Remove MemoryCaseUtil::MergeThrdMemZoneId (#4705)

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>

oneflow/core/memory/memory_case_util.cpp

@@ -76,10 +76,6 @@ bool MemoryCaseUtil::IsHostUnPinnedMemoryCase(const MemoryCase& mem_case) {
          && !mem_case.host_mem().used_by_network();
 }
 
-int64_t MemoryCaseUtil::MergeThrdMemZoneId(int64_t thrd_id, const MemoryCase& mem_case) {
-  return (thrd_id << 21) | (MemoryCaseUtil::GenMemZoneId(mem_case));
-}
-
 std::shared_ptr<MemoryCase> MemoryCaseUtil::MakeMemCase(const DeviceType device_type,
                                                         const int64_t device_id) {
   const auto& mem_case = std::make_shared<MemoryCase>();

oneflow/core/memory/memory_case_util.h

@@ -48,8 +48,6 @@ struct MemoryCaseUtil {
 
   static int64_t GenMemZoneId(const MemoryCase& mem_case);
 
-  static int64_t MergeThrdMemZoneId(int64_t thrd_id, const MemoryCase& mem_case);
-
   static bool IsHostUnPinnedMemoryCase(const MemoryCase& mem_case);
 
   static std::shared_ptr<MemoryCase> MakeMemCase(const DeviceType device_type,