diff --git a/disasm.c b/disasm.c
index d2d9d914..665e3d28 100644
--- a/disasm.c
+++ b/disasm.c
@@ -25,19 +25,56 @@ extern struct itemplate **itable[];
  * Flags that go into the `segment' field of `insn' structures
  * during disassembly.
  */
-#define SEG_RELATIVE 1
-#define SEG_32BIT 2
-#define SEG_RMREG 4
-#define SEG_DISP8 8
-#define SEG_DISP16 16
-#define SEG_DISP32 32
-#define SEG_NODISP 64
-#define SEG_SIGNED 128
+#define SEG_RELATIVE	  1
+#define SEG_32BIT	  2
+#define SEG_RMREG	  4
+#define SEG_DISP8	  8
+#define SEG_DISP16	 16
+#define SEG_DISP32	 32
+#define SEG_NODISP	 64
+#define SEG_SIGNED	128
+#define SEG_64BIT	256
+
+/*
+ * REX flags
+ */
+#define REX_P		0x40	/* REX prefix present */
+#define REX_W		0x08	/* 64-bit operand size */
+#define REX_R		0x04	/* ModRM reg extension */
+#define REX_X		0x02	/* SIB index extension */
+#define REX_B		0x01	/* ModRM r/m extension */
 
-static int whichreg(int32_t regflags, int regval)
-{
 #include "regdis.c"
 
+#define getu8(x) (*(uint8_t *)(x))
+#if defined(__i386__) || defined(__x86_64__)
+/* Littleendian CPU which can handle unaligned references */
+#define getu16(x) (*(uint16_t *)(x))
+#define getu32(x) (*(uint32_t *)(x))
+#define getu64(x) (*(uint64_t *)(x))
+#else
+static uint16_t getu16(uint8_t *data)
+{
+    return (uint16_t)data[0] + ((uint16_t)data[1] << 8);
+}
+static uint32_t getu32(uint8_t *data)
+{
+    return (uint32_t)getu16(data) + ((uint32_t)getu16(data+2) << 16);
+}
+static uint64_t getu64(uint8_t *data)
+{
+    return (uint64_t)getu32(data) + ((uint64_t)getu32(data+4) << 32);
+}
+#endif
+
+#define gets8(x) ((int8_t)getu8(x))
+#define gets16(x) ((int16_t)getu16(x))
+#define gets32(x) ((int32_t)getu32(x))
+#define gets64(x) ((int64_t)getu64(x))
+
+/* Important: regval must already have been adjusted for rex extensions */
+static int whichreg(int32_t regflags, int regval, int rex)
+{
     if (!(REG_AL & ~regflags))
         return R_AL;
     if (!(REG_AX & ~regflags))
@@ -62,36 +99,46 @@ static int whichreg(int32_t regflags, int regval)
         return (regval == 1) ? R_CS : 0;
     if (!(REG_DESS & ~regflags))
         return (regval == 0 || regval == 2
-                || regval == 3 ? sreg[regval] : 0);
+                || regval == 3 ? rd_sreg[regval] : 0);
     if (!(REG_FSGS & ~regflags))
-        return (regval == 4 || regval == 5 ? sreg[regval] : 0);
+        return (regval == 4 || regval == 5 ? rd_sreg[regval] : 0);
     if (!(REG_SEG67 & ~regflags))
-        return (regval == 6 || regval == 7 ? sreg[regval] : 0);
+        return (regval == 6 || regval == 7 ? rd_sreg[regval] : 0);
 
-    /* All the entries below look up regval in an 8-entry array */
-    if (regval < 0 || regval > 7)
+    /* All the entries below look up regval in an 16-entry array */
+    if (regval < 0 || regval > 15)
         return 0;
 
