Remove xml files from gdbserver

For ports which use new target descriptions, this patch removes
the xml files from being built into gdbserver,

Alan.

2018-03-21 Alan Hayward  <alan.hayward@arm.com>

gdbserver/
	* configure.srv (aarch64*-*-linux*): Don't include xml.
	(i[34567]86-*-cygwin*): Likewise.
	(i[34567]86-*-linux*): Likewise.
	(i[34567]86-*-lynxos*): Likewise.
	(i[34567]86-*-mingw32ce*): Likewise.
	(i[34567]86-*-mingw*): Likewise.
	(i[34567]86-*-nto*): Likewise.
	(tic6x-*-uclinux): Likewise.
	(x86_64-*-linux*): Likewise.
	(x86_64-*-mingw*): Likewise.
	(x86_64-*-cygwin*): Likewise.

gdb/Makefile.in

@@ -967,6 +967,7 @@ COMMON_SFILES = \
 	common/run-time-clock.c \
 	common/signals.c \
 	common/signals-state-save-restore.c \
+	common/tdesc.c \
 	common/vec.c \
 	common/xml-utils.c \
 	complaints.c \
@@ -1444,6 +1445,7 @@ HFILES_NO_SRCDIR = \
 	common/run-time-clock.h \
 	common/signals-state-save-restore.h \
 	common/symbol.h \
+	common/tdesc.h \
 	common/vec.h \
 	common/version.h \
 	common/x86-xstate.h \

gdb/common/tdesc.c

@@ -0,0 +1,397 @@
+/* Target description support for GDB.
+
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#ifdef GDBSERVER
+#include "server.h"
+#else
+#include "defs.h"
+#endif
+
+#include "common/tdesc.h"
+
+tdesc_reg::tdesc_reg (struct tdesc_feature *feature, const std::string &name_,
+		      int regnum, int save_restore_, const char *group_,
+		      int bitsize_, const char *type_)
+  : name (name_), target_regnum (regnum),
+    save_restore (save_restore_),
+    group (group_ != NULL ? group_ : ""),
+    bitsize (bitsize_),
+    type (type_ != NULL ? type_ : "<unknown>")
+{
+  /* If the register's type is target-defined, look it up now.  We may not
+     have easy access to the containing feature when we want it later.  */
+  tdesc_type = tdesc_named_type (feature, type.c_str ());
+}
+
+/* Predefined types.  */
+static tdesc_type_builtin tdesc_predefined_types[] =
+{
+  { "bool", TDESC_TYPE_BOOL },
+  { "int8", TDESC_TYPE_INT8 },
+  { "int16", TDESC_TYPE_INT16 },
+  { "int32", TDESC_TYPE_INT32 },
+  { "int64", TDESC_TYPE_INT64 },
+  { "int128", TDESC_TYPE_INT128 },
+  { "uint8", TDESC_TYPE_UINT8 },
+  { "uint16", TDESC_TYPE_UINT16 },
+  { "uint32", TDESC_TYPE_UINT32 },
+  { "uint64", TDESC_TYPE_UINT64 },
+  { "uint128", TDESC_TYPE_UINT128 },
+  { "code_ptr", TDESC_TYPE_CODE_PTR },
+  { "data_ptr", TDESC_TYPE_DATA_PTR },
+  { "ieee_single", TDESC_TYPE_IEEE_SINGLE },
+  { "ieee_double", TDESC_TYPE_IEEE_DOUBLE },
+  { "arm_fpa_ext", TDESC_TYPE_ARM_FPA_EXT },
+  { "i387_ext", TDESC_TYPE_I387_EXT }
+};
+
+void tdesc_feature::accept (tdesc_element_visitor &v) const
+{
+  v.visit_pre (this);
+
+  for (const tdesc_type_up &type : types)
+    type->accept (v);
+
+  for (const tdesc_reg_up &reg : registers)
+    reg->accept (v);
+
+  v.visit_post (this);
+}
+
+bool tdesc_feature::operator== (const tdesc_feature &other) const
+{
+  if (name != other.name)
+    return false;
+
+  if (registers.size () != other.registers.size ())
+    return false;
+
+  for (int ix = 0; ix < registers.size (); ix++)
+    {
+      const tdesc_reg_up &reg1 = registers[ix];
+      const tdesc_reg_up &reg2 = other.registers[ix];
+
+      if (reg1 != reg2 && *reg1 != *reg2)
+	return false;
+      }
+
+  if (types.size () != other.types.size ())
+    return false;
+
+  for (int ix = 0; ix < types.size (); ix++)
+    {
+      const tdesc_type_up &type1 = types[ix];
+      const tdesc_type_up &type2 = other.types[ix];
+
+      if (type1 != type2 && *type1 != *type2)
+	return false;
+    }
+
+  return true;
+}
+
+/* Lookup a predefined type.  */
+
+static struct tdesc_type *
+tdesc_predefined_type (enum tdesc_type_kind kind)
+{
+  for (int ix = 0; ix < ARRAY_SIZE (tdesc_predefined_types); ix++)
+    if (tdesc_predefined_types[ix].kind == kind)
+      return &tdesc_predefined_types[ix];
+
+  gdb_assert_not_reached ("bad predefined tdesc type");
+}
+
+/* See common/tdesc.h.  */
+
+struct tdesc_type *
+tdesc_named_type (const struct tdesc_feature *feature, const char *id)
+{
+  /* First try target-defined types.  */
+  for (const tdesc_type_up &type : feature->types)
+    if (type->name == id)
+      return type.get ();
+
+  /* Next try the predefined types.  */
+  for (int ix = 0; ix < ARRAY_SIZE (tdesc_predefined_types); ix++)
+    if (tdesc_predefined_types[ix].name == id)
+      return &tdesc_predefined_types[ix];
+
+  return NULL;
+}
+
+/* See common/tdesc.h.  */
+
+void
+tdesc_create_reg (struct tdesc_feature *feature, const char *name,
+		  int regnum, int save_restore, const char *group,
+		  int bitsize, const char *type)
+{
+  tdesc_reg *reg = new tdesc_reg (feature, name, regnum, save_restore,
+				  group, bitsize, type);
+
+  feature->registers.emplace_back (reg);
+}
+
+/* See common/tdesc.h.  */
+
+struct tdesc_type *
+tdesc_create_vector (struct tdesc_feature *feature, const char *name,
+		     struct tdesc_type *field_type, int count)
+{
+  tdesc_type_vector *type = new tdesc_type_vector (name, field_type, count);
+  feature->types.emplace_back (type);
+
+  return type;
+}
+
+/* See common/tdesc.h.  */
+
+tdesc_type_with_fields *
+tdesc_create_struct (struct tdesc_feature *feature, const char *name)
+{
+  tdesc_type_with_fields *type
+    = new tdesc_type_with_fields (name, TDESC_TYPE_STRUCT);
+  feature->types.emplace_back (type);
+
+  return type;
+}
+
+/* See common/tdesc.h.  */
+
+void
+tdesc_set_struct_size (tdesc_type_with_fields *type, int size)
+{
+  gdb_assert (type->kind == TDESC_TYPE_STRUCT);
+  gdb_assert (size > 0);
+  type->size = size;
+}
+
+/* See common/tdesc.h.  */
+
+tdesc_type_with_fields *
+tdesc_create_union (struct tdesc_feature *feature, const char *name)
+{
+  tdesc_type_with_fields *type
+    = new tdesc_type_with_fields (name, TDESC_TYPE_UNION);
+  feature->types.emplace_back (type);
+
+  return type;
+}
+
+/* See common/tdesc.h.  */
+
+tdesc_type_with_fields *
+tdesc_create_flags (struct tdesc_feature *feature, const char *name,
+		    int size)
+{
+  gdb_assert (size > 0);
+
+  tdesc_type_with_fields *type
+    = new tdesc_type_with_fields (name, TDESC_TYPE_FLAGS, size);
+  feature->types.emplace_back (type);
+
+  return type;
+}
+
+tdesc_type_with_fields *
+tdesc_create_enum (struct tdesc_feature *feature, const char *name,
+		   int size)
+{
+  gdb_assert (size > 0);
+
+  tdesc_type_with_fields *type
+    = new tdesc_type_with_fields (name, TDESC_TYPE_ENUM, size);
+  feature->types.emplace_back (type);
+
+  return type;
+}
+
+/* See common/tdesc.h.  */
+
+void
+tdesc_add_field (tdesc_type_with_fields *type, const char *field_name,
+		 struct tdesc_type *field_type)
+{
+  gdb_assert (type->kind == TDESC_TYPE_UNION
+	      || type->kind == TDESC_TYPE_STRUCT);
+
+  /* Initialize start and end so we know this is not a bit-field
+     when we print-c-tdesc.  */
+  type->fields.emplace_back (field_name, field_type, -1, -1);
+}
+
+void
+tdesc_add_typed_bitfield (tdesc_type_with_fields *type, const char *field_name,
+			  int start, int end, struct tdesc_type *field_type)
+{
+  gdb_assert (type->kind == TDESC_TYPE_STRUCT
+	      || type->kind == TDESC_TYPE_FLAGS);
+  gdb_assert (start >= 0 && end >= start);
+
+  type->fields.emplace_back (field_name, field_type, start, end);
+}
+
+/* See common/tdesc.h.  */
+
+void
+tdesc_add_bitfield (tdesc_type_with_fields *type, const char *field_name,
+		    int start, int end)
+{
+  struct tdesc_type *field_type;
+
+  gdb_assert (start >= 0 && end >= start);
+
+  if (type->size > 4)
+    field_type = tdesc_predefined_type (TDESC_TYPE_UINT64);
+  else
+    field_type = tdesc_predefined_type (TDESC_TYPE_UINT32);
+
+  tdesc_add_typed_bitfield (type, field_name, start, end, field_type);
+}
+
+/* See common/tdesc.h.  */
+
+void
+tdesc_add_flag (tdesc_type_with_fields *type, int start,
+		const char *flag_name)
+{
+  gdb_assert (type->kind == TDESC_TYPE_FLAGS
+	      || type->kind == TDESC_TYPE_STRUCT);
+
+  type->fields.emplace_back (flag_name,
+			     tdesc_predefined_type (TDESC_TYPE_BOOL),
+			     start, start);
+}
+
+void
+tdesc_add_enum_value (tdesc_type_with_fields *type, int value,
+		      const char *name)
+{
+  gdb_assert (type->kind == TDESC_TYPE_ENUM);
+  type->fields.emplace_back (name,
+			     tdesc_predefined_type (TDESC_TYPE_INT32),
+			     value, -1);
+}
+
+void print_xml_feature::visit_pre (const tdesc_feature *e)
+{
+  string_appendf (m_buffer, "<feature name=\"%s\">\n", e->name.c_str ());
+}
+
+void print_xml_feature::visit_post (const tdesc_feature *e)
+{
+  string_appendf (m_buffer, "</feature>\n");
+}
+
+void print_xml_feature::visit (const tdesc_type_builtin *t)
+{
+  error (_("xml output is not supported type \"%s\"."), t->name.c_str ());
+}
+
+void print_xml_feature::visit (const tdesc_type_vector *t)
+{
+  string_appendf (m_buffer, "<vector id=\"%s\" type=\"%s\" count=\"%d\"/>\n",
+		  t->name.c_str (), t->element_type->name.c_str (), t->count);
+}
+
+void print_xml_feature::visit (const tdesc_type_with_fields *t)
+{
+  struct tdesc_type_field *f;
+  const static char *types[] = { "struct", "union", "flags", "enum" };
+
+  gdb_assert (t->kind >= TDESC_TYPE_STRUCT && t->kind <= TDESC_TYPE_ENUM);
+
+  string_appendf (m_buffer, "<%s id=\"%s\"", types[t->kind - TDESC_TYPE_STRUCT],
+		  t->name.c_str ());
+
+  switch (t->kind)
+    {
+    case TDESC_TYPE_STRUCT:
+    case TDESC_TYPE_FLAGS:
+      if (t->size > 0)
+	string_appendf (m_buffer, " size=\"%d\"", t->size);
+      string_appendf (m_buffer, ">\n");
+
+      for (const tdesc_type_field &f : t->fields)
+	{
+	  string_appendf (m_buffer, "  <field name=\"%s\" ", f.name.c_str ());
+	  if (f.start == -1)
+	    string_appendf (m_buffer, "type=\"%s\"/>\n", f.type->name.c_str ());
+	  else
+	    string_appendf (m_buffer, "start=\"%d\" end=\"%d\"/>\n", f.start,
+			    f.end);
+	}
+      break;
+
+    case TDESC_TYPE_ENUM:
+      string_appendf (m_buffer, ">\n");
+      for (const tdesc_type_field &f : t->fields)
+	string_appendf (m_buffer, "  <field name=\"%s\" start=\"%d\"/>\n",
+			f.name.c_str (), f.start);
+      break;
+
+    case TDESC_TYPE_UNION:
+      string_appendf (m_buffer, ">\n");
+      for (const tdesc_type_field &f : t->fields)
+	string_appendf (m_buffer, "  <field name=\"%s\" type=\"%s\"/>\n",
+			f.name.c_str (), f.type->name.c_str ());
+      break;
+
+    default:
+      error (_("xml output is not supported type \"%s\"."), t->name.c_str ());
+    }
+
+  string_appendf (m_buffer, "</%s>\n", types[t->kind - TDESC_TYPE_STRUCT]);
+}
+
+void print_xml_feature::visit (const tdesc_reg *r)
+{
+  string_appendf (m_buffer,
+		  "<reg name=\"%s\" bitsize=\"%d\" type=\"%s\" regnum=\"%ld\"",
+		  r->name.c_str (), r->bitsize, r->type.c_str (),
+		  r->target_regnum);
+
+  if (r->group.length () > 0)
+    string_appendf (m_buffer, " group=\"%s\"", r->group.c_str ());
+
+  if (r->save_restore == 0)
+    string_appendf (m_buffer, " save-restore=\"no\"");
+
+  string_appendf (m_buffer, "/>\n");
+}
+
+void print_xml_feature::visit_pre (const target_desc *e)
+{
+#ifndef IN_PROCESS_AGENT
+  string_appendf (m_buffer, "<?xml version=\"1.0\"?>\n");
+  string_appendf (m_buffer, "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">\n");
+  string_appendf (m_buffer, "<target>\n<architecture>%s</architecture>\n",
+		  tdesc_architecture_name (e));
+
+  const char *osabi = tdesc_osabi_name (e);
+  if (osabi != nullptr)
+    string_appendf (m_buffer, "<osabi>%s</osabi>", osabi);
+#endif
+}
+
+void print_xml_feature::visit_post (const target_desc *e)
+{
+  string_appendf (m_buffer, "</target>\n");
+}

