Also support several images for elf

[jklinkenberg]

Summary

In revision r336569 (D49036) libomptarget support for multiple nvidia images has been fixed in case a target region resides inside one or multiple libraries and in the compiled application. But the issues was still present for elf images.
This fix will also support multiple images for elf.

[ABataev]

LG

[protze.joachim]

The change is symetric with what is implemented for cuda.
LGTM

[grokos]

LGTM

openmp/trunk/libomptarget/plugins/generic-elf-64bit/src/rtl.cpp

 
 /// Keep entries table per device.
 struct FuncOrGblEntryTy {
   __tgt_target_table Table;
 };
 
 /// Class containing all the device information.
 class RTLDeviceInfoTy {
-  std::vector<FuncOrGblEntryTy> FuncGblEntries;
+  std::vector<std::list<FuncOrGblEntryTy>> FuncGblEntries;
 
 public:
   std::list<DynLibTy> DynLibs;
 
   // Record entry point associated with device.
   void createOffloadTable(int32_t device_id, __tgt_offload_entry *begin,
                           __tgt_offload_entry *end) {
     assert(device_id < (int32_t)FuncGblEntries.size() &&
            "Unexpected device id!");
-    FuncOrGblEntryTy &E = FuncGblEntries[device_id];
+    FuncGblEntries[device_id].emplace_back();
+    FuncOrGblEntryTy &E = FuncGblEntries[device_id].back();
 
     E.Table.EntriesBegin = begin;
     E.Table.EntriesEnd = end;
   }
 
   // Return true if the entry is associated with device.
   bool findOffloadEntry(int32_t device_id, void *addr) {
     assert(device_id < (int32_t)FuncGblEntries.size() &&
            "Unexpected device id!");
-    FuncOrGblEntryTy &E = FuncGblEntries[device_id];
+    FuncOrGblEntryTy &E = FuncGblEntries[device_id].back();
 
     for (__tgt_offload_entry *i = E.Table.EntriesBegin, *e = E.Table.EntriesEnd;
          i < e; ++i) {
       if (i->addr == addr)
         return true;
     }
 
     return false;
   }
 
   // Return the pointer to the target entries table.
   __tgt_target_table *getOffloadEntriesTable(int32_t device_id) {
     assert(device_id < (int32_t)FuncGblEntries.size() &&
            "Unexpected device id!");
-    FuncOrGblEntryTy &E = FuncGblEntries[device_id];
+    FuncOrGblEntryTy &E = FuncGblEntries[device_id].back();
 
     return &E.Table;
   }
 
   RTLDeviceInfoTy(int32_t num_devices) {
 #ifdef OMPTARGET_DEBUG
     if (char *envStr = getenv("LIBOMPTARGET_DEBUG")) {
       DebugLevel = std::stoi(envStr);