1/* Function return value location for Linux/x86-64 ABI.
2   Copyright (C) 2005-2010 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 x86_64_
34#include "libebl_CPU.h"
35
36
37/* %rax, or pair %rax, %rdx.  */
38static const Dwarf_Op loc_intreg[] =
39  {
40    { .atom = DW_OP_reg0 }, { .atom = DW_OP_piece, .number = 8 },
41    { .atom = DW_OP_reg1 }, { .atom = DW_OP_piece, .number = 8 },
42  };
43#define nloc_intreg	1
44#define nloc_intregpair	4
45
46/* %st(0), or pair %st(0), %st(1).  */
47static const Dwarf_Op loc_x87reg[] =
48  {
49    { .atom = DW_OP_regx, .number = 33 },
50    { .atom = DW_OP_piece, .number = 10 },
51    { .atom = DW_OP_regx, .number = 34 },
52    { .atom = DW_OP_piece, .number = 10 },
53  };
54#define nloc_x87reg	1
55#define nloc_x87regpair	4
56
57/* %xmm0, or pair %xmm0, %xmm1.  */
58static const Dwarf_Op loc_ssereg[] =
59  {
60    { .atom = DW_OP_reg17 }, { .atom = DW_OP_piece, .number = 16 },
61    { .atom = DW_OP_reg18 }, { .atom = DW_OP_piece, .number = 16 },
62  };
63#define nloc_ssereg	1
64#define nloc_sseregpair	4
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 %rax.  */
69static const Dwarf_Op loc_aggregate[] =
70  {
71    { .atom = DW_OP_breg0, .number = 0 }
72  };
73#define nloc_aggregate 1
74
75
76int
77x86_64_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
78{
79  /* Start with the function's type, and get the DW_AT_type attribute,
80     which is the type of the return value.  */
81
82  Dwarf_Attribute attr_mem;
83  Dwarf_Attribute *attr = dwarf_attr_integrate (functypedie, DW_AT_type,
84						&attr_mem);
85  if (attr == NULL)
86    /* The function has no return value, like a `void' function in C.  */
87    return 0;
88
89  Dwarf_Die die_mem;
90  Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
91  int tag = dwarf_tag (typedie);
92
93  /* Follow typedefs and qualifiers to get to the actual type.  */
94  while (tag == DW_TAG_typedef
95	 || tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
96	 || tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
97    {
98      attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
99      typedie = dwarf_formref_die (attr, &die_mem);
100      tag = dwarf_tag (typedie);
101    }
102
103  Dwarf_Word size;
104  switch (tag)
105    {
106    case -1:
107      return -1;
108
109    case DW_TAG_subrange_type:
110      if (! dwarf_hasattr_integrate (typedie, DW_AT_byte_size))
111	{
112	  attr = dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem);
113	  typedie = dwarf_formref_die (attr, &die_mem);
114	  tag = dwarf_tag (typedie);
115	}
116      /* Fall through.  */
117
118    case DW_TAG_base_type:
119    case DW_TAG_enumeration_type:
120    case DW_TAG_pointer_type:
121    case DW_TAG_ptr_to_member_type:
122      if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_byte_size,
123						 &attr_mem), &size) != 0)
124	{
125	  if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
126	    size = 8;
127	  else
128	    return -1;
129	}
130      if (tag == DW_TAG_base_type)
131	{
132	  Dwarf_Word encoding;
133	  if (dwarf_formudata (dwarf_attr_integrate (typedie, DW_AT_encoding,
134						     &attr_mem),
135			       &encoding) != 0)
136	    return -1;
137
138	  switch (encoding)
139	    {
140	    case DW_ATE_complex_float:
141	      switch (size)
142		{
143		case 4 * 2:	/* complex float */
144		case 8 * 2:	/* complex double */
145		  *locp = loc_ssereg;
146		  return nloc_sseregpair;
147		case 16 * 2:	/* complex long double */
148		  *locp = loc_x87reg;
149		  return nloc_x87regpair;
150		}
151	      return -2;
152
153	    case DW_ATE_float:
154	      switch (size)
155		{
156		case 4:	/* float */
157		case 8:	/* double */
158		  *locp = loc_ssereg;
159		  return nloc_ssereg;
160		case 16:	/* long double */
161		  /* XXX distinguish __float128, which is sseregpair?? */
162		  *locp = loc_x87reg;
163		  return nloc_x87reg;
164		}
165	      return -2;
166	    }
167	}
168
169    intreg:
170      *locp = loc_intreg;
171      if (size <= 8)
172	return nloc_intreg;
173      if (size <= 16)
174	return nloc_intregpair;
175
176    large:
177      *locp = loc_aggregate;
178      return nloc_aggregate;
179
180    case DW_TAG_structure_type:
181    case DW_TAG_class_type:
182    case DW_TAG_union_type:
183    case DW_TAG_array_type:
184      if (dwarf_aggregate_size (typedie, &size) != 0)
185	goto large;
186      if (size > 16)
187	goto large;
188
189      /* XXX
190	 Must examine the fields in picayune ways to determine the
191	 actual answer.  This will be right for small C structs
192	 containing integer types and similarly simple cases.
193      */
194
195      goto intreg;
196    }
197
198  /* XXX We don't have a good way to return specific errors from ebl calls.
199     This value means we do not understand the type, but it is well-formed
200     DWARF and might be valid.  */
201  return -2;
202}
203