gdb/common/tdesc.h

@@ -18,6 +18,12 @@
 #ifndef ARCH_TDESC_H
 #define ARCH_TDESC_H 1
 
+#ifdef GDBSERVER
+#include "server.h"
+#else
+#include "defs.h"
+#endif
+
 struct tdesc_feature;
 struct tdesc_type;
 struct tdesc_type_builtin;
@@ -26,6 +32,270 @@ struct tdesc_type_with_fields;
 struct tdesc_reg;
 struct target_desc;
 
+/* The interface to visit different elements of target description.  */
+
+class tdesc_element_visitor
+{
+public:
+  virtual void visit_pre (const target_desc *e)
+  {}
+
+  virtual void visit_post (const target_desc *e)
+  {}
+
+  virtual void visit_pre (const tdesc_feature *e)
+  {}
+
+  virtual void visit_post (const tdesc_feature *e)
+  {}
+
+  virtual void visit (const tdesc_type_builtin *e)
+  {}
+
+  virtual void visit (const tdesc_type_vector *e)
+  {}
+
+  virtual void visit (const tdesc_type_with_fields *e)
+  {}
+
+  virtual void visit (const tdesc_reg *e)
+  {}
+};
+
+class tdesc_element
+{
+public:
+  virtual void accept (tdesc_element_visitor &v) const = 0;
+};
+
+/* An individual register from a target description.  */
+
+struct tdesc_reg : tdesc_element
+{
+  tdesc_reg (struct tdesc_feature *feature, const std::string &name_,
+	     int regnum, int save_restore_, const char *group_,
+	     int bitsize_, const char *type_);
+
+  virtual ~tdesc_reg () = default;
+
+  DISABLE_COPY_AND_ASSIGN (tdesc_reg);
+
+  /* The name of this register.  In standard features, it may be
+     recognized by the architecture support code, or it may be purely
+     for the user.  */
+  std::string name;
+
+  /* The register number used by this target to refer to this
+     register.  This is used for remote p/P packets and to determine
+     the ordering of registers in the remote g/G packets.  */
+  long target_regnum;
+
+  /* If this flag is set, GDB should save and restore this register
+     around calls to an inferior function.  */
+  int save_restore;
+
+  /* The name of the register group containing this register, or empty
+     if the group should be automatically determined from the
+     register's type.  If this is "general", "float", or "vector", the
+     corresponding "info" command should display this register's
+     value.  It can be an arbitrary string, but should be limited to
+     alphanumeric characters and internal hyphens.  Currently other
+     strings are ignored (treated as empty).  */
+  std::string group;
+
+  /* The size of the register, in bits.  */
+  int bitsize;
+
+  /* The type of the register.  This string corresponds to either
+     a named type from the target description or a predefined
+     type from GDB.  */
+  std::string type;
+
+  /* The target-described type corresponding to TYPE, if found.  */
+  struct tdesc_type *tdesc_type;
+
+  void accept (tdesc_element_visitor &v) const override
+  {
+    v.visit (this);
+  }
+
+  bool operator== (const tdesc_reg &other) const
+  {
+    return (name == other.name
+       && target_regnum == other.target_regnum
+       && save_restore == other.save_restore
+       && bitsize == other.bitsize
+       && group == other.group
+       && type == other.type);
+  }
+
+  bool operator!= (const tdesc_reg &other) const
+  {
+    return !(*this == other);
+  }
+};
+
+typedef std::unique_ptr<tdesc_reg> tdesc_reg_up;
+
+enum tdesc_type_kind
+{
+  /* Predefined types.  */
+  TDESC_TYPE_BOOL,
+  TDESC_TYPE_INT8,
+  TDESC_TYPE_INT16,
+  TDESC_TYPE_INT32,
+  TDESC_TYPE_INT64,
+  TDESC_TYPE_INT128,
+  TDESC_TYPE_UINT8,
+  TDESC_TYPE_UINT16,
+  TDESC_TYPE_UINT32,
+  TDESC_TYPE_UINT64,
+  TDESC_TYPE_UINT128,
+  TDESC_TYPE_CODE_PTR,
+  TDESC_TYPE_DATA_PTR,
+  TDESC_TYPE_IEEE_SINGLE,
+  TDESC_TYPE_IEEE_DOUBLE,
+  TDESC_TYPE_ARM_FPA_EXT,
+  TDESC_TYPE_I387_EXT,
+
+  /* Types defined by a target feature.  */
+  TDESC_TYPE_VECTOR,
+  TDESC_TYPE_STRUCT,
+  TDESC_TYPE_UNION,
+  TDESC_TYPE_FLAGS,
+  TDESC_TYPE_ENUM
+};
+
+struct tdesc_type : tdesc_element
+{
+  tdesc_type (const std::string &name_, enum tdesc_type_kind kind_)
+    : name (name_), kind (kind_)
+  {}
+
+  virtual ~tdesc_type () = default;
+
+  DISABLE_COPY_AND_ASSIGN (tdesc_type);
+
+  /* The name of this type.  */
+  std::string name;
+
+  /* Identify the kind of this type.  */
+  enum tdesc_type_kind kind;
+
+  bool operator== (const tdesc_type &other) const
+  {
+    return name == other.name && kind == other.kind;
+  }
+
+  bool operator!= (const tdesc_type &other) const
+  {
+    return !(*this == other);
+  }
+};
+
+typedef std::unique_ptr<tdesc_type> tdesc_type_up;
+
+struct tdesc_type_builtin : tdesc_type
+{
+  tdesc_type_builtin (const std::string &name, enum tdesc_type_kind kind)
+  : tdesc_type (name, kind)
+  {}
+
+  void accept (tdesc_element_visitor &v) const override
+  {
+    v.visit (this);
+  }
+};
+
+/* tdesc_type for vector types.  */
+
+struct tdesc_type_vector : tdesc_type
+{
+  tdesc_type_vector (const std::string &name, tdesc_type *element_type_,
+		     int count_)
+  : tdesc_type (name, TDESC_TYPE_VECTOR),
+    element_type (element_type_), count (count_)
+  {}
+
+  void accept (tdesc_element_visitor &v) const override
+  {
+    v.visit (this);
+  }
+
+  struct tdesc_type *element_type;
+  int count;
+};
+
+/* A named type from a target description.  */
+
+struct tdesc_type_field
+{
+  tdesc_type_field (const std::string &name_, tdesc_type *type_,
+		    int start_, int end_)
+  : name (name_), type (type_), start (start_), end (end_)
+  {}
+
+  std::string name;
+  struct tdesc_type *type;
+  /* For non-enum-values, either both are -1 (non-bitfield), or both are
+     not -1 (bitfield).  For enum values, start is the value (which could be
+     -1), end is -1.  */
+  int start, end;
+};
+
+/* tdesc_type for struct, union, flags, and enum types.  */
+
+struct tdesc_type_with_fields : tdesc_type
+{
+  tdesc_type_with_fields (const std::string &name, tdesc_type_kind kind,
+			  int size_ = 0)
+  : tdesc_type (name, kind), size (size_)
+  {}
+
+  void accept (tdesc_element_visitor &v) const override
+  {
+    v.visit (this);
+  }
+
+  std::vector<tdesc_type_field> fields;
+  int size;
+};
+
+/* A feature from a target description.  Each feature is a collection
+   of other elements, e.g. registers and types.  */
+
+struct tdesc_feature : tdesc_element
+{
+  tdesc_feature (const std::string &name_)
+    : name (name_)
+  {}
+
+  virtual ~tdesc_feature () = default;
+
+  DISABLE_COPY_AND_ASSIGN (tdesc_feature);
+
+  /* The name of this feature.  It may be recognized by the architecture
+     support code.  */
+  std::string name;
+
+  /* The registers associated with this feature.  */
+  std::vector<tdesc_reg_up> registers;
+
+  /* The types associated with this feature.  */
+  std::vector<tdesc_type_up> types;
+
+  void accept (tdesc_element_visitor &v) const override;
+
+  bool operator== (const tdesc_feature &other) const;
+
+  bool operator!= (const tdesc_feature &other) const
+  {
+    return !(*this == other);
+  }
+};
+
+typedef std::unique_ptr<tdesc_feature> tdesc_feature_up;
+
 /* Allocate a new target_desc.  */
 target_desc *allocate_target_description (void);
 
