From 2c65e1abacc4401c4fd3e9b48f52c4de120bc511 Mon Sep 17 00:00:00 2001
From: Eddie Hung <eddie@fpgeh.com>
Date: Mon, 13 Jan 2020 21:45:27 -0800
Subject: [PATCH] abc9: break SCC by setting (* keep *) on output wires

---
 backends/aiger/xaiger.cc      | 23 +++++++++++++++--------
 frontends/aiger/aigerparse.cc |  4 +++-
 passes/techmap/abc9.cc        |  2 +-
 passes/techmap/abc9_ops.cc    | 29 ++++-------------------------
 4 files changed, 23 insertions(+), 35 deletions(-)

diff --git a/backends/aiger/xaiger.cc b/backends/aiger/xaiger.cc
index ed0e48e01..8651f3a01 100644
--- a/backends/aiger/xaiger.cc
+++ b/backends/aiger/xaiger.cc
@@ -436,15 +436,22 @@ struct XAigerWriter
 		for (const auto &bit : output_bits) {
 			ordered_outputs[bit] = aig_o++;
 			int aig;
-			// For inout/keep bits only, the output bit
-			//   should be driven by logic, not the PI,
-			//   so temporarily swap that out
+			// Unlike bit2aig() which checks aig_map first, for
+			//   inout/keep bits, since aig_map will point to
+			//   the PI, first attempt to find the NOT/AND driver
+			//   before resorting to an aig_map lookup (which
+			//   could be another PO)
 			if (input_bits.count(bit)) {
-				auto it = aig_map.find(bit);
-				int input_aig = it->second;
-				aig_map.erase(it);
-				aig = bit2aig(bit);
-				aig_map.at(bit) = input_aig;
+				if (not_map.count(bit)) {
+					aig = bit2aig(not_map.at(bit)) ^ 1;
+				} else if (and_map.count(bit)) {
+					auto args = and_map.at(bit);
+					int a0 = bit2aig(args.first);
+					int a1 = bit2aig(args.second);
+					aig = mkgate(a0, a1);
+				}
+				else
+					aig = aig_map.at(bit);
 			}
 			else
 				aig = bit2aig(bit);
diff --git a/frontends/aiger/aigerparse.cc b/frontends/aiger/aigerparse.cc
index b4304a581..f4decaf25 100644
--- a/frontends/aiger/aigerparse.cc
+++ b/frontends/aiger/aigerparse.cc
@@ -831,6 +831,7 @@ void AigerReader::post_process()
 					}
 					else {
 						wire->port_output = false;
+						existing->port_output = true;
 						module->connect(wire, existing);
 						wire = existing;
 					}
@@ -845,8 +846,9 @@ void AigerReader::post_process()
 							wideports_cache[escaped_s] = std::max(wideports_cache[escaped_s], index);
 					}
 					else {
-						module->connect(wire, existing);
 						wire->port_output = false;
+						existing->port_output = true;
+						module->connect(wire, existing);
 					}
 					log_debug(" -> %s\n", log_id(indexed_name));
 				}
diff --git a/passes/techmap/abc9.cc b/passes/techmap/abc9.cc
index 2627ab9ca..dad40be63 100644
--- a/passes/techmap/abc9.cc
+++ b/passes/techmap/abc9.cc
@@ -298,7 +298,7 @@ struct Abc9Pass : public ScriptPass
 							num_outputs);
 					if (num_outputs) {
 						run(stringf("%s -cwd %s", exe_cmd.str().c_str(), tempdir_name.c_str()));
-						run(stringf("read_aiger -xaiger -wideports -module_name %s$abc9 -map %s/input.sym %s/output.aig", log_id(mod->name), tempdir_name.c_str(), tempdir_name.c_str()));
+						run(stringf("read_aiger -xaiger -wideports -module_name %s$abc9 -map %s/input.sym %s/output.aig", log_id(mod), tempdir_name.c_str(), tempdir_name.c_str()));
 						run("abc9_ops -reintegrate");
 					}
 					else
diff --git a/passes/techmap/abc9_ops.cc b/passes/techmap/abc9_ops.cc
index 9cc58c99d..4da10d94b 100644
--- a/passes/techmap/abc9_ops.cc
+++ b/passes/techmap/abc9_ops.cc
@@ -53,30 +53,7 @@ void break_scc(RTLIL::Module *module)
 			if (cell->output(c.first)) {
 				SigBit b = c.second.as_bit();
 				Wire *w = b.wire;
-				if (w->port_input) {
-					// In this case, hopefully the loop break has been already created
-					// Get the non-prefixed wire
-					Wire *wo = module->wire(stringf("%s.abco", b.wire->name.c_str()));
-					log_assert(wo != nullptr);
-					log_assert(wo->port_output);
-					log_assert(b.offset < GetSize(wo));
-					c.second = RTLIL::SigBit(wo, b.offset);
-				}
-				else {
-					// Create a new output/input loop break
-					w->port_input = true;
-					w = module->wire(stringf("%s.abco", w->name.c_str()));
-					if (!w) {
-						w = module->addWire(stringf("%s.abco", b.wire->name.c_str()), GetSize(b.wire));
-						w->port_output = true;
-					}
-					else {
-						log_assert(w->port_input);
-						log_assert(b.offset < GetSize(w));
-					}
-					w->set_bool_attribute(ID(abc9_scc_break));
-					c.second = RTLIL::SigBit(w, b.offset);
-				}
+				w->set_bool_attribute(ID::keep);
 			}
 		}
 	}
@@ -586,7 +563,9 @@ void reintegrate(RTLIL::Module *module)
 				}
 				if (cell->output(mapped_conn.first))
 					for (auto i : mapped_conn.second)
-						bit_drivers[i].insert(mapped_cell->name);
+						// Ignore inouts for topo ordering
+						if (i.wire && !(i.wire->port_input && i.wire->port_output))
+							bit_drivers[i].insert(mapped_cell->name);
 			}
 		}
 		else {
-- 
2.30.2