[Bug middle-end/80100] New: simplify-rtx.c sanitizer detects undefined behaviour with optimization

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80100

            Bug ID: 80100
           Summary: simplify-rtx.c sanitizer detects undefined behaviour
                    with optimization
           Product: gcc
           Version: 7.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

//gcc 7.0.1 trunk 246252 undefined behaviour with optimization
//-O0 and -Og ok, higher levels get undefined
long int
f2 (long int k)
{
  return 2L | ((k - 1L) >> ((int) sizeof (long int) * __CHAR_BIT__ - 1));
}
//../../gcc-7-246252/gcc/simplify-rtx.c:2743:49: runtime error: left shift of 2
by 63 places cannot be represented in type 'long int'
//simplify-rtx.c:2743 is "HOST_WIDE_INT mask = INTVAL (trueop1) << count;