@@ -33,9 +303,18 @@ target_desc *allocate_target_description (void);
 void set_tdesc_architecture (target_desc *target_desc,
 			     const char *name);
 
+/* Return the architecture associated with this target description as a string,
+   or NULL if no architecture was specified.  */
+const char *tdesc_architecture_name (const struct target_desc *target_desc);
+
 /* Set TARGET_DESC's osabi by NAME.  */
 void set_tdesc_osabi (target_desc *target_desc, const char *name);
 
+/* Return the osabi associated with this target description as a string,
+   or NULL if no osabi was specified.  */
+const char *
+tdesc_osabi_name (const struct target_desc *target_desc);
+
 /* Return the type associated with ID in the context of FEATURE, or
    NULL if none.  */
 struct tdesc_type *tdesc_named_type (const struct tdesc_feature *feature,
@@ -43,9 +322,7 @@ struct tdesc_type *tdesc_named_type (const struct tdesc_feature *feature,
 
 /* Return the created feature named NAME in target description TDESC.  */
 struct tdesc_feature *tdesc_create_feature (struct target_desc *tdesc,
-					    const char *name,
-					    const char *xml = nullptr);
-
+					    const char *name);
 
 /* Return the created vector tdesc_type named NAME in FEATURE.  */
 struct tdesc_type *tdesc_create_vector (struct tdesc_feature *feature,
@@ -92,4 +369,33 @@ void tdesc_create_reg (struct tdesc_feature *feature, const char *name,
 		       int regnum, int save_restore, const char *group,
 		       int bitsize, const char *type);
 
+/* Return the tdesc in string XML format.  */
+
+const char *tdesc_get_features_xml (target_desc *tdesc);
+
+/* Print target description as xml.  */
+
+class print_xml_feature : public tdesc_element_visitor
+{
+public:
+  print_xml_feature (std::string &buffer_)
+    : m_buffer (buffer_)
+  {}
+
+  ~print_xml_feature ()
+  {}
+
+  void visit_pre (const target_desc *e) override;
+  void visit_post (const target_desc *e) override;
+  void visit_pre (const tdesc_feature *e) override;
+  void visit_post (const tdesc_feature *e) override;
+  void visit (const tdesc_type_builtin *type) override;
+  void visit (const tdesc_type_vector *type) override;
+  void visit (const tdesc_type_with_fields *type) override;
+  void visit (const tdesc_reg *reg) override;
+
+private:
+  std::string &m_buffer;
+};
+
 #endif /* ARCH_TDESC_H */

gdb/features/Makefile

@@ -193,12 +193,18 @@ XMLTOC = \
 TDESC_CFILES = $(patsubst %.xml,%.c,$(XMLTOC))
 GDB = false
 
+#Targets which use feature based target descriptions.
+aarch64-feature = 1
+i386-feature = 1
+tic6x-feature = 1
+
 all: $(OUTPUTS)
 
 $(outdir)/%.dat: %.xml number-regs.xsl sort-regs.xsl gdbserver-regs.xsl
 	echo "# THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:" > $(outdir)/$*.tmp
 	echo "# Generated from: $<" >> $(outdir)/$*.tmp
 	echo "name:`echo $(notdir $*) | sed 's/-/_/g'`" >> $(outdir)/$*.tmp
+	$(if $($(firstword $(subst /, ,$(subst -, ,$*)))-feature), echo "feature:1") >> $(outdir)/$*.tmp
 	echo "xmltarget:$(<F)" >> $(outdir)/$*.tmp
 	echo "expedite:$(if $($*-expedite),$($*-expedite),$($(firstword $(subst -, ,$(notdir $*)))-expedite))" \
 	  >> $(outdir)/$*.tmp

gdb/features/aarch64-core.c

@@ -8,7 +8,7 @@ create_feature_aarch64_core (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.core", "aarch64-core.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.core");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_flags (feature, "cpsr_flags", 4);
   tdesc_add_flag (type_with_fields, 0, "SP");

gdb/features/aarch64-fpu.c

@@ -8,7 +8,7 @@ create_feature_aarch64_fpu (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.fpu", "aarch64-fpu.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.fpu");
   tdesc_type *element_type;
   element_type = tdesc_named_type (feature, "ieee_double");
   tdesc_create_vector (feature, "v2d", element_type, 2);

gdb/features/i386/32bit-avx.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_avx (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx", "32bit-avx.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx");
   tdesc_create_reg (feature, "ymm0h", regnum++, 1, NULL, 128, "uint128");
   tdesc_create_reg (feature, "ymm1h", regnum++, 1, NULL, 128, "uint128");
   tdesc_create_reg (feature, "ymm2h", regnum++, 1, NULL, 128, "uint128");

gdb/features/i386/32bit-avx512.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_avx512 (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx512", "32bit-avx512.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx512");
   tdesc_type *element_type;
   element_type = tdesc_named_type (feature, "uint128");
   tdesc_create_vector (feature, "v2ui128", element_type, 2);

gdb/features/i386/32bit-core.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_core (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "32bit-core.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");

gdb/features/i386/32bit-linux.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_linux (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux", "32bit-linux.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux");
   regnum = 41;
   tdesc_create_reg (feature, "orig_eax", regnum++, 1, NULL, 32, "int");
   return regnum;

gdb/features/i386/32bit-mpx.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_mpx (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.mpx", "32bit-mpx.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.mpx");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_struct (feature, "br128");
   tdesc_type *field_type;

gdb/features/i386/32bit-pkeys.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_pkeys (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.pkeys", "32bit-pkeys.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.pkeys");
   tdesc_create_reg (feature, "pkru", regnum++, 1, NULL, 32, "uint32");
   return regnum;
 }

gdb/features/i386/32bit-sse.c

@@ -8,7 +8,7 @@ create_feature_i386_32bit_sse (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.sse", "32bit-sse.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.sse");
   tdesc_type *element_type;
   element_type = tdesc_named_type (feature, "ieee_single");
   tdesc_create_vector (feature, "v4f", element_type, 4);

gdb/features/i386/64bit-avx.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_avx (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx", "64bit-avx.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx");
   tdesc_create_reg (feature, "ymm0h", regnum++, 1, NULL, 128, "uint128");
   tdesc_create_reg (feature, "ymm1h", regnum++, 1, NULL, 128, "uint128");
   tdesc_create_reg (feature, "ymm2h", regnum++, 1, NULL, 128, "uint128");

gdb/features/i386/64bit-avx512.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_avx512 (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx512", "64bit-avx512.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx512");
   tdesc_type *element_type;
   element_type = tdesc_named_type (feature, "ieee_single");
   tdesc_create_vector (feature, "v4f", element_type, 4);

gdb/features/i386/64bit-core.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_core (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "64bit-core.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");

gdb/features/i386/64bit-linux.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_linux (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux", "64bit-linux.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux");
   regnum = 57;
   tdesc_create_reg (feature, "orig_rax", regnum++, 1, NULL, 64, "int");
   return regnum;

gdb/features/i386/64bit-mpx.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_mpx (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.mpx", "64bit-mpx.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.mpx");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_struct (feature, "br128");
   tdesc_type *field_type;

gdb/features/i386/64bit-pkeys.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_pkeys (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.pkeys", "64bit-pkeys.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.pkeys");
   tdesc_create_reg (feature, "pkru", regnum++, 1, NULL, 32, "uint32");
   return regnum;
 }

