Fix internal error on DW_OP_bregx(-1)

diff --git a/gdb/findvar.c b/gdb/findvar.c
index 0f46e53..855947d 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -927,6 +927,12 @@  address_from_register (int regnum, struct frame_info *frame)
   struct type *type = builtin_type (gdbarch)->builtin_data_ptr;
   struct value *value;
   CORE_ADDR result;
+  int regnum_max_excl = (gdbarch_num_regs (gdbarch)
+			 + gdbarch_num_pseudo_regs (gdbarch));
+
+  if (regnum < 0 || regnum >= regnum_max_excl)
+    error (_("Invalid register #%d, expecting 0 <= # < %d"), regnum,
+	   regnum_max_excl);
 
   /* This routine may be called during early unwinding, at a time
      where the ID of FRAME is not yet known.  Calling value_from_register
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.S b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.S
new file mode 100644
index 0000000..075bfd6
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.S
@@ -0,0 +1,91 @@ 
+/* Copyright 2015 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/>.  */
+
+	.section	.debug_info
+debug_start:
+	.4byte	debug_end - 1f	/* Length of Compilation Unit Info */
+1:
+	.2byte	0x3	/* DWARF version number */
+	.4byte	.Ldebug_abbrev0	/* Offset Into Abbrev. Section */
+	.byte	0x4	/* Pointer Size (in bytes) */
+	.uleb128 0x1	/* (DIE (0xb) DW_TAG_compile_unit) */
+	.ascii "clang-3.5.0-9.fc22.x86_64\0"	/* DW_AT_producer */
+	.byte	0x1	/* DW_AT_language */
+	.ascii "1.c\0"	/* DW_AT_name */
+	.4byte	main_label		/* DW_AT_low_pc */
+	.4byte	main_label+0x10000	/* DW_AT_high_pc */
+
+	.uleb128	2			/* Abbrev: DW_TAG_subprogram */
+	.byte		1			/* DW_AT_external */
+	.ascii		"main\0"		/* DW_AT_name */
+	.4byte	main_label		/* DW_AT_low_pc */
+	.4byte	main_label+0x10000	/* DW_AT_high_pc */
+
+	.uleb128 0x4	/* (DW_TAG_variable) */
+	.ascii "variable\0"	/* DW_AT_name */
+	.2byte	2f - 1f	/* DW_AT_location: DW_FORM_block2 */
+1:
+	.byte	0x92	/* DW_OP_bregx */
+	.uleb128	0xffffffff
+	.sleb128 0
+2:
+
+	.byte	0x0	/* end of children of main */
+	.byte	0x0	/* end of children of CU */
+debug_end:
+
+	.section	.debug_abbrev
+.Ldebug_abbrev0:
+	.uleb128 0x1	/* (abbrev code) */
+	.uleb128 0x11	/* (TAG: DW_TAG_compile_unit) */
+	.byte	0x1	/* DW_children_yes */
+	.uleb128 0x25	/* (DW_AT_producer) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.uleb128 0x13	/* (DW_AT_language) */
+	.uleb128 0xb	/* (DW_FORM_data1) */
+	.uleb128 0x3	/* (DW_AT_name) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.byte	0x0
+	.byte	0x0
+
+	.uleb128	2			/* Abbrev code */
+	.uleb128	0x2e			/* DW_TAG_subprogram */
+	.byte		1			/* has_children */
+	.uleb128	0x3f			/* DW_AT_external */
+	.uleb128	0xc			/* DW_FORM_flag */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x11			/* DW_AT_low_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.uleb128	0x12			/* DW_AT_high_pc */
+	.uleb128	0x1			/* DW_FORM_addr */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
+
+	.uleb128 0x4	/* (abbrev code) */
+	.uleb128 0x34	/* (TAG: DW_TAG_variable) */
+	.byte	0x0	/* DW_children_yes */
+	.uleb128 0x3	/* (DW_AT_name) */
+	.uleb128 0x8	/* (DW_FORM_string) */
+	.uleb128 0x02	/* (DW_AT_location) */
+	.uleb128 0x3	/* (DW_FORM_block2) */
+	.byte	0x0
+	.byte	0x0
+	.byte	0x0
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp
new file mode 100644
index 0000000..7c3a404
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-regno-invalid.exp
@@ -0,0 +1,32 @@ 
+# Copyright 2015 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/>.
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0  
+}
+
+standard_testfile .S main.c
+
+if { [gdb_compile "${srcdir}/${subdir}/${srcfile} ${srcdir}/${subdir}/${srcfile2}" \
+		  "${binfile}" executable {}] != "" } {
+    return -1
+}
+
+clean_restart ${binfile}
+runto_main
+
+gdb_test "p variable"