kernel/rtlil: Extract some helpers for checking memory cell types.

There will soon be more (versioned) memory cells, so handle passes that
only care if a cell is memory-related by a simple helper call instead of
a hardcoded list.

kernel/rtlil.cc

@@ -3125,6 +3125,16 @@ void RTLIL::Cell::fixup_parameters(bool set_a_signed, bool set_b_signed)
 	check();
 }
 
+bool RTLIL::Cell::has_memid() const
+{
+	return type.in(ID($memwr), ID($memrd), ID($meminit));
+}
+
+bool RTLIL::Cell::is_mem_cell() const
+{
+	return type == ID($mem) || has_memid();
+}
+
 RTLIL::SigChunk::SigChunk()
 {
 	wire = NULL;

kernel/rtlil.h

@@ -1522,6 +1522,9 @@ public:
 #ifdef WITH_PYTHON
 	static std::map<unsigned int, RTLIL::Cell*> *get_all_cells(void);
 #endif
+
+	bool has_memid() const;
+	bool is_mem_cell() const;
 };
 
 struct RTLIL::CaseRule : public RTLIL::AttrObject