assemble.c

/* ----------------------------------------------------------------------- *
 *
 *   Copyright 1996-2010 The NASM Authors - All Rights Reserved
 *   See the file AUTHORS included with the NASM distribution for
 *   the specific copyright holders.
 *
 *   Redistribution and use in source and binary forms, with or without
 *   modification, are permitted provided that the following
 *   conditions are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *
 *     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 *     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 *     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 *     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 *     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 *     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 *     EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * ----------------------------------------------------------------------- */

/*
 * assemble.c   code generation for the Netwide Assembler
 *
 * the actual codes (C syntax, i.e. octal):
 * \0            - terminates the code. (Unless it's a literal of course.)
 * \1..\4	 - that many literal bytes follow in the code stream
 * \5            - add 4 to the primary operand number (b, low octdigit)
 * \6            - add 4 to the secondary operand number (a, middle octdigit)
 * \7            - add 4 to both the primary and the secondary operand number
 * \10..\13      - a literal byte follows in the code stream, to be added
 *                 to the register value of operand 0..3
 * \14..\17      - a signed byte immediate operand, from operand 0..3
 * \20..\23      - a byte immediate operand, from operand 0..3
 * \24..\27      - an unsigned byte immediate operand, from operand 0..3
 * \30..\33      - a word immediate operand, from operand 0..3
 * \34..\37      - select between \3[0-3] and \4[0-3] depending on 16/32 bit
 *                 assembly mode or the operand-size override on the operand
 * \40..\43      - a long immediate operand, from operand 0..3
 * \44..\47      - select between \3[0-3], \4[0-3] and \5[4-7]
 *		   depending on the address size of the instruction.
 * \50..\53      - a byte relative operand, from operand 0..3
 * \54..\57      - a qword immediate operand, from operand 0..3
 * \60..\63      - a word relative operand, from operand 0..3
 * \64..\67      - select between \6[0-3] and \7[0-3] depending on 16/32 bit
 *                 assembly mode or the operand-size override on the operand
 * \70..\73      - a long relative operand, from operand 0..3
 * \74..\77      - a word constant, from the _segment_ part of operand 0..3
 * \1ab          - a ModRM, calculated on EA in operand a, with the spare
 *                 field the register value of operand b.
 * \140..\143    - an immediate word or signed byte for operand 0..3
 * \144..\147    - or 2 (s-field) into opcode byte if operand 0..3
 *		    is a signed byte rather than a word.  Opcode byte follows.
 * \150..\153    - an immediate dword or signed byte for operand 0..3
 * \154..\157    - or 2 (s-field) into opcode byte if operand 0..3
 *		    is a signed byte rather than a dword.  Opcode byte follows.
 * \160..\163    - this instruction uses DREX rather than REX, with the
 *		   OC0 field set to 0, and the dest field taken from
 *                 operand 0..3.
 * \164..\167    - this instruction uses DREX rather than REX, with the
 *		   OC0 field set to 1, and the dest field taken from
 *                 operand 0..3.
 * \171		 - placement of DREX suffix in the absence of an EA
 * \172\ab	 - the register number from operand a in bits 7..4, with
 *                 the 4-bit immediate from operand b in bits 3..0.
 * \173\xab	 - the register number from operand a in bits 7..4, with
 *		   the value b in bits 3..0.
 * \174\a	 - the register number from operand a in bits 7..4, and
 *		   an arbitrary value in bits 3..0 (assembled as zero.)
 * \2ab          - a ModRM, calculated on EA in operand a, with the spare
 *                 field equal to digit b.
 * \250..\253    - same as \150..\153, except warn if the 64-bit operand
 *                 is not equal to the truncated and sign-extended 32-bit
 *                 operand; used for 32-bit immediates in 64-bit mode.
 * \254..\257    - a signed 32-bit operand to be extended to 64 bits.
 * \260..\263    - this instruction uses VEX/XOP rather than REX, with the
 *		   V field taken from operand 0..3.
 * \270		 - this instruction uses VEX/XOP rather than REX, with the
 *		   V field set to 1111b.
 *
 * VEX/XOP prefixes are followed by the sequence:
 * \tmm\wlp        where mm is the M field; and wlp is:
 *                 00 0ww lpp
 *                 [w0] ww = 0 for W = 0
 *                 [w1] ww = 1 for W = 1
 *                 [wx] ww = 2 for W don't care (always assembled as 0)
 *                 [ww] ww = 3 for W used as REX.W
 *
 * t = 0 for VEX (C4/C5), t = 1 for XOP (8F).
 *
 * \274..\277    - a signed byte immediate operand, from operand 0..3,
 *                 which is to be extended to the operand size.
 * \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) invalid with non-default address size.
 * \313          - indicates fixed 64-bit address size, 0x67 invalid.
 * \314          - (disassembler only) invalid with REX.B
 * \315          - (disassembler only) invalid with REX.X
 * \316          - (disassembler only) invalid with REX.R
 * \317          - (disassembler only) invalid with REX.W
 * \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)
 * \323          - indicates fixed 64-bit operand size, REX on extensions only.
 * \324          - indicates 64-bit operand size requiring REX prefix.
 * \325		 - instruction which always uses spl/bpl/sil/dil
 * \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          - REP prefix (0xF2 byte) used as opcode extension.
 * \333          - REP prefix (0xF3 byte) used as opcode extension.
 * \334          - LOCK prefix used as REX.R (used in non-64-bit mode)
 * \335          - disassemble a rep (0xF3 byte) prefix as repe not rep.
 * \336          - force a REP(E) prefix (0xF2) even if not specified.
 * \337		 - force a REPNE prefix (0xF3) even if not specified.
 *                 \336-\337 are still listed as prefixes in the disassembler.
 * \340          - reserve <operand 0> bytes of uninitialized storage.
 *                 Operand 0 had better be a segmentless constant.
 * \341		 - this instruction needs a WAIT "prefix"
 * \344,\345     - the PUSH/POP (respectively) codes for CS, DS, ES, SS
 *                 (POP is never used for CS) depending on operand 0
 * \346,\347     - the second byte of PUSH/POP codes for FS, GS, depending
 *                 on operand 0
 * \360		 - no SSE prefix (== \364\331)
 * \361          - 66 SSE prefix (== \366\331)
 * \362          - F2 SSE prefix (== \364\332)
 * \363          - F3 SSE prefix (== \364\333)
 * \364          - operand-size prefix (0x66) not permitted
 * \365          - address-size prefix (0x67) not permitted
 * \366          - operand-size prefix (0x66) used as opcode extension
 * \367          - address-size prefix (0x67) used as opcode extension
 * \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 "compiler.h"

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

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

enum match_result {
    /*
     * Matching errors.  These should be sorted so that more specific
     * errors come later in the sequence.
     */
    MERR_INVALOP,
    MERR_OPSIZEMISSING,
    MERR_OPSIZEMISMATCH,
    MERR_BADCPU,
    MERR_BADMODE,
    /*
     * Matching success; the conditional ones first
     */
    MOK_JUMP,			/* Matching OK but needs jmp_match() */
    MOK_GOOD			/* Matching unconditionally OK */
};

