Mark Wielaard is implementing support for LVU and IEPM in elfutils, and
he was surprised by the encoding of DW_AT_GNU_entry_view; so was I!
When GCC computes and outputs views internally (broken without internal
view resets), it outputs entry_view attributes as data: it knows the
view numbers. However, when it uses the assembler to compute the views
symbolically, it has to output the view symbolically.
I'd chosen lbl_id to that end, without giving it much thought, but that
was no good: it's not just space-inefficient, it uses an addr encoding,
indirect in some cases, for something that's not a real label, but
rather a a small assembler data constant. Oops.
Regstrapped on i686- and x86_64-linux-gnu. Ok to install?
[IEPM] [PR debug/84620] use constant form for DW_AT_GNU_entry_view
When outputting entry views in symbolic mode, we used to use a lbl_id,
but that outputs the view as an addr, perhaps even in an indirect one,
which is all excessive and undesirable for a small assembler-computed
constant.
Introduce a new value class for symbolic views, so that we can output
the labels as constant data, using small forms that should suffice for
any symbolic views.
Ideally, we'd use uleb128, but then the compiler would have to defer
.debug_info offset computation to the assembler. I'm not going there
for now, so a symbolic uleb128 assembler constant in an attribute is
not something GCC can deal with ATM.
for gcc/ChangeLog
PR debug/84620
* dwarf2out.h (dw_val_class): Add dw_val_class_symview.
(dw_val_node): Add val_symbolic_view.
* dwarf2out.c (dw_val_equal_p): Handle symview.
(add_AT_symview): New.
(print_dw_val): Handle symview.
(attr_checksum, attr_checksum_ordered): Likewise.
(same_dw_val_p, size_of_die): Likewise.
(value_format, output_die): Likewise.
(add_high_low_attributes): Use add_AT_symview for entry_view.
---
gcc/dwarf2out.c | 40 +++++++++++++++++++++++++++++++++++++++-
gcc/dwarf2out.h | 4 +++-
2 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 41bb11558f69..b52edee845f2 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -1434,6 +1434,8 @@ dw_val_equal_p (dw_val_node *a, dw_val_node *b)
return a->v.val_die_ref.die == b->v.val_die_ref.die;
case dw_val_class_fde_ref:
return a->v.val_fde_index == b->v.val_fde_index;
+ case dw_val_class_symview:
+ return strcmp (a->v.val_symbolic_view, b->v.val_symbolic_view) == 0;
case dw_val_class_lbl_id:
case dw_val_class_lineptr:
case dw_val_class_macptr:
@@ -3600,6 +3602,7 @@ static addr_table_entry *add_addr_table_entry (void *,
enum ate_kind);
static void remove_addr_table_entry (addr_table_entry *);
static void add_AT_addr (dw_die_ref, enum dwarf_attribute, rtx, bool);
static inline rtx AT_addr (dw_attr_node *);
+static void add_AT_symview (dw_die_ref, enum dwarf_attribute, const char *);
static void add_AT_lbl_id (dw_die_ref, enum dwarf_attribute, const char *);
static void add_AT_lineptr (dw_die_ref, enum dwarf_attribute, const char *);
static void add_AT_macptr (dw_die_ref, enum dwarf_attribute, const char *);
@@ -5114,6 +5117,21 @@ add_AT_vms_delta (dw_die_ref die, enum dwarf_attribute
attr_kind,
add_dwarf_attr (die, &attr);
}
+/* Add a symbolic view identifier attribute value to a DIE. */
+
+static inline void
+add_AT_symview (dw_die_ref die, enum dwarf_attribute attr_kind,
+ const char *view_label)
+{
+ dw_attr_node attr;
+
+ attr.dw_attr = attr_kind;
+ attr.dw_attr_val.val_class = dw_val_class_symview;
+ attr.dw_attr_val.val_entry = NULL;
