Merge pull request #1213 from YosysHQ/eddie/wreduce_add

wreduce/opt_expr: improve width reduction for $add and $sub cells

kernel/rtlil.h

@@ -788,6 +788,7 @@ public:
 	RTLIL::SigSpec extract(const RTLIL::SigSpec &pattern, const RTLIL::SigSpec *other = NULL) const;
 	RTLIL::SigSpec extract(const pool<RTLIL::SigBit> &pattern, const RTLIL::SigSpec *other = NULL) const;
 	RTLIL::SigSpec extract(int offset, int length = 1) const;
+	RTLIL::SigSpec extract_end(int offset) const { return extract(offset, width_ - offset); }
 
 	void append(const RTLIL::SigSpec &signal);
 	void append_bit(const RTLIL::SigBit &bit);
@@ -834,6 +835,7 @@ public:
 
 	operator std::vector<RTLIL::SigChunk>() const { return chunks(); }
 	operator std::vector<RTLIL::SigBit>() const { return bits(); }
+	RTLIL::SigBit at(int offset, const RTLIL::SigBit &defval) { return offset < width_ ? (*this)[offset] : defval; }
 
 	unsigned int hash() const { if (!hash_) updhash(); return hash_; };
 

passes/opt/opt_expr.cc

@@ -641,6 +641,31 @@ void replace_const_cells(RTLIL::Design *design, RTLIL::Module *module, bool cons
 					did_something = true;
 				}
 			}
+
+			if (cell->type.in("$add", "$sub")) {
+				RTLIL::SigSpec sig_a = assign_map(cell->getPort("\\A"));
+				RTLIL::SigSpec sig_b = assign_map(cell->getPort("\\B"));
+				RTLIL::SigSpec sig_y = cell->getPort("\\Y");
+				bool sub = cell->type == "$sub";
+
+				int i;
+				for (i = 0; i < GetSize(sig_y); i++) {
+					if (sig_b.at(i, State::Sx) == State::S0 && sig_a.at(i, State::Sx) != State::Sx)
+						module->connect(sig_y[i], sig_a[i]);
+					else if (!sub && sig_a.at(i, State::Sx) == State::S0 && sig_b.at(i, State::Sx) != State::Sx)
+						module->connect(sig_y[i], sig_b[i]);
+					else
+						break;
+				}
+				if (i > 0) {
+					cover_list("opt.opt_expr.fine", "$add", "$sub", cell->type.str());
+					cell->setPort("\\A", sig_a.extract_end(i));
+					cell->setPort("\\B", sig_b.extract_end(i));
+					cell->setPort("\\Y", sig_y.extract_end(i));
+					cell->fixup_parameters();
+					did_something = true;
+				}
+			}
 		}
 
 		if (cell->type == "$reduce_xor" || cell->type == "$reduce_xnor" || cell->type == "$shift" || cell->type == "$shiftx" ||

passes/opt/wreduce.cc

@@ -342,9 +342,9 @@ struct WreduceWorker
 			}
 		}
 
-		if (cell->type.in("$pos", "$add", "$mul", "$and", "$or", "$xor"))
+		if (cell->type.in("$pos", "$add", "$mul", "$and", "$or", "$xor", "$sub"))
 		{
-			bool is_signed = cell->getParam("\\A_SIGNED").as_bool();
+			bool is_signed = cell->getParam("\\A_SIGNED").as_bool() || cell->type == "$sub";
 
 			int a_size = 0, b_size = 0;
 			if (cell->hasPort("\\A")) a_size = GetSize(cell->getPort("\\A"));
@@ -352,7 +352,7 @@ struct WreduceWorker
 
 			int max_y_size = max(a_size, b_size);
 
-			if (cell->type == "$add")
+			if (cell->type.in("$add", "$sub"))
 				max_y_size++;
 
 			if (cell->type == "$mul")

tests/various/opt_expr.ys

@@ -0,0 +1,148 @@
+
+read_verilog <<EOT
+module opt_expr_add_test(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = (i << 4) + j;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$add r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module opt_expr_add_signed_test(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
+    assign o = (i << 4) + j;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$add r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module opt_expr_sub_test1(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = j - (i << 4);
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module opt_expr_sub_signed_test1(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
+    assign o = j - (i << 4);
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module opt_expr_sub_test2(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = (i << 4) - j;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$sub r:A_WIDTH=8 r:B_WIDTH=8 r:Y_WIDTH=9 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module opt_expr_sub_test4(input [3:0] i, output [8:0] o);
+    assign o = 5'b00010 - i;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr -fine
+wreduce
+
+select -assert-count 1 t:$sub r:A_WIDTH=2 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter

tests/various/wreduce.ys

@@ -0,0 +1,48 @@
+read_verilog <<EOT
+module wreduce_sub_test(input [3:0] i, input [7:0] j, output [8:0] o);
+    assign o = (j >> 4) - i;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr
+wreduce
+
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter
+
+##########
+
+read_verilog <<EOT
+module wreduce_sub_signed_test(input signed [3:0] i, input signed [7:0] j, output signed [8:0] o);
+    assign o = (j >>> 4) - i;
+endmodule
+EOT
+
+hierarchy -auto-top
+proc
+design -save gold
+
+opt_expr
+wreduce
+
+dump
+select -assert-count 1 t:$sub r:A_WIDTH=4 r:B_WIDTH=4 r:Y_WIDTH=5 %i %i %i
+
+design -stash gate
+
+design -import gold -as gold
+design -import gate -as gate
+
+miter -equiv -flatten -make_assert -make_outputs gold gate miter
+sat -verify -prove-asserts -show-ports miter