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 */
    uint8_t modrm, sib, rex, rip;    /* the bytes themselves */
} ea;

static uint32_t cpu;            /* cpu level received from nasm.c */
static efunc errfunc;
static struct ofmt *outfmt;
static ListGen *list;

static int64_t calcsize(int32_t, int64_t, int, insn *, const uint8_t *);
static void gencode(int32_t segment, int64_t offset, int bits,
                    insn * ins, const struct itemplate *temp,
		    int64_t insn_end);
static enum match_result find_match(const struct itemplate **tempp,
				    insn *instruction,
				    int32_t segment, int64_t offset, int bits);
static enum match_result matches(const struct itemplate *, insn *, int bits);
static opflags_t regflag(const operand *);
static int32_t regval(const operand *);
static int rexflags(int, opflags_t, int);
static int op_rexflags(const operand *, int);
static ea *process_ea(operand *, ea *, int, int, int, opflags_t);
static void add_asp(insn *, int);

static int has_prefix(insn * ins, enum prefix_pos pos, enum prefixes prefix)
{
    return ins->prefixes[pos] == prefix;
}

static void assert_no_prefix(insn * ins, enum prefix_pos pos)
{
    if (ins->prefixes[pos])
	errfunc(ERR_NONFATAL, "invalid %s prefix",
		prefix_name(ins->prefixes[pos]));
}

static const char *size_name(int size)
{
    switch (size) {
    case 1:
	return "byte";
    case 2:
	return "word";
    case 4:
	return "dword";
    case 8:
	return "qword";
    case 10:
	return "tword";
    case 16:
	return "oword";
    case 32:
	return "yword";
    default:
	return "???";
    }
}

static void warn_overflow(int pass, int size)
{
    errfunc(ERR_WARNING | pass | ERR_WARN_NOV,
            "%s data exceeds bounds", size_name(size));
}

static void warn_overflow_const(int64_t data, int size)
{
    if (overflow_general(data, size))
        warn_overflow(ERR_PASS1, size);
}

static void warn_overflow_opd(const struct operand *o, int size)
{
    if (o->wrt == NO_SEG && o->segment == NO_SEG) {
        if (overflow_general(o->offset, size))
            warn_overflow(ERR_PASS2, size);
    }
}

/*
 * 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(int64_t offset, int32_t segto, const void *data,
                enum out_type type, uint64_t size,
		int32_t segment, int32_t wrt)
{
    static int32_t lineno = 0;     /* static!!! */
    static char *lnfname = NULL;
    uint8_t p[8];

    if (type == OUT_ADDRESS && segment == NO_SEG && wrt == NO_SEG) {
	/*
	 * This is a non-relocated address, and we're going to
	 * convert it into RAWDATA format.
	 */
	uint8_t *q = p;

	if (size > 8) {
	    errfunc(ERR_PANIC, "OUT_ADDRESS with size > 8");
	    return;
	}

	WRITEADDR(q, *(int64_t *)data, size);
	data = p;
	type = OUT_RAWDATA;
    }

    list->output(offset, data, type, size);

    /*
     * 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, size, segment, wrt);
}

static bool jmp_match(int32_t segment, int64_t offset, int bits,
                     insn * ins, const uint8_t *code)
{
    int64_t isize;
    uint8_t c = code[0];

    if ((c != 0370 && c != 0371) || (ins->oprs[0].type & STRICT))
        return false;
    if (!optimizing)
	return false;
    if (optimizing < 0 && c == 0371)
	return false;

    isize = calcsize(segment, offset, bits, ins, code);

    if (ins->oprs[0].opflags & OPFLAG_UNKNOWN)
        /* Be optimistic in pass 1 */
        return true;

    if (ins->oprs[0].segment != segment)
        return false;

    isize = ins->oprs[0].offset - offset - isize; /* isize is delta */
    return (isize >= -128 && isize <= 127); /* is it byte size? */
}

int64_t assemble(int32_t segment, int64_t offset, int bits, uint32_t cp,
		 insn * instruction, struct ofmt *output, efunc error,
		 ListGen * listgen)
{
    const struct itemplate *temp;
    int j;
    enum match_result m;
    int64_t insn_end;
    int32_t itimes;
    int64_t start = offset;
    int64_t wsize;              /* size for DB etc. */

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

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

    if (wsize) {
        extop *e;
        int32_t t = instruction->times;
        if (t < 0)
            errfunc(ERR_PANIC,
                    "instruction->times < 0 (%ld) in assemble()", t);

        while (t--) {           /* repeat TIMES times */
            list_for_each(e, instruction->eops) {
                if (e->type == EOT_DB_NUMBER) {
		    if (wsize > 8) {
                        errfunc(ERR_NONFATAL,
				"integer supplied to a DT, DO or DY"
                                " instruction");
                    } else {
                        out(offset, segment, &e->offset,
                            OUT_ADDRESS, wsize, e->segment, e->wrt);
			offset += wsize;
		    }
                } else if (e->type == EOT_DB_STRING ||
			   e->type == EOT_DB_STRING_FREE) {
                    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, zero_buffer,
                            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, 0);
                list->uplevel(LIST_TIMES);
            }
        }
        if (instruction->times > 1)
            list->downlevel(LIST_TIMES);
        return offset - start;
    }

    if (instruction->opcode == I_INCBIN) {
        const char *fname = instruction->eops->stringval;
        FILE *fp;

	fp = fopen(fname, "rb");
	if (!fp) {
            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[4096];
            size_t t = instruction->times;
            size_t base = 0;
	    size_t len;

            len = ftell(fp);
            if (instruction->eops->next) {
                base = instruction->eops->next->offset;
                len -= base;
                if (instruction->eops->next->next &&
                    len > (size_t)instruction->eops->next->next->offset)
                    len = (size_t)instruction->eops->next->next->offset;
            }
            /*
             * Dummy call to list->output to give the offset to the
             * listing module.
             */
            list->output(offset, NULL, OUT_RAWDATA, 0);
            list->uplevel(LIST_INCBIN);
            while (t--) {
                size_t l;

                fseek(fp, base, SEEK_SET);
                l = len;
                while (l > 0) {
                    int32_t m;
		    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, 0);
                list->uplevel(LIST_TIMES);
                list->downlevel(LIST_TIMES);
            }
            fclose(fp);
            return instruction->times * len;
        }
        return 0;               /* if we're here, there's an error */
    }

    /* Check to see if we need an address-size prefix */
    add_asp(instruction, bits);

    m = find_match(&temp, instruction, segment, offset, bits);

    if (m == MOK_GOOD) {
	/* Matches! */
	int64_t insn_size = calcsize(segment, offset, bits,
				     instruction, temp->code);
	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 < MAXPREFIX; j++) {
		    uint8_t c = 0;
		    switch (instruction->prefixes[j]) {
		    case P_WAIT:
			c = 0x9B;
			break;
		    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:
			if (bits == 64) {
			    error(ERR_WARNING | ERR_PASS2,
				  "cs segment base generated, but will be ignored in 64-bit mode");
			}
			c = 0x2E;
			break;
		    case R_DS:
			if (bits == 64) {
			    error(ERR_WARNING | ERR_PASS2,
				  "ds segment base generated, but will be ignored in 64-bit mode");
			}
			c = 0x3E;
			break;
		    case R_ES:
			if (bits == 64) {
			    error(ERR_WARNING | ERR_PASS2,
				  "es segment base generated, but will be ignored in 64-bit mode");
			}
			c = 0x26;
			break;
		    case R_FS:
			c = 0x64;
			break;
		    case R_GS:
			c = 0x65;
			break;
		    case R_SS:
			if (bits == 64) {
			    error(ERR_WARNING | ERR_PASS2,
				  "ss segment base generated, but will be ignored in 64-bit mode");
			}
			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 == 64) {
			    error(ERR_NONFATAL,
				  "16-bit addressing is not supported "
				  "in 64-bit mode");
			} else if (bits != 16)
			    c = 0x67;
			break;
		    case P_A32:
			if (bits != 32)
			    c = 0x67;
			break;
		    case P_A64:
			if (bits != 64) {
			    error(ERR_NONFATAL,
				  "64-bit addressing is only supported "
				  "in 64-bit mode");
			}
			break;
		    case P_ASP:
			c = 0x67;
			break;
		    case P_O16:
			if (bits != 16)
			    c = 0x66;
			break;
		    case P_O32:
			if (bits == 16)
			    c = 0x66;
			break;
		    case P_O64:
			/* REX.W */
			break;
		    case P_OSP:
			c = 0x66;
			break;
		    case P_none:
			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,
			temp, 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, 0);
		    list->uplevel(LIST_TIMES);
		}
	    }
	if (instruction->times > 1)
	    list->downlevel(LIST_TIMES);
	return offset - start;
    } else {
	/* No match */
	switch (m) {
	case MERR_OPSIZEMISSING:
	    error(ERR_NONFATAL, "operation size not specified");
	    break;
	case MERR_OPSIZEMISMATCH:
            error(ERR_NONFATAL, "mismatch in operand sizes");
	    break;
	case MERR_BADCPU:
            error(ERR_NONFATAL, "no instruction for this cpu level");
	    break;
	case MERR_BADMODE:
            error(ERR_NONFATAL, "instruction not supported in %d-bit mode",
		  bits);
	    break;
	default:
            error(ERR_NONFATAL,
                  "invalid combination of opcode and operands");
	    break;
	}
    }
    return 0;
}

int64_t insn_size(int32_t segment, int64_t offset, int bits, uint32_t cp,
		  insn * instruction, efunc error)
{
    const struct itemplate *temp;
    enum match_result m;

