[Bug target/95439] New: Incorrect zero count check in cmpstrnsi

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95439

            Bug ID: 95439
           Summary: Incorrect zero count check in cmpstrnsi
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: hubicka at ucw dot cz, ubizjak at gmail dot com
  Target Milestone: ---
            Target: i386,x86-64

cmpstrnsi expander has

      emit_insn (gen_cmp_1 (Pmode, countreg, countreg));
      emit_insn (gen_cmpstrnqi_1 (addr1, addr2, countreg, align,
                                  operands[1], operands[2]));

to guard against zero count.  But it checks equality, not zero.