Add support for new DWARF overlay operations

Another complex DWARF expression operations, that are usefull for
SIMD/SIMT like architectures are: DW_OP_LLVM_overlay and
DW_OP_LLVM_bit_overlay. These operations pop four stack entries,
where the first must be an integral that represents an overlay size,
the second must be an integral that represents a starting point of the
overlay from the base location, the third must be a location
description that represents the overlay location description and the
forth must be a location description that represents the base location
description.

Resulting composite location description contains parts from base
location description, overlayed by the overlay location description,
starting from the overlay offset, ending at a sum of the overlay offset
and overlay size.

A new test in gdb.dwarf2 called dw2-llvm-overlay has been also added to
test the support for both operations.

gdb/ada-lang.c

@@ -531,7 +531,7 @@ coerce_unspec_val_to_type (struct value *val, struct type *type)
       else
 	{
 	  result = allocate_value (type);
-	  value_contents_copy (result, 0, val, 0, TYPE_LENGTH (type));
+	  value_contents_copy (result, 0, val, 0, 0, TYPE_LENGTH (type));
 	}
       set_value_component_location (result, val);
       set_value_bitsize (result, value_bitsize (val));

gdb/compile/compile-loc2c.c

@@ -357,6 +357,27 @@ compute_stack_depth_worker (int start, int *need_tempvar,
 	  (*info)[offset].label = 1;
 	  break;
 
+	case DW_OP_LLVM_offset:
+	case DW_OP_LLVM_bit_offset:
+	  --stack_depth;
+	  break;
+
+	case DW_OP_LLVM_undefined:
+	  ++stack_depth;
+	  break;
+
+	case DW_OP_LLVM_select_bit_piece:
+	  stack_depth -= 2;
+	  break;
+
+	case DW_OP_LLVM_overlay:
+	case DW_OP_LLVM_bit_overlay:
+	  stack_depth -= 3;
+	  break;
+
+	case DW_OP_LLVM_extend:
+	case DW_OP_LLVM_piece_end:
+	case DW_OP_LLVM_offset_constu:
 	case DW_OP_nop:
 	  break;
 

gdb/dwarf2/expr.h

@@ -27,249 +27,56 @@
 
 struct dwarf2_per_objfile;
 
-/* The location of a value.  */
-enum dwarf_value_location
-{
-  /* The piece is in memory.
-     The value on the dwarf stack is its address.  */
-  DWARF_VALUE_MEMORY,
+/* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
+   FRAME context.  The PER_OBJFILE contains a pointer to the PER_BFD
+   information.  ADDR_SIZE defines a size of the DWARF generic type.
+   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.  */
+value *dwarf2_evaluate (const gdb_byte *addr, size_t len, bool as_lval,
+			dwarf2_per_objfile *per_objfile,
+			dwarf2_per_cu_data *per_cu,
+			frame_info *frame, int addr_size,
+			std::vector<value *> *init_values,
+			const struct property_addr_info *addr_info,
+			struct type *type = nullptr,
+			struct type *subobj_type = nullptr,
+			LONGEST subobj_offset = 0);
 
-  /* The piece is in a register.
-     The value on the dwarf stack is the register number.  */
-  DWARF_VALUE_REGISTER,
-
-  /* The piece is on the dwarf stack.  */
-  DWARF_VALUE_STACK,
-
-  /* The piece is a literal.  */
-  DWARF_VALUE_LITERAL,
-
-  /* The piece was optimized out.  */
-  DWARF_VALUE_OPTIMIZED_OUT,
-
-  /* The piece is an implicit pointer.  */
-  DWARF_VALUE_IMPLICIT_POINTER
-};
-
-/* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece.  */
-struct dwarf_expr_piece
-{
-  enum dwarf_value_location location;
-
-  union
-  {
-    struct
-    {
-      /* This piece's address, for DWARF_VALUE_MEMORY pieces.  */
-      CORE_ADDR addr;
-      /* Non-zero if the piece is known to be in memory and on
-	 the program's stack.  */
-      bool in_stack_memory;
-    } mem;
-
-    /* The piece's register number, for DWARF_VALUE_REGISTER pieces.  */
-    int regno;
-
-    /* The piece's literal value, for DWARF_VALUE_STACK pieces.  */
-    struct value *value;
-
-    struct
-    {
-      /* A pointer to the data making up this piece,
-	 for DWARF_VALUE_LITERAL pieces.  */
-      const gdb_byte *data;
-      /* The length of the available data.  */
-      ULONGEST length;
-    } literal;
-
-    /* Used for DWARF_VALUE_IMPLICIT_POINTER.  */
-    struct
-    {
-      /* The referent DIE from DW_OP_implicit_pointer.  */
-      sect_offset die_sect_off;
-      /* The byte offset into the resulting data.  */
-      LONGEST offset;
-    } ptr;
-  } v;
-
-  /* The length of the piece, in bits.  */
-  ULONGEST size;
-  /* The piece offset, in bits.  */
-  ULONGEST offset;
-};
-
-/* The dwarf expression stack.  */
-
-struct dwarf_stack_value
-{
-  dwarf_stack_value (struct value *value_, int in_stack_memory_)
-  : value (value_), in_stack_memory (in_stack_memory_)
-  {}
-
-  struct value *value;
-
-  /* True if the piece is in memory and is known to be on the program's stack.
-     It is always ok to set this to zero.  This is used, for example, to
-     optimize memory access from the target.  It can vastly speed up backtraces
-     on long latency connections when "set stack-cache on".  */
-  bool in_stack_memory;
-};
-
-/* The expression evaluator works with a dwarf_expr_context, describing
-   its current state and its callbacks.  */
-struct dwarf_expr_context
-{
-  dwarf_expr_context (dwarf2_per_objfile *per_objfile,
-		      int addr_size);
-  virtual ~dwarf_expr_context () = default;
-
-  void push_address (CORE_ADDR value, bool in_stack_memory);
-
-  /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
-     and FRAME context.
-
-     AS_LVAL defines if the returned struct value is expected to be a
-     value (false) or a location description (true).
-
-     TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the 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.  */
-  value *evaluate (const gdb_byte *addr, size_t len, bool as_lval,
-		   dwarf2_per_cu_data *per_cu, frame_info *frame,
-		   const struct property_addr_info *addr_info = nullptr,
-		   struct type *type = nullptr,
-		   struct type *subobj_type = nullptr,
-		   LONGEST subobj_offset = 0);
-
-private:
-  /* The stack of values.  */
-  std::vector<dwarf_stack_value> m_stack;
-
-  /* Target address size in bytes.  */
-  int m_addr_size = 0;
-
-  /* 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;
-
-  /* Location of the value.  */
-  dwarf_value_location m_location = DWARF_VALUE_MEMORY;
-
-  /* For DWARF_VALUE_LITERAL, the current literal value's length and
-     data.  For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
-     target DIE of sect_offset kind.  */
-  ULONGEST m_len = 0;
-  const gdb_byte *m_data = nullptr;
-
-  /* Initialization status of variable: Non-zero if variable has been
-     initialized; zero otherwise.  */
-  int m_initialized = 0;
-
-  /* A vector of pieces.
-
-     Each time DW_OP_piece is executed, we add a new element to the
-     end of this array, recording the current top of the stack, the
-     current location, and the size given as the operand to
-     DW_OP_piece.  We then pop the top value from the stack, reset the
-     location, and resume evaluation.
-
-     The Dwarf spec doesn't say whether DW_OP_piece pops the top value
-     from the stack.  We do, ensuring that clients of this interface
-     expecting to see a value left on the top of the stack (say, code
-     evaluating frame base expressions or CFA's specified with
-     DW_CFA_def_cfa_expression) will get an error if the expression
-     actually marks all the values it computes as pieces.
-
-     If an expression never uses DW_OP_piece, num_pieces will be zero.
-     (It would be nice to present these cases as expressions yielding
-     a single piece, so that callers need not distinguish between the
-     no-DW_OP_piece and one-DW_OP_piece cases.  But expressions with
-     no DW_OP_piece operations have no value to place in a piece's
-     'size' field; the size comes from the surrounding data.  So the
-     two cases need to be handled separately.)  */
-  std::vector<dwarf_expr_piece> m_pieces;
-
-  /* We evaluate the expression in the context of this objfile.  */
-  dwarf2_per_objfile *m_per_objfile;
-
-  /* Frame information used for the evaluation.  */
-  frame_info *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 struct property_addr_info *m_addr_info = nullptr;
-
-  void eval (const gdb_byte *addr, size_t len);
-  struct type *address_type () const;
-  void push (struct value *value, bool in_stack_memory);
-  bool stack_empty_p () const;
-  void add_piece (ULONGEST size, ULONGEST offset);
-  void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
-  void pop ();
-  struct value *fetch (int n);
-  CORE_ADDR fetch_address (int n);
-  bool fetch_in_stack_memory (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.  */
-  struct 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 (call_site_parameter_kind kind,
-				   call_site_parameter_u kind_u,
-				   int deref_size);
-
-  /* Read LENGTH bytes at ADDR into BUF.  This method also handles the
-     case where a caller of the evaluator passes in some data,
-     but with the address being 0.  In this situation, we arrange for
-     memory reads to come from the passed-in buffer.  */
-  void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
-};
-
-/* Return the value of register number REG (a DWARF register number),
-   read as an address in a given FRAME.  */
-CORE_ADDR read_addr_from_reg (frame_info *frame, int reg);
+/* Return the address type used of the ARCH architecture and
+   ADDR_SIZE is expected size of the type.  */
+type *address_type (gdbarch *arch, int addr_size);
 
