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dwarves/dwarves_reorganize.c
Arnaldo Carvalho de Melo 3f4e4457e2 dwarves: Add DW_TAG_ptr_to_member_type to tag__is_tag_type 
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2009-03-03 15:12:29 -03:00

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/*
Copyright (C) 2006 Mandriva Conectiva S.A.
Copyright (C) 2006 Arnaldo Carvalho de Melo <acme@mandriva.com>
Copyright (C) 2007 Red Hat Inc.
Copyright (C) 2007 Arnaldo Carvalho de Melo <acme@redhat.com>
This program is free software; you can redistribute it and/or modify it
under the terms of version 2 of the GNU General Public License as
published by the Free Software Foundation.
*/
#include "list.h"
#include "dwarves_reorganize.h"
#include "dwarves.h"
void class__subtract_offsets_from(struct class *self, const struct cu *cu,
struct class_member *from,
const uint16_t size)
{
struct class_member *member =
list_prepare_entry(from, class__tags(self), tag.node);
list_for_each_entry_continue(member, class__tags(self), tag.node)
if (member->tag.tag == DW_TAG_member)
member->offset -= size;
if (self->padding != 0) {
struct class_member *last_member =
type__last_member(&self->type);
const size_t last_member_size =
class_member__size(last_member, cu);
const ssize_t new_padding =
(class__size(self) -
(last_member->offset + last_member_size));
if (new_padding > 0)
self->padding = new_padding;
else
self->padding = 0;
}
}
void class__add_offsets_from(struct class *self, struct class_member *from,
const uint16_t size)
{
struct class_member *member =
list_prepare_entry(from, class__tags(self), tag.node);
list_for_each_entry_continue(member, class__tags(self), tag.node)
if (member->tag.tag == DW_TAG_member)
member->offset += size;
}
/*
* XXX: Check this more thoroughly. Right now it is used because I was
* to lazy to do class__remove_member properly, adjusting alignments and
* holes as we go removing fields. Ditto for class__add_offsets_from.
*/
void class__fixup_alignment(struct class *self, const struct cu *cu)
{
struct class_member *pos, *last_member = NULL;
size_t member_size;
size_t power2;
type__for_each_data_member(&self->type, pos) {
member_size = class_member__size(pos, cu);
if (last_member == NULL && pos->offset != 0) { /* paranoid! */
class__subtract_offsets_from(self, cu, pos,
pos->offset - member_size);
pos->offset = 0;
} else if (last_member != NULL &&
last_member->hole >= cu->addr_size) {
size_t dec = (last_member->hole / cu->addr_size) *
cu->addr_size;
last_member->hole -= dec;
if (last_member->hole == 0)
--self->nr_holes;
pos->offset -= dec;
self->type.size -= dec;
class__subtract_offsets_from(self, cu, pos, dec);
} else for (power2 = cu->addr_size; power2 >= 2; power2 /= 2) {
const size_t remainder = pos->offset % power2;
if (member_size == power2) {
if (remainder == 0) /* perfectly aligned */
break;
if (last_member->hole >= remainder) {
last_member->hole -= remainder;
if (last_member->hole == 0)
--self->nr_holes;
pos->offset -= remainder;
class__subtract_offsets_from(self, cu, pos, remainder);
} else {
const size_t inc = power2 - remainder;
if (last_member->hole == 0)
++self->nr_holes;
last_member->hole += inc;
pos->offset += inc;
self->type.size += inc;
class__add_offsets_from(self, pos, inc);
}
}
}
last_member = pos;
}
if (last_member != NULL) {
struct class_member *m =
type__find_first_biggest_size_base_type_member(&self->type, cu);
size_t unpadded_size = last_member->offset + class_member__size(last_member, cu);
size_t m_size = class_member__size(m, cu), remainder;
/* google for struct zone_padding in the linux kernel for an example */
if (m_size == 0)
return;
remainder = unpadded_size % m_size;
if (remainder != 0) {
self->padding = m_size - remainder;
self->type.size = unpadded_size + self->padding;
}
}
}
static struct class_member *
class__find_next_hole_of_size(struct class *class,
struct class_member *from,
const struct cu *cu, size_t size)
{
struct class_member *member =
list_prepare_entry(from, class__tags(class), tag.node);
struct class_member *bitfield_head = NULL;
list_for_each_entry_continue(member, class__tags(class), tag.node) {
if (member->tag.tag != DW_TAG_member)
continue;
if (member->bit_size != 0) {
if (bitfield_head == NULL)
bitfield_head = member;
} else
bitfield_head = NULL;
if (member->hole != 0) {
const size_t member_size = class_member__size(member, cu);
if (member_size != 0 && member_size <= size)
return bitfield_head ? : member;
}
}
return NULL;
}
static struct class_member *
class__find_last_member_of_size(struct class *class,
struct class_member *to,
const struct cu *cu, size_t size)
{
struct class_member *member;
list_for_each_entry_reverse(member, class__tags(class), tag.node) {
size_t member_size;
if (member->tag.tag != DW_TAG_member)
continue;
if (member == to)
break;
/*
* Check if this is the first member of a bitfield. It either
* has another member before it that is not part of the current
* bitfield or it is the first member of the struct.