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

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

    if (instruction->opcode == I_DB || instruction->opcode == I_DW ||
        instruction->opcode == I_DD || instruction->opcode == I_DQ ||
	instruction->opcode == I_DT || instruction->opcode == I_DO ||
	instruction->opcode == I_DY) {
        extop *e;
        int32_t isize, osize, wsize;

        isize = 0;
        wsize = idata_bytes(instruction->opcode);

        list_for_each(e, instruction->eops) {
            int32_t align;

            osize = 0;
            if (e->type == EOT_DB_NUMBER) {
                osize = 1;
                warn_overflow_const(e->offset, wsize);
            } else if (e->type == EOT_DB_STRING ||
                       e->type == EOT_DB_STRING_FREE)
                osize = e->stringlen;

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

    if (instruction->opcode == I_INCBIN) {
	const char *fname = instruction->eops->stringval;
        FILE *fp;
        int64_t val = 0;
        size_t len;

	fp = fopen(fname, "rb");
	if (!fp)
            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);
            if (instruction->eops->next) {
                len -= instruction->eops->next->offset;
                if (instruction->eops->next->next &&
                    len > (size_t)instruction->eops->next->next->offset) {
                    len = (size_t)instruction->eops->next->next->offset;
                }
            }
            val = instruction->times * len;
        }
        if (fp)
            fclose(fp);
        return val;
    }

    /* Check to see if we need an address-size prefix */
    add_asp(instruction, bits);

    m = find_match(&temp, instruction, segment, offset, bits);
    if (m == MOK_GOOD) {
	/* we've matched an instruction. */
	int64_t isize;
	const uint8_t *codes = temp->code;
	int j;

	isize = calcsize(segment, offset, bits, instruction, codes);
	if (isize < 0)
	    return -1;
	for (j = 0; j < MAXPREFIX; j++) {
	    switch (instruction->prefixes[j]) {
	    case P_A16:
		if (bits != 16)
		    isize++;
		break;
	    case P_A32:
		if (bits != 32)
		    isize++;
		break;
	    case P_O16:
		if (bits != 16)
		    isize++;
		break;
	    case P_O32:
		if (bits == 16)
		    isize++;
		break;
	    case P_A64:
	    case P_O64:
	    case P_none:
		break;
	    default:
		isize++;
		break;
	    }
	}
	return isize * instruction->times;
    } else {
	return -1;                  /* didn't match any instruction */
    }
}

static bool possible_sbyte(operand *o)
{
    return o->wrt == NO_SEG && o->segment == NO_SEG &&
	!(o->opflags & OPFLAG_UNKNOWN) &&
	optimizing >= 0 && !(o->type & STRICT);
}

/* check that opn[op]  is a signed byte of size 16 or 32 */
static bool is_sbyte16(operand *o)
{
    int16_t v;

    if (!possible_sbyte(o))
	return false;

    v = o->offset;
    return v >= -128 && v <= 127;
}

static bool is_sbyte32(operand *o)
{
    int32_t v;

    if (!possible_sbyte(o))
	return false;

    v = o->offset;
    return v >= -128 && v <= 127;
}

/* Common construct */
#define case4(x) case (x): case (x)+1: case (x)+2: case (x)+3

static int64_t calcsize(int32_t segment, int64_t offset, int bits,
			insn * ins, const uint8_t *codes)
{
    int64_t length = 0;
    uint8_t c;
    int rex_mask = ~0;
    int op1, op2;
    struct operand *opx;
    uint8_t opex = 0;

    ins->rex = 0;               /* Ensure REX is reset */

    if (ins->prefixes[PPS_OSIZE] == P_O64)
	ins->rex |= REX_W;

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

    while (*codes) {
	c = *codes++;
	op1 = (c & 3) + ((opex & 1) << 2);
	op2 = ((c >> 3) & 3) + ((opex & 2) << 1);
	opx = &ins->oprs[op1];
	opex = 0;		/* For the next iteration */

        switch (c) {
        case 01:
        case 02:
        case 03:
	case 04:
            codes += c, length += c;
            break;

	case 05:
	case 06:
	case 07:
	    opex = c;
	    break;

	case4(010):
	    ins->rex |=
		op_rexflags(opx, REX_B|REX_H|REX_P|REX_W);
            codes++, length++;
            break;

	case4(014):
	case4(020):
	case4(024):
            length++;
            break;

	case4(030):
            length += 2;
            break;

	case4(034):
            if (opx->type & (BITS16 | BITS32 | BITS64))
                length += (opx->type & BITS16) ? 2 : 4;
            else
                length += (bits == 16) ? 2 : 4;
            break;

	case4(040):
            length += 4;
            break;

	case4(044):
            length += ins->addr_size >> 3;
            break;

	case4(050):
            length++;
            break;

	case4(054):
            length += 8; /* MOV reg64/imm */
            break;

	case4(060):
            length += 2;
            break;

	case4(064):
            if (opx->type & (BITS16 | BITS32 | BITS64))
                length += (opx->type & BITS16) ? 2 : 4;
            else
                length += (bits == 16) ? 2 : 4;
            break;

	case4(070):
            length += 4;
            break;

	case4(074):
            length += 2;
            break;

	case4(0140):
            length += is_sbyte16(opx) ? 1 : 2;
            break;

	case4(0144):
            codes++;
            length++;
            break;

	case4(0150):
            length += is_sbyte32(opx) ? 1 : 4;
            break;

	case4(0154):
            codes++;
            length++;
            break;

	case4(0160):
	    length++;
	    ins->rex |= REX_D;
	    ins->drexdst = regval(opx);
	    break;

	case4(0164):
	    length++;
	    ins->rex |= REX_D|REX_OC;
	    ins->drexdst = regval(opx);
	    break;

	case 0171:
	    break;

	case 0172:
	case 0173:
	case 0174:
	    codes++;
	    length++;
	    break;

	case4(0250):
            length += is_sbyte32(opx) ? 1 : 4;
            break;

	case4(0254):
	    length += 4;
	    break;

	case4(0260):
	    ins->rex |= REX_V;
	    ins->drexdst = regval(opx);
	    ins->vex_cm = *codes++;
	    ins->vex_wlp = *codes++;
	    break;

	case 0270:
	    ins->rex |= REX_V;
	    ins->drexdst = 0;
	    ins->vex_cm = *codes++;
	    ins->vex_wlp = *codes++;
	    break;

	case4(0274):
            length++;
            break;

	case4(0300):
            break;

        case 0310:
	    if (bits == 64)
		return -1;
            length += (bits != 16) && !has_prefix(ins, PPS_ASIZE, P_A16);
            break;

        case 0311:
            length += (bits != 32) && !has_prefix(ins, PPS_ASIZE, P_A32);
            break;

        case 0312:
            break;

        case 0313:
	    if (bits != 64 || has_prefix(ins, PPS_ASIZE, P_A16) ||
		has_prefix(ins, PPS_ASIZE, P_A32))
		return -1;
            break;

	case4(0314):
	    break;

        case 0320:
            length += (bits != 16);
            break;

        case 0321:
            length += (bits == 16);
            break;

        case 0322:
            break;

        case 0323:
            rex_mask &= ~REX_W;
            break;

        case 0324:
	    ins->rex |= REX_W;
            break;

	case 0325:
	    ins->rex |= REX_NH;
	    break;