-    if (!((REGMEM | BITS8) & ~regflags))
-        return reg8[regval];
+    if (!(rex & REX_P) && regval > 7)
+	return 0;		/* Internal error! */
+
+    if (!((REGMEM | BITS8) & ~regflags)) {
+	if (rex & REX_P)
+	    return rd_reg8_rex[regval];
+	else
+	    return rd_reg8[regval];
+    }
     if (!((REGMEM | BITS16) & ~regflags))
-        return reg16[regval];
+        return rd_reg16[regval];
     if (!((REGMEM | BITS32) & ~regflags))
-        return reg32[regval];
+        return rd_reg32[regval];
     if (!(REG_SREG & ~regflags))
-        return sreg[regval];
+        return rd_sreg[regval & 7]; /* Ignore REX */
     if (!(REG_CREG & ~regflags))
-        return creg[regval];
+        return rd_creg[regval];
     if (!(REG_DREG & ~regflags))
-        return dreg[regval];
-    if (!(REG_TREG & ~regflags))
-        return treg[regval];
+        return rd_dreg[regval];
+    if (!(REG_TREG & ~regflags)) {
+	if (rex & REX_P)
+	    return 0;		/* TR registers are ill-defined with rex */
+        return rd_treg[regval];
+    }
     if (!(FPUREG & ~regflags))
-        return fpureg[regval];
+        return rd_fpureg[regval & 7]; /* Ignore REX */
     if (!(MMXREG & ~regflags))
-        return mmxreg[regval];
+        return rd_mmxreg[regval & 7]; /* Ignore REX */
     if (!(XMMREG & ~regflags))
-        return xmmreg[regval];
+        return rd_xmmreg[regval];
 
     return 0;
 }
@@ -109,7 +156,7 @@ static const char *whichcond(int condval)
  * Process an effective address (ModRM) specification.
  */
 static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
-                            int segsize, operand * op)
+		      int segsize, operand * op, int rex)
 {
     int mod, rm, scale, index, base;
 
@@ -175,7 +222,7 @@ static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
             break;
         case 1:
             op->segment |= SEG_DISP8;
-            op->offset = (char)*data++;
+            op->offset = (int8_t)*data++;
             break;
         case 2:
             op->segment |= SEG_DISP16;
@@ -189,40 +236,35 @@ static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
          * Once again, <mod> specifies displacement size (this time
          * none, byte or *dword*), while <rm> specifies the base
          * register. Again, [EBP] is missing, replaced by a pure
-         * disp32 (this time that's mod=0,rm=*5*). However, rm=4
+         * disp32 (this time that's mod=0,rm=*5*) in 32-bit mode,
+	 * and RIP-relative addressing in 64-bit mode.
+	 *
+	 * However, rm=4
          * indicates not a single base register, but instead the
          * presence of a SIB byte...
          */
+	int a64 = asize == 64;
+
         op->indexreg = -1;
-        switch (rm) {
-        case 0:
-            op->basereg = R_EAX;
-            break;
-        case 1:
-            op->basereg = R_ECX;
-            break;
-        case 2:
-            op->basereg = R_EDX;
-            break;
-        case 3:
-            op->basereg = R_EBX;
-            break;
-        case 5:
-            op->basereg = R_EBP;
-            break;
-        case 6:
-            op->basereg = R_ESI;
-            break;
-        case 7:
-            op->basereg = R_EDI;
-            break;
-        }
+
+	if (a64)
+	    op->basereg = rd_reg64[rm | ((rex & REX_B) ? 8 : 0)];
+	else
+	    op->basereg = rd_reg32[rm | ((rex & REX_B) ? 8 : 0)];
+
         if (rm == 5 && mod == 0) {
-            op->basereg = -1;
-            if (segsize != 32)
-                op->addr_size = 32;
-            mod = 2;            /* fake disp32 */
+	    if (segsize == 64) {
+		op->basereg = R_RIP;
+		op->segment |= SEG_RELATIVE;
+		mod = 2;	/* fake disp32 */
+	    } else {
+		op->basereg = -1;
+		if (segsize != 32)
+		    op->addr_size = 32;
+		mod = 2;            /* fake disp32 */
+	    }
         }
+
         if (rm == 4) {          /* process SIB */
             scale = (*data >> 6) & 03;
             index = (*data >> 3) & 07;
@@ -230,78 +272,36 @@ static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
             data++;
 
             op->scale = 1 << scale;
-            switch (index) {
-            case 0:
-                op->indexreg = R_EAX;
-                break;
-            case 1:
-                op->indexreg = R_ECX;
-                break;
-            case 2:
-                op->indexreg = R_EDX;
-                break;
-            case 3:
-                op->indexreg = R_EBX;
-                break;
-            case 4:
-                op->indexreg = -1;
-                break;
-            case 5:
-                op->indexreg = R_EBP;
-                break;
-            case 6:
-                op->indexreg = R_ESI;
-                break;
-            case 7:
-                op->indexreg = R_EDI;
-                break;
-            }
 
