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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/3713] Pointers to functions or member functions are not folded or inlined
Date: Wed, 16 Jan 2013 14:21:00 -0000
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X-Bugzilla-Component: tree-optimization
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: hubicka at gcc dot gnu.org
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3713

--- Comment #31 from Jan Hubicka <hubicka at gcc dot gnu.org> 2013-01-16 14:20:46 UTC ---
Well, after early optimizations we get:
int main() ()
{
  struct Foo x;
  void Foo::<T392> (const struct Foo *) * iftmp.0;
  long int _3;
  long int _4;
  int (*__vtbl_ptr_type) () * _5;
  long int _6;
  sizetype _7;
  int (*__vtbl_ptr_type) () * _8;

  <bb 2>:
  _3 = (long int) Bar;
  _4 = _3 & 1;
  if (_4 == 0)
    goto <bb 4>;
  else
    goto <bb 3>;

  <bb 3>:
  _5 = MEM[(int (*__vtbl_ptr_type) () * *)&x];

that is only later, at ccp2 times turned int
int main() ()
{
  struct Foo x;
  long int _3;

  <bb 2>:
  _3 = (long int) Bar;
  Foo::Bar (&x);
  x ={v} {CLOBBER};
  return 0;

}

ccp1 s not able to do this because it still sees:
int main() ()
{
  struct
  {
    void Foo::<T392> (const struct Foo *) * __pfn;
    long int __delta;
  } y;
  struct Foo x;
  void Foo::<T392> (const struct Foo *) * iftmp.0;
  void Foo::<T392> (const struct Foo *) * _5;
  long int _6;
  long int _7;
  long int _9;
  sizetype _10;
  struct Foo * _11;
  int (*__vtbl_ptr_type) () * _12;
  void Foo::<T392> (const struct Foo *) * _13;
  long int _14;
  long int _15;
  sizetype _16;
  int (*__vtbl_ptr_type) () * _17;
  long int _19;
  sizetype _20;
  const struct Foo * _21;

  <bb 2>:
  y.__pfn = Bar;
  y.__delta = 0;
  _5 = y.__pfn;
  _6 = (long int) _5;
  _7 = _6 & 1;
  if (_7 == 0)
    goto <bb 3>;
  else
    goto <bb 4>;

This is fixed by SRA to:
  <bb 2>:
  y$__pfn_4 = Bar;
  y$__delta_3 = 0;
  _5 = y$__pfn_4;
  _6 = (long int) _5;
  _7 = _6 & 1;
  if (_7 == 0)
    goto <bb 3>;
  else
    goto <bb 4>;

  <bb 3>:
  iftmp.0_8 = y$__pfn_4;

Richi, is there chance for subsequent FRE to catch this?