1 files changed, 50 insertions, 28 deletions

diff --git a/passes/proc/proc_mux.cc b/passes/proc/proc_mux.cc
index bac2dc2cd..aac0b121c 100644
--- a/passes/proc/proc_mux.cc
+++ b/passes/proc/proc_mux.cc
@@ -108,6 +108,7 @@ struct SigSnippets
 
 struct SnippetSwCache
 {
+	dict<RTLIL::SwitchRule*, pool<RTLIL::SigBit>, hash_ptr_ops> full_case_bits_cache;
 	dict<RTLIL::SwitchRule*, pool<int>, hash_ptr_ops> cache;
 	const SigSnippets *snippets;
 	int current_snippet;
@@ -268,6 +269,49 @@ void append_pmux(RTLIL::Module *mod, const RTLIL::SigSpec &signal, const std::ve
 	last_mux_cell->parameters["\\S_WIDTH"] = last_mux_cell->getPort("\\S").size();
 }
 
+const pool<SigBit> &get_full_case_bits(SnippetSwCache &swcache, RTLIL::SwitchRule *sw)
+{
+	if (!swcache.full_case_bits_cache.count(sw))
+	{
+		pool<SigBit> bits;
+
+		if (sw->get_bool_attribute("\\full_case"))
+		{
+			bool first_case = true;
+
+			for (auto cs : sw->cases)
+			{
+				pool<SigBit> case_bits;
+
+				for (auto it : cs->actions) {
+					for (auto bit : it.first)
+						case_bits.insert(bit);
+				}
+
+				for (auto it : cs->switches) {
+					for (auto bit : get_full_case_bits(swcache, it))
+						case_bits.insert(bit);
+				}
+
+				if (first_case) {
+					first_case = false;
+					bits = case_bits;
+				} else {
+					pool<SigBit> new_bits;
+					for (auto bit : bits)
+						if (case_bits.count(bit))
+							new_bits.insert(bit);
+					bits.swap(new_bits);
+				}
+			}
+		}
+
+		bits.swap(swcache.full_case_bits_cache[sw]);
+	}
+
+	return swcache.full_case_bits_cache.at(sw);
+}
+
 RTLIL::SigSpec signal_to_mux_tree(RTLIL::Module *mod, SnippetSwCache &swcache, dict<RTLIL::SwitchRule*, bool, hash_ptr_ops> &swpara,
 		RTLIL::CaseRule *cs, const RTLIL::SigSpec &sig, const RTLIL::SigSpec &defval, bool ifxmode)
 {
@@ -337,10 +381,15 @@ RTLIL::SigSpec signal_to_mux_tree(RTLIL::Module *mod, SnippetSwCache &swcache, d
 			}
 		}
 
+		// mask default bits that are irrelevant because the output is driven by a full case
+		const pool<SigBit> &full_case_bits = get_full_case_bits(swcache, sw);
+		for (int i = 0; i < GetSize(sig); i++)
+			if (full_case_bits.count(sig[i]))
+				result[i] = State::Sx;
+
 		// evaluate in reverse order to give the first entry the top priority
 		RTLIL::SigSpec initial_val = result;
 		RTLIL::Cell *last_mux_cell = NULL;
-		bool shiftx = initial_val.is_fully_undef();
 		for (size_t i = 0; i < sw->cases.size(); i++) {
 			int case_idx = sw->cases.size() - i - 1;
 			RTLIL::CaseRule *cs2 = sw->cases[case_idx];
@@ -349,33 +398,6 @@ RTLIL::SigSpec signal_to_mux_tree(RTLIL::Module *mod, SnippetSwCache &swcache, d
 				append_pmux(mod, sw->signal, cs2->compare, value, last_mux_cell, sw, ifxmode);
 			else
 				result = gen_mux(mod, sw->signal, cs2->compare, value, result, last_mux_cell, sw, ifxmode);
-
-			// Ignore output values which are entirely don't care
-			if (shiftx && !value.is_fully_undef()) {
-				// Keep checking if case condition is the same as the current case index
-				if (cs2->compare.size() == 1 && cs2->compare.front().is_fully_const())
-					shiftx = (cs2->compare.front().as_int() == case_idx);
-				else
-					shiftx = false;
-			}
-		}
-
-		// Transform into a $shiftx where possible
-		if (shiftx && last_mux_cell && last_mux_cell->type == "$pmux") {
-			// Create bit-blasted $shiftx-es that shifts by the address line used in the case statement
-			auto pmux_b_port = last_mux_cell->getPort("\\B");
-			auto pmux_y_port = last_mux_cell->getPort("\\Y");
-			int width = last_mux_cell->getParam("\\WIDTH").as_int();
-			for (int i = 0; i < width; ++i) {
-				RTLIL::SigSpec a_port;
-				// Because we went in reverse order above, un-reverse $pmux's B port here
-				for (int j = pmux_b_port.size()/width-1; j >= 0; --j)
-					a_port.append(pmux_b_port.extract(j*width+i, 1));
-				// Create a $shiftx that shifts by the address line used in the case statement
-				mod->addShiftx(NEW_ID, a_port, sw->signal, pmux_y_port.extract(i, 1));
-			}
-			// Disconnect $pmux by replacing its output port with a floating wire
-			last_mux_cell->setPort("\\Y", mod->addWire(NEW_ID, width));
 		}
 	}