TheRock/debug-tools/rocgdb/source/gdb/dwarf2/expr.c

/* DWARF 2 Expression Evaluator.

   Copyright (C) 2001-2024 Free Software Foundation, Inc.
   Copyright (C) 2020-2024 Advanced Micro Devices, Inc. All rights reserved.

   Contributed by Daniel Berlin (dan@dberlin.org)

   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/>.  */

#include "block.h"
#include "event-top.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "value.h"
#include "gdbcore.h"
#include "dwarf2.h"
#include "dwarf2/expr.h"
#include "dwarf2/loc.h"
#include "dwarf2/read.h"
#include "frame.h"
#include "gdbsupport/underlying.h"
#include "gdbsupport/refcounted-object.h"
#include "gdbarch.h"
#include "gdbthread.h"
#include "inferior.h"
#include "objfiles.h"
#include "observable.h"

using context_generation_t = ULONGEST;

/* A monotically increasing counter modified every time any inferior memory
   is touched or any register in any target is modified.  This can be used to
   know if state (register value) cached by the evaluator might be stale.  */

static context_generation_t context_generation = 0;

/* This holds gdbarch-specific types used by the DWARF expression
   evaluator.  See comments in execute_stack_op.  */

struct dwarf_gdbarch_types
{
  struct type *dw_types[3] {};
};

/* Cookie for gdbarch data.  */

static const registry<gdbarch>::key<dwarf_gdbarch_types> dwarf_arch_cookie;

/* Ensure that a thread is in focus and throw an exception
   otherwise.  */
static void
ensure_have_thread (const char *op_name)
{
  if (inferior_ptid == null_ptid)
    throw_error (DWARF2_THREAD_CONTEXT_MISSING,
		 _("%s evaluation requires a thread to be in focus."),
		 op_name);
}

/* See expr.h.  */

void
ensure_have_frame (const frame_info_ptr &frame, const char *context)
{
  if (frame == nullptr)
    throw_error (DWARF2_FRAME_CONTEXT_MISSING,
		 _("%s evaluation requires a frame."), context);

  ensure_have_thread (context);
}

/* Ensure that a PER_CU is defined and throw an exception otherwise.  */

static void
ensure_have_per_cu (dwarf2_per_cu_data *per_cu, const char* op_name)
{
  if (per_cu == nullptr)
    throw_error (GENERIC_ERROR,
		 _("%s evaluation requires a compilation unit."), op_name);
}

/* Ensure that a SIMD lane is in focus and throw an exception
   otherwise.  */
static void
ensure_have_simd_lane (const char *op_name)
{
  ensure_have_thread (op_name);

  int current_simd_lane
    = inferior_thread ()->current_simd_lane ();

  if (current_simd_lane == -1)
    error (_("%s evaluation requires a SIMD lane to be in focus."), op_name);
}

/* Return the number of bytes overlapping a contiguous chunk of N_BITS
   bits whose first bit is located at bit offset START.  */

static size_t
bits_to_bytes (ULONGEST start, ULONGEST n_bits)
{
  return (start % HOST_CHAR_BIT + n_bits + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
}

/* Throw an exception about the invalid DWARF expression.  */

static void
ill_formed_expression ()
{
  error (_("Ill-formed DWARF expression"));
}

/* Read register REGNUM's contents in a given FRAME context.

   The data read is offsetted by OFFSET, and the number of bytes read
   is defined by LENGTH.  The data is then copied into the
   caller-managed buffer BUF.

   If the register is optimized out or unavailable for the given
   FRAME, the OPTIMIZED and UNAVAILABLE outputs are set
   accordingly  */

static void
read_from_register (const frame_info_ptr &frame, int regnum,
		    CORE_ADDR offset, gdb::array_view<gdb_byte> buf,
		    int *optimized, int *unavailable)
{
  gdbarch *arch = get_frame_arch (frame);
  int regsize = register_size (arch, regnum);
  int numregs = gdbarch_num_cooked_regs (arch);
  int length = buf.size ();

  /* If a register is wholly inside the OFFSET, skip it.  */
  if (frame == NULL || !regsize
      || offset + length > regsize || numregs < regnum)
    {
      *optimized = 0;
      *unavailable = 1;
      return;
    }

  gdb::byte_vector temp_buf (regsize);
  enum lval_type lval;
  CORE_ADDR address;
  int realnum;

  frame_register_unwind (get_next_frame_sentinel_okay (frame), regnum,
			 optimized, unavailable, &lval, &address, &realnum,
			 temp_buf.data ());

  if (!*optimized && !*unavailable)
     memcpy (buf.data (), (char *) temp_buf.data () + offset, length);

  return;
}

/* Write register REGNUM's contents in a given FRAME context.

   The data written is offsetted by OFFSET, and the number of bytes
   written is defined by LENGTH.  The data is copied from
   caller-managed buffer BUF.

   If the register is optimized out or unavailable for the given
   FRAME, the OPTIMIZED and UNAVAILABLE outputs are set
   accordingly. */

static void
write_to_register (const frame_info_ptr &frame, int regnum,
		   CORE_ADDR offset, gdb::array_view<gdb_byte> buf,
		   int *optimized, int *unavailable)
{
  gdbarch *arch = get_frame_arch (frame);
  int regsize = register_size (arch, regnum);
  int numregs = gdbarch_num_cooked_regs (arch);
  int length = buf.size ();

  /* If a register is wholly inside of OFFSET, skip it.  */
  if (frame == NULL || !regsize
     || offset + length > regsize || numregs < regnum)
    {
      *optimized = 0;
      *unavailable = 1;
      return;
    }

  gdb::byte_vector temp_buf (regsize);
  enum lval_type lval;
  CORE_ADDR address;
  int realnum;

  frame_register_unwind (get_next_frame_sentinel_okay (frame), regnum,
			 optimized, unavailable, &lval, &address, &realnum,
			 temp_buf.data ());

  if (!*optimized && !*unavailable)
    {
      memcpy ((char *) temp_buf.data () + offset, buf.data (), length);

      put_frame_register (frame, regnum, temp_buf);
    }

  return;
}

/* Helper for read_from_memory and write_to_memory.  */

static void
xfer_memory (CORE_ADDR address, gdb_byte *readbuf,
	     const gdb_byte *writebuf,
	     size_t length, bool stack, int *unavailable)
{
  *unavailable = 0;

  target_object object
    = stack ? TARGET_OBJECT_STACK_MEMORY : TARGET_OBJECT_MEMORY;

  ULONGEST xfered_total = 0;

  while (xfered_total < length)
    {
      ULONGEST xfered_partial;

      enum target_xfer_status status
	= target_xfer_partial (current_inferior ()->top_target (),
			       object, NULL,
			       (readbuf != nullptr
				? readbuf + xfered_total
				: nullptr),
			       (writebuf != nullptr
				? writebuf + xfered_total
				: nullptr),
			       address + xfered_total, length - xfered_total,
			       &xfered_partial);

      if (status == TARGET_XFER_OK)
	{
	  xfered_total += xfered_partial;
	  QUIT;
	}
      else if (status == TARGET_XFER_UNAVAILABLE)
	{
	  *unavailable = 1;
	  return;
	}
      else if (status == TARGET_XFER_EOF)
	memory_error (TARGET_XFER_E_IO, address + xfered_total);
      else
	memory_error (status, address + xfered_total);
    }
}

/* Read LENGTH bytes of memory contents starting at ADDRESS.

   The data read is copied to a caller-managed buffer BUF.  STACK
   indicates whether the memory range specified belongs to a stack
   memory region.

   If the memory is unavailable, the UNAVAILABLE output is set.  */

static void
read_from_memory (CORE_ADDR address, gdb_byte *buffer,
		  size_t length, bool stack, int *unavailable)
{
  xfer_memory (address, buffer, nullptr, length, stack, unavailable);
}

/* Write LENGTH bytes of memory contents starting at ADDRESS.

   The data written is copied from a caller-managed buffer buf.  STACK
   indicates whether the memory range specified belongs to a stack
   memory region.

   If the memory is unavailable, the UNAVAILABLE output is set.  */

static void
write_to_memory (CORE_ADDR address, const gdb_byte *buffer,
		 size_t length, bool stack, int *unavailable)
{
  xfer_memory (address, nullptr, buffer, length, stack, unavailable);

  gdb::observers::memory_changed.notify (address, length, buffer);
}


type *
address_type (gdbarch *arch, int addr_size)
{
  dwarf_gdbarch_types *types = dwarf_arch_cookie.get (arch);
  if (types == nullptr)
    types = dwarf_arch_cookie.emplace (arch);
  int ndx;

  if (addr_size == 2)
    ndx = 0;
  else if (addr_size == 4)
    ndx = 1;
  else if (addr_size == 8)
    ndx = 2;
  else
    error (_("Unsupported address size in DWARF expressions: %d bits"),
	   HOST_CHAR_BIT * addr_size);

  if (types->dw_types[ndx] == NULL)
    {
      type_allocator alloc (arch);
      types->dw_types[ndx]
	= init_integer_type (alloc, HOST_CHAR_BIT * addr_size,
			     0, "<signed DWARF address type>");
    }

  return types->dw_types[ndx];
}

class dwarf_location;
class dwarf_memory;
class dwarf_value;

/* Closure callback functions.  */

static void *
copy_value_closure (const value *v);

static void
free_value_closure (value *v);

static void
rw_closure_value (value *v, value *from);

static bool
check_synthetic_pointer (const value *value, LONGEST bit_offset,
			 int bit_length);

static void
write_closure_value (value *to, value *from);

static void
read_closure_value (value *v);

static bool
is_optimized_out_closure_value (value *v);

static value *
indirect_closure_value (value *value);

static value *
coerce_closure_ref (const value *value);

static bool
closure_mem_addr_ranges (const value *value, std::vector<addr_range> &ranges);

/* Functions for accessing a variable described by DW_OP_piece,
   DW_OP_bit_piece or DW_OP_implicit_pointer.  */

static const lval_funcs closure_value_funcs = {
  read_closure_value,
  write_closure_value,
  is_optimized_out_closure_value,
  indirect_closure_value,
  coerce_closure_ref,
  check_synthetic_pointer,
  closure_mem_addr_ranges,
  copy_value_closure,
  free_value_closure
};

/* Closure class that encapsulates a DWARF location description and a
   frame information used when that location description was created.

   Used for lval_computed value abstraction.  */

class computed_closure : public refcounted_object
{
public:
  explicit computed_closure (std::shared_ptr<dwarf_location> location,
			     struct frame_id frame_id)
    : m_location (location), m_frame_id (frame_id)
  {}

  explicit computed_closure (std::shared_ptr<dwarf_location> location,
			     const frame_info_ptr &frame)
    : m_location (location), m_frame (frame)
  {}

  const std::shared_ptr<dwarf_location> get_location () const
  {
    return m_location;
  }

  frame_id get_frame_id () const
  {
    return m_frame_id;
  }

  frame_info_ptr get_frame () const
  {
    return m_frame;
  }

private:
  /* Entry that this class encloses.  */
  std::shared_ptr<dwarf_location> m_location;

  /* Frame ID context of the closure.  */
  frame_id m_frame_id;

  /* In the case of frame expression evaluator the frame_id
     is not safe to use because the frame itself is being built.
     Only in these cases we set and use frame info directly.  */
  frame_info_ptr m_frame = NULL;
};

/* Base class that describes entries found on a DWARF expression
   evaluation stack.  */

class dwarf_entry : public std::enable_shared_from_this<dwarf_entry>
{
public:
  /* Not expected to be called on it's own.  */
  dwarf_entry () = default;

  virtual ~dwarf_entry () = 0;

  /* Clones entry.  */
  virtual std::shared_ptr<dwarf_entry> clone () const = 0;

  /* Convert DWARF entry into a DWARF location description.  ARCH
     defines an architecture of the location described.   */
  virtual std::shared_ptr<dwarf_location> to_location (gdbarch *arch) = 0;

  /* Convert DWARF entry into a DWARF value.  TYPE defines a
     desired type of the returned DWARF value if it already
     doesn't have one.  */
  virtual std::shared_ptr<dwarf_value> to_value (struct type *type) = 0;

  /* Convert DWARF entry to the matching struct value representation
     of the given TYPE type in a given FRAME. SUBOBJ_TYPE information
     if specified, will be used for more precise description of the
     source variable type information.  Where SUBOBJ_OFFSET defines an
     offset into the DWARF entry contents.  */
  virtual value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
			       struct type *subobj_type,
			       LONGEST subobj_offset) = 0;
};

dwarf_entry::~dwarf_entry () = default;

/* Location description entry found on a DWARF expression evaluation
   stack.

   Types of locations described can be: register location, memory
   location, implicit location, implicit pointer location, undefined
   location and composite location (composed out of any of the location
   types including another composite location).  */

class dwarf_location : public dwarf_entry
{
public:
  /* Not expected to be called on it's own.  */
  dwarf_location (gdbarch *arch, LONGEST offset = 0,
		  LONGEST bit_suboffset = 0)
    : m_arch (arch), m_initialised (true)
  {
    m_offset = offset;
    m_offset += bit_suboffset / HOST_CHAR_BIT;
    m_bit_suboffset = bit_suboffset % HOST_CHAR_BIT;
  }

  dwarf_location (const dwarf_location &location)
    : m_arch (location.m_arch),
      m_offset (location.m_offset),
      m_bit_suboffset (location.m_bit_suboffset),
      m_initialised (location.m_initialised)
  {}

  virtual ~dwarf_location () = default;

  /* Add bit offset to the location description.  */
  void add_bit_offset (LONGEST bit_offset)
  {
    LONGEST bit_total_offset = m_bit_suboffset + bit_offset;

    m_offset += bit_total_offset / HOST_CHAR_BIT;
    m_bit_suboffset = bit_total_offset % HOST_CHAR_BIT;
  };

  void set_initialised (bool initialised)
  {
    m_initialised = initialised;
  };

  /* Convert DWARF entry into a DWARF location description.  If the
     entry is already a location description, it will be returned as a
     result and no conversion will be applied to it.  ARCH defines an
     architecture of the location described.  */
  std::shared_ptr<dwarf_location> to_location (gdbarch *arch) override
  {
    return std::dynamic_pointer_cast<dwarf_location> (shared_from_this ());
  }

  /* Convert DWARF entry into a DWARF value.  If the conversion
     from that location description kind to a value is not supported
     the result is an empty pointer.  TYPE defines a desired type of
     the returned DWARF value if it already doesn't have one.  */
  virtual std::shared_ptr<dwarf_value> to_value (struct type *type) override
  {
    ill_formed_expression ();
    return std::shared_ptr<dwarf_value> (nullptr);
  }

  /* Make a slice of a location description with an added bit offset
     BIT_OFFSET and BIT_SIZE size in bits.

     In the case of a composite location description, function returns
     a minimum subset of that location description that starts on a
     given offset of a given size.  */
  virtual std::shared_ptr<dwarf_location> slice (LONGEST bit_offset,
						 LONGEST bit_size) const;

  /* Read contents from the descripbed location.

     The read operation is performed in the context of a FRAME.
     BIT_SIZE is the number of bits to read.  The data read is copied
     to the caller-managed buffer BUF.  BIG_ENDIAN defines the
     endianness of the target.  BITS_TO_SKIP is a bit offset into the
     location and BUF_BIT_OFFSET is buffer BUF's bit offset.
     LOCATION_BIT_LIMIT is a maximum number of bits that location can
     hold, where value zero signifies that there is no such
     restriction.

     Note that some location types can be read without a FRAME context.

     If the location is optimized out or unavailable (entirely or
     partially), the affected ranges will be appended to OPTIMIZED and
     UNAVAILABLE as necessary.  OPTIMIZED or UNAVAILABLE are left unchanged
     if the location is not optimized or unavailable.  The ranges will
     reference regions relative to BITS_TO_SKIP.  */
  virtual void read (const frame_info_ptr &frame, gdb_byte *buf,
		     int buf_bit_offset, size_t bit_size,
		     LONGEST bits_to_skip, size_t location_bit_limit,
		     bool big_endian, std::vector<range> &optimized_ranges,
		     std::vector<range> &unavailable) const = 0;

  /* Write contents to a described location.

     The write operation is performed in the context of a FRAME.
     BIT_SIZE is the number of bits written.  The data written is
     copied from the caller-managed BUF buffer.  BIG_ENDIAN defines an
     endianness of the target.  BITS_TO_SKIP is a bit offset into the
     location and BUF_BIT_OFFSET is buffer BUF's bit offset.
     LOCATION_BIT_LIMIT is a maximum number of bits that location can
     hold, where value zero signifies that there is no such
     restriction.

     Note that some location types can be written without a FRAME
     context.

     If the location is optimized out or unavailable, the OPTIMIZED and
     UNAVAILABLE outputs are set.  */
  virtual void write (const frame_info_ptr &frame, const gdb_byte *buf,
		      int buf_bit_offset, size_t bit_size,
		      LONGEST bits_to_skip, size_t location_bit_limit,
		      bool big_endian, int *optimized,
		      int *unavailable) const = 0;

  /* Apply dereference operation on the DWARF location description.
     Operation returns a DWARF value of a given TYPE type while FRAME
     contains a frame context information of the location.  ADDR_INFO
     (if present) describes a passed in memory buffer if a regular
     memory read is not desired for certain address range.  If the SIZE
     is specified, it must be equal or smaller then the TYPE type size.
     If SIZE is smaller then the type size, the value will be zero
     extended to the difference.  */
  virtual std::shared_ptr<dwarf_value> deref
    (const frame_info_ptr &frame, const property_addr_info *addr_info,
     struct type *type, size_t size = 0) const;

/* Read data from the VALUE contents to the location specified by the
   location description.

   The read operation is performed in the context of a FRAME.  BIT_SIZE
   is the number of bits to read.  VALUE_BIT_OFFSET is a bit offset
   into a VALUE content and BITS_TO_SKIP is a bit offset into the
   location.  LOCATION_BIT_LIMIT is a maximum number of bits that
   location can hold, where value zero signifies that there is no such
   restriction.

   Note that some location types can be read without a FRAME context.  */
  virtual void read_from_gdb_value (const frame_info_ptr &frame,
				    struct value *value, int value_bit_offset,
				    LONGEST bits_to_skip, size_t bit_size,
				    size_t location_bit_limit);

/* Write data to the VALUE contents from the location specified by the
   location description.

   The write operation is performed in the context of a FRAME.
   BIT_SIZE is the number of bits to read.  VALUE_BIT_OFFSET is a bit
   offset into a VALUE content and BITS_TO_SKIP is a bit offset into
   the location.  LOCATION_BIT_LIMIT is a maximum number of bits that
   location can hold, where value zero signifies that there is no such
   restriction.

