1/* Function return value location for Linux/PPC64 ABI.
2   Copyright (C) 2005-2010, 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 ppc64_
37#include "libebl_CPU.h"
38
39
40/* r3.  */
41static const Dwarf_Op loc_intreg[] =
42  {
43    { .atom = DW_OP_reg3 }
44  };
45#define nloc_intreg	1
46
47/* f1, or f1:f2, or f1:f4.  */
48static const Dwarf_Op loc_fpreg[] =
49  {
50    { .atom = DW_OP_regx, .number = 33 }, { .atom = DW_OP_piece, .number = 8 },
51    { .atom = DW_OP_regx, .number = 34 }, { .atom = DW_OP_piece, .number = 8 },
52    { .atom = DW_OP_regx, .number = 35 }, { .atom = DW_OP_piece, .number = 8 },
53    { .atom = DW_OP_regx, .number = 36 }, { .atom = DW_OP_piece, .number = 8 },
54  };
55#define nloc_fpreg	1
56#define nloc_fp2regs	4
57#define nloc_fp4regs	8
58
59/* vr2.  */
60static const Dwarf_Op loc_vmxreg[] =
61  {
62    { .atom = DW_OP_regx, .number = 1124 + 2 }
63  };
64#define nloc_vmxreg	1
65
66/* The return value is a structure and is actually stored in stack space
67   passed in a hidden argument by the caller.  But, the compiler
68   helpfully returns the address of that space in r3.  */
69static const Dwarf_Op loc_aggregate[] =
70  {
71    { .atom = DW_OP_breg3, .number = 0 }
72  };
73#define nloc_aggregate 1
74
75int
76ppc64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
77{
78  /* Start with the function's type, and get the DW_AT_type attribute,
79     which is the type of the return value.  */
80  Dwarf_Die die_mem, *typedie = &die_mem;
81  int tag = dwarf_peeled_die_type (functypedie, typedie);
82  if (tag <= 0)
83    return tag;
84
85  Dwarf_Word size;
86  switch (tag)
87    {
88    case -1:
89      return -1;
90
91    case DW_TAG_subrange_type:
92      if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
93	{
94	  Dwarf_Attribute attr_mem, *attr;
95	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
96	  typedie = dwarf_formref_die (attr, &die_mem);
97	  tag = DWARF_TAG_OR_RETURN (typedie);
98	}
99      /* Fall through.  */
100
101    case DW_TAG_base_type:
102    case DW_TAG_enumeration_type:
103    case DW_TAG_pointer_type:
104    case DW_TAG_ptr_to_member_type:
105      {
106	Dwarf_Attribute attr_mem;
107	if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
108						   &attr_mem), &size) != 0)
109	  {
110	    if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
111	      size = 8;
112	    else
113	      return -1;
114	}
115      }
116
117      if (tag == DW_TAG_base_type)
118	{
119	  Dwarf_Attribute attr_mem;
120	  Dwarf_Word encoding;
121	  if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
122						     &attr_mem),
123			       &encoding) != 0)
124	    return -1;
125
126	  if (encoding == DW_ATE_float || encoding == DW_ATE_complex_float)
127	    {
128	      *locp = loc_fpreg;
129	      if (size <= 8)
130		return nloc_fpreg;
131	      if (size <= 16)
132		return nloc_fp2regs;
133	      if (size <= 32)
134		return nloc_fp4regs;
135	    }
136	}
137      if (size <= 8)
138	{
139	intreg:
140	  *locp = loc_intreg;
141	  return nloc_intreg;
142	}
143
144      /* Else fall through.  */
145    case DW_TAG_structure_type:
146    case DW_TAG_class_type:
147    case DW_TAG_union_type:
148    aggregate:
149      *locp = loc_aggregate;
150      return nloc_aggregate;
151
152    case DW_TAG_array_type:
153      {
154	Dwarf_Attribute attr_mem;
155	bool is_vector;
156	if (dwarf_formflag (dwarf_attr_integrate (typedie, DW_AT_GNU_vector,
157						  &attr_mem), &is_vector) == 0
158	    && is_vector)
159	  {
160	    *locp = loc_vmxreg;
161	    return nloc_vmxreg;
162	  }
163      }
164      /* Fall through.  */
165
166    case DW_TAG_string_type:
167      if (dwarf_aggregate_size (typedie, &size) == 0 && size <= 8)
168	{
169	  if (tag == DW_TAG_array_type)
170	    {
171	      /* Check if it's a character array.  */
172	      Dwarf_Attribute attr_mem, *attr;
173	      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
174	      typedie = dwarf_formref_die (attr, &die_mem);
175	      tag = DWARF_TAG_OR_RETURN (typedie);
176	      if (tag != DW_TAG_base_type)
177		goto aggregate;
178	      if (dwarf_formudata (dwarf_attr_integrate (typedie,
179							 DW_AT_byte_size,
180							 &attr_mem),
181				   &size) != 0)
182		return -1;
183	      if (size != 1)
184		goto aggregate;
185	    }
186	  goto intreg;
187	}
188      goto aggregate;
189    }
190
191  /* XXX We don't have a good way to return specific errors from ebl calls.
192     This value means we do not understand the type, but it is well-formed
193     DWARF and might be valid.  */
194  return -2;
195}
196