[Bug libfortran/79956] [7 Regression] many new -Wmaybe-uninitialized warnings with bootstrap-O3

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956

--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 8 Mar 2017, trippels at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79956
> 
> --- Comment #3 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
> Testcase that only warns with -O3

It also warns with -O1 and -Os (but not -O2).  At -O2 the function is
optimized to just

fn1 ()
{
  int n;
  int d[1];

  <bb 2> [0.01%]:
  c = 1;

  <bb 3> [100.00%]:
  goto <bb 3>; [100.00%]
}

at -O3 we have peeled one iteration and are left with

fn1 ()
{
  int n;
  int d[1];
  int b.1_1;
  int _2;

  <bb 2> [0.01%]:
  n_4 = a;
  c = 1;
  _2 = d[0];
  b.1_1 = b;
  goto <bb 4>; [100.00%]
... (similar to above)

Note the testcase doesnt' capture the specific case of a bogus
warning as it is in parity_l8.