-            switch (base) {
-            case 0:
-                op->basereg = R_EAX;
-                break;
-            case 1:
-                op->basereg = R_ECX;
-                break;
-            case 2:
-                op->basereg = R_EDX;
-                break;
-            case 3:
-                op->basereg = R_EBX;
-                break;
-            case 4:
-                op->basereg = R_ESP;
-                break;
-            case 6:
-                op->basereg = R_ESI;
-                break;
-            case 7:
-                op->basereg = R_EDI;
-                break;
-            case 5:
-                if (mod == 0) {
-                    mod = 2;
-                    op->basereg = -1;
-                } else
-                    op->basereg = R_EBP;
-                break;
-            }
+	    if (index == 4)
+		op->indexreg = -1; /* ESP/RSP/R12 cannot be an index */
+	    else if (a64)
+		op->indexreg = rd_reg64[index | ((rex & REX_X) ? 8 : 0)];
+	    else
+		op->indexreg = rd_reg64[index | ((rex & REX_X) ? 8 : 0)];
+
+	    if (base == 5 && mod == 0) {
+		op->basereg = -1;
+		mod = 2;	/* Fake disp32 */
+	    } else if (a64)
+		op->basereg = rd_reg64[base | ((rex & REX_B) ? 8 : 0)];
+	    else
+		op->basereg = rd_reg32[base | ((rex & REX_B) ? 8 : 0)];
         }
+
         switch (mod) {
         case 0:
             op->segment |= SEG_NODISP;
             break;
         case 1:
             op->segment |= SEG_DISP8;
-            op->offset = (char)*data++;
+            op->offset = gets8(data);
+	    data++;
             break;
         case 2:
             op->segment |= SEG_DISP32;
-            op->offset = *data++;
-            op->offset |= ((unsigned)*data++) << 8;
-            op->offset |= ((int32_t)*data++) << 16;
-            op->offset |= ((int32_t)*data++) << 24;
+            op->offset = getu32(data);
+	    data += 4;
             break;
         }
         return data;
@@ -313,12 +313,23 @@ static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
  * stream in data. Return the number of bytes matched if so.
  */
 static int matches(struct itemplate *t, uint8_t *data, int asize,
-                   int osize, int segsize, int rep, insn * ins)
+                   int osize, int segsize, int rep, insn * ins,
+		   int rex, int *rexout)
 {
     uint8_t *r = (uint8_t *)(t->code);
     uint8_t *origdata = data;
     int a_used = FALSE, o_used = FALSE;
     int drep = 0;
+    
+    *rexout = rex;
+
+    if (segsize == 64) {
+	if (t->flags & IF_NOLONG)
+	    return FALSE;
+    } else {
+	if (t->flags & IF_X64)
+	    return FALSE;
+    }
 
