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* [Bug default/25398] New: CU referenced from PU
@ 2020-01-01  0:00 vries at gcc dot gnu.org
  2020-01-01  0:00 ` [Bug default/25398] " vries at gcc dot gnu.org
                   ` (5 more replies)
  0 siblings, 6 replies; 7+ messages in thread
From: vries at gcc dot gnu.org @ 2020-01-01  0:00 UTC (permalink / raw)
  To: dwz

https://sourceware.org/bugzilla/show_bug.cgi?id=25398

            Bug ID: 25398
           Summary: CU referenced from PU
           Product: dwz
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: default
          Assignee: nobody at sourceware dot org
          Reporter: vries at gcc dot gnu.org
                CC: dwz at sourceware dot org
  Target Milestone: ---

Consider the benchmark cc1.

When compiled like this:
...
$ dwz cc1 -o 1 -lnone --no-odr 
...
we find this duplicate chain:
...
duplicate chain:
 6a1a881 O 13b1049c f3237179 rounding enumeration_type (type: 6a1a4ec unsigned
int base_type)
 6a25115 O 13b1049c f3237179 rounding enumeration_type (type: 6a24dd3 unsigned
int base_type)
 6a26b99 O 13b1049c f3237179 rounding enumeration_type (type: 6a2685c unsigned
int base_type)
 6a27e84 O 13b1049c f3237179 rounding enumeration_type (type: 6a27b47 unsigned
int base_type)
 6a29495 O 13b1049c f3237179 rounding enumeration_type (type: 6a29158 unsigned
int base_type)
...

which is referencing this (very long, so abbreviated) duplicate chain:
...
duplicate chain:
 59 O ec21c4f2 ec21c4f2 unsigned int base_type
 762fa O ec21c4f2 ec21c4f2 unsigned int base_type
 7f7e7 O ec21c4f2 ec21c4f2 unsigned int base_type
 b4999 O ec21c4f2 ec21c4f2 unsigned int base_type
 ...
 6a19d58 O ec21c4f2 ec21c4f2 unsigned int base_type
 6a1a4ec O ec21c4f2 ec21c4f2 unsigned int base_type
 6a24dd3 O ec21c4f2 ec21c4f2 unsigned int base_type
...

Each of the chains is copied to a partial unit.

