[Bug tree-optimization/60165] "may be used uninitialized" warning with -O3 but not with -O2

[vincent-gcc at vinc17 dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60165

--- Comment #15 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Manuel López-Ibáñez from comment #10)
> Now, I agree that ideally, GCC should warn for your last testcase. But I
> guess in that case inlining either doesn't happen or it happens too late, so
> GCC only sees the first case. The analysis that GCC performs are predicated
> on the transformations leading to better code, otherwise they are not
> performed. A tool for static analysis will surely inline as much as it
> could, not matter if the code is slower or larger, but this is not how GCC
> works because GCC is not a tool for static analysis.

Well, detecting uninitialized variables is equivalent to generating better
code. See the following functions. If you want to be able to remove the i == 0
test in the first one (making generated code better), you'll solve the warning
problem in the second one.

int f(void)
{
  int i = 0;
  /* some code that sets i to a nonzero value, but difficult to prove */
  if (i == 0)
    abort();
  return i;
}

int f(void)
{
  int i;
  /* some code that sets i to a nonzero value, but difficult to prove */
  return i;
}