+/* Check that the current operator is either at the end of an
+   expression, or that it is followed by a composition operator or by
+   DW_OP_GNU_uninit (which should terminate the expression).  */
 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
 				     const char *);
 
+/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_reg* return the
+   DWARF register number.  Otherwise return -1.  */
 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
 
+/* If <BUF..BUF_END] contains DW_FORM_block* with just DW_OP_breg*(0) and
+   DW_OP_deref* return the DWARF register number.  Otherwise return -1.
+   DEREF_SIZE_RETURN contains -1 for DW_OP_deref; otherwise it contains the
+   size from DW_OP_deref_size.  */
 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
 				    const gdb_byte *buf_end,
 				    CORE_ADDR *deref_size_return);
 
+/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_fbreg(X) fill
+   in FB_OFFSET_RETURN with the X offset and return 1.  Otherwise return 0.  */
 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
 			      CORE_ADDR *fb_offset_return);
 
+/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_bregSP(X) fill
+   in SP_OFFSET_RETURN with the X offset and return 1.  Otherwise return 0.
+   The matched SP register number depends on GDBARCH.  */
 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
 			      const gdb_byte *buf_end,
 			      CORE_ADDR *sp_offset_return);
@@ -309,14 +116,17 @@ gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
   return buf + bytes_read;
 }
 
+/* Helper to read a uleb128 value or throw an error.  */
 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
 					  const gdb_byte *buf_end,
 					  uint64_t *r);
 
+/* Helper to read a uleb128 value or throw an error.  */
 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
 					  const gdb_byte *buf_end,
 					  int64_t *r);
 
+/* Helper to skip a leb128 value or throw an error.  */
 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
 					 const gdb_byte *buf_end);
 

gdb/dwarf2/frame.c

@@ -193,6 +193,18 @@ dwarf2_frame_state::dwarf2_frame_state (CORE_ADDR pc_, struct dwarf2_cie *cie)
 {
 }
 
+/* Return the value of register number REG (a DWARF register number),
+   read as an address in a given FRAME.  */
+
+static CORE_ADDR
+read_addr_from_reg (frame_info *frame, int reg)
+{
+  gdbarch *arch = get_frame_arch (frame);
+  int regnum = dwarf_reg_to_regnum_or_error (arch, reg);
+
+  return address_from_register (regnum, frame);
+}
+
 /* Execute the required actions for both the DW_CFA_restore and
 DW_CFA_restore_extended instructions.  */
 static void
@@ -224,21 +236,35 @@ register %s (#%d) at %s"),
     }
 }
 
-static CORE_ADDR
+static value *
 execute_stack_op (const gdb_byte *exp, ULONGEST len, int addr_size,
 		  struct frame_info *this_frame, CORE_ADDR initial,
-		  int initial_in_stack_memory, dwarf2_per_objfile *per_objfile)
+		  int initial_in_stack_memory, dwarf2_per_objfile *per_objfile,
+		  struct type* type = nullptr, bool as_lval = true)
 {
-  dwarf_expr_context ctx (per_objfile, addr_size);
   scoped_value_mark free_values;
+  struct type *init_type = address_type (per_objfile->objfile->arch (),
+					 addr_size);
 
-  ctx.push_address (initial, initial_in_stack_memory);
-  value *result_val = ctx.evaluate (exp, len, true, nullptr, this_frame);
+  value *init_value = value_at_lazy (init_type, initial);
+  std::vector<value *> init_values;
 
-  if (VALUE_LVAL (result_val) == lval_memory)
-    return value_address (result_val);
-  else
-    return value_as_address (result_val);
+  set_value_stack (init_value, initial_in_stack_memory);
+  init_values.push_back (init_value);
+
+  value *result_val
+    = dwarf2_evaluate (exp, len, true, per_objfile, nullptr,
+		       this_frame, addr_size, &init_values, nullptr);
+
+  /* We need to clean up all the values that are not needed any more.
+     The problem with a value_ref_ptr class is that it disconnects the
+     RETVAL from the value garbage collection, so we need to make
+     a copy of that value on the stack to keep everything consistent.
+     The value_ref_ptr will clean up after itself at the end of this block.  */
+  value_ref_ptr value_holder = value_ref_ptr::new_reference (result_val);
+  free_values.free_to_mark ();
+
+  return value_copy (result_val);
 }
 
 
@@ -969,10 +995,14 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
 	  break;
 
 	case CFA_EXP:
-	  cache->cfa =
-	    execute_stack_op (fs.regs.cfa_exp, fs.regs.cfa_exp_len,
-			      cache->addr_size, this_frame, 0, 0,
-			      cache->per_objfile);
+	  {
+	    struct value *value
+	      = execute_stack_op (fs.regs.cfa_exp, fs.regs.cfa_exp_len,
+				  cache->addr_size, this_frame, 0, 0,
+				  cache->per_objfile);
+	    cache->cfa = value_address (value);
+	  }
+
 	  break;
 
 	default:
@@ -1170,24 +1200,22 @@ dwarf2_frame_prev_register (struct frame_info *this_frame, void **this_cache,
       return frame_unwind_got_register (this_frame, regnum, realnum);
 
     case DWARF2_FRAME_REG_SAVED_EXP:
-      addr = execute_stack_op (cache->reg[regnum].loc.exp.start,
+      return execute_stack_op (cache->reg[regnum].loc.exp.start,
 			       cache->reg[regnum].loc.exp.len,
-			       cache->addr_size,
-			       this_frame, cache->cfa, 1,
-			       cache->per_objfile);
-      return frame_unwind_got_memory (this_frame, regnum, addr);
+			       cache->addr_size, this_frame,
+			       cache->cfa, 1, cache->per_objfile,
+			       register_type (gdbarch, regnum));
 
     case DWARF2_FRAME_REG_SAVED_VAL_OFFSET:
       addr = cache->cfa + cache->reg[regnum].loc.offset;
       return frame_unwind_got_constant (this_frame, regnum, addr);
 
     case DWARF2_FRAME_REG_SAVED_VAL_EXP:
-      addr = execute_stack_op (cache->reg[regnum].loc.exp.start,
+      return execute_stack_op (cache->reg[regnum].loc.exp.start,
 			       cache->reg[regnum].loc.exp.len,
-			       cache->addr_size,
-			       this_frame, cache->cfa, 1,
-			       cache->per_objfile);
-      return frame_unwind_got_constant (this_frame, regnum, addr);
+			       cache->addr_size, this_frame,
+			       cache->cfa, 1, cache->per_objfile,
+			       register_type (gdbarch, regnum), false);
 
     case DWARF2_FRAME_REG_UNSPECIFIED:
       /* GCC, in its infinite wisdom decided to not provide unwind

gdb/dwarf2/loc.c

@@ -1474,15 +1474,15 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
   if (size == 0)
     return allocate_optimized_out_value (subobj_type);
 
-  dwarf_expr_context ctx (per_objfile, per_cu->addr_size ());
-
   value *retval;
   scoped_value_mark free_values;
 
   try
     {
-      retval = ctx.evaluate (data, size, as_lval, per_cu, frame, nullptr,
-			     type, subobj_type, subobj_byte_offset);
+      retval
+	= dwarf2_evaluate (data, size, as_lval, per_objfile, per_cu,
+			   frame, per_cu->addr_size (), nullptr, nullptr,
+			   type, subobj_type, subobj_byte_offset);
     }
   catch (const gdb_exception_error &ex)
     {
@@ -1553,23 +1553,28 @@ dwarf2_locexpr_baton_eval (const struct dwarf2_locexpr_baton *dlbaton,
 
   dwarf2_per_objfile *per_objfile = dlbaton->per_objfile;
   dwarf2_per_cu_data *per_cu = dlbaton->per_cu;
-  dwarf_expr_context ctx (per_objfile, per_cu->addr_size ());
 
   value *result;
   scoped_value_mark free_values;
+  std::vector<value *> init_values;
 
   if (push_initial_value)
     {
+      struct type *type = address_type (per_objfile->objfile->arch (),
+					per_cu->addr_size ());
+
       if (addr_stack != nullptr)
-	ctx.push_address (addr_stack->addr, false);
+	init_values.push_back (value_at_lazy (type, addr_stack->addr));
       else
-	ctx.push_address (0, false);
+	init_values.push_back (value_at_lazy (type, 0));
     }
 
   try
     {
-      result = ctx.evaluate (dlbaton->data, dlbaton->size,
-			     true, per_cu, frame, addr_stack);
+      result
+	= dwarf2_evaluate (dlbaton->data, dlbaton->size, true, per_objfile,
+			   per_cu, frame, per_cu->addr_size (), &init_values,
+			   addr_stack);
     }
   catch (const gdb_exception_error &ex)
     {
@@ -1919,6 +1924,12 @@ dwarf2_get_symbol_read_needs (gdb::array_view<const gdb_byte> expr,
 	case DW_OP_nop:
 	case DW_OP_GNU_uninit:
 	case DW_OP_push_object_address:
+	case DW_OP_LLVM_offset:
+	case DW_OP_LLVM_bit_offset:
+	case DW_OP_LLVM_undefined:
+	case DW_OP_LLVM_piece_end:
+	case DW_OP_LLVM_overlay:
+	case DW_OP_LLVM_bit_overlay:
 	  break;
 
 	case DW_OP_form_tls_address:
@@ -1936,6 +1947,7 @@ dwarf2_get_symbol_read_needs (gdb::array_view<const gdb_byte> expr,
 	case DW_OP_constu:
 	case DW_OP_plus_uconst:
 	case DW_OP_piece:
+	case DW_OP_LLVM_offset_constu:
 	  op_ptr = safe_skip_leb128 (op_ptr, expr_end);
 	  break;
 
