x86: use fixed-width type for codep and friends

This first of all removes a dependency on bfd_byte and unsigned char
being the same types. It further eliminates the need to mask by 0xff
when fetching values (which wasn't done fully consistently anyway),
improving code legibility.

While there, where possible add const.
diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 07fcf32..398be8b 100644
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -120,8 +120,8 @@
 
 struct dis_private {
   /* Points to first byte not fetched.  */
-  bfd_byte *max_fetched;
-  bfd_byte the_buffer[MAX_MNEM_SIZE];
+  uint8_t *max_fetched;
+  uint8_t the_buffer[MAX_MNEM_SIZE];
   bfd_vma insn_start;
   int orig_sizeflag;
 };
@@ -133,7 +133,7 @@
   mode_64bit
 };
 
-static const char *prefix_name (enum address_mode, int, int);
+static const char *prefix_name (enum address_mode, uint8_t, int);
 
 enum x86_64_isa
 {
@@ -149,9 +149,9 @@
   int prefixes;
 
   /* REX prefix the current instruction.  See below.  */
-  unsigned char rex;
+  uint8_t rex;
   /* Bits of REX we've already used.  */
-  unsigned char rex_used;
+  uint8_t rex_used;
 
   bool need_modrm;
   bool need_vex;
@@ -168,10 +168,10 @@
   char obuf[MAX_OPERAND_BUFFER_SIZE];
   char *obufp;
   char *mnemonicendp;
-  unsigned char *start_codep;
-  unsigned char *insn_codep;
-  unsigned char *codep;
-  unsigned char *end_codep;
+  const uint8_t *start_codep;
+  uint8_t *insn_codep;
+  uint8_t *codep;
+  const uint8_t *end_codep;
   signed char last_lock_prefix;
   signed char last_repz_prefix;
   signed char last_repnz_prefix;
@@ -186,7 +186,7 @@
 #define MAX_CODE_LENGTH 15
   /* We can up to 14 ins->prefixes since the maximum instruction length is
      15bytes.  */
-  unsigned char all_prefixes[MAX_CODE_LENGTH - 1];
+  uint8_t all_prefixes[MAX_CODE_LENGTH - 1];
   disassemble_info *info;
 
   struct
@@ -288,7 +288,7 @@
    to ADDR (exclusive) are valid.  Returns true for success, false
    on error.  */
 static bool
-fetch_code (struct disassemble_info *info, bfd_byte *until)
+fetch_code (struct disassemble_info *info, uint8_t *until)
 {
   int status = -1;
   struct dis_private *priv = info->private_data;
@@ -8833,7 +8833,8 @@
 }
 ckprefix (instr_info *ins)
 {
-  int newrex, i, length;
+  int i, length;
+  uint8_t newrex;
 
   i = 0;
   length = 0;
@@ -8843,7 +8844,7 @@
       if (!fetch_code (ins->info, ins->codep + 1))
 	return ckp_fetch_error;
       newrex = 0;
-      switch (*ins->codep & 0xff)
+      switch (*ins->codep)
 	{
 	/* REX prefixes family.  */
 	case 0x40:
@@ -8863,7 +8864,7 @@
 	case 0x4e:
 	case 0x4f:
 	  if (ins->address_mode == mode_64bit)
-	    newrex = *ins->codep & 0xff;
+	    newrex = *ins->codep;
 	  else
 	    return ckp_okay;
 	  ins->last_rex_prefix = i;
@@ -8943,8 +8944,8 @@
       /* Rex is ignored when followed by another prefix.  */
       if (ins->rex)
 	return ckp_bogus;
-      if ((*ins->codep & 0xff) != FWAIT_OPCODE)
-	ins->all_prefixes[i++] = *ins->codep & 0xff;
+      if (*ins->codep != FWAIT_OPCODE)
+	ins->all_prefixes[i++] = *ins->codep;
       ins->rex = newrex;
       ins->codep++;
       length++;
@@ -8956,7 +8957,7 @@
    prefix byte.  */
 
 static const char *
-prefix_name (enum address_mode mode, int pref, int sizeflag)
+prefix_name (enum address_mode mode, uint8_t pref, int sizeflag)
 {
   static const char *rexes [16] =
     {
@@ -9175,7 +9176,7 @@
     case USE_3BYTE_TABLE:
       if (!fetch_code (ins->info, ins->codep + 2))
 	return &err_opcode;
-      vindex = *ins->codep++ & 0xff;
+      vindex = *ins->codep++;
       dp = &three_byte_table[dp->op[1].bytemode][vindex];
       ins->end_codep = ins->codep;
       if (!fetch_modrm (ins))
@@ -9282,7 +9283,7 @@
 	}
       ins->need_vex = true;
       ins->codep++;
-      vindex = *ins->codep++ & 0xff;
+      vindex = *ins->codep++;
       dp = &xop_table[vex_table_index][vindex];
 