     if (rep == 0xF2)
         drep = P_REPNE;
@@ -402,7 +413,7 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
             if (*data++)
                 return FALSE;
         if (c >= 014 && c <= 016) {
-            ins->oprs[c - 014].offset = (char)*data++;
+            ins->oprs[c - 014].offset = (int8_t)*data++;
             ins->oprs[c - 014].segment |= SEG_SIGNED;
         }
         if (c >= 020 && c <= 022)
@@ -410,55 +421,60 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
         if (c >= 024 && c <= 026)
             ins->oprs[c - 024].offset = *data++;
         if (c >= 030 && c <= 032) {
-            ins->oprs[c - 030].offset = *data++;
-            ins->oprs[c - 030].offset |= (((unsigned)*data++) << 8);
+            ins->oprs[c - 030].offset = getu16(data);
+	    data += 2;
         }
         if (c >= 034 && c <= 036) {
-            ins->oprs[c - 034].offset = *data++;
-            ins->oprs[c - 034].offset |= (((unsigned)*data++) << 8);
-            if (osize == 32) {
-                ins->oprs[c - 034].offset |= (((int32_t)*data++) << 16);
-                ins->oprs[c - 034].offset |= (((int32_t)*data++) << 24);
-            }
+	    if (osize == 32) {
+		ins->oprs[c - 034].offset = getu32(data);
+		data += 4;
+	    } else {
+		ins->oprs[c - 034].offset = getu16(data);
+		data += 2;
+	    }
             if (segsize != asize)
                 ins->oprs[c - 034].addr_size = asize;
         }
         if (c >= 040 && c <= 042) {
-            ins->oprs[c - 040].offset = *data++;
-            ins->oprs[c - 040].offset |= (((unsigned)*data++) << 8);
-            ins->oprs[c - 040].offset |= (((int32_t)*data++) << 16);
-            ins->oprs[c - 040].offset |= (((int32_t)*data++) << 24);
+            ins->oprs[c - 040].offset = getu32(data);
+	    data += 4;
         }
         if (c >= 044 && c <= 046) {
-            ins->oprs[c - 044].offset = *data++;
-            ins->oprs[c - 044].offset |= (((unsigned)*data++) << 8);
-            if (asize == 32) {
-                ins->oprs[c - 044].offset |= (((int32_t)*data++) << 16);
-                ins->oprs[c - 044].offset |= (((int32_t)*data++) << 24);
-            }
+	    /* hpa: should this be gets32/gets16? */
+	    if (asize == 32) {
+		ins->oprs[c - 044].offset = getu32(data);
+		data += 4;
+	    } else {
+		ins->oprs[c - 044].offset = getu16(data);
+		data += 2;
+	    }
             if (segsize != asize)
                 ins->oprs[c - 044].addr_size = asize;
         }
         if (c >= 050 && c <= 052) {
-            ins->oprs[c - 050].offset = (char)*data++;
+            ins->oprs[c - 050].offset = gets8(data++);
             ins->oprs[c - 050].segment |= SEG_RELATIVE;
         }
+	if (c >= 054 && c <= 056) {
+	    ins->oprs[c - 054].offset = getu64(data);
+	    data += 8;
+	}
         if (c >= 060 && c <= 062) {
-            ins->oprs[c - 060].offset = *data++;
-            ins->oprs[c - 060].offset |= (((unsigned)*data++) << 8);
+            ins->oprs[c - 060].offset = gets16(data);
+	    data += 2;
             ins->oprs[c - 060].segment |= SEG_RELATIVE;
             ins->oprs[c - 060].segment &= ~SEG_32BIT;
         }
         if (c >= 064 && c <= 066) {
-            ins->oprs[c - 064].offset = *data++;
-            ins->oprs[c - 064].offset |= (((unsigned)*data++) << 8);
-            if (osize == 32) {
-                ins->oprs[c - 064].offset |= (((int32_t)*data++) << 16);
-                ins->oprs[c - 064].offset |= (((int32_t)*data++) << 24);
+	    if (osize == 32) {
+		ins->oprs[c - 064].offset = getu32(data);
+		data += 4;
                 ins->oprs[c - 064].segment |= SEG_32BIT;
-            } else
+	    } else {
+		ins->oprs[c - 064].offset = getu16(data);
+		data += 2;
                 ins->oprs[c - 064].segment &= ~SEG_32BIT;
-            ins->oprs[c - 064].segment |= SEG_RELATIVE;
+	    }	
             if (segsize != osize) {
