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      1 /* Function return value location for Alpha ELF ABI.
      2    Copyright (C) 2005, 2007, 2014 Red Hat, Inc.
      3    This file is part of elfutils.
      4 
      5    This file is free software; you can redistribute it and/or modify
      6    it under the terms of either
      7 
      8      * the GNU Lesser General Public License as published by the Free
      9        Software Foundation; either version 3 of the License, or (at
     10        your option) any later version
     11 
     12    or
     13 
     14      * the GNU General Public License as published by the Free
     15        Software Foundation; either version 2 of the License, or (at
     16        your option) any later version
     17 
     18    or both in parallel, as here.
     19 
     20    elfutils is distributed in the hope that it will be useful, but
     21    WITHOUT ANY WARRANTY; without even the implied warranty of
     22    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     23    General Public License for more details.
     24 
     25    You should have received copies of the GNU General Public License and
     26    the GNU Lesser General Public License along with this program.  If
     27    not, see <http://www.gnu.org/licenses/>.  */
     28 
     29 #ifdef HAVE_CONFIG_H
     30 # include <config.h>
     31 #endif
     32 
     33 #include <assert.h>
     34 #include <dwarf.h>
     35 
     36 #define BACKEND alpha_
     37 #include "libebl_CPU.h"
     38 
     39 
     40 /* $0.  */
     41 static const Dwarf_Op loc_intreg[] =
     42   {
     43     { .atom = DW_OP_reg0 }
     44   };
     45 #define nloc_intreg	1
     46 
     47 /* $f0, or pair $f0, $f1.  */
     48 static const Dwarf_Op loc_fpreg[] =
     49   {
     50     { .atom = DW_OP_regx, .number = 32 }, { .atom = DW_OP_piece, .number = 4 },
     51     { .atom = DW_OP_regx, .number = 33 }, { .atom = DW_OP_piece, .number = 4 },
     52   };
     53 #define nloc_fpreg	1
     54 #define nloc_fpregpair	4
     55 
     56 /* The return value is a structure and is actually stored in stack space
     57    passed in a hidden argument by the caller.  But, the compiler
     58    helpfully returns the address of that space in $0.  */
     59 static const Dwarf_Op loc_aggregate[] =
     60   {
     61     { .atom = DW_OP_breg0, .number = 0 }
     62   };
     63 #define nloc_aggregate 1
     64 
     65 int
     66 alpha_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
     67 {
     68   /* Start with the function's type, and get the DW_AT_type attribute,
     69      which is the type of the return value.  */
     70   Dwarf_Die die_mem, *typedie = &die_mem;
     71   int tag = dwarf_peeled_die_type (functypedie, typedie);
     72   if (tag <= 0)
     73     return tag;
     74 
     75   switch (tag)
     76     {
     77     case -1:
     78       return -1;
     79 
     80     case DW_TAG_subrange_type:
     81       if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
     82 	{
     83 	  Dwarf_Attribute attr_mem, *attr;
     84 	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
     85 	  typedie = dwarf_formref_die (attr, &die_mem);
     86 	  tag = DWARF_TAG_OR_RETURN (typedie);
     87 	}
     88       /* Fall through.  */
     89 
     90     case DW_TAG_base_type:
     91     case DW_TAG_enumeration_type:
     92     case DW_TAG_pointer_type:
     93     case DW_TAG_ptr_to_member_type:
     94       {
     95 	Dwarf_Attribute attr_mem;
     96 	Dwarf_Word size;
     97 	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
     98 						   &attr_mem), &size) != 0)
     99 	  {
    100 	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
    101 	      size = 8;
    102 	    else
    103 	      return -1;
    104 	  }
    105 	if (tag == DW_TAG_base_type)
    106 	  {
    107 	    Dwarf_Word encoding;
    108 	    if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
    109 						       &attr_mem),
    110 				 &encoding) != 0)
    111 	      return -1;
    112 
    113 	    *locp = loc_fpreg;
    114 	    if (encoding == DW_ATE_float)
    115 	      {
    116 		if (size <= 8)
    117 		  return nloc_fpreg;
    118 		goto aggregate;
    119 	      }
    120 	    if (encoding == DW_ATE_complex_float)
    121 	      {
    122 		if (size <= 8 * 2)
    123 		  return nloc_fpregpair;
    124 		goto aggregate;
    125 	      }
    126 	  }
    127 	if (size <= 8)
    128 	  {
    129 	    *locp = loc_intreg;
    130 	    return nloc_intreg;
    131 	  }
    132       }
    133 
    134       /* Else fall through.  */
    135 
    136     case DW_TAG_structure_type:
    137     case DW_TAG_class_type:
    138     case DW_TAG_union_type:
    139     case DW_TAG_string_type:
    140     case DW_TAG_array_type:
    141     aggregate:
    142       *locp = loc_aggregate;
    143       return nloc_aggregate;
    144     }
    145 
    146   /* XXX We don't have a good way to return specific errors from ebl calls.
    147      This value means we do not understand the type, but it is well-formed
    148      DWARF and might be valid.  */
    149   return -2;
    150 }
    151