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[commit/dwarf2] Delay loading of needed compilation units
- From: Daniel Jacobowitz <drow at false dot org>
- To: gdb-patches at sourceware dot org
- Date: Wed, 20 Aug 2008 16:33:50 -0400
- Subject: [commit/dwarf2] Delay loading of needed compilation units
This is performance-neutral, another clarity improvement rather than
performance. We don't need to load required compilation units as
early as read_full_die; we only need to load them if we follow a
reference to them (so, for instance, if we never follow the reference
we do not need the target CU).
Tested on x86_64-linux, committed.
--
Daniel Jacobowitz
CodeSourcery
2008-08-20 Daniel Jacobowitz <dan@codesourcery.com>
* dwarf2read.c (queue_comp_unit): Take an objfile argument. Read
in the DIEs here.
(process_queue): Do not read in the DIEs here.
(psymtab_to_symtab_1): Update call to queue_comp_unit.
(read_full_die): Do not call queue_comp_unit from here.
(maybe_queue_comp_unit): New function.
(follow_die_ref): Use it.
---
gdb/dwarf2read.c | 97 ++++++++++++++++++++++++-------------------------------
1 file changed, 43 insertions(+), 54 deletions(-)
Index: src/gdb/dwarf2read.c
===================================================================
--- src.orig/gdb/dwarf2read.c 2008-08-10 11:50:43.000000000 -0400
+++ src/gdb/dwarf2read.c 2008-08-20 13:05:52.000000000 -0400
@@ -2424,7 +2424,7 @@ dwarf2_psymtab_to_symtab (struct partial
/* Add PER_CU to the queue. */
static void
-queue_comp_unit (struct dwarf2_per_cu_data *per_cu)
+queue_comp_unit (struct dwarf2_per_cu_data *per_cu, struct objfile *objfile)
{
struct dwarf2_queue_item *item;
@@ -2439,6 +2439,12 @@ queue_comp_unit (struct dwarf2_per_cu_da
dwarf2_queue_tail->next = item;
dwarf2_queue_tail = item;
+
+ /* Either PER_CU is the CU we want to process, or we're following a reference
+ pointing into PER_CU. Either way, we need its DIEs now. */
+ load_full_comp_unit (item->per_cu, objfile);
+ item->per_cu->cu->read_in_chain = dwarf2_per_objfile->read_in_chain;
+ dwarf2_per_objfile->read_in_chain = item->per_cu;
}
/* Process the queue. */
@@ -2448,22 +2454,8 @@ process_queue (struct objfile *objfile)
{
struct dwarf2_queue_item *item, *next_item;
- /* Initially, there is just one item on the queue. Load its DIEs,
- and the DIEs of any other compilation units it requires,
- transitively. */
-
- for (item = dwarf2_queue; item != NULL; item = item->next)
- {
- /* Read in this compilation unit. This may add new items to
- the end of the queue. */
- load_full_comp_unit (item->per_cu, objfile);
-
- item->per_cu->cu->read_in_chain = dwarf2_per_objfile->read_in_chain;
- dwarf2_per_objfile->read_in_chain = item->per_cu;
- }
-
- /* Now everything left on the queue needs to be read in. Process
- them, one at a time, removing from the queue as we finish. */
+ /* The queue starts out with one item, but following a DIE reference
+ may load a new CU, adding it to the end of the queue. */
for (item = dwarf2_queue; item != NULL; dwarf2_queue = item = next_item)
{
if (item->per_cu->psymtab && !item->per_cu->psymtab->readin)
@@ -2545,7 +2537,7 @@ psymtab_to_symtab_1 (struct partial_symt
back_to = make_cleanup (dwarf2_release_queue, NULL);
- queue_comp_unit (per_cu);
+ queue_comp_unit (per_cu, pst->objfile);
process_queue (pst->objfile);
@@ -6072,42 +6064,8 @@ read_full_die (struct die_info **diep, b
die->num_attrs = abbrev->num_attrs;
for (i = 0; i < abbrev->num_attrs; ++i)
- {
- info_ptr = read_attribute (&die->attrs[i], &abbrev->attrs[i],
- abfd, info_ptr, cu);
-
- /* If this attribute is an absolute reference to a different
- compilation unit, make sure that compilation unit is loaded
- also. */
- if (die->attrs[i].form == DW_FORM_ref_addr
- && (DW_ADDR (&die->attrs[i]) < cu->header.offset
- || (DW_ADDR (&die->attrs[i])
- >= cu->header.offset + cu->header.length)))
- {
- struct dwarf2_per_cu_data *per_cu;
- per_cu = dwarf2_find_containing_comp_unit (DW_ADDR (&die->attrs[i]),
- cu->objfile);
-
- /* Mark the dependence relation so that we don't flush PER_CU
- too early. */
- dwarf2_add_dependence (cu, per_cu);
-
- /* If it's already on the queue, we have nothing to do. */
- if (per_cu->queued)
- continue;
-
- /* If the compilation unit is already loaded, just mark it as
- used. */
- if (per_cu->cu != NULL)
- {
- per_cu->cu->last_used = 0;
- continue;
- }
-
- /* Add it to the queue. */
- queue_comp_unit (per_cu);
- }
- }
+ info_ptr = read_attribute (&die->attrs[i], &abbrev->attrs[i],
+ abfd, info_ptr, cu);
*diep = die;
*has_children = abbrev->has_children;
@@ -9170,6 +9128,33 @@ dwarf2_get_attr_constant_value (struct a
}
}
+/* THIS_CU has a reference to PER_CU. If necessary, load the new compilation
+ unit and add it to our queue. */
+
+static void
+maybe_queue_comp_unit (struct dwarf2_cu *this_cu,
+ struct dwarf2_per_cu_data *per_cu)
+{
+ /* Mark the dependence relation so that we don't flush PER_CU
+ too early. */
+ dwarf2_add_dependence (this_cu, per_cu);
+
+ /* If it's already on the queue, we have nothing to do. */
+ if (per_cu->queued)
+ return;
+
+ /* If the compilation unit is already loaded, just mark it as
+ used. */
+ if (per_cu->cu != NULL)
+ {
+ per_cu->cu->last_used = 0;
+ return;
+ }
+
+ /* Add it to the queue. */
+ queue_comp_unit (per_cu, this_cu->objfile);
+}
+
static struct die_info *
follow_die_ref (struct die_info *src_die, struct attribute *attr,
struct dwarf2_cu *cu)
@@ -9187,6 +9172,10 @@ follow_die_ref (struct die_info *src_die
struct dwarf2_per_cu_data *per_cu;
per_cu = dwarf2_find_containing_comp_unit (DW_ADDR (attr),
cu->objfile);
+
+ /* If necessary, add it to the queue and load its DIEs. */
+ maybe_queue_comp_unit (cu, per_cu);
+
target_cu = per_cu->cu;
}
else