+ attr.dw_attr_val.v.val_symbolic_view = xstrdup (view_label);
+ add_dwarf_attr (die, &attr);
+}
+
/* Add a label identifier attribute value to a DIE. */
static inline void
@@ -6457,6 +6475,9 @@ print_dw_val (dw_val_node *val, bool recurse, FILE
*outfile)
fprintf (outfile, "delta: @slotcount(%s-%s)",
val->v.val_vms_delta.lbl2, val->v.val_vms_delta.lbl1);
break;
+ case dw_val_class_symview:
+ fprintf (outfile, "view: %s", val->v.val_symbolic_view);
+ break;
case dw_val_class_lbl_id:
case dw_val_class_lineptr:
case dw_val_class_macptr:
@@ -6828,6 +6849,7 @@ attr_checksum (dw_attr_node *at, struct md5_ctx *ctx, int
*mark)
case dw_val_class_fde_ref:
case dw_val_class_vms_delta:
+ case dw_val_class_symview:
case dw_val_class_lbl_id:
case dw_val_class_lineptr:
case dw_val_class_macptr:
@@ -7124,6 +7146,7 @@ attr_checksum_ordered (enum dwarf_tag tag, dw_attr_node
*at,
break;
case dw_val_class_fde_ref:
+ case dw_val_class_symview:
case dw_val_class_lbl_id:
case dw_val_class_lineptr:
case dw_val_class_macptr:
@@ -7624,6 +7647,9 @@ same_dw_val_p (const dw_val_node *v1, const dw_val_node
*v2, int *mark)
case dw_val_class_die_ref:
return same_die_p (v1->v.val_die_ref.die, v2->v.val_die_ref.die, mark);
+ case dw_val_class_symview:
+ return strcmp (v1->v.val_symbolic_view, v2->v.val_symbolic_view) == 0;
+
case dw_val_class_fde_ref:
case dw_val_class_vms_delta:
case dw_val_class_lbl_id:
@@ -9284,6 +9310,10 @@ size_of_die (dw_die_ref die)
size += csize;
}
break;
+ case dw_val_class_symview:
+ /* FIXME: Use uleb128 rather than data2. */
+ size += 2;
+ break;
case dw_val_class_const_implicit:
case dw_val_class_unsigned_const_implicit:
case dw_val_class_file_implicit:
@@ -9732,6 +9762,9 @@ value_format (dw_attr_node *a)
default:
return DW_FORM_block1;
}
+ case dw_val_class_symview:
+ /* FIXME: Use uleb128 rather than data2. */
+ return DW_FORM_data2;
case dw_val_class_vec:
switch (constant_size (a->dw_attr_val.v.val_vec.length
* a->dw_attr_val.v.val_vec.elt_size))
@@ -10497,6 +10530,11 @@ output_die (dw_die_ref die)
}
break;
+ case dw_val_class_symview:
+ /* FIXME: Use uleb128 rather than data2. */
+ dw2_asm_output_addr (2, a->dw_attr_val.v.val_symbolic_view, "%s",
name);
+ break;
+
case dw_val_class_const_implicit:
if (flag_debug_asm)
fprintf (asm_out_file, "\t\t\t%s %s ("
@@ -23809,7 +23847,7 @@ add_high_low_attributes (tree stmt, dw_die_ref die)
indirecting them through a table might make things
easier, but even that would be more wasteful,
space-wise, than what we have now. */
- add_AT_lbl_id (die, DW_AT_GNU_entry_view, label);
+ add_AT_symview (die, DW_AT_GNU_entry_view, label);
}
}
diff --git a/gcc/dwarf2out.h b/gcc/dwarf2out.h
index a1856a5185e2..f2240af85375 100644
--- a/gcc/dwarf2out.h
+++ b/gcc/dwarf2out.h
@@ -161,7 +161,8 @@ enum dw_val_class
dw_val_class_const_implicit,
dw_val_class_unsigned_const_implicit,
dw_val_class_file_implicit,
- dw_val_class_view_list
+ dw_val_class_view_list,
+ dw_val_class_symview
};
/* Describe a floating point constant value, or a vector constant value. */
@@ -209,6 +210,7 @@ struct GTY(()) dw_val_node {
HOST_WIDE_INT GTY ((default)) val_int;
unsigned HOST_WIDE_INT
GTY ((tag ("dw_val_class_unsigned_const"))) val_unsigned;
+ char * GTY ((tag ("dw_val_class_symview"))) val_symbolic_view;
double_int GTY ((tag ("dw_val_class_const_double"))) val_double;
wide_int_ptr GTY ((tag ("dw_val_class_wide_int"))) val_wide;
dw_vec_const GTY ((tag ("dw_val_class_vec"))) val_vec;
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer
