Merge pull request #3305 from jix/sva_value_change_logic

verific: Improve logic generated for SVA value change expressions

frontends/verific/verific.cc

@@ -1557,17 +1557,25 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 
 			SigSpec sig_d = net_map_at(inst->GetInput1());
 			SigSpec sig_o = net_map_at(inst->GetOutput());
-			SigSpec sig_q = module->addWire(new_verific_id(inst));
+			SigSpec sig_dx = module->addWire(new_verific_id(inst), 2);
+			SigSpec sig_qx = module->addWire(new_verific_id(inst), 2);
 
 			if (verific_verbose) {
+				log("    NEX with A=%s, B=0, Y=%s.\n",
+						log_signal(sig_d), log_signal(sig_dx[0]));
+				log("    EQX with A=%s, B=1, Y=%s.\n",
+						log_signal(sig_d), log_signal(sig_dx[1]));
 				log("    %sedge FF with D=%s, Q=%s, C=%s.\n", clocking.posedge ? "pos" : "neg",
-						log_signal(sig_d), log_signal(sig_q), log_signal(clocking.clock_sig));
-				log("    XNOR with A=%s, B=%s, Y=%s.\n",
-						log_signal(sig_d), log_signal(sig_q), log_signal(sig_o));
+						log_signal(sig_dx), log_signal(sig_qx), log_signal(clocking.clock_sig));
+				log("    EQ with A=%s, B=%s, Y=%s.\n",
+						log_signal(sig_dx), log_signal(sig_qx), log_signal(sig_o));
 			}
 
-			clocking.addDff(new_verific_id(inst), sig_d, sig_q);
-			module->addXnor(new_verific_id(inst), sig_d, sig_q, sig_o);
+			module->addNex(new_verific_id(inst), sig_d, State::S0, sig_dx[0]);
+			module->addEqx(new_verific_id(inst), sig_d, State::S1, sig_dx[1]);
+
+			clocking.addDff(new_verific_id(inst), sig_dx, sig_qx, Const(1, 2));
+			module->addEq(new_verific_id(inst), sig_dx, sig_qx, sig_o);
 
 			if (!mode_keep)
 				continue;
@@ -1601,13 +1609,20 @@ void VerificImporter::import_netlist(RTLIL::Design *design, Netlist *nl, std::ma
 			SigBit sig_d = net_map_at(inst->GetInput1());
 			SigBit sig_o = net_map_at(inst->GetOutput());
 			SigBit sig_q = module->addWire(new_verific_id(inst));
+			SigBit sig_d_no_x = module->addWire(new_verific_id(inst));
 
-			if (verific_verbose)
+			if (verific_verbose) {
+				log("    EQX with A=%s, B=%d, Y=%s.\n",
+						log_signal(sig_d), inst->Type() == PRIM_SVA_ROSE, log_signal(sig_d_no_x));
 				log("    %sedge FF with D=%s, Q=%s, C=%s.\n", clocking.posedge ? "pos" : "neg",
-						log_signal(sig_d), log_signal(sig_q), log_signal(clocking.clock_sig));
+						log_signal(sig_d_no_x), log_signal(sig_q), log_signal(clocking.clock_sig));
+				log("    EQ with A={%s, %s}, B={0, 1}, Y=%s.\n",
+						log_signal(sig_q), log_signal(sig_d_no_x), log_signal(sig_o));
+			}
 
-			clocking.addDff(new_verific_id(inst), sig_d, sig_q);
-			module->addEq(new_verific_id(inst), {sig_q, sig_d}, Const(inst->Type() == PRIM_SVA_ROSE ? 1 : 2, 2), sig_o);
+			module->addEqx(new_verific_id(inst), sig_d, inst->Type() == PRIM_SVA_ROSE ? State::S1 : State::S0, sig_d_no_x);
+			clocking.addDff(new_verific_id(inst), sig_d_no_x, sig_q, State::S0);
+			module->addEq(new_verific_id(inst), {sig_q, sig_d_no_x}, Const(1, 2), sig_o);
 
 			if (!mode_keep)
 				continue;

tests/sva/.gitignore

@@ -3,5 +3,6 @@
 /*_pass
 /*_fail
 /*.ok
+/*.fst
 /vhdlpsl[0-9][0-9]
 /vhdlpsl[0-9][0-9].sby

