[Bug tree-optimization/87287] New: Move signed (x % pow2) == 0 optimization to gimple

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87287

            Bug ID: 87287
           Summary: Move signed (x % pow2) == 0 optimization to gimple
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

As can be seen on:

void f0 (void);

int
f1 (int x)
{
  return x % 16 == 0;
}

int
f2 (int x)
{
  int y = x % 16;
  return y != 0;
}

void
f3 (int x)
{
  if (x % 16 != 0)
    f0 ();
}

void
f4 (int x)
{
  int y = x % 16;
  if (y == 0)
    f0 ();
}

we perform this optimization in fold-const.c only, it should be moved to
match.pd.