*/
if (member->bit_size != 0 && member->offset != 0) {
struct class_member *prev =
list_entry(member->tag.node.prev,
struct class_member,
tag.node);
if (prev->bit_size != 0)
continue;
}
member_size = class_member__size(member, cu);
if (member_size != 0 && member_size <= size)
return member;
}
return NULL;
}
static struct class_member *
class__find_next_bit_hole_of_size(struct class *class,
struct class_member *from,
size_t size)
{
struct class_member *member =
list_prepare_entry(from, class__tags(class), tag.node);
list_for_each_entry_continue(member, class__tags(class), tag.node) {
if (member->tag.tag != DW_TAG_member)
continue;
if (member->bit_hole != 0 &&
member->bit_size <= size)
return member;
}
#if 0
/*
* FIXME: Handle the case where the bit padding is on the same bitfield
* that we're looking, i.e. we can't combine a bitfield with itself,
* perhaps we should tag bitfields with a sequential, clearly marking
* each of the bitfields in advance, so that all the algoriths that
* have to deal with bitfields, moving them around, demoting, etc, can
* be simplified.
*/
/*
* Now look if the last member is a one member bitfield,
* i.e. if we have bit_padding
*/
if (class->bit_padding != 0)
return type__last_member(&class->type);
#endif
return NULL;
}
static void class__move_member(struct class *class, struct class_member *dest,
struct class_member *from, const struct cu *cu,
int from_padding, const int verbose, FILE *fp)
{
const size_t from_size = class_member__size(from, cu);
const size_t dest_size = class_member__size(dest, cu);
const bool from_was_last = from->tag.node.next == class__tags(class);
struct class_member *tail_from = from;
struct class_member *from_prev = list_entry(from->tag.node.prev,
struct class_member,
tag.node);
uint16_t orig_tail_from_hole = tail_from->hole;
const uint16_t orig_from_offset = from->offset;
/*
* Align 'from' after 'dest':
*/
const uint16_t offset = dest->hole % (from_size > cu->addr_size ?
cu->addr_size : from_size);
/*
* Set new 'from' offset, after 'dest->offset', aligned
*/
const uint16_t new_from_offset = dest->offset + dest_size + offset;
if (verbose)
fputs("/* Moving", fp);
if (from->bit_size != 0) {
struct class_member *pos =
list_prepare_entry(from, class__tags(class),
tag.node);
struct class_member *tmp;
uint8_t orig_tail_from_bit_hole;
LIST_HEAD(from_list);
if (verbose)
fprintf(fp, " bitfield('%s' ... ", class_member__name(from));
list_for_each_entry_safe_from(pos, tmp, class__tags(class),
tag.node) {
if (pos->tag.tag != DW_TAG_member)
continue;
/*
* Have we reached the end of the bitfield?
