[PATCHv2 1/3] opcodes/arc: Move instruction length logic to new function

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

Move the logic that calculates the instruction length out to a new
function.  Restructure the code to make it simpler.

opcodes/ChangeLog:

	* arc-dis.c (arc_insn_length): New function.
	(print_insn_arc): Use arc_insn_length.
---
 opcodes/ChangeLog |  5 +++++
 opcodes/arc-dis.c | 57 ++++++++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/opcodes/arc-dis.c b/opcodes/arc-dis.c
index eb8bd67..458ba47 100644
--- a/opcodes/arc-dis.c
+++ b/opcodes/arc-dis.c
@@ -309,6 +309,41 @@ get_auxreg (const struct arc_opcode *opcode,
     }
   return NULL;
 }
+
+/* Calculate the instruction length for an instruction starting with MSB
+   and LSB, the most and least significant byte.  The ISA_MASK is used to
+   filter the instructions considered to only those that are part of the
+   current architecture.
+
+   The instruction lengths are calculated from the ARC_OPCODE table, and
+   cached for later use.  */
+
+static int
+arc_insn_length (bfd_byte msb, bfd_byte lsb ATTRIBUTE_UNUSED,
+                 struct disassemble_info *info)
+{
+  bfd_byte major_opcode = msb >> 3;
+  int len = 0;
+
+  switch (info->mach)
+    {
+    case bfd_mach_arc_nps400:
+    case bfd_mach_arc_arc700:
+    case bfd_mach_arc_arc600:
+      len = (major_opcode > 0xb) ? 2 : 4;
+      break;
+
+    case bfd_mach_arc_arcv2:
+      len = (major_opcode > 0x7) ? 2 : 4;
+      break;
+
+    default:
+      abort ();
+    }
+
+  return len;
+}
+
 /* Disassemble ARC instructions.  */
 
 static int
@@ -422,20 +457,19 @@ print_insn_arc (bfd_vma memaddr,
       return size;
     }
 
-  if ((((buffer[lowbyte] & 0xf8) > 0x38)
-       && ((buffer[lowbyte] & 0xf8) != 0x48))
-      || ((info->mach == bfd_mach_arc_arcv2)
-	  && ((buffer[lowbyte] & 0xF8) == 0x48)) /* FIXME! ugly.  */
-      )
+  insnLen = arc_insn_length (buffer[lowbyte], buffer[highbyte], info);
+  switch (insnLen)
     {
-      /* This is a short instruction.  */
-      insnLen = 2;
+    case 2:
       insn[0] = (buffer[lowbyte] << 8) | buffer[highbyte];
-    }
-  else
-    {
-      insnLen = 4;
+      break;
 
+    default:
+      /* An unknown instruction is treated as being length 4.  This is
+         possibly not the best solution, but matches the behaviour that was
+         in place before the table based instruction length look-up was
+         introduced.  */
+    case 4:
       /* This is a long instruction: Read the remaning 2 bytes.  */
       status = (*info->read_memory_func) (memaddr + 2, &buffer[2], 2, info);
       if (status != 0)
@@ -444,6 +478,7 @@ print_insn_arc (bfd_vma memaddr,
 	  return -1;
 	}
       insn[0] = ARRANGE_ENDIAN (info, buffer);
+      break;
     }
 
   /* Set some defaults for the insn info.  */
-- 
2.5.1