   Note that some location types can be read without a FRAME context.  */
  virtual void write_to_gdb_value (const frame_info_ptr &frame,
				   struct value *value, int value_bit_offset,
				   LONGEST bits_to_skip, size_t bit_size,
				   size_t location_bit_limit);

  /* Check if a given DWARF location description contains an implicit
     pointer location description of a BIT_LENGTH size on a given
     BIT_OFFSET offset.  */
  virtual bool is_implicit_ptr_at (LONGEST bit_offset, int bit_length) const
  {
     return false;
  }

  /* Recursive indirecting of the implicit pointer location description
     if that location is or encapsulates an implicit pointer.  The
     operation is performed in a given FRAME context, using the TYPE as
     the type of the pointer.  Where POINTER_OFFSET is an offset
     applied to that implicit pointer location description before the
     operation. BIT_OFFSET is a bit offset applied to the location and
     BIT_LENGTH is a bit length of the read.

     Indirecting is only performed on the implicit pointer location
     description parts of the location.  */
  virtual value *indirect_implicit_ptr (const frame_info_ptr &frame,
					struct type *type,
					LONGEST pointer_offset = 0,
					LONGEST bit_offset = 0,
					int bit_length = 0) const
  {
    return nullptr;
  }

/* Check if location description resolves into optimized out.

   The check operation is performed in the context of a FRAME.
   BIG_ENDIAN defines the endianness of the target, BIT_SIZE is the
   number of bits to read and BITS_TO_SKIP is a bit offset into the
   location.  LOCATION_BIT_LIMIT is a maximum number of bits that
   location can hold, where value zero signifies that there is
   no such restriction.  */
  virtual bool is_optimized_out (const frame_info_ptr &frame, bool big_endian,
				 LONGEST bits_to_skip, size_t bit_size,
				 size_t location_bit_limit) const
  {
    return false;
  }

  /* Collect memory address ranges represented by the location
     description, of the given byte SIZE and starting at the BIT_OFFSET
     bit offset.

     Return false if any piece of the location description does not
     describe a memory location.  */
  virtual bool mem_addr_ranges (LONGEST bit_offset, size_t size,
				std::vector<addr_range> &ranges) const
  {
    return false;
  }

protected:
  /* Architecture of the location.  */
  gdbarch *m_arch;

  /* Byte offset into the location.  */
  LONGEST m_offset;

  /* Bit suboffset of the last byte.  */
  LONGEST m_bit_suboffset;

  /* Whether the location is initialized.  Used for non-standard
     DW_OP_GNU_uninit operation.  */
  bool m_initialised;
};

/* This is a default implementation used on
   non-composite location descriptions.  */

std::shared_ptr<dwarf_location>
dwarf_location::slice (LONGEST bit_offset, LONGEST bit_size) const
{
  auto location_slice = this->clone ()->to_location (m_arch);
  location_slice->add_bit_offset (bit_offset);
  return location_slice;
}

std::shared_ptr<dwarf_value>
dwarf_location::deref (const frame_info_ptr &frame,
		       const property_addr_info *addr_info,
		       struct type *type, size_t size) const
{
  bool big_endian = type_byte_order (type) == BFD_ENDIAN_BIG;
  size_t actual_size = size != 0 ? size : type->length ();

  if (actual_size > type->length ())
    ill_formed_expression ();

    /* If the size of the object read from memory is different
     from the type length, we need to zero-extend it.  */
  gdb::byte_vector read_buf (type->length (), 0);
  gdb_byte *buf_ptr = read_buf.data ();
  std::vector<range> optimized, unavailable;

  if (big_endian)
    buf_ptr += type->length () - actual_size;

  this->read (frame, buf_ptr, 0, actual_size * HOST_CHAR_BIT,
	      0, 0, big_endian, optimized, unavailable);

  if (!optimized.empty ())
    throw_error (OPTIMIZED_OUT_ERROR,
		 _("Can't do read-modify-write to "
		   "update bitfield; containing word "
		   "has been optimized out"));
  if (!unavailable.empty ())
    throw_error (NOT_AVAILABLE_ERROR,
		 _("Can't dereference "
		   "update bitfield; containing word "
		   "is unavailable"));

  return std::make_shared<dwarf_value> (read_buf.data (), type);
}

void
dwarf_location::read_from_gdb_value (const frame_info_ptr &frame,
				     struct value *value,
				     int value_bit_offset,
				     LONGEST bits_to_skip, size_t bit_size,
				     size_t location_bit_limit)
{
  int optimized, unavailable;
  bool big_endian = type_byte_order (value->type ()) == BFD_ENDIAN_BIG;

  this->write (frame, value->contents ().data (), value_bit_offset,
	       bit_size, bits_to_skip, location_bit_limit,
	       big_endian, &optimized, &unavailable);

  if (optimized)
    throw_error (OPTIMIZED_OUT_ERROR,
		 _("Can't do read-modify-write to "
		   "update bitfield; containing word "
		   "has been optimized out"));
  if (unavailable)
    throw_error (NOT_AVAILABLE_ERROR,
		 _("Can't do read-modify-write to "
		   "update bitfield; containing word "
		   "is unavailable"));
}

void
dwarf_location::write_to_gdb_value (const frame_info_ptr &frame,
				    struct value *value, int value_bit_offset,
				    LONGEST bits_to_skip, size_t bit_size,
				    size_t location_bit_limit)
{
  std::vector<range> optimized, unavailable;
  bool big_endian = type_byte_order (value->type ()) == BFD_ENDIAN_BIG;

  this->read (frame, value->contents_raw ().data (), value_bit_offset,
	      bit_size, bits_to_skip, location_bit_limit,
	      big_endian, optimized, unavailable);

  for (auto &&optimized_range : optimized)
    value->mark_bits_optimized_out
      (value_bit_offset + optimized_range.offset, optimized_range.length);
  for (auto &&unavailable_range : unavailable)
    value->mark_bits_unavailable
      (value_bit_offset + unavailable_range.offset, unavailable_range.length);
}

/* Value entry found on a DWARF expression evaluation stack.  */

class dwarf_value : public dwarf_entry
{
public:
  dwarf_value (const gdb_byte *contents, struct type *type)
  {
    size_t type_len = type->length ();
    m_contents.reset ((gdb_byte *) xzalloc (type_len));

    memcpy (m_contents.get (), contents, type_len);
    m_type = type;
  }

  dwarf_value (ULONGEST value, struct type *type)
  {
    m_contents.reset ((gdb_byte *) xzalloc (type->length ()));

    pack_unsigned_long (m_contents.get (), type, value);
    m_type = type;
  }

  dwarf_value (LONGEST value, struct type *type)
  {
    m_contents.reset ((gdb_byte *) xzalloc (type->length ()));

    pack_long (m_contents.get (), type, value);
    m_type = type;
  }

  dwarf_value (const dwarf_value &value)
  {
    struct type *type = value.m_type;
    size_t type_len = type->length ();

    m_contents.reset ((gdb_byte *) xzalloc (type_len));

    memcpy (m_contents.get (), value.m_contents.get (), type_len);
    m_type = type;
  }

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_value> (*this);
  }

  const gdb_byte* get_contents () const
  {
    return m_contents.get ();
  }

  type* get_type () const
  {
    return m_type;
  }

  LONGEST to_long () const
  {
    return unpack_long (m_type, m_contents.get ());
  }

  /* Convert DWARF value to the matching struct value representation
     of the given TYPE type.  Where offset defines an offset into the
     DWARF value contents.  */
  value *convert_to_gdb_value (struct type *type, LONGEST offset = 0) const;

  /* Convert DWARF value into a DWARF memory location description.
     ARCH defines an architecture of the location described.  */
  std::shared_ptr<dwarf_location> to_location (gdbarch *arch) override;

  /* Convert DWARF entry into a DWARF value.  If the entry
     is already a value, it is just returned and the TYPE type
     information is ignored.  */
  std::shared_ptr<dwarf_value> to_value (struct type *type) override
  {
    return std::dynamic_pointer_cast<dwarf_value> (shared_from_this ());
  }

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

private:
  /* Value contents as a stream of bytes in target byte order.  */
  gdb::unique_xmalloc_ptr<gdb_byte> m_contents;

  /* Type of the value held by the entry.  */
  type *m_type;
};

value *
dwarf_value::convert_to_gdb_value (struct type *type, LONGEST offset) const
{
  size_t type_len = type->length ();

  if (offset + type_len > m_type->length ())
    invalid_synthetic_pointer ();

  value *retval = value::allocate (type);
  memcpy (retval->contents_raw ().data (),
	  m_contents.get () + offset, type_len);
  return retval;
}

std::shared_ptr<dwarf_location>
dwarf_value::to_location (gdbarch *arch)
{
  LONGEST offset;

  if (gdbarch_integer_to_address_p (arch))
    offset = gdbarch_integer_to_address (arch, m_type, m_contents.get (),
					 ARCH_ADDR_SPACE_ID_DEFAULT);
  else
    offset = extract_unsigned_integer (m_contents.get (), m_type->length (),
				       type_byte_order (m_type));

  auto memory = std::make_shared<dwarf_memory> (arch, offset);
  return std::dynamic_pointer_cast<dwarf_location> (memory);
}

value *
dwarf_value::to_gdb_value (const frame_info_ptr &frame, struct type *type,
			   struct type *subobj_type,
			   LONGEST subobj_offset)
{
  if (subobj_type == nullptr)
    subobj_type = type;

  return convert_to_gdb_value (subobj_type, subobj_offset);
}

/* Undefined location description entry.  This is a special location
   description type that describes the location description that is
   not known.  */

class dwarf_undefined : public dwarf_location
{
public:
  dwarf_undefined (gdbarch *arch, LONGEST offset = 0,
		   LONGEST bit_suboffset = 0)
    : dwarf_location (arch, offset, bit_suboffset)
  {}

  dwarf_undefined (const dwarf_undefined &undefined)
    : dwarf_location (undefined)
  {}

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_undefined> (*this);
  }

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip, size_t location_bit_limit,
	     bool big_endian, std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override
  {
    optimized.push_back ({0, bit_size});
  }

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size,
	      LONGEST bits_to_skip, size_t location_bit_limit,
	      bool big_endian, int *optimized, int *unavailable) const override
  {
    *unavailable = 0;
    *optimized = 1;
  }

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override
  {
    value *retval = value::allocate (subobj_type);

    if (subobj_type == nullptr)
      subobj_type = type;

    retval->mark_bytes_optimized_out (subobj_offset, subobj_type->length ());
    return retval;
  }

  bool is_optimized_out (const frame_info_ptr &frame, bool big_endian,
			 LONGEST bits_to_skip, size_t bit_size,
			 size_t location_bit_limit) const override
  {
    return true;
  }
};

class dwarf_memory : public dwarf_location
{
public:
  dwarf_memory (gdbarch *arch, LONGEST offset,
		LONGEST bit_suboffset = 0, bool stack = false,
		arch_addr_space_id address_space = ARCH_ADDR_SPACE_ID_DEFAULT)
    : dwarf_location (arch, offset, bit_suboffset),
      m_stack (stack), m_address_space (address_space)
  {}

  dwarf_memory (const dwarf_memory &memory)
    : dwarf_location (memory),
      m_stack (memory.m_stack),
      m_address_space (memory.m_address_space)
  {}

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_memory> (*this);
  }

  void set_stack (bool stack)
  {
    m_stack = stack;
  };

  void set_address_space (arch_addr_space_id address_space)
  {
    m_address_space = address_space;
  };

  std::shared_ptr<dwarf_value> to_value (struct type *type) override;

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip,
	     size_t location_bit_limit, bool big_endian,
	     std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override;

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size, LONGEST bits_to_skip,
	      size_t location_bit_limit, bool big_endian,
	      int *optimized, int *unavailable) const override;

  std::shared_ptr<dwarf_value> deref (const frame_info_ptr &frame,
				      const property_addr_info *addr_info,
				      struct type *type,
				      size_t size = 0) const override;

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

  bool mem_addr_ranges (LONGEST bit_offset, size_t size,
			std::vector<addr_range> &ranges) const override
  {
    ranges.emplace_back
	     (gdbarch_segment_address_to_core_address
		(m_arch, m_address_space,
		 m_offset + (m_bit_suboffset + bit_offset) / HOST_CHAR_BIT),
		 size);

    return true;
  }

private:
  /* True if the location belongs to a stack memory region.  */
  bool m_stack;

  /* Address space of the location.  */
  arch_addr_space_id m_address_space;
};

std::shared_ptr<dwarf_value>
dwarf_memory::to_value (struct type *type)
{
  if (m_address_space)
    ill_formed_expression ();

  return std::make_shared<dwarf_value> (m_offset, type);
}

void
dwarf_memory::read (const frame_info_ptr &frame, gdb_byte *buf,
		    int buf_bit_offset, size_t bit_size,
		    LONGEST bits_to_skip, size_t location_bit_limit,
		    bool big_endian, std::vector<range> &optimized,
		    std::vector<range> &unavailable) const
{
  LONGEST total_bits_to_skip = bits_to_skip;
  CORE_ADDR start_address
    = m_offset + (m_bit_suboffset + total_bits_to_skip) / HOST_CHAR_BIT;
  gdb::byte_vector temp_buf;

  start_address
    = gdbarch_segment_address_to_core_address (m_arch, m_address_space,
					       start_address);

  total_bits_to_skip += m_bit_suboffset;

  if (total_bits_to_skip % HOST_CHAR_BIT == 0
      && bit_size % HOST_CHAR_BIT == 0
      && buf_bit_offset % HOST_CHAR_BIT == 0)
    {
      /* Everything is byte-aligned, no buffer needed.  */
      int is_unavailable;
      read_from_memory (start_address,
			buf + buf_bit_offset / HOST_CHAR_BIT,
			bit_size / HOST_CHAR_BIT, m_stack, &is_unavailable);
      if (is_unavailable)
	unavailable.push_back ({0, bit_size});
    }
  else
    {
      LONGEST this_size = bits_to_bytes (total_bits_to_skip, bit_size);
      temp_buf.resize (this_size);

      /* Can only read from memory on byte granularity so an
	 additional buffer is required.  */
      int is_unavailable;
      read_from_memory (start_address, temp_buf.data (), this_size,
			m_stack, &is_unavailable);

      if (!is_unavailable)
	copy_bitwise (buf, buf_bit_offset, temp_buf.data (),
		      total_bits_to_skip % HOST_CHAR_BIT,
		      bit_size, big_endian);
      else
	unavailable.push_back ({0, bit_size});
    }
}

void
dwarf_memory::write (const frame_info_ptr &frame, const gdb_byte *buf,
		     int buf_bit_offset, size_t bit_size,
		     LONGEST bits_to_skip, size_t location_bit_limit,
		     bool big_endian, int *optimized, int *unavailable) const
{
  LONGEST total_bits_to_skip = bits_to_skip;
  CORE_ADDR start_address
    = m_offset + (m_bit_suboffset + total_bits_to_skip) / HOST_CHAR_BIT;
  gdb::byte_vector temp_buf;

  total_bits_to_skip += m_bit_suboffset;
  *optimized = 0;

  start_address
    = gdbarch_segment_address_to_core_address (m_arch, m_address_space,
					       start_address);

  if (total_bits_to_skip % HOST_CHAR_BIT == 0
      && bit_size % HOST_CHAR_BIT == 0
      && buf_bit_offset % HOST_CHAR_BIT == 0)
    {
      /* Everything is byte-aligned; no buffer needed.  */
      write_to_memory (start_address, buf + buf_bit_offset / HOST_CHAR_BIT,
		       bit_size / HOST_CHAR_BIT, m_stack, unavailable);
    }
  else
    {
      LONGEST this_size = bits_to_bytes (total_bits_to_skip, bit_size);
      temp_buf.resize (this_size);

      if (total_bits_to_skip % HOST_CHAR_BIT != 0
	  || bit_size % HOST_CHAR_BIT != 0)
	{
	  if (this_size <= HOST_CHAR_BIT)
	    /* Perform a single read for small sizes.  */
	    read_from_memory (start_address, temp_buf.data (),
			      this_size, m_stack, unavailable);
	  else
	    {
	      /* Only the first and last bytes can possibly have
		 any bits reused.  */
	      read_from_memory (start_address, temp_buf.data (),
				1, m_stack, unavailable);

	      if (!*unavailable)
		read_from_memory (start_address + this_size - 1,
				  &temp_buf[this_size - 1], 1,
				  m_stack, unavailable);
	    }
	}

      copy_bitwise (temp_buf.data (), total_bits_to_skip % HOST_CHAR_BIT,
		    buf, buf_bit_offset, bit_size, big_endian);

      write_to_memory (start_address, temp_buf.data (), this_size,
		       m_stack, unavailable);
    }
}

std::shared_ptr<dwarf_value>
dwarf_memory::deref (const frame_info_ptr &frame,
		     const property_addr_info *addr_info,
		     struct type *type, size_t size) const
{
  bool big_endian = type_byte_order (type) == BFD_ENDIAN_BIG;
  size_t actual_size = size != 0 ? size : type->length ();

  if (actual_size > type->length ())
    ill_formed_expression ();

  gdb::byte_vector read_buf (type->length (), 0);
  size_t size_in_bits = actual_size * HOST_CHAR_BIT;
  gdb_byte *buf_ptr = read_buf.data ();

  if (big_endian)
    buf_ptr += type->length () - actual_size;

  /* Covers the case where we have a passed in memory that is not
     part of the target and requires for the location description
     to address it instead of addressing the actual target
     memory.  */
  LONGEST this_size = bits_to_bytes (m_bit_suboffset, size_in_bits);

  /* We shouldn't have a case where we read from a passed in
     memory and the same memory being marked as stack. */
  if (!m_stack
      && this_size != 0
      && addr_info != nullptr
      && m_offset >= addr_info->addr
      && m_offset + this_size <= (addr_info->addr
				  + addr_info->valaddr.size ()))
    {
      /* Using second buffer here because the copy_bitwise
	 doesn't support in place copy.  */
      gdb::byte_vector temp_buf (this_size);
      CORE_ADDR offset_in_buf = m_offset - addr_info->addr;
      memcpy (temp_buf.data (), addr_info->valaddr.data () + offset_in_buf,
	      this_size);
      copy_bitwise (buf_ptr, 0, temp_buf.data (),
		    m_bit_suboffset, size_in_bits, big_endian);
    }
  else
    {
      std::vector<range> optimized, unavailable;

      this->read (frame, buf_ptr, 0, size_in_bits, 0, 0,
		  big_endian, optimized, unavailable);

      if (!optimized.empty ())
	throw_error (OPTIMIZED_OUT_ERROR,
		     _("Can't do read-modify-write to "
		     "update bitfield; containing word "
		     "has been optimized out"));
      if (!unavailable.empty ())
	throw_error (NOT_AVAILABLE_ERROR,
		     _("Can't dereference "
		     "update bitfield; containing word "
		     "is unavailable"));
    }

  return std::make_shared<dwarf_value> (read_buf.data (), type);
}

value *
dwarf_memory::to_gdb_value (const frame_info_ptr &frame, struct type *type,
			    struct type *subobj_type,
			    LONGEST subobj_offset)
{
  if (subobj_type == nullptr)
    subobj_type = type;

  struct type *ptr_type = builtin_type (m_arch)->builtin_data_ptr;
  CORE_ADDR address = m_offset;

  address
    = gdbarch_segment_address_to_core_address (m_arch, m_address_space,
					       address);

  if (subobj_type->code () == TYPE_CODE_FUNC
      || subobj_type->code () == TYPE_CODE_METHOD)
    ptr_type = builtin_type (m_arch)->builtin_func_ptr;

  address = value_as_address (value_from_pointer (ptr_type, address));
  value *retval = value_at_lazy (subobj_type, address + subobj_offset, frame);
  retval->set_stack (m_stack);
  retval->set_bitpos (m_bit_suboffset);
  return retval;
}