When we write out the die representing the first duplicate chain, we hit code
this in write_die:
...
                  if (refdt->die_dup && refdt->die_op_type_referenced)
                    {
                      if (cu == die_cu (refdt->die_dup))
                        refd = die_find_dup (refdt, refdt->die_dup, refd);
                    }
                  else if (refdt->die_dup)
                    refd = die_find_dup (refdt, refdt->die_dup, refd);
...
with refdt->die_dup && refdt->die_op_type_reference true:
...
(gdb) p /x *refdt
$5 = {
  die_offset = 0x6a1a4ec,
  die_tag = 0x24,
  die_ck_state = 0x1,
  die_op_call2_referenced = 0x0, 
  die_op_type_referenced = 0x1,    <===
  die_named_namespace = 0x0,
  die_ref_hash_computed = 0x1, 
  die_toplevel = 0x1,
  die_remove = 0x0,
  die_no_multifile = 0x0,
  die_referenced = 0x0, 
  die_intercu_referenced = 0x0,
  die_collapsed_children = 0x0,
  die_collapsed_child = 0x0, 
  die_root = 0x0,
  die_odr_state = 0x0,
  die_parent = 0x7fffb00a0bf0,
  die_child = 0x0, 
  die_sib = 0x7fffb00a0ca0,
  die_abbrev = 0x7fffb009f940,
  die_size = 0x7,
  die_ref_seen = 0x0,
  u = {
    p1 = {die_hash = 0xaf5b0d28,
          die_ref_hash = 0x7fff,
          die_hash2 = 0x28,
          die_enter = 0x0,
          die_exit = 0x1},
    p2 = {die_new_abbrev = 0x7fffaf5b0d28,
          die_new_offset = 0x28, 
          die_intracu_udata_size = 0x0}
  },
  die_dup = 0x7fffb025f5d8,    <===
  die_nextdup = 0x7fffb00dc5c0
}
...
and cu and die_cu (refdt->die_dup) being different partial units:
...
(gdb) p *cu
$6 = {
  cu_files = 0x0,
  cu_nfiles = 0,
  cu_kind = CU_PU,
  cu_next = 0x7fffaeb8bdf0,
  cu_offset = 2099, 
  cu_version = 4,
  cu_comp_dir = 0x0,
  cu_die = 0x7fffaeb8a840,
 cu_abbrev = 0x0,
  cu_new_abbrev = 0x0, 
  u1 = {
    cu_new_abbrev_owner = 0x7fffb0399ca0,
    cu_icu = 0x7fffb0399ca0
  }, 
  u2 = {
    cu_new_abbrev_offset = 5832,
    cu_largest_entry = 5832
  },
  cu_new_offset = 1244546,
  cu_chunk = 0, 
  cu_intracu_form = DW_FORM_ref_udata,
  initial_intracusize = 2,
  lang = 0
}
(gdb) p *die_cu (refdt->die_dup)
$7 = {
  cu_files = 0x0,
  cu_nfiles = 0,
  cu_kind = CU_PU,
  cu_next = 0x7fffb025f630,
  cu_offset = 1, 
  cu_version = 4,
  cu_comp_dir = 0x0,
  cu_die = 0x7fffb025f580,
  cu_abbrev = 0x0,
  cu_new_abbrev = 0x0, 
  u1 = {
    cu_new_abbrev_owner = 0x7fffb042a200,
    cu_icu = 0x7fffb042a200
  },
  u2 = {
    cu_new_abbrev_offset = 9661,
    cu_largest_entry = 9661
  },
  cu_new_offset = 28,
  cu_chunk = 0, 
  cu_intracu_form = DW_FORM_ref_udata,
  initial_intracusize = 1,
  lang = 0
}
...
so, the die_find_dup is not applied.

This results in this DIE in a PU:
...
 <0><12fd8d>: Abbrev Number: 11 (DW_TAG_partial_unit)
 ...
 <1><12fd9b>: Abbrev Number: 7 (DW_TAG_enumeration_type)
    <12fd9c>   DW_AT_name        : rounding
    <12fda0>   DW_AT_encoding    : 7    (unsigned)
    <12fda1>   DW_AT_byte_size   : 4
    <12fda2>   DW_AT_type        : <0x3a81757>
    <12fda6>   DW_AT_decl_file   : 10
    <12fda7>   DW_AT_decl_line   : 69
    <12fda8>   DW_AT_decl_column : 8
    <12fda9>   DW_AT_sibling     : <0x12fde1>
...
referring to this DIE in a CU:
...
 <0><3a8173a>: Abbrev Number: 41 (DW_TAG_compile_unit)
    <3a81740>   DW_AT_name        : ../../libdecnumber/decNumber.c
    ...
 <1><3a81757>: Abbrev Number: 27 (DW_TAG_base_type)
    <3a81758>   DW_AT_byte_size   : 4
    <3a81759>   DW_AT_encoding    : 7   (unsigned)
    <3a8175a>   DW_AT_name        : unsigned int
...

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^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-03-02  7:59 UTC | newest]

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-- links below jump to the message on this page --
2020-01-01  0:00 [Bug default/25398] New: CU referenced from PU vries at gcc dot gnu.org
2020-01-01  0:00 ` [Bug default/25398] " vries at gcc dot gnu.org
2020-01-01  0:00 ` vries at gcc dot gnu.org
2020-01-01  0:00 ` vries at gcc dot gnu.org
2020-01-01  0:00 ` [Bug default/25398] [dwz, fixed-needs-testcase] " vries at gcc dot gnu.org
2021-02-25 14:50 ` vries at gcc dot gnu.org
2021-03-02  7:59 ` vries at gcc dot gnu.org

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