[Bug middle-end/50741] [4.7 Regression] remove_unused_locals causes seg fault

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50741

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |jakub at gcc dot gnu.org

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-10-18 
11:00:49 UTC ---
Bootstraps and tests ok.  But I suppose with BLOCK_NONLOCAL_VARS we could
refer to an inlined functions static vars, and their initializer could refer
to static vars from the inlined function that are otherwise unused.

int foo()
{
  static volatile int i;
  static volatile int * volatile p = &i;
  return *p;
}

int bar()
{
  return foo();
}

when foo is inlined into bar.  And indeed with the patch we get

{ Scope block 0x7ffff5b3ac30#0

  { Scope block 0x7ffff5b950a0#2 t.c:10 Originating from :  static intD.6
fooD.1604 ();

    { Scope block 0x7ffff5b950f0#3 Originating from : 0x7ffff5b3ab90#0
      static volatile intD.6 i.1606D.1606; (nonlocalized)
      static volatile intD.6 * volatile p.1607D.1607 = &i.1606D.1606;
(nonlocalized)

    }

  }

}
bar ()
{
  volatile intD.6 * volatile p.0D.2736;
  intD.6 D.2735;

  # BLOCK 2 freq:10000
  # PRED: ENTRY [100.0%]  (fallthru,exec)
  # VUSE <.MEMD.2734_2(D)>
  # PT = nonlocal escaped
  p.0D.2736_4 ={v} p.1607D.1607;
  # VUSE <.MEMD.2734_2(D)>
  D.2735_5 ={v} *p.0D.2736_4;
  # VUSE <.MEMD.2734_2(D)>
  return D.2735_5;

while without we get

Scope blocks after cleanups:

{ Scope block 0x7ffff5b3ac30#0

  { Scope block 0x7ffff5b950a0#2 t.c:10 Originating from :  static intD.6
fooD.1604 ();

    { Scope block 0x7ffff5b950f0#3 Originating from : 0x7ffff5b3ab90#0
      static volatile intD.6 i.1606D.1606; (nonlocalized)
      static volatile intD.6 * volatile p.1607D.1607 = &i.1606D.1606;
(nonlocalized)

    }

  }

bar ()
{
  volatile intD.6 * volatile p.0D.2736;
  static volatile intD.6 iD.1606;
  static volatile intD.6 * volatile p.1607D.1607 = &iD.1606;
  intD.6 D.2735;
  static volatile intD.6 * volatile p.1607D.1607 = &iD.1606;
  static volatile intD.6 iD.1606;

  # BLOCK 2 freq:10000
  # PRED: ENTRY [100.0%]  (fallthru,exec)
  # VUSE <.MEMD.2734_2(D)>
  # PT = nonlocal escaped
  p.0D.2736_4 ={v} p.1607D.1607;
  # VUSE <.MEMD.2734_2(D)>
  D.2735_5 ={v} *p.0D.2736_4;
  # VUSE <.MEMD.2734_2(D)>
  return D.2735_5;
  # SUCC: EXIT [100.0%]

so there is a difference in what local_decls contains.  Not sure if that
is important though.