/* Register location description entry.  */

class dwarf_register : public dwarf_location
{
public:
  dwarf_register (gdbarch *arch, unsigned int regnum,
		  bool on_entry = false, LONGEST offset = 0,
		  LONGEST bit_suboffset = 0)
    : dwarf_location (arch, offset, bit_suboffset),
      m_storage {register_storage_ptr::new_reference
		   (new register_storage (regnum, on_entry))}
  {}

  dwarf_register (const dwarf_register &reg)
    : dwarf_location (reg), m_storage (reg.m_storage)
  {}

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_register> (*this);
  }

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip, size_t location_bit_limit,
	     bool big_endian, std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override;

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size, LONGEST bits_to_skip,
	      size_t location_bit_limit, bool big_endian,
	      int *optimized, int *unavailable) const override;

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

  bool is_optimized_out (const frame_info_ptr &frame, bool big_endian,
			 LONGEST bits_to_skip, size_t bit_size,
			 size_t location_bit_limit) const override;

private:
  struct register_storage : public refcounted_object
  {
    register_storage (unsigned int regnum, bool on_entry)
      : m_regnum { regnum }, m_on_entry { on_entry }
      , m_read_cache {}
    {}

    /* DWARF register number.  */
    unsigned int m_regnum;

    /* True if location is on the frame entry, described
       in CFI of the previous frame.  */
    bool m_on_entry;

    struct read_cache
    {
      read_cache (gdbarch *arch, const frame_info_ptr &frame, int regnum)
	: m_frame { frame }, m_context_generation { context_generation }
	, m_data (register_size (arch, regnum))
	{
	  enum lval_type lval;
	  CORE_ADDR address;
	  int realnum;
	  int optimized, unavailable;
	  frame_register_unwind (get_next_frame_sentinel_okay (frame), regnum,
				 &optimized, &unavailable, &lval,
				 &address, &realnum, m_data.data ());
	  m_optimized_out = optimized;
	  m_unavailable = unavailable;
	}

      bool outdated (const frame_info_ptr &frame) const
      {
	return (m_context_generation != context_generation
		|| frame != m_frame);
      }

      bool optimized_out () const { return m_optimized_out; }
      bool unavailable () const { return m_unavailable; }
      gdb::array_view<const gdb_byte> data () const
      {
	return {m_data};
      }

    private:
      frame_info_ptr m_frame;
      context_generation_t m_context_generation;
      bool m_optimized_out;
      bool m_unavailable;
      gdb::byte_vector m_data;
    };
    std::optional<read_cache> m_read_cache;
  };

  using register_storage_ptr
    = gdb::ref_ptr<register_storage,
		   refcounted_object_delete_ref_policy<register_storage>>;

  register_storage_ptr m_storage;
};

void
dwarf_register::read (const frame_info_ptr &initial_frame, gdb_byte *buf,
		      int buf_bit_offset, size_t bit_size,
		      LONGEST bits_to_skip, size_t location_bit_limit,
		      bool big_endian, std::vector<range> &optimized,
		      std::vector<range> &unavailable) const
{
  frame_info_ptr frame = initial_frame;
  LONGEST total_bits_to_skip = bits_to_skip;
  size_t read_bit_limit = location_bit_limit;
  gdbarch *arch = get_frame_arch (frame);
  int reg = dwarf_reg_to_regnum_or_error (arch, m_storage->m_regnum);
  ULONGEST reg_bits = HOST_CHAR_BIT * register_size (arch, reg);
  gdb::byte_vector temp_buf;

  if (big_endian)
    {
      if (!read_bit_limit || reg_bits <= read_bit_limit)
	read_bit_limit = bit_size;

      total_bits_to_skip += reg_bits - (m_offset * HOST_CHAR_BIT
					+ m_bit_suboffset + read_bit_limit);
    }
  else
    total_bits_to_skip += m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  LONGEST this_size = bits_to_bytes (total_bits_to_skip, bit_size);
  temp_buf.resize (this_size);

  if (m_storage->m_on_entry)
    frame = get_prev_frame_always (frame);

  if (frame == NULL)
    internal_error (_("invalid frame information"));

  /* Populate or refresh the cache if needed.  */
  if (m_storage->m_read_cache.has_value ()
      && m_storage->m_read_cache->outdated (frame))
    m_storage->m_read_cache.reset ();

  if (!m_storage->m_read_cache.has_value ())
    m_storage->m_read_cache.emplace (arch, frame, reg);

  if (m_storage->m_read_cache->optimized_out ())
    optimized.push_back ({0, bit_size});

  if (m_storage->m_read_cache->unavailable ())
    unavailable.push_back ({0, bit_size});

  if (!m_storage->m_read_cache->optimized_out ()
      && !m_storage->m_read_cache->unavailable ())
    {
      if (total_bits_to_skip > reg_bits)
	{
	  /* The read is completely past the register, mark everything as
	     optimized out.  */
	  optimized.push_back ({0, bit_size});
	}
      else
	{
	  if (total_bits_to_skip + bit_size > reg_bits)
	    {
	      /* The access goes past the end of the register.  Mark this part
		 as optimized out, and read the rest.  */
	      optimized.push_back
		({static_cast<LONGEST> (reg_bits) - total_bits_to_skip,
		  (static_cast<LONGEST> (bit_size) + total_bits_to_skip
		   - reg_bits)});
	      bit_size = reg_bits - total_bits_to_skip;
	    }

	  copy_bitwise (buf, buf_bit_offset,
			m_storage->m_read_cache->data ().data (),
			total_bits_to_skip, bit_size, big_endian);
	}
    }

}

void
dwarf_register::write (const frame_info_ptr &initial_frame, const gdb_byte *buf,
		       int buf_bit_offset, size_t bit_size,
		       LONGEST bits_to_skip, size_t location_bit_limit,
		       bool big_endian, int *optimized, int *unavailable) const
{
  /* Invalidate the cache.  */
  m_storage->m_read_cache.reset ();

  frame_info_ptr frame = initial_frame;
  LONGEST total_bits_to_skip = bits_to_skip;
  size_t write_bit_limit = location_bit_limit;
  gdbarch *arch = get_frame_arch (frame);
  int gdb_regnum = dwarf_reg_to_regnum_or_error (arch, m_storage->m_regnum);
  ULONGEST reg_bits = HOST_CHAR_BIT * register_size (arch, gdb_regnum);
  gdb::byte_vector temp_buf;

  if (m_storage->m_on_entry)
    frame = get_prev_frame_always (frame);

  if (frame == NULL)
    internal_error (_("invalid frame information"));

  if (big_endian)
    {
      if (!write_bit_limit || reg_bits <= write_bit_limit)
	write_bit_limit = bit_size;

      total_bits_to_skip += reg_bits - (m_offset * HOST_CHAR_BIT
					+ m_bit_suboffset + write_bit_limit);
    }
  else
    total_bits_to_skip += m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  LONGEST this_size = bits_to_bytes (total_bits_to_skip, bit_size);
  temp_buf.resize (this_size);

  if (total_bits_to_skip % HOST_CHAR_BIT != 0
      || bit_size % HOST_CHAR_BIT != 0)
    {
      /* Contents is copied non-byte-aligned into the register.
         Need some bits from original register value.  */
      read_from_register (frame, gdb_regnum,
			  total_bits_to_skip / HOST_CHAR_BIT,
			  temp_buf, optimized, unavailable);
    }

  copy_bitwise (temp_buf.data (), total_bits_to_skip % HOST_CHAR_BIT, buf,
		buf_bit_offset, bit_size, big_endian);

  write_to_register (frame, gdb_regnum, total_bits_to_skip / HOST_CHAR_BIT,
		     temp_buf, optimized, unavailable);
}

value *
dwarf_register::to_gdb_value (const frame_info_ptr &initial_frame,
			      struct type *type, struct type *subobj_type,
			      LONGEST subobj_offset)
{
  frame_info_ptr frame = initial_frame;
  gdbarch *arch = get_frame_arch (frame);
  int gdb_regnum = dwarf_reg_to_regnum_or_error (arch, m_storage->m_regnum);

  if (subobj_type == nullptr)
    subobj_type = type;

  if (m_storage->m_on_entry)
    frame = get_prev_frame_always (frame);

  if (frame == NULL)
    internal_error (_("invalid frame information"));

  /* Construct the value.  */
  value *retval
    = value_from_register (type, gdb_regnum, frame, m_offset, m_bit_suboffset);

  if (retval->optimized_out ())
    {
      /* This means the register has undefined value / was not saved.
	 As we're computing the location of some variable etc. in the
	 program, not a value for inspecting a register ($pc, $sp, etc.),
	 return a generic optimized out value instead, so that we show
	 <optimized out> instead of <not saved>.  */
      value *temp = value::allocate (subobj_type);
      retval->contents_copy (temp, 0, 0, subobj_type->length ());
      retval = temp;
    }

  return retval;
}

bool
dwarf_register::is_optimized_out (const frame_info_ptr &frame, bool big_endian,
				  LONGEST bits_to_skip, size_t bit_size,
				  size_t location_bit_limit) const
{
  std::vector<range> optimized, unavailable;
  gdb::byte_vector temp_buf (bit_size);

  this->read (frame, temp_buf.data (), 0, bit_size,
	      bits_to_skip, location_bit_limit,
	      big_endian, optimized, unavailable);

  return !optimized.empty ();
}

/* Implicit location description entry.  Describes a location
   description not found on the target but instead saved in a
   gdb-allocated buffer.  */

class dwarf_implicit : public dwarf_location
{
public:

  dwarf_implicit (gdbarch *arch, const gdb_byte *contents,
		  size_t size, enum bfd_endian byte_order)
    : dwarf_location (arch)
  {
    m_contents.reset ((gdb_byte *) xzalloc (size));

    memcpy (m_contents.get (), contents, size);
    m_size = size;
    m_byte_order = byte_order;
  }

  dwarf_implicit (const dwarf_implicit &implicit)
    : dwarf_location (implicit)
  {
    size_t size = implicit.m_size;
    m_contents.reset ((gdb_byte *) xzalloc (size));

    memcpy (m_contents.get (), implicit.m_contents.get (), size);
    m_size = size;
    m_byte_order = implicit.m_byte_order;
  }

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_implicit> (*this);
  }

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip, size_t location_bit_limit,
	     bool big_endian, std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override;

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size,
	      LONGEST bits_to_skip, size_t location_bit_limit,
	      bool big_endian, int* optimized, int* unavailable) const override
  {
    *optimized = 1;
    *unavailable = 0;
  }

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

private:
  /* Implicit location contents as a stream of bytes in target byte-order.  */
  gdb::unique_xmalloc_ptr<gdb_byte> m_contents;

  /* Contents byte stream size.  */
  size_t m_size;

  /* Contents original byte order.  */
  bfd_endian m_byte_order;
};

void
dwarf_implicit::read (const frame_info_ptr &frame, gdb_byte *buf,
		      int buf_bit_offset, size_t bit_size,
		      LONGEST bits_to_skip, size_t location_bit_limit,
		      bool big_endian, std::vector<range> &optimized,
		      std::vector<range> &unavailable) const
{
  ULONGEST implicit_bit_size = HOST_CHAR_BIT * m_size;
  LONGEST total_bits_to_skip = bits_to_skip;
  size_t read_bit_limit = location_bit_limit;

  /* Cut off at the end of the implicit value.  */
  if (m_byte_order == BFD_ENDIAN_BIG)
    {
      if (!read_bit_limit || read_bit_limit > implicit_bit_size)
	read_bit_limit = bit_size;

      total_bits_to_skip
	+= implicit_bit_size - (m_offset * HOST_CHAR_BIT
			       + m_bit_suboffset + read_bit_limit);
    }
  else
    total_bits_to_skip += m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  if (total_bits_to_skip >= implicit_bit_size)
    {
      optimized.push_back ({0, bit_size});
      return;
    }

  if (bit_size > implicit_bit_size - total_bits_to_skip)
    {
      optimized.push_back
	({static_cast<LONGEST> (implicit_bit_size - total_bits_to_skip),
	  bit_size + total_bits_to_skip - implicit_bit_size});
      bit_size = implicit_bit_size - total_bits_to_skip;
    }

  copy_bitwise (buf, buf_bit_offset, m_contents.get (),
		total_bits_to_skip, bit_size, big_endian);
}

value *
dwarf_implicit::to_gdb_value (const frame_info_ptr &frame, struct type *type,
			      struct type *subobj_type,
			      LONGEST subobj_offset)
{
  if (subobj_type == nullptr)
    subobj_type = type;

  size_t subtype_len = subobj_type->length ();
  size_t type_len = type->length ();

  /* To be compatible with expected error output of the existing
     tests, the invalid synthetic pointer is not reported for
     DW_OP_implicit_value operation.  */
  if (subobj_offset + subtype_len > type_len
      && m_byte_order != BFD_ENDIAN_UNKNOWN)
    invalid_synthetic_pointer ();

  value *retval = value::allocate (subobj_type);

  /* The given offset is relative to the actual object.  */
  if (m_byte_order == BFD_ENDIAN_BIG)
    subobj_offset += m_size - type_len;

  memcpy (retval->contents_raw ().data (),
	  (void *) (m_contents.get () + subobj_offset), subtype_len);

  return retval;
}

/* Implicit pointer location description entry.  */

class dwarf_implicit_pointer : public dwarf_location
{
public:
  dwarf_implicit_pointer (gdbarch *arch,
			  dwarf2_per_objfile *per_objfile,
			  dwarf2_per_cu_data *per_cu,
			  int addr_size, sect_offset die_offset,
			  LONGEST offset, LONGEST bit_suboffset = 0)
    : dwarf_location (arch, offset, bit_suboffset),
      m_per_objfile (per_objfile), m_per_cu (per_cu),
      m_addr_size (addr_size), m_die_offset (die_offset)
  {}

  dwarf_implicit_pointer (const dwarf_implicit_pointer &implicit_ptr)
    : dwarf_location (implicit_ptr),
      m_per_objfile (implicit_ptr.m_per_objfile),
      m_per_cu (implicit_ptr.m_per_cu),
      m_addr_size (implicit_ptr.m_addr_size),
      m_die_offset (implicit_ptr.m_die_offset)
  {}

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_implicit_pointer> (*this);
  }

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip, size_t location_bit_limit,
	     bool big_endian, std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override;

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size, LONGEST bits_to_skip,
	      size_t location_bit_limit, bool big_endian,
	      int* optimized, int* unavailable) const override
  {
    *optimized = 1;
    *unavailable = 0;
  }

  /* Reading from and writing to an implicit pointer is not meaningful,
     so we just skip them here.  */
  void read_from_gdb_value (const frame_info_ptr &frame, struct value *value,
			    int value_bit_offset,
			    LONGEST bits_to_skip, size_t bit_size,
			    size_t location_bit_limit) override
  {
    value->mark_bits_optimized_out (bits_to_skip, bit_size);
  }

  void write_to_gdb_value (const frame_info_ptr &frame, struct value *value,
			   int value_bit_offset,
			   LONGEST bits_to_skip, size_t bit_size,
			   size_t location_bit_limit) override
  {}

  bool is_implicit_ptr_at (LONGEST bit_offset, int bit_length) const override
  {
     return true;
  }

  value *indirect_implicit_ptr (const frame_info_ptr &frame, struct type *type,
				LONGEST pointer_offset = 0,
				LONGEST bit_offset = 0,
				int bit_length = 0) const override;

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

private:
  /* Per object file data of the implicit pointer.  */
  dwarf2_per_objfile *m_per_objfile;

  /* Compilation unit context of the implicit pointer.  */
  dwarf2_per_cu_data *m_per_cu;

  /* Address size for the evaluation.  */
  int m_addr_size;

