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[patch] Remove excessive DWARF block xmemdup by me [Re: [patch 02/12] entryval: Basic parameter values recovery]
- From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- To: Tom Tromey <tromey at redhat dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Sun, 24 Jul 2011 19:51:23 +0200
- Subject: [patch] Remove excessive DWARF block xmemdup by me [Re: [patch 02/12] entryval: Basic parameter values recovery]
- References: <20110718201528.GC30496@host1.jankratochvil.net> <m3pql65p63.fsf@fleche.redhat.com>
On Tue, 19 Jul 2011 16:19:00 +0200, Tom Tromey wrote:
> >>>>> "Jan" == Jan Kratochvil <jan.kratochvil@redhat.com> writes:
> Jan> +/* Allocate a copy of BLK on CU's objfile_obstack (not comp_unit_obstack),
> Jan> + including a copy of the BLK DWARF code. */
> Jan> +
> Jan> +static struct dwarf2_locexpr_baton *
> Jan> +dlbaton_obstack_copy (const struct dwarf_block *blk, struct dwarf2_cu *cu)
>
> I don't understand the need for this.
>
> Once we have mapped in a DWARF section, we do not unmap it until the
> objfile is destroyed or reloaded. At that point, the types are all
> destroyed as well. So, the lifetimes are already in sync, and you can
> just store a pointer directly to the DWARF data. We already rely on
> this in many cases.
I agree. In such case my recently checked-in patch is also excessively memory
copying this way.
[patch] Fix DW_OP_call2 and DW_OP_call4 for max-cache-age 0 #2
http://sourceware.org/ml/gdb-patches/2011-07/msg00343.html
f35c0b67e636d7ccddfee8ace6b462a73394b482
I will check it in. No regressions on
{x86_64,x86_64-m32,i686}-fedora16pre-linux-gnu.
Thanks,
Jan
gdb/
2011-07-24 Jan Kratochvil <jan.kratochvil@redhat.com>
Remove excessive DWARF expressions memory duplication.
* dwarf2loc.c (per_cu_dwarf_call): Remove variable back_to and its use
for block.data.
(indirect_pieced_value): Remove variable result. Remove variable
back_to and its use for baton.data.
(dwarf2_compile_expr_to_ax): Remove variable back_to and its use for
block.data.
* dwarf2read.c (dwarf2_fetch_die_location_block): Remove xmemdup.
Update the function comment.
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -265,19 +265,14 @@ per_cu_dwarf_call (struct dwarf_expr_context *ctx, size_t die_offset,
void *baton)
{
struct dwarf2_locexpr_baton block;
- struct cleanup *back_to;
block = dwarf2_fetch_die_location_block (die_offset, per_cu,
get_frame_pc, baton);
- back_to = make_cleanup (xfree, (void *) block.data);
-
/* DW_OP_call_ref is currently not supported. */
gdb_assert (block.per_cu == per_cu);
dwarf_expr_eval (ctx, block.data, block.size);
-
- do_cleanups (back_to);
}
/* Helper interface of per_cu_dwarf_call for dwarf2_evaluate_loc_desc. */
@@ -969,9 +964,7 @@ indirect_pieced_value (struct value *value)
struct dwarf2_locexpr_baton baton;
int i, bit_offset, bit_length;
struct dwarf_expr_piece *piece = NULL;
- struct value *result;
LONGEST byte_offset;
- struct cleanup *back_to;
type = check_typedef (value_type (value));
if (TYPE_CODE (type) != TYPE_CODE_PTR)
@@ -1019,15 +1012,9 @@ indirect_pieced_value (struct value *value)
get_frame_address_in_block_wrapper,
frame);
- back_to = make_cleanup (xfree, (void *) baton.data);
-
- result = dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
- baton.data, baton.size, baton.per_cu,
- byte_offset);
-
- do_cleanups (back_to);
-
- return result;
+ return dwarf2_evaluate_loc_desc_full (TYPE_TARGET_TYPE (type), frame,
+ baton.data, baton.size, baton.per_cu,
+ byte_offset);
}
static void *
@@ -2133,14 +2120,12 @@ dwarf2_compile_expr_to_ax (struct agent_expr *expr, struct axs_value *loc,
{
struct dwarf2_locexpr_baton block;
int size = (op == DW_OP_call2 ? 2 : 4);
- struct cleanup *back_to;
uoffset = extract_unsigned_integer (op_ptr, size, byte_order);
op_ptr += size;
block = dwarf2_fetch_die_location_block (uoffset, per_cu,
get_ax_pc, expr);
- back_to = make_cleanup (xfree, (void *) block.data);
/* DW_OP_call_ref is currently not supported. */
gdb_assert (block.per_cu == per_cu);
@@ -2148,8 +2133,6 @@ dwarf2_compile_expr_to_ax (struct agent_expr *expr, struct axs_value *loc,
dwarf2_compile_expr_to_ax (expr, loc, arch, addr_size,
block.data, block.data + block.size,
per_cu);
-
- do_cleanups (back_to);
}
break;
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -13892,9 +13892,9 @@ follow_die_ref (struct die_info *src_die, struct attribute *attr,
return die;
}
-/* Return DWARF block and its CU referenced by OFFSET at PER_CU. Returned
- value is intended for DW_OP_call*. You must call xfree on returned
- dwarf2_locexpr_baton->data. */
+/* Return DWARF block referenced by DW_AT_location of DIE at OFFSET at PER_CU.
+ Returned value is intended for DW_OP_call*. Returned
+ dwarf2_locexpr_baton->data has lifetime of PER_CU->OBJFILE. */
struct dwarf2_locexpr_baton
dwarf2_fetch_die_location_block (unsigned int offset,
@@ -13950,9 +13950,6 @@ dwarf2_fetch_die_location_block (unsigned int offset,
}
retval.per_cu = cu->per_cu;
- if (retval.data)
- retval.data = xmemdup (retval.data, retval.size, retval.size);
-
age_cached_comp_units ();
return retval;