[Bug tree-optimization/112982] New: Missing optimization: fold max(b, a + 1) to b when a < b

[xxs_chy at outlook dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112982

            Bug ID: 112982
           Summary: Missing optimization: fold max(b, a + 1) to b when a <
                    b
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xxs_chy at outlook dot com
  Target Milestone: ---

Godbolt example: https://godbolt.org/z/nn8hT16Ka

long src(long a, long b) {
    if(a < b){
        return max(b, a + 1);
    }else{
        return 0;
    }
}

can be folded to:

long tgt(long a, long b) {
    if(a < b){
        return b;
    }else{
        return 0;
    }
}

Similarly, such pattern can be generalized to `a > b`, `min(b, a + 1)`.
Both GCC and LLVM missed such optimization opportunity.