From a038787c9b51e92440cac3a38801c08f66dbb3af Mon Sep 17 00:00:00 2001
From: Clifford Wolf <clifford@clifford.at>
Date: Wed, 4 Feb 2015 18:52:54 +0100
Subject: [PATCH] Added onehot attribute

---
 README                        |  3 +++
 passes/fsm/fsm_map.cc         |  3 +++
 passes/memory/memory_share.cc | 13 +++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/README b/README
index 476e5ce54..fbd92db36 100644
--- a/README
+++ b/README
@@ -268,6 +268,9 @@ Verilog Attributes and non-standard features
   temporary variable within an always block. This is mostly used internally
   by yosys to synthesize verilog functions and access arrays.
 
+- The "onehot" attribute on wires mark them as onehot state register. This
+  is used for example for memory port sharing and set by the fsm_map pass.
+
 - The "blackbox" attribute on modules is used to mark empty stub modules
   that have the same ports as the real thing but do not contain information
   on the internal configuration. This modules are only used by the synthesis
diff --git a/passes/fsm/fsm_map.cc b/passes/fsm/fsm_map.cc
index a260653fb..155801a3a 100644
--- a/passes/fsm/fsm_map.cc
+++ b/passes/fsm/fsm_map.cc
@@ -224,6 +224,9 @@ static void map_fsm(RTLIL::Cell *fsm_cell, RTLIL::Module *module)
 		}
 	}
 
+	if (encoding_is_onehot)
+		state_wire->set_bool_attribute("\\onehot");
+
 	// generate next_state signal
 
 	if (GetSize(fsm_data.state_table) == 1)
diff --git a/passes/memory/memory_share.cc b/passes/memory/memory_share.cc
index ec8df7598..a2f89f6d9 100644
--- a/passes/memory/memory_share.cc
+++ b/passes/memory/memory_share.cc
@@ -544,6 +544,7 @@ struct MemoryShareWorker
 
 		// create SAT representation of common input cone of all considered EN signals
 
+		pool<Wire*> one_hot_wires;
 		std::set<RTLIL::Cell*> sat_cells;
 		std::set<RTLIL::SigBit> bits_queue;
 		std::map<int, int> port_to_sat_variable;
@@ -560,6 +561,10 @@ struct MemoryShareWorker
 
 		while (!bits_queue.empty())
 		{
+			for (auto bit : bits_queue)
+				if (bit.wire && bit.wire->get_bool_attribute("\\onehot"))
+					one_hot_wires.insert(bit.wire);
+
 			pool<ModWalker::PortBit> portbits;
 			modwalker.get_drivers(portbits, bits_queue);
 			bits_queue.clear();
@@ -572,6 +577,14 @@ struct MemoryShareWorker
 				}
 		}
 
+		for (auto wire : one_hot_wires) {
+			log("  Adding one-hot constraint for wire %s.\n", log_id(wire));
+			vector<int> ez_wire_bits = satgen.importSigSpec(wire);
+			for (int i : ez_wire_bits)
+			for (int j : ez_wire_bits)
+				if (i != j) ez.assume(ez.NOT(i), j);
+		}
+
 		log("  Common input cone for all EN signals: %d cells.\n", int(sat_cells.size()));
 
 		for (auto cell : sat_cells)
-- 
2.30.2