@@ -1944,6 +1956,8 @@ dwarf2_get_symbol_read_needs (gdb::array_view<const gdb_byte> expr,
 	  break;
 
 	case DW_OP_bit_piece:
+	case DW_OP_LLVM_extend:
+	case DW_OP_LLVM_select_bit_piece:
 	  op_ptr = safe_skip_leb128 (op_ptr, expr_end);
 	  op_ptr = safe_skip_leb128 (op_ptr, expr_end);
 	  break;
@@ -3652,6 +3666,33 @@ disassemble_dwarf_expression (struct ui_file *stream,
 	  data += offset_size;
 	  fprintf_filtered (stream, " offset %s", phex_nz (ul, offset_size));
 	  break;
+
+	case DW_OP_LLVM_offset_constu:
+	  data = safe_read_uleb128 (data, end, &ul);
+	  fprintf_filtered (stream, " %s", pulongest (ul));
+	  break;
+
+	case DW_OP_LLVM_extend:
+	  {
+	    uint64_t count;
+
+	    data = safe_read_uleb128 (data, end, &ul);
+	    data = safe_read_uleb128 (data, end, &count);
+	    fprintf_filtered (stream, " piece size %s (bits) pieces count %s",
+	                      pulongest (ul), pulongest (count));
+	  }
+	  break;
+
+	case DW_OP_LLVM_select_bit_piece:
+	  {
+	    uint64_t count;
+
+	    data = safe_read_uleb128 (data, end, &ul);
+	    data = safe_read_uleb128 (data, end, &count);
+	    fprintf_filtered (stream, " piece size %s (bits) pieces count %s",
+			      pulongest (ul), pulongest (count));
+	  }
+	  break;
 	}
 
       fprintf_filtered (stream, "\n");

gdb/f-lang.c

@@ -161,7 +161,7 @@ fortran_bounds_all_dims (bool lbound_p,
       gdb_assert (dst_offset + TYPE_LENGTH (value_type (v))
 		  <= TYPE_LENGTH (value_type (result)));
       gdb_assert (TYPE_LENGTH (value_type (v)) == elm_len);
-      value_contents_copy (result, dst_offset, v, 0, elm_len);
+      value_contents_copy (result, dst_offset, v, 0, 0, elm_len);
 
       /* Peel another dimension of the array.  */
       array_type = TYPE_TARGET_TYPE (array_type);
@@ -289,7 +289,7 @@ protected:
      available offset.  */
   void copy_element_to_dest (struct value *elt)
   {
-    value_contents_copy (m_dest, m_dest_offset, elt, 0,
+    value_contents_copy (m_dest, m_dest_offset, elt, 0, 0,
 			 TYPE_LENGTH (value_type (elt)));
     m_dest_offset += TYPE_LENGTH (value_type (elt));
   }
@@ -736,7 +736,7 @@ fortran_array_shape (struct gdbarch *gdbarch, const language_defn *lang,
       gdb_assert (dst_offset + TYPE_LENGTH (value_type (v))
 		  <= TYPE_LENGTH (value_type (result)));
       gdb_assert (TYPE_LENGTH (value_type (v)) == elm_len);
-      value_contents_copy (result, dst_offset, v, 0, elm_len);
+      value_contents_copy (result, dst_offset, v, 0, 0, elm_len);
 
       /* Peel another dimension of the array.  */
       val_type = TYPE_TARGET_TYPE (val_type);

gdb/findvar.c

@@ -869,6 +869,7 @@ read_frame_register_value (struct value *value, struct frame_info *frame)
   struct gdbarch *gdbarch = get_frame_arch (frame);
   LONGEST offset = 0;
   LONGEST reg_offset = value_offset (value);
+  LONGEST bit_offset = value_bitpos (value);
   int regnum = VALUE_REGNUM (value);
   int len = type_length_units (check_typedef (value_type (value)));
 
@@ -892,7 +893,8 @@ read_frame_register_value (struct value *value, struct frame_info *frame)
       if (reg_len > len)
 	reg_len = len;
 
-      value_contents_copy (value, offset, regval, reg_offset, reg_len);
+      value_contents_copy (value, offset, regval, reg_offset,
+			   bit_offset, reg_len);
 
       offset += reg_len;
       len -= reg_len;

gdb/frame.c

@@ -1497,8 +1497,9 @@ get_frame_register_bytes (frame_info *frame, int regnum,
 	      return false;
 	    }
 
-	  memcpy (myaddr, value_contents_all (value).data () + offset,
-		  curr_len);
+	  memcpy (myaddr,
+		  value_contents_all (value).data ()
+		    + value_offset (value) + offset, curr_len);
 	  release_value (value);
 	}
 
@@ -1532,21 +1533,53 @@ put_frame_register_bytes (struct frame_info *frame, int regnum,
   /* Copy the data.  */
   while (len > 0)
     {
+      struct value *value = frame_unwind_register_value (frame->next,
+							 regnum);
+      /* Need to account the unwind register offset too.  */
+      offset += value == NULL ? 0 : value_offset (value);
+
+      if (offset >= register_size (gdbarch, regnum))
+	{
+	  offset -= register_size (gdbarch, regnum);
+	  regnum++;
+	  continue;
+	}
+
       int curr_len = register_size (gdbarch, regnum) - offset;
 
       if (curr_len > len)
 	curr_len = len;
 
       const gdb_byte *myaddr = buffer.data ();
-      if (curr_len == register_size (gdbarch, regnum))
+
+      /*  Computed value is a special case.  The computed callback
+	  mechanism requires a strut value argument, so we need to
+	  make one.  */
+      if (value != nullptr && VALUE_LVAL (value) == lval_computed)
+	{
+	  const lval_funcs *funcs = value_computed_funcs (value);
+
+	  if (funcs->write == nullptr)
+	    error (_("Attempt to assign to an unmodifiable value."));
+
+	  type * reg_type = register_type (gdbarch, regnum);
+
+	  struct value *from_value = allocate_value (reg_type);
+	  memcpy (value_contents_raw (from_value).data (), myaddr,
+		  TYPE_LENGTH (reg_type));
+
+	  set_value_offset (value, offset);
+
+	  funcs->write (value, from_value);
+	  release_value (from_value);
+	}
+      else if (curr_len == register_size (gdbarch, regnum))
 	{
 	  put_frame_register (frame, regnum, myaddr);
 	}
       else
 	{
-	  struct value *value = frame_unwind_register_value (frame->next,
-							     regnum);
-	  gdb_assert (value != NULL);
+	  gdb_assert (value != nullptr);
 
 	  memcpy ((char *) value_contents_writeable (value).data () + offset,
 		  myaddr, curr_len);

gdb/testsuite/gdb.dwarf2/dw2-llvm-extend.exp

@@ -0,0 +1,147 @@
+# Copyright (C) 2017-2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test the new DW_OP_LLVM_extend operation.
+#
+# The test uses a composite location description, where all the pieces
+# are allocated in the same register by using the new operation.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum 0
+
+if { [is_aarch64_target] } {
+    set regname x0
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname r0
+} elseif { [is_x86_like_target] } {
+    set regname eax
+} elseif { [is_amd64_regs_target] } {
+    set regname rax
+} else {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_src [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels int_type_label char_type_label array_type_label
+
+	    # define char type
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 7 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+
+		# All array elements are in first byte of REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name var_array_1}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_regx $dwarf_regnum
+			DW_OP_LLVM_extend 8 8
+		    } SPECIAL_expr}
+		}
+
+		# All array elements are in fourth byte of REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name var_array_2}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_regx $dwarf_regnum
+			DW_OP_LLVM_offset_constu 3
+			DW_OP_LLVM_extend 8 8
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set var \$$regname = 0x04030201" "init reg"
+
+# Determine byte order.
+set endian [get_endianness]
+
+switch $endian {
+	little {set val "0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1"}
+	big {set val "0x4, 0x4, 0x4, 0x4, 0x4, 0x4, 0x4, 0x4"}
+}
+
+gdb_test "print/x var_array_1" " = \\{${val}\\}" "var_array_1 print"
+
+switch $endian {
+	little {set val "0x4, 0x4, 0x4, 0x4, 0x4, 0x4, 0x4, 0x4"}
+	big {set val "0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1, 0x1"}
+}
+
+gdb_test "print/x var_array_2" " = \\{${val}\\}" "var_array_2 print"