                 ins->oprs[c - 064].type =
                     (ins->oprs[c - 064].type & NON_SIZE)
@@ -466,10 +482,8 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
             }
         }
         if (c >= 070 && c <= 072) {
-            ins->oprs[c - 070].offset = *data++;
-            ins->oprs[c - 070].offset |= (((unsigned)*data++) << 8);
-            ins->oprs[c - 070].offset |= (((int32_t)*data++) << 16);
-            ins->oprs[c - 070].offset |= (((int32_t)*data++) << 24);
+            ins->oprs[c - 070].offset = getu32(data);
+	    data += 4;
             ins->oprs[c - 070].segment |= SEG_32BIT | SEG_RELATIVE;
         }
         if (c >= 0100 && c < 0130) {
@@ -477,24 +491,22 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
             ins->oprs[c & 07].basereg = (modrm >> 3) & 07;
             ins->oprs[c & 07].segment |= SEG_RMREG;
             data = do_ea(data, modrm, asize, segsize,
-                         &ins->oprs[(c >> 3) & 07]);
+                         &ins->oprs[(c >> 3) & 07], rex);
         }
         if (c >= 0130 && c <= 0132) {
-            ins->oprs[c - 0130].offset = *data++;
-            ins->oprs[c - 0130].offset |= (((unsigned)*data++) << 8);
+            ins->oprs[c - 0130].offset = getu16(data);
+	    data += 2;
         }
         if (c >= 0140 && c <= 0142) {
-            ins->oprs[c - 0140].offset = *data++;
-            ins->oprs[c - 0140].offset |= (((unsigned)*data++) << 8);
-            ins->oprs[c - 0140].offset |= (((int32_t)*data++) << 16);
-            ins->oprs[c - 0140].offset |= (((int32_t)*data++) << 24);
+	    ins->oprs[c - 0140].offset = getu32(data);
+	    data += 4;
         }
         if (c >= 0200 && c <= 0277) {
             int modrm = *data++;
             if (((modrm >> 3) & 07) != (c & 07))
                 return FALSE;   /* spare field doesn't match up */
             data = do_ea(data, modrm, asize, segsize,
-                         &ins->oprs[(c >> 3) & 07]);
+                         &ins->oprs[(c >> 3) & 07], rex);
         }
         if (c >= 0300 && c <= 0302) {
             if (asize)
@@ -504,7 +516,7 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
             a_used = TRUE;
         }
         if (c == 0310) {
-            if (asize == 32)
+            if (asize != 16)
                 return FALSE;
             else
                 a_used = TRUE;
@@ -522,7 +534,7 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
                 a_used = TRUE;
         }
         if (c == 0320) {
-            if (osize == 32)
+            if (osize != 16)
                 return FALSE;
             else
                 o_used = TRUE;
@@ -534,11 +546,19 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
                 o_used = TRUE;
         }
         if (c == 0322) {
-            if (osize != segsize)
+            if (osize != (segsize == 16) ? 16 : 32)
                 return FALSE;
             else
                 o_used = TRUE;
         }
+	if (c == 0323) {
+	    rex |= REX_W;	/* 64-bit only instruction */
+	    osize = 64;
+	}
+	if (c == 0324) {
+	    if (!(rex & REX_P))
+		return FALSE;
+	}
         if (c == 0330) {
             int t = *r++, d = *data++;
             if (d < t || d > t + 15)
@@ -568,10 +588,15 @@ static int matches(struct itemplate *t, uint8_t *data, int asize,
     if (drep)
         ins->prefixes[ins->nprefix++] = drep;
     if (!a_used && asize != segsize)
-        ins->prefixes[ins->nprefix++] = (asize == 16 ? P_A16 : P_A32);
-    if (!o_used && osize != segsize)
-        ins->prefixes[ins->nprefix++] = (osize == 16 ? P_O16 : P_O32);
+        ins->prefixes[ins->nprefix++] = asize == 16 ? P_A16 : P_A32;
+    if (!o_used && osize == ((segsize == 16) ? 32 : 16)) {
+	fprintf(stderr, "osize = %d, segsize = %d\n", osize, segsize);
+        ins->prefixes[ins->nprefix++] = osize == 16 ? P_O16 : P_O32;
+    }
 
