functional backend: make Memory in the C++ simulation library read-on…

…ly again

backends/functional/cxx.cc

@@ -156,6 +156,14 @@ template<class NodePrinter> struct CxxPrintVisitor : public FunctionalIR::Abstra
 	void memory_write(Node, Node mem, Node addr, Node data) override { print("{}.write({}, {})", mem, addr, data); }
 };
 
+bool equal_def(RTLIL::Const const &a, RTLIL::Const const &b) {
+	if(a.size() != b.size()) return false;
+	for(int i = 0; i < a.size(); i++)
+		if((a[i] == State::S1) != (b[i] == State::S1))
+			return false;
+	return true;
+}
+
 struct CxxModule {
 	FunctionalIR ir;
 	CxxStruct input_struct, output_struct, state_struct;
@@ -193,11 +201,16 @@ struct CxxModule {
 			if (sort.is_signal())
 				f.print("\tstate.{} = {};\n", state_struct[name], cxx_const(ir.get_initial_state_signal(name)));
 			else if (sort.is_memory()) {
+				f.print("\t{{\n");
+				f.print("\t\tstd::array<Signal<{}>, {}> mem;\n", sort.data_width(), 1<<sort.addr_width());
 				const auto &contents = ir.get_initial_state_memory(name);
-				f.print("\tstate.{}.fill({});\n", state_struct[name], cxx_const(contents.default_value()));
+				f.print("\t\tmem.fill({});\n", cxx_const(contents.default_value()));
 				for(auto range : contents)
 					for(auto addr = range.base(); addr < range.limit(); addr++)
-						f.print("\tstate.{}[{}] = {};\n", state_struct[name], addr, cxx_const(range[addr]));
+						if(!equal_def(range[addr], contents.default_value()))
+							f.print("\t\tmem[{}] = {};\n", addr, cxx_const(range[addr]));
+				f.print("\t\tstate.{} = mem;\n", state_struct[name]);
+				f.print("\t}}\n");
 			}
 		}
 		f.print("}}\n\n");

backends/functional/cxx_runtime/sim.h

@@ -400,6 +400,8 @@ template<size_t a, size_t d>
 class Memory {
     std::array<Signal<d>, 1<<a> _contents;
 public:
+    Memory() {}
+    Memory(std::array<Signal<d>, 1<<a> const &contents) : _contents(contents) {}
     Signal<d> read(Signal<a> addr) const
     {
         return _contents[addr.template as_numeric<size_t>()];
@@ -410,9 +412,6 @@ class Memory {
         ret._contents[addr.template as_numeric<size_t>()] = data;
         return ret;
     }
-    // mutating methods for initializing a state
-    void fill(Signal<d> data) { _contents.fill(data); }
-    Signal<d> &operator[](Signal<a> addr) { return _contents[addr.template as_numeric<size_t>()]; }
 };
 
 #endif