gdb/testsuite/gdb.dwarf2/dw2-llvm-offset.exp

@@ -0,0 +1,328 @@
+# Copyright 2017-2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test DWARF operation that allow adding byte and bit offset to any
+# location description.
+#
+# In particular, the test uses memory and register location
+# descriptions (both as standalone and parts of the composite
+# location), and applies different byte and bit offsets to them.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum 0
+
+if { [is_aarch64_target] } {
+    set regname x0
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname r0
+} elseif { [is_x86_like_target] } {
+    set regname eax
+} elseif { [is_amd64_regs_target] } {
+    set regname rax
+} else {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_var [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels char_type_label int_type_label
+	    declare_labels array_size_4_type_label array_size_8_type_label
+
+	    # define char type.
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    # define int type.
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    # define 4 byte size array type.
+	    array_size_4_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 3 DW_FORM_udata}
+		}
+	    }
+
+	    # define 8 byte size array type.
+	    array_size_8_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 7 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+		# define original buf variable.
+		DW_TAG_variable {
+		    {DW_AT_name buf}
+		    {DW_AT_type :$array_size_4_type_label}
+		    {DW_AT_location {
+			DW_OP_addr $buf_var
+		    } SPECIAL_expr}
+		}
+
+		# defined a variable located in
+		# a third byte of the buf variable.
+		DW_TAG_variable {
+		    {DW_AT_name buf_byte_3}
+		    {DW_AT_type :$char_type_label}
+		    {DW_AT_location {
+			DW_OP_addr $buf_var
+			DW_OP_LLVM_offset_constu 2
+		    } SPECIAL_expr}
+		    {external 1 flag}
+		}
+
+		# defined a variable located in a second byte
+		# of the buf variable with a bit offset of one.
+		DW_TAG_variable {
+		    {DW_AT_name buf_byte_2_bit_1}
+		    {DW_AT_type :$char_type_label}
+		    {DW_AT_location {
+			DW_OP_addr $buf_var
+			DW_OP_lit9
+			DW_OP_LLVM_bit_offset
+		    } SPECIAL_expr}
+		    {external 1 flag}
+		}
+
+		# defined a variable located in a
+		# third byte of the REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name reg_byte_3}
+		    {DW_AT_type :$char_type_label}
+		    {DW_AT_location {
+			DW_OP_regx $dwarf_regnum
+			DW_OP_lit2
+			DW_OP_LLVM_offset
+		    } SPECIAL_expr}
+		    {external 1 flag}
+		}
+
+		# defined a variable located in a second byte of
+		# the REGNAME register with a bit offset of one.
+		DW_TAG_variable {
+		    {DW_AT_name reg_byte_2_bit_1}
+		    {DW_AT_type :$char_type_label}
+		    {DW_AT_location {
+			DW_OP_regx $dwarf_regnum
+			DW_OP_lit1
+			DW_OP_LLVM_offset
+			DW_OP_lit1
+			DW_OP_LLVM_bit_offset
+		    } SPECIAL_expr}
+		    {external 1 flag}
+		}
+
+		# Define an array variable spread in different
+		# pieces of buf variable and REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name mix_array}
+		    {DW_AT_type :$array_size_8_type_label}
+		    {DW_AT_location {
+
+			# a byte piece located in a
+			# fourth byte of the buf variable.
+			DW_OP_addr $buf_var
+			DW_OP_LLVM_offset_constu 3
+			DW_OP_piece 0x1
+
+			# a byte piece located in a
+			# third byte of the buf variable.
+			DW_OP_addr $buf_var
+			DW_OP_lit2
+			DW_OP_LLVM_offset
+			DW_OP_piece 0x1
+
+			# a byte piece located in a second byte of
+			# the buf variable with a bit offset of one.
+			DW_OP_addr $buf_var
+			DW_OP_lit1
+			DW_OP_LLVM_offset
+			DW_OP_lit1
+			DW_OP_LLVM_bit_offset
+			DW_OP_piece 0x1
+
+			# a four bit piece located in a first byte
+			# of the buf variable with a bit offset of one.
+			DW_OP_addr $buf_var
+			DW_OP_LLVM_offset_constu 0
+			DW_OP_bit_piece 0x4 0x1
+
+			# a four bit piece located in a first byte of
+			# the buf variable with a bit offset of eight.
+			DW_OP_addr $buf_var
+			DW_OP_lit1
+			DW_OP_LLVM_bit_offset
+			DW_OP_LLVM_offset_constu 0
+			DW_OP_bit_piece 0x4 0x7
+
+			# a byte piece located in a fourth
+			# byte of the REGNAME register.
+			DW_OP_regx $dwarf_regnum
+			DW_OP_LLVM_offset_constu 3
+			DW_OP_piece 0x1
+
+			# a byte piece located in a third
+			# byte of the REGNAME register.
+			DW_OP_regx $dwarf_regnum
+			DW_OP_lit2
+			DW_OP_LLVM_offset
+			DW_OP_piece 0x1
+
+			# a byte piece located in a second byte of the
+			# REGNAME register with a bit offset of one.
+			DW_OP_regx $dwarf_regnum
+			DW_OP_lit1
+			DW_OP_LLVM_offset
+			DW_OP_lit1
+			DW_OP_LLVM_bit_offset
+			DW_OP_piece 0x1
+
+			# a four bit piece located in a first byte of
+			# the REGNAME register with a bit offset of one.
+			DW_OP_regx $dwarf_regnum
+			DW_OP_LLVM_offset_constu 0
+			DW_OP_bit_piece 0x4 0x1
+
+			# a four bit piece located in a first byte of the
+			# REGNAME register with a bit offset of eight.
+			DW_OP_regx $dwarf_regnum
+			DW_OP_lit1
+			DW_OP_LLVM_bit_offset
+			DW_OP_LLVM_offset_constu 0
+			DW_OP_bit_piece 0x4 0x7
+
+		    } SPECIAL_expr}
+		    {external 1 flag}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+# Determine byte order.
+set endian [get_endianness]
+
+if { $endian != "little" } then {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+gdb_test_no_output "set var \$$regname = 0x04030201" "init reg"
+gdb_test_no_output "set var *\(\(unsigned int *\) buf\) = 0x04030201" \
+		   "init buf"
+
+gdb_test "print/x buf_byte_3" " = 0x3" "buf_byte_3 == 0x3"
+gdb_test "print/x buf_byte_2_bit_1" " = 0x81" \
+	 "print buf_byte_2_bit_1"
+gdb_test "print/x reg_byte_3" " = 0x3" "reg_byte_3 == 0x3"
+gdb_test "print/x reg_byte_2_bit_1" " = 0x81" \
+	 "print reg_byte_2_bit_1"
+
+gdb_test_no_output "set var buf_byte_3 = 0x4" "init buf_byte_3 to 0x4"
+gdb_test "print/x buf_byte_3" " = 0x4" "buf_byte_3 == 0x4"
+
+gdb_test_no_output "set var buf_byte_2_bit_1 = 0x4" \
+		   "init buf_byte_2_bit_1 to 0x4"
+gdb_test "print/x buf_byte_2_bit_1" " = 0x4" "buf_byte_2_bit_1 == 0x4"
+
+gdb_test "print/x buf" " = \\{0x1, 0x8, 0x4, 0x4\\}" "buf print"
+
+gdb_test_no_output "set var reg_byte_3 = 0x4" "init reg_byte_3 to 0x4"
+gdb_test "print/x reg_byte_3" " = 0x4" "reg_byte_3 == 0x4"
+
+gdb_test_no_output "set var reg_byte_2_bit_1 = 0x4" \
+		   "init reg_byte_2_bit_1 to 0x4"
+gdb_test "print/x reg_byte_2_bit_1" " = 0x4" "reg_byte_2_bit_1 == 0x4"
+
+gdb_test "print/x \$$regname" " = 0x4040801" "\$$regname print"
+
+gdb_test_no_output "set var \$$regname = 0x04030201" "reset reg"
+gdb_test_no_output "set var *\(\(unsigned int *\) buf\) = 0x04030201" \
+		   "reset buf"
+
+gdb_test "print/x mix_array" \
+	 " = \\{0x4, 0x3, 0x81, 0x20, 0x4, 0x3, 0x81, 0x20\\}" \
+	 "mix_array print"
+
+gdb_test_no_output "set var mix_array\[1\] = 0x4" \
+		   "set mix_array second byte"
+gdb_test_no_output "set var mix_array\[2\] = 0x4" \
+		   "set mix_array third byte"
+gdb_test_no_output "set var mix_array\[5\] = 0x4" \
+		   "set mix_array fifth byte"
+gdb_test_no_output "set var mix_array\[6\] = 0x4" \
+		   "set mix_array sixth byte"
+
+gdb_test "print/x mix_array" \
+	 " = \\{0x4, 0x4, 0x4, 0x80, 0x4, 0x4, 0x4, 0x80\\}" \
+	 "mix_array second print"
+
+gdb_test "print/x buf" " = \\{0x1, 0x8, 0x4, 0x4\\}" "buf second print"
+
+gdb_test "print/x \$$regname" " = 0x4040801" "\$$regname second print"

