In the ABC pass, avoid scanning the entire module for each ABC run

kernel/ffinit.h

@@ -27,10 +27,10 @@ YOSYS_NAMESPACE_BEGIN
 
 struct FfInitVals
 {
-	const SigMap *sigmap;
+	const SigMapView *sigmap;
 	dict<SigBit, std::pair<State,SigBit>> initbits;
 
-	void set(const SigMap *sigmap_, RTLIL::Module *module)
+	void set(const SigMapView *sigmap_, RTLIL::Module *module)
 	{
 		sigmap = sigmap_;
 		initbits.clear();
@@ -126,7 +126,7 @@ struct FfInitVals
 		initbits.clear();
 	}
 
-	FfInitVals (const SigMap *sigmap, RTLIL::Module *module)
+	FfInitVals (const SigMapView *sigmap, RTLIL::Module *module)
 	{
 		set(sigmap, module);
 	}

kernel/ffmerge.h

@@ -58,7 +58,7 @@ YOSYS_NAMESPACE_BEGIN
 
 struct FfMergeHelper
 {
-	const SigMap *sigmap;
+	const SigMapView *sigmap;
 	RTLIL::Module *module;
 	FfInitVals *initvals;
 

kernel/hashlib.h

@@ -1353,7 +1353,8 @@ class mfp
 		return p;
 	}
 
-	// Merge sets if the given indices belong to different sets
+	// Merge sets if the given indices belong to different sets.
+	// Makes ifind(j) the root of the merged set.
 	void imerge(int i, int j)
 	{
 		i = ifind(i);

kernel/sigtools.h

@@ -237,17 +237,51 @@ using sort_by_name_id_guard = typename std::enable_if<std::is_same<T,RTLIL::Cell
 template<typename T>
 class SigSet<T, sort_by_name_id_guard<T>> : public SigSet<T, RTLIL::sort_by_name_id<typename std::remove_pointer<T>::type>> {};
 
+struct SigMapView
+{
+	mfp<SigBit> database;
+
+	// Modify bit to its representative
+	void apply(RTLIL::SigBit &bit) const
+	{
+		bit = database.find(bit);
+	}
+
+	void apply(RTLIL::SigSpec &sig) const
+	{
+		for (auto &bit : sig)
+			apply(bit);
+	}
+
+	RTLIL::SigBit operator()(RTLIL::SigBit bit) const
+	{
+		apply(bit);
+		return bit;
+	}
+
+	RTLIL::SigSpec operator()(RTLIL::SigSpec sig) const
+	{
+		apply(sig);
+		return sig;
+	}
+
+	RTLIL::SigSpec operator()(RTLIL::Wire *wire) const
+	{
+		SigSpec sig(wire);
+		apply(sig);
+		return sig;
+	}
+};
+
 /**
  * SigMap wraps a union-find "database"
  * to map SigBits of a module to canonical representative SigBits.
  * SigBits that are connected share a set in the underlying database.
  * If a SigBit has a const state (impl: bit.wire is nullptr),
  * it's promoted to a representative.
  */
-struct SigMap
+struct SigMap final : public SigMapView
 {
-	mfp<SigBit> database;
-
 	SigMap(RTLIL::Module *module = NULL)
 	{
 		if (module != NULL)
@@ -320,45 +354,115 @@ struct SigMap
 
 	inline void add(Wire *wire) { return add(RTLIL::SigSpec(wire)); }
 
-	// Modify bit to its representative
-	void apply(RTLIL::SigBit &bit) const
+	// All non-const bits
+	RTLIL::SigSpec allbits() const
 	{
-		bit = database.find(bit);
+		RTLIL::SigSpec sig;
+		for (const auto &bit : database)
+			if (bit.wire != nullptr)
+				sig.append(bit);
+		return sig;
 	}
+};
 
-	void apply(RTLIL::SigSpec &sig) const
+/**
+ * SiValgMap wraps a union-find "database" to map SigBits of a module to
+ * canonical representative SigBits plus some optional Val value associated with the bits.
+ * Val has a commutative, associative, idempotent operator|=, a default constructor
+ * which constructs an identity element, and a copy constructor.
+ * SigBits that are connected share a set in the underlying database;
+ * the associated value is the "sum" of all the values associated with the contributing bits.
+ * If any of the SigBits in a set are a constant, the canonical SigBit is a constant.
+ */
+template <class Val>
+struct SigValMap final : public SigMapView
+{
+	dict<SigBit, Val> values;
+
+	void swap(SigValMap<Val> &other)
 	{
-		for (auto &bit : sig)
-			apply(bit);
+		database.swap(other.database);
+		values.swap(other.values);
 	}
 
-	RTLIL::SigBit operator()(RTLIL::SigBit bit) const
+	void clear()
 	{
-		apply(bit);
-		return bit;
+		database.clear();
+		values.clear();
 	}
 
-	RTLIL::SigSpec operator()(RTLIL::SigSpec sig) const
+	// Rebuild SigMap for all connections in module
+	void set(RTLIL::Module *module)
 	{
-		apply(sig);
-		return sig;
+		int bitcount = 0;
+		for (auto &it : module->connections())
+			bitcount += it.first.size();
+
+		database.clear();
+		values.clear();
+		database.reserve(bitcount);
+
+		for (auto &it : module->connections())
+			add(it.first, it.second);
 	}
 
-	RTLIL::SigSpec operator()(RTLIL::Wire *wire) const
+	// Add connections from "from" to "to", bit-by-bit.
+	void add(const RTLIL::SigSpec& from, const RTLIL::SigSpec& to)
 	{
-		SigSpec sig(wire);
-		apply(sig);
-		return sig;
+		log_assert(GetSize(from) == GetSize(to));
+
+		for (int i = 0; i < GetSize(from); i++)
+		{
+			int bfi = database.lookup(from[i]);
+			int bti = database.lookup(to[i]);
+			if (bfi == bti) {
+				continue;
+			}
+
+			const RTLIL::SigBit &bf = database[bfi];
+			const RTLIL::SigBit &bt = database[bti];
+			if (bf.wire == nullptr) {
+				// bf is constant so make it the canonical representative.
+				database.imerge(bti, bfi);
+				merge_value(bt, bf);
+			} else {
+				// Make bt the canonical representative.
+				database.imerge(bfi, bti);
+				merge_value(bf, bt);
+			}
+		}
 	}
 
-	// All non-const bits
-	RTLIL::SigSpec allbits() const
+	void addVal(const RTLIL::SigBit &bit, const Val &val)
 	{
-		RTLIL::SigSpec sig;
-		for (const auto &bit : database)
-			if (bit.wire != nullptr)
-				sig.append(bit);
-		return sig;
+		values[database.find(bit)] |= val;
+	}
+
+	void addVal(const RTLIL::SigSpec &sig, const Val &val)
+	{
+		for (const auto &bit : sig)
+			addVal(bit, val);
+	}
+
+	Val apply_and_get_value(RTLIL::SigBit &bit) const
+	{
+		bit = database.find(bit);
+		auto it = values.find(bit);
+		return it == values.end() ? Val() : it->second;
+	}
+
+private:
+	void merge_value(const RTLIL::SigBit &from, const RTLIL::SigBit &to)
+	{
+		auto it = values.find(from);
+		if (it == values.end()) {
+			return;
+		}
+		// values[to] could resize the underlying `entries` so
+		// finish using `it` first.
+		Val v = it->second;
+		values.erase(it);
+		values[to] |= v;
 	}
 };