Fix persistable var is GC as unexpected (#36932)

* Fix persistable var is GC as unexpected

* polish code and rebase develop

paddle/fluid/framework/new_executor/interpretercore.cc

@@ -502,11 +502,11 @@ void InterpreterCore::CheckGC(const Instruction& instr) {
   for (auto var_id : instr.GCCheckVars()) {
     bool is_ready =
         atomic_var_ref[var_id]->fetch_sub(1, std::memory_order_relaxed) == 1;
-    if (is_ready && var_scope.VarDesc(var_id) &&
-        !var_scope.VarDesc(var_id)->Persistable()) {
-      gc_.Add(var_scope.Var(var_id), gc_event_.at(instr_id),
-              &instr.DeviceContext());
-    } else if (is_ready && var_scope.VarDesc(var_id) == nullptr) {
+    // ignore all persistable var while GC
+    if (var_scope.VarDesc(var_id) && var_scope.VarDesc(var_id)->Persistable()) {
+      continue;
+    }
+    if (is_ready) {
       gc_.Add(var_scope.Var(var_id), gc_event_.at(instr_id),
               &instr.DeviceContext());
     }

paddle/fluid/framework/new_executor/interpretercore_util.cc

@@ -146,7 +146,7 @@ void build_variable_scope(const framework::ProgramDesc& pdesc,
       if (nullptr == var_desc_tmp) {
         VLOG(3) << "update var:" << var_name << " desc from nullptr into "
                 << var_desc;
-        var_scope->VarMetaInfo(var_name).vardesc_ = var_desc;
+        var_scope->SetVarDesc(var_name, var_desc);
       }
     }
   }

paddle/fluid/framework/new_executor/new_executor_defs.h

@@ -564,6 +564,11 @@ class VariableScope : public ScopeBase {
     vec_meta_info_.push_back(info);
   }
 
+  void SetVarDesc(const std::string& name, framework::VarDesc* var_desc) {
+    CheckExist(name);
+    vec_meta_info_[VarId(name)].vardesc_ = var_desc;
+  }
+
   paddle::framework::VarDesc* VarDesc(const std::string& name) const {
     return VarDesc(VarId(name));
   }
@@ -573,10 +578,6 @@ class VariableScope : public ScopeBase {
     return vec_meta_info_[id].vardesc_;
   }
 
-  VariableMetaInfo& VarMetaInfo(const std::string& name) {
-    return vec_meta_info_[VarId(name)];
-  }
-
   void CheckExist(int id) const {
     PADDLE_ENFORCE_LT(id, var_list_.size(),
                       platform::errors::PreconditionNotMet(