gdb/testsuite/gdb.dwarf2/dw2-llvm-overlay.c

@@ -0,0 +1,33 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2022 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+unsigned buff[] = {0, 1, 2, 3, 4, 5, 6, 7};
+
+void foo (unsigned dst[], unsigned src[], int len)
+{
+  asm volatile ("foo_label: .globl foo_label");
+  for (int i = 0; i < len; ++i)
+    dst[i] += src[i];
+}
+
+int
+main (void)
+{
+  asm volatile ("main_label: .globl main_label");
+  foo (buff, buff, 1);
+  return 0;
+}

gdb/testsuite/gdb.dwarf2/dw2-llvm-overlay.exp

@@ -0,0 +1,213 @@
+# Copyright (C) 2022 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test the new DW_OP_LLVM_overlay operation.
+#
+# The test uses a composite location description, where variable buff
+# address is used as a base location and a reg1 is used as an overlay
+# location.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum {0 1}
+
+if { [is_aarch64_target] } {
+    set regname {x0 x1}
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname {r0 r1}
+} elseif { [is_x86_like_target] } {
+    set regname {eax ecx}
+} elseif { [is_amd64_regs_target] } {
+    set regname {rax rdx}
+} else {
+    verbose "Skipping $gdb_test_file_name."
+    return
+}
+
+standard_testfile .c -dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buff_src [gdb_target_symbol buff]
+
+    set foo_result [function_range foo ${srcdir}/${subdir}/${srcfile}]
+    set foo_start [lindex $foo_result 0]
+    set foo_length [lindex $foo_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name $srcfile}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels int_type_label uint_type_label array_type_label
+
+	    uint_type_label: DW_TAG_base_type {
+		{DW_AT_name "uint32_t"}
+		{DW_AT_encoding @DW_ATE_unsigned}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$uint_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 7 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name foo}
+		{DW_AT_low_pc $foo_start addr}
+		{DW_AT_high_pc $foo_length data8}
+	    } {
+
+		DW_TAG_variable {
+		    {DW_AT_name dst_v1}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			# 1. Memory location description of dst elements located in memory:
+			DW_OP_addr $buff_src
+
+			# 2. Register location description of element dst\[i\] is located in a register:
+			DW_OP_regx [lindex $dwarf_regnum 1]
+
+			# 3. Offset of the register within the memory of dst:
+			DW_OP_bregx [lindex $dwarf_regnum 0] 0
+			DW_OP_lit4
+			DW_OP_mul
+
+			# 4. The size of the register element:
+			DW_OP_lit4
+
+			# 5. Make a composite location description for dst that is the memory #1 with
+			#    the register #2 positioned as an overlay at offset #3 of size #4:
+			DW_OP_LLVM_overlay
+		    } SPECIAL_expr}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name dst_v2}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			# 1. Memory location description of dst elements located in memory:
+			DW_OP_addr $buff_src
+
+			# 2. Register location description of element dst\[i\] is located in a register:
+			DW_OP_regx [lindex $dwarf_regnum 1]
+
+			# 3. Offset of the register within the memory of dst:
+			DW_OP_bregx [lindex $dwarf_regnum 0] 0
+			DW_OP_lit4
+			DW_OP_mul
+
+			# 4. The size of the register element:
+			DW_OP_lit4
+
+			# 5. Make a composite location description for dst that is the memory #1 with
+			#    the register #2 positioned as an overlay at offset #3 of size #4:
+			DW_OP_LLVM_bit_overlay
+		    } SPECIAL_expr}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name src}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_addr $buff_src
+		    } SPECIAL_expr}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name i}
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_location {
+			DW_OP_regx [lindex $dwarf_regnum 0]
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test "break foo" "Breakpoint.*at.*" "break at function foo"
+gdb_test "continue"  "Continuing\\..*Breakpoint \[0-9\]+,.*foo \\(\\).*" \
+	 "continue to foo"
+
+gdb_test_no_output "set var \$[lindex $regname 0] = 0x0" "init reg 0"
+gdb_test_no_output "set var \$[lindex $regname 1] = 0xdeadbeef" "init reg 1"
+
+# gdb_interact
+
+# Determine byte order.
+set endian [get_endianness]
+
+switch $endian {
+	little {set val_v1 "0xdeadbeef, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7"}
+	big {set val_v1 "0x7, 0x6, 0x5, 0x4, 0x3, 0x2, 0x1, 0xdeadbeef"}
+}
+
+gdb_test "print/x dst_v1" " = \\{${val_v1}\\}" "dst_v1 print i = 0"
+
+switch $endian {
+	little {set val_v2 "0xf, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7"}
+	big {set val_v2 "0x7, 0x6, 0x5, 0x4, 0x3, 0x2, 0x1, 0xf"}
+}
+
+gdb_test "print/x dst_v2" " = \\{${val_v2}\\}" "dst_v2 print i = 0"
+
+gdb_test_no_output "set var i = 0x2" "init reg 0 to 2"
+
+switch $endian {
+	little {set val_v1 "0x0, 0x1, 0xdeadbeef, 0x3, 0x4, 0x5, 0x6, 0x7"}
+	big {set val_v1 "0x7, 0x6, 0x5, 0x4, 0x3, 0xdeadbeef, 0x1, 0x0"}
+}
+
+gdb_test "print/x dst_v1" " = \\{${val_v1}\\}" "dst_v1 print i = 2"
+
+switch $endian {
+	little {set val_v2 "0xf00, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7"}
+	big {set val_v2 "0x7, 0x6, 0x5, 0x4, 0x3, 0x2, 0x1, 0xf00"}
+}
+
+gdb_test "print/x dst_v2" " = \\{${val_v2}\\}" "dst_v2 print i = 2"

gdb/testsuite/gdb.dwarf2/dw2-llvm-piece-end.exp

@@ -0,0 +1,191 @@
+# Copyright (C) 2017-2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test the nested composition location description by using the new
+# DW_OP_LLVM_piece_end operation.
+#
+# The test uses three nested levels of composite location descriptions
+# to define a location of an array.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum 0
+
+if { [is_aarch64_target] } {
+    set regname x0
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname r0
+} elseif { [is_x86_like_target] } {
+    set regname eax
+} elseif { [is_amd64_regs_target] } {
+    set regname rax
+} else {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_src [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels array_type_label int_type_label char_type_label
+
+	    # define char type
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 7 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+		# Array spread in different pieces, of which some are
+		# undefined (1st and sixth bytes) and some are either
+		# in buf variable or REGNAME register.
+		#
+		# Location consists of three nested composite levels:
+		# - Third level consists of a composite location
+		# descriptions which hold a single simple location
+		# description each.
+		# - Second level consist of two more composite location
+		# descriptions that hold two of the third level
+		# composite location descriptions.
+		# - First level holds two of the second level composite
+		# location descriptions.
+
+		DW_TAG_variable {
+		    {DW_AT_name var_array}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			# First level composite start
+			# Second level first composite start
+			# Third level first composite start
+			DW_OP_addr $buf_src
+			DW_OP_piece 0x2
+			DW_OP_LLVM_piece_end
+			# Third level first composite end
+
+			# Third level second composite start
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+			DW_OP_LLVM_piece_end
+			# Third level second composite end
+
+			DW_OP_piece 0x1
+			DW_OP_swap
+			DW_OP_piece 0x2
+			DW_OP_LLVM_piece_end
+			# Second level first composite end
+
+			# Second level second composite start
+			# Third level third composite start
+			DW_OP_regx $dwarf_regnum
+			DW_OP_piece 0x4
+			DW_OP_LLVM_piece_end
+			# Third level third composite end
+
+			# Third level fourth composite start
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+			DW_OP_LLVM_piece_end
+			# Third level fourth composite end
+
+			DW_OP_piece 0x1
+			DW_OP_swap
+			DW_OP_piece 0x4
+			DW_OP_LLVM_piece_end
+			# Second level second composite end
+
+			DW_OP_piece 0x5
+			DW_OP_swap
+			DW_OP_piece 0x3
+			DW_OP_LLVM_piece_end
+			# First level composite end
+
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set var \$$regname = 0x4030201" "init reg"
+
+# Determine byte order.
+set endian [get_endianness]
+set optimized "<optimized out>"
+
+switch $endian {
+    little {
+	set val "$optimized, 0x1, 0x2, 0x3, 0x4, $optimized, 0x0, 0x1"
+    }
+    big {
+	set val "$optimized, 0x4, 0x3, 0x2, 0x1, $optimized, 0x0, 0x1"
+    }
+}
+
+gdb_test "print/x var_array" " = \\{${val}\\}" "var_array print"
+