  /* DWARF die offset pointed by the implicit pointer.  */
  sect_offset m_die_offset;
};

void
dwarf_implicit_pointer::read (const frame_info_ptr &frame, gdb_byte *buf,
			      int buf_bit_offset, size_t bit_size,
			      LONGEST bits_to_skip, size_t location_bit_limit,
			      bool big_endian, std::vector<range> &optimized,
			      std::vector<range> &unavailable) const
{
  frame_info_ptr actual_frame = frame;
  LONGEST total_bits_to_skip = bits_to_skip + m_bit_suboffset;

  if (actual_frame == nullptr)
    actual_frame = get_selected_frame (_("No frame selected."));

  struct type *type
    = address_type (get_frame_arch (actual_frame), m_addr_size);

  struct value *value
    = indirect_synthetic_pointer (m_die_offset, m_offset, m_per_cu,
				  m_per_objfile, actual_frame, type);

  gdb_byte *value_contents
    = value->contents_raw ().data () + total_bits_to_skip / HOST_CHAR_BIT;

  if (total_bits_to_skip % HOST_CHAR_BIT == 0
      && bit_size % HOST_CHAR_BIT == 0
      && buf_bit_offset % HOST_CHAR_BIT == 0)
    {
      memcpy (buf + buf_bit_offset / HOST_CHAR_BIT,
	      value_contents, bit_size / HOST_CHAR_BIT);
    }
  else
    {
      copy_bitwise (buf, buf_bit_offset, value_contents,
		    total_bits_to_skip % HOST_CHAR_BIT,
		    bit_size, big_endian);
    }
}

value *
dwarf_implicit_pointer::indirect_implicit_ptr (const frame_info_ptr &frame,
					       struct type *type,
					       LONGEST pointer_offset,
					       LONGEST bit_offset,
					       int bit_length) const
{
  return indirect_synthetic_pointer (m_die_offset, m_offset + pointer_offset,
				     m_per_cu, m_per_objfile, frame, type);
}

value *
dwarf_implicit_pointer::to_gdb_value (const frame_info_ptr &frame,
				      struct type *type,
				      struct type *subobj_type,
				      LONGEST subobj_offset)
{
  if (subobj_type == nullptr)
    subobj_type = type;

  computed_closure *closure
    = new computed_closure (std::make_shared<dwarf_implicit_pointer> (*this),
			    get_frame_id (frame));
  closure->incref ();

  value *retval
    = value::allocate_computed (subobj_type, &closure_value_funcs, closure);
  retval->set_offset (subobj_offset);

  return retval;
}

/* Composite location description entry.  */

class dwarf_composite : public dwarf_location
{
public:
  dwarf_composite (gdbarch *arch, dwarf2_per_cu_data *per_cu,
		   LONGEST offset = 0, LONGEST bit_suboffset = 0)
    : dwarf_location (arch, offset, bit_suboffset), m_per_cu (per_cu)
  {}

  dwarf_composite (const dwarf_composite &composite)
    : dwarf_location (composite), m_per_cu (composite.m_per_cu)
  {
    /* We do a shallow copy of the pieces because they are not
       expected to be modified after they are already formed.  */
    for (unsigned int i = 0; i < composite.m_pieces.size (); i++)
      m_pieces.emplace_back (composite.m_pieces[i].m_location,
			     composite.m_pieces[i].m_size);

    m_completed = composite.m_completed;
  }

  std::shared_ptr<dwarf_entry> clone () const override
  {
    return std::make_shared<dwarf_composite> (*this);
  }

  std::shared_ptr<dwarf_location> slice (LONGEST bit_offset,
					 LONGEST bit_size) const override;

  void add_piece (std::shared_ptr<dwarf_location> location, ULONGEST bit_size)
  {
    gdb_assert (location != nullptr);
    m_pieces.emplace_back (location, bit_size);
  }

  void set_completed (bool completed)
  {
    m_completed = completed;
  };

  bool is_completed () const
  {
    return m_completed;
  };

  void read (const frame_info_ptr &frame, gdb_byte *buf, int buf_bit_offset,
	     size_t bit_size, LONGEST bits_to_skip, size_t location_bit_limit,
	     bool big_endian, std::vector<range> &optimized,
	     std::vector<range> &unavailable) const override;

  void write (const frame_info_ptr &frame, const gdb_byte *buf,
	      int buf_bit_offset, size_t bit_size, LONGEST bits_to_skip,
	      size_t location_bit_limit, bool big_endian,
	      int *optimized, int *unavailable) const override;

  void read_from_gdb_value (const frame_info_ptr &frame, struct value *value,
			    int value_bit_offset,
			    LONGEST bits_to_skip, size_t bit_size,
			    size_t location_bit_limit) override;

  void write_to_gdb_value (const frame_info_ptr &frame, struct value *value,
			   int value_bit_offset,
			   LONGEST bits_to_skip, size_t bit_size,
			   size_t location_bit_limit) override;

  bool is_implicit_ptr_at (LONGEST bit_offset, int bit_length) const override;

  value *indirect_implicit_ptr (const frame_info_ptr &frame, struct type *type,
				LONGEST pointer_offset = 0,
				LONGEST bit_offset = 0,
				int bit_length = 0) const override;

  value *to_gdb_value (const frame_info_ptr &frame, struct type *type,
		       struct type *subobj_type,
		       LONGEST subobj_offset) override;

  bool is_optimized_out (const frame_info_ptr &frame, bool big_endian,
			 LONGEST bits_to_skip, size_t bit_size,
			 size_t location_bit_limit) const override;

  bool mem_addr_ranges (LONGEST bit_offset, size_t size,
			std::vector<addr_range> &ranges) const override;

private:
  /* Composite piece that contains a piece location
     description and it's size.  */
  class piece
  {
  public:
    piece (std::shared_ptr<dwarf_location> location, ULONGEST size)
    : m_location (location),
      m_size (size)
    {}

    std::shared_ptr<dwarf_location> m_location;
    ULONGEST m_size;
  };

  /* Compilation unit context of the pointer.  */
  dwarf2_per_cu_data *m_per_cu;

  /* Vector of composite pieces.  */
  std::vector<piece> m_pieces;

  /* True if location description is completed.  */
  bool m_completed = false;
};

std::shared_ptr<dwarf_location>
dwarf_composite::slice (LONGEST bit_offset, LONGEST bit_size) const
{
  /* Size 0 is never expected at this point.  */
  gdb_assert (bit_size != 0);

  unsigned int pieces_num = m_pieces.size ();
  LONGEST total_bit_size = bit_size;
  LONGEST total_bits_to_skip = m_offset * HOST_CHAR_BIT
			       + m_bit_suboffset + bit_offset;
  std::vector<piece> piece_slices;
  unsigned int i;

  for (i = 0; i < pieces_num; i++)
    {
      LONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
	break;

      total_bits_to_skip -= piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      if (total_bit_size == 0)
	break;

      gdb_assert (total_bit_size > 0);

      LONGEST slice_bit_size = m_pieces[i].m_size - total_bits_to_skip;

      if (total_bit_size < slice_bit_size)
	slice_bit_size = total_bit_size;

      auto slice = m_pieces[i].m_location->slice (total_bits_to_skip,
						  slice_bit_size);
      piece_slices.emplace_back (slice, slice_bit_size);

      total_bit_size -= slice_bit_size;
      total_bits_to_skip = 0;
    }

  unsigned int slices_num = piece_slices.size ();

  /* Only one piece found, so there is no reason to
      make a composite location description.  */
  if (slices_num == 1)
    return piece_slices[0].m_location;

  auto composite_slice
    = std::make_shared<dwarf_composite> (m_arch, m_per_cu);

  for (const class piece &piece : piece_slices)
    composite_slice->add_piece (piece.m_location, piece.m_size);

  return composite_slice;
}

void
dwarf_composite::read (const frame_info_ptr &frame, gdb_byte *buf,
		       int buf_bit_offset, size_t bit_size,
		       LONGEST bits_to_skip, size_t location_bit_limit,
		       bool big_endian, std::vector<range> &optimized,
		       std::vector<range> &unavailable) const
{
  unsigned int pieces_num = m_pieces.size ();
  LONGEST total_bits_to_skip = bits_to_skip;
  LONGEST range_bit_offset = 0;
  unsigned int i;

  if (!m_completed)
    ill_formed_expression ();

  total_bits_to_skip += m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  /* The range_bit_offset (bit offset that we need to add to any
     optimized / unavailable range) can start negative if the current
     location has an offset.  However, as we skip over pieces not
     covered by the read / the beginning of the first covered piece,
     this will get back to a positive or null value.  */
  range_bit_offset -= m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  /* Skip pieces covered by the read offset.  */
  for (i = 0; i < pieces_num; i++)
    {
      LONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
        break;

      total_bits_to_skip -= piece_bit_size;
      range_bit_offset += piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      std::vector<range> piece_optimized, piece_unavailable;
      LONGEST piece_bit_size = m_pieces[i].m_size;
      LONGEST actual_bit_size = piece_bit_size;

      if (actual_bit_size > bit_size)
        actual_bit_size = bit_size;

      m_pieces[i].m_location->read (frame, buf, buf_bit_offset,
				    actual_bit_size, total_bits_to_skip,
				    piece_bit_size, big_endian,
				    piece_optimized, piece_unavailable);

      for (auto &&piece_range : piece_optimized)
	optimized.push_back ({(range_bit_offset + piece_range.offset),
			      piece_range.length});

      for (auto &&piece_range : piece_unavailable)
	unavailable.push_back ({(range_bit_offset + piece_range.offset),
				piece_range.length});

      if (bit_size == actual_bit_size)
	break;

      buf_bit_offset += actual_bit_size;
      bit_size -= actual_bit_size;
      range_bit_offset += actual_bit_size - total_bits_to_skip;
      total_bits_to_skip = 0;
    }
}

void
dwarf_composite::write (const frame_info_ptr &frame, const gdb_byte *buf,
			int buf_bit_offset, size_t bit_size,
			LONGEST bits_to_skip, size_t location_bit_limit,
			bool big_endian, int *optimized,
			int *unavailable) const
{
  LONGEST total_bits_to_skip = bits_to_skip;
  unsigned int pieces_num = m_pieces.size ();
  unsigned int i;

  if (!m_completed)
    ill_formed_expression ();

  total_bits_to_skip += m_offset * HOST_CHAR_BIT + m_bit_suboffset;

  /* Skip pieces covered by the write offset.  */
  for (i = 0; i < pieces_num; i++)
    {
      LONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
	break;

      total_bits_to_skip -= piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      LONGEST piece_bit_size = m_pieces[i].m_size;
      LONGEST actual_bit_size = piece_bit_size;

      if (actual_bit_size > bit_size)
        actual_bit_size = bit_size;

      m_pieces[i].m_location->write (frame, buf, buf_bit_offset,
				     actual_bit_size, total_bits_to_skip,
				     piece_bit_size, big_endian,
				     optimized, unavailable);

      if (bit_size == actual_bit_size || *optimized || *unavailable)
	break;

      buf_bit_offset += actual_bit_size;
      bit_size -= actual_bit_size;
    }
}

void
dwarf_composite::read_from_gdb_value (const frame_info_ptr &frame,
				      struct value *value,
				      int value_bit_offset,
				      LONGEST bits_to_skip, size_t bit_size,
				      size_t location_bit_limit)
{
  ULONGEST total_bits_to_skip
    = bits_to_skip + HOST_CHAR_BIT * m_offset + m_bit_suboffset;
  ULONGEST remaining_bit_size = bit_size;
  ULONGEST bit_offset = value_bit_offset;
  unsigned int pieces_num = m_pieces.size ();
  unsigned int i;

  /* Advance to the first non-skipped piece.  */
  for (i = 0; i < pieces_num; i++)
    {
      ULONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
	break;

      total_bits_to_skip -= piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      auto location = m_pieces[i].m_location;
      ULONGEST piece_bit_size = m_pieces[i].m_size;
      size_t this_bit_size = piece_bit_size - total_bits_to_skip;

      if (this_bit_size > remaining_bit_size)
	this_bit_size = remaining_bit_size;

      location->read_from_gdb_value (frame, value, bit_offset,
				     total_bits_to_skip, this_bit_size,
				     piece_bit_size);

      bit_offset += this_bit_size;
      remaining_bit_size -= this_bit_size;
      total_bits_to_skip = 0;
    }
}

void
dwarf_composite::write_to_gdb_value (const frame_info_ptr &frame,
				     struct value *value,
				     int value_bit_offset,
				     LONGEST bits_to_skip, size_t bit_size,
				     size_t location_bit_limit)
{
  ULONGEST total_bits_to_skip
    = bits_to_skip + HOST_CHAR_BIT * m_offset + m_bit_suboffset;
  ULONGEST remaining_bit_size = bit_size;
  ULONGEST bit_offset = value_bit_offset;
  unsigned int pieces_num = m_pieces.size ();
  unsigned int i;

  /* Advance to the first non-skipped piece.  */
  for (i = 0; i < pieces_num; i++)
    {
      ULONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
	break;

      total_bits_to_skip -= piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      auto location = m_pieces[i].m_location;
      ULONGEST piece_bit_size = m_pieces[i].m_size;
      size_t this_bit_size = piece_bit_size - total_bits_to_skip;

      if (this_bit_size > remaining_bit_size)
	this_bit_size = remaining_bit_size;

      location->write_to_gdb_value (frame, value, bit_offset,
				    total_bits_to_skip, this_bit_size,
				    piece_bit_size);

      bit_offset += this_bit_size;
      remaining_bit_size -= this_bit_size;
      total_bits_to_skip = 0;
    }

  if (remaining_bit_size != 0)
    value->mark_bits_optimized_out (bit_offset,
				    bit_offset + remaining_bit_size);
}

bool
dwarf_composite::is_implicit_ptr_at (LONGEST bit_offset, int bit_length) const
{
  /* Advance to the first non-skipped piece.  */
  unsigned int pieces_num = m_pieces.size ();
  LONGEST total_bit_offset = bit_offset;
  LONGEST total_bit_length = bit_length;

  total_bit_offset += HOST_CHAR_BIT * m_offset + m_bit_suboffset;

  for (unsigned int i = 0; i < pieces_num && total_bit_length != 0; i++)
    {
      ULONGEST read_bit_length = m_pieces[i].m_size;

      if (total_bit_offset >= read_bit_length)
	{
	  total_bit_offset -= read_bit_length;
	  continue;
	}

      read_bit_length -= total_bit_offset;

      if (total_bit_length < read_bit_length)
	read_bit_length = total_bit_length;

      if (m_pieces[i].m_location->is_implicit_ptr_at (total_bit_offset,
						      read_bit_length))
	return true;

      total_bit_offset = 0;
      total_bit_length -= read_bit_length;
    }

    /* The case where the requested range goes outside of the
       underlying location range is currently described as a
       access through a synthetic pointer.  Check for this kind
       of access seems to be covered by the same closure hook as
       the implicit pointer check.  This means that if the
       composite location description doesn't describe the whole
       requested range, true needs to be returned here.  */
    if (total_bit_length != 0)
      return true;

    return false;
}

value *
dwarf_composite::indirect_implicit_ptr (const frame_info_ptr &frame,
					struct type *type,
					LONGEST pointer_offset,
					LONGEST bit_offset,
					int bit_length) const
{
  /* Advance to the first non-skipped piece.  */
  unsigned int pieces_num = m_pieces.size ();
  LONGEST total_bit_offset = HOST_CHAR_BIT * m_offset
			     + m_bit_suboffset + bit_offset;

  for (unsigned int i = 0; i < pieces_num; i++)
    {
      ULONGEST read_bit_length = m_pieces[i].m_size;

      if (total_bit_offset >= read_bit_length)
	{
	  total_bit_offset -= read_bit_length;
	  continue;
	}

      read_bit_length -= total_bit_offset;

      if (bit_length < read_bit_length)
	read_bit_length = bit_length;

      return m_pieces[i].m_location->indirect_implicit_ptr (frame, type,
							    pointer_offset,
							    total_bit_offset,
							    read_bit_length);
    }

  return nullptr;
}

value *
dwarf_composite::to_gdb_value (const frame_info_ptr &frame, struct type *type,
			       struct type *subobj_type,
			       LONGEST subobj_offset)
{
  size_t pieces_num = m_pieces.size ();
  ULONGEST bit_size = 0;
  m_completed = true;

  if (subobj_type == nullptr)
    subobj_type = type;

  for (unsigned int i = 0; i < pieces_num; i++)
    bit_size += m_pieces[i].m_size;

  /* Complain if the expression is larger than the size of the
     outer type.  */
  if (bit_size > HOST_CHAR_BIT * type->length ())
    invalid_synthetic_pointer ();

  computed_closure *closure;

  /* If compilation unit information is not available
     we are in a CFI context.  */
  if (m_per_cu == nullptr)
    closure = new computed_closure (std::make_shared<dwarf_composite> (*this),
				    frame);
  else
    closure = new computed_closure (std::make_shared<dwarf_composite> (*this),
				    get_frame_id (frame));

  closure->incref ();

  value *retval
    = value::allocate_computed (subobj_type, &closure_value_funcs, closure);
  retval->set_offset (subobj_offset);

  return retval;
}

bool
dwarf_composite::is_optimized_out (const frame_info_ptr &frame,
				   bool big_endian, LONGEST bits_to_skip,
				   size_t bit_size,
				   size_t location_bit_limit) const
{
  ULONGEST total_bits_to_skip
    = bits_to_skip + HOST_CHAR_BIT * m_offset + m_bit_suboffset;
  ULONGEST remaining_bit_size = bit_size;
  unsigned int pieces_num = m_pieces.size ();
  unsigned int i;

  /* Advance to the first non-skipped piece.  */
  for (i = 0; i < pieces_num; i++)
    {
      ULONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bits_to_skip < piece_bit_size)
	break;

      total_bits_to_skip -= piece_bit_size;
    }

  for (; i < pieces_num; i++)
    {
      auto location = m_pieces[i].m_location;
      ULONGEST piece_bit_size = m_pieces[i].m_size;
      size_t this_bit_size = piece_bit_size - total_bits_to_skip;

      if (this_bit_size > remaining_bit_size)
	this_bit_size = remaining_bit_size;

      if (location->is_optimized_out (frame, big_endian, total_bits_to_skip,
				      this_bit_size, piece_bit_size))
	return true;

      remaining_bit_size -= this_bit_size;
      total_bits_to_skip = 0;
    }

  return false;
}

bool
dwarf_composite::mem_addr_ranges (LONGEST bit_offset, size_t size,
				  std::vector<addr_range> &ranges) const
{
  ULONGEST total_bit_offset
    = bit_offset + HOST_CHAR_BIT * m_offset + m_bit_suboffset;
  unsigned int pieces_num = m_pieces.size ();
  unsigned int i;

  /* Advance to the first non-skipped piece.  */
  for (i = 0; i < pieces_num; i++)
    {
      ULONGEST piece_bit_size = m_pieces[i].m_size;

      if (total_bit_offset < piece_bit_size)
	break;

      total_bit_offset -= piece_bit_size;
    }

  size_t total_size = 0;
  for (; i < pieces_num; i++)
    {
      if (total_size >= size)
	break;

      size_t piece_size = m_pieces[i].m_size;

      /* If the piece is bigger then the leftover amount,
	 get that amount.  */
      if (total_size + piece_size > size)
	piece_size = size - total_size;

      if (!m_pieces[i].m_location->mem_addr_ranges (total_bit_offset, piece_size,
						    ranges))
	return false;

      total_size += piece_size;
      total_bit_offset = 0;
    }

  return true;
}

/* Set of functions that perform different arithmetic operations
   on a given DWARF value arguments.