*/
if (pos->offset != orig_from_offset)
break;
tail_from = pos;
orig_tail_from_hole = tail_from->hole;
orig_tail_from_bit_hole = tail_from->bit_hole;
pos->offset = new_from_offset;
pos->hole = 0;
pos->bit_hole = 0;
list_move_tail(&pos->tag.node, &from_list);
}
tail_from->bit_hole = orig_tail_from_bit_hole;
list_splice(&from_list, &dest->tag.node);
if (verbose)
fprintf(fp, "'%s')", class_member__name(tail_from));
} else {
if (verbose)
fprintf(fp, " '%s'", class_member__name(from));
/*
* Remove 'from' from the list
*/
list_del(&from->tag.node);
/*
* Add 'from' after 'dest':
*/
__list_add(&from->tag.node, &dest->tag.node,
dest->tag.node.next);
from->offset = new_from_offset;
}
if (verbose)
fprintf(fp, " from after '%s' to after '%s' */\n",
class_member__name(from_prev),
class_member__name(dest));
if (from_padding) {
/*
* Check if we're eliminating the need for padding:
*/
if (orig_from_offset % cu->addr_size == 0) {
/*
* Good, no need for padding anymore:
*/
class->type.size -= from_size + class->padding;
class->padding = 0;
} else {
/*
* No, so just add from_size to the padding:
*/
class->padding += from_size;
if (verbose)
fprintf(fp, "/* adding %zd bytes from %s to "
"the padding */\n",
from_size, class_member__name(from));
}
} else if (from_was_last) {
class->type.size -= from_size + class->padding;
class->padding = 0;
} else {
/*
* See if we are adding a new hole that is bigger than
* sizeof(long), this may have problems with explicit alignment
* made by the programmer, perhaps we need A switch that allows
* us to avoid realignment, just using existing holes but
* keeping the existing alignment, anyway the programmer has to
* check the resulting rerganization before using it, and for
* automatic stuff such as the one that will be used for struct
* "views" in tools such as ctracer we are more interested in
* packing the subset as tightly as possible.
*/
if (orig_tail_from_hole + from_size >= cu->addr_size) {
class->type.size -= cu->addr_size;
class__subtract_offsets_from(class, cu, from_prev,
cu->addr_size);
} else {
/*
* Add the hole after 'from' + its size to the member
* before it:
*/
from_prev->hole += orig_tail_from_hole + from_size;
}
/*
* Check if we have eliminated a hole
*/
if (dest->hole == from_size)
class->nr_holes--;
}
tail_from->hole = dest->hole - (from_size + offset);
dest->hole = offset;
if (verbose > 1) {
class__find_holes(class, cu);
class__fprintf(class, cu, NULL, fp);
fputc('\n', fp);
}
}
static void class__move_bit_member(struct class *class, const struct cu *cu,
struct class_member *dest,
struct class_member *from,
const int verbose, FILE *fp)
{
struct class_member *from_prev = list_entry(from->tag.node.prev,
struct class_member,
tag.node);
const uint8_t is_last_member = (from->tag.node.next ==
class__tags(class));
if (verbose)
fprintf(fp, "/* Moving '%s:%u' from after '%s' to "
"after '%s:%u' */\n",
class_member__name(from), from->bit_size,
class_member__name(from_prev),
class_member__name(dest), dest->bit_size);
/*
* Remove 'from' from the list
*/
list_del(&from->tag.node);
/*
* Add from after dest:
*/
__list_add(&from->tag.node,
&dest->tag.node,
dest->tag.node.next);
/* Check if this was the last entry in the bitfield */
if (from_prev->bit_size == 0) {
size_t from_size = class_member__size(from, cu);
/*
* Are we shrinking the struct?
*/
if (from_size + from->hole >= cu->addr_size) {
class->type.size -= from_size + from->hole;
class__subtract_offsets_from(class, cu, from_prev,
from_size + from->hole);
} else if (is_last_member)
class->padding += from_size;
else
from_prev->hole += from_size + from->hole;
if (is_last_member) {
/*
* Now we don't have bit_padding anymore
*/
class->bit_padding = 0;
} else
class->nr_bit_holes--;
} else {
/*
* Add add the holes after from + its size to the member
* before it:
*/
from_prev->bit_hole += from->bit_hole + from->bit_size;
from_prev->hole = from->hole;
}
from->bit_hole = dest->bit_hole - from->bit_size;
/*
* Tricky, what are the rules for bitfield layouts on this arch?