       ins->end_codep = ins->codep;
@@ -9347,7 +9348,7 @@
 	}
       ins->need_vex = true;
       ins->codep++;
-      vindex = *ins->codep++ & 0xff;
+      vindex = *ins->codep++;
       dp = &vex_table[vex_table_index][vindex];
       ins->end_codep = ins->codep;
       /* There is no MODRM byte for VEX0F 77.  */
@@ -9382,7 +9383,7 @@
 	}
       ins->need_vex = true;
       ins->codep++;
-      vindex = *ins->codep++ & 0xff;
+      vindex = *ins->codep++;
       dp = &vex_table[dp->op[1].bytemode][vindex];
       ins->end_codep = ins->codep;
       /* There is no MODRM byte for VEX 77.  */
@@ -9474,7 +9475,7 @@
 
       ins->need_vex = true;
       ins->codep++;
-      vindex = *ins->codep++ & 0xff;
+      vindex = *ins->codep++;
       dp = &evex_table[vex_table_index][vindex];
       ins->end_codep = ins->codep;
       if (!fetch_modrm (ins))
@@ -9821,11 +9822,10 @@
       goto out;
     }
 
-  ins.two_source_ops = ((*ins.codep & 0xff) == 0x62
-			|| (*ins.codep & 0xff) == 0xc8);
+  ins.two_source_ops = (*ins.codep == 0x62 || *ins.codep == 0xc8);
 
   if ((ins.prefixes & PREFIX_FWAIT)
-      && ((*ins.codep & 0xff) < 0xd8 || (*ins.codep & 0xff) > 0xdf))
+      && (*ins.codep < 0xd8 || *ins.codep > 0xdf))
     {
       /* Handle ins.prefixes before fwait.  */
       for (i = 0; i < ins.fwait_prefix && ins.all_prefixes[i];
@@ -9838,22 +9838,22 @@
       goto out;
     }
 
-  if ((*ins.codep & 0xff) == 0x0f)
+  if (*ins.codep == 0x0f)
     {
       unsigned char threebyte;
 
       ins.codep++;
       if (!fetch_code (info, ins.codep + 1))
 	goto fetch_error_out;
-      threebyte = *ins.codep & 0xff;
+      threebyte = *ins.codep;
       dp = &dis386_twobyte[threebyte];
       ins.need_modrm = twobyte_has_modrm[threebyte];
       ins.codep++;
     }
   else
     {
-      dp = &dis386[*ins.codep & 0xff];
-      ins.need_modrm = onebyte_has_modrm[*ins.codep & 0xff];
+      dp = &dis386[*ins.codep];
+      ins.need_modrm = onebyte_has_modrm[*ins.codep];
       ins.codep++;
     }
 
@@ -10553,9 +10553,7 @@
 dofloat (instr_info *ins, int sizeflag)
 {
   const struct dis386 *dp;
-  unsigned char floatop;
-
-  floatop = ins->codep[-1] & 0xff;
+  unsigned char floatop = ins->codep[-1];
 
   if (ins->modrm.mod != 3)
     {
@@ -10576,7 +10574,7 @@
       putop (ins, fgrps[dp->op[0].bytemode][ins->modrm.rm], sizeflag);
 
       /* Instruction fnstsw is only one with strange arg.  */
-      if (floatop == 0xdf && (ins->codep[-1] & 0xff) == 0xe0)
+      if (floatop == 0xdf && ins->codep[-1] == 0xe0)
 	strcpy (ins->op_out[0], att_names16[0] + ins->intel_syntax);
     }
   else
@@ -11749,7 +11747,7 @@
 {
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  *res = (((bfd_vma) *ins->codep++ & 0xff) ^ 0x80) - 0x80;
+  *res = ((bfd_vma) *ins->codep++ ^ 0x80) - 0x80;
   return true;
 }
 
@@ -11758,8 +11756,8 @@
 {
   if (!fetch_code (ins->info, ins->codep + 2))
     return false;
-  *res = (bfd_vma) *ins->codep++ & 0xff;
-  *res |= ((bfd_vma) *ins->codep++ & 0xff) << 8;
+  *res = *ins->codep++;
+  *res |= (bfd_vma) *ins->codep++ << 8;
   return true;
 }
 
