[Bug tree-optimization/108133] New: Failure to merge conditional bit clears

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108133

            Bug ID: 108133
           Summary: Failure to merge conditional bit clears
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

void foo (int *p)
{
  if (*p & (1<<3))
    *p &= ~(1<<3);
  if (*p & (1<<5))
    *p &= ~(1<<5);
  if (*p & (1<<6))
    *p &= ~(1<<6);
}

could be optimized to

  if (*p & ((1<<3)|(1<<5)|(1<<6)))
    *p &= ~((1<<3)|(1<<5)|(1<<6));

We have such code in tree-inline.cc:

      /* Clear flags that need revisiting.  */
      if (gcall *call_stmt = dyn_cast <gcall *> (copy))
        {
          if (gimple_call_tail_p (call_stmt))
            gimple_call_set_tail (call_stmt, false);
          if (gimple_call_from_thunk_p (call_stmt))
            gimple_call_set_from_thunk (call_stmt, false);