gdb/features/i386/64bit-segments.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_segments (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.segments", "64bit-segments.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.segments");
   tdesc_create_reg (feature, "fs_base", regnum++, 1, NULL, 64, "int");
   tdesc_create_reg (feature, "gs_base", regnum++, 1, NULL, 64, "int");
   return regnum;

gdb/features/i386/64bit-sse.c

@@ -8,7 +8,7 @@ create_feature_i386_64bit_sse (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.sse", "64bit-sse.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.sse");
   tdesc_type *element_type;
   element_type = tdesc_named_type (feature, "ieee_single");
   tdesc_create_vector (feature, "v4f", element_type, 4);

gdb/features/i386/x32-core.c

@@ -8,7 +8,7 @@ create_feature_i386_x32_core (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "x32-core.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core");
   tdesc_type_with_fields *type_with_fields;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");

gdb/features/tic6x-c6xp.c

@@ -8,7 +8,7 @@ create_feature_tic6x_c6xp (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.c6xp", "tic6x-c6xp.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.c6xp");
   tdesc_create_reg (feature, "TSR", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "ILC", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "RILC", regnum++, 1, NULL, 32, "uint32");

gdb/features/tic6x-core.c

@@ -8,7 +8,7 @@ create_feature_tic6x_core (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.core", "tic6x-core.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.core");
   tdesc_create_reg (feature, "A0", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "A1", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "A2", regnum++, 1, NULL, 32, "uint32");

gdb/features/tic6x-gp.c

@@ -8,7 +8,7 @@ create_feature_tic6x_gp (struct target_desc *result, long regnum)
 {
   struct tdesc_feature *feature;
 
-  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.gp", "tic6x-gp.xml");
+  feature = tdesc_create_feature (result, "org.gnu.gdb.tic6x.gp");
   tdesc_create_reg (feature, "A16", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "A17", regnum++, 1, NULL, 32, "uint32");
   tdesc_create_reg (feature, "A18", regnum++, 1, NULL, 32, "uint32");

gdb/gdbserver/Makefile.in

@@ -215,6 +215,7 @@ SFILES = \
 	$(srcdir)/common/print-utils.c \
 	$(srcdir)/common/ptid.c \
 	$(srcdir)/common/rsp-low.c \
+	$(srcdir)/common/tdesc.c \
 	$(srcdir)/common/vec.c \
 	$(srcdir)/common/xml-utils.c \
 	$(srcdir)/nat/linux-btrace.c \
@@ -258,6 +259,7 @@ OBS = \
 	common/rsp-low.o \
 	common/signals.o \
 	common/signals-state-save-restore.o \
+	common/tdesc.o \
 	common/vec.o \
 	common/xml-utils.o \
 	debug.o \
@@ -403,6 +405,7 @@ IPA_OBJS = \
 	common/format-ipa.o \
 	common/print-utils-ipa.o \
 	common/rsp-low-ipa.o \
+	common/tdesc-ipa.o \
 	common/vec-ipa.o \
 	regcache-ipa.o \
 	remote-utils-ipa.o \

gdb/gdbserver/configure.srv

@@ -34,14 +34,6 @@ fi
 
 ipa_ppc_linux_regobj="powerpc-32l-ipa.o powerpc-altivec32l-ipa.o powerpc-cell32l-ipa.o powerpc-vsx32l-ipa.o powerpc-isa205-32l-ipa.o powerpc-isa205-altivec32l-ipa.o powerpc-isa205-vsx32l-ipa.o powerpc-e500l-ipa.o powerpc-64l-ipa.o powerpc-altivec64l-ipa.o powerpc-cell64l-ipa.o powerpc-vsx64l-ipa.o powerpc-isa205-64l-ipa.o powerpc-isa205-altivec64l-ipa.o powerpc-isa205-vsx64l-ipa.o"
 
-srv_i386_32bit_xmlfiles="i386/32bit-core.xml i386/32bit-sse.xml i386/32bit-avx.xml i386/32bit-avx512.xml i386/32bit-mpx.xml i386/32bit-pkeys.xml"
-srv_i386_64bit_xmlfiles="i386/64bit-core.xml i386/64bit-segments.xml i386/64bit-sse.xml i386/64bit-avx.xml i386/64bit-avx512.xml i386/x32-core.xml i386/64bit-mpx.xml i386/64bit-pkeys.xml"
-srv_i386_xmlfiles="i386/i386.xml $srv_i386_32bit_xmlfiles"
-srv_amd64_xmlfiles="i386/amd64.xml $srv_i386_64bit_xmlfiles"
-srv_i386_linux_xmlfiles="i386/32bit-linux.xml $srv_i386_32bit_xmlfiles"
-srv_amd64_linux_xmlfiles="i386/64bit-linux.xml $srv_i386_64bit_xmlfiles"
-
-
 # Linux object files.  This is so we don't have to repeat
 # these files over and over again.
 srv_linux_obj="linux-low.o linux-osdata.o linux-procfs.o linux-ptrace.o linux-waitpid.o linux-personality.o linux-namespaces.o fork-child.o fork-inferior.o"
@@ -63,11 +55,6 @@ case "${target}" in
 			srv_tgtobj="$srv_tgtobj arch/aarch64.o"
 			srv_tgtobj="$srv_tgtobj linux-aarch64-tdesc.o"
 			srv_tgtobj="${srv_tgtobj} $srv_linux_obj"
-			srv_xmlfiles="aarch64.xml"
-			srv_xmlfiles="${srv_xmlfiles} aarch64-core.xml"
-			srv_xmlfiles="${srv_xmlfiles} aarch64-fpu.xml"
-			srv_xmlfiles="${srv_xmlfiles} arm/arm-core.xml arm/arm-vfpv3.xml"
-			srv_xmlfiles="${srv_xmlfiles} arm/arm-with-neon.xml"
 			srv_linux_regsets=yes
 			srv_linux_thread_db=yes
 			ipa_obj="linux-aarch64-ipa.o"
@@ -121,13 +108,10 @@ case "${target}" in
   i[34567]86-*-cygwin*)	srv_regobj=""
 			srv_tgtobj="x86-low.o x86-dregs.o win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/i386.o"
-			srv_xmlfiles="$srv_i386_xmlfiles"
 			;;
   i[34567]86-*-linux*)	srv_regobj="$srv_i386_linux_regobj"
-			srv_xmlfiles="$srv_i386_linux_xmlfiles"
 			if test "$gdb_cv_i386_is_x86_64" = yes ; then
 			    srv_regobj="$srv_regobj $srv_amd64_linux_regobj"
-			    srv_xmlfiles="${srv_xmlfiles} $srv_amd64_linux_xmlfiles"
 			    srv_tgtobj="amd64-linux-siginfo.o"
 			fi
 			srv_tgtobj="${srv_tgtobj} arch/i386.o"
@@ -145,9 +129,6 @@ case "${target}" in
   i[34567]86-*-lynxos*)	srv_regobj=""
 			srv_tgtobj="lynx-low.o lynx-i386-low.o fork-child.o fork-inferior.o"
 			srv_tgtobj="${srv_tgtobj} arch/i386.o"
-			srv_xmlfiles="i386/i386.xml"
-			srv_xmlfiles="${srv_xmlfiles} i386/32bit-core.xml"
-			srv_xmlfiles="${srv_xmlfiles} i386/32bit-sse.xml"
 			srv_lynxos=yes
 			;;
   i[34567]86-*-mingw32ce*)
@@ -155,7 +136,6 @@ case "${target}" in
 			srv_tgtobj="x86-low.o x86-dregs.o win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/i386.o"
 			srv_tgtobj="${srv_tgtobj} wincecompat.o"
-			srv_xmlfiles="$srv_i386_xmlfiles"
 			# hostio_last_error implementation is in win32-low.c
 			srv_hostio_err_objs=""
 			srv_mingw=yes
@@ -164,12 +144,10 @@ case "${target}" in
   i[34567]86-*-mingw*)	srv_regobj=""
 			srv_tgtobj="x86-low.o x86-dregs.o win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/i386.o"
-			srv_xmlfiles="$srv_i386_xmlfiles"
 			srv_mingw=yes
 			;;
   i[34567]86-*-nto*)	srv_regobj=""
 			srv_tgtobj="nto-low.o nto-x86-low.o arch/i386.o"
-			srv_xmlfiles="$srv_i386_xmlfiles"
 			srv_qnx="yes"
 			;;
   ia64-*-linux*)	srv_regobj=reg-ia64.o
@@ -370,9 +348,6 @@ case "${target}" in
                         else
 			  srv_regobj=""
                         fi
-			srv_xmlfiles="${srv_xmlfiles} tic6x-core.xml"
-			srv_xmlfiles="${srv_xmlfiles} tic6x-gp.xml"
-			srv_xmlfiles="${srv_xmlfiles} tic6x-c6xp.xml"
 			srv_tgtobj="$srv_linux_obj linux-tic6x-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/tic6x.o"
 			srv_linux_regsets=yes
@@ -386,7 +361,6 @@ case "${target}" in
 			srv_tgtobj="${srv_tgtobj} linux-btrace.o x86-linux.o"
 			srv_tgtobj="${srv_tgtobj} x86-linux-dregs.o"
 			srv_tgtobj="${srv_tgtobj} amd64-linux-siginfo.o"
-			srv_xmlfiles="$srv_i386_linux_xmlfiles $srv_amd64_linux_xmlfiles"
 			srv_linux_usrregs=yes # This is for i386 progs.
 			srv_linux_regsets=yes
 			srv_linux_thread_db=yes
@@ -397,13 +371,11 @@ case "${target}" in
   x86_64-*-mingw*)	srv_regobj=""
 			srv_tgtobj="x86-low.o x86-dregs.o i387-fp.o win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/amd64.o"
-			srv_xmlfiles="$srv_i386_xmlfiles $srv_amd64_xmlfiles"
 			srv_mingw=yes
 			;;
   x86_64-*-cygwin*)	srv_regobj=""
 			srv_tgtobj="x86-low.o x86-dregs.o i387-fp.o win32-low.o win32-i386-low.o"
 			srv_tgtobj="${srv_tgtobj} arch/amd64.o"
-			srv_xmlfiles="$srv_i386_xmlfiles"
 			;;
 
   xtensa*-*-linux*)	srv_regobj=reg-xtensa.o

gdb/gdbserver/regcache.c

@@ -196,6 +196,13 @@ regcache_cpy (struct regcache *dst, struct regcache *src)
   dst->registers_valid = src->registers_valid;
 }
 
