Shared memory should only be shared inside cluster

[xujuntwt95329]

In current implementation, the shared memory is shared globally, instances from different clusters shares the same memory, which is not expected behavior.

We should only share the memory inside cluster, and when new clusters are created, there should be new memory instances.

The problem is: the cluster is created during creating exec_env rather than module instance, so during instantiating there may be no cluster information.

[xujuntwt95329]

Possible solution:

Data structures:

• In WASMSharedMemNode, add one field: main_inst_wp, weak pointer to main instance
• In WASMCluster, add one field: shared_memory_wp, weak pointer to the shared MemoryInstance

Logic:

• When creating shared memory instance, store the pointer of main instance in main_inst_wp field
• When creating new cluster, if the module's memory is shared, search the WASMSharedMemNode according to the module and main_instance, and set the shared MemoryInstance to shared_memory_wp field
• Change is_sub_inst parameter of wasm_runtime_instantiate_internal to WASMCluster *cluster
  • If cluster is NULL, always create new memory instance rather than search the shared memory list.
  • If cluster is not NULL and module's memory is shared, use the cluster->shared_memory_wp directly