* Assume its IA32
*/
from->bit_offset = dest->bit_offset + dest->bit_size;
/*
* Now both have the some offset:
*/
from->offset = dest->offset;
dest->bit_hole = 0;
from->hole = dest->hole;
dest->hole = 0;
if (verbose > 1) {
class__find_holes(class, cu);
class__fprintf(class, cu, NULL, fp);
fputc('\n', fp);
}
}
static void class__demote_bitfield_members(struct class *class,
struct class_member *from,
struct class_member *to,
const struct base_type *old_type,
const struct base_type *new_type)
{
const uint8_t bit_diff = old_type->bit_size - new_type->bit_size;
struct class_member *member =
list_prepare_entry(from, class__tags(class), tag.node);
list_for_each_entry_from(member, class__tags(class), tag.node) {
if (member->tag.tag != DW_TAG_member)
continue;
/*
* Assume IA32 bitfield layout
*/
member->bit_offset -= bit_diff;
member->tag.type = new_type->tag.id;
if (member == to)
break;
member->bit_hole = 0;
}
}
static struct tag *cu__find_base_type_of_size(const struct cu *cu,
const size_t size)
{
const char *type_name, *type_name_alt = NULL;
switch (size) {
case sizeof(unsigned char):
type_name = "unsigned char"; break;
case sizeof(unsigned short int):
type_name = "short unsigned int";
type_name = "unsigned short"; break;
case sizeof(unsigned int):
type_name = "unsigned int";
type_name_alt = "unsigned"; break;
case sizeof(unsigned long long):
if (cu->addr_size == 8) {
type_name = "long unsigned int";
type_name_alt = "unsigned long";
} else {
type_name = "long long unsigned int";
type_name_alt = "unsigned long long";
}
break;
default:
return NULL;
}
struct tag *ret = cu__find_base_type_by_name(cu, type_name);
return ret ?: cu__find_base_type_by_name(cu, type_name_alt);
}
static int class__demote_bitfields(struct class *class, const struct cu *cu,
const int verbose, FILE *fp)
{
struct class_member *member;
struct class_member *bitfield_head = NULL;
const struct tag *old_type_tag, *new_type_tag;
size_t current_bitfield_size = 0, size, bytes_needed, new_size;
int some_was_demoted = 0;
type__for_each_data_member(&class->type, member) {
/*
* Check if we are moving away from a bitfield
*/
if (member->bit_size == 0) {
current_bitfield_size = 0;
bitfield_head = NULL;
} else {
if (bitfield_head == NULL) {
bitfield_head = member;
current_bitfield_size = member->bit_size;
} else if (bitfield_head->offset != member->offset) {
/*
* We moved from one bitfield to another, for
* now don't handle this case, just move on to
* the next bitfield, we may well move it to
* another place and then the first bitfield will
* be isolated and will be handled in the next
* pass.
*/
bitfield_head = member;
current_bitfield_size = member->bit_size;
} else
current_bitfield_size += member->bit_size;
}
/*
* Have we got to the end of a bitfield with holes?
*/
if (member->bit_hole == 0)
continue;
size = class_member__size(member, cu);
bytes_needed = (current_bitfield_size + 7) / 8;
if (bytes_needed == size)
continue;
old_type_tag = cu__find_type_by_id(cu, member->tag.type);
new_type_tag = cu__find_base_type_of_size(cu, bytes_needed);
if (new_type_tag == NULL) {
fprintf(fp, "/* BRAIN FART ALERT! couldn't find a "
"%zd bytes base type */\n\n", bytes_needed);
continue;
}
if (verbose)
fprintf(fp, "/* Demoting bitfield ('%s' ... '%s') "
"from '%s' to '%s' */\n",
class_member__name(bitfield_head),
class_member__name(member),
base_type__name(tag__base_type(old_type_tag)),
base_type__name(tag__base_type(new_type_tag)));
class__demote_bitfield_members(class,
bitfield_head, member,
tag__base_type(old_type_tag),
tag__base_type(new_type_tag));
new_size = class_member__size(member, cu);
member->hole = size - new_size;
if (member->hole != 0)
++class->nr_holes;
member->bit_hole = new_size * 8 - current_bitfield_size;
some_was_demoted = 1;
/*
* Have we packed it so that there are no hole now?
