diff options
Diffstat (limited to 'backends/i386_retval.c')
| -rw-r--r-- | backends/i386_retval.c | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/backends/i386_retval.c b/backends/i386_retval.c new file mode 100644 index 00000000..34cae064 --- /dev/null +++ b/backends/i386_retval.c @@ -0,0 +1,139 @@ +/* Function return value location for Linux/i386 ABI. + Copyright (C) 2005 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 i386_ +#include "libebl_CPU.h" + + +/* %eax, or pair %eax, %edx. */ +static const Dwarf_Op loc_intreg[] = + { + { .atom = DW_OP_reg0 }, { .atom = DW_OP_piece, .number = 4 }, + { .atom = DW_OP_reg1 }, { .atom = DW_OP_piece, .number = 4 }, + }; +#define nloc_intreg 1 +#define nloc_intregpair 4 + +/* %st(0). */ +static const Dwarf_Op loc_fpreg[] = + { + { .atom = DW_OP_reg11 } + }; +#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 %eax. */ +static const Dwarf_Op loc_aggregate[] = + { + { .atom = DW_OP_breg0, .number = 0 } + }; +#define nloc_aggregate 1 + +int +i386_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); + } + + 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: + { + Dwarf_Word size; + 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 (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) + { + if (size > 16) + return -2; + *locp = loc_fpreg; + return nloc_fpreg; + } + } + *locp = loc_intreg; + if (size <= 4) + return nloc_intreg; + if (size <= 8) + return nloc_intregpair; + + /* Else fall through. */ + } + + case DW_TAG_structure_type: + case DW_TAG_class_type: + case DW_TAG_union_type: + case DW_TAG_array_type: + *locp = loc_aggregate; + return nloc_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; +} |