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      1 /* Function return value location for Linux/TILE-Gx ABI.
      2    Copyright (C) 2012 Tilera Corporation
      3    Copyright (C) 2014 Red Hat, Inc.
      4    This file is part of elfutils.
      5 
      6    This file is free software; you can redistribute it and/or modify
      7    it under the terms of either
      8 
      9      * the GNU Lesser General Public License as published by the Free
     10        Software Foundation; either version 3 of the License, or (at
     11        your option) any later version
     12 
     13    or
     14 
     15      * the GNU General Public License as published by the Free
     16        Software Foundation; either version 2 of the License, or (at
     17        your option) any later version
     18 
     19    or both in parallel, as here.
     20 
     21    elfutils is distributed in the hope that it will be useful, but
     22    WITHOUT ANY WARRANTY; without even the implied warranty of
     23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     24    General Public License for more details.
     25 
     26    You should have received copies of the GNU General Public License and
     27    the GNU Lesser General Public License along with this program.  If
     28    not, see <http://www.gnu.org/licenses/>.  */
     29 
     30 
     31 #ifdef HAVE_CONFIG_H
     32 # include <config.h>
     33 #endif
     34 
     35 #include <assert.h>
     36 #include <dwarf.h>
     37 
     38 #define BACKEND tilegx_
     39 #include "libebl_CPU.h"
     40 
     41 
     42 /* r0.  */
     43 static const Dwarf_Op loc_intreg[] =
     44   {
     45     { .atom = DW_OP_reg0 }
     46   };
     47 #define nloc_intreg	1
     48 
     49 /* The return value is a structure and is actually stored in stack space
     50    passed in a hidden argument by the caller.  But, the compiler
     51    helpfully returns the address of that space in r0.  */
     52 static const Dwarf_Op loc_aggregate[] =
     53   {
     54     { .atom = DW_OP_breg0, .number = 0 }
     55   };
     56 #define nloc_aggregate 1
     57 
     58 int
     59 tilegx_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
     60 {
     61   /* Start with the function's type, and get the DW_AT_type attribute,
     62      which is the type of the return value.  */
     63   Dwarf_Die die_mem, *typedie = &die_mem;
     64   int tag = dwarf_peeled_die_type (functypedie, typedie);
     65   if (tag <= 0)
     66     return tag;
     67 
     68   Dwarf_Word size;
     69   switch (tag)
     70     {
     71     case -1:
     72       return -1;
     73 
     74     case DW_TAG_subrange_type:
     75       if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
     76 	{
     77 	  Dwarf_Attribute attr_mem, *attr;
     78 	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
     79 	  typedie = dwarf_formref_die (attr, &die_mem);
     80 	  tag = DWARF_TAG_OR_RETURN (typedie);
     81 	}
     82       /* Fall through.  */
     83 
     84     case DW_TAG_base_type:
     85     case DW_TAG_enumeration_type:
     86     case DW_TAG_pointer_type:
     87     case DW_TAG_ptr_to_member_type:
     88       {
     89 	Dwarf_Attribute attr_mem;
     90 	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
     91 						   &attr_mem), &size) != 0)
     92 	  {
     93 	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
     94 	      size = 8;
     95 	    else
     96 	      return -1;
     97 	  }
     98 	if (tag == DW_TAG_base_type)
     99 	  {
    100 	    Dwarf_Word encoding;
    101 	    if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
    102 						       &attr_mem),
    103 				 &encoding) != 0)
    104 	      return -1;
    105 	  }
    106       }
    107 
    108       /* Small enough structs are passed directly in registers R0 ... R7.  */
    109       if (size <= 8)
    110 	{
    111 	intreg:
    112 	  *locp = loc_intreg;
    113 	  return nloc_intreg;
    114 	}
    115 
    116       /* Else fall through.  */
    117     case DW_TAG_structure_type:
    118     case DW_TAG_class_type:
    119     case DW_TAG_union_type:
    120     aggregate:
    121       *locp = loc_aggregate;
    122       return nloc_aggregate;
    123 
    124     case DW_TAG_array_type:
    125     case DW_TAG_string_type:
    126       if (dwarf_aggregate_size (typedie, &size) == 0 && size <= 8)
    127 	{
    128 	  if (tag == DW_TAG_array_type)
    129 	    {
    130 	      Dwarf_Attribute attr_mem, *attr;
    131 	      /* Check if it's a character array.  */
    132 	      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
    133 	      typedie = dwarf_formref_die (attr, &die_mem);
    134 	      tag = DWARF_TAG_OR_RETURN (typedie);
    135 	      if (tag != DW_TAG_base_type)
    136 		goto aggregate;
    137 	      if (dwarf_formudata (dwarf_attr_integrate (typedie,
    138 							 DW_AT_byte_size,
    139 							 &attr_mem),
    140 				   &size) != 0)
    141 		return -1;
    142 	      if (size != 1)
    143 		goto aggregate;
    144 	    }
    145 	  goto intreg;
    146 	}
    147       goto aggregate;
    148     }
    149 
    150   /* XXX We don't have a good way to return specific errors from ebl calls.
    151      This value means we do not understand the type, but it is well-formed
    152      DWARF and might be valid.  */
    153   return -2;
    154 }
    155