[SYCL] Store pointers to memory allocations instead of iterators (#3860)

Author: againull

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -940,17 +940,16 @@ pi_result _pi_queue::executeCommandList(ze_command_list_handle_t ZeCommandList,
 
       auto &Contexts = Device->Platform->Contexts;
       for (auto &Ctx : Contexts) {
-        for (auto It = Ctx->MemAllocs.begin(); It != Ctx->MemAllocs.end();
-             It++) {
-          const auto &Pair = Kernel->MemAllocs.insert(It);
+        for (auto &Elem : Ctx->MemAllocs) {
+          const auto &Pair = Kernel->MemAllocs.insert(&Elem);
           // Kernel is referencing this memory allocation from now.
           // If this memory allocation was already captured for this kernel, it
           // means that kernel is submitted several times. Increase reference
           // count only once because we release all allocations only when
           // SubmissionsCount turns to 0. We don't want to know how many times
           // allocation was retained by each submission.
           if (Pair.second)
-            It->second.RefCount++;
+            Elem.second.RefCount++;
         }
       }
       Kernel->SubmissionsCount++;

sycl/plugins/level_zero/pi_level_zero.hpp

@@ -906,30 +906,27 @@ struct _pi_kernel : _pi_object {
 
   // Hash function object for the unordered_set below.
   struct Hash {
-    size_t operator()(
-        const std::unordered_map<void *, MemAllocRecord>::iterator &It) const {
-      return std::hash<void *>()(It->first);
+    size_t operator()(const std::pair<void *const, MemAllocRecord> *P) const {
+      return std::hash<void *>()(P->first);
     }
   };
 
   // If kernel has indirect access we need to make a snapshot of all existing
   // memory allocations to defer deletion of these memory allocations to the
   // moment when kernel execution has finished.
-  // We store iterators because iterator is not invalidated by insert/delete for
-  // std::map.
-  // Why need to take a snapshot instead of just reference-counting the
-  // allocations, because picture of active allocations can change during kernel
-  // execution (new allocations can be added) and we need to know which memory
-  // allocations were retained by this kernel to release them (and don't touch
-  // new allocations) at kernel completion.
-  // Same kernel may be submitted several times and retained allocations may be
-  // different at each submission. That's why we have a set of memory
-  // allocations here and increase ref count only once even if kernel is
-  // submitted many times. We don't want to know how many times and which
-  // allocations were retained by each submission. We release all allocations
-  // in the set only when SubmissionsCount == 0.
-  std::unordered_set<std::unordered_map<void *, MemAllocRecord>::iterator, Hash>
-      MemAllocs;
+  // We store pointers to the elements because pointers are not invalidated by
+  // insert/delete for std::unordered_map (iterators are invalidated). We need
+  // to take a snapshot instead of just reference-counting the allocations,
+  // because picture of active allocations can change during kernel execution
+  // (new allocations can be added) and we need to know which memory allocations
+  // were retained by this kernel to release them (and don't touch new
+  // allocations) at kernel completion. Same kernel may be submitted several
+  // times and retained allocations may be different at each submission. That's
+  // why we have a set of memory allocations here and increase ref count only
+  // once even if kernel is submitted many times. We don't want to know how many
+  // times and which allocations were retained by each submission. We release
+  // all allocations in the set only when SubmissionsCount == 0.
+  std::unordered_set<std::pair<void *const, MemAllocRecord> *, Hash> MemAllocs;
 
   // Counter to track the number of submissions of the kernel.
   // When this value is zero, it means that kernel is not submitted for an