        case 0330:
            codes++, length++;
            break;

        case 0331:
            break;

        case 0332:
        case 0333:
            length++;
            break;

	case 0334:
	    ins->rex |= REX_L;
	    break;

        case 0335:
	    break;

	case 0336:
	    if (!ins->prefixes[PPS_LREP])
		ins->prefixes[PPS_LREP] = P_REP;
	    break;

	case 0337:
	    if (!ins->prefixes[PPS_LREP])
		ins->prefixes[PPS_LREP] = P_REPNE;
	    break;

        case 0340:
            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;
            break;

	case 0341:
	    if (!ins->prefixes[PPS_WAIT])
		ins->prefixes[PPS_WAIT] = P_WAIT;
	    break;

	case4(0344):
            length++;
            break;

	case 0360:
	    break;

	case 0361:
	case 0362:
	case 0363:
	    length++;
	    break;

	case 0364:
	case 0365:
	    break;

        case 0366:
        case 0367:
	    length++;
	    break;

        case 0370:
        case 0371:
        case 0372:
            break;

        case 0373:
            length++;
            break;

	case4(0100):
	case4(0110):
	case4(0120):
	case4(0130):
	case4(0200):
	case4(0204):
	case4(0210):
	case4(0214):
	case4(0220):
	case4(0224):
	case4(0230):
	case4(0234):
	    {
                ea ea_data;
                int rfield;
		opflags_t rflags;
		struct operand *opy = &ins->oprs[op2];

                ea_data.rex = 0;           /* Ensure ea.REX is initially 0 */

		if (c <= 0177) {
		    /* pick rfield from operand b (opx) */
		    rflags = regflag(opx);
		    rfield = nasm_regvals[opx->basereg];
		} else {
		    rflags = 0;
		    rfield = c & 7;
		}
                if (!process_ea(opy, &ea_data, bits,
				ins->addr_size, rfield, rflags)) {
                    errfunc(ERR_NONFATAL, "invalid effective address");
                    return -1;
                } else {
		    ins->rex |= ea_data.rex;
                    length += ea_data.size;
                }
	    }
	    break;

	default:
	    errfunc(ERR_PANIC, "internal instruction table corrupt"
		    ": instruction code \\%o (0x%02X) given", c, c);
	    break;
	}
    }

    ins->rex &= rex_mask;

    if (ins->rex & REX_NH) {
	if (ins->rex & REX_H) {
	    errfunc(ERR_NONFATAL, "instruction cannot use high registers");
	    return -1;
	}
	ins->rex &= ~REX_P;	/* Don't force REX prefix due to high reg */
    }

    if (ins->rex & REX_V) {
	int bad32 = REX_R|REX_W|REX_X|REX_B;

	if (ins->rex & REX_H) {
	    errfunc(ERR_NONFATAL, "cannot use high register in vex instruction");
	    return -1;
	}
	switch (ins->vex_wlp & 030) {
	case 000:
	case 020:
	    ins->rex &= ~REX_W;
	    break;
	case 010:
	    ins->rex |= REX_W;
	    bad32 &= ~REX_W;
	    break;
	case 030:
	    /* Follow REX_W */
	    break;
	}

	if (bits != 64 && ((ins->rex & bad32) || ins->drexdst > 7)) {
	    errfunc(ERR_NONFATAL, "invalid operands in non-64-bit mode");
	    return -1;
	}
	if (ins->vex_cm != 1 || (ins->rex & (REX_W|REX_R|REX_B)))
	    length += 3;
	else
	    length += 2;
    } else if (ins->rex & REX_D) {
	if (ins->rex & REX_H) {
	    errfunc(ERR_NONFATAL, "cannot use high register in drex instruction");
	    return -1;
	}
	if (bits != 64 && ((ins->rex & (REX_R|REX_W|REX_X|REX_B)) ||
			   ins->drexdst > 7)) {
	    errfunc(ERR_NONFATAL, "invalid operands in non-64-bit mode");
	    return -1;
	}
	length++;
    } else if (ins->rex & REX_REAL) {
	if (ins->rex & REX_H) {
	    errfunc(ERR_NONFATAL, "cannot use high register in rex instruction");
	    return -1;
	} else if (bits == 64) {
	    length++;
	} else if ((ins->rex & REX_L) &&
		   !(ins->rex & (REX_P|REX_W|REX_X|REX_B)) &&
		   cpu >= IF_X86_64) {
	    /* LOCK-as-REX.R */
	    assert_no_prefix(ins, PPS_LREP);
	    length++;
	} else {
	    errfunc(ERR_NONFATAL, "invalid operands in non-64-bit mode");
	    return -1;
	}
    }

    return length;
}

#define EMIT_REX()							\
    if (!(ins->rex & (REX_D|REX_V)) && (ins->rex & REX_REAL) && (bits == 64)) { \
	ins->rex = (ins->rex & REX_REAL)|REX_P;				\
	out(offset, segment, &ins->rex, OUT_RAWDATA, 1, NO_SEG, NO_SEG); \
	ins->rex = 0;							\
	offset += 1; \
    }

static void gencode(int32_t segment, int64_t offset, int bits,
                    insn * ins, const struct itemplate *temp,
		    int64_t 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
    };
    uint8_t c;
    uint8_t bytes[4];
    int64_t size;
    int64_t data;
    int op1, op2;
    struct operand *opx;
    const uint8_t *codes = temp->code;
    uint8_t opex = 0;

    while (*codes) {
	c = *codes++;
	op1 = (c & 3) + ((opex & 1) << 2);
	op2 = ((c >> 3) & 3) + ((opex & 2) << 1);
	opx = &ins->oprs[op1];
	opex = 0;		/* For the next iteration */

        switch (c) {
        case 01:
        case 02:
        case 03:
	case 04:
	    EMIT_REX();
            out(offset, segment, codes, OUT_RAWDATA, c, NO_SEG, NO_SEG);
            codes += c;
            offset += c;
            break;

	case 05:
	case 06:
	case 07:
	    opex = c;
	    break;

	case4(010):
	    EMIT_REX();
            bytes[0] = *codes++ + (regval(opx) & 7);
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

	case4(014):
	    /* The test for BITS8 and SBYTE here is intended to avoid
	       warning on optimizer actions due to SBYTE, while still
	       warn on explicit BYTE directives.  Also warn, obviously,
	       if the optimizer isn't enabled. */
            if (((opx->type & BITS8) ||
		 !(opx->type & temp->opd[op1] & BYTENESS)) &&
		(opx->offset < -128 || opx->offset > 127)) {
                errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"signed byte value exceeds bounds");
	    }
            if (opx->segment != NO_SEG) {
                data = opx->offset;
                out(offset, segment, &data, OUT_ADDRESS, 1,
                    opx->segment, opx->wrt);
            } else {
                bytes[0] = opx->offset;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

	case4(020):
            if (opx->offset < -256 || opx->offset > 255) {
                errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"byte value exceeds bounds");
            }
            if (opx->segment != NO_SEG) {
                data = opx->offset;
                out(offset, segment, &data, OUT_ADDRESS, 1,
                    opx->segment, opx->wrt);
            } else {
                bytes[0] = opx->offset;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

	case4(024):
            if (opx->offset < 0 || opx->offset > 255)
                errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"unsigned byte value exceeds bounds");
            if (opx->segment != NO_SEG) {
                data = opx->offset;
                out(offset, segment, &data, OUT_ADDRESS, 1,
                    opx->segment, opx->wrt);
            } else {
                bytes[0] = opx->offset;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;

	case4(030):
            warn_overflow_opd(opx, 2);
            data = opx->offset;
            out(offset, segment, &data, OUT_ADDRESS, 2,
                opx->segment, opx->wrt);
            offset += 2;
            break;

	case4(034):
            if (opx->type & (BITS16 | BITS32))
                size = (opx->type & BITS16) ? 2 : 4;
            else
                size = (bits == 16) ? 2 : 4;
            warn_overflow_opd(opx, size);
            data = opx->offset;
            out(offset, segment, &data, OUT_ADDRESS, size,
                opx->segment, opx->wrt);
            offset += size;
            break;