gdb/testsuite/gdb.dwarf2/dw2-llvm-select-bit-piece.exp

@@ -0,0 +1,138 @@
+# Copyright (C) 2017-2021 Free Software Foundation, Inc.
+# Copyright (C) 2020-2021 Advanced Micro Devices, Inc. All rights reserved.
+
+# 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/>.
+
+# Test the new DW_OP_LLVM_select_bit_piece operation.
+#
+# The test uses a composite location description, where all the pieces
+# are selected from two registers in odd/even pattern using the new
+# operation.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum {0 1}
+
+if { [is_aarch64_target] } {
+    set regname {x0 x1}
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname {r0 r1}
+} elseif { [is_x86_like_target] } {
+    set regname {eax ecx}
+} elseif { [is_amd64_regs_target] } {
+    set regname {rax rdx}
+} else {
+    verbose "Skipping $gdb_test_file_name."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_src [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels int_type_label char_type_label array_type_label
+
+	    # define char type
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 7 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+
+		# Odd array elements are in first byte of REGNAME 0 register,
+		# while even elements are in first byte of REGNAME 1 register.
+		DW_TAG_variable {
+		    {DW_AT_name var_array}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_regx [lindex $dwarf_regnum 0]
+			DW_OP_LLVM_extend 8 8
+                        DW_OP_regx [lindex $dwarf_regnum 1]
+			DW_OP_LLVM_extend 8 8
+			DW_OP_constu 0xaa
+			DW_OP_LLVM_select_bit_piece 8 8
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set var \$[lindex $regname 0] = 0x04030201" "init reg 0"
+gdb_test_no_output "set var \$[lindex $regname 1] = 0x01020304" "init reg 1"
+
+# Determine byte order.
+set endian [get_endianness]
+
+switch $endian {
+	little {set val "0x1, 0x4, 0x1, 0x4, 0x1, 0x4, 0x1, 0x4"}
+	big {set val "0x4, 0x1, 0x4, 0x1, 0x4, 0x1, 0x4, 0x1"}
+}
+
+gdb_test "print/x var_array" " = \\{${val}\\}" "var_array print"
+

gdb/testsuite/gdb.dwarf2/dw2-llvm-undefined.exp

@@ -0,0 +1,144 @@
+# Copyright 2017-2021 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test the new DW_OP_LLVM_undefined operation.
+#
+# The test uses a composite location description, where some pieces
+# of that location description are undefined location description.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+    return 0
+}
+
+# Choose suitable integer registers for the test.
+
+set dwarf_regnum 0
+
+if { [is_aarch64_target] } {
+    set regname x0
+} elseif { [is_aarch32_target]
+	   || [istarget "s390*-*-*" ]
+	   || [istarget "powerpc*-*-*"]
+	   || [istarget "rs6000*-*-aix*"] } {
+    set regname r0
+} elseif { [is_x86_like_target] } {
+    set regname eax
+} elseif { [is_amd64_regs_target] } {
+    set regname rax
+} else {
+    verbose "Skipping ${gdb_test_file_name}."
+    return
+}
+
+standard_testfile var-access.c ${gdb_test_file_name}-dw.S
+
+# Make some DWARF for the test.
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+    global dwarf_regnum regname srcdir subdir srcfile
+    set buf_src [gdb_target_symbol buf]
+
+    set main_result [function_range main ${srcdir}/${subdir}/${srcfile}]
+    set main_start [lindex $main_result 0]
+    set main_length [lindex $main_result 1]
+
+    cu {} {
+	DW_TAG_compile_unit {
+	    {DW_AT_name var-access.c}
+	    {DW_AT_comp_dir /tmp}
+	} {
+	    declare_labels int_type_label char_type_label array_type_label
+
+	    # define char type
+	    char_type_label: DW_TAG_base_type {
+		{DW_AT_name "char"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 1 DW_FORM_sdata}
+	    }
+
+	    int_type_label: DW_TAG_base_type {
+		{DW_AT_name "int"}
+		{DW_AT_encoding @DW_ATE_signed}
+		{DW_AT_byte_size 4 DW_FORM_sdata}
+	    }
+
+	    array_type_label: DW_TAG_array_type {
+		{DW_AT_type :$char_type_label}
+	    } {
+		DW_TAG_subrange_type {
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_upper_bound 5 DW_FORM_udata}
+		}
+	    }
+
+	    DW_TAG_subprogram {
+		{DW_AT_name main}
+		{DW_AT_low_pc $main_start addr}
+		{DW_AT_high_pc $main_length data8}
+	    } {
+
+		# Array spread in different pieces of which some are
+		# undefined (1st and sixth bytes) and some are in a
+		# REGNAME register.
+		DW_TAG_variable {
+		    {DW_AT_name var_array}
+		    {DW_AT_type :$array_type_label}
+		    {DW_AT_location {
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+			DW_OP_regx $dwarf_regnum
+			DW_OP_piece 0x4
+			DW_OP_LLVM_undefined
+			DW_OP_piece 0x1
+		    } SPECIAL_expr}
+		}
+
+		DW_TAG_variable {
+		    {DW_AT_name var_int}
+		    {DW_AT_type :$int_type_label}
+		    {DW_AT_location {
+			DW_OP_LLVM_undefined
+		    } SPECIAL_expr}
+		}
+	    }
+	}
+    }
+}
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} \
+     [list $srcfile $asm_file] {nodebug}] } {
+    return -1
+}
+
+if ![runto_main] {
+    return -1
+}
+
+gdb_test_no_output "set var \$$regname = 0x04030201" "init reg"
+
+# Determine byte order.
+set endian [get_endianness]
+
+switch $endian {
+	little {set val "<optimized out>, 0x1, 0x2, 0x3, 0x4, <optimized out>"}
+	big {set val "<optimized out>, 0x4, 0x3, 0x2, 0x1, <optimized out>"}
+}
+
+gdb_test "print/x var_array" " = \\{${val}\\}" "var_array print"
+gdb_test "print/x var_int" " = <optimized out>" "var_int print"

gdb/testsuite/gdb.dwarf2/dw2-op-call.exp

@@ -40,4 +40,4 @@ if ![runto_main] {
     return -1
 }
 gdb_test "p arraynoloc" " = <optimized out>"
-gdb_test "p arraycallnoloc" {Asked for position 0 of stack, stack only has 0 elements on it\.}
+gdb_test "p arraycallnoloc" {dwarf expression stack underflow}

gdb/testsuite/gdb.dwarf2/dw2-param-error.exp

@@ -32,4 +32,4 @@ if ![runto f] {
 
 # FAIL was printing:
 # [...] in f (bad=)
-gdb_test "frame" { f \(bad=<error reading variable: Asked for position 0 of stack, stack only has 0 elements on it\.>, good=23\)}
+gdb_test "frame" { f \(bad=<error reading variable: dwarf expression stack underflow>, good=23\)}

gdb/testsuite/gdb.dwarf2/dw2-stack-boundary.exp

@@ -64,5 +64,5 @@ if { $readnow_p } {
 }
 gdb_assert {$w1 && $w2}
 
-gdb_test "p underflow" {Asked for position 0 of stack, stack only has 0 elements on it\.}
+gdb_test "p underflow" {dwarf expression stack underflow}
 gdb_test "p overflow" " = 2"

gdb/testsuite/lib/dwarf.exp

@@ -1221,6 +1221,20 @@ namespace eval Dwarf {
 		    _op .sleb128 [lindex $line 1]
 		}
 
+		DW_OP_LLVM_offset_constu {
+		    _op .uleb128 [lindex $line 1]
+		}
+
+		DW_OP_LLVM_extend {
+		    _op .uleb128 [lindex $line 1]
+		    _op .uleb128 [lindex $line 2]
+		}
+
+		DW_OP_LLVM_select_bit_piece {
+		    _op .uleb128 [lindex $line 1]
+		    _op .uleb128 [lindex $line 2]
+		}
+
 		default {
 		    if {[llength $line] > 1} {
 			error "Unimplemented: operands in location for $opcode"

gdb/valops.c

@@ -1040,20 +1040,31 @@ read_value_memory (struct value *val, LONGEST bit_offset,
   ULONGEST xfered_total = 0;
   struct gdbarch *arch = get_value_arch (val);
   int unit_size = gdbarch_addressable_memory_unit_size (arch);
+  bool big_endian = type_byte_order (value_type (val)) == BFD_ENDIAN_BIG;
   enum target_object object;
+  size_t extended_length
+    = length + (bit_offset + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
+  gdb_byte *buffer_ptr = buffer;
+  gdb::byte_vector temp_buffer;
+
+  if (bit_offset)
+    {
+      temp_buffer.resize (extended_length);
+      buffer_ptr = temp_buffer.data ();
+    }
 
   object = stack ? TARGET_OBJECT_STACK_MEMORY : TARGET_OBJECT_MEMORY;
 
-  while (xfered_total < length)
+  while (xfered_total < extended_length)
     {
       enum target_xfer_status status;
       ULONGEST xfered_partial;
 
       status = target_xfer_partial (current_inferior ()->top_target (),
 				    object, NULL,
-				    buffer + xfered_total * unit_size, NULL,
+				    buffer_ptr + xfered_total * unit_size, NULL,
 				    memaddr + xfered_total,
-				    length - xfered_total,
+				    extended_length - xfered_total,
 				    &xfered_partial);
 
       if (status == TARGET_XFER_OK)
@@ -1070,6 +1081,10 @@ read_value_memory (struct value *val, LONGEST bit_offset,
       xfered_total += xfered_partial;
       QUIT;
     }
+
+  if (bit_offset)
+    copy_bitwise (buffer, 0, temp_buffer.data (),
+		  bit_offset, length * HOST_CHAR_BIT, big_endian);
 }
 
