[Bug tree-optimization/97997] Missed optimization: Multiply of extended integer cannot overflow

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97997

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
unsigned short
f1 (unsigned short x)
{
  return x * 10 / 10;
}

unsigned short
f2 (unsigned short x)
{
  int a = x;
  int b = 10;
  int c = 10;
  return a * b / c;
}

unsigned short
f3 (unsigned short x)
{
  return x * 10U / 10;
}

unsigned short
f4 (unsigned short x)
{
  unsigned a = x;
  unsigned b = 10;
  unsigned c = 10;
  return a * b / c;
}

For f1 we fold it already during generic folding, f2 we fold during ccp using
the
/* Simplify (t * 2) / 2) -> t.  */
(for div (trunc_div ceil_div floor_div round_div exact_div)
 (simplify
  (div (mult:c @0 @1) @1)
  (if (ANY_INTEGRAL_TYPE_P (type)
       && TYPE_OVERFLOW_UNDEFINED (type))
   @0)))
rule.