[OpenMP] Target memory allocator fallback to default when no device available

[jdoerfert]

LG

openmp/runtime/src/i18n/en_US.txt

 StgDeprecatedValue           "%1$s: \"%2$s\" value is deprecated. Please use \"%3$s\" instead."
 NumTeamsNotPositive          "num_teams value must be positive, it is %1$d, using %2$d instead."
 AffHWSubsetIncompat          "KMP_HW_SUBSET ignored: %1$s, %2$s: attributes are ambiguous, please only specify one."
 AffHWSubsetAttrRepeat        "KMP_HW_SUBSET ignored: %1$s: attribute specified more than once."
 AffHWSubsetAttrInvalid       "KMP_HW_SUBSET ignored: %1$s: attribute value %2$s is invalid."
 AffHWSubsetAllFiltered       "KMP_HW_SUBSET ignored: all hardware resources would be filtered, please reduce the filter."
 AffHWSubsetAttrsNonHybrid    "KMP_HW_SUBSET ignored: Too many attributes specified. This machine is not a hybrid architecutre."
 AffHWSubsetIgnoringAttr      "KMP_HW_SUBSET: ignoring %1$s attribute. This machine is not a hybrid architecutre."
+TargetMemNotAvailable        "Target memory not available, will use default allocator."
 
 # --------------------------------------------------------------------------------------------------
 -*- HINTS -*-
 # --------------------------------------------------------------------------------------------------
 
 # Hints. Hint may be printed after a message. Usually it is longer explanation text or suggestion.
 # To maintain hint numbers (they are visible to customers), add new hints to the end.
 

openmp/runtime/src/kmp_alloc.cpp

if (__kmp_target_mem_available) {
       kmp_int32 device =
           __kmp_threads[gtid]->th.th_current_task->td_icvs.default_device;
       if (allocator == llvm_omp_target_host_mem_alloc)
         ptr = kmp_target_alloc_host(size, device);
       else if (allocator == llvm_omp_target_shared_mem_alloc)
         ptr = kmp_target_alloc_shared(size, device);
       else // allocator == llvm_omp_target_device_mem_alloc
         ptr = kmp_target_alloc_device(size, device);
-    }
       return ptr;
+    } else {
+      KMP_INFORM(TargetMemNotAvailable);
+    }
   }
 
   if (allocator >= kmp_max_mem_alloc && KMP_IS_TARGET_MEM_SPACE(al->memspace)) {
     if (__kmp_target_mem_available) {
       kmp_int32 device =
           __kmp_threads[gtid]->th.th_current_task->td_icvs.default_device;
       if (al->memspace == llvm_omp_target_host_mem_space)
         ptr = kmp_target_alloc_host(size, device);
       else if (al->memspace == llvm_omp_target_shared_mem_space)
         ptr = kmp_target_alloc_shared(size, device);
       else // al->memspace == llvm_omp_target_device_mem_space
         ptr = kmp_target_alloc_device(size, device);
-    }
       return ptr;
+    } else {
+      KMP_INFORM(TargetMemNotAvailable);
+    }
   }
 
   if (__kmp_memkind_available) {
     if (allocator < kmp_max_mem_alloc) {
       // pre-defined allocator
       if (allocator == omp_high_bw_mem_alloc && mk_hbw_preferred) {
         ptr = kmp_mk_alloc(*mk_hbw_preferred, desc.size_a);
       } else if (allocator == omp_large_cap_mem_alloc && mk_dax_kmem_all) {