+/* Return a reference to the description of register ``n''.  */
+
+static const struct reg &
+find_register_by_number (const struct target_desc *tdesc, int n)
+{
+  return tdesc->reg_defs[n];
+}
 
 #ifndef IN_PROCESS_AGENT
 
@@ -243,25 +250,13 @@ int
 find_regno (const struct target_desc *tdesc, const char *name)
 {
   for (int i = 0; i < tdesc->reg_defs.size (); ++i)
-    {
-      struct reg *reg = tdesc->reg_defs[i];
+    if (strcmp (name, find_register_by_number (tdesc, i).name) == 0)
+      return i;
 
-      if (strcmp (name, reg->name) == 0)
-	return i;
-    }
   internal_error (__FILE__, __LINE__, "Unknown register %s requested",
 		  name);
 }
 
-#endif
-
-struct reg *
-find_register_by_number (const struct target_desc *tdesc, int n)
-{
-  return tdesc->reg_defs[n];
-}
-
-#ifndef IN_PROCESS_AGENT
 static void
 free_register_cache_thread (struct thread_info *thread)
 {
@@ -292,7 +287,7 @@ register_cache_size (const struct target_desc *tdesc)
 int
 register_size (const struct target_desc *tdesc, int n)
 {
-  return find_register_by_number (tdesc, n)->size / 8;
+  return find_register_by_number (tdesc, n).size / 8;
 }
 
 /* See common/common-regcache.h.  */
@@ -307,7 +302,7 @@ static unsigned char *
 register_data (struct regcache *regcache, int n, int fetch)
 {
   return (regcache->registers
-	  + find_register_by_number (regcache->tdesc, n)->offset / 8);
+	  + find_register_by_number (regcache->tdesc, n).offset / 8);
 }
 
 /* Supply register N, whose contents are stored in BUF, to REGCACHE.

gdb/gdbserver/regcache.h

@@ -94,10 +94,6 @@ void registers_from_string (struct regcache *regcache, char *buf);
 
 void regcache_write_pc (struct regcache *regcache, CORE_ADDR pc);
 
-/* Return a pointer to the description of register ``n''.  */
-
-struct reg *find_register_by_number (const struct target_desc *tdesc, int n);
-
 int register_cache_size (const struct target_desc *tdesc);
 
 int register_size (const struct target_desc *tdesc, int n);

gdb/gdbserver/tdesc.c

@@ -19,16 +19,91 @@
 #include "tdesc.h"
 #include "regdef.h"
 
+#ifndef IN_PROCESS_AGENT
+
+target_desc::~target_desc ()
+{
+  xfree ((char *) arch);
+  xfree ((char *) osabi);
+}
+
+bool target_desc::operator== (const target_desc &other) const
+{
+  if (reg_defs.size () != other.reg_defs.size ())
+    return false;
+
+  for (int i = 0; i < reg_defs.size (); ++i)
+    {
+      struct reg reg = reg_defs[i];
+      struct reg reg2 = other.reg_defs[i];
+
+      if (&reg != &reg2 && reg != reg2)
+	return false;
+    }
+
+  /* Compare expedite_regs.  */
+  int i = 0;
+  for (; expedite_regs[i] != NULL; i++)
+    {
+      if (strcmp (expedite_regs[i], other.expedite_regs[i]) != 0)
+	return false;
+    }
+  if (other.expedite_regs[i] != NULL)
+    return false;
+
+  return true;
+}
+
+#endif
+
+void target_desc::accept (tdesc_element_visitor &v) const
+{
+#ifndef IN_PROCESS_AGENT
+  v.visit_pre (this);
+
+  for (const tdesc_feature_up &feature : features)
+    feature->accept (v);
+
+  v.visit_post (this);
+#endif
+}
+
 void
 init_target_desc (struct target_desc *tdesc)
 {
   int offset = 0;
 
-  for (reg *reg : tdesc->reg_defs)
-    {
-      reg->offset = offset;
-      offset += reg->size;
-    }
+  /* Go through all the features and populate reg_defs.  */
+  for (const tdesc_feature_up &feature : tdesc->features)
+    for (const tdesc_reg_up &treg : feature->registers)
+      {
+	int current_size = tdesc->reg_defs.size ();
+
+	/* Register number will either increase (possibly with gaps) or be
+	   zero.  */
+	gdb_assert (treg->target_regnum == 0
+		    || treg->target_regnum >= current_size);
+
+	tdesc->reg_defs.resize (treg->target_regnum != 0
+				? treg->target_regnum + 1
+				: current_size + 1);
+
+	/* Fill in any blank spaces.  */
+	while (current_size < treg->target_regnum)
+	  {
+	    struct reg *reg = &tdesc->reg_defs[current_size];
+	    reg->name = "";
+	    reg->size = 0;
+	    reg->offset = offset;
+	    current_size++;
+	  }
+
+	struct reg *reg = &tdesc->reg_defs.back ();
+	reg->name = treg->name.c_str ();
+	reg->size = treg->bitsize;
+	reg->offset = offset;
+	offset += reg->size;
+      }
 
   tdesc->registers_size = offset / 8;
 
@@ -68,6 +143,14 @@ current_target_desc (void)
 
 /* See common/tdesc.h.  */
 
+const char *
+tdesc_architecture_name (const struct target_desc *target_desc)
+{
+  return target_desc->arch;
+}
+
+/* See common/tdesc.h.  */
+
 void
 set_tdesc_architecture (struct target_desc *target_desc,
 			const char *name)
@@ -77,51 +160,35 @@ set_tdesc_architecture (struct target_desc *target_desc,
 
 /* See common/tdesc.h.  */
 
+const char *
+tdesc_osabi_name (const struct target_desc *target_desc)
+{
+  return target_desc->osabi;
+}
+
+/* See common/tdesc.h.  */
+
 void
 set_tdesc_osabi (struct target_desc *target_desc, const char *name)
 {
   target_desc->osabi = xstrdup (name);
 }
 
-/* Return a string which is of XML format, including XML target
-   description to be sent to GDB.  */
+/* See common/tdesc.h.  */
 
 const char *
 tdesc_get_features_xml (target_desc *tdesc)
 {
   /* Either .xmltarget or .features is not NULL.  */
   gdb_assert (tdesc->xmltarget != NULL
-	      || (tdesc->features != NULL
+	      || (!tdesc->features.empty ()
 		  && tdesc->arch != NULL));
 
   if (tdesc->xmltarget == NULL)
     {
-      std::string buffer ("@<?xml version=\"1.0\"?>");
-
-      buffer += "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">";
-      buffer += "<target>";
-      buffer += "<architecture>";
-      buffer += tdesc->arch;
-      buffer += "</architecture>";
-
-      if (tdesc->osabi != nullptr)
-	{
-	  buffer += "<osabi>";
-	  buffer += tdesc->osabi;
-	  buffer += "</osabi>";
-	}
-
-      char *xml;
-
-      for (int i = 0; VEC_iterate (char_ptr, tdesc->features, i, xml); i++)
-	{
-	  buffer += "<xi:include href=\"";
-	  buffer += xml;
-	  buffer += "\"/>";
-	}
-
-      buffer += "</target>";
-
+      std::string buffer ("@");
+      print_xml_feature v (buffer);
+      tdesc->accept (v);
       tdesc->xmltarget = xstrdup (buffer.c_str ());
     }
 
@@ -129,113 +196,12 @@ tdesc_get_features_xml (target_desc *tdesc)
 }
 #endif
 
-struct tdesc_type
-{};
-
 /* See common/tdesc.h.  */
 
 struct tdesc_feature *
-tdesc_create_feature (struct target_desc *tdesc, const char *name,
-		      const char *xml)
-{
-#ifndef IN_PROCESS_AGENT
-  VEC_safe_push (char_ptr, tdesc->features, xstrdup (xml));
-#endif
-  return tdesc;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_flags (struct tdesc_feature *feature, const char *name,
-		    int size)
-{
-  return NULL;
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_add_flag (tdesc_type_with_fields *type, int start,
-		const char *flag_name)
-{}
-
-/* See common/tdesc.h.  */
-
-struct tdesc_type *
-tdesc_named_type (const struct tdesc_feature *feature, const char *id)
-{
-  return NULL;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_union (struct tdesc_feature *feature, const char *id)
-{
-  return NULL;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_struct (struct tdesc_feature *feature, const char *id)
-{
-  return NULL;
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_create_reg (struct tdesc_feature *feature, const char *name,
-		  int regnum, int save_restore, const char *group,
-		  int bitsize, const char *type)
-{
-  struct target_desc *tdesc = (struct target_desc *) feature;
-
-  while (tdesc->reg_defs.size () < regnum)
-    {
-      struct reg *reg = XCNEW (struct reg);
-
-      reg->name = "";
-      reg->size = 0;
-      tdesc->reg_defs.push_back (reg);
-    }
-
-  gdb_assert (regnum == 0
-	      || regnum == tdesc->reg_defs.size ());
-
-  struct reg *reg = XCNEW (struct reg);
-
-  reg->name = name;
-  reg->size = bitsize;
-  tdesc->reg_defs.push_back (reg);
-}
-
-/* See common/tdesc.h.  */
-
-struct tdesc_type *
-tdesc_create_vector (struct tdesc_feature *feature, const char *name,
-		     struct tdesc_type *field_type, int count)
-{
-  return NULL;
-}
-
-void
-tdesc_add_bitfield (tdesc_type_with_fields *type, const char *field_name,
-		    int start, int end)
-{}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_add_field (tdesc_type_with_fields *type, const char *field_name,
-		 struct tdesc_type *field_type)
-{}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_set_struct_size (tdesc_type_with_fields *type, int size)
+tdesc_create_feature (struct target_desc *tdesc, const char *name)
 {
+  struct tdesc_feature *new_feature = new tdesc_feature (name);
+  tdesc->features.emplace_back (new_feature);
+  return new_feature;
 }

gdb/gdbserver/tdesc.h

@@ -24,21 +24,21 @@
 #include "regdef.h"
 #include <vector>
 
-struct tdesc_feature
-{};
-
 /* A target description.  Inherit from tdesc_feature so that target_desc
    can be used as tdesc_feature.  */
 