	case4(040):
            warn_overflow_opd(opx, 4);
            data = opx->offset;
            out(offset, segment, &data, OUT_ADDRESS, 4,
                opx->segment, opx->wrt);
            offset += 4;
            break;

	case4(044):
            data = opx->offset;
            size = ins->addr_size >> 3;
            warn_overflow_opd(opx, size);
            out(offset, segment, &data, OUT_ADDRESS, size,
                opx->segment, opx->wrt);
            offset += size;
            break;

	case4(050):
            if (opx->segment != segment) {
                data = opx->offset;
                out(offset, segment, &data,
                    OUT_REL1ADR, insn_end - offset,
                    opx->segment, opx->wrt);
            } else {
                data = opx->offset - insn_end;
		if (data > 127 || data < -128)
		    errfunc(ERR_NONFATAL, "short jump is out of range");
                out(offset, segment, &data,
                    OUT_ADDRESS, 1, NO_SEG, NO_SEG);
            }
            offset += 1;
            break;

	case4(054):
            data = (int64_t)opx->offset;
            out(offset, segment, &data, OUT_ADDRESS, 8,
                opx->segment, opx->wrt);
            offset += 8;
            break;

	case4(060):
            if (opx->segment != segment) {
                data = opx->offset;
                out(offset, segment, &data,
                    OUT_REL2ADR, insn_end - offset,
                    opx->segment, opx->wrt);
            } else {
                data = opx->offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS, 2, NO_SEG, NO_SEG);
            }
            offset += 2;
            break;

	case4(064):
            if (opx->type & (BITS16 | BITS32 | BITS64))
                size = (opx->type & BITS16) ? 2 : 4;
            else
                size = (bits == 16) ? 2 : 4;
            if (opx->segment != segment) {
                data = opx->offset;
                out(offset, segment, &data,
		    size == 2 ? OUT_REL2ADR : OUT_REL4ADR,
		    insn_end - offset, opx->segment, opx->wrt);
            } else {
                data = opx->offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS, size, NO_SEG, NO_SEG);
            }
            offset += size;
            break;

	case4(070):
            if (opx->segment != segment) {
                data = opx->offset;
                out(offset, segment, &data,
                    OUT_REL4ADR, insn_end - offset,
                    opx->segment, opx->wrt);
            } else {
                data = opx->offset - insn_end;
                out(offset, segment, &data,
                    OUT_ADDRESS, 4, NO_SEG, NO_SEG);
            }
            offset += 4;
            break;

	case4(074):
            if (opx->segment == NO_SEG)
                errfunc(ERR_NONFATAL, "value referenced by FAR is not"
                        " relocatable");
	    data = 0;
            out(offset, segment, &data, OUT_ADDRESS, 2,
                outfmt->segbase(1 + opx->segment),
                opx->wrt);
            offset += 2;
            break;

	case4(0140):
            data = opx->offset;
            warn_overflow_opd(opx, 2);
            if (is_sbyte16(opx)) {
                bytes[0] = data;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
                offset++;
            } else {
                out(offset, segment, &data, OUT_ADDRESS, 2,
                    opx->segment, opx->wrt);
                offset += 2;
            }
            break;

	case4(0144):
	    EMIT_REX();
            bytes[0] = *codes++;
            if (is_sbyte16(opx))
                bytes[0] |= 2;  /* s-bit */
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset++;
            break;

	case4(0150):
            data = opx->offset;
            warn_overflow_opd(opx, 4);
            if (is_sbyte32(opx)) {
                bytes[0] = data;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
                offset++;
            } else {
                out(offset, segment, &data, OUT_ADDRESS, 4,
                    opx->segment, opx->wrt);
                offset += 4;
            }
            break;

	case4(0154):
	    EMIT_REX();
            bytes[0] = *codes++;
            if (is_sbyte32(opx))
                bytes[0] |= 2;  /* s-bit */
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset++;
            break;

	case4(0160):
	case4(0164):
	    break;

	case 0171:
	    bytes[0] =
		(ins->drexdst << 4) |
		(ins->rex & REX_OC ? 0x08 : 0) |
		(ins->rex & (REX_R|REX_X|REX_B));
	    ins->rex = 0;
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
	    offset++;
	    break;

	case 0172:
	    c = *codes++;
	    opx = &ins->oprs[c >> 3];
	    bytes[0] = nasm_regvals[opx->basereg] << 4;
	    opx = &ins->oprs[c & 7];
	    if (opx->segment != NO_SEG || opx->wrt != NO_SEG) {
		errfunc(ERR_NONFATAL,
			"non-absolute expression not permitted as argument %d",
			c & 7);
	    } else {
		if (opx->offset & ~15) {
		    errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			    "four-bit argument exceeds bounds");
		}
		bytes[0] |= opx->offset & 15;
	    }
	    out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
	    offset++;
	    break;

	case 0173:
	    c = *codes++;
	    opx = &ins->oprs[c >> 4];
	    bytes[0] = nasm_regvals[opx->basereg] << 4;
	    bytes[0] |= c & 15;
	    out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
	    offset++;
	    break;

	case 0174:
	    c = *codes++;
	    opx = &ins->oprs[c];
	    bytes[0] = nasm_regvals[opx->basereg] << 4;
	    out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
	    offset++;
	    break;

	case4(0250):
            data = opx->offset;
	    if (opx->wrt == NO_SEG && opx->segment == NO_SEG &&
		(int32_t)data != (int64_t)data) {
		errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"signed dword immediate exceeds bounds");
	    }
            if (is_sbyte32(opx)) {
                bytes[0] = data;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
                offset++;
            } else {
                out(offset, segment, &data, OUT_ADDRESS, 4,
                    opx->segment, opx->wrt);
                offset += 4;
            }
            break;

	case4(0254):
            data = opx->offset;
	    if (opx->wrt == NO_SEG && opx->segment == NO_SEG &&
		(int32_t)data != (int64_t)data) {
		errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"signed dword immediate exceeds bounds");
	    }
	    out(offset, segment, &data, OUT_ADDRESS, 4,
		opx->segment, opx->wrt);
	    offset += 4;
            break;

	case4(0260):
	case 0270:
	    codes += 2;
	    if (ins->vex_cm != 1 || (ins->rex & (REX_W|REX_X|REX_B))) {
		bytes[0] = (ins->vex_cm >> 6) ? 0x8f : 0xc4;
		bytes[1] = (ins->vex_cm & 31) | ((~ins->rex & 7) << 5);
		bytes[2] = ((ins->rex & REX_W) << (7-3)) |
		    ((~ins->drexdst & 15)<< 3) | (ins->vex_wlp & 07);
		out(offset, segment, &bytes, OUT_RAWDATA, 3, NO_SEG, NO_SEG);
		offset += 3;
	    } else {
		bytes[0] = 0xc5;
		bytes[1] = ((~ins->rex & REX_R) << (7-2)) |
		    ((~ins->drexdst & 15) << 3) | (ins->vex_wlp & 07);
		out(offset, segment, &bytes, OUT_RAWDATA, 2, NO_SEG, NO_SEG);
		offset += 2;
	    }
	    break;

	case4(0274):
	{
	    uint64_t uv, um;
	    int s;

	    if (ins->rex & REX_W)
		s = 64;
	    else if (ins->prefixes[PPS_OSIZE] == P_O16)
		s = 16;
	    else if (ins->prefixes[PPS_OSIZE] == P_O32)
		s = 32;
	    else
		s = bits;

	    um = (uint64_t)2 << (s-1);
	    uv = opx->offset;

	    if (uv > 127 && uv < (uint64_t)-128 &&
		(uv < um-128 || uv > um-1)) {
                errfunc(ERR_WARNING | ERR_PASS2 | ERR_WARN_NOV,
			"signed byte value exceeds bounds");
	    }
            if (opx->segment != NO_SEG) {
                data = uv;
                out(offset, segment, &data, OUT_ADDRESS, 1,
                    opx->segment, opx->wrt);
            } else {
                bytes[0] = uv;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG,
                    NO_SEG);
            }
            offset += 1;
            break;
	}

	case4(0300):
            break;

        case 0310:
            if (bits == 32 && !has_prefix(ins, PPS_ASIZE, P_A16)) {
                *bytes = 0x67;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0311:
            if (bits != 32 && !has_prefix(ins, PPS_ASIZE, P_A32)) {
                *bytes = 0x67;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
                offset += 1;
            } else
                offset += 0;
            break;

        case 0312:
            break;

        case 0313:
            ins->rex = 0;
            break;

	case4(0314):
	    break;

        case 0320:
            if (bits != 16) {
                *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:
        case 0323:
            break;

        case 0324:
            ins->rex |= REX_W;
            break;

	case 0325:
	    break;

