diff --git a/mlir/lib/Support/StorageUniquer.cpp b/mlir/lib/Support/StorageUniquer.cpp
--- a/mlir/lib/Support/StorageUniquer.cpp
+++ b/mlir/lib/Support/StorageUniquer.cpp
@@ -82,9 +82,6 @@
     /// The set containing the allocated storage instances.
     StorageTypeSet instances;
 
-    /// Allocator to use when constructing derived instances.
-    StorageAllocator allocator;
-
 #if LLVM_ENABLE_THREADS != 0
     /// A mutex to keep uniquing thread-safe.
     llvm::sys::SmartRWMutex<true> mutex;
@@ -95,11 +92,12 @@
   /// fashion.
   BaseStorage *
   getOrCreateUnsafe(Shard &shard, LookupKey &key,
-                    function_ref<BaseStorage *(StorageAllocator &)> ctorFn) {
+                    function_ref<BaseStorage *(StorageAllocator &)> ctorFn,
+                    function_ref<StorageAllocator &()> getAllocFn) {
     auto existing = shard.instances.insert_as({key.hashValue}, key);
     BaseStorage *&storage = existing.first->storage;
     if (existing.second)
-      storage = ctorFn(shard.allocator);
+      storage = ctorFn(getAllocFn());
     return storage;
   }
 
@@ -138,11 +136,12 @@
   BaseStorage *
   getOrCreate(bool threadingIsEnabled, unsigned hashValue,
               function_ref<bool(const BaseStorage *)> isEqual,
-              function_ref<BaseStorage *(StorageAllocator &)> ctorFn) {
+              function_ref<BaseStorage *(StorageAllocator &)> ctorFn,
+              function_ref<StorageAllocator &()> getAllocFn) {
     Shard &shard = getShard(hashValue);
     ParametricStorageUniquer::LookupKey lookupKey{hashValue, isEqual};
     if (!threadingIsEnabled)
-      return getOrCreateUnsafe(shard, lookupKey, ctorFn);
+      return getOrCreateUnsafe(shard, lookupKey, ctorFn, getAllocFn);
 
     // Check for a instance of this object in the local cache.
     auto localIt = localCache->insert_as({hashValue}, lookupKey);
@@ -161,19 +160,24 @@
     // Acquire a writer-lock so that we can safely create the new storage
     // instance.
     llvm::sys::SmartScopedWriter<true> typeLock(shard.mutex);
-    return localInst = getOrCreateUnsafe(shard, lookupKey, ctorFn);
+    return localInst = getOrCreateUnsafe(shard, lookupKey, ctorFn, getAllocFn);
   }
+
   /// Run a mutation function on the provided storage object in a thread-safe
   /// way.
   LogicalResult
-  mutate(bool threadingIsEnabled, BaseStorage *storage,
+  mutate(bool threadingIsEnabled, StorageAllocator &allocator,
+         BaseStorage *storage,
          function_ref<LogicalResult(StorageAllocator &)> mutationFn) {
-    Shard &shard = getShardFor(storage);
+    // Get a shard to use for mutating this storage instance. It doesn't need to
+    // be the same shard as the original allocation, but does need to be
+    // deterministic.
+    Shard &shard = getShard(llvm::hash_value(storage));
     if (!threadingIsEnabled)
-      return mutationFn(shard.allocator);
+      return mutationFn(allocator);
 
     llvm::sys::SmartScopedWriter<true> lock(shard.mutex);
-    return mutationFn(shard.allocator);
+    return mutationFn(allocator);
   }
 
 private:
@@ -197,18 +201,6 @@
     return *shard;
   }
 
-  /// Return the shard that allocated the provided storage object.
-  Shard &getShardFor(BaseStorage *storage) {
-    for (size_t i = 0; i != numShards; ++i) {
-      if (Shard *shard = shards[i].load(std::memory_order_acquire)) {
-        llvm::sys::SmartScopedReader<true> lock(shard->mutex);
-        if (shard->allocator.allocated(storage))
-          return *shard;
-      }
-    }
-    llvm_unreachable("expected storage object to have a valid shard");
-  }
-
   /// A thread local cache for storage objects. This helps to reduce the lock
   /// contention when an object already existing in the cache.
   ThreadLocalCache<StorageTypeSet> localCache;
@@ -281,8 +273,9 @@
     assert(parametricUniquers.count(id) &&
            "creating unregistered storage instance");
     ParametricStorageUniquer &storageUniquer = *parametricUniquers[id];
-    return storageUniquer.getOrCreate(threadingIsEnabled, hashValue, isEqual,
-                                      ctorFn);
+    return storageUniquer.getOrCreate(
+        threadingIsEnabled, hashValue, isEqual, ctorFn,
+        [&]() -> StorageAllocator & { return getThreadSafeAllocator(); });
   }
 
   /// Run a mutation function on the provided storage object in a thread-safe
@@ -293,7 +286,30 @@
     assert(parametricUniquers.count(id) &&
            "mutating unregistered storage instance");
     ParametricStorageUniquer &storageUniquer = *parametricUniquers[id];
-    return storageUniquer.mutate(threadingIsEnabled, storage, mutationFn);
+    return storageUniquer.mutate(threadingIsEnabled, getThreadSafeAllocator(),
+                                 storage, mutationFn);
+  }
+
+  /// Return an allocator that can be used to safely allocate instances on the
+  /// current thread.
+  StorageAllocator &getThreadSafeAllocator() {
+#if LLVM_ENABLE_THREADS != 0
+    StorageAllocator *&allocator = threadSafeAllocator.get();
+
+    // If the allocator has not been initialized, create a new one.
+    if (!allocator) {
+      allocator = new StorageAllocator();
+
+      // Record this allocator, given that we don't want it to be destroyed when
+      // the thread dies.
+      llvm::sys::SmartScopedLock<true> lock(threadAllocatorMutex);
+      threadAllocators.push_back(std::unique_ptr<StorageAllocator>(allocator));
+    }
+
+    return *allocator;
+#else
+    return allocator;
+#endif
   }
 
   //===--------------------------------------------------------------------===//
@@ -314,6 +330,18 @@
   // Instance Storage
   //===--------------------------------------------------------------------===//
 
+#if LLVM_ENABLE_THREADS != 0
+  /// A thread local set of allocators used for uniquing parametric instances,
+  /// or other data allocated in thread volatile situations.
+  ThreadLocalCache<StorageAllocator *> threadSafeAllocator;
+
+  /// All of the allocators that have been created for thread based allocation.
+  std::vector<std::unique_ptr<StorageAllocator>> threadAllocators;
+
+  /// A mutex used for safely adding a new thread allocator.
+  llvm::sys::SmartMutex<true> threadAllocatorMutex;
+#endif
+
   /// Map of type ids to the storage uniquer to use for registered objects.
   DenseMap<TypeID, std::unique_ptr<ParametricStorageUniquer>>
       parametricUniquers;
@@ -322,8 +350,9 @@
   /// singleton.
   DenseMap<TypeID, BaseStorage *> singletonInstances;
 
-  /// Allocator used for uniquing singleton instances.
-  StorageAllocator singletonAllocator;
+  /// Main allocator used for uniquing singleton instances, and other state when
+  /// thread safety is guaranteed.
+  StorageAllocator allocator;
 
   /// Flag specifying if multi-threading is enabled within the uniquer.
   bool threadingIsEnabled = true;
@@ -378,7 +407,7 @@
     TypeID id, function_ref<BaseStorage *(StorageAllocator &)> ctorFn) {
   assert(!impl->singletonInstances.count(id) &&
          "storage class already registered");
-  impl->singletonInstances.try_emplace(id, ctorFn(impl->singletonAllocator));
+  impl->singletonInstances.try_emplace(id, ctorFn(impl->allocator));
 }
 
 /// Implementation for mutating an instance of a derived storage.