-struct target_desc : tdesc_feature
+struct target_desc : tdesc_element
 {
   /* A vector of elements of register definitions that
      describe the inferior's register set.  */
-  std::vector<struct reg *> reg_defs;
+  std::vector<struct reg> reg_defs;
 
   /* The register cache size, in bytes.  */
   int registers_size;
 
+  /* XML features in this target description.  */
+  std::vector<tdesc_feature_up> features;
+
 #ifndef IN_PROCESS_AGENT
   /* An array of register names.  These are the "expedite" registers:
      registers whose values are sent along with stop replies.  */
@@ -53,9 +53,6 @@ struct target_desc : tdesc_feature
      fields features, arch, and osabi in tdesc_get_features_xml.  */
   const char *xmltarget = NULL;
 
-  /* XML features in this target description.  */
-  VEC (char_ptr) *features = NULL;
-
   /* The value of <architecture> element in the XML, replying GDB.  */
   const char *arch = NULL;
 
@@ -67,55 +64,17 @@ public:
     : registers_size (0)
   {}
 
-  ~target_desc ()
-  {
-    int i;
+  ~target_desc ();
 
-    for (reg *reg : reg_defs)
-      xfree (reg);
-
-    xfree ((char *) arch);
-    xfree ((char *) osabi);
-
-    char *f;
-
-    for (i = 0; VEC_iterate (char_ptr, features, i, f); i++)
-      xfree (f);
-    VEC_free (char_ptr, features);
-  }
-
-  bool operator== (const target_desc &other) const
-  {
-    if (reg_defs.size () != other.reg_defs.size ())
-      return false;
-
-    for (int i = 0; i < reg_defs.size (); ++i)
-      {
-	struct reg *reg = reg_defs[i];
-	struct reg *reg2 = other.reg_defs[i];
-
-	if (reg != reg2 && *reg != *reg2)
-	  return false;
-      }
-
-    /* Compare expedite_regs.  */
-    int i = 0;
-    for (; expedite_regs[i] != NULL; i++)
-      {
-	if (strcmp (expedite_regs[i], other.expedite_regs[i]) != 0)
-	  return false;
-      }
-    if (other.expedite_regs[i] != NULL)
-      return false;
-
-    return true;
-  }
+  bool operator== (const target_desc &other) const;
 
   bool operator!= (const target_desc &other) const
   {
     return !(*this == other);
   }
 #endif
+
+  void accept (tdesc_element_visitor &v) const;
 };
 
 /* Copy target description SRC to DEST.  */

gdb/regformats/aarch64.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: aarch64.xml
 name:aarch64
+feature:1
 xmltarget:aarch64.xml
 expedite:x29,sp,pc
 64:x0

gdb/regformats/i386/amd64-avx-avx512-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-avx-avx512-linux.xml
 name:amd64_avx_avx512_linux
+feature:1
 xmltarget:amd64-avx-avx512-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64-avx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-avx-linux.xml
 name:amd64_avx_linux
+feature:1
 xmltarget:amd64-avx-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64-avx-mpx-avx512-pku-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-avx-mpx-avx512-pku-linux.xml
 name:amd64_avx_mpx_avx512_pku_linux
+feature:1
 xmltarget:amd64-avx-mpx-avx512-pku-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64-avx-mpx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-avx-mpx-linux.xml
 name:amd64_avx_mpx_linux
+feature:1
 xmltarget:amd64-avx-mpx-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-linux.xml
 name:amd64_linux
+feature:1
 xmltarget:amd64-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64-mpx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64-mpx-linux.xml
 name:amd64_mpx_linux
+feature:1
 xmltarget:amd64-mpx-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/amd64.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/amd64.xml
 name:amd64
+feature:1
 xmltarget:amd64.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/i386-avx-avx512-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-avx-avx512-linux.xml
 name:i386_avx_avx512_linux
+feature:1
 xmltarget:i386-avx-avx512-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-avx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-avx-linux.xml
 name:i386_avx_linux
+feature:1
 xmltarget:i386-avx-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-avx-mpx-avx512-pku-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-avx-mpx-avx512-pku-linux.xml
 name:i386_avx_mpx_avx512_pku_linux
+feature:1
 xmltarget:i386-avx-mpx-avx512-pku-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-avx-mpx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-avx-mpx-linux.xml
 name:i386_avx_mpx_linux
+feature:1
 xmltarget:i386-avx-mpx-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-linux.xml
 name:i386_linux
+feature:1
 xmltarget:i386-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-mmx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-mmx-linux.xml
 name:i386_mmx_linux
+feature:1
 xmltarget:i386-mmx-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386-mpx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386-mpx-linux.xml
 name:i386_mpx_linux
+feature:1
 xmltarget:i386-mpx-linux.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/i386.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/i386.xml
 name:i386
+feature:1
 xmltarget:i386.xml
 expedite:ebp,esp,eip
 32:eax

gdb/regformats/i386/x32-avx-avx512-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/x32-avx-avx512-linux.xml
 name:x32_avx_avx512_linux
+feature:1
 xmltarget:x32-avx-avx512-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/x32-avx-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/x32-avx-linux.xml
 name:x32_avx_linux
+feature:1
 xmltarget:x32-avx-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/i386/x32-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: i386/x32-linux.xml
 name:x32_linux
+feature:1
 xmltarget:x32-linux.xml
 expedite:rbp,rsp,rip
 64:rax

gdb/regformats/regdat.sh

@@ -118,6 +118,7 @@ xmltarget=x
 xmlarch=x
 xmlosabi=x
 expedite=x
+feature=x
 exec < $1
 while do_read
 do
@@ -131,7 +132,7 @@ do
     echo "{"
     echo "  static struct target_desc tdesc_${name}_s;"
     echo "  struct target_desc *result = &tdesc_${name}_s;"
-
+    echo "  struct tdesc_feature *feature = tdesc_create_feature (result, \"${name}\");"
     continue
   elif test "${type}" = "xmltarget"; then
     xmltarget="${entry}"
@@ -145,11 +146,14 @@ do
   elif test "${type}" = "expedite"; then
     expedite="${entry}"
     continue
+  elif test "${type}" = "feature"; then
+    feature="${entry}"
+    continue
   elif test "${name}" = x; then
     echo "$0: $1 does not specify \`\`name''." 1>&2
     exit 1
   else
-    echo "  tdesc_create_reg ((struct tdesc_feature *) result, \"${entry}\","
+    echo "  tdesc_create_reg (feature, \"${entry}\","
     echo "  0, 0, NULL, ${type}, NULL);"
 
     offset=`expr ${offset} + ${type}`
@@ -159,7 +163,9 @@ done
 
 echo
 echo "static const char *expedite_regs_${name}[] = { \"`echo ${expedite} | sed 's/,/", "/g'`\", 0 };"
-if test "${xmltarget}" = x; then
+if test "${feature}" != x; then
+  echo "static const char *xmltarget_${name} = 0;"
+elif test "${xmltarget}" = x; then
   if test "${xmlarch}" = x && test "${xmlosabi}" = x; then
     echo "static const char *xmltarget_${name} = 0;"
   else

gdb/regformats/tic6x-c62x-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: tic6x-c62x-linux.xml
 name:tic6x_c62x_linux
+feature:1
 xmltarget:tic6x-c62x-linux.xml
 expedite:A15,PC
 32:A0

gdb/regformats/tic6x-c64x-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: tic6x-c64x-linux.xml
 name:tic6x_c64x_linux
+feature:1
 xmltarget:tic6x-c64x-linux.xml
 expedite:A15,PC
 32:A0

gdb/regformats/tic6x-c64xp-linux.dat

@@ -1,6 +1,7 @@
 # THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi :set ro:
 # Generated from: tic6x-c64xp-linux.xml
 name:tic6x_c64xp_linux
+feature:1
 xmltarget:tic6x-c64xp-linux.xml
 expedite:A15,PC
 32:A0

gdb/target-descriptions.c

@@ -38,44 +38,6 @@
 #include "completer.h"
 #include "readline/tilde.h" /* tilde_expand */
 
-static type *make_gdb_type (struct gdbarch *gdbarch, struct tdesc_type *ttype);
-
-/* The interface to visit different elements of target description.  */
-
-class tdesc_element_visitor
-{
-public:
-  virtual void visit_pre (const target_desc *e)
-  {}
-
-  virtual void visit_post (const target_desc *e)
-  {}
-
-  virtual void visit_pre (const tdesc_feature *e)
-  {}
-
-  virtual void visit_post (const tdesc_feature *e)
-  {}
-
-  virtual void visit (const tdesc_type_builtin *e)
-  {}
-
-  virtual void visit (const tdesc_type_vector *e)
-  {}
-
-  virtual void visit (const tdesc_type_with_fields *e)
-  {}
-
-  virtual void visit (const tdesc_reg *e)
-  {}
-};
-
-class tdesc_element
-{
-public:
-  virtual void accept (tdesc_element_visitor &v) const = 0;
-};
-
 /* Types.  */
 
 struct property
@@ -88,207 +50,6 @@ struct property
   std::string value;
 };
 