*/
if (member->bit_hole == 0)
--class->nr_bit_holes;
if (verbose > 1) {
class__find_holes(class, cu);
class__fprintf(class, cu, NULL, fp);
fputc('\n', fp);
}
}
/*
* Now look if we have bit padding, i.e. if the the last member
* is a bitfield and its the sole member in this bitfield, i.e.
* if it wasn't already demoted as part of a bitfield of more than
* one member:
*/
member = type__last_member(&class->type);
if (class->bit_padding != 0 && bitfield_head == member) {
size = class_member__size(member, cu);
bytes_needed = (member->bit_size + 7) / 8;
if (bytes_needed < size) {
old_type_tag =
cu__find_type_by_id(cu, member->tag.type);
new_type_tag =
cu__find_base_type_of_size(cu, bytes_needed);
tag__assert_search_result(old_type_tag);
tag__assert_search_result(new_type_tag);
if (verbose)
fprintf(fp, "/* Demoting bitfield ('%s') "
"from '%s' to '%s' */\n",
class_member__name(member),
base_type__name(tag__base_type(old_type_tag)),
base_type__name(tag__base_type(new_type_tag)));
class__demote_bitfield_members(class,
member, member,
tag__base_type(old_type_tag),
tag__base_type(new_type_tag));
new_size = class_member__size(member, cu);
member->hole = 0;
/*
* Do we need byte padding?
*/
if (member->offset + new_size < class__size(class)) {
class->padding = (class__size(class) -
(member->offset + new_size));
class->bit_padding = 0;
member->bit_hole = (new_size * 8 -
member->bit_size);
} else {
class->padding = 0;
class->bit_padding = (new_size * 8 -
member->bit_size);
member->bit_hole = 0;
}
some_was_demoted = 1;
if (verbose > 1) {
class__find_holes(class, cu);
class__fprintf(class, cu, NULL, fp);
fputc('\n', fp);
}
}
}
return some_was_demoted;
}
static void class__reorganize_bitfields(struct class *class,
const struct cu *cu,
const int verbose, FILE *fp)
{
struct class_member *member, *brother;
restart:
type__for_each_data_member(&class->type, member) {
/* See if we have a hole after this member */
if (member->bit_hole != 0) {
/*
* OK, try to find a member that has a bit hole after
* it and that has a size that fits the current hole:
*/
brother =
class__find_next_bit_hole_of_size(class, member,
member->bit_hole);
if (brother != NULL) {
class__move_bit_member(class, cu,
member, brother,
verbose, fp);
goto restart;
}
}
}
}
static void class__fixup_bitfield_types(struct class *self,
struct class_member *from,
struct class_member *to_before,
Dwarf_Off type)
{
struct class_member *member =
list_prepare_entry(from, class__tags(self), tag.node);
list_for_each_entry_from(member, class__tags(self), tag.node) {
if (member->tag.tag != DW_TAG_member)
continue;
if (member == to_before)
break;
member->tag.type = type;
}
}
/*
* Think about this pahole output a bit:
*
* [filo examples]$ pahole swiss_cheese cheese
* / * <11b> /home/acme/git/pahole/examples/swiss_cheese.c:3 * /
* struct cheese {
* <SNIP>
* int bitfield1:1; / * 64 4 * /
* int bitfield2:1; / * 64 4 * /
*
* / * XXX 14 bits hole, try to pack * /
* / * Bitfield WARNING: DWARF size=4, real size=2 * /
*
* short int d; / * 66 2 * /
* <SNIP>
*
* The compiler (gcc 4.1.1 20070105 (Red Hat 4.1.1-51) in the above example),
* Decided to combine what was declared as an int (4 bytes) bitfield but doesn't
* uses even one byte with the next field, that is a short int (2 bytes),
* without demoting the type of the bitfield to short int (2 bytes), so in terms
* of alignment the real size is 2, not 4, to make things easier for the rest of
* the reorganizing routines we just do the demotion ourselves, fixing up the
* sizes.
