[Bug middle-end/39246] FAIL: gcc.dg/uninit-13.c

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39246

Andreas Krebbel <krebbel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |krebbel at gcc dot gnu.org

--- Comment #4 from Andreas Krebbel <krebbel at gcc dot gnu.org> 2011-02-25 14:08:20 UTC ---
I also see uninit-13.c failing on s390x.

The warning here is also emitted for line 7 while being expected in
line 8.

     4  typedef _Complex float C;
     5  C foo()
     6  {
     7    C f;
     8    __imag__ f = 0;       /* { dg-warning "is used" "unconditional" } */
     9    return f;
    10  }

The question is why do we expect the warning in line 8 at all?!  To me
it makes sense to either emit the warning on the uninitialized use -
that would be the "return f;" in line 9 or emit it for the declaration
of the uninitialized variable - that would be line 7 then.

To my understanding line 8 is the only one not directly related to the
warning.

warn_uninit in tree-ssa.c seems to implement exactly this.  It uses
either the location of the using gimple expression if available or it
falls back to the var decl. On s390x I see the var decl being used as
location while for x86_64 there is a stmt having its own location which
is used instead.

x86_64: uninit-13.c.083t.dce2:

foo ()
{
  float f$real;
  C f;

<bb 2>:
  [gcc/testsuite/gcc.dg/uninit-13.c : 8:14] f_3 = COMPLEX_EXPR <f$real_5(D),
0.0>;
  return f_3;

}



s390x: uninit-13.i.083t.dce2

foo ()
{
  float f$real;

<bb 2>:
  REALPART_EXPR <<retval>> = f$real_6(D);
  [gcc/testsuite/gcc.dg/uninit-13.c : 9:3] IMAGPART_EXPR <<retval>> = 0.0;
  [gcc/testsuite/gcc.dg/uninit-13.c : 9:3] return <retval>;

}


Before dce2 the line with the COMPLEX_EXPR exists also on s390x:

s390x: uninit-13.i.082t.reassoc1:

foo ()
{
  float f$real;
  C f;
  float D.2702;

<bb 2>:
  [gcc/testsuite/gcc.dg/uninit-13.c : 8:14] f$real_2 = f$real_6(D);
  [gcc/testsuite/gcc.dg/uninit-13.c : 8:14] f_3 = COMPLEX_EXPR <f$real_6(D),
0.0>;
  REALPART_EXPR <<retval>> = f$real_6(D);
  [gcc/testsuite/gcc.dg/uninit-13.c : 9:3] IMAGPART_EXPR <<retval>> = 0.0;
  [gcc/testsuite/gcc.dg/uninit-13.c : 9:3] return <retval>;

}

I think first we should fix the testcase - moving the warning one line
up and then find a way to fix the x86_64 problem.  To me it currently
looks like this is a testcase bug.