/* this version is derived from the flowchart in the preliminary P400
   release notes */

static inline ea_t ea64v (unsigned short inst, ea_t earp) {

  ea_t ea;                                       /* full seg/word va */
  unsigned short ea_s;                           /* eff address segno */
  unsigned short ea_w;                           /* eff address wordno */
  unsigned short br;
  unsigned short i;
  unsigned short x;
  unsigned short xok;
  unsigned short a;
  unsigned short ixy;
  unsigned short m;
  unsigned short rph,rpl;


  i = inst & 0100000;           /* indirect is bit 1 (left/MS bit) */
  x = ((inst & 036000) != 032000) ? (inst & 040000) : 0;

  /* earp is usually = RPH/RPL in the register file, except for the
     case of an XEC instruction; in that case, earp points to 1
     after the instruction being executed */

  rph = earp >> 16;
  rpl = earp & 0xFFFF;
  //TRACE(T_EAV, " inst=%o, rph=%o, rpl=%o\n", inst, rph, rpl);

  ea_s = rph;

  /* first check for long, 2-word, V-mode memory references.  About
     half of V-mode references are in this form */

  if ((inst & 01740) == 01400) {
    a = iget16(RP);
    INCRP;
    TRACE(T_EAV, " 2-word format, a=%o\n", a);
    ixy = (i >> 13) | (x >> 13) | ((inst & 020) >> 4);
    xok = (inst & 036000) != 032000;        /* true if indexing is okay */

    br = (inst & 3);
    eap = &gv.brp[br];

#ifndef NOTRACE
    int opcode;

    opcode = ((inst & 036000) != 032000) ? ((inst & 036000) >> 4) : ((inst & 076000) >> 4);
    opcode |= ((inst >> 2) & 3);         /* opcode extension */
    TRACE(T_EAV, " new opcode=%#05o, br=%d, ixy=%d, xok=%d\n", opcode, br, ixy, xok);
#endif

    ea_s = getcrs16(PBH+br*2) | (ea_s & RINGMASK16);
    ea_w = getcrs16(PBL+br*2) + a;

    if (xok)
      if (ixy == 2 || ixy == 6)
        ea_w += getcrs16(X);
      else if (ixy == 1 || ixy == 4)
        ea_w += getcrs16(Y);

#if 0
      /* if this is a PB% address, use RPBR instead if it's in range

         NOTE: this has been disabled, because gcov showed it only
         occurred 0.5% of the time */

      if (br == 0 && ((((ea_s & 0x8FFF) << 16) | (ea_w & 0xFC00)) == gv.brp[RPBR].vpn))
        eap = &gv.brp[RPBR];
#endif

    if (ixy >= 3) {
      ea = MAKEVA(ea_s, ea_w);
      TRACE(T_EAV, " Long indirect, ea=%o/%o, ea_s=%o, ea_w=%o\n", ea>>16, ea&0xFFFF, ea_s, ea_w);
      m = get16(ea);
      if (m & 0x8000)
        fault(POINTERFAULT, m, ea);
      ea_s = m | (ea_s & RINGMASK16);
      ea_w = get16(INCVA(ea,1));
      TRACE(T_EAV, " After indirect, ea_s=%o, ea_w=%o\n", ea_s, ea_w);

      /* when passing stack variables, callee references will be
         SB%+20,*, which may still be in the same page.  Don't switch to
         UNBR if the new ea is still in the current page */

      if ((((ea_s & 0x8FFF) << 16) | (ea_w & 0xFC00)) != (eap->vpn & 0x0FFFFFFF))
        eap = &gv.brp[UNBR];

      if (xok)
        if (ixy == 7) {
          TRACE(T_EAV, " Postindex, old ea_w=%o, X='%o/%d\n", ea_w, getcrs16(X), getcrs16s(X));
          ea_w += getcrs16(X);
        } else if (ixy == 5) {
          TRACE(T_EAV, " Postindex, old ea_w=%o, Y='%o/%d\n", ea_w, getcrs16(Y), getcrs16s(Y));
          ea_w += getcrs16(Y);
        }
    }
    return MAKEVA(ea_s, ea_w);
  }

