From 4ffdee65e034493cf1eafd9f94d770c88d2f35e0 Mon Sep 17 00:00:00 2001
From: Charlotte <charlotte@hrzn.ee>
Date: Wed, 28 Jun 2023 11:51:31 +1000
Subject: [PATCH] cxxrtl: store comb $print cell last EN/ARGS in module

statics were obviously wrong -- may be multiple instantiations of any
given module.  Extend test to cover this.
---
 backends/cxxrtl/cxxrtl_backend.cc | 35 ++++++++++++-------------------
 tests/fmt/always_comb_tb.cc       |  9 +++++---
 tests/fmt/always_comb_tb.v        |  3 ++-
 3 files changed, 21 insertions(+), 26 deletions(-)

diff --git a/backends/cxxrtl/cxxrtl_backend.cc b/backends/cxxrtl/cxxrtl_backend.cc
index 82babe72b..17080ef2e 100644
--- a/backends/cxxrtl/cxxrtl_backend.cc
+++ b/backends/cxxrtl/cxxrtl_backend.cc
@@ -1219,12 +1219,13 @@ struct CxxrtlWorker {
 			log_assert(!for_debug);
 
 			auto trg_enable = cell->getParam(ID::TRG_ENABLE).as_bool();
-			static int cell_counter = 0;
+
 			if (!trg_enable) {
-				++cell_counter;
-				f << indent << "static bool last_print_" << cell_counter << "_known = false;\n";
-				f << indent << "static value<1> last_print_" << cell_counter << "_en;\n";
-				f << indent << "static value<" << cell->getPort(ID::ARGS).size() << "> last_print_" << cell_counter << "_args;\n";
+				f << indent << "auto " << mangle(cell) << "_curr = ";
+				dump_sigspec_rhs(cell->getPort(ID::EN));
+				f << ".concat(";
+				dump_sigspec_rhs(cell->getPort(ID::ARGS));
+				f << ").val();\n";
 			}
 
 			f << indent << "if (";
@@ -1246,16 +1247,7 @@ struct CxxrtlWorker {
 				}
 				f << ") && ";
 			} else {
-				f << '(';
-					f << "!last_print_" << cell_counter << "_known || ";
-					f << '(';
-						f << "last_print_" << cell_counter << "_en != ";
-						dump_sigspec_rhs(cell->getPort(ID::EN));
-
-						f << " || last_print_" << cell_counter << "_args != ";
-						dump_sigspec_rhs(cell->getPort(ID::ARGS));
-					f << ')';
-				f << ") && ";
+				f << mangle(cell) << " != " << mangle(cell) << "_curr && ";
 			}
 			dump_sigspec_rhs(cell->getPort(ID::EN));
 			f << " == value<1>{1u}) {\n";
@@ -1265,13 +1257,7 @@ struct CxxrtlWorker {
 			f << indent << "}\n";
 
 			if (!trg_enable) {
-				f << indent << "last_print_" << cell_counter << "_known = true;\n";
-				f << indent << "last_print_" << cell_counter << "_en = ";
-				dump_sigspec_rhs(cell->getPort(ID::EN));
-				f << ";\n";
-				f << indent << "last_print_" << cell_counter << "_args = ";
-				dump_sigspec_rhs(cell->getPort(ID::ARGS));
-				f << ";\n";
+				f << indent << mangle(cell) << " = " << mangle(cell) << "_curr;\n";
 			}
 		// Flip-flops
 		} else if (is_ff_cell(cell->type)) {
@@ -2362,6 +2348,11 @@ struct CxxrtlWorker {
 					f << "\n";
 				bool has_cells = false;
 				for (auto cell : module->cells()) {
+					if (cell->type == ID($print) && !cell->getParam(ID::TRG_ENABLE).as_bool()) {
+						// comb $print cell -- store the last EN/ARGS values to know when they change.
+						dump_attrs(cell);
+						f << indent << "value<" << (1 + cell->getParam(ID::ARGS_WIDTH).as_int()) << "> " << mangle(cell) << ";\n";
+					}
 					if (is_internal_cell(cell->type))
 						continue;
 					dump_attrs(cell);
diff --git a/tests/fmt/always_comb_tb.cc b/tests/fmt/always_comb_tb.cc
index c949af4e3..f2a8c6b26 100644
--- a/tests/fmt/always_comb_tb.cc
+++ b/tests/fmt/always_comb_tb.cc
@@ -3,11 +3,14 @@
 
 int main()
 {
-	cxxrtl_design::p_top uut;
+	cxxrtl_design::p_top uut1, uut2;
 
 	for (int i = 0; i < 20; ++i) {
-		uut.p_clk.set(!uut.p_clk);
-		uut.step();
+		uut1.p_clk.set(!uut1.p_clk);
+		uut1.step();
+
+		uut2.p_clk.set(!uut2.p_clk);
+		uut2.step();
 	}
 
 	return 0;
diff --git a/tests/fmt/always_comb_tb.v b/tests/fmt/always_comb_tb.v
index 447897433..3cc4496a0 100644
--- a/tests/fmt/always_comb_tb.v
+++ b/tests/fmt/always_comb_tb.v
@@ -1,7 +1,8 @@
 module tb;
     reg clk = 0;
 
-    top uut (.clk(clk));
+    top uut1 (.clk(clk));
+    top uut2 (.clk(clk));
 
     always #1 clk <= ~clk;
     initial #20 $finish;