The HS jtreg test gc/stringdedup/TestStringDeduplicationAgeThreshold_ZGenerational

shows this error when running with ubsan enabled :

  const double current_old_gc_time_per_bytes_freed = double(old_gc_time) / double(reclaimed_per_old_gc);
  
gc/stringdedup/TestStringDeduplicationAgeThreshold_ZGenerational.jtr

src/hotspot/share/gc/z/zDirector.cpp:491:74: runtime error: division by zero
    #0 0x7f09886401d4 in rule_major_allocation_rate src/hotspot/share/gc/z/zDirector.cpp:491
    #1 0x7f09886401d4 in start_gc src/hotspot/share/gc/z/zDirector.cpp:822
    #2 0x7f09886401d4 in ZDirector::run_thread() src/hotspot/share/gc/z/zDirector.cpp:912
    #3 0x7f098c1404e8 in ZThread::run_service() src/hotspot/share/gc/z/zThread.cpp:29
    #4 0x7f09897cac19 in ConcurrentGCThread::run() src/hotspot/share/gc/shared/concurrentGCThread.cpp:48
    #5 0x7f098bb46b0a in Thread::call_run() src/hotspot/share/runtime/thread.cpp:225
    #6 0x7f098b1a9881 in thread_native_entry src/hotspot/os/linux/os_linux.cpp:858