[Bug middle-end/19430] taking address of a var causes missing uninitialized warning (virtual PHI with MEM)

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19430

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2005-05-03 18:04:44         |2022-8-29

--- Comment #37 from Richard Biener <rguenth at gcc dot gnu.org> ---
Re-confirmed for the original testcase.  The issue is that while we now try to
perform uninitialized diagnostics for memory we do not perform the maybe-uninit
analysis via PHIs we do for non-memory.  We see

  <bb 2> [local count: 1073741824]:
  # .MEM_5 = VDEF <.MEM_3(D)>
  _1 = bar (i_4(D));
  if (_1 != 0)
    goto <bb 3>; [33.00%]
  else
    goto <bb 5>; [67.00%]

  <bb 5> [local count: 719407024]:
  goto <bb 4>; [100.00%]

  <bb 3> [local count: 354334800]:
  # .MEM_6 = VDEF <.MEM_5>
  baz (&j);

  <bb 4> [local count: 1073741824]:
  # .MEM_2 = PHI <.MEM_5(5), .MEM_6(3)>
  # VUSE <.MEM_2>
  _7 = j;

so when we are walking and looking for defs of 'j' by means of
walk_aliased_vdefs but that will simply process MEM_6 "unordered"
and record that as possible definition.  We are not properly forking
the walk to discover a path where 'j' is not initialized nor are
we trying to compute predicates which guard the use.

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