 /* Store the contents of FROMVAL into the location of TOVAL.
@@ -1141,7 +1156,7 @@ value_assign (struct value *toval, struct value *fromval)
 	const gdb_byte *dest_buffer;
 	CORE_ADDR changed_addr;
 	int changed_len;
-	gdb_byte buffer[sizeof (LONGEST)];
+	gdb::byte_vector buffer;
 
 	if (value_bitsize (toval))
 	  {
@@ -1167,10 +1182,26 @@ value_assign (struct value *toval, struct value *fromval)
 		       "don't fit in a %d bit word."),
 		     (int) sizeof (LONGEST) * HOST_CHAR_BIT);
 
-	    read_memory (changed_addr, buffer, changed_len);
-	    modify_field (type, buffer, value_as_long (fromval),
+	    buffer.resize (changed_len);
+
+	    read_memory (changed_addr, buffer.data (), changed_len);
+	    modify_field (type, buffer.data (), value_as_long (fromval),
 			  value_bitpos (toval), value_bitsize (toval));
-	    dest_buffer = buffer;
+	    dest_buffer = buffer.data ();
+	  }
+	else if (value_bitpos (toval))
+	  {
+	    int bitpos = value_bitpos (toval);
+	    bool big_endian = type_byte_order (type) == BFD_ENDIAN_BIG;
+	    changed_addr = value_address (toval);
+	    changed_len = TYPE_LENGTH (type)
+			  + (bitpos + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
+	    buffer.resize (changed_len);
+	    read_memory (changed_addr, buffer.data (), changed_len);
+	    copy_bitwise (buffer.data (), bitpos,
+			  value_contents (fromval).data (), 0,
+			  TYPE_LENGTH (type) * HOST_CHAR_BIT, big_endian);
+	    dest_buffer = buffer.data();
 	  }
 	else
 	  {
@@ -1186,7 +1217,6 @@ value_assign (struct value *toval, struct value *fromval)
     case lval_register:
       {
 	struct frame_info *frame;
-	struct gdbarch *gdbarch;
 	int value_reg;
 
 	/* Figure out which frame this register value is in.  The value
@@ -1204,29 +1234,41 @@ value_assign (struct value *toval, struct value *fromval)
 	if (!frame)
 	  error (_("Value being assigned to is no longer active."));
 
-	gdbarch = get_frame_arch (frame);
+	gdbarch *arch = get_frame_arch (frame);
+	LONGEST bitpos = value_bitpos (toval);
+	LONGEST bitsize = value_bitsize (toval);
+	LONGEST offset = value_offset (toval);
 
-	if (value_bitsize (toval))
+	if (bitpos || bitsize)
 	  {
-	    struct value *parent = value_parent (toval);
-	    LONGEST offset = value_offset (parent) + value_offset (toval);
-	    size_t changed_len;
-	    gdb_byte buffer[sizeof (LONGEST)];
+	    int changed_len;
+	    bool big_endian = type_byte_order (type) == BFD_ENDIAN_BIG;
+
+	    if (bitsize)
+	      {
+		offset += value_offset (value_parent (toval));
+
+		changed_len = (bitpos + bitsize + HOST_CHAR_BIT - 1)
+			      / HOST_CHAR_BIT;
+
+		if (changed_len > (int) sizeof (LONGEST))
+		  error (_("Can't handle bitfields which "
+			   "don't fit in a %d bit word."),
+			   (int) sizeof (LONGEST) * HOST_CHAR_BIT);
+	      }
+	    else
+	      {
+		changed_len = TYPE_LENGTH (type)
+			      + (bitpos + HOST_CHAR_BIT - 1) / HOST_CHAR_BIT;
+
+		bitsize = TYPE_LENGTH (type) * HOST_CHAR_BIT;
+	      }
+
+	    gdb::byte_vector buffer (changed_len);
 	    int optim, unavail;
 
-	    changed_len = (value_bitpos (toval)
-			   + value_bitsize (toval)
-			   + HOST_CHAR_BIT - 1)
-			  / HOST_CHAR_BIT;
-
-	    if (changed_len > sizeof (LONGEST))
-	      error (_("Can't handle bitfields which "
-		       "don't fit in a %d bit word."),
-		     (int) sizeof (LONGEST) * HOST_CHAR_BIT);
-
 	    if (!get_frame_register_bytes (frame, value_reg, offset,
-					   {buffer, changed_len},
-					   &optim, &unavail))
+					   buffer, &optim, &unavail))
 	      {
 		if (optim)
 		  throw_error (OPTIMIZED_OUT_ERROR,
@@ -1236,23 +1278,21 @@ value_assign (struct value *toval, struct value *fromval)
 			       _("value is not available"));
 	      }
 
-	    modify_field (type, buffer, value_as_long (fromval),
-			  value_bitpos (toval), value_bitsize (toval));
+	    copy_bitwise (buffer.data (), bitpos,
+			  value_contents (fromval).data (),
+			  0, bitsize, big_endian);
 
-	    put_frame_register_bytes (frame, value_reg, offset,
-				      {buffer, changed_len});
+	    put_frame_register_bytes (frame, value_reg, offset, buffer);
 	  }
 	else
 	  {
-	    if (gdbarch_convert_register_p (gdbarch, VALUE_REGNUM (toval),
-					    type))
+	    if (gdbarch_convert_register_p (arch, VALUE_REGNUM (toval), type))
 	      {
 		/* If TOVAL is a special machine register requiring
 		   conversion of program values to a special raw
 		   format.  */
-		gdbarch_value_to_register (gdbarch, frame,
-					   VALUE_REGNUM (toval), type,
-					   value_contents (fromval).data ());
+		gdbarch_value_to_register (arch, frame, VALUE_REGNUM (toval),
+					   type, value_contents (fromval).data ());
 	      }
 	    else
 	      {
@@ -1260,8 +1300,7 @@ value_assign (struct value *toval, struct value *fromval)
 		  = gdb::make_array_view (value_contents (fromval).data (),
 					  TYPE_LENGTH (type));
 		put_frame_register_bytes (frame, value_reg,
-					  value_offset (toval),
-					  contents);
+					  offset, contents);
 	      }
 	  }
 
@@ -1363,21 +1402,22 @@ value_assign (struct value *toval, struct value *fromval)
 struct value *
 value_repeat (struct value *arg1, int count)
 {
-  struct value *val;
-
   if (VALUE_LVAL (arg1) != lval_memory)
     error (_("Only values in memory can be extended with '@'."));
   if (count < 1)
     error (_("Invalid number %d of repetitions."), count);
 
-  val = allocate_repeat_value (value_enclosing_type (arg1), count);
+  value *val
+    = allocate_repeat_value (value_enclosing_type (arg1), count);
 
   VALUE_LVAL (val) = lval_memory;
   set_value_address (val, value_address (arg1));
+  set_value_bitpos (val, value_bitpos (arg1));
+  type *enclosing_type = value_enclosing_type (val);
 
-  read_value_memory (val, 0, value_stack (val), value_address (val),
-		     value_contents_all_raw (val).data (),
-		     type_length_units (value_enclosing_type (val)));
+  read_value_memory (val, value_bitpos (val), value_stack (val),
+		     value_address (val), value_contents_all_raw (val).data (),
+		     type_length_units (enclosing_type));
 
   return val;
 }
@@ -1726,7 +1766,7 @@ value_array (int lowbound, int highbound, struct value **elemvec)
     {
       val = allocate_value (arraytype);
       for (idx = 0; idx < nelem; idx++)
-	value_contents_copy (val, idx * typelength, elemvec[idx], 0,
+	value_contents_copy (val, idx * typelength, elemvec[idx], 0, 0,
 			     typelength);
       return val;
     }
@@ -1736,7 +1776,8 @@ value_array (int lowbound, int highbound, struct value **elemvec)
 
   val = allocate_value (arraytype);
   for (idx = 0; idx < nelem; idx++)
-    value_contents_copy (val, idx * typelength, elemvec[idx], 0, typelength);
+    value_contents_copy (val, idx * typelength, elemvec[idx], 0, 0,
+			 typelength);
   return val;
 }
 
@@ -4005,7 +4046,7 @@ value_slice (struct value *array, int lowbound, int length)
     else
       {
 	slice = allocate_value (slice_type);
-	value_contents_copy (slice, 0, array, offset,
+	value_contents_copy (slice, 0, array, offset, 0,
 			     type_length_units (slice_type));
       }
 

gdb/value.c

@@ -1322,9 +1322,10 @@ value_ranges_copy_adjusted (struct value *dst, int dst_bit_offset,
 
 static void
 value_contents_copy_raw (struct value *dst, LONGEST dst_offset,
-			 struct value *src, LONGEST src_offset, LONGEST length)
+			 struct value *src, LONGEST src_offset,
+			 LONGEST src_bit_offset, LONGEST length)
 {
-  LONGEST src_bit_offset, dst_bit_offset, bit_length;
+  LONGEST src_total_bit_offset, dst_total_bit_offset, bit_length;
   struct gdbarch *arch = get_value_arch (src);
   int unit_size = gdbarch_addressable_memory_unit_size (arch);
 
@@ -1343,17 +1344,31 @@ value_contents_copy_raw (struct value *dst, LONGEST dst_offset,
 					     TARGET_CHAR_BIT * length));
 