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

        case 0331:
            break;

	case 0332:
        case 0333:
            *bytes = c - 0332 + 0xF2;
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset += 1;
            break;

        case 0334:
            if (ins->rex & REX_R) {
                *bytes = 0xF0;
                out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
                offset += 1;
            }
            ins->rex &= ~(REX_L|REX_R);
            break;

        case 0335:
	    break;

        case 0336:
        case 0337:
	    break;

        case 0340:
            if (ins->oprs[0].segment != NO_SEG)
                errfunc(ERR_PANIC, "non-constant BSS size in pass two");
            else {
                int64_t size = ins->oprs[0].offset;
                if (size > 0)
                    out(offset, segment, NULL,
                        OUT_RESERVE, size, NO_SEG, NO_SEG);
                offset += size;
            }
            break;

	case 0341:
	    break;

        case 0344:
        case 0345:
	    bytes[0] = c & 1;
            switch (ins->oprs[0].basereg) {
            case R_CS:
                bytes[0] += 0x0E;
                break;
            case R_DS:
                bytes[0] += 0x1E;
                break;
            case R_ES:
                bytes[0] += 0x06;
                break;
            case R_SS:
                bytes[0] += 0x16;
                break;
            default:
                errfunc(ERR_PANIC,
                        "bizarre 8086 segment register received");
            }
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset++;
            break;

        case 0346:
        case 0347:
	    bytes[0] = c & 1;
            switch (ins->oprs[0].basereg) {
            case R_FS:
                bytes[0] += 0xA0;
                break;
            case R_GS:
                bytes[0] += 0xA8;
                break;
            default:
                errfunc(ERR_PANIC,
                        "bizarre 386 segment register received");
            }
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset++;
            break;

	case 0360:
	    break;

	case 0361:
	    bytes[0] = 0x66;
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset += 1;
	    break;

	case 0362:
	case 0363:
	    bytes[0] = c - 0362 + 0xf2;
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset += 1;
	    break;

	case 0364:
	case 0365:
	    break;

        case 0366:
	case 0367:
            *bytes = c - 0366 + 0x66;
            out(offset, segment, bytes, OUT_RAWDATA, 1, NO_SEG, NO_SEG);
            offset += 1;
            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;

	case4(0100):
	case4(0110):
	case4(0120):
	case4(0130):
	case4(0200):
	case4(0204):
	case4(0210):
	case4(0214):
	case4(0220):
	case4(0224):
	case4(0230):
	case4(0234):
	    {
                ea ea_data;
                int rfield;
		opflags_t rflags;
                uint8_t *p;
                int32_t s;
		enum out_type type;
		struct operand *opy = &ins->oprs[op2];

                if (c <= 0177) {
		    /* pick rfield from operand b (opx) */
		    rflags = regflag(opx);
                    rfield = nasm_regvals[opx->basereg];
		} else {
		    /* rfield is constant */
		    rflags = 0;
                    rfield = c & 7;
		}

                if (!process_ea(opy, &ea_data, bits, ins->addr_size,
				rfield, rflags)) {
                    errfunc(ERR_NONFATAL, "invalid effective address");
                }


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

		/* DREX suffixes come between the SIB and the displacement */
		if (ins->rex & REX_D) {
		    *p++ = (ins->drexdst << 4) |
			   (ins->rex & REX_OC ? 0x08 : 0) |
			   (ins->rex & (REX_R|REX_X|REX_B));
		    ins->rex = 0;
		}

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

                /*
                 * Make sure the address gets the right offset in case
                 * the line breaks in the .lst file (BR 1197827)
                 */
                offset += s;
                s = 0;

                switch (ea_data.bytes) {
                case 0:
                    break;
                case 1:
                case 2:
                case 4:
                case 8:
                    data = opy->offset;
                    s += ea_data.bytes;
		    if (ea_data.rip) {
			if (opy->segment == segment) {
			    data -= insn_end;
                            if (overflow_signed(data, ea_data.bytes))
                                warn_overflow(ERR_PASS2, ea_data.bytes);
			    out(offset, segment, &data, OUT_ADDRESS,
				ea_data.bytes, NO_SEG, NO_SEG);
			} else {
                            /* overflow check in output/linker? */
			    out(offset, segment, &data,	OUT_REL4ADR,
				insn_end - offset, opy->segment, opy->wrt);
			}
		    } else {
                        if (overflow_general(opy->offset, ins->addr_size >> 3) ||
                            signed_bits(opy->offset, ins->addr_size) !=
                            signed_bits(opy->offset, ea_data.bytes * 8))
                            warn_overflow(ERR_PASS2, ea_data.bytes);

			type = OUT_ADDRESS;
			out(offset, segment, &data, OUT_ADDRESS,
			    ea_data.bytes, opy->segment, opy->wrt);
		    }
                    break;
                default:
                    /* Impossible! */
                    errfunc(ERR_PANIC,
                            "Invalid amount of bytes (%d) for offset?!",
                            ea_data.bytes);
                    break;
                }
                offset += s;
	    }
	    break;

	default:
	    errfunc(ERR_PANIC, "internal instruction table corrupt"
		    ": instruction code \\%o (0x%02X) given", c, c);
	    break;
        }
    }
}

static opflags_t regflag(const operand * o)
{
    if (!is_register(o->basereg))
        errfunc(ERR_PANIC, "invalid operand passed to regflag()");
    return nasm_reg_flags[o->basereg];
}

static int32_t regval(const operand * o)
{
    if (!is_register(o->basereg))
        errfunc(ERR_PANIC, "invalid operand passed to regval()");
    return nasm_regvals[o->basereg];
}

static int op_rexflags(const operand * o, int mask)
{
    opflags_t flags;
    int val;

    if (!is_register(o->basereg))
        errfunc(ERR_PANIC, "invalid operand passed to op_rexflags()");

    flags = nasm_reg_flags[o->basereg];
    val = nasm_regvals[o->basereg];

    return rexflags(val, flags, mask);
}

static int rexflags(int val, opflags_t flags, int mask)
{
    int rex = 0;

    if (val >= 8)
	rex |= REX_B|REX_X|REX_R;
    if (flags & BITS64)
	rex |= REX_W;
    if (!(REG_HIGH & ~flags))	/* AH, CH, DH, BH */
	rex |= REX_H;
    else if (!(REG8 & ~flags) && val >= 4) /* SPL, BPL, SIL, DIL */
	rex |= REX_P;

    return rex & mask;
}

static enum match_result find_match(const struct itemplate **tempp,
				    insn *instruction,
				    int32_t segment, int64_t offset, int bits)
{
    const struct itemplate *temp;
    enum match_result m, merr;
    opflags_t xsizeflags[MAX_OPERANDS];
    bool opsizemissing = false;
    int i;

    for (i = 0; i < instruction->operands; i++)
	xsizeflags[i] = instruction->oprs[i].type & SIZE_MASK;

    merr = MERR_INVALOP;

    for (temp = nasm_instructions[instruction->opcode];
	 temp->opcode != I_none; temp++) {
	m = matches(temp, instruction, bits);
	if (m == MOK_JUMP) {
	    if (jmp_match(segment, offset, bits, instruction, temp->code))
		m = MOK_GOOD;
	    else
		m = MERR_INVALOP;
	} else if (m == MERR_OPSIZEMISSING &&
		   (temp->flags & IF_SMASK) != IF_SX) {
	    /*
	     * Missing operand size and a candidate for fuzzy matching...
	     */
	    for (i = 0; i < temp->operands; i++) {
		if ((temp->opd[i] & SAME_AS) == 0)
		    xsizeflags[i] |= temp->opd[i] & SIZE_MASK;
	    }
	    opsizemissing = true;
	}
	if (m > merr)
	    merr = m;
	if (merr == MOK_GOOD)
	    goto done;
    }