*/
static void class__fixup_member_types(struct class *self, const struct cu *cu,
const uint8_t verbose, FILE *fp)
{
struct class_member *pos, *bitfield_head = NULL;
uint8_t fixup_was_done = 0;
type__for_each_data_member(&self->type, pos) {
/*
* Is this bitfield member?
*/
if (pos->bit_size != 0) {
/*
* The first entry in a bitfield?
*/
if (bitfield_head == NULL)
bitfield_head = pos;
continue;
}
/*
* OK, not a bitfield member, but have we just passed
* by a bitfield?
*/
if (bitfield_head != NULL) {
const uint16_t real_size = (pos->offset -
bitfield_head->offset);
const size_t size = class_member__size(bitfield_head,
cu);
if (real_size != size) {
struct tag *new_type_tag =
cu__find_base_type_of_size(cu,
real_size);
if (new_type_tag == NULL) {
fprintf(stderr, "pahole: couldn't find"
" a base_type of %d bytes!\n",
real_size);
continue;
}
class__fixup_bitfield_types(self,
bitfield_head, pos,
new_type_tag->id);
fixup_was_done = 1;
}
}
bitfield_head = NULL;
}
if (verbose && fixup_was_done) {
fprintf(fp, "/* bitfield types were fixed */\n");
if (verbose > 1) {
class__find_holes(self, cu);
class__fprintf(self, cu, NULL, fp);
fputc('\n', fp);
}
}
}
void class__reorganize(struct class *self, const struct cu *cu,
const int verbose, FILE *fp)
{
struct class_member *member, *brother, *last_member;
size_t last_member_size;
class__fixup_member_types(self, cu, verbose, fp);
while (class__demote_bitfields(self, cu, verbose, fp))
class__reorganize_bitfields(self, cu, verbose, fp);
/* Now try to combine holes */
restart:
class__find_holes(self, cu);
/*
* It can be NULL if this class doesn't have any data members,
* just inheritance entries
*/
last_member = type__last_member(&self->type);
if (last_member == NULL)
return;
last_member_size = class_member__size(last_member, cu);
type__for_each_data_member(&self->type, member) {
/* See if we have a hole after this member */
if (member->hole != 0) {
/*
* OK, try to find a member that has a hole after it
* and that has a size that fits the current hole:
*/
brother = class__find_next_hole_of_size(self, member,
cu,
member->hole);
if (brother != NULL) {
struct class_member *brother_prev =
list_entry(brother->tag.node.prev,
struct class_member,
tag.node);
/*
* If it the next member, avoid moving it closer,
* it could be a explicit alignment rule, like
* ____cacheline_aligned_in_smp in the Linux
* kernel.
*/
if (brother_prev != member) {
class__move_member(self, member,
brother, cu, 0,
verbose, fp);
goto restart;
}
}
/*
* OK, but is there padding? If so the last member
* has a hole, if we are not at the last member and
* it has a size that is smaller than the current hole
* we can move it after the current member, reducing
* the padding or eliminating it altogether.
*/
if (self->padding > 0 &&
member != last_member &&
last_member_size != 0 &&
last_member_size <= member->hole) {
class__move_member(self, member, last_member,
cu, 1, verbose, fp);
goto restart;
}
}
}
/* Now try to move members at the tail to after holes */
if (self->nr_holes == 0)
return;
type__for_each_data_member(&self->type, member) {
/* See if we have a hole after this member */
if (member->hole != 0) {
brother = class__find_last_member_of_size(self, member,
cu,
member->hole);
if (brother != NULL) {
struct class_member *brother_prev =
list_entry(brother->tag.node.prev,
struct class_member,
tag.node);
/*
* If it the next member, avoid moving it closer,
* it could be a explicit alignment rule, like
* ____cacheline_aligned_in_smp in the Linux
* kernel.
*/
if (brother_prev != member) {
class__move_member(self, member,
brother, cu, 0,
verbose, fp);
goto restart;
}
}
}
}
}
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