   /* Copy the data.  */
-  memcpy (value_contents_all_raw (dst).data () + dst_offset * unit_size,
-	  value_contents_all_raw (src).data () + src_offset * unit_size,
-	  length * unit_size);
-
-  /* Copy the meta-data, adjusted.  */
-  src_bit_offset = src_offset * unit_size * HOST_CHAR_BIT;
-  dst_bit_offset = dst_offset * unit_size * HOST_CHAR_BIT;
   bit_length = length * unit_size * HOST_CHAR_BIT;
 
-  value_ranges_copy_adjusted (dst, dst_bit_offset,
-			      src, src_bit_offset,
+  if (src_bit_offset)
+    {
+      bool big_endian = type_byte_order (value_type (dst)) == BFD_ENDIAN_BIG;
+
+      copy_bitwise (value_contents_all_raw (dst).data ()
+		      + dst_offset * unit_size, 0,
+		    value_contents_all_raw (src).data ()
+		      + src_offset * unit_size,
+		    src_bit_offset, bit_length, big_endian);
+    }
+  else
+    memcpy (value_contents_all_raw (dst).data () + dst_offset * unit_size,
+	    value_contents_all_raw (src).data () + src_offset * unit_size,
+	    length * unit_size);
+
+  /* Copy the meta-data, adjusted.  */
+  src_total_bit_offset = src_offset * unit_size * HOST_CHAR_BIT
+			 + src_bit_offset;
+  dst_total_bit_offset = dst_offset * unit_size * HOST_CHAR_BIT;
+
+
+  value_ranges_copy_adjusted (dst, dst_total_bit_offset,
+			      src, src_total_bit_offset,
 			      bit_length);
 }
 
@@ -1369,12 +1384,14 @@ value_contents_copy_raw (struct value *dst, LONGEST dst_offset,
 
 void
 value_contents_copy (struct value *dst, LONGEST dst_offset,
-		     struct value *src, LONGEST src_offset, LONGEST length)
+		     struct value *src, LONGEST src_offset,
+		     LONGEST src_bit_offset, LONGEST length)
 {
   if (src->lazy)
     value_fetch_lazy (src);
 
-  value_contents_copy_raw (dst, dst_offset, src, src_offset, length);
+  value_contents_copy_raw (dst, dst_offset, src, src_offset,
+			   src_bit_offset, length);
 }
 
 int
@@ -3089,7 +3106,7 @@ value_primitive_field (struct value *arg1, LONGEST offset,
       else
 	{
 	  v = allocate_value (value_enclosing_type (arg1));
-	  value_contents_copy_raw (v, 0, arg1, 0,
+	  value_contents_copy_raw (v, 0, arg1, 0, 0,
 				   TYPE_LENGTH (value_enclosing_type (arg1)));
 	}
       v->type = type;
@@ -3124,7 +3141,7 @@ value_primitive_field (struct value *arg1, LONGEST offset,
 	  v = allocate_value (type);
 	  value_contents_copy_raw (v, value_embedded_offset (v),
 				   arg1, value_embedded_offset (arg1) + offset,
-				   type_length_units (type));
+				   0, type_length_units (type));
 	}
       v->offset = (value_offset (arg1) + offset
 		   + value_embedded_offset (arg1));
@@ -3476,7 +3493,7 @@ pack_long (gdb_byte *buf, struct type *type, LONGEST num)
 
 /* Pack NUM into BUF using a target format of TYPE.  */
 
-static void
+void
 pack_unsigned_long (gdb_byte *buf, struct type *type, ULONGEST num)
 {
   LONGEST len;
@@ -3731,7 +3748,7 @@ value_from_component (struct value *whole, struct type *type, LONGEST offset)
       v = allocate_value (type);
       value_contents_copy (v, value_embedded_offset (v),
 			   whole, value_embedded_offset (whole) + offset,
-			   type_length_units (type));
+			   0, type_length_units (type));
     }
   v->offset = value_offset (whole) + offset + value_embedded_offset (whole);
   set_value_component_location (v, whole);
@@ -3913,9 +3930,9 @@ value_fetch_lazy_memory (struct value *val)
   struct type *type = check_typedef (value_enclosing_type (val));
 
   if (TYPE_LENGTH (type))
-      read_value_memory (val, 0, value_stack (val),
-			 addr, value_contents_all_raw (val).data (),
-			 type_length_units (type));
+    read_value_memory (val, value_bitpos (val), value_stack (val),
+		       addr, value_contents_all_raw (val).data (),
+		       type_length_units (type));
 }
 
 /* Helper for value_fetch_lazy when the value is in a register.  */
@@ -3928,10 +3945,6 @@ value_fetch_lazy_register (struct value *val)
   struct type *type = check_typedef (value_type (val));
   struct value *new_val = val, *mark = value_mark ();
 
-  /* Offsets are not supported here; lazy register values must
-     refer to the entire register.  */
-  gdb_assert (value_offset (val) == 0);
-
   while (VALUE_LVAL (new_val) == lval_register && value_lazy (new_val))
     {
       struct frame_id next_frame_id = VALUE_NEXT_FRAME_ID (new_val);
@@ -3974,6 +3987,11 @@ value_fetch_lazy_register (struct value *val)
 			_("infinite loop while fetching a register"));
     }
 
+  /* Check if NEW_VALUE is big enough to cover
+     the expected VAL type with an offset.  */
+  gdb_assert ((TYPE_LENGTH (type) + value_offset (val))
+	      <= TYPE_LENGTH (value_type (new_val)));
+
   /* If it's still lazy (for instance, a saved register on the
      stack), fetch it.  */
   if (value_lazy (new_val))
@@ -3982,9 +4000,9 @@ value_fetch_lazy_register (struct value *val)
   /* Copy the contents and the unavailability/optimized-out
      meta-data from NEW_VAL to VAL.  */
   set_value_lazy (val, 0);
-  value_contents_copy (val, value_embedded_offset (val),
-		       new_val, value_embedded_offset (new_val),
-		       type_length_units (type));
+  value_contents_copy (val, value_embedded_offset (val), new_val,
+		       value_embedded_offset (new_val) + value_offset (val),
+		       value_bitpos (val), type_length_units (type));
 
   if (frame_debug)
     {

gdb/value.h

@@ -678,6 +678,8 @@ extern struct value *value_field_bitfield (struct type *type, int fieldno,
 					   const struct value *val);
 
 extern void pack_long (gdb_byte *buf, struct type *type, LONGEST num);
+extern void pack_unsigned_long (gdb_byte *buf, struct type *type,
+				ULONGEST num);
 
 extern struct value *value_from_longest (struct type *type, LONGEST num);
 extern struct value *value_from_ulongest (struct type *type, ULONGEST num);
@@ -738,7 +740,7 @@ extern struct value *allocate_value (struct type *type);
 extern struct value *allocate_value_lazy (struct type *type);
 extern void value_contents_copy (struct value *dst, LONGEST dst_offset,
 				 struct value *src, LONGEST src_offset,
-				 LONGEST length);
+				 LONGEST src_bit_offset, LONGEST length);
 
 extern struct value *allocate_repeat_value (struct type *type, int count);
 

gdbsupport/common-utils.h

@@ -206,4 +206,22 @@ extern int hex2bin (const char *hex, gdb_byte *bin, int count);
 /* Like the above, but return a gdb::byte_vector.  */
 gdb::byte_vector hex2bin (const char *hex);
 
+#if __cplusplus >= 201402L
+#include <memory>
+
+using std::make_unique;
+#else
+namespace gdb {
+
+/* Stolen from libstdc++ and adjusted, so probably fine license-wise.  */
+template<typename _Tp, typename ... _Args>
+std::unique_ptr<_Tp>
+make_unique (_Args &&... __args)
+{
+  return std::unique_ptr<_Tp> (new _Tp (std::forward<_Args>(__args)...));
+}
+
+}
+#endif /* __cplusplus >= 201402L */
+
 #endif /* COMMON_COMMON_UTILS_H */

include/dwarf2.def

@@ -704,6 +704,16 @@ DW_OP (DW_OP_PGI_omp_thread_num, 0xf8)
    to 0 except explicitly documented for one action.  Please refer AArch64 DWARF
    ABI documentation for details.  */
 DW_OP (DW_OP_AARCH64_operation, 0xea)
+/* LLVM extensions for heterogeneous targets */
+DW_OP_DUP (DW_OP_LLVM_offset, 0xe3)
+DW_OP_DUP (DW_OP_LLVM_offset_constu, 0xe4)
+DW_OP_DUP (DW_OP_LLVM_bit_offset, 0xe5)
+DW_OP (DW_OP_LLVM_undefined, 0xe7)
+DW_OP_DUP (DW_OP_LLVM_piece_end, 0xea)
+DW_OP (DW_OP_LLVM_extend, 0xeb)
+DW_OP (DW_OP_LLVM_select_bit_piece, 0xec)
+DW_OP (DW_OP_LLVM_bit_overlay, 0xed)
+DW_OP (DW_OP_LLVM_overlay, 0xee)
 DW_END_OP
 
 DW_FIRST_ATE (DW_ATE_void, 0x0)