    /* No match, but see if we can get a fuzzy operand size match... */
    if (!opsizemissing)
	goto done;

    for (i = 0; i < instruction->operands; i++) {
	/*
	 * We ignore extrinsic operand sizes on registers, so we should
	 * never try to fuzzy-match on them.  This also resolves the case
	 * when we have e.g. "xmmrm128" in two different positions.
	 */
	if (is_class(REGISTER, instruction->oprs[i].type))
	    continue;

	/* This tests if xsizeflags[i] has more than one bit set */
	if ((xsizeflags[i] & (xsizeflags[i]-1)))
	    goto done;		/* No luck */

	instruction->oprs[i].type |= xsizeflags[i]; /* Set the size */
    }

    /* Try matching again... */
    for (temp = nasm_instructions[instruction->opcode];
	 temp->opcode != I_none; temp++) {
	m = matches(temp, instruction, bits);
	if (m == MOK_JUMP) {
	    if (jmp_match(segment, offset, bits, instruction, temp->code))
		m = MOK_GOOD;
	    else
		m = MERR_INVALOP;
	}
	if (m > merr)
	    merr = m;
	if (merr == MOK_GOOD)
	    goto done;
    }

done:
    *tempp = temp;
    return merr;
}

static enum match_result matches(const struct itemplate *itemp,
                                 insn *instruction, int bits)
{
    int i, size[MAX_OPERANDS], asize, oprs;
    bool opsizemissing = false;

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

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

    /*
     * 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 MERR_INVALOP;

    /*
     * Process size flags
     */
    switch (itemp->flags & IF_SMASK) {
    case IF_SB:
        asize = BITS8;
        break;
    case IF_SW:
        asize = BITS16;
        break;
    case IF_SD:
        asize = BITS32;
        break;
    case IF_SQ:
        asize = BITS64;
        break;
    case IF_SO:
        asize = BITS128;
        break;
    case IF_SY:
        asize = BITS256;
        break;
    case IF_SZ:
        switch (bits) {
        case 16:
            asize = BITS16;
            break;
        case 32:
            asize = BITS32;
            break;
        case 64:
            asize = BITS64;
            break;
        default:
            asize = 0;
            break;
        }
        break;
    default:
        asize = 0;
        break;
    }

    if (itemp->flags & IF_ARMASK) {
        /* S- flags only apply to a specific operand */
        i = ((itemp->flags & IF_ARMASK) >> IF_ARSHFT) - 1;
        memset(size, 0, sizeof size);
        size[i] = asize;
    } else {
        /* S- flags apply to all operands */
        for (i = 0; i < MAX_OPERANDS; i++)
            size[i] = asize;
    }

    /*
     * Check that the operand flags all match up,
     * it's a bit tricky so lets be verbose:
     *
     * 1) Find out the size of operand. If instruction
     *    doesn't have one specified -- we're trying to
     *    guess it either from template (IF_S* flag) or
     *    from code bits.
     *
     * 2) If template operand (i) has SAME_AS flag [used for registers only]
     *    (ie the same operand as was specified somewhere in template, and
     *    this referred operand index is being achieved via ~SAME_AS)
     *    we are to be sure that both registers (in template and instruction)
     *    do exactly match.
     *
     * 3) If template operand do not match the instruction OR
     *    template has an operand size specified AND this size differ
     *    from which instruction has (perhaps we got it from code bits)
     *    we are:
     *      a)  Check that only size of instruction and operand is differ
     *          other characteristics do match
     *      b)  Perhaps it's a register specified in instruction so
     *          for such a case we just mark that operand as "size
     *          missing" and this will turn on fuzzy operand size
     *          logic facility (handled by a caller)
     */
    for (i = 0; i < itemp->operands; i++) {
        opflags_t type = instruction->oprs[i].type;
        if (!(type & SIZE_MASK))
            type |= size[i];

        if (itemp->opd[i] & SAME_AS) {
            int j = itemp->opd[i] & ~SAME_AS;
            if (type != instruction->oprs[j].type ||
                instruction->oprs[i].basereg != instruction->oprs[j].basereg)
                return MERR_INVALOP;
        } else if (itemp->opd[i] & ~type ||
            ((itemp->opd[i] & SIZE_MASK) &&
             ((itemp->opd[i] ^ type) & SIZE_MASK))) {
            if ((itemp->opd[i] & ~type & ~SIZE_MASK) || (type & SIZE_MASK)) {
                return MERR_INVALOP;
            } else if (!is_class(REGISTER, type)) {
                /*
                 * Note: we don't honor extrinsic operand sizes for registers,
                 * so "missing operand size" for a register should be
                 * considered a wildcard match rather than an error.
                 */
                opsizemissing = true;
            }
        }
    }

    if (opsizemissing)
        return MERR_OPSIZEMISSING;

    /*
     * Check operand sizes
     */
    if (itemp->flags & (IF_SM | IF_SM2)) {
        oprs = (itemp->flags & IF_SM2 ? 2 : itemp->operands);
        for (i = 0; i < oprs; i++) {
            asize = itemp->opd[i] & SIZE_MASK;
            if (asize) {
                for (i = 0; i < oprs; i++)
                    size[i] = 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]))
            return MERR_OPSIZEMISMATCH;
    }

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

    /*
     * Verify the appropriate long mode flag.
     */
    if ((itemp->flags & (bits == 64 ? IF_NOLONG : IF_LONG)))
        return MERR_BADMODE;

    /*
     * Check if special handling needed for Jumps
     */
    if ((itemp->code[0] & 0374) == 0370)
        return MOK_JUMP;

    return MOK_GOOD;
}

static ea *process_ea(operand * input, ea * output, int bits,
		      int addrbits, int rfield, opflags_t rflags)
{
    bool forw_ref = !!(input->opflags & OPFLAG_UNKNOWN);

    output->rip = false;

    /* REX flags for the rfield operand */
    output->rex |= rexflags(rfield, rflags, REX_R|REX_P|REX_W|REX_H);

    if (is_class(REGISTER, input->type)) {  /* register direct */
        int i;
	opflags_t f;

        if (!is_register(input->basereg))
            return NULL;
	f = regflag(input);
        i = nasm_regvals[input->basereg];

	if (REG_EA & ~f)
	    return NULL;	/* Invalid EA register */

	output->rex |= op_rexflags(input, REX_B|REX_P|REX_W|REX_H);

        output->sib_present = false;             /* no SIB necessary */
        output->bytes = 0;  /* no offset necessary either */
        output->modrm = 0xC0 | ((rfield & 7) << 3) | (i & 7);
    } else {                    /* it's a memory reference */
        if (input->basereg == -1
            && (input->indexreg == -1 || input->scale == 0)) {
            /* it's a pure offset */

            if (bits == 64 && ((input->type & IP_REL) == IP_REL) &&
                input->segment == NO_SEG) {
                nasm_error(ERR_WARNING | ERR_PASS1, "absolute address can not be RIP-relative");
                input->type &= ~IP_REL;
                input->type |= MEMORY;
            }

            if (input->eaflags & EAF_BYTEOFFS ||
                (input->eaflags & EAF_WORDOFFS &&
                 input->disp_size != (addrbits != 16 ? 32 : 16))) {
                nasm_error(ERR_WARNING | ERR_PASS1, "displacement size ignored on absolute address");
            }

            if (bits == 64 && (~input->type & IP_REL)) {
              int scale, index, base;
              output->sib_present = true;
              scale = 0;
              index = 4;
              base = 5;
              output->sib = (scale << 6) | (index << 3) | base;
              output->bytes = 4;
              output->modrm = 4 | ((rfield & 7) << 3);
	      output->rip = false;
            } else {
              output->sib_present = false;
              output->bytes = (addrbits != 16 ? 4 : 2);
              output->modrm = (addrbits != 16 ? 5 : 6) | ((rfield & 7) << 3);
	      output->rip = bits == 64;
            }
        } else {                /* it's an indirection */
            int i = input->indexreg, b = input->basereg, s = input->scale;
            int32_t seg = input->segment;
            int hb = input->hintbase, ht = input->hinttype;
            int t, it, bt;	 	/* register numbers */
	    opflags_t x, ix, bx;	/* register flags */

