Handle missing initializers in allocation planner to fix crashes with…

… DML provider (#5244)

* Fix memory planning bug with DML EP

* Address PR comments

* Fix typo

onnxruntime/core/framework/allocation_planner.cc

@@ -144,7 +144,13 @@ class PlannerImpl {
   struct OrtValueInfo {
     const onnxruntime::NodeArg* p_def_site;  // the (unique) NodeArg corresponding to the MLValue
     int usecount = 0;                        // static reference-count
-    OrtValueIndex reused_buffer_index;       // index of original buffer to reuse
+
+    // This is initialized to -1 to ensure that if ProcessDef is somehow not called, planning
+    // will fail more cleanly.  This is also used as a temporary workaround to detect the
+    // case that the DML provider has removed initilizers from the graph during partitioning. 
+    // Removing initializers is a temporary measure needed to limit the number of copies of 
+    // tensors in GPU memory.
+    OrtValueIndex reused_buffer_index = -1;  // index of original buffer to reuse
   };
 
   // ort_value_info_ is indexed by an OrtValueIndex
@@ -177,6 +183,12 @@ class PlannerImpl {
   }
   int& UseCount(const OrtValueName& name) { return UseCount(Index(name)); }
 
+  int DecrementUseCount(OrtValueIndex n) {
+    int& use_count = --UseCount(n);
+    assert(use_count >= 0);
+    return use_count;
+  }
+
   OrtValueIndex& Buffer(OrtValueIndex n) {
     ORT_ENFORCE(n >= 0 && static_cast<size_t>(n) < ort_value_info_.size());
     return ort_value_info_[n].reused_buffer_index;
@@ -643,7 +655,9 @@ class PlannerImpl {
         if (node_input->Exists()) {
           auto& sym = node_input->Name();
           auto original = Buffer(Index(sym));
-          if (0 == --UseCount(original))
+          // The index will be -1 if it's an initializer that was removed as part of a temporary workaround.
+          // See comments in the OrtValueInfo definition.
+          if ((original != -1) && (0 == DecrementUseCount(original)))
             freelist_.push_front(FreeBufferInfo(original, program_counter));
         }
       }
@@ -652,7 +666,9 @@ class PlannerImpl {
         if (node_input->Exists()) {
           auto& sym = node_input->Name();
           auto original = Buffer(Index(sym));
-          if (0 == --UseCount(original))
+          // The index will be -1 if it's an initializer that was removed as part of a temporary workaround.
+          // See comments in the OrtValueInfo definition.
+          if ((original != -1) && (0 == DecrementUseCount(original)))
             freelist_.push_front(FreeBufferInfo(original, program_counter));
         }
       }
@@ -662,7 +678,7 @@ class PlannerImpl {
         if (node_output->Exists()) {
           auto& sym = node_output->Name();
           auto original = Buffer(Index(sym));
-          if (0 == --UseCount(original))
+          if (0 == DecrementUseCount(original))
             freelist_.push_front(FreeBufferInfo(original, program_counter));
         }
       }