arc: Detect usage of illegal double register pairs

ARC can use odd-even double register pairs in some selected
instructions. Although the GNU assembler doesn't allow even-odd
registers to be used, there may be cases when the disassembler is
presented with such situation.  This patch add a test and detects such
cases.

opcodes/
2020-07-14  Claudiu Zissulescu  <claziss@gmail.com>

	* arc-dis.c (print_insn_arc): Detect and emit a warning when a
	faulty double register pair is detected.

binutils/
2020-07-14  Claudiu Zissulescu  <claziss@gmail.com>

	* testsuite/binutils-all/arc/double_regs.s: New test.
	* testsuite/binutils-all/arc/objdump.exp: Add the above test.

Signed-off-by: Claudiu Zissulescu <claziss@gmail.com>

5 files changed, 27 insertions, 3 deletions

diff --git a/binutils/ChangeLog b/binutils/ChangeLog
index 7219f85..708be22 100644
--- a/binutils/ChangeLog
+++ b/binutils/ChangeLog
@@ -1,3 +1,8 @@
+2020-07-14  Claudiu Zissulescu  <claziss@gmail.com>
+
+	* testsuite/binutils-all/arc/double_regs.s: New test.
+	* testsuite/binutils-all/arc/objdump.exp: Add the above test.
+
 2020-07-13  Nick Clifton  <nickc@redhat.com>
 
 	* po/fr.po: Updated French translation.
diff --git a/binutils/testsuite/binutils-all/arc/double_regs.s b/binutils/testsuite/binutils-all/arc/double_regs.s
new file mode 100644
index 0000000..5d3aa86
--- /dev/null
+++ b/binutils/testsuite/binutils-all/arc/double_regs.s
@@ -0,0 +1,3 @@
+	.cpu HS
+	.text
+	.byte 0x9e,0x2f,0x20,0x75
diff --git a/binutils/testsuite/binutils-all/arc/objdump.exp b/binutils/testsuite/binutils-all/arc/objdump.exp
index 18f0bb7..542a336 100644
--- a/binutils/testsuite/binutils-all/arc/objdump.exp
+++ b/binutils/testsuite/binutils-all/arc/objdump.exp
@@ -72,6 +72,9 @@ proc check_assembly { testname objfile expected { disas_flags "" } } {
 # disassembler has had to guess as the instruction class in use).
 set want "Warning: disassembly.*vmac2hnfr\[ \t\]*r0,r2,r4.*dmulh12.f\[ \t\]*r0,r2,r4.*dmulh11.f"
 check_assembly "Warning test" [do_objfile dsp.s] $want
+set warn_double_reg "Warning: illegal use of double register pair."
+check_assembly "Warning faulty double regs" [do_objfile double_regs.s] \
+    $warn_double_reg
 
 set double_store_hs_expected {std\s*r0r1,\[r3\]}
 set objfile [do_objfile double_store.s]
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 3a38bb2..f571884 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,8 @@
+2020-07-14  Claudiu Zissulescu  <claziss@gmail.com>
+
+	* arc-dis.c (print_insn_arc): Detect and emit a warning when a
+	faulty double register pair is detected.
+
 2020-07-14  Jan Beulich  <jbeulich@suse.com>
 
 	* i386-dis.c (OP_D): Print dr<N> instead of db<N> in Intel mode.
diff --git a/opcodes/arc-dis.c b/opcodes/arc-dis.c
index bf31940..27852e8 100644
--- a/opcodes/arc-dis.c
+++ b/opcodes/arc-dis.c
@@ -1269,11 +1269,19 @@ print_insn_arc (bfd_vma memaddr,
 	  if (!rname)
 	    rname = regnames[value];
 	  (*info->fprintf_func) (info->stream, "%s", rname);
+
+	  /* Check if we have a double register to print.  */
 	  if (operand->flags & ARC_OPERAND_TRUNCATE)
 	    {
-	      rname = arcExtMap_coreRegName (value + 1);
-	      if (!rname)
-		rname = regnames[value + 1];
+	      if ((value & 0x01) == 0)
+		{
+		  rname = arcExtMap_coreRegName (value + 1);
+		  if (!rname)
+		    rname = regnames[value + 1];
+		}
+	      else
+		rname = _("\nWarning: illegal use of double register "
+			  "pair.\n");
 	      (*info->fprintf_func) (info->stream, "%s", rname);
 	    }
 	  if (value == 63)