tests/sva/Makefile

@@ -10,4 +10,5 @@ clean:
 	rm -rf $(addsuffix .ok,$(TESTS)) $(addsuffix .sby,$(TESTS)) $(TESTS)
 	rm -rf $(addsuffix _pass.sby,$(TESTS)) $(addsuffix _pass,$(TESTS))
 	rm -rf $(addsuffix _fail.sby,$(TESTS)) $(addsuffix _fail,$(TESTS))
+	rm -rf $(addsuffix .fst,$(TESTS))
 

tests/sva/runtest.sh

@@ -57,7 +57,9 @@ generate_sby() {
 	fi
 }
 
-if [ -f $prefix.sv ]; then
+if [ -f $prefix.ys ]; then
+	$PWD/../../yosys -q -e "Assert .* failed." -s $prefix.ys
+elif [ -f $prefix.sv ]; then
 	generate_sby pass > ${prefix}_pass.sby
 	generate_sby fail > ${prefix}_fail.sby
 	sby --yosys $PWD/../../yosys -f ${prefix}_pass.sby

tests/sva/sva_value_change_changed.sv

@@ -0,0 +1,17 @@
+module top (
+	input clk,
+	input a, b
+);
+	default clocking @(posedge clk); endclocking
+
+	assert property (
+		$changed(b)
+	);
+
+`ifndef FAIL
+	assume property (
+		b !== 'x ##1 $changed(b)
+	);
+`endif
+
+endmodule

tests/sva/sva_value_change_rose.sv

@@ -0,0 +1,20 @@
+module top (
+	input clk,
+	input a, b
+);
+	default clocking @(posedge clk); endclocking
+
+    wire a_copy;
+    assign a_copy = a;
+
+	assert property (
+		$rose(a) |-> b
+	);
+
+`ifndef FAIL
+	assume property (
+		$rose(a_copy) |-> b
+	);
+`endif
+
+endmodule

tests/sva/sva_value_change_sim.sv

@@ -0,0 +1,51 @@
+module top (
+	input clk
+);
+
+reg [7:0] counter = 0;
+
+reg a = 0;
+reg b = 1;
+reg c;
+
+wire a_fell; assign a_fell = $fell(a, @(posedge clk));
+wire a_rose; assign a_rose = $rose(a, @(posedge clk));
+wire a_stable; assign a_stable = $stable(a, @(posedge clk));
+
+wire b_fell; assign b_fell = $fell(b, @(posedge clk));
+wire b_rose; assign b_rose = $rose(b, @(posedge clk));
+wire b_stable; assign b_stable = $stable(b, @(posedge clk));
+
+wire c_fell; assign c_fell = $fell(c, @(posedge clk));
+wire c_rose; assign c_rose = $rose(c, @(posedge clk));
+wire c_stable; assign c_stable = $stable(c, @(posedge clk));
+
+always @(posedge clk) begin
+	counter <= counter + 1;
+
+	case (counter)
+		0: begin
+            assert property ( $fell(a) && !$rose(a) && !$stable(a));
+            assert property (!$fell(b) &&  $rose(b) && !$stable(b));
+            assert property (!$fell(c) && !$rose(c) &&  $stable(c));
+            a <= 1; b <= 1; c <= 1;
+        end
+		1: begin a <= 0; b <= 1; c <= 'x; end
+		2: begin
+            assert property ( $fell(a) && !$rose(a) && !$stable(a));
+            assert property (!$fell(b) && !$rose(b) &&  $stable(b));
+            assert property (!$fell(c) && !$rose(c) && !$stable(c));
+            a <= 0; b <= 0; c <= 0;
+        end
+		3: begin a <= 0; b <= 1; c <= 'x; end
+		4: begin
+            assert property (!$fell(a) && !$rose(a) &&  $stable(a));
+            assert property (!$fell(b) &&  $rose(b) && !$stable(b));
+            assert property (!$fell(c) && !$rose(c) && !$stable(c));
+            a <= 'x; b <= 'x; c <= 'x;
+        end
+		5: begin a <= 0; b <= 1; c <= 'x; counter <= 0; end
+	endcase;
+end
+
+endmodule

tests/sva/sva_value_change_sim.ys

@@ -0,0 +1,3 @@
+read -sv sva_value_change_sim.sv
+hierarchy -top top
+sim -clock clk -fst sva_value_change_sim.fst