   Currently the existing struct value operations are used under the
   hood to avoid the code duplication.  Vector types are planned to be
   promoted to base types in the future anyway which means that the
   operations subset needed is just going to grow anyway.  */

/* Compare two DWARF value's ARG1 and ARG2 for equality in a context
   of a value entry comparison.  */

static bool
dwarf_value_equal_op (std::shared_ptr<const dwarf_value> arg1,
		      std::shared_ptr<const dwarf_value> arg2)
{
  value *arg1_value = arg1->convert_to_gdb_value (arg1->get_type ());
  value *arg2_value = arg2->convert_to_gdb_value (arg2->get_type ());

  return value_equal (arg1_value, arg2_value);
}

/* Compare if DWARF value ARG1 is lesser then DWARF value ARG2 in a
   context of a value entry comparison.   */

static bool
dwarf_value_less_op (std::shared_ptr<const dwarf_value> arg1,
		     std::shared_ptr<const dwarf_value> arg2)
{
  value *arg1_value = arg1->convert_to_gdb_value (arg1->get_type ());
  value *arg2_value = arg2->convert_to_gdb_value (arg2->get_type ());

  return value_less (arg1_value, arg2_value);
}

/* Apply binary operation OP on given ARG1 and ARG2 arguments
   and return a new value entry containing the result of that
   operation.  */

static std::shared_ptr<dwarf_value>
dwarf_value_binary_op (std::shared_ptr<const dwarf_value> arg1,
		       std::shared_ptr<const dwarf_value> arg2,
		       exp_opcode op)
{
  value *arg1_value = arg1->convert_to_gdb_value (arg1->get_type ());
  value *arg2_value = arg2->convert_to_gdb_value (arg2->get_type ());
  value *result = value_binop (arg1_value, arg2_value, op);

  return std::make_shared<dwarf_value> (result->contents_raw ().data (),
				        result->type ());
}

/* Apply a negation operation on ARG and return a new value entry
   containing the result of that operation.  */

static std::shared_ptr<dwarf_value>
dwarf_value_negation_op (std::shared_ptr<const dwarf_value> arg)
{
  value *result
    = value_neg (arg->convert_to_gdb_value (arg->get_type ()));
  return std::make_shared<dwarf_value> (result->contents_raw ().data (),
					result->type ());
}

/* Apply a complement operation on ARG and return a new value entry
   containing the result of that operation.  */

static std::shared_ptr<dwarf_value>
dwarf_value_complement_op (std::shared_ptr<const dwarf_value> arg)
{
  value *result
    = value_complement (arg->convert_to_gdb_value (arg->get_type ()));
  return std::make_shared<dwarf_value> (result->contents_raw ().data (),
					result->type ());
}

/* Apply a cast operation on ARG and return a new value entry
   containing the result of that operation.  */

static std::shared_ptr<dwarf_value>
dwarf_value_cast_op (std::shared_ptr<const dwarf_value> arg, struct type *type)
{
  value *result
    = value_cast (type, arg->convert_to_gdb_value (arg->get_type ()));
  return std::make_shared<dwarf_value> (result->contents_raw ().data (), type);
}

static void *
copy_value_closure (const value *v)
{
  computed_closure *closure = ((computed_closure*) v->computed_closure ());

  if (closure == nullptr)
    internal_error (_("invalid closure type"));

  closure->incref ();
  return closure;
}

static void
free_value_closure (value *v)
{
  computed_closure *closure = ((computed_closure*) v->computed_closure ());

  if (closure == nullptr)
    internal_error (_("invalid closure type"));

  closure->decref ();

  if (closure->refcount () == 0)
    delete closure;
}

/* Read or write a closure value V.  If FROM != NULL, operate in "write
   mode": copy FROM into the closure comprising V.  If FROM == NULL,
   operate in "read mode": fetch the contents of the (lazy) value V by
   composing it from its closure.  */

static void
rw_closure_value (value *v, value *from)
{
  LONGEST bit_offset = 0, max_bit_size;
  computed_closure *closure = (computed_closure*) v->computed_closure ();
  bool big_endian = type_byte_order (v->type ()) == BFD_ENDIAN_BIG;
  auto location = closure->get_location ();

  ULONGEST bits_to_skip = HOST_CHAR_BIT * v->offset ();

  /* If there are bits that don't complete a byte, count them in.  */
  if (v->bitsize ())
    {
      bits_to_skip += HOST_CHAR_BIT * v->parent ()->offset () + v->bitpos ();
      if (from != NULL && big_endian)
	{
	  /* Use the least significant bits of FROM.  */
	  max_bit_size = HOST_CHAR_BIT * from->type ()->length ();
	  bit_offset = max_bit_size - v->bitsize ();
	}
      else
	max_bit_size = v->bitsize ();
    }
  else
    max_bit_size = HOST_CHAR_BIT * v->type ()->length ();

  frame_info_ptr frame = closure->get_frame ();

  if (frame == NULL)
    frame = frame_find_by_id (closure->get_frame_id ());

  if (from == NULL)
    {
      location->write_to_gdb_value (frame, v, bit_offset, bits_to_skip,
				    max_bit_size - bit_offset, 0);
    }
  else
    {
      location->read_from_gdb_value (frame, from, bit_offset, bits_to_skip,
				     max_bit_size - bit_offset, 0);
    }
}

/* Read or write a closure value V.  If FROM != NULL, operate in "write
   mode": copy FROM into the closure comprising V.  If FROM == NULL,
   operate in "read mode": fetch the contents of the (lazy) value V by
   composing it from its closure.  */

static bool
is_optimized_out_closure_value (value *v)
{
  LONGEST max_bit_size;
  computed_closure *closure = (computed_closure*) v->computed_closure ();
  bool big_endian = type_byte_order (v->type ()) == BFD_ENDIAN_BIG;
  auto location = closure->get_location ();

  ULONGEST bits_to_skip = HOST_CHAR_BIT * v->offset ();

  /* If there are bits that don't complete a byte, count them in.  */
  if (v->bitsize ())
    {
      bits_to_skip += HOST_CHAR_BIT * v->parent ()->offset () + v->bitpos ();
      max_bit_size = v->bitsize ();
    }
  else
    max_bit_size = HOST_CHAR_BIT * v->type ()->length ();

  frame_info_ptr frame = closure->get_frame ();
  if (frame == NULL)
    frame = frame_find_by_id (closure->get_frame_id ());

  return location->is_optimized_out (frame, big_endian, bits_to_skip,
				     max_bit_size, 0);
}

static void
read_closure_value (value *v)
{
  rw_closure_value (v, NULL);
}

static void
write_closure_value (value *to, value *from)
{
  rw_closure_value (to, from);
}

/* An implementation of an lval_funcs method to see whether a value is
   a synthetic pointer.  */

static bool
check_synthetic_pointer (const value *value, LONGEST bit_offset,
			 int bit_length)
{
  LONGEST total_bit_offset = bit_offset + HOST_CHAR_BIT * value->offset ();

  if (value->bitsize ())
    total_bit_offset += value->bitpos ();

  computed_closure *closure
    = (computed_closure *) value->computed_closure ();

  return closure->get_location ()->is_implicit_ptr_at (total_bit_offset,
						       bit_length);
}

/* An implementation of an lval_funcs method to indirect through a
   pointer.  This handles the synthetic pointer case when needed.  */

static value *
indirect_closure_value (value *value)
{
  computed_closure *closure
    = (computed_closure *) value->computed_closure ();

  struct type *type = check_typedef (value->type ());
  if (type->code () != TYPE_CODE_PTR)
    return NULL;

  LONGEST bit_length = HOST_CHAR_BIT * type->length ();
  LONGEST bit_offset = HOST_CHAR_BIT * value->offset ();

  if (value->bitsize ())
    bit_offset += value->bitpos ();

  frame_info_ptr frame = get_selected_frame (_("No frame selected."));

  /* This is an offset requested by GDB, such as value subscripts.
     However, due to how synthetic pointers are implemented, this is
     always presented to us as a pointer type.  This means we have to
     sign-extend it manually as appropriate.  Use raw
     extract_signed_integer directly rather than value_as_address and
     sign extend afterwards on architectures that would need it
     (mostly everywhere except MIPS, which has signed addresses) as
     the later would go through gdbarch_pointer_to_address and thus
     return a CORE_ADDR with high bits set on architectures that
     encode address spaces and other things in CORE_ADDR.  */
  bfd_endian byte_order = gdbarch_byte_order (get_frame_arch (frame));
  LONGEST pointer_offset
    = extract_signed_integer (value->contents (), byte_order);

  return closure->get_location ()->indirect_implicit_ptr (frame, type,
							  pointer_offset,
							  bit_offset, bit_length);
}

/* Implementation of the coerce_ref method of lval_funcs for synthetic C++
   references.  */

static value *
coerce_closure_ref (const value *value)
{
  struct type *type = check_typedef (value->type ());

  if (value->bits_synthetic_pointer (value->embedded_offset (),
				     TARGET_CHAR_BIT * type->length ()))
    {
      computed_closure *closure
	= (computed_closure *) value->computed_closure ();
      frame_info_ptr frame = get_selected_frame (_("No frame selected."));

      return closure->get_location ()->indirect_implicit_ptr (frame, type);
    }
  else
    {
      /* Else: not a synthetic reference; do nothing.  */
      return NULL;
    }
}

/* Implementation of the mem_addr_ranges method of lval_funcs that
   returns all memory locations encapsulated by the closure.  */

static bool
closure_mem_addr_ranges (const struct value *value,
			 std::vector<addr_range> &ranges)
{
  LONGEST total_bit_offset = value->offset () * HOST_CHAR_BIT;

  if (value->bitsize ())
    total_bit_offset += value->bitpos ();

  computed_closure *closure
    = (computed_closure *) value->computed_closure ();

  return closure->get_location ()->mem_addr_ranges (total_bit_offset,
						    value->type ()->length (),
						    ranges);
}

/* Convert struct value VALUE to the matching DWARF entry
   representation.  ARCH describes an architecture of the new
   entry.  */

static std::shared_ptr<dwarf_entry>
gdb_value_to_dwarf_entry (gdbarch *arch, struct value *value)
{
  struct type *type = value->type ();

  LONGEST offset = value->offset ();

  switch (value->lval ())
    {
      /* We can only convert struct value to a location because
	 we can't distinguish between the implicit value and
	 not_lval.  */
    case not_lval:
      {
	gdb_byte *contents_start = value->contents_raw ().data () + offset;

	return std::make_shared<dwarf_implicit> (arch, contents_start,
						 type->length (),
						 type_byte_order (type));
      }
    case lval_memory:
      {
	arch_addr_space_id address_space = ARCH_ADDR_SPACE_ID_DEFAULT;
	CORE_ADDR address = value->address ();

	address_space
	  = gdbarch_address_space_id_from_core_address (arch, address);
	address = gdbarch_segment_address_from_core_address (arch, address);

	return std::make_shared<dwarf_memory>
	  (arch, address, 0, value->stack (), address_space);
      }
    case lval_register:
      return std::make_shared<dwarf_register> (arch, value->regnum (),
					       false, offset);
    case lval_computed:
      {
	/* Dwarf entry is enclosed by the closure anyway so we just
	   need to unwrap it here.  */
	computed_closure *closure
	  = (computed_closure *) value->computed_closure ();
	auto location = closure->get_location ()->clone ()->to_location (arch);

	if (location == nullptr)
	  internal_error (_("invalid closure type"));

	location->add_bit_offset (offset * HOST_CHAR_BIT);
	return location;
      }
    default:
      internal_error (_("invalid location type"));
  }
}

/* Given context CTX, section offset SECT_OFF, and compilation unit
   data PER_CU, execute the "variable value" operation on the DIE
   found at SECT_OFF.  */

static value *
sect_variable_value (sect_offset sect_off,
		     dwarf2_per_cu_data *per_cu,
		     dwarf2_per_objfile *per_objfile)
{
  const char *var_name = nullptr;
  struct type *die_type
    = dwarf2_fetch_die_type_sect_off (sect_off, per_cu, per_objfile,
				      &var_name);

  if (die_type == NULL)
    error (_("Bad DW_OP_GNU_variable_value DIE."));

  /* Note: Things still work when the following test is removed.  This
     test and error is here to conform to the proposed specification.  */
  if (die_type->code () != TYPE_CODE_INT
      && die_type->code () != TYPE_CODE_ENUM
      && die_type->code () != TYPE_CODE_RANGE
      && die_type->code () != TYPE_CODE_PTR)
    error (_("Type of DW_OP_GNU_variable_value DIE must be an integer or pointer."));

  if (var_name != nullptr)
    {
      value *result = compute_var_value (var_name);
      if (result != nullptr)
	return result;
    }

  struct type *type = lookup_pointer_type (die_type);
  frame_info_ptr frame = get_selected_frame (_("No frame selected."));
  return indirect_synthetic_pointer (sect_off, 0, per_cu, per_objfile, frame,
				     type, true);
}

/* The expression evaluator works with a dwarf_expr_context, describing
   its current state and its callbacks.  */
struct dwarf_expr_context
{
  /* Create a new context for the expression evaluator.

     We should ever only pass in the PER_OBJFILE and the ADDR_SIZE
     information should be retrievable from there.  The PER_OBJFILE
     contains a pointer to the PER_BFD information anyway and the
     address size information must be the same for the whole BFD.   */
  dwarf_expr_context (struct dwarf2_per_objfile *per_objfile,
		      int addr_size);

  /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
     FRAME context.  INIT_VALUES vector contains values that are
     expected to be pushed on a DWARF expression stack before the
     evaluation.  AS_LVAL defines if the returned struct value is
     expected to be a value or a location description.  Where TYPE,
     SUBOBJ_TYPE and SUBOBJ_OFFSET describe expected struct value
     representation of the evaluation result.  The ADDR_INFO property
     can be specified to override the range of memory addresses with
     the passed in buffer.  */
  struct value *evaluate (const gdb_byte *addr, size_t len, bool as_lval,
			  dwarf2_per_cu_data *per_cu,
			  const frame_info_ptr &frame,
			  std::vector<value *> *init_values,
			  const property_addr_info *addr_info,
			  struct type *type, struct type *subobj_type,
			  LONGEST subobj_offset);

private:
  /* The stack of DWARF entries.  */
  std::vector<std::shared_ptr<dwarf_entry>> m_stack;

  /* Target address size in bytes.  */
  int m_addr_size;

  /* The current depth of dwarf expression recursion, via DW_OP_call*,
     DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
     depth we'll tolerate before raising an error.  */
  int m_recursion_depth = 0, m_max_recursion_depth = 0x100;

  /* We evaluate the expression in the context of this objfile.  */
  dwarf2_per_objfile *m_per_objfile;

  /* Frame information used for the evaluation.  */
  frame_info_ptr m_frame = nullptr;

  /* Compilation unit used for the evaluation.  */
  dwarf2_per_cu_data *m_per_cu = nullptr;

  /* Property address info used for the evaluation.  */
  const property_addr_info *m_addr_info = nullptr;

  /* Scope dependency of the evaluated expression.

     A DWARF expression can be determined to be scope dependent
     (frame, thread and SIMD lane).  That information is
     gathered here during the evaluation and recorded in the resulting
     struct value object.  */
  location_scope m_scope = LOCATION_SCOPE_INFERIOR;

  /* Evaluate the expression at ADDR (LEN bytes long).  */
  void eval (const gdb_byte *addr, size_t len);

  /* Return the type used for DWARF operations where the type is
     unspecified in the DWARF spec.  Only certain sizes are
     supported.  */
  type *address_type () const;

  /* Push ENTRY onto the stack.  */
  void push (std::shared_ptr<dwarf_entry> value);

  /* Return true if the expression stack is empty.  */
  bool stack_empty_p () const;

  /* Pop a top element of the stack and add as a composite piece.
     The action is based on the context:

      - If the stack is empty, then an incomplete composite location
	description (comprised of one undefined location description),
	is pushed on the stack.

      - Otherwise, if the top stack entry is an incomplete composite
	location description, then it is updated to append a new piece
	comprised of one undefined location description.  The
	incomplete composite location description is then left on the
	stack.

      - Otherwise, if the top stack entry is a location description or
	can be converted to one, it is popped. Then:

	 - If the top stack entry (after popping) is a location
	   description comprised of one incomplete composite location
	   description, then it is updated to append a new piece
	   specified by the previously popped location description.
	   The incomplete composite location description is then left
	   on the stack.

	 - Otherwise, a new location description comprised of one
	   incomplete composite location description, with a new piece
	   specified by the previously popped location description, is
	   pushed on the stack.

      - Otherwise, the DWARF expression is ill-formed  */
  std::shared_ptr<dwarf_entry> add_piece (ULONGEST bit_size,
					  ULONGEST bit_offset);

  /* It pops three stack entries.  The first must be an integral type
     value that represents a bit mask.  The second must be a location
     description that represents the one-location description.  The
     third must be a location description that represents the
     zero-location description.

     A complete composite location description created with parts from
     either of the two location description, based on the bit mask,
     is pushed on top of the DWARF stack.  PIECE_BIT_SIZE represent
     a size in bits of each piece and PIECES_COUNT represents a number
     of pieces required.  */
  std::shared_ptr<dwarf_entry> create_select_composite
    (ULONGEST piece_bit_size, ULONGEST pieces_count);

  /* It pops one stack entry that must be a location description and is
     treated as a piece location description.

