1/* Function return value location for S/390 ABI.
2   Copyright (C) 2006, 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 s390_
34#include "libebl_CPU.h"
35
36
37/* %r2, or pair %r2, %r3.  */
38static const Dwarf_Op loc_intreg[] =
39  {
40    { .atom = DW_OP_reg2 }, { .atom = DW_OP_piece, .number = 4 },
41    { .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
42  };
43#define nloc_intreg	1
44#define nloc_intregpair	4
45
46/* %f0.  */
47static const Dwarf_Op loc_fpreg[] =
48  {
49    { .atom = DW_OP_reg16 },
50  };
51#define nloc_fpreg	1
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 %r2.  */
56static const Dwarf_Op loc_aggregate[] =
57  {
58    { .atom = DW_OP_breg2, .number = 0 }
59  };
60#define nloc_aggregate 1
61
62
63int
64s390_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
65{
66  /* Start with the function's type, and get the DW_AT_type attribute,
67     which is the type of the return value.  */
68
69  Dwarf_Attribute attr_mem;
70  Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
71						&attr_mem);
72  if (attr == NULL)
73    /* The function has no return value, like a `void' function in C.  */
74    return 0;
75
76  Dwarf_Die die_mem;
77  Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
78  int tag = dwarf_tag (typedie);
79
80  /* Follow typedefs and qualifiers to get to the actual type.  */
81  while (tag == DW_TAG_typedef
82	 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
83	 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
84    {
85      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
86      typedie = dwarf_formref_die (attr, &die_mem);
87      tag = dwarf_tag (typedie);
88    }
89
90  Dwarf_Word size;
91  switch (tag)
92    {
93    case -1:
94      return -1;
95
96    case DW_TAG_subrange_type:
97      if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
98	{
99	  attr = dwarf_attr (typedie, DW_AT_type, &attr_mem);
100	  typedie = dwarf_formref_die (attr, &die_mem);
101	  tag = dwarf_tag (typedie);
102	}
103      /* Fall through.  */
104
105    case DW_TAG_base_type:
106    case DW_TAG_enumeration_type:
107    case DW_TAG_pointer_type:
108    case DW_TAG_ptr_to_member_type:
109      {
110	Dwarf_Die cudie;
111	uint8_t asize;
112	if (dwarf_diecu (typedie, &cudie, &asize, NULL) == NULL)
113	  return -1;
114
115	if (dwarf_formudata (dwarf_attr (typedie, DW_AT_byte_size,
116					 &attr_mem), &size) != 0)
117	  {
118	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
119	      size = asize;
120	    else
121	      return -1;
122	  }
123	if (tag == DW_TAG_base_type)
124	  {
125	    Dwarf_Word encoding;
126	    if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
127						       &attr_mem),
128				 &encoding) != 0)
129	      return -1;
130	    if (encoding == DW_ATE_float && size <= 8)
131	      {
132		*locp = loc_fpreg;
133		return nloc_fpreg;
134	      }
135	  }
136	if (size <= 8)
137	  {
138	    *locp = loc_intreg;
139	    return size <= asize ? nloc_intreg : nloc_intregpair;
140	  }
141      }
142      /* Fall through.  */
143
144    case DW_TAG_structure_type:
145    case DW_TAG_class_type:
146    case DW_TAG_union_type:
147    case DW_TAG_array_type:
148      *locp = loc_aggregate;
149      return nloc_aggregate;
150    }
151
152  /* XXX We don't have a good way to return specific errors from ebl calls.
153     This value means we do not understand the type, but it is well-formed
154     DWARF and might be valid.  */
155  return -2;
156}
157