+    /* Fix: check for redundant REX prefixes */
+
+    *rexout = rex;
     return data - origdata;
 }
 
@@ -581,7 +606,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
     struct itemplate **p, **best_p;
     int length, best_length = 0;
     char *segover;
-    int rep, lock, asize, osize, i, slen, colon;
+    int rep, lock, asize, osize, i, slen, colon, rex, rexout, best_rex;
     uint8_t *origdata;
     int works;
     insn tmp_ins, ins;
@@ -590,7 +615,9 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
     /*
      * Scan for prefixes.
      */
-    asize = osize = segsize;
+    asize = segsize;
+    osize = (segsize == 64) ? 32 : segsize;
+    rex = 0;
     segover = NULL;
     rep = lock = 0;
     origdata = data;
@@ -599,46 +626,47 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
             rep = *data++;
         else if (*data == 0xF0)
             lock = *data++;
-        else if (*data == 0x2E || *data == 0x36 || *data == 0x3E ||
-                 *data == 0x26 || *data == 0x64 || *data == 0x65) {
-            switch (*data++) {
-            case 0x2E:
-                segover = "cs";
-                break;
-            case 0x36:
-                segover = "ss";
-                break;
-            case 0x3E:
-                segover = "ds";
-                break;
-            case 0x26:
-                segover = "es";
-                break;
-            case 0x64:
-                segover = "fs";
-                break;
-            case 0x65:
-                segover = "gs";
-                break;
-            }
-        } else if (*data == 0x66)
-            osize = 48 - segsize, data++;
-        else if (*data == 0x67)
-            asize = 48 - segsize, data++;
-        else
+        else if (*data == 0x2E)
+	    segover = "cs", data++;
+	else if (*data == 0x36)
+	    segover = "ss", data++;
+	else if (*data == 0x3E)
+	    segover = "ds", data++;
+	else if (*data == 0x26)
+	    segover = "es", data++;
+	else if (*data == 0x64)
+	    segover = "fs", data++;
+	else if (*data == 0x65)
+	    segover = "gs", data++;
+	else if (*data == 0x66) {
+	    if (segsize != 64)	/* 66 prefix is ignored in 64-bit mode */
+		osize = 48 - segsize;
+	    data++;
+	} else if (*data == 0x67) {
+	    asize = (segsize == 32) ? 16 : 32;
+	    data++;
+	} else if (segsize == 64 && (*data & 0xf0) == REX_P) {
+	    rex = *data++;
+	    if (rex & REX_W)
+		osize = 64;
+	    break;		/* REX is always the last prefix */
+	} else {
             break;
+	}
     }
 
     tmp_ins.oprs[0].segment = tmp_ins.oprs[1].segment =
         tmp_ins.oprs[2].segment =
         tmp_ins.oprs[0].addr_size = tmp_ins.oprs[1].addr_size =
-        tmp_ins.oprs[2].addr_size = (segsize == 16 ? 0 : SEG_32BIT);
+        tmp_ins.oprs[2].addr_size = (segsize == 64 ? SEG_64BIT :
+				     segsize == 32 ? SEG_32BIT : 0);
     tmp_ins.condition = -1;
-    best = ~0UL;                /* Worst possible */
+    best = -1;			/* Worst possible */
     best_p = NULL;
+    best_rex = 0;
     for (p = itable[*data]; *p; p++) {
         if ((length = matches(*p, data, asize, osize,
-                              segsize, rep, &tmp_ins))) {
+                              segsize, rep, &tmp_ins, rex, &rexout))) {
             works = TRUE;
             /*
              * Final check to make sure the types of r/m match up.
@@ -656,7 +684,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
                        ((((*p)->opd[i] & (REGISTER | FPUREG)) ||
                          (tmp_ins.oprs[i].segment & SEG_RMREG)) &&
                         !whichreg((*p)->opd[i],
-                                  tmp_ins.oprs[i].basereg))) {
+                                  tmp_ins.oprs[i].basereg, rexout))) {
                     works = FALSE;
                     break;
                 }
@@ -670,6 +698,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
                     best_p = p;
                     best_length = length;
                     ins = tmp_ins;
+		    best_rex = rexout;
                 }
             }
         }
@@ -681,6 +710,9 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
     /* Pick the best match */
     p = best_p;
     length = best_length;
+    rex = best_rex;
+    if (best_rex & REX_W)
+	osize = 64;
 
     slen = 0;
 
