[Bug tree-optimization/98299] New: Failure to optimize sub loop into modulo-based pattern

[gabravier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98299

            Bug ID: 98299
           Summary: Failure to optimize sub loop into modulo-based pattern
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

int f1(int n)
{
    while (n >= 45)
        n -= 45;

    return n;
}

This can be optimized into a modulo-based pattern, for example this :

int f2(int n)
{
    int tmp = n > 44 ? n : 44;
    return ((tmp % 45) - tmp) + n;
}

This transformation is done by LLVM, but not by GCC.