && i != R_SI && i != R_DI))
                    return NULL;

                /* ensure the user didn't specify DWORD */
                if (input->addr_size == 32)
                    return NULL;

                if (s != 1 && i != -1)
                    return NULL;        /* no can do, in 16-bit EA */
                if (b == -1 && i != -1) {
                    int tmp = b;
                    b = i;
                    i = tmp;
                }               /* swap */
                if ((b == R_SI || b == R_DI) && i != -1) {
                    int tmp = b;
                    b = i;
                    i = tmp;
                }
                /* have BX/BP as base, SI/DI index */
                if (b == i)
                    return NULL;        /* shouldn't ever happen, in theory */
                if (i != -1 && b != -1 &&
                    (i == R_BP || i == R_BX || b == R_SI || b == R_DI))
                    return NULL;        /* invalid combinations */
                if (b == -1)    /* pure offset: handled above */
                    return NULL;        /* so if it gets to here, panic! */

                rm = -1;
                if (i != -1)
                    switch (i * 256 + b) {
                    case R_SI * 256 + R_BX:
                        rm = 0;
                        break;
                    case R_DI * 256 + R_BX:
                        rm = 1;
                        break;
                    case R_SI * 256 + R_BP:
                        rm = 2;
                        break;
                    case R_DI * 256 + R_BP:
                        rm = 3;
                        break;
                } else
                    switch (b) {
                    case R_SI:
                        rm = 4;
                        break;
                    case R_DI:
                        rm = 5;
                        break;
                    case R_BP:
                        rm = 6;
                        break;
                    case R_BX:
                        rm = 7;
                        break;
                    }
                if (rm == -1)   /* can't happen, in theory */
                    return NULL;        /* so panic if it does */

                if (o == 0 && seg == NO_SEG && !forw_ref && rm != 6 &&
                    !(input->eaflags & (EAF_BYTEOFFS | EAF_WORDOFFS)))
                    mod = 0;
                else if (input->eaflags & EAF_BYTEOFFS ||
                         (o >= -128 && o <= 127 && seg == NO_SEG
                          && !forw_ref
                          && !(input->eaflags & EAF_WORDOFFS)))
                    mod = 1;
                else
                    mod = 2;

                output->sib_present = FALSE;    /* no SIB - it's 16-bit */
                output->bytes = mod;    /* bytes of offset needed */
                output->modrm = (mod << 6) | (rfield << 3) | rm;
            }
        }
    }
    output->size = 1 + output->sib_present + output->bytes;
    return output;
}

static int chsize(operand * input, int addrbits)
{
    if (!(MEMORY & ~input->type)) {
        int i = input->indexreg, b = input->basereg;

        if (input->scale == 0)
            i = -1;

        if (i == -1 && b == -1) /* pure offset */
            return (input->addr_size != 0 && input->addr_size != addrbits);

        if (i == R_EAX || i == R_EBX || i == R_ECX || i == R_EDX
            || i == R_EBP || i == R_ESP || i == R_ESI || i == R_EDI
            || b == R_EAX || b == R_EBX || b == R_ECX || b == R_EDX
            || b == R_EBP || b == R_ESP || b == R_ESI || b == R_EDI)
            return (addrbits == 16);
        else
            return (addrbits == 32);
    } else
        return 0;
}