Merge pull request #1790 from YosysHQ/eddie/opt_expr_xor

opt_expr: optimise $xor/$xnor/$_XOR_/$_XNOR_ -s with constant inputs

4 files changed, 92 insertions, 10 deletions

diff --git a/passes/opt/opt_expr.cc b/passes/opt/opt_expr.cc
index 723830aa0..1a9de7f40 100644
--- a/passes/opt/opt_expr.cc
+++ b/passes/opt/opt_expr.cc
@@ -496,6 +496,42 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 			}
 		}
 
+		if (cell->type.in(ID($_XOR_), ID($_XNOR_)) || (cell->type.in(ID($xor), ID($xnor)) && GetSize(cell->getPort(ID::A)) == 1 && GetSize(cell->getPort(ID::B)) == 1 && !cell->getParam(ID(A_SIGNED)).as_bool()))
+		{
+			SigBit sig_a = assign_map(cell->getPort(ID::A));
+			SigBit sig_b = assign_map(cell->getPort(ID::B));
+			if (!sig_a.wire)
+				std::swap(sig_a, sig_b);
+			if (sig_b == State::S0 || sig_b == State::S1) {
+				if (cell->type.in(ID($xor), ID($_XOR_))) {
+					cover("opt.opt_expr.xor_buffer");
+					SigSpec sig_y;
+					if (cell->type == ID($xor))
+						sig_y = (sig_b == State::S1 ? module->Not(NEW_ID, sig_a).as_bit() : sig_a);
+					else if (cell->type == ID($_XOR_))
+						sig_y = (sig_b == State::S1 ? module->NotGate(NEW_ID, sig_a) : sig_a);
+					else log_abort();
+					replace_cell(assign_map, module, cell, "xor_buffer", ID::Y, sig_y);
+					goto next_cell;
+				}
+				if (cell->type.in(ID($xnor), ID($_XNOR_))) {
+					cover("opt.opt_expr.xnor_buffer");
+					SigSpec sig_y;
+					if (cell->type == ID($xnor)) {
+						sig_y = (sig_b == State::S1 ? sig_a : module->Not(NEW_ID, sig_a).as_bit());
+						int width = cell->getParam(ID(Y_WIDTH)).as_int();
+						sig_y.append(RTLIL::Const(State::S1, width-1));
+					}
+					else if (cell->type == ID($_XNOR_))
+						sig_y = (sig_b == State::S1 ? sig_a : module->NotGate(NEW_ID, sig_a));
+					else log_abort();
+					replace_cell(assign_map, module, cell, "xnor_buffer", ID::Y, sig_y);
+					goto next_cell;
+				}
+				log_abort();
+			}
+		}
+
 		if (cell->type.in(ID($reduce_and), ID($reduce_or), ID($reduce_bool), ID($reduce_xor), ID($reduce_xnor), ID($neg)) &&
 				GetSize(cell->getPort(ID::A)) == 1 && GetSize(cell->getPort(ID::Y)) == 1)
 		{
@@ -850,8 +886,6 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 			if (input.match("11")) ACTION_DO_Y(0);
 			if (input.match(" *")) ACTION_DO_Y(x);
 			if (input.match("* ")) ACTION_DO_Y(x);
-			if (input.match(" 0")) ACTION_DO(ID::Y, input.extract(1, 1));
-			if (input.match("0 ")) ACTION_DO(ID::Y, input.extract(0, 1));
 		}
 
 		if (cell->type == ID($_MUX_)) {
@@ -1622,7 +1656,7 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 					}
 
 					int const_bit_set = get_highest_hot_index(const_sig);
-					if(const_bit_set >= var_width)
+					if (const_bit_set >= var_width)
 					{
 						string cmp_name;
 						if (cmp_type == ID($lt) || cmp_type == ID($le))
diff --git a/tests/arch/anlogic/fsm.ys b/tests/arch/anlogic/fsm.ys
index 0bcc4e011..eb94177ad 100644
--- a/tests/arch/anlogic/fsm.ys
+++ b/tests/arch/anlogic/fsm.ys
@@ -10,9 +10,6 @@ sat -verify -prove-asserts -show-public -set-at 1 in_reset 1 -seq 20 -prove-skip
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd fsm # Constrain all select calls below inside the top module
 
-select -assert-count 1 t:AL_MAP_LUT2
-select -assert-count 5 t:AL_MAP_LUT5
-select -assert-count 1 t:AL_MAP_LUT6
 select -assert-count 6 t:AL_MAP_SEQ
 
-select -assert-none t:AL_MAP_LUT2 t:AL_MAP_LUT5 t:AL_MAP_LUT6 t:AL_MAP_SEQ %% t:* %D
+select -assert-none t:AL_MAP_LUT* t:AL_MAP_SEQ %% t:* %D
diff --git a/tests/arch/efinix/fsm.ys b/tests/arch/efinix/fsm.ys
index a2db2ad98..aef720d46 100644
--- a/tests/arch/efinix/fsm.ys
+++ b/tests/arch/efinix/fsm.ys
@@ -10,7 +10,6 @@ sat -verify -prove-asserts -show-public -set-at 1 in_reset 1 -seq 20 -prove-skip
 design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
 cd fsm # Constrain all select calls below inside the top module
 
-select -assert-count 1  t:EFX_GBUFCE
-select -assert-count 6  t:EFX_FF
-select -assert-count 15 t:EFX_LUT4
+select -assert-count 1 t:EFX_GBUFCE
+select -assert-count 6 t:EFX_FF
 select -assert-none t:EFX_GBUFCE t:EFX_FF t:EFX_LUT4 %% t:* %D
diff --git a/tests/opt/opt_expr_xor.ys b/tests/opt/opt_expr_xor.ys
new file mode 100644
index 000000000..21439fd53
--- /dev/null
+++ b/tests/opt/opt_expr_xor.ys
@@ -0,0 +1,52 @@
+read_verilog <<EOT
+module top(input a, output [3:0] y);
+assign y[0] = a^1'b0;
+assign y[1] = 1'b1^a;
+assign y[2] = a~^1'b0;
+assign y[3] = 1'b1^~a;
+endmodule
+EOT
+design -save read
+select -assert-count 2 t:$xor
+select -assert-count 2 t:$xnor
+
+equiv_opt opt_expr
+design -load postopt
+select -assert-none t:$xor
+select -assert-none t:$xnor
+select -assert-count 2 t:$not
+
+
+design -load read
+simplemap
+equiv_opt opt_expr
+design -load postopt
+select -assert-none t:$_XOR_
+select -assert-none t:$_XNOR_ # NB: simplemap does $xnor -> $_XOR_+$_NOT_
+select -assert-count 3 t:$_NOT_
+
+
+design -reset
+read_verilog -icells <<EOT
+module top(input a, output [1:0] y);
+$_XNOR_ u0(.A(a), .B(1'b0), .Y(y[0]));
+$_XNOR_ u1(.A(1'b1), .B(a), .Y(y[1]));
+endmodule
+EOT
+select -assert-count 2 t:$_XNOR_
+equiv_opt opt_expr
+design -load postopt
+select -assert-none t:$_XNOR_ # NB: simplemap does $xnor -> $_XOR_+$_NOT_
+select -assert-count 1 t:$_NOT_
+
+
+design -reset
+read_verilog <<EOT
+module top(input a, output [1:0] w, x, y, z);
+assign w = a^1'b0;
+assign x = a^1'b1;
+assign y = a~^1'b0;
+assign z = a~^1'b1;
+endmodule
+EOT
+equiv_opt opt_expr