     A complete composite location storage is created with PIECES_COUNT
     identical pieces and pushed on the DWARF stack.  Each pieces has a
     bit size of PIECE_BIT_SIZE.  */
  std::shared_ptr<dwarf_entry> create_extend_composite
    (ULONGEST piece_bit_size, ULONGEST pieces_count);

  /* Evaluator for the LLVM extension opcodes.  Using the context in
    this object, evaluate the following LLVM operation.  */
  const gdb_byte *execute_llvm_stack_op (dwarf_llvm_user op,
					 const gdb_byte *op_ptr,
					 const gdb_byte *op_end);

  /* The engine for the expression evaluator.  Using the context in this
     object, evaluate the expression between OP_PTR and OP_END.  */
  void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);

  /* Pop the top item off of the stack.  */
  void pop ();

  /* Retrieve the N'th item on the stack.  */
  std::shared_ptr<dwarf_entry> fetch (int n);

  /* Fetch the result of the expression evaluation in a form of
     a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET
     describe the source level representation of that result.
     AS_LVAL defines if the fetched struct value is expected to
     be a value or a location description.  */
  value *fetch_result (struct type *type, struct type *subobj_type,
		       LONGEST subobj_offset, bool as_lval);

  /* Return the location expression for the frame base attribute, in
     START and LENGTH.  The result must be live until the current
     expression evaluation is complete.  */
  void get_frame_base (const gdb_byte **start, size_t *length);

  /* Return the base type given by the indicated DIE at DIE_CU_OFF.
     This can throw an exception if the DIE is invalid or does not
     represent a base type.  */
  type *get_base_type (cu_offset die_cu_off);

  /* Execute DW_AT_location expression for the DWARF expression
     subroutine in the DIE at DIE_CU_OFF in the CU.  Do not touch
     STACK while it being passed to and returned from the called DWARF
     subroutine.  */
  void dwarf_call (cu_offset die_cu_off);

  /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
     parameter matching KIND and KIND_U at the caller of specified
     BATON. If DEREF_SIZE is not -1 then use DW_AT_call_data_value
     instead of DW_AT_call_value.  */
  void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
				   union call_site_parameter_u kind_u,
				   int deref_size);
};

/* Return the type used for DWARF operations where the type is
   unspecified in the DWARF spec.  Only certain sizes are
   supported.  */

type *
dwarf_expr_context::address_type () const
{
  return ::address_type (this->m_per_objfile->objfile->arch (),
			 this->m_addr_size);
}

/* Create a new context for the expression evaluator.  */

dwarf_expr_context::dwarf_expr_context (dwarf2_per_objfile *per_objfile,
					int addr_size)
: m_addr_size (addr_size),
  m_per_objfile (per_objfile)
{
}

void
dwarf_expr_context::push (std::shared_ptr<dwarf_entry> entry)
{
  this->m_stack.emplace_back (entry);
}

void
dwarf_expr_context::pop ()
{
  if (this->m_stack.empty ())
    error (_("dwarf expression stack underflow"));

  this->m_stack.pop_back ();
}

std::shared_ptr<dwarf_entry>
dwarf_expr_context::fetch (int n)
{
  if (this->m_stack.size () <= n)
     error (_("Asked for position %d of stack, "
	      "stack only has %zu elements on it."),
	    n, this->m_stack.size ());
  return this->m_stack[this->m_stack.size () - (1 + n)];
}

void
dwarf_expr_context::get_frame_base (const gdb_byte **start,
				    size_t * length)
{
  ensure_have_frame (this->m_frame, "DW_OP_fbreg");

  const block *bl = get_frame_block (this->m_frame, NULL);

  if (bl == NULL)
    error (_("frame address is not available."));

  /* Use block_linkage_function, which returns a real (not inlined)
     function, instead of get_frame_function, which may return an
     inlined function.  */
  symbol *framefunc = bl->linkage_function ();

  /* If we found a frame-relative symbol then it was certainly within
     some function associated with a frame. If we can't find the frame,
     something has gone wrong.  */
  gdb_assert (framefunc != NULL);

  func_get_frame_base_dwarf_block (framefunc,
				   get_frame_address_in_block (this->m_frame),
				   start, length);
}

type *
dwarf_expr_context::get_base_type (cu_offset die_cu_off)
{
  if (this->m_per_cu == nullptr)
    return builtin_type (this->m_per_objfile->objfile->arch ())->builtin_int;

  type *result = dwarf2_get_die_type (die_cu_off, this->m_per_cu,
				      this->m_per_objfile);

  if (result == nullptr)
    error (_("Could not find type for operation"));
  return result;
}

void
dwarf_expr_context::dwarf_call (cu_offset die_cu_off)
{
  ensure_have_per_cu (this->m_per_cu, "DW_OP_call");

  frame_info_ptr frame = this->m_frame;

  auto get_pc_from_frame = [frame] ()
    {
      ensure_have_frame (frame, "DW_OP_call");
      return get_frame_address_in_block (frame);
    };

  dwarf2_locexpr_baton block
    = dwarf2_fetch_die_loc_cu_off (die_cu_off, this->m_per_cu,
				   this->m_per_objfile, get_pc_from_frame);

  /* DW_OP_call_ref is currently not supported.  */
  gdb_assert (block.per_cu == this->m_per_cu);

  this->eval (block.data, block.size);
}

void
dwarf_expr_context::push_dwarf_reg_entry_value
  (call_site_parameter_kind kind, call_site_parameter_u kind_u, int deref_size)
{
  ensure_have_per_cu (this->m_per_cu, "DW_OP_entry_value");
  ensure_have_frame (this->m_frame, "DW_OP_entry_value");

  dwarf2_per_cu_data *caller_per_cu;
  dwarf2_per_objfile *caller_per_objfile;
  frame_info_ptr caller_frame = get_prev_frame (this->m_frame);
  struct call_site_parameter *parameter
    = dwarf_expr_reg_to_entry_parameter (this->m_frame, kind, kind_u,
					 &caller_per_cu,
					 &caller_per_objfile);
  const gdb_byte *data_src
    = deref_size == -1 ? parameter->value : parameter->data_value;
  size_t size
    = deref_size == -1 ? parameter->value_size : parameter->data_value_size;

  /* DEREF_SIZE size is not verified here.  */
  if (data_src == nullptr)
    throw_error (NO_ENTRY_VALUE_ERROR,
		 _("Cannot resolve DW_AT_call_data_value"));

  /* We are about to evaluate an expression in the context of the caller
     of the current frame.  This evaluation context may be different from
     the current (callee's) context), so temporarily set the caller's context.

     It is possible for the caller to be from a different objfile from the
     callee if the call is made through a function pointer.  */
  scoped_restore save_frame = make_scoped_restore (&this->m_frame,
						   caller_frame);
  scoped_restore save_per_cu = make_scoped_restore (&this->m_per_cu,
						    caller_per_cu);
  scoped_restore save_addr_info = make_scoped_restore (&this->m_addr_info,
						       nullptr);
  scoped_restore save_per_objfile = make_scoped_restore (&this->m_per_objfile,
							 caller_per_objfile);
  scoped_restore save_addr_size = make_scoped_restore (&this->m_addr_size);
  this->m_addr_size = this->m_per_cu->addr_size ();

  this->eval (data_src, size);
}

value *
dwarf_expr_context::fetch_result (struct type *type, struct type *subobj_type,
				  LONGEST subobj_offset, bool as_lval)
{
  if (type == nullptr)
    type = address_type ();

  if (subobj_type == nullptr)
    subobj_type = type;

  /* Ensure that, if TYPE or SUBOBJ_TYPE are typedefs, their length is filled
     in instead of being zero.  */
  check_typedef (type);
  check_typedef (subobj_type);

  auto entry = fetch (0);

  if (!as_lval)
    entry = entry->to_value (address_type ());
  else
    entry = entry->to_location (this->m_per_objfile->objfile->arch ());

  value *result = entry->to_gdb_value (this->m_frame, type,
				       subobj_type, subobj_offset);

  result->set_scope (this->m_scope | result->scope ());
  return result;
}

value *
dwarf_expr_context::evaluate (const gdb_byte *addr, size_t len, bool as_lval,
			      dwarf2_per_cu_data *per_cu,
			      const frame_info_ptr &frame,
			      std::vector<value *> *init_values,
			      const property_addr_info *addr_info,
			      struct type *type, struct type *subobj_type,
			      LONGEST subobj_offset)
{
  this->m_per_cu = per_cu;
  this->m_frame = frame;
  this->m_addr_info = addr_info;
  gdbarch *arch = this->m_per_objfile->objfile->arch ();

  if (init_values != nullptr)
    for (unsigned int i = 0; i < init_values->size (); i++)
      push (gdb_value_to_dwarf_entry (arch, (*init_values)[i]));

  eval (addr, len);
  return fetch_result (type, subobj_type, subobj_offset, as_lval);
}

/* Require that TYPE be an integral type; throw an exception if not.  */

static void
dwarf_require_integral (struct type *type)
{
  if (type->code () != TYPE_CODE_INT
      && type->code () != TYPE_CODE_CHAR
      && type->code () != TYPE_CODE_BOOL)
    error (_("integral type expected in DWARF expression"));
}

/* Return the unsigned form of TYPE.  TYPE is necessarily an integral
   type.  */

static struct type *
get_unsigned_type (struct gdbarch *gdbarch, struct type *type)
{
  switch (type->length ())
    {
    case 1:
      return builtin_type (gdbarch)->builtin_uint8;
    case 2:
      return builtin_type (gdbarch)->builtin_uint16;
    case 4:
      return builtin_type (gdbarch)->builtin_uint32;
    case 8:
      return builtin_type (gdbarch)->builtin_uint64;
    default:
      error (_("no unsigned variant found for type, while evaluating "
	       "DWARF expression"));
    }
}

/* Return the signed form of TYPE.  TYPE is necessarily an integral
   type.  */

static struct type *
get_signed_type (struct gdbarch *gdbarch, struct type *type)
{
  switch (type->length ())
    {
    case 1:
      return builtin_type (gdbarch)->builtin_int8;
    case 2:
      return builtin_type (gdbarch)->builtin_int16;
    case 4:
      return builtin_type (gdbarch)->builtin_int32;
    case 8:
      return builtin_type (gdbarch)->builtin_int64;
    default:
      error (_("no signed variant found for type, while evaluating "
	       "DWARF expression"));
    }
}

bool
dwarf_expr_context::stack_empty_p () const
{
  return this->m_stack.empty ();
}

std::shared_ptr<dwarf_entry>
dwarf_expr_context::add_piece (ULONGEST bit_size, ULONGEST bit_offset)
{
  std::shared_ptr<dwarf_location> piece;
  std::shared_ptr<dwarf_composite> composite;
  gdbarch *arch = this->m_per_objfile->objfile->arch ();

  if (stack_empty_p ())
    piece = std::make_shared<dwarf_undefined> (arch);
  else
    {
      piece = fetch (0)->to_location (arch);

      if (auto old_composite
	    = std::dynamic_pointer_cast<dwarf_composite> (piece))
	{
	  if (!old_composite->is_completed ())
	    piece = std::make_shared<dwarf_undefined> (arch);
	}
      else if (std::dynamic_pointer_cast<dwarf_undefined> (piece) != nullptr)
	pop ();
    }

  if (std::dynamic_pointer_cast<dwarf_undefined> (piece) == nullptr)
    {
      piece->add_bit_offset (bit_offset);
      pop ();
    }

  if (stack_empty_p ()
      || std::dynamic_pointer_cast<dwarf_composite> (fetch (0)) == nullptr)
    composite = std::make_shared<dwarf_composite> (arch, this->m_per_cu);
  else
    {
      composite = std::dynamic_pointer_cast<dwarf_composite> (fetch (0));

      if (composite->is_completed ())
	composite = std::make_shared<dwarf_composite> (arch, this->m_per_cu);
      else
	pop ();
    }

  composite->add_piece (piece, bit_size);
  return composite;
}

std::shared_ptr<dwarf_entry>
dwarf_expr_context::create_select_composite (ULONGEST piece_bit_size,
					     ULONGEST pieces_count)
{
  std::shared_ptr<dwarf_location> zero, one;
  std::shared_ptr<dwarf_composite> composite;
  gdb::byte_vector mask_buf;
  gdb_byte* mask_buf_data;
  ULONGEST i, mask_size;
  gdbarch *arch = this->m_per_objfile->objfile->arch ();

  if (stack_empty_p () || piece_bit_size == 0 || pieces_count == 0)
    ill_formed_expression ();

  auto mask = fetch (0)->to_value (address_type ());
  type *mask_type = mask->get_type ();
  mask_size = mask_type->length ();
  dwarf_require_integral (mask_type);
  pop ();

  if (mask_size * HOST_CHAR_BIT < pieces_count)
    ill_formed_expression ();

  mask_buf.resize (mask_size);
  mask_buf_data = mask_buf.data ();

  copy_bitwise (mask_buf_data, 0, mask->get_contents (),
		0, mask_size * HOST_CHAR_BIT,
		type_byte_order (mask_type) == BFD_ENDIAN_BIG);

  if (stack_empty_p ())
    ill_formed_expression ();

  one = fetch (0)->to_location (arch);
  pop ();

  if (stack_empty_p ())
    ill_formed_expression ();

  zero = fetch (0)->to_location (arch);
  pop ();

  composite = std::make_shared<dwarf_composite> (arch, this->m_per_cu);

  for (i = 0; i < pieces_count; i++)
    {
      std::shared_ptr<dwarf_location> slice;

      if ((mask_buf_data[i / HOST_CHAR_BIT] >> (i % HOST_CHAR_BIT)) & 1)
	slice = one->slice (i * piece_bit_size, piece_bit_size);
      else
	slice = zero->slice (i * piece_bit_size, piece_bit_size);

      composite->add_piece (slice, piece_bit_size);
    }

  composite->set_completed (true);
  return composite;
}

std::shared_ptr<dwarf_entry>
dwarf_expr_context::create_extend_composite (ULONGEST piece_bit_size,
					     ULONGEST pieces_count)
{
  std::shared_ptr<dwarf_location> location;
  std::shared_ptr<dwarf_composite> composite;
  ULONGEST i;
  gdbarch *arch = this->m_per_objfile->objfile->arch ();

  if (stack_empty_p () || piece_bit_size == 0 || pieces_count == 0)
    ill_formed_expression ();

  location = fetch (0)->to_location (arch);
  pop ();

  composite = std::make_shared<dwarf_composite> (arch, this->m_per_cu);

  for (i = 0; i < pieces_count; i++)
    {
      auto piece = location->clone ();
      composite->add_piece (std::dynamic_pointer_cast<dwarf_location> (piece),
			    piece_bit_size);
    }

  composite->set_completed (true);
  return composite;
}

void
dwarf_expr_context::eval (const gdb_byte *addr, size_t len)
{
  int old_recursion_depth = this->m_recursion_depth;

  execute_stack_op (addr, addr + len);

  /* RECURSION_DEPTH becomes invalid if an exception was thrown here.  */

  gdb_assert (this->m_recursion_depth == old_recursion_depth);
}

/* See expr.h.  */

const gdb_byte *
safe_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
		   uint64_t *r)
{
  buf = gdb_read_uleb128 (buf, buf_end, r);
  if (buf == NULL)
    error (_("DWARF expression error: ran off end of buffer reading uleb128 value"));
  return buf;
}

/* See expr.h.  */

const gdb_byte *
safe_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
		   int64_t *r)
{
  buf = gdb_read_sleb128 (buf, buf_end, r);
  if (buf == NULL)
    error (_("DWARF expression error: ran off end of buffer reading sleb128 value"));
  return buf;
}

/* See expr.h.  */

const gdb_byte *
safe_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
{
  buf = gdb_skip_leb128 (buf, buf_end);
  if (buf == NULL)
    error (_("DWARF expression error: ran off end of buffer reading leb128 value"));
  return buf;
}

/* See expr.h.  */

void
dwarf_expr_require_composition (const gdb_byte *op_ptr, const gdb_byte *op_end,
				const char *op_name)
{
  if (op_ptr != op_end && *op_ptr != DW_OP_piece && *op_ptr != DW_OP_bit_piece
      && *op_ptr != DW_OP_GNU_uninit)
    error (_("DWARF-2 expression error: `%s' operations must be "
	     "used either alone or in conjunction with DW_OP_piece "
	     "or DW_OP_bit_piece."),
	   op_name);
}

/* Return true iff the types T1 and T2 are "the same".  This only does
   checks that might reasonably be needed to compare DWARF base
   types.  */

static int
base_types_equal_p (struct type *t1, struct type *t2)
{
  if (t1->code () != t2->code ())
    return 0;
  if (t1->is_unsigned () != t2->is_unsigned ())
    return 0;
  return t1->length () == t2->length ();
}

/* See expr.h.  */

int
dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end)
{
  uint64_t dwarf_reg;

  if (buf_end <= buf)
    return -1;
  if (*buf >= DW_OP_reg0 && *buf <= DW_OP_reg31)
    {
      if (buf_end - buf != 1)
	return -1;
      return *buf - DW_OP_reg0;
    }

  if (*buf == DW_OP_regval_type || *buf == DW_OP_GNU_regval_type)
    {
      buf++;
      buf = gdb_read_uleb128 (buf, buf_end, &dwarf_reg);
      if (buf == NULL)
	return -1;
      buf = gdb_skip_leb128 (buf, buf_end);
      if (buf == NULL)
	return -1;
    }
  else if (*buf == DW_OP_regx)
    {
      buf++;
      buf = gdb_read_uleb128 (buf, buf_end, &dwarf_reg);
      if (buf == NULL)
	return -1;
    }
  else
    return -1;
  if (buf != buf_end || (int) dwarf_reg != dwarf_reg)
    return -1;
  return dwarf_reg;
}

/* See expr.h.  */

int
dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf, const gdb_byte *buf_end,
				CORE_ADDR *deref_size_return)
{
  uint64_t dwarf_reg;
  int64_t offset;

  if (buf_end <= buf)
    return -1;

  if (*buf >= DW_OP_breg0 && *buf <= DW_OP_breg31)
    {
      dwarf_reg = *buf - DW_OP_breg0;
      buf++;
      if (buf >= buf_end)
	return -1;
    }
  else if (*buf == DW_OP_bregx)
    {
      buf++;
      buf = gdb_read_uleb128 (buf, buf_end, &dwarf_reg);
      if (buf == NULL)
	return -1;
      if ((int) dwarf_reg != dwarf_reg)
       return -1;
    }
  else
    return -1;

  buf = gdb_read_sleb128 (buf, buf_end, &offset);
  if (buf == NULL)
    return -1;
  if (offset != 0)
    return -1;

  if (*buf == DW_OP_deref)
    {
      buf++;
      *deref_size_return = -1;
    }
  else if (*buf == DW_OP_deref_size)
    {
      buf++;
      if (buf >= buf_end)
       return -1;
      *deref_size_return = *buf++;
    }
  else
    return -1;

  if (buf != buf_end)
    return -1;

  return dwarf_reg;
}

/* See expr.h.  */

int
dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
			  CORE_ADDR *fb_offset_return)
{
  int64_t fb_offset;

  if (buf_end <= buf)
    return 0;

  if (*buf != DW_OP_fbreg)
    return 0;
  buf++;

  buf = gdb_read_sleb128 (buf, buf_end, &fb_offset);
  if (buf == NULL)
    return 0;
  *fb_offset_return = fb_offset;
  if (buf != buf_end || fb_offset != (LONGEST) *fb_offset_return)
    return 0;

  return 1;
}

/* See expr.h.  */

int
dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
			  const gdb_byte *buf_end, CORE_ADDR *sp_offset_return)
{
  uint64_t dwarf_reg;
  int64_t sp_offset;

  if (buf_end <= buf)
    return 0;
  if (*buf >= DW_OP_breg0 && *buf <= DW_OP_breg31)
    {
      dwarf_reg = *buf - DW_OP_breg0;
      buf++;
    }
  else
    {
      if (*buf != DW_OP_bregx)
       return 0;
      buf++;
      buf = gdb_read_uleb128 (buf, buf_end, &dwarf_reg);
      if (buf == NULL)
	return 0;
    }

  if (dwarf_reg_to_regnum (gdbarch, dwarf_reg)
      != gdbarch_sp_regnum (gdbarch))
    return 0;

  buf = gdb_read_sleb128 (buf, buf_end, &sp_offset);
  if (buf == NULL)
    return 0;
  *sp_offset_return = sp_offset;
  if (buf != buf_end || sp_offset != (LONGEST) *sp_offset_return)
    return 0;

  return 1;
}

const gdb_byte *
dwarf_expr_context::execute_llvm_stack_op (dwarf_llvm_user op,
					   const gdb_byte *op_ptr,
					   const gdb_byte *op_end)
{
  if (op == 0)
    error (_("Unhandled DWARF expression LLVM user opcode 0x%x"), op);

  gdbarch *arch = this->m_per_objfile->objfile->arch ();
  type *address_type = this->address_type ();
  uint64_t uoffset, reg;
  int64_t offset;
  std::shared_ptr<dwarf_entry> result_entry;