@@ -11777,10 +11775,10 @@
 {
   if (!fetch_code (ins->info, ins->codep + 4))
     return false;
-  *res = *ins->codep++ & (bfd_vma) 0xff;
-  *res |= (*ins->codep++ & (bfd_vma) 0xff) << 8;
-  *res |= (*ins->codep++ & (bfd_vma) 0xff) << 16;
-  *res |= (*ins->codep++ & (bfd_vma) 0xff) << 24;
+  *res = *ins->codep++;
+  *res |= (bfd_vma) *ins->codep++ << 8;
+  *res |= (bfd_vma) *ins->codep++ << 16;
+  *res |= (bfd_vma) *ins->codep++ << 24;
   return true;
 }
 
@@ -11803,14 +11801,14 @@
 
   if (!fetch_code (ins->info, ins->codep + 8))
     return false;
-  a = *ins->codep++ & 0xff;
-  a |= (*ins->codep++ & 0xff) << 8;
-  a |= (*ins->codep++ & 0xff) << 16;
-  a |= (*ins->codep++ & 0xffu) << 24;
-  b = *ins->codep++ & 0xff;
-  b |= (*ins->codep++ & 0xff) << 8;
-  b |= (*ins->codep++ & 0xff) << 16;
-  b |= (*ins->codep++ & 0xffu) << 24;
+  a = *ins->codep++;
+  a |= (unsigned int) *ins->codep++ << 8;
+  a |= (unsigned int) *ins->codep++ << 16;
+  a |= (unsigned int) *ins->codep++ << 24;
+  b = *ins->codep++;
+  b |= (unsigned int) *ins->codep++ << 8;
+  b |= (unsigned int) *ins->codep++ << 16;
+  b |= (unsigned int) *ins->codep++ << 24;
   *res = a + ((uint64_t) b << 32);
   return true;
 }
@@ -12489,7 +12487,7 @@
     case b_mode:
       if (!fetch_code (ins->info, ins->codep + 1))
 	return false;
-      op = *ins->codep++ & 0xff;
+      op = *ins->codep++;
       break;
     case v_mode:
       USED_REX (REX_W);
@@ -12776,7 +12774,7 @@
 {
   if (ins->intel_syntax)
     {
-      switch (ins->codep[-1] & 0xff)
+      switch (ins->codep[-1])
 	{
 	case 0x6d:	/* insw/insl */
 	  intel_operand_size (ins, z_mode, sizeflag);
@@ -12802,7 +12800,7 @@
 {
   if (ins->intel_syntax)
     {
-      switch (ins->codep[-1] & 0xff)
+      switch (ins->codep[-1])
 	{
 	case 0x6f:	/* outsw/outsl */
 	  intel_operand_size (ins, z_mode, sizeflag);
@@ -13248,7 +13246,7 @@
      place where an 8-bit immediate would normally go.  ie. the last
      byte of the instruction.  */
   ins->obufp = ins->mnemonicendp;
-  mnemonic = Suffix3DNow[*ins->codep++ & 0xff];
+  mnemonic = Suffix3DNow[*ins->codep++];
   if (mnemonic)
     ins->obufp = stpcpy (ins->obufp, mnemonic);
   else
@@ -13313,7 +13311,7 @@
 
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  cmp_type = *ins->codep++ & 0xff;
+  cmp_type = *ins->codep++;
   if (cmp_type < ARRAY_SIZE (simd_cmp_op))
     {
       char suffix[3];
@@ -13763,7 +13761,7 @@
 
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  reg = *ins->codep++ & 0xff;
+  reg = *ins->codep++;
 
   if (bytemode != x_mode && bytemode != scalar_mode)
     abort ();
@@ -13807,7 +13805,7 @@
 
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  cmp_type = *ins->codep++ & 0xff;
+  cmp_type = *ins->codep++;
   /* There are aliases for immediates 0, 1, 2, 4, 5, 6.
      If it's the case, print suffix, otherwise - print the immediate.  */
   if (cmp_type < ARRAY_SIZE (simd_cmp_op)
@@ -13862,7 +13860,7 @@
 
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  cmp_type = *ins->codep++ & 0xff;
+  cmp_type = *ins->codep++;
   if (cmp_type < ARRAY_SIZE (xop_cmp_op))
     {
       char suffix[3];
@@ -13909,7 +13907,7 @@
 
   if (!fetch_code (ins->info, ins->codep + 1))
     return false;
-  pclmul_type = *ins->codep++ & 0xff;
+  pclmul_type = *ins->codep++;
   switch (pclmul_type)
     {
     case 0x10: