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/* Function return value location for Linux/PPC ABI.
Copyright (C) 2005, 2006 Red Hat, Inc.
This program is Open Source software; you can redistribute it and/or
modify it under the terms of the Open Software License version 1.0 as
published by the Open Source Initiative.
You should have received a copy of the Open Software License along
with this program; if not, you may obtain a copy of the Open Software
License version 1.0 from http://www.opensource.org/licenses/osl.php or
by writing the Open Source Initiative c/o Lawrence Rosen, Esq.,
3001 King Ranch Road, Ukiah, CA 95482. */
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <assert.h>
#include <dwarf.h>
#define BACKEND ppc_
#include "libebl_CPU.h"
/* This is the SVR4 ELF ABI convention, but AIX and Linux do not use it. */
#define SVR4_STRUCT_RETURN 0
/* r3, or pair r3, r4. */
static const Dwarf_Op loc_intreg[] =
{
{ .atom = DW_OP_reg3 }, { .atom = DW_OP_piece, .number = 4 },
{ .atom = DW_OP_reg4 }, { .atom = DW_OP_piece, .number = 4 },
};
#define nloc_intreg 1
#define nloc_intregpair 4
/* f1. */
static const Dwarf_Op loc_fpreg[] =
{
{ .atom = DW_OP_regx, .number = 33 }
};
#define nloc_fpreg 1
/* The return value is a structure and is actually stored in stack space
passed in a hidden argument by the caller. But, the compiler
helpfully returns the address of that space in r3. */
static const Dwarf_Op loc_aggregate[] =
{
{ .atom = DW_OP_breg3, .number = 0 }
};
#define nloc_aggregate 1
int
ppc_return_value_location (Dwarf_Die *functypedie, const Dwarf_Op **locp)
{
/* Start with the function's type, and get the DW_AT_type attribute,
which is the type of the return value. */
Dwarf_Attribute attr_mem;
Dwarf_Attribute *attr = dwarf_attr (functypedie, DW_AT_type, &attr_mem);
if (attr == NULL)
/* The function has no return value, like a `void' function in C. */
return 0;
Dwarf_Die die_mem;
Dwarf_Die *typedie = dwarf_formref_die (attr, &die_mem);
int tag = dwarf_tag (typedie);
/* Follow typedefs and qualifiers to get to the actual type. */
while (tag == DW_TAG_typedef
|| tag == DW_TAG_const_type || tag == DW_TAG_volatile_type
|| tag == DW_TAG_restrict_type || tag == DW_TAG_mutable_type)
{
attr = dwarf_attr (typedie, DW_AT_type, &attr_mem);
typedie = dwarf_formref_die (attr, &die_mem);
tag = dwarf_tag (typedie);
}
Dwarf_Word size;
switch (tag)
{
case -1:
return -1;
case DW_TAG_subrange_type:
if (! dwarf_hasattr (typedie, DW_AT_byte_size))
{
attr = dwarf_attr (typedie, DW_AT_type, &attr_mem);
typedie = dwarf_formref_die (attr, &die_mem);
tag = dwarf_tag (typedie);
}
/* Fall through. */
case DW_TAG_base_type:
case DW_TAG_enumeration_type:
case DW_TAG_pointer_type:
case DW_TAG_ptr_to_member_type:
if (dwarf_formudata (dwarf_attr (typedie, DW_AT_byte_size,
&attr_mem), &size) != 0)
{
if (tag == DW_TAG_pointer_type || tag == DW_TAG_ptr_to_member_type)
size = 4;
else
return -1;
}
if (size <= 8)
{
if (tag == DW_TAG_base_type)
{
Dwarf_Word encoding;
if (dwarf_formudata (dwarf_attr (typedie, DW_AT_encoding,
&attr_mem), &encoding) != 0)
return -1;
if (encoding == DW_ATE_float)
{
*locp = loc_fpreg;
return nloc_fpreg;
}
}
intreg:
*locp = loc_intreg;
return size <= 4 ? nloc_intreg : nloc_intregpair;
}
aggregate:
*locp = loc_aggregate;
return nloc_aggregate;
case DW_TAG_structure_type:
case DW_TAG_class_type:
case DW_TAG_union_type:
case DW_TAG_array_type:
if (SVR4_STRUCT_RETURN
&& dwarf_formudata (dwarf_attr (typedie, DW_AT_byte_size,
&attr_mem), &size) == 0
&& size > 0 && size <= 8)
goto intreg;
goto aggregate;
}
/* XXX We don't have a good way to return specific errors from ebl calls.
This value means we do not understand the type, but it is well-formed
DWARF and might be valid. */
return -2;
}
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