-/* An individual register from a target description.  */
-
-struct tdesc_reg : tdesc_element
-{
-  tdesc_reg (struct tdesc_feature *feature, const std::string &name_,
-	     int regnum, int save_restore_, const char *group_,
-	     int bitsize_, const char *type_)
-    : name (name_), target_regnum (regnum),
-      save_restore (save_restore_),
-      group (group_ != NULL ? group_ : ""),
-      bitsize (bitsize_),
-      type (type_ != NULL ? type_ : "<unknown>")
-  {
-    /* If the register's type is target-defined, look it up now.  We may not
-       have easy access to the containing feature when we want it later.  */
-    tdesc_type = tdesc_named_type (feature, type.c_str ());
-  }
-
-  virtual ~tdesc_reg () = default;
-
-  DISABLE_COPY_AND_ASSIGN (tdesc_reg);
-
-  /* The name of this register.  In standard features, it may be
-     recognized by the architecture support code, or it may be purely
-     for the user.  */
-  std::string name;
-
-  /* The register number used by this target to refer to this
-     register.  This is used for remote p/P packets and to determine
-     the ordering of registers in the remote g/G packets.  */
-  long target_regnum;
-
-  /* If this flag is set, GDB should save and restore this register
-     around calls to an inferior function.  */
-  int save_restore;
-
-  /* The name of the register group containing this register, or empty
-     if the group should be automatically determined from the register's
-     type.  This is traditionally "general", "float", "vector" but can
-     also be an arbitrary string.  If defined the corresponding "info"
-     command should display this register's value.  The string should be
-     limited to alphanumeric characters and internal hyphens.  */
-  std::string group;
-
-  /* The size of the register, in bits.  */
-  int bitsize;
-
-  /* The type of the register.  This string corresponds to either
-     a named type from the target description or a predefined
-     type from GDB.  */
-  std::string type;
-
-  /* The target-described type corresponding to TYPE, if found.  */
-  struct tdesc_type *tdesc_type;
-
-  void accept (tdesc_element_visitor &v) const override
-  {
-    v.visit (this);
-  }
-
-  bool operator== (const tdesc_reg &other) const
-  {
-    return (name == other.name
-	    && target_regnum == other.target_regnum
-	    && save_restore == other.save_restore
-	    && bitsize == other.bitsize
-	    && group == other.group
-	    && type == other.type);
-  }
-
-  bool operator!= (const tdesc_reg &other) const
-  {
-    return !(*this == other);
-  }
-};
-
-typedef std::unique_ptr<tdesc_reg> tdesc_reg_up;
-
-/* A named type from a target description.  */
-
-struct tdesc_type_field
-{
-  tdesc_type_field (const std::string &name_, tdesc_type *type_,
-		    int start_, int end_)
-  : name (name_), type (type_), start (start_), end (end_)
-  {}
-
-  std::string name;
-  struct tdesc_type *type;
-  /* For non-enum-values, either both are -1 (non-bitfield), or both are
-     not -1 (bitfield).  For enum values, start is the value (which could be
-     -1), end is -1.  */
-  int start, end;
-};
-
-enum tdesc_type_kind
-{
-  /* Predefined types.  */
-  TDESC_TYPE_BOOL,
-  TDESC_TYPE_INT8,
-  TDESC_TYPE_INT16,
-  TDESC_TYPE_INT32,
-  TDESC_TYPE_INT64,
-  TDESC_TYPE_INT128,
-  TDESC_TYPE_UINT8,
-  TDESC_TYPE_UINT16,
-  TDESC_TYPE_UINT32,
-  TDESC_TYPE_UINT64,
-  TDESC_TYPE_UINT128,
-  TDESC_TYPE_CODE_PTR,
-  TDESC_TYPE_DATA_PTR,
-  TDESC_TYPE_IEEE_SINGLE,
-  TDESC_TYPE_IEEE_DOUBLE,
-  TDESC_TYPE_ARM_FPA_EXT,
-  TDESC_TYPE_I387_EXT,
-
-  /* Types defined by a target feature.  */
-  TDESC_TYPE_VECTOR,
-  TDESC_TYPE_STRUCT,
-  TDESC_TYPE_UNION,
-  TDESC_TYPE_FLAGS,
-  TDESC_TYPE_ENUM
-};
-
-struct tdesc_type : tdesc_element
-{
-  tdesc_type (const std::string &name_, enum tdesc_type_kind kind_)
-    : name (name_), kind (kind_)
-  {}
-
-  virtual ~tdesc_type () = default;
-
-  DISABLE_COPY_AND_ASSIGN (tdesc_type);
-
-  /* The name of this type.   */
-  std::string name;
-
-  /* Identify the kind of this type.  */
-  enum tdesc_type_kind kind;
-
-  bool operator== (const tdesc_type &other) const
-  {
-    return name == other.name && kind == other.kind;
-  }
-
-  bool operator!= (const tdesc_type &other) const
-  {
-    return !(*this == other);
-  }
-};
-
-typedef std::unique_ptr<tdesc_type> tdesc_type_up;
-
-struct tdesc_type_builtin : tdesc_type
-{
-  tdesc_type_builtin (const std::string &name, enum tdesc_type_kind kind)
-  : tdesc_type (name, kind)
-  {}
-
-  void accept (tdesc_element_visitor &v) const override
-  {
-    v.visit (this);
-  }
-};
-
-/* tdesc_type for vector types.  */
-
-struct tdesc_type_vector : tdesc_type
-{
-  tdesc_type_vector (const std::string &name, tdesc_type *element_type_, int count_)
-  : tdesc_type (name, TDESC_TYPE_VECTOR),
-    element_type (element_type_), count (count_)
-  {}
-
-  void accept (tdesc_element_visitor &v) const override
-  {
-    v.visit (this);
-  }
-
-  struct tdesc_type *element_type;
-  int count;
-};
-
-/* tdesc_type for struct, union, flags, and enum types.  */
-
-struct tdesc_type_with_fields : tdesc_type
-{
-  tdesc_type_with_fields (const std::string &name, tdesc_type_kind kind,
-			  int size_ = 0)
-  : tdesc_type (name, kind), size (size_)
-  {}
-
-  void accept (tdesc_element_visitor &v) const override
-  {
-    v.visit (this);
-  }
-
-  std::vector<tdesc_type_field> fields;
-  int size;
-};
-
 /* Convert a tdesc_type to a gdb type.  */
 
 static type *
@@ -544,82 +305,6 @@ make_gdb_type (struct gdbarch *gdbarch, struct tdesc_type *ttype)
   return gdb_type.get_type ();
 }
 
-/* A feature from a target description.  Each feature is a collection
-   of other elements, e.g. registers and types.  */
-
-struct tdesc_feature : tdesc_element
-{
-  tdesc_feature (const std::string &name_)
-    : name (name_)
-  {}
-
-  virtual ~tdesc_feature () = default;
-
-  DISABLE_COPY_AND_ASSIGN (tdesc_feature);
-
-  /* The name of this feature.  It may be recognized by the architecture
-     support code.  */
-  std::string name;
-
-  /* The registers associated with this feature.  */
-  std::vector<tdesc_reg_up> registers;
-
-  /* The types associated with this feature.  */
-  std::vector<tdesc_type_up> types;
-
-  void accept (tdesc_element_visitor &v) const override
-  {
-    v.visit_pre (this);
-
-    for (const tdesc_type_up &type : types)
-      type->accept (v);
-
-    for (const tdesc_reg_up &reg : registers)
-      reg->accept (v);
-
-    v.visit_post (this);
-  }
-
-  bool operator== (const tdesc_feature &other) const
-  {
-    if (name != other.name)
-      return false;
-
-    if (registers.size () != other.registers.size ())
-      return false;
-
-    for (int ix = 0; ix < registers.size (); ix++)
-      {
-	const tdesc_reg_up &reg1 = registers[ix];
-	const tdesc_reg_up &reg2 = other.registers[ix];
-
-	if (reg1 != reg2 && *reg1 != *reg2)
-	  return false;
-      }
-
-    if (types.size () != other.types.size ())
-      return false;
-
-    for (int ix = 0; ix < types.size (); ix++)
-      {
-	const tdesc_type_up &type1 = types[ix];
-	const tdesc_type_up &type2 = other.types[ix];
-
-	if (type1 != type2 && *type1 != *type2)
-	  return false;
-      }
-
-    return true;
-  }
-
-  bool operator!= (const tdesc_feature &other) const
-  {
-    return !(*this == other);
-  }
-};
-
-typedef std::unique_ptr<tdesc_feature> tdesc_feature_up;
-
 /* A target description.  */
 
 struct target_desc : tdesc_element
@@ -648,6 +333,8 @@ struct target_desc : tdesc_element
   /* The features associated with this target.  */
   std::vector<tdesc_feature_up> features;
 
+  char *xmltarget = nullptr;
+
   void accept (tdesc_element_visitor &v) const override
   {
     v.visit_pre (this);
@@ -943,6 +630,14 @@ tdesc_architecture (const struct target_desc *target_desc)
   return target_desc->arch;
 }
 
+/* See common/tdesc.h.  */
+
+const char *
+tdesc_architecture_name (const struct target_desc *target_desc)
+{
+  return target_desc->arch->printable_name;
+}
+
 /* Return the OSABI associated with this target description, or
    GDB_OSABI_UNKNOWN if no osabi was specified.  */
 
@@ -952,7 +647,16 @@ tdesc_osabi (const struct target_desc *target_desc)
   return target_desc->osabi;
 }
 
-
+/* See common/tdesc.h.  */
+
+const char *
+tdesc_osabi_name (const struct target_desc *target_desc)
+{
+  enum gdb_osabi osabi = tdesc_osabi (target_desc);
+  if (osabi > GDB_OSABI_UNKNOWN && osabi < GDB_OSABI_INVALID)
+    return gdbarch_osabi_name (osabi);
+  return nullptr;
+}
 
 /* Return 1 if this target description includes any registers.  */
 
@@ -991,58 +695,6 @@ tdesc_feature_name (const struct tdesc_feature *feature)
   return feature->name.c_str ();
 }
 
