Optimize memory address port width in wreduce and memory_collect, not verilog front-end

2 files changed, 31 insertions, 3 deletions

diff --git a/passes/memory/memory_collect.cc b/passes/memory/memory_collect.cc
index e068ef905..ab66e3fb8 100644
--- a/passes/memory/memory_collect.cc
+++ b/passes/memory/memory_collect.cc
@@ -37,8 +37,6 @@ Cell *handle_memory(Module *module, RTLIL::Memory *memory)
 	log("Collecting $memrd, $memwr and $meminit for memory `%s' in module `%s':\n",
 			memory->name.c_str(), module->name.c_str());
 
-	int addr_bits = 0;
-
 	Const init_data(State::Sx, memory->size * memory->width);
 	SigMap sigmap(module);
 
@@ -59,16 +57,28 @@ Cell *handle_memory(Module *module, RTLIL::Memory *memory)
 	SigSpec sig_rd_data;
 	SigSpec sig_rd_en;
 
+	int addr_bits = 0;
 	std::vector<Cell*> memcells;
 
 	for (auto &cell_it : module->cells_) {
 		Cell *cell = cell_it.second;
 		if (cell->type.in("$memrd", "$memwr", "$meminit") && memory->name == cell->parameters["\\MEMID"].decode_string()) {
-			addr_bits = max(addr_bits, cell->getParam("\\ABITS").as_int());
+			SigSpec addr = sigmap(cell->getPort("\\ADDR"));
+			for (int i = 0; i < GetSize(addr); i++)
+				if (addr[i] != State::S0)
+					addr_bits = std::max(addr_bits, i+1);
 			memcells.push_back(cell);
 		}
 	}
 
+	if (memory->start_offset == 0 && addr_bits < 30 && (1 << addr_bits) < memory->size)
+		memory->size = 1 << addr_bits;
+
+	if (memory->start_offset >= 0)
+		addr_bits = std::min(addr_bits, ceil_log2(memory->size + memory->start_offset));
+
+	addr_bits = std::max(addr_bits, 1);
+
 	if (memcells.empty()) {
 		log("  no cells found. removing memory.\n");
 		return nullptr;
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index 333541eab..b2f1bea7a 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -385,6 +385,7 @@ struct WreducePass : public Pass {
 				continue;
 
 			for (auto c : module->selected_cells())
+			{
 				if (c->type.in("$reduce_and", "$reduce_or", "$reduce_xor", "$reduce_xnor", "$reduce_bool",
 						"$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt",
 						"$logic_not", "$logic_and", "$logic_or") && GetSize(c->getPort("\\Y")) > 1) {
@@ -396,6 +397,23 @@ struct WreducePass : public Pass {
 						module->connect(sig, Const(0, GetSize(sig)));
 					}
 				}
+				if (c->type.in("$memrd", "$memwr", "$meminit")) {
+					IdString memid = c->getParam("\\MEMID").decode_string();
+					RTLIL::Memory *mem = module->memories.at(memid);
+					if (mem->start_offset == 0) {
+						int cur_addrbits = c->getParam("\\ABITS").as_int();
+						int max_addrbits = ceil_log2(mem->size);
+						if (cur_addrbits > max_addrbits) {
+							log("Removed top %d address bits (of %d) from memory %s port %s.%s (%s).\n",
+									cur_addrbits-max_addrbits, cur_addrbits,
+									c->type == "$memrd" ? "read" : c->type == "$memwr" ? "write" : "init",
+									log_id(module), log_id(c), log_id(memid));
+							c->setParam("\\ABITS", max_addrbits);
+							c->setPort("\\ADDR", c->getPort("\\ADDR").extract(0, max_addrbits));
+						}
+					}
+				}
+			}
 
 			WreduceWorker worker(&config, module);
 			worker.run();