[Bug tree-optimization/29738] Missed constant propagation into loops

["sebastian dot pop at cri dot ensmp dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #1 from sebastian dot pop at cri dot ensmp dot fr  2006-11-06 11:48 -------
Subject: Re:  Missed constant propagation into loops

I think the problem is that "i" is a global variable and thus foo is
potentially
considered as modifying "i".  Have you tried

void foo (void);
void bar (void)
{
  int i, j;
  i = 0;
  for (j = 0; j < 10000; j++)
    if (i)
      foo ();
}

This should be a simpler case that either is correctly simplified or I know
what to do for making it work.

For the original problem, why don't we propagate constants in

  #   i_3 = V_MUST_DEF <i_2>;
  i = 0;

  # NONLOCAL.6_19 = PHI <NONLOCAL.6_9(5), NONLOCAL.6_11(2)>;
  # i_18 = PHI <i_7(5), i_3(2)>;

i.e. replacing the use of i_3 with just the constant 0?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29738