-/* Predefined types.  */
-static tdesc_type_builtin tdesc_predefined_types[] =
-{
-  { "bool", TDESC_TYPE_BOOL },
-  { "int8", TDESC_TYPE_INT8 },
-  { "int16", TDESC_TYPE_INT16 },
-  { "int32", TDESC_TYPE_INT32 },
-  { "int64", TDESC_TYPE_INT64 },
-  { "int128", TDESC_TYPE_INT128 },
-  { "uint8", TDESC_TYPE_UINT8 },
-  { "uint16", TDESC_TYPE_UINT16 },
-  { "uint32", TDESC_TYPE_UINT32 },
-  { "uint64", TDESC_TYPE_UINT64 },
-  { "uint128", TDESC_TYPE_UINT128 },
-  { "code_ptr", TDESC_TYPE_CODE_PTR },
-  { "data_ptr", TDESC_TYPE_DATA_PTR },
-  { "ieee_single", TDESC_TYPE_IEEE_SINGLE },
-  { "ieee_double", TDESC_TYPE_IEEE_DOUBLE },
-  { "arm_fpa_ext", TDESC_TYPE_ARM_FPA_EXT },
-  { "i387_ext", TDESC_TYPE_I387_EXT }
-};
-
-/* Lookup a predefined type.  */
-
-static struct tdesc_type *
-tdesc_predefined_type (enum tdesc_type_kind kind)
-{
-  for (int ix = 0; ix < ARRAY_SIZE (tdesc_predefined_types); ix++)
-    if (tdesc_predefined_types[ix].kind == kind)
-      return &tdesc_predefined_types[ix];
-
-  gdb_assert_not_reached ("bad predefined tdesc type");
-}
-
-/* See common/tdesc.h.  */
-
-struct tdesc_type *
-tdesc_named_type (const struct tdesc_feature *feature, const char *id)
-{
-  /* First try target-defined types.  */
-  for (const tdesc_type_up &type : feature->types)
-    if (type->name == id)
-      return type.get ();
-
-  /* Next try the predefined types.  */
-  for (int ix = 0; ix < ARRAY_SIZE (tdesc_predefined_types); ix++)
-    if (tdesc_predefined_types[ix].name == id)
-      return &tdesc_predefined_types[ix];
-
-  return NULL;
-}
-
 /* Lookup type associated with ID.  */
 
 struct type *
@@ -1474,167 +1126,11 @@ tdesc_use_registers (struct gdbarch *gdbarch,
 				      tdesc_remote_register_number);
   set_gdbarch_register_reggroup_p (gdbarch, tdesc_register_reggroup_p);
 }
-
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_create_reg (struct tdesc_feature *feature, const char *name,
-		  int regnum, int save_restore, const char *group,
-		  int bitsize, const char *type)
-{
-  tdesc_reg *reg = new tdesc_reg (feature, name, regnum, save_restore,
-				  group, bitsize, type);
-
-  feature->registers.emplace_back (reg);
-}
-
-/* See common/tdesc.h.  */
-
-struct tdesc_type *
-tdesc_create_vector (struct tdesc_feature *feature, const char *name,
-		     struct tdesc_type *field_type, int count)
-{
-  tdesc_type_vector *type = new tdesc_type_vector (name, field_type, count);
-  feature->types.emplace_back (type);
-
-  return type;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_struct (struct tdesc_feature *feature, const char *name)
-{
-  tdesc_type_with_fields *type
-    = new tdesc_type_with_fields (name, TDESC_TYPE_STRUCT);
-  feature->types.emplace_back (type);
-
-  return type;
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_set_struct_size (tdesc_type_with_fields *type, int size)
-{
-  gdb_assert (type->kind == TDESC_TYPE_STRUCT);
-  gdb_assert (size > 0);
-  type->size = size;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_union (struct tdesc_feature *feature, const char *name)
-{
-  tdesc_type_with_fields *type
-    = new tdesc_type_with_fields (name, TDESC_TYPE_UNION);
-  feature->types.emplace_back (type);
-
-  return type;
-}
-
-/* See common/tdesc.h.  */
-
-tdesc_type_with_fields *
-tdesc_create_flags (struct tdesc_feature *feature, const char *name,
-		    int size)
-{
-  gdb_assert (size > 0);
-
-  tdesc_type_with_fields *type
-    = new tdesc_type_with_fields (name, TDESC_TYPE_FLAGS, size);
-  feature->types.emplace_back (type);
-
-  return type;
-}
-
-tdesc_type_with_fields *
-tdesc_create_enum (struct tdesc_feature *feature, const char *name,
-		   int size)
-{
-  gdb_assert (size > 0);
-
-  tdesc_type_with_fields *type
-    = new tdesc_type_with_fields (name, TDESC_TYPE_ENUM, size);
-  feature->types.emplace_back (type);
-
-  return type;
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_add_field (tdesc_type_with_fields *type, const char *field_name,
-		 struct tdesc_type *field_type)
-{
-  gdb_assert (type->kind == TDESC_TYPE_UNION
-	      || type->kind == TDESC_TYPE_STRUCT);
-
-  /* Initialize start and end so we know this is not a bit-field
-     when we print-c-tdesc.  */
-  type->fields.emplace_back (field_name, field_type, -1, -1);
-}
-
-void
-tdesc_add_typed_bitfield (tdesc_type_with_fields *type, const char *field_name,
-			  int start, int end, struct tdesc_type *field_type)
-{
-  gdb_assert (type->kind == TDESC_TYPE_STRUCT
-	      || type->kind == TDESC_TYPE_FLAGS);
-  gdb_assert (start >= 0 && end >= start);
-
-  type->fields.emplace_back (field_name, field_type, start, end);
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_add_bitfield (tdesc_type_with_fields *type, const char *field_name,
-		    int start, int end)
-{
-  struct tdesc_type *field_type;
-
-  gdb_assert (start >= 0 && end >= start);
-
-  if (type->size > 4)
-    field_type = tdesc_predefined_type (TDESC_TYPE_UINT64);
-  else
-    field_type = tdesc_predefined_type (TDESC_TYPE_UINT32);
-
-  tdesc_add_typed_bitfield (type, field_name, start, end, field_type);
-}
-
-/* See common/tdesc.h.  */
-
-void
-tdesc_add_flag (tdesc_type_with_fields *type, int start,
-		const char *flag_name)
-{
-  gdb_assert (type->kind == TDESC_TYPE_FLAGS
-	      || type->kind == TDESC_TYPE_STRUCT);
-
-  type->fields.emplace_back (flag_name,
-			     tdesc_predefined_type (TDESC_TYPE_BOOL),
-			     start, start);
-}
-
-void
-tdesc_add_enum_value (tdesc_type_with_fields *type, int value,
-		      const char *name)
-{
-  gdb_assert (type->kind == TDESC_TYPE_ENUM);
-  type->fields.emplace_back (name,
-			     tdesc_predefined_type (TDESC_TYPE_INT32),
-			     value, -1);
-}
 
 /* See common/tdesc.h.  */
 
 struct tdesc_feature *
-tdesc_create_feature (struct target_desc *tdesc, const char *name,
-		      const char *xml)
+tdesc_create_feature (struct target_desc *tdesc, const char *name)
 {
   struct tdesc_feature *new_feature = new tdesc_feature (name);
 
@@ -2102,8 +1598,8 @@ public:
     printf_unfiltered ("  struct tdesc_feature *feature;\n");
 
     printf_unfiltered
-      ("\n  feature = tdesc_create_feature (result, \"%s\", \"%s\");\n",
-       e->name.c_str (), lbasename (m_filename_after_features.c_str ()));
+      ("\n  feature = tdesc_create_feature (result, \"%s\");\n",
+       e->name.c_str ());
   }
 
   void visit_post (const tdesc_feature *e) override
@@ -2172,6 +1668,21 @@ private:
   int m_next_regnum = 0;
 };
 
+/* See common/tdesc.h.  */
+
+const char *
+tdesc_get_features_xml (target_desc *tdesc)
+{
+  if (tdesc->xmltarget == nullptr)
+    {
+      std::string buffer ("@");
+      print_xml_feature v (buffer);
+      tdesc->accept (v);
+      tdesc->xmltarget = xstrdup (buffer.c_str ());
+    }
+  return tdesc->xmltarget;
+}
+
 static void
 maint_print_c_tdesc_cmd (const char *args, int from_tty)
 {
@@ -2265,7 +1776,36 @@ maintenance_check_xml_descriptions (const char *dir, int from_tty)
 	= file_read_description_xml (tdesc_xml.data ());
 
       if (tdesc == NULL || *tdesc != *e.second)
-	failed++;
+	{
+	  printf_filtered ( _("Descriptions for %s do not match\n"), e.first);
+	  failed++;
+	  continue;
+	}
+
+      /* Convert both descriptions to xml, and then back again.  Confirm all
+	 descriptions are identical.  */
+
+      const char *xml = tdesc_get_features_xml ((target_desc *) tdesc);
+      const char *xml2 = tdesc_get_features_xml ((target_desc *) e.second);
+      gdb_assert (*xml == '@');
+      gdb_assert (*xml2 == '@');
+      const target_desc *t_trans = target_read_description_xml_string (xml+1);
+      const target_desc *t_trans2 = target_read_description_xml_string (xml2+1);
+
+      if (t_trans == NULL || t_trans2 == NULL)
+	{
+	  printf_filtered (
+	    _("Could not convert descriptions for %s back to xml (%p %p)\n"),
+	    e.first, t_trans, t_trans2);
+	  failed++;
+	}
+      else if (*tdesc != *t_trans || *tdesc != *t_trans2)
+	{
+	  printf_filtered
+	    (_("Translated descriptions for %s do not match (%d %d)\n"),
+	    e.first, *tdesc == *t_trans, *tdesc == *t_trans2);
+	  failed++;
+	}
     }
   printf_filtered (_("Tested %lu XML files, %d failed\n"),
 		   (long) selftests::xml_tdesc.size (), failed);

gdb/xml-tdesc.c

@@ -752,3 +752,12 @@ target_fetch_description_xml (struct target_ops *ops)
   return output;
 #endif
 }
+
+/* Take an xml string, parse it, and return the parsed description.  Does not
+   handle a string containing includes.  */
+
+const struct target_desc *
+target_read_description_xml_string (const char *xml_str)
+{
+  return tdesc_parse_xml (xml_str, nullptr, nullptr);
+}

gdb/xml-tdesc.h

@@ -44,5 +44,10 @@ const struct target_desc *target_read_description_xml (struct target_ops *);
    otherwise.  */
 gdb::optional<std::string> target_fetch_description_xml (target_ops *ops);
 
+/* Take an xml string, parse it, and return the parsed description.  Does not
+   handle a string containing includes.  */
+
+const struct target_desc *target_read_description_xml_string (const char *);
+
 #endif /* XML_TDESC_H */