arc: Pass proper CPU value to the disassembler

There was a problem with generation of the disassembler options for ARC in GDB,
because a BFD architecture name was used as a CPU name, but they have different
meaning even if some architectures have same name as respective CPUs.  Target
description specifies a BFD architecture, which is different from ARC CPU, as
accepted by the disassembler (and most other ARC tools), because CPU values are
much more fine grained - there can be multiple CPU values per single BFD
architecture.  As a result this code should translate architecture to some CPU
value.  Since there is no info on exact CPU configuration, it is best to use
the most feature-rich CPU, so that the disassembler will recognize all
instructions available to the specified architecture.

gdb/ChangeLog
yyyy-mm-dd  Anton Kolesov  <Anton.Kolesov@synopsys.com>

	* arc-tdep.c (arc_gdbarch_init): Pass proper cpu value to disassembler.
	* arc-tdep.h (arc_arch_is_em): New function.
	(arc_arch_is_hs): Likewise.

gdb/testsuite/ChangeLog
yyyy-mm-dd  Anton Kolesov  <Anton.Kolesov@synopsys.com>

	* gdb.arch/arc-tdesc-cpu.exp: New file.
	* gdb.arch/arc-tdesc-cpu.xml: Likewise.

6 files changed, 159 insertions, 2 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 39511502890..1205355dce9 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2017-10-11  Anton Kolesov  <Anton.Kolesov@synopsys.com>
+
+	* arc-tdep.c (arc_gdbarch_init): Pass proper cpu value to disassembler.
+	* arc-tdep.h (arc_arch_is_em): New function.
+	(arc_arch_is_hs): Likewise.
+
 2017-10-11  Egeyar Bagcioglu  <egeyar.bagcioglu@oracle.com>
 
 	* macrotab.h (macro_lookup_inclusion): Remove unnecessary
diff --git a/gdb/arc-tdep.c b/gdb/arc-tdep.c
index 1d05c5a20f3..771d6dfaff3 100644
--- a/gdb/arc-tdep.c
+++ b/gdb/arc-tdep.c
@@ -2085,8 +2085,38 @@ arc_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 	     existing gdbarches, which also can be problematic, if
 	     arc_gdbarch_init will start reusing existing gdbarch
 	     instances.  */
-	  arc_disassembler_options = xstrprintf ("cpu=%s",
-						 tdesc_arch->printable_name);
+	  /* Target description specifies a BFD architecture, which is
+	     different from ARC cpu, as accepted by disassembler (and most
+	     other ARC tools), because cpu values are much more fine grained -
+	     there can be multiple cpu values per single BFD architecture.  As
+	     a result this code should translate architecture to some cpu
+	     value.  Since there is no info on exact cpu configuration, it is
+	     best to use the most feature-rich CPU, so that disassembler will
+	     recognize all instructions available to the specified
+	     architecture.  */
+	  switch (tdesc_arch->mach)
+	    {
+	    case bfd_mach_arc_arc601:
+	      arc_disassembler_options = xstrdup ("cpu=arc601");
+	      break;
+	    case bfd_mach_arc_arc600:
+	      arc_disassembler_options = xstrdup ("cpu=arc600");
+	      break;
+	    case bfd_mach_arc_arc700:
+	      arc_disassembler_options = xstrdup ("cpu=arc700");
+	      break;
+	    case bfd_mach_arc_arcv2:
+	      /* Machine arcv2 has three arches: ARCv2, EM and HS; where ARCv2
+		 is treated as EM.  */
+	      if (arc_arch_is_hs (tdesc_arch))
+		arc_disassembler_options = xstrdup ("cpu=hs38_linux");
+	      else
+		arc_disassembler_options = xstrdup ("cpu=em4_fpuda");
+	      break;
+	    default:
+	      arc_disassembler_options = NULL;
+	      break;
+	    }
 	  set_gdbarch_disassembler_options (gdbarch,
 					    &arc_disassembler_options);
 	}
diff --git a/gdb/arc-tdep.h b/gdb/arc-tdep.h
index 1bf18179893..580ccb74b1e 100644
--- a/gdb/arc-tdep.h
+++ b/gdb/arc-tdep.h
@@ -123,6 +123,21 @@ arc_mach_is_arcv2 (struct gdbarch *gdbarch)
   return gdbarch_bfd_arch_info (gdbarch)->mach == bfd_mach_arc_arcv2;
 }
 
