On Tue, 25 Sep 2018, Richard Biener wrote:
>
> This gets rid of 99% of the useless late DIE to early DIE forwarders
> (those which do not have any attributes besides the
> DW_AT_abstract_origin). I've wanted to do this for a long time but
> only now was able to verify that creating the concrete instances
> lazily in lookup_decl_die and friend works.
>
> So the patch replaces BLOCK_DIE uses in dwarf2out.c with lookup_block_die
> and equate_block_to_die "forwarders" that do the lazy concrete instance
> DIE creation and adjusts lookup_decl_die accordingly. It then switches
> dwarf2out_register_external_die to populate a decl -> { symbol, offset }
> map rather than using DIEs for the recording (and adjusts
> dwarf2out_die_ref_for_decl to look into that map in WPA phase).
>
> The rest of the patch deals with cases where we are outputting references
> to DIEs and replaces existing hacks with easier querying of the new map.
> It also makes sure to output DW_TAG_imported_unit DIEs first rather than
> spread over the DIE tree and consistently so.
>
> LTO bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
>
> I do consider backporting this given it makes the debug info so much
> easier to read (actual size only shriks by about 10%). A backport of
> the patch passed LTO bootstrap and regtest but I'll leave this on
> trunk for a while to spot issues.
>
> I said 99% above because I did spot some stray remains when digging
> through cc1 debug info. Have to see if I can easily debug that.
The following gets rid of the remaining issues (also fixing a mistake
I made with DW_TAG_imported_unit which is now created over and over
again). It also does a few simplifications where possible.
LTO bootstrap and regtest in progress on x86_64-unknown-linux-gnu.
Richard.
2018-09-25 Richard Biener <rguent...@suse.de>
PR debug/83941
* dwarf2out.c (add_AT_external_die_ref): Remove now redundant
GC-ification.
(maybe_create_die_with_external_ref): Do not create
DW_TAG_imported_unit here.
(add_abstract_origin_attribute): Handle external BLOCK refs.
(dwarf2out_abstract_function): Simplify LTO case.
(dwarf2out_early_finish): Create DW_TAG_imported_unit explicitely
rather than using maybe_create_die_with_external_ref.
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c (revision 264564)
+++ gcc/dwarf2out.c (working copy)
@@ -5868,7 +5868,7 @@ add_AT_external_die_ref (dw_die_ref die,
/* ??? We probably want to share these, thus put a ref to the DIE
we create here to the external_die_map entry. */
dw_die_ref ref = new_die_raw (die->die_tag);
- ref->die_id.die_symbol = IDENTIFIER_POINTER (get_identifier (symbol));
+ ref->die_id.die_symbol = symbol;
ref->die_offset = offset;
ref->with_offset = 1;
add_AT_die_ref (die, attr_kind, ref);
@@ -5966,8 +5966,6 @@ maybe_create_die_with_external_ref (tree
case TRANSLATION_UNIT_DECL:
{
die = comp_unit_die ();
- dw_die_ref import = new_die (DW_TAG_imported_unit, die, NULL_TREE);
- add_AT_external_die_ref (import, DW_AT_import, sym, off);
/* We re-target all CU decls to the LTRANS CU DIE, so no need
to create a DIE for the original CUs. */
return die;
@@ -21134,19 +21132,21 @@ add_abstract_origin_attribute (dw_die_re
{
dw_die_ref origin_die = NULL;
- if (DECL_P (origin))
+ /* For late LTO debug output we want to refer directly to the abstract
+ DIE in the early debug rather to the possibly existing concrete
+ instance and avoid creating that just for this purpose. */
+ sym_off_pair *desc;
+ if (in_lto_p
+ && external_die_map
+ && (desc = external_die_map->get (origin)))
{
- sym_off_pair *desc;
- if (in_lto_p
- && external_die_map
- && (desc = external_die_map->get (origin)))
- {
- add_AT_external_die_ref (die, DW_AT_abstract_origin,
- desc->sym, desc->off);
- return;
- }
- origin_die = lookup_decl_die (origin);
+ add_AT_external_die_ref (die, DW_AT_abstract_origin,
+ desc->sym, desc->off);
+ return;
}
+
+ if (DECL_P (origin))
+ origin_die = lookup_decl_die (origin);
else if (TYPE_P (origin))
origin_die = lookup_type_die (origin);
else if (TREE_CODE (origin) == BLOCK)
@@ -22458,21 +22458,15 @@ dwarf2out_abstract_function (tree decl)
if (DECL_IGNORED_P (decl))
return;
- /* Do not lazily create a DIE for decl here just because we
- got called via debug_hooks->outlining_inline_function. */
- if (in_lto_p
- && external_die_map
- && external_die_map->get (decl))
+ /* In LTO we're all set. We already created abstract instances
+ early and we want to avoid creating a concrete instance of that
+ if we don't output it. */
+ if (in_lto_p)
return;
old_die = lookup_decl_die (decl);
- /* With early debug we always have an old DIE unless we are in LTO
- and the user did not compile but only link with debug. */
- if (in_lto_p && ! old_die)
- return;
gcc_assert (old_die != NULL);
- if (get_AT (old_die, DW_AT_inline)
- || get_AT (old_die, DW_AT_abstract_origin))
+ if (get_AT (old_die, DW_AT_inline))
/* We've already generated the abstract instance. */
return;
@@ -31908,7 +31910,13 @@ dwarf2out_early_finish (const char *file
unsigned i;
tree tu;
FOR_EACH_VEC_SAFE_ELT (all_translation_units, i, tu)
- maybe_create_die_with_external_ref (tu);
+ if (sym_off_pair *desc = external_die_map->get (tu))
+ {
+ dw_die_ref import = new_die (DW_TAG_imported_unit,
+ comp_unit_die (), NULL_TREE);
+ add_AT_external_die_ref (import, DW_AT_import,
+ desc->sym, desc->off);
+ }
}
early_dwarf_finished = true;