  switch (op)
    {
      case DW_OP_LLVM_USER_form_aspace_address:
	{
	  auto aspace_value = fetch (0)->to_value (address_type);
	  pop ();

	  auto address_value = fetch (0)->to_value (address_type);
	  pop ();

	  dwarf_require_integral (aspace_value->get_type ());
	  arch_addr_space_id address_space
	    = gdbarch_dwarf_address_space_to_address_space_id
		(arch, aspace_value->to_long ());
	  CORE_ADDR address = address_value->to_long ();
	  address
	    = gdbarch_segment_address_to_core_address (arch, address_space,
						       address);
	  location_scope scope
	    = gdbarch_address_scope (arch, inferior_ptid, address);

	  if (scope_matches (scope, LOCATION_SCOPE_LANE))
	    {
	      ensure_have_simd_lane ("DW_OP_LLVM_form_aspace_address");
	      m_scope |= LOCATION_SCOPE_LANE;
	    }
	  else if (scope_matches (scope, LOCATION_SCOPE_THREAD))
	    {
	      ensure_have_thread ("DW_OP_LLVM_form_aspace_address");
	      m_scope |= LOCATION_SCOPE_THREAD;
	    }

	  result_entry
	    = std::make_shared<dwarf_memory> (arch,
					      address_value->to_long (), 0,
					      false, address_space);
	}
	break;

      case DW_OP_LLVM_USER_offset:
	{
	  auto value = fetch (0)->to_value (address_type);
	  pop ();

	  dwarf_require_integral (value->get_type ());

	  auto location = fetch (0)->to_location (arch);
	  pop ();

	  location->add_bit_offset (value->to_long () * HOST_CHAR_BIT);
	  result_entry = location;
	}
	break;

      case DW_OP_LLVM_USER_offset_constu:
	{
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);

	  auto location = fetch (0)->to_location (arch);
	  pop ();

	  location->add_bit_offset (uoffset * HOST_CHAR_BIT);
	  result_entry = location;
	}
	break;

      case DW_OP_LLVM_USER_bit_offset:
	{
	  auto value = fetch (0)->to_value (address_type);
	  pop ();

	  dwarf_require_integral (value->get_type ());

	  auto location = fetch (0)->to_location (arch);
	  pop ();

	  location->add_bit_offset (value->to_long ());
	  result_entry = location;
	}
	break;

      case DW_OP_LLVM_USER_call_frame_entry_reg:
	op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);

	ensure_have_frame (this->m_frame, "DW_OP_LLVM_call_frame_entry_reg");

	result_entry
	  = std::make_shared<dwarf_register> (arch, reg, true);
	m_scope |= LOCATION_SCOPE_FRAME;
	break;

      case DW_OP_LLVM_USER_undefined:
	result_entry = std::make_shared<dwarf_undefined> (arch);
	break;

      case DW_OP_LLVM_USER_piece_end:
	{
	  auto entry = fetch (0);

	  auto composite
	    = std::dynamic_pointer_cast<dwarf_composite> (entry);

	  if (composite == nullptr)
	    ill_formed_expression ();

	  if (composite->is_completed ())
	    ill_formed_expression ();

	  composite->set_completed (true);
	  return op_ptr;
	}

      case DW_OP_LLVM_USER_select_bit_piece:
	{
	  uint64_t piece_bit_size, pieces_count;

	  /* Record the piece.  */
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &piece_bit_size);
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &pieces_count);
	  result_entry
	    = create_select_composite (piece_bit_size, pieces_count);
	}
	break;

      case DW_OP_LLVM_USER_extend:
	{
	  uint64_t piece_bit_size, pieces_count;

	  /* Record the piece.  */
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &piece_bit_size);
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &pieces_count);
	  result_entry
	    = create_extend_composite (piece_bit_size, pieces_count);
	}
	break;

      case DW_OP_LLVM_USER_aspace_bregx:
	{
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);
	  op_ptr = safe_read_sleb128 (op_ptr, op_end, &offset);

	  ensure_have_frame (this->m_frame, "DW_OP_LLVM_aspace_bregx");

	  int regnum = dwarf_reg_to_regnum_or_error (arch, reg);
	  ULONGEST reg_size = register_size (arch, regnum);
	  std::shared_ptr<dwarf_location> location
	    = std::make_shared<dwarf_register> (arch, reg);
	  std::shared_ptr<dwarf_value> address_value
	    = location->deref (this->m_frame, this->m_addr_info,
			       address_type, reg_size);
	  location = address_value->to_location (arch);

	  auto memory
	    = std::dynamic_pointer_cast<dwarf_memory> (location);

	  if (memory == nullptr)
	    ill_formed_expression ();

	  memory->add_bit_offset (offset * HOST_CHAR_BIT);

	  auto aspace_value = fetch (0)->to_value (address_type);
	  pop ();

	  dwarf_require_integral (aspace_value->get_type ());
	  arch_addr_space_id address_space
	    = gdbarch_dwarf_address_space_to_address_space_id
		(arch, aspace_value->to_long ());
	  memory->set_address_space (address_space);
	  result_entry = memory;

	  CORE_ADDR address
	    = gdbarch_segment_address_to_core_address
		(arch, address_space, address_value->to_long ());
	  location_scope scope
	    = gdbarch_address_scope (arch, inferior_ptid, address);

	  /* Only need to check if there is a SIMD lane in focus,
	     previous check ensured that there is a frame so there
	     must also be a thread in focus too.  */
	  if (scope_matches (scope, LOCATION_SCOPE_LANE))
	    {
	      ensure_have_simd_lane ("DW_OP_LLVM_aspace_bregx");
	      m_scope |= LOCATION_SCOPE_LANE;
	    }

	  m_scope |= LOCATION_SCOPE_FRAME;
	}
	break;

      case DW_OP_LLVM_USER_push_lane:
	{
	  ensure_have_simd_lane ("DW_OP_LLVM_push_lane");
	  ULONGEST lane = inferior_thread ()->current_simd_lane ();
	  result_entry = std::make_shared<dwarf_value> (lane, address_type);
	  m_scope |= LOCATION_SCOPE_LANE;
	}
	break;

      default:
	return op_ptr;
    }

  /* Most things push a result value.  */
  gdb_assert (result_entry != NULL);
  push (result_entry);
  return op_ptr;
}

void
dwarf_expr_context::execute_stack_op (const gdb_byte *op_ptr,
				      const gdb_byte *op_end)
{
  gdbarch *arch = this->m_per_objfile->objfile->arch ();
  bfd_endian byte_order = gdbarch_byte_order (arch);
  /* Old-style "untyped" DWARF values need special treatment in a
     couple of places, specifically DW_OP_mod and DW_OP_shr.  We need
     a special type for these values so we can distinguish them from
     values that have an explicit type, because explicitly-typed
     values do not need special treatment.  This special type must be
     different (in the `==' sense) from any base type coming from the
     CU.  */
  type *address_type = this->address_type ();

  if (this->m_recursion_depth > this->m_max_recursion_depth)
    error (_("DWARF-2 expression error: Loop detected (%d)."),
	   this->m_recursion_depth);
  this->m_recursion_depth++;

  while (op_ptr < op_end)
    {
      dwarf_location_atom op = (dwarf_location_atom) *op_ptr++;
      ULONGEST result;
      uint64_t uoffset, reg;
      int64_t offset;
      std::shared_ptr<dwarf_entry> result_entry = nullptr;

      /* The DWARF expression might have a bug causing an infinite
	 loop.  In that case, quitting is the only way out.  */
      QUIT;

      switch (op)
	{
	case DW_OP_lit0:
	case DW_OP_lit1:
	case DW_OP_lit2:
	case DW_OP_lit3:
	case DW_OP_lit4:
	case DW_OP_lit5:
	case DW_OP_lit6:
	case DW_OP_lit7:
	case DW_OP_lit8:
	case DW_OP_lit9:
	case DW_OP_lit10:
	case DW_OP_lit11:
	case DW_OP_lit12:
	case DW_OP_lit13:
	case DW_OP_lit14:
	case DW_OP_lit15:
	case DW_OP_lit16:
	case DW_OP_lit17:
	case DW_OP_lit18:
	case DW_OP_lit19:
	case DW_OP_lit20:
	case DW_OP_lit21:
	case DW_OP_lit22:
	case DW_OP_lit23:
	case DW_OP_lit24:
	case DW_OP_lit25:
	case DW_OP_lit26:
	case DW_OP_lit27:
	case DW_OP_lit28:
	case DW_OP_lit29:
	case DW_OP_lit30:
	case DW_OP_lit31:
	  result = op - DW_OP_lit0;
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  break;

	case DW_OP_addr:
	  result = extract_unsigned_integer (op_ptr,
					     this->m_addr_size, byte_order);
	  op_ptr += this->m_addr_size;
	  /* Some versions of GCC emit DW_OP_addr before
	     DW_OP_GNU_push_tls_address.  In this case the value is an
	     index, not an address.  We don't support things like
	     branching between the address and the TLS op.  */
	  if (op_ptr >= op_end || *op_ptr != DW_OP_GNU_push_tls_address)
	    {
	      result += this->m_per_objfile->objfile->text_section_offset ();
	      result_entry = std::make_shared<dwarf_memory> (arch, result);
	    }
	  else
	    /* This is a special case where the value is expected to be
	       created instead of memory location.  */
	    result_entry = std::make_shared<dwarf_value> (result, address_type);
	  break;

	case DW_OP_addrx:
	case DW_OP_GNU_addr_index:
	  ensure_have_per_cu (this->m_per_cu, "DW_OP_addrx");

	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	  result = (m_per_objfile->relocate
		     (dwarf2_read_addr_index (this->m_per_cu,
					      this->m_per_objfile,
					      uoffset)));
	  result_entry = std::make_shared<dwarf_memory> (arch, result);
	  break;
	case DW_OP_constx:
	case DW_OP_GNU_const_index:
	  ensure_have_per_cu (this->m_per_cu, "DW_OP_constx");

	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	  result = (ULONGEST) dwarf2_read_addr_index (this->m_per_cu,
						      this->m_per_objfile,
						      uoffset);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  break;

	case DW_OP_const1u:
	  result = extract_unsigned_integer (op_ptr, 1, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 1;
	  break;
	case DW_OP_const1s:
	  result = extract_signed_integer (op_ptr, 1, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 1;
	  break;
	case DW_OP_const2u:
	  result = extract_unsigned_integer (op_ptr, 2, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 2;
	  break;
	case DW_OP_const2s:
	  result = extract_signed_integer (op_ptr, 2, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 2;
	  break;
	case DW_OP_const4u:
	  result = extract_unsigned_integer (op_ptr, 4, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 4;
	  break;
	case DW_OP_const4s:
	  result = extract_signed_integer (op_ptr, 4, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 4;
	  break;
	case DW_OP_const8u:
	  result = extract_unsigned_integer (op_ptr, 8, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 8;
	  break;
	case DW_OP_const8s:
	  result = extract_signed_integer (op_ptr, 8, byte_order);
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  op_ptr += 8;
	  break;
	case DW_OP_constu:
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	  result = uoffset;
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  break;
	case DW_OP_consts:
	  op_ptr = safe_read_sleb128 (op_ptr, op_end, &offset);
	  result = offset;
	  result_entry = std::make_shared<dwarf_value> (result, address_type);
	  break;

	/* The DW_OP_reg operations are required to occur alone in
	   location expressions.  */
	case DW_OP_reg0:
	case DW_OP_reg1:
	case DW_OP_reg2:
	case DW_OP_reg3:
	case DW_OP_reg4:
	case DW_OP_reg5:
	case DW_OP_reg6:
	case DW_OP_reg7:
	case DW_OP_reg8:
	case DW_OP_reg9:
	case DW_OP_reg10:
	case DW_OP_reg11:
	case DW_OP_reg12:
	case DW_OP_reg13:
	case DW_OP_reg14:
	case DW_OP_reg15:
	case DW_OP_reg16:
	case DW_OP_reg17:
	case DW_OP_reg18:
	case DW_OP_reg19:
	case DW_OP_reg20:
	case DW_OP_reg21:
	case DW_OP_reg22:
	case DW_OP_reg23:
	case DW_OP_reg24:
	case DW_OP_reg25:
	case DW_OP_reg26:
	case DW_OP_reg27:
	case DW_OP_reg28:
	case DW_OP_reg29:
	case DW_OP_reg30:
	case DW_OP_reg31:
	  ensure_have_frame (this->m_frame, "DW_OP_reg");

	  result = op - DW_OP_reg0;
	  result_entry = std::make_shared<dwarf_register> (arch, result);
	  m_scope |= LOCATION_SCOPE_FRAME;
	  break;

	case DW_OP_regx:
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);
	  ensure_have_frame (this->m_frame, "DW_OP_regx");

	  result = reg;
	  result_entry = std::make_shared<dwarf_register> (arch, reg);
	  m_scope |= LOCATION_SCOPE_FRAME;
	  break;

	case DW_OP_implicit_value:
	  {
	    uint64_t len;

	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &len);
	    if (op_ptr + len > op_end)
	      error (_("DW_OP_implicit_value: too few bytes available."));
	    result_entry = std::make_shared<dwarf_implicit>
	      (arch, op_ptr, len, BFD_ENDIAN_UNKNOWN);
	    op_ptr += len;
	  }
	  break;

	case DW_OP_stack_value:
	  {
	    auto value = fetch (0)->to_value (address_type);
	    pop ();

	    struct type* type = value->get_type ();

	    result_entry = std::make_shared<dwarf_implicit>
	      (arch, value->get_contents (),
	       type->length (), type_byte_order (type));
	  }
	  break;

	case DW_OP_implicit_pointer:
	case DW_OP_GNU_implicit_pointer:
	  {
	    int64_t len;
	    ensure_have_per_cu (this->m_per_cu, "DW_OP_implicit_pointer");

	    int ref_addr_size = this->m_per_cu->ref_addr_size ();

	    /* The referred-to DIE of sect_offset kind.  */
	    sect_offset die_offset
	      = (sect_offset) extract_unsigned_integer (op_ptr, ref_addr_size,
							byte_order);
	    op_ptr += ref_addr_size;

	    /* The byte offset into the data.  */
	    op_ptr = safe_read_sleb128 (op_ptr, op_end, &len);
	    result_entry = std::make_shared<dwarf_implicit_pointer>
	      (arch, this->m_per_objfile, this->m_per_cu,
	       this->m_addr_size, die_offset, len);
	  }
	  break;

	case DW_OP_breg0:
	case DW_OP_breg1:
	case DW_OP_breg2:
	case DW_OP_breg3:
	case DW_OP_breg4:
	case DW_OP_breg5:
	case DW_OP_breg6:
	case DW_OP_breg7:
	case DW_OP_breg8:
	case DW_OP_breg9:
	case DW_OP_breg10:
	case DW_OP_breg11:
	case DW_OP_breg12:
	case DW_OP_breg13:
	case DW_OP_breg14:
	case DW_OP_breg15:
	case DW_OP_breg16:
	case DW_OP_breg17:
	case DW_OP_breg18:
	case DW_OP_breg19:
	case DW_OP_breg20:
	case DW_OP_breg21:
	case DW_OP_breg22:
	case DW_OP_breg23:
	case DW_OP_breg24:
	case DW_OP_breg25:
	case DW_OP_breg26:
	case DW_OP_breg27:
	case DW_OP_breg28:
	case DW_OP_breg29:
	case DW_OP_breg30:
	case DW_OP_breg31:
	  {
	    op_ptr = safe_read_sleb128 (op_ptr, op_end, &offset);
	    ensure_have_frame (this->m_frame, "DW_OP_breg");

	    reg = op - DW_OP_breg0;

	    int regnum = dwarf_reg_to_regnum_or_error (arch, reg);
	    ULONGEST reg_size = register_size (arch, regnum);
	    std::shared_ptr<dwarf_location> location
	      = std::make_shared<dwarf_register> (arch, reg);
	    result_entry = location->deref (this->m_frame, this->m_addr_info,
					    address_type, reg_size);

	    location = result_entry->to_location (arch);
	    location->add_bit_offset (offset * HOST_CHAR_BIT);
	    result_entry = location;
	    m_scope |= LOCATION_SCOPE_FRAME;
	  }
	  break;
	case DW_OP_bregx:
	  {
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);
	    op_ptr = safe_read_sleb128 (op_ptr, op_end, &offset);
	    ensure_have_frame (this->m_frame, "DW_OP_bregx");

	    int regnum = dwarf_reg_to_regnum_or_error (arch, reg);
	    ULONGEST reg_size = register_size (arch, regnum);
	    std::shared_ptr<dwarf_location> location
	      = std::make_shared<dwarf_register> (arch, reg);
	    result_entry = location->deref (this->m_frame, this->m_addr_info,
					    address_type, reg_size);

	    location = result_entry->to_location (arch);
	    location->add_bit_offset (offset * HOST_CHAR_BIT);
	    result_entry = location;
	    m_scope |= LOCATION_SCOPE_FRAME;
	  }
	  break;
	case DW_OP_fbreg:
	  {
	    op_ptr = safe_read_sleb128 (op_ptr, op_end, &offset);

	    /* Rather than create a whole new context, we simply
	       backup the current stack locally and install a new empty stack,
	       then reset it afterwards, effectively erasing whatever the
	       recursive call put there.  */
	    std::vector<std::shared_ptr<dwarf_entry>> saved_stack
	      = std::move (this->m_stack);
	    this->m_stack.clear ();

	    const gdb_byte *datastart;
	    size_t datalen;

	    this->get_frame_base (&datastart, &datalen);
	    eval (datastart, datalen);
	    result_entry = fetch (0);

	    auto reg_loc
	      = std::dynamic_pointer_cast<dwarf_register> (result_entry);

	    if (reg_loc != nullptr)
	      result_entry = reg_loc->deref (this->m_frame,
					     this->m_addr_info, address_type);

	    result_entry = result_entry->to_location (arch);
	    auto memory
	      = std::dynamic_pointer_cast<dwarf_memory> (result_entry);

	    /* If we get anything else then memory location here,
	       the DWARF standard defines the expression as ill formed.  */
	    if (memory == nullptr)
	      ill_formed_expression ();

	    memory->add_bit_offset (offset * HOST_CHAR_BIT);
	    memory->set_stack (true);
	    result_entry = memory;

	    /* Restore the content of the original stack.  */
	    this->m_stack = std::move (saved_stack);
	    m_scope |= LOCATION_SCOPE_FRAME;
	  }
	  break;

	case DW_OP_dup:
	  result_entry = fetch (0)->clone ();
	  break;

	case DW_OP_drop:
	  pop ();
	  goto no_push;

	case DW_OP_pick:
	  offset = *op_ptr++;
	  result_entry = fetch (offset);
	  break;
	  
	case DW_OP_swap:
	  {
	    if (this->m_stack.size () < 2)
	       error (_("Not enough elements for "
			"DW_OP_swap.  Need 2, have %zu."),
		      this->m_stack.size ());

	    auto temp = this->m_stack[this->m_stack.size () - 1];
	    this->m_stack[this->m_stack.size () - 1]
	      = this->m_stack[this->m_stack.size () - 2];
	    this->m_stack[this->m_stack.size () - 2] = temp;
	    goto no_push;
	  }

	case DW_OP_over:
	  result_entry = fetch (1)->clone ();
	  break;

	case DW_OP_rot:
	  {
	    if (this->m_stack.size () < 3)
	       error (_("Not enough elements for "
			"DW_OP_rot.  Need 3, have %zu."),
		      this->m_stack.size ());

	    auto temp = this->m_stack[this->m_stack.size () - 1];
	    this->m_stack[this->m_stack.size () - 1]
	      = this->m_stack[this->m_stack.size () - 2];
	    this->m_stack[this->m_stack.size () - 2]
	      = this->m_stack[this->m_stack.size () - 3];
	    this->m_stack[this->m_stack.size () - 3] = temp;
	    goto no_push;
	  }

	case DW_OP_deref:
	case DW_OP_deref_size:
	case DW_OP_deref_type:
	case DW_OP_GNU_deref_type:
	  {
	    int addr_size = (op == DW_OP_deref ? this->m_addr_size : *op_ptr++);
	    struct type *type = address_type;

	    if (op == DW_OP_deref_type || op == DW_OP_GNU_deref_type)
	      {
		op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
		cu_offset type_die_cu_off = (cu_offset) uoffset;
		type = get_base_type (type_die_cu_off);
		addr_size = type->length ();
	      }

	    auto location = fetch (0)->to_location (arch);
	    result_entry = location->deref (this->m_frame, this->m_addr_info,
					    type, addr_size);
	    pop ();
	  }
	  break;

	case DW_OP_abs:
	case DW_OP_neg:
	case DW_OP_not:
	case DW_OP_plus_uconst:
	  {
	    /* Unary operations.  */
	    auto arg = fetch (0)->to_value (address_type);
	    pop ();

	    switch (op)
	      {
	      case DW_OP_abs:
		{
		  value *arg_value
		    = arg->convert_to_gdb_value (arg->get_type ());

		  if (value_less (arg_value,
				  value::zero (arg->get_type (), not_lval)))
		    arg = dwarf_value_negation_op (arg);
		}
		break;
	      case DW_OP_neg:
		arg = dwarf_value_negation_op (arg);
		break;
	      case DW_OP_not:
		dwarf_require_integral (arg->get_type ());
		arg = dwarf_value_complement_op (arg);
		break;
	      case DW_OP_plus_uconst:
		dwarf_require_integral (arg->get_type ());
		op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);
		result = arg->to_long () + reg;
		arg = std::make_shared<dwarf_value> (result, address_type);
		break;
	      }
	    result_entry = arg;
	  }
	  break;

	case DW_OP_and:
	case DW_OP_div:
	case DW_OP_minus:
	case DW_OP_mod:
	case DW_OP_mul:
	case DW_OP_or:
	case DW_OP_plus:
	case DW_OP_shl:
	case DW_OP_shr:
	case DW_OP_shra:
	case DW_OP_xor:
	case DW_OP_le:
	case DW_OP_ge:
	case DW_OP_eq:
	case DW_OP_lt:
	case DW_OP_gt:
	case DW_OP_ne:
	  {
	    /* Binary operations.  */
	    auto arg2 = fetch (0)->to_value (address_type);
	    pop ();

	    auto arg1 = fetch (0)->to_value (address_type);
	    pop ();

	    if (! base_types_equal_p (arg1->get_type (), arg2->get_type ()))
	      error (_("Incompatible types on DWARF stack"));

	    std::shared_ptr<dwarf_value> op_result;

	    switch (op)
	      {
	      case DW_OP_and:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		op_result = dwarf_value_binary_op (arg1, arg2,
						   BINOP_BITWISE_AND);
		break;
	      case DW_OP_div:
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_DIV);
		break;
	      case DW_OP_minus:
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_SUB);
		break;
	      case DW_OP_mod:
		{
		  int cast_back = 0;
		  type *orig_type = arg1->get_type ();

		  /* We have to special-case "old-style" untyped values
		     -- these must have mod computed using unsigned
		     math.  */
		  if (orig_type == address_type)
		    {
		      type *utype = get_unsigned_type (arch, orig_type);

		      cast_back = 1;
		      arg1 = dwarf_value_cast_op (arg1, utype);
		      arg2 = dwarf_value_cast_op (arg2, utype);
		    }
		  /* Note that value_binop doesn't handle float or
		     decimal float here.  This seems unimportant.  */
		  op_result = dwarf_value_binary_op (arg1, arg2, BINOP_MOD);
		  if (cast_back)
		    op_result = dwarf_value_cast_op (op_result, orig_type);
		}
		break;
	      case DW_OP_mul:
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_MUL);
		break;
	      case DW_OP_or:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_BITWISE_IOR);
		break;
	      case DW_OP_plus:
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_ADD);
		break;
	      case DW_OP_shl:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_LSH);
		break;
	      case DW_OP_shr:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		if (!arg1->get_type ()->is_unsigned ())
		  {
		    type *utype = get_unsigned_type (arch, arg1->get_type ());
		    arg1 = dwarf_value_cast_op (arg1, utype);
		  }

		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_RSH);
		/* Make sure we wind up with the same type we started
		   with.  */
		if (op_result->get_type () != arg2->get_type ())
		  op_result
		    = dwarf_value_cast_op (op_result, arg2->get_type ());
		break;
	      case DW_OP_shra:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		if (arg1->get_type ()->is_unsigned ())
		  {
		    type *stype = get_signed_type (arch, arg1->get_type ());
		    arg1 = dwarf_value_cast_op (arg1, stype);
		  }

		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_RSH);
		/* Make sure we wind up with the same type we started  with.  */
		if (op_result->get_type () != arg2->get_type ())
		  op_result
		    = dwarf_value_cast_op (op_result, arg2->get_type ());
		break;
	      case DW_OP_xor:
		dwarf_require_integral (arg1->get_type ());
		dwarf_require_integral (arg2->get_type ());
		op_result
		  = dwarf_value_binary_op (arg1, arg2, BINOP_BITWISE_XOR);
		break;
	      case DW_OP_le:
		/* A <= B is !(B < A).  */
		result = ! dwarf_value_less_op (arg2, arg1);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      case DW_OP_ge:
		/* A >= B is !(A < B).  */
		result = ! dwarf_value_less_op (arg1, arg2);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      case DW_OP_eq:
		result = dwarf_value_equal_op (arg1, arg2);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      case DW_OP_lt:
		result = dwarf_value_less_op (arg1, arg2);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      case DW_OP_gt:
		/* A > B is B < A.  */
		result = dwarf_value_less_op (arg2, arg1);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      case DW_OP_ne:
		result = ! dwarf_value_equal_op (arg1, arg2);
		op_result
		  = std::make_shared<dwarf_value> (result, address_type);
		break;
	      default:
		internal_error (_("Can't be reached."));
	      }
	    result_entry = op_result;
	  }
	  break;

	case DW_OP_call_frame_cfa:
	  ensure_have_frame (this->m_frame, "DW_OP_call_frame_cfa");

	  result = dwarf2_frame_cfa (this->m_frame);
	  result_entry
	    = std::make_shared<dwarf_memory> (arch, result, 0, true);
	  m_scope |= LOCATION_SCOPE_FRAME;
	  break;

	case DW_OP_GNU_push_tls_address:
	case DW_OP_form_tls_address:
	  ensure_have_thread ("DW_OP_form_tls_address");
	  /* Variable is at a constant offset in the thread-local
	  storage block into the objfile for the current thread and
	  the dynamic linker module containing this expression.  Here
	  we return returns the offset from that base.  The top of the
	  stack has the offset from the beginning of the thread
	  control block at which the variable is located.  Nothing
	  should follow this operator, so the top of stack would be
	  returned.  */
	  result = fetch (0)->to_value (address_type)->to_long ();
	  pop ();
	  result = target_translate_tls_address (this->m_per_objfile->objfile,
						 result);
	  result_entry = std::make_shared<dwarf_memory> (arch, result);
	  m_scope |= LOCATION_SCOPE_THREAD;
	  break;

	case DW_OP_skip:
	  offset = extract_signed_integer (op_ptr, 2, byte_order);
	  op_ptr += 2;
	  op_ptr += offset;
	  goto no_push;

	case DW_OP_bra:
	  {
	    auto dwarf_value = fetch (0)->to_value (address_type);

	    offset = extract_signed_integer (op_ptr, 2, byte_order);
	    op_ptr += 2;
	    dwarf_require_integral (dwarf_value->get_type ());
	    if (dwarf_value->to_long () != 0)
	      op_ptr += offset;
	    pop ();
	  }
	  goto no_push;

	case DW_OP_nop:
	  goto no_push;

	case DW_OP_piece:
	  {
	    uint64_t size;

	    /* Record the piece.  */
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &size);
	    result_entry = add_piece (HOST_CHAR_BIT * size, 0);
	  }
	  break;

	case DW_OP_bit_piece:
	  {
	    uint64_t size, uleb_offset;

	    /* Record the piece.  */
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &size);
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &uleb_offset);
	    result_entry = add_piece (size, uleb_offset);
	  }
	  break;

	case DW_OP_GNU_uninit:
	  {
	    dwarf_expr_require_composition (op_ptr, op_end,
					    "DW_OP_GNU_uninit");

	    auto location = std::dynamic_pointer_cast<dwarf_location> (fetch (0));

	    if (location == nullptr)
	      ill_formed_expression ();

	    location->set_initialised (false);
	    result_entry = location;
	  }
	  goto no_push;

	case DW_OP_call2:
	  {
	    cu_offset cu_off
	      = (cu_offset) extract_unsigned_integer (op_ptr, 2, byte_order);
	    op_ptr += 2;
	    this->dwarf_call (cu_off);
	  }
	  goto no_push;

	case DW_OP_call4:
	  {
	    cu_offset cu_off
	      = (cu_offset) extract_unsigned_integer (op_ptr, 4, byte_order);
	    op_ptr += 4;
	    this->dwarf_call (cu_off);
	  }
	  goto no_push;

	case DW_OP_GNU_variable_value:
	  {
	    ensure_have_per_cu (this->m_per_cu, "DW_OP_GNU_variable_value");
	    int ref_addr_size = this->m_per_cu->ref_addr_size ();

	    sect_offset sect_off
	      = (sect_offset) extract_unsigned_integer (op_ptr, ref_addr_size,
							byte_order);
	    op_ptr += ref_addr_size;
	    struct value *value = sect_variable_value
	      (sect_off, this->m_per_cu, this->m_per_objfile);
	    value = value_cast (address_type, value);

	    result_entry = gdb_value_to_dwarf_entry (arch, value);

	    auto undefined
	      = std::dynamic_pointer_cast<dwarf_undefined> (result_entry);

	    if (undefined != nullptr)
	      error_value_optimized_out ();

	    auto location = result_entry->to_location (arch);
	    result_entry = location->deref (this->m_frame, this->m_addr_info,
					    address_type);
	  }
	  break;
	
	case DW_OP_entry_value:
	case DW_OP_GNU_entry_value:
	  {
	    uint64_t len;
	    CORE_ADDR deref_size;
	    union call_site_parameter_u kind_u;

	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &len);
	    if (op_ptr + len > op_end)
	      error (_("DW_OP_entry_value: too few bytes available."));

	    kind_u.dwarf_reg = dwarf_block_to_dwarf_reg (op_ptr, op_ptr + len);
	    if (kind_u.dwarf_reg != -1)
	      {
		op_ptr += len;
		this->push_dwarf_reg_entry_value (CALL_SITE_PARAMETER_DWARF_REG,
						  kind_u,
						  -1 /* deref_size */);
		goto no_push;
	      }

	    kind_u.dwarf_reg = dwarf_block_to_dwarf_reg_deref (op_ptr,
							       op_ptr + len,
							       &deref_size);
	    if (kind_u.dwarf_reg != -1)
	      {
		if (deref_size == -1)
		  deref_size = this->m_addr_size;
		op_ptr += len;
		this->push_dwarf_reg_entry_value (CALL_SITE_PARAMETER_DWARF_REG,
						  kind_u, deref_size);
		goto no_push;
	      }

	    error (_("DWARF-2 expression error: DW_OP_entry_value is "
		     "supported only for single DW_OP_reg* "
		     "or for DW_OP_breg*(0)+DW_OP_deref*"));
	  }

	case DW_OP_GNU_parameter_ref:
	  {
	    union call_site_parameter_u kind_u;

	    kind_u.param_cu_off
	      = (cu_offset) extract_unsigned_integer (op_ptr, 4, byte_order);
	    op_ptr += 4;
	    this->push_dwarf_reg_entry_value (CALL_SITE_PARAMETER_PARAM_OFFSET,
					      kind_u,
					      -1 /* deref_size */);
	  }
	  goto no_push;

	case DW_OP_const_type:
	case DW_OP_GNU_const_type:
	  {
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	    cu_offset type_die_cu_off = (cu_offset) uoffset;

	    int n = *op_ptr++;
	    const gdb_byte *data = op_ptr;
	    op_ptr += n;

	    struct type *type = get_base_type (type_die_cu_off);

	    if (type->length () != n)
	      error (_("DW_OP_const_type has different sizes for type and data"));

	    result_entry = std::make_shared<dwarf_value> (data, type);
	  }
	  break;

	case DW_OP_regval_type:
	case DW_OP_GNU_regval_type:
	  {
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &reg);
	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	    cu_offset type_die_cu_off = (cu_offset) uoffset;

	    ensure_have_frame (this->m_frame, "DW_OP_regval_type");
	    struct type *type = get_base_type (type_die_cu_off);

	    auto reg_loc
	      = std::make_shared<dwarf_register> (arch, reg);
	    result_entry
	      = reg_loc->deref (this->m_frame, this->m_addr_info, type);
	    m_scope |= LOCATION_SCOPE_FRAME;
	  }
	  break;

	case DW_OP_convert:
	case DW_OP_GNU_convert:
	case DW_OP_reinterpret:
	case DW_OP_GNU_reinterpret:
	  {
	    std::shared_ptr<dwarf_value> value
	      = fetch (0)->to_value (address_type);

	    pop ();

	    op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	    cu_offset type_die_cu_off = (cu_offset) uoffset;

	    struct type *type;

	    if (to_underlying (type_die_cu_off) == 0)
	      type = address_type;
	    else
	      type = get_base_type (type_die_cu_off);

	    if (op == DW_OP_convert || op == DW_OP_GNU_convert)
	      value = dwarf_value_cast_op (value, type);
	    else if (type == value->get_type ())
	      {
		/* Nothing.  */
	      }
	    else if (type->length () != value->get_type ()->length ())
	      error (_("DW_OP_reinterpret has wrong size"));
	    else
	      value
		= std::make_shared<dwarf_value> (value->get_contents (), type);
	    result_entry = value;
	  }
	  break;

	case DW_OP_push_object_address:
	  if (this->m_addr_info == nullptr)
	    error (_("Location address is not set."));

	  /* Return the address of the object we are currently observing.  */
	  result_entry
	    = std::make_shared<dwarf_memory> (arch, this->m_addr_info->addr);
	  break;

	case DW_OP_LLVM_user:
	  op_ptr = safe_read_uleb128 (op_ptr, op_end, &uoffset);
	  op_ptr = execute_llvm_stack_op ((dwarf_llvm_user) uoffset,
					  op_ptr, op_end);
	  goto no_push;

	case DW_OP_LLVM_form_aspace_address:
	case DW_OP_LLVM_offset:
	case DW_OP_LLVM_offset_constu:
	case DW_OP_LLVM_bit_offset:
	case DW_OP_LLVM_call_frame_entry_reg:
	case DW_OP_LLVM_undefined:
	case DW_OP_LLVM_piece_end:
	case DW_OP_LLVM_select_bit_piece:
	case DW_OP_LLVM_extend:
	case DW_OP_LLVM_aspace_bregx:
	case DW_OP_LLVM_push_lane:
	  {
	    unsigned int llvm_user_op = get_DW_OP_LLVM_USER (op);

	    if (!llvm_user_op)
	      error (_("Unhandled DWARF expression opcode 0x%x"), op);

	    op_ptr = execute_llvm_stack_op ((dwarf_llvm_user) llvm_user_op,
					    op_ptr, op_end);
	  }
	  goto no_push;

	default:
	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
	}

      /* Most things push a result value.  */
      gdb_assert (result_entry != NULL);
      push (result_entry);
    no_push:
      ;
    }

  this->m_recursion_depth--;
  gdb_assert (this->m_recursion_depth >= 0);
}

/* See expr.h.  */

value *
dwarf2_evaluate (const gdb_byte *addr, size_t len, bool as_lval,
		 dwarf2_per_objfile *per_objfile, dwarf2_per_cu_data *per_cu,
		 const frame_info_ptr &frame, int addr_size,
		 std::vector<value *> *init_values,
		 const property_addr_info *addr_info,
		 struct type *type, struct type *subobj_type,
		 LONGEST subobj_offset)
{
  dwarf_expr_context ctx (per_objfile, addr_size);

  return ctx.evaluate (addr, len, as_lval, per_cu,
		       frame, init_values, addr_info,
		       type, subobj_type, subobj_offset);
}

static void
expr_observer_target_changed (struct target_ops * /* target */)
{
  context_generation++;
}

static void
expr_observer_memory_changed (CORE_ADDR /* addr */, ssize_t /* len */,
			      const bfd_byte * /* data */)
{
  context_generation++;
}

void _initialize_dwarf2_expr ();
void
_initialize_dwarf2_expr ()
{
  /* Register the observers we need to invalidate our internal caches.

     Every time a register is modified (every time a value is assigned to
     really, also applies to lval_memory values), target_changed ends-up being
     called.  Any such assignment should invalidate any cached value we hold
     in the expression evaluator.  */
  gdb::observers::target_changed.attach (expr_observer_target_changed,
					 "dwarf2_expr");

  /* Note that we can implicitly cache register values which are not currently
     stored in a register.  For example, if a register was spilled to memory
     from the previous frame, a memory change could impact a register value
     we cached.  It is possible to modify such memory without triggering
     target_changed for example using "Inferior.write_memory" in Python or
     "-data-write-memory-bytes" with MI.  Use the memory_changed observable to
     invalidate our caches if such access is done.  */
  gdb::observers::memory_changed.attach (expr_observer_memory_changed,
					 "dwarf2_expr");
}