@@ -739,8 +771,8 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
             /*
              * sort out wraparound
              */
-            if (!(ins.oprs[i].segment & SEG_32BIT))
-                ins.oprs[i].offset &= 0xFFFF;
+            if (!(ins.oprs[i].segment & (SEG_32BIT|SEG_64BIT)))
+		ins.oprs[i].offset &= 0xffff;
             /*
              * add sync marker, if autosync is on
              */
@@ -756,7 +788,7 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
         if (((*p)->opd[i] & (REGISTER | FPUREG)) ||
             (ins.oprs[i].segment & SEG_RMREG)) {
             ins.oprs[i].basereg = whichreg((*p)->opd[i],
-                                           ins.oprs[i].basereg);
+                                           ins.oprs[i].basereg, rex);
             if ((*p)->opd[i] & TO)
                 slen += snprintf(output + slen, outbufsize - slen, "to ");
             slen += snprintf(output + slen, outbufsize - slen, "%s",
@@ -781,6 +813,9 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
             } else if ((*p)->opd[i] & BITS32) {
                 slen +=
                     snprintf(output + slen, outbufsize - slen, "dword ");
+            } else if ((*p)->opd[i] & BITS64) {
+                slen +=
+                    snprintf(output + slen, outbufsize - slen, "qword ");
             } else if ((*p)->opd[i] & NEAR) {
                 slen +=
                     snprintf(output + slen, outbufsize - slen, "near ");
@@ -825,9 +860,10 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
             output[slen++] = '[';
             if (ins.oprs[i].addr_size)
                 slen += snprintf(output + slen, outbufsize - slen, "%s",
-                                 (ins.oprs[i].addr_size == 32 ? "dword " :
-                                  ins.oprs[i].addr_size ==
-                                  16 ? "word " : ""));
+                                 (ins.oprs[i].addr_size == 64 ? "qword " :
+				  ins.oprs[i].addr_size == 32 ? "dword " :
+                                  ins.oprs[i].addr_size == 16 ? "word " :
+				  ""));
             if (segover) {
                 slen +=
                     snprintf(output + slen, outbufsize - slen, "%s:",
@@ -853,26 +889,39 @@ int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
                 started = TRUE;
             }
             if (ins.oprs[i].segment & SEG_DISP8) {
-                int sign = '+';
-                if (ins.oprs[i].offset & 0x80) {
-                    ins.oprs[i].offset = -(char)ins.oprs[i].offset;
-                    sign = '-';
-                }
+		int minus = 0;
+		int8_t offset = ins.oprs[i].offset;
+		if (offset < 0) {
+		    minus = 1;
+		    offset = -offset;
+		}
                 slen +=
-                    snprintf(output + slen, outbufsize - slen, "%c0x%"PRIx64"",
-                             sign, ins.oprs[i].offset);
+                    snprintf(output + slen, outbufsize - slen, "%s0x%"PRIx8"",
+			     minus ? "-" : "+", offset);
             } else if (ins.oprs[i].segment & SEG_DISP16) {
-                if (started)
-                    output[slen++] = '+';
+		int minus = 0;
+		int16_t offset = ins.oprs[i].offset;
+		if (offset < 0) {
+		    minus = 1;
+		    offset = -offset;
+		}
                 slen +=
-                    snprintf(output + slen, outbufsize - slen, "0x%"PRIx64"",
-                             ins.oprs[i].offset);
+                    snprintf(output + slen, outbufsize - slen, "%s0x%"PRIx16"",
+			     minus ? "-" : started ? "+" : "", offset);
             } else if (ins.oprs[i].segment & SEG_DISP32) {
-                if (started)
-                    output[slen++] = '+';
-                slen +=
-                    snprintf(output + slen, outbufsize - slen, "0x%"PRIx64"",
-                             ins.oprs[i].offset);
+		    char *prefix = "";
+		    int32_t offset = ins.oprs[i].offset;
+		    if (ins.oprs[i].basereg == R_RIP) {
+			prefix = ":";
+		    } else if (offset < 0) {
+			offset = -offset;
+			prefix = "-";
+		    } else {
+			prefix = started ? "+" : "";
+		    }
+		    slen +=
+			snprintf(output + slen, outbufsize - slen,
+				 "%s0x%"PRIx32"", prefix, offset);
             }
             output[slen++] = ']';
         } else {
diff --git a/nasm.h b/nasm.h
index e860eadc..92f678ec 100644
--- a/nasm.h
+++ b/nasm.h
@@ -223,7 +223,7 @@ enum {                          /* token types, other than chars */
 
 typedef struct {
     int32_t segment;
-    int32_t offset;
+    int64_t offset;
     int known;
 } loc_t;
 
diff --git a/regs.pl b/regs.pl
index e96029a2..c412c660 100755
--- a/regs.pl
+++ b/regs.pl
@@ -118,7 +118,7 @@ if ( $fmt eq 'h' ) {
     # Output regdis.c
     print "/* automatically generated from $file - do not edit */\n";
     foreach $class ( sort(keys(%disclass)) ) {
-	printf "static const int %-8s[] = {", $class;
+	printf "static const int rd_%-8s[] = {", $class;
 	@foo = @{$disclass{$class}};
 	@bar = ();
 	for ( $i = 0 ; $i < scalar(@foo) ; $i++ ) {