1/* Function return value location for Alpha ELF ABI.
2   Copyright (C) 2005, 2007 Red Hat, Inc.
3   This file is part of Red Hat elfutils.
4
5   Red Hat elfutils is free software; you can redistribute it and/or modify
6   it under the terms of the GNU General Public License as published by the
7   Free Software Foundation; version 2 of the License.
8
9   Red Hat elfutils is distributed in the hope that it will be useful, but
10   WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   General Public License for more details.
13
14   You should have received a copy of the GNU General Public License along
15   with Red Hat elfutils; if not, write to the Free Software Foundation,
16   Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA.
17
18   Red Hat elfutils is an included package of the Open Invention Network.
19   An included package of the Open Invention Network is a package for which
20   Open Invention Network licensees cross-license their patents.  No patent
21   license is granted, either expressly or impliedly, by designation as an
22   included package.  Should you wish to participate in the Open Invention
23   Network licensing program, please visit www.openinventionnetwork.com
24   <http://www.openinventionnetwork.com>.  */
25
26#ifdef HAVE_CONFIG_H
27# include <config.h>
28#endif
29
30#include <assert.h>
31#include <dwarf.h>
32
33#define BACKEND alpha_
34#include "libebl_CPU.h"
35
36
37/* $0.  */
38static const Dwarf_Op loc_intreg[] =
39  {
40    { .atom = DW_OP_reg0 }
41  };
42#define nloc_intreg	1
43
44/* $f0, or pair $f0, $f1.  */
45static const Dwarf_Op loc_fpreg[] =
46  {
47    { .atom = DW_OP_regx, .number = 32 }, { .atom = DW_OP_piece, .number = 4 },
48    { .atom = DW_OP_regx, .number = 33 }, { .atom = DW_OP_piece, .number = 4 },
49  };
50#define nloc_fpreg	1
51#define nloc_fpregpair	4
52
53/* The return value is a structure and is actually stored in stack space
54   passed in a hidden argument by the caller.  But, the compiler
55   helpfully returns the address of that space in $0.  */
56static const Dwarf_Op loc_aggregate[] =
57  {
58    { .atom = DW_OP_breg0, .number = 0 }
59  };
60#define nloc_aggregate 1
61
62int
63alpha_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
64{
65  /* Start with the function's type, and get the DW_AT_type attribute,
66     which is the type of the return value.  */
67
68  Dwarf_Attribute attr_mem;
69  Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
70						&attr_mem);
71  if (attr == NULL)
72    /* The function has no return value, like a `void' function in C.  */
73    return 0;
74
75  Dwarf_Die die_mem;
76  Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
77  int tag = dwarf_tag (typedie);
78
79  /* Follow typedefs and qualifiers to get to the actual type.  */
80  while (tag == DW_TAG_typedef
81	 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
82	 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
83    {
84      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
85      typedie = dwarf_formref_die (attr, &die_mem);
86      tag = dwarf_tag (typedie);
87    }
88
89  switch (tag)
90    {
91    case -1:
92      return -1;
93
94    case DW_TAG_subrange_type:
95      if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
96	{
97	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
98	  typedie = dwarf_formref_die (attr, &die_mem);
99	  tag = dwarf_tag (typedie);
100	}
101      /* Fall through.  */
102
103    case DW_TAG_base_type:
104    case DW_TAG_enumeration_type:
105    case DW_TAG_pointer_type:
106    case DW_TAG_ptr_to_member_type:
107      {
108	Dwarf_Word size;
109	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
110						   &attr_mem), &size) != 0)
111	  {
112	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
113	      size = 8;
114	    else
115	      return -1;
116	  }
117	if (tag == DW_TAG_base_type)
118	  {
119	    Dwarf_Word encoding;
120	    if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
121						       &attr_mem),
122				 &encoding) != 0)
123	      return -1;
124
125	    *locp = loc_fpreg;
126	    if (encoding == DW_ATE_float)
127	      {
128		if (size <= 8)
129		  return nloc_fpreg;
130		goto aggregate;
131	      }
132	    if (encoding == DW_ATE_complex_float)
133	      {
134		if (size <= 8 * 2)
135		  return nloc_fpregpair;
136		goto aggregate;
137	      }
138	  }
139	if (size <= 8)
140	  {
141	    *locp = loc_intreg;
142	    return nloc_intreg;
143	  }
144      }
145
146      /* Else fall through.  */
147
148    case DW_TAG_structure_type:
149    case DW_TAG_class_type:
150    case DW_TAG_union_type:
151    case DW_TAG_string_type:
152    case DW_TAG_array_type:
153    aggregate:
154      *locp = loc_aggregate;
155      return nloc_aggregate;
156    }
157
158  /* XXX We don't have a good way to return specific errors from ebl calls.
159     This value means we do not understand the type, but it is well-formed
160     DWARF and might be valid.  */
161  return -2;
162}
163