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

            if (is_register(i)) {
                it = nasm_regvals[i];
		ix = nasm_reg_flags[i];
	    } else {
                it = -1;
		ix = 0;
	    }

	    if (is_register(b)) {
                bt = nasm_regvals[b];
		bx = nasm_reg_flags[b];
	    } else {
                bt = -1;
		bx = 0;
	    }

	    /* check for a 32/64-bit memory reference... */
	    if ((ix|bx) & (BITS32|BITS64)) {
                /* it must be a 32/64-bit memory reference. Firstly we have
                 * to check that all registers involved are type E/Rxx. */
		int32_t sok = BITS32|BITS64, o = input->offset;

                if (it != -1) {
		    if (!(REG64 & ~ix) || !(REG32 & ~ix))
			sok &= ix;
		    else
			return NULL;
		}

		if (bt != -1) {
		    if (REG_GPR & ~bx)
			return NULL; /* Invalid register */
		    if (~sok & bx & SIZE_MASK)
			return NULL; /* Invalid size */
		    sok &= bx;
		}

                /* While we're here, ensure the user didn't specify
		   WORD or QWORD. */
                if (input->disp_size == 16 || input->disp_size == 64)
		    return NULL;

		if (addrbits == 16 ||
		    (addrbits == 32 && !(sok & BITS32)) ||
		    (addrbits == 64 && !(sok & BITS64)))
		    return NULL;

                /* now reorganize base/index */
                if (s == 1 && bt != it && bt != -1 && it != -1 &&
                    ((hb == b && ht == EAH_NOTBASE)
                     || (hb == i && ht == EAH_MAKEBASE))) {
		    /* swap if hints say so */
                    t = bt, bt = it, it = t;
		    x = bx, bx = ix, ix = x;
		}
                if (bt == it)     /* convert EAX+2*EAX to 3*EAX */
                    bt = -1, bx = 0, s++;
                if (bt == -1 && s == 1 && !(hb == it && ht == EAH_NOTBASE)) {
		    /* make single reg base, unless hint */
                    bt = it, bx = ix, it = -1, ix = 0;
		}
                if (((s == 2 && it != REG_NUM_ESP
                      && !(input->eaflags & EAF_TIMESTWO)) || s == 3
                     || s == 5 || s == 9) && bt == -1)
                    bt = it, bx = ix, s--; /* convert 3*EAX to EAX+2*EAX */
                if (it == -1 && (bt & 7) != REG_NUM_ESP
                    && (input->eaflags & EAF_TIMESTWO))
                    it = bt, ix = bx, bt = -1, bx = 0, s = 1;
                /* convert [NOSPLIT EAX] to sib format with 0x0 displacement */
                if (s == 1 && it == REG_NUM_ESP) {
		    /* swap ESP into base if scale is 1 */
                    t = it, it = bt, bt = t;
		    x = ix, ix = bx, bx = x;
		}
                if (it == REG_NUM_ESP
                    || (s != 1 && s != 2 && s != 4 && s != 8 && it != -1))
                    return NULL;        /* wrong, for various reasons */

		output->rex |= rexflags(it, ix, REX_X);
		output->rex |= rexflags(bt, bx, REX_B);

                if (it == -1 && (bt & 7) != REG_NUM_ESP) {
		    /* no SIB needed */
                    int mod, rm;

                    if (bt == -1) {
                        rm = 5;
                        mod = 0;
                    } else {
                        rm = (bt & 7);
                        if (rm != REG_NUM_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 = (bt == -1 || mod == 2 ? 4 : mod);
                    output->modrm = (mod << 6) | ((rfield & 7) << 3) | rm;
                } else {
		    /* we need a SIB */
                    int mod, scale, index, base;

                    if (it == -1)
                        index = 4, s = 1;
                    else
                        index = (it & 7);

                    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 (bt == -1) {
                        base = 5;
                        mod = 0;
                    } else {
                        base = (bt & 7);
                        if (base != REG_NUM_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 =  (bt == -1 || mod == 2 ? 4 : mod);
                    output->modrm = (mod << 6) | ((rfield & 7) << 3) | 4;
                    output->sib = (scale << 6) | (index << 3) | base;
                }
            } else {            /* it's 16-bit */
                int mod, rm;
                int16_t o = input->offset;

                /* check for 64-bit long mode */
                if (addrbits == 64)
                    return NULL;

                /* 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/QWORD */
                if (input->disp_size == 32 || input->disp_size == 64)
                    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 & 7) << 3) | rm;
            }
        }
    }

    output->size = 1 + output->sib_present + output->bytes;
    return output;
}

static void add_asp(insn *ins, int addrbits)
{
    int j, valid;
    int defdisp;

    valid = (addrbits == 64) ? 64|32 : 32|16;

    switch (ins->prefixes[PPS_ASIZE]) {
    case P_A16:
	valid &= 16;
	break;
    case P_A32:
	valid &= 32;
	break;
    case P_A64:
	valid &= 64;
	break;
    case P_ASP:
	valid &= (addrbits == 32) ? 16 : 32;
	break;
    default:
	break;
    }

    for (j = 0; j < ins->operands; j++) {
	if (is_class(MEMORY, ins->oprs[j].type)) {
	    opflags_t i, b;

	    /* Verify as Register */
            if (!is_register(ins->oprs[j].indexreg))
		i = 0;
	    else
		i = nasm_reg_flags[ins->oprs[j].indexreg];

	    /* Verify as Register */
            if (!is_register(ins->oprs[j].basereg))
		b = 0;
	    else
		b = nasm_reg_flags[ins->oprs[j].basereg];

	    if (ins->oprs[j].scale == 0)
		i = 0;

	    if (!i && !b) {
		int ds = ins->oprs[j].disp_size;
		if ((addrbits != 64 && ds > 8) ||
		    (addrbits == 64 && ds == 16))
		    valid &= ds;
	    } else {
		if (!(REG16 & ~b))
		    valid &= 16;
		if (!(REG32 & ~b))
		    valid &= 32;
		if (!(REG64 & ~b))
		    valid &= 64;

		if (!(REG16 & ~i))
		    valid &= 16;
		if (!(REG32 & ~i))
		    valid &= 32;
		if (!(REG64 & ~i))
		    valid &= 64;
	    }
	}
    }

    if (valid & addrbits) {
	ins->addr_size = addrbits;
    } else if (valid & ((addrbits == 32) ? 16 : 32)) {
	/* Add an address size prefix */
	enum prefixes pref = (addrbits == 32) ? P_A16 : P_A32;
	ins->prefixes[PPS_ASIZE] = pref;
	ins->addr_size = (addrbits == 32) ? 16 : 32;
    } else {
	/* Impossible... */
	errfunc(ERR_NONFATAL, "impossible combination of address sizes");
	ins->addr_size = addrbits; /* Error recovery */
    }

    defdisp = ins->addr_size == 16 ? 16 : 32;

    for (j = 0; j < ins->operands; j++) {
	if (!(MEM_OFFS & ~ins->oprs[j].type) &&
	    (ins->oprs[j].disp_size ? ins->oprs[j].disp_size : defdisp)
	    != ins->addr_size) {
	    /* mem_offs sizes must match the address size; if not,
	       strip the MEM_OFFS bit and match only EA instructions */
	    ins->oprs[j].type &= ~(MEM_OFFS & ~MEMORY);
	}
    }
}