https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83941
Bug ID: 83941
Summary: Debug info generated with -flto contains useless
forwarders
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Keywords: lto, missed-optimization
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
Currently for
int main()
{
int i;
return 0;
}
we emit
<1><174>: Abbrev Number: 2 (DW_TAG_subprogram)
<175> DW_AT_external : 1
<175> DW_AT_name : (indirect string, offset: 0x152): main
<179> DW_AT_decl_file : 1
<17a> DW_AT_decl_line : 1
<17b> DW_AT_decl_column : 5
<17c> DW_AT_type : <0x18f>
<180> DW_AT_sibling : <0x18f>
<2><184>: Abbrev Number: 3 (DW_TAG_variable)
<185> DW_AT_name : i
<187> DW_AT_decl_file : 1
<188> DW_AT_decl_line : 3
<189> DW_AT_decl_column : 7
<18a> DW_AT_type : <0x18f>
<2><18e>: Abbrev Number: 0
<1><18f>: Abbrev Number: 4 (DW_TAG_base_type)
<190> DW_AT_byte_size : 4
<191> DW_AT_encoding : 5 (signed)
<192> DW_AT_name : int
in the early unit and
<1><1c9>: Abbrev Number: 3 (DW_TAG_subprogram)
<1ca> DW_AT_abstract_origin: <0x174>
<1ce> DW_AT_low_pc : 0x4004b6
<1d6> DW_AT_high_pc : 0x6
<1de> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<1e0> DW_AT_GNU_all_call_sites: 1
<2><1e0>: Abbrev Number: 4 (DW_TAG_variable)
<1e1> DW_AT_abstract_origin: <0x184>
in the late one. Note the "useless" DIE for 'i' which isn't necessary
to make gdb print '<optimized out>' - gdb happily picks up variables
for name lookup without the extra forwarder via the DW_TAG_subprogram
abstract origin children.
