[Bug tree-optimization/112857] New: Missing optimzation: fold (b + ~a) > 0 to a - b < -1

xxs_chy at outlook dot com gcc-bugzilla@gcc.gnu.org
Tue Dec 5 06:16:40 GMT 2023


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112857

            Bug ID: 112857
           Summary: Missing optimzation: fold (b + ~a) > 0 to a - b < -1
           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 link example: https://godbolt.org/z/Pba4Y164f
For c code like:


bool src(int a, int b){
    return (b + ~a) > 0;
}

can be folded to:


bool tgt(int a, int b){
    return a - b < -1;
}


But both GCC and LLVM missed it.


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