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[PATCH] Emit DW_AT_data_bit_offset instead of DW_AT_{data_member_location,bit_offset,byte_size} for -gdwarf-5 (PR debug/71669)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org, Jan Kratochvil <jkratoch at redhat dot com>
- Date: Thu, 12 Jan 2017 21:27:54 +0100
- Subject: [PATCH] Emit DW_AT_data_bit_offset instead of DW_AT_{data_member_location,bit_offset,byte_size} for -gdwarf-5 (PR debug/71669)
- Authentication-results: sourceware.org; auth=none
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
While DW_AT_data_bit_offset has been introduced already in DWARF4, GDB only
gained support for it last November, so I think it is better to enable this
only for -gdwarf-5 for now and we can reconsider it in a year or two.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2017-01-12 Jakub Jelinek <jakub@redhat.com>
PR debug/71669
* dwarf2out.c (add_data_member_location_attribute): For constant
offset bitfield emit for -gdwarf-5 DW_AT_data_bit_offset attribute
instead of DW_AT_data_member_location, DW_AT_bit_offset and
DW_AT_byte_size attributes.
--- gcc/dwarf2out.c.jj 2017-01-11 19:05:15.000000000 +0100
+++ gcc/dwarf2out.c 2017-01-12 15:08:29.842773537 +0100
@@ -18272,6 +18272,23 @@ add_data_member_location_attribute (dw_d
if (! loc_descr)
{
+ /* While DW_AT_data_bit_offset has been added already in DWARF4,
+ e.g. GDB only added support to it in November 2016. For DWARF5
+ we need newer debug info consumers anyway. We might change this
+ to dwarf_version >= 4 once most consumers catched up. */
+ if (dwarf_version >= 5
+ && TREE_CODE (decl) == FIELD_DECL
+ && DECL_BIT_FIELD_TYPE (decl))
+ {
+ tree off = bit_position (decl);
+ if (tree_fits_uhwi_p (off) && get_AT (die, DW_AT_bit_size))
+ {
+ remove_AT (die, DW_AT_byte_size);
+ remove_AT (die, DW_AT_bit_offset);
+ add_AT_unsigned (die, DW_AT_data_bit_offset, tree_to_uhwi (off));
+ return;
+ }
+ }
if (dwarf_version > 2)
{
/* Don't need to output a location expression, just the constant. */
Jakub