simplify c++ memory models; support +dramsim flag

works for both vlsi and emulator

csrc/mm_dramsim2.h

@@ -0,0 +1,50 @@
+#ifndef _MM_EMULATOR_DRAMSIM2_H
+#define _MM_EMULATOR_DRAMSIM2_H
+
+#include "mm.h"
+#include <DRAMSim.h>
+#include <map>
+#include <queue>
+#include <stdint.h>
+
+class mm_dramsim2_t : public mm_t
+{
+ public:
+  mm_dramsim2_t() : store_inflight(false), store_count(0) {}
+
+  virtual void init(size_t sz);
+
+  virtual bool req_cmd_ready() { return mem->willAcceptTransaction() && !store_inflight; }
+  virtual bool req_data_ready() { return mem->willAcceptTransaction() && store_inflight; }
+  virtual bool resp_valid() { return !resp.empty(); }
+  virtual uint64_t resp_tag() { return resp_valid() ? resp.front().first : 0; }
+  virtual void* resp_data() { return resp_valid() ? &resp.front().second[0] : &dummy_data[0]; }
+
+  virtual void tick
+  (
+    bool req_cmd_val,
+    bool req_cmd_store,
+    uint64_t req_cmd_addr,
+    uint64_t req_cmd_tag,
+    bool req_data_val,
+    void* req_data_bits
+  );
+
+
+ protected:
+  DRAMSim::MultiChannelMemorySystem *mem;
+  uint64_t cycle;
+
+  bool store_inflight;
+  int store_count;
+  uint64_t store_addr;
+  std::vector<char> dummy_data;
+
+  std::map<uint64_t,uint64_t> req;
+  std::queue<std::pair<uint64_t, std::vector<char>>> resp;
+
+  void read_complete(unsigned id, uint64_t address, uint64_t clock_cycle);
+  void write_complete(unsigned id, uint64_t address, uint64_t clock_cycle);
+};
+
+#endif