+/* ARC EM and ARC HS are unique BFD arches, however they share the same machine
+   number as "ARCv2".  */
+
+static inline bool
+arc_arch_is_hs (const struct bfd_arch_info* arch)
+{
+  return startswith (arch->printable_name, "HS");
+}
+
+static inline bool
+arc_arch_is_em (const struct bfd_arch_info* arch)
+{
+  return startswith (arch->printable_name, "EM");
+}
+
 /* Function to access ARC disassembler.  Underlying opcodes disassembler will
    print an instruction into stream specified in the INFO, so if it is
    undesired, then this stream should be set to some invisible stream, but it
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index dd0645c80fc..77d638b0481 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-10-11  Anton Kolesov  <Anton.Kolesov@synopsys.com>
+
+	* gdb.arch/arc-tdesc-cpu.exp: New file.
+	* gdb.arch/arc-tdesc-cpu.xml: Likewise.
+
 2017-10-10  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* lib/gdb.exp (get_integer_valueof): Don't output read value in test name.
diff --git a/gdb/testsuite/gdb.arch/arc-tdesc-cpu.exp b/gdb/testsuite/gdb.arch/arc-tdesc-cpu.exp
new file mode 100644
index 00000000000..f1c009da1e2
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/arc-tdesc-cpu.exp
@@ -0,0 +1,48 @@
+# Copyright 2017 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+if {[gdb_skip_xml_test]} {
+    unsupported "arc-tdesc-cpu.exp"
+    return -1
+}
+
+gdb_start
+
+# Test whether it is OK to have `arc:HS` in the target description
+# architecture.  `HS` is a valid BFD architecture name, however the
+# disassembler doesn't accept it as a CPU name.  This test checks that GDB
+# doesn't pass architecture from the target description directly to the
+# disassembler and instead uses one of the valid CPU names.
+
+set filename $srcdir/$subdir/arc-tdesc-cpu.xml
+
+set cmd "set tdesc filename $filename"
+gdb_test $cmd
+
+# An error message is emitted by the disassembler, therefore it is not shown
+# unless the disassembler is actually invoked.  Address "0" is not invalid,
+# but that doesn't matter for this test case, because it is only the
+# disassembler error message that is interesting.
+set cmd "x /i 0"
+set msg "setting HS architecture"
+gdb_test_multiple $cmd $msg {
+    -re "Unrecognised disassembler CPU option: HS.*$gdb_prompt" {
+	fail $msg
+    }
+    -re "^$cmd\r\n\\s*$hex:\\s+Cannot access memory at address $hex\r\n$gdb_prompt"
+    {
+	pass $msg
+    }
+}
diff --git a/gdb/testsuite/gdb.arch/arc-tdesc-cpu.xml b/gdb/testsuite/gdb.arch/arc-tdesc-cpu.xml
new file mode 100644
index 00000000000..fe158ae48fb
--- /dev/null
+++ b/gdb/testsuite/gdb.arch/arc-tdesc-cpu.xml
@@ -0,0 +1,53 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2017 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE target SYSTEM "gdb-target.dtd">
+<target>
+  <architecture>arc:HS</architecture>
+
+  <feature name="org.gnu.gdb.arc.core.v2">
+    <reg name="r0"  bitsize="32"/>
+    <reg name="r1"  bitsize="32"/>
+    <reg name="r2"  bitsize="32"/>
+    <reg name="r3"  bitsize="32"/>
+    <reg name="r4"  bitsize="32"/>
+    <reg name="r5"  bitsize="32"/>
+    <reg name="r6"  bitsize="32"/>
+    <reg name="r7"  bitsize="32"/>
+    <reg name="r8"  bitsize="32"/>
+    <reg name="r9"  bitsize="32"/>
+    <reg name="r10" bitsize="32"/>
+    <reg name="r11" bitsize="32"/>
+    <reg name="r12" bitsize="32"/>
+    <reg name="r13" bitsize="32"/>
+    <reg name="r14" bitsize="32"/>
+    <reg name="r15" bitsize="32"/>
+    <reg name="r16" bitsize="32"/>
+    <reg name="r17" bitsize="32"/>
+    <reg name="r18" bitsize="32"/>
+    <reg name="r19" bitsize="32"/>
+    <reg name="r20" bitsize="32"/>
+    <reg name="r21" bitsize="32"/>
+    <reg name="r22" bitsize="32"/>
+    <reg name="r23" bitsize="32"/>
+    <reg name="r24" bitsize="32"/>
+    <reg name="r25" bitsize="32"/>
+    <reg name="gp"  bitsize="32"/>
+    <reg name="fp"  bitsize="32"/>
+    <reg name="sp"  bitsize="32"/>
+    <reg name="ilink" bitsize="32"/>
+    <reg name="r30"   bitsize="32"/>
+    <reg name="blink" bitsize="32"/>
+    <reg name="lp_count" bitsize="32"/>
+    <reg name="pcl" bitsize="32"/>
+  </feature>
+
+  <feature name="org.gnu.gdb.arc.aux-minimal">
+    <reg name="pc"       bitsize="32"/>
+    <reg name="status32" bitsize="32"/>
+  </feature>
+</target>