  /* now check for direct short-form - the 2nd-most frequent case */

  if ((inst & 0101000) == 0) {
    ea_w = (inst & 0777);
    if (x) {
      TRACE(T_EAV, " Postindex, old ea_w=%o, X='%o/%d\n", ea_w, getcrs16(X), getcrs16s(X));
      ea_w += getcrs16(X);
      TRACE(T_EAV, " Postindex, new ea_w=%o\n", ea_w);
    }
    if (inst & 0400) {
      TRACE(T_EAV, " Short LB relative, LB=%o/%o\n", getcrs16(LBH), getcrs16(LBL));
      eap = &gv.brp[LBBR];
      ea_s = getcrs16(LBH) | (ea_s & RINGMASK16);
      ea_w += getcrs16(LBL);
      return MAKEVA(ea_s, ea_w);
    }
    if (ea_w >= gv.livereglim) {
      eap = &gv.brp[SBBR];
      ea_s = getcrs16(SBH) | (ea_s & RINGMASK16);
      ea_w += getcrs16(SBL);
      TRACE(T_EAV, " Short SB relative, SB=%o/%o\n", getcrs16(SBH), getcrs16(SBL));
      return MAKEVA(ea_s, ea_w);
    }
    TRACE(T_EAV, " Live register '%o\n", ea_w);
    return 0x80000000 | (rph << 16) | ea_w;
  }

  /* here for short, PC-relative instructions:
     - if bit 7 set, it's PC relative
     - if bit 7 clear, it's sector 0 (or register)
     - instruction may be indirect or not
     - optionally, may be postindexed by X
  */

  if (inst & 001000) {               /* sector bit 7 set? */
    ea_w = rpl + (((short) (inst << 7)) >> 7);   /* yes, sign extend D */
    TRACE(T_EAV, " PC relative, P=%o, new ea_w=%o\n", rpl, ea_w);
    eap = &gv.brp[RPBR];

  } else {
#if DBG
    if (!i)
      fatal ("ea64v: i not set?");
#endif
    eap = &gv.brp[S0BR];
    ea_w = (inst & 0777);                        /* sector 0 */
    TRACE(T_EAV, " Sector 0, new ea_w=%o\n", ea_w);
    if (ea_w < 0100 && x) {                      /* preindex by X */
      TRACE(T_EAV, " Preindex, ea_w=%o, X='%o/%d\n", ea_w, getcrs16(X), getcrs16s(X));
      ea_w += getcrs16(X);
      TRACE(T_EAV, " Preindex, new ea_w=%o\n", ea_w);
      x = 0;
    }
  }

  if (i) {
    if (ea_w >= gv.livereglim) {
      TRACE(T_EAV, " Indirect, ea_s=%o, ea_w=%o\n", ea_s, ea_w);
      ea_w = get16(MAKEVA(ea_s, ea_w));
    } else {
      TRACE(T_EAV, " Indirect through live register '%o\n", ea_w);
      ea_w = get16trap(ea_w);
    }
    TRACE(T_EAV, " After indirect, new ea_w=%o\n", ea_w);
  }

  if (x) {
    TRACE(T_EAV, " Postindex, old ea_w=%o, X='%o/%d\n", ea_w, getcrs16(X), getcrs16s(X));
    ea_w += getcrs16(X);
    TRACE(T_EAV, " Postindex, new ea_w=%o\n", ea_w);
  }

  /* if ea_w is within RP's brp cache page, set eap to match;
     otherwise, use PB's cache page */

  if (ea_w >= gv.livereglim) {
    if (((ea_w ^ RPL) & 0xFC00) == 0)
      eap = &gv.brp[RPBR];          /* occurs 80% */
    else
      eap = &gv.brp[PBBR];          /* occurs 20% */
    return MAKEVA(ea_s, ea_w);
  }

  TRACE(T_EAV, " Live register '%o\n", ea_w);
  return 0x80000000 | (rph << 16) | ea_w;
}