Merge pull request #4298 from povik/kogge-stone

techmap: Add a Kogge-Stone option for `$lcu` mapping

techlibs/common/Makefile.inc

@@ -35,3 +35,4 @@ $(eval $(call add_share_file,share,techlibs/common/abc9_map.v))
 $(eval $(call add_share_file,share,techlibs/common/abc9_unmap.v))
 $(eval $(call add_share_file,share,techlibs/common/cmp2lcu.v))
 $(eval $(call add_share_file,share,techlibs/common/cmp2softlogic.v))
+$(eval $(call add_share_file,share/choices,techlibs/common/choices/kogge-stone.v))

techlibs/common/choices/kogge-stone.v

@@ -0,0 +1,54 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2024  Martin Povišer <povik@cutebit.org>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+(* techmap_celltype = "$lcu" *)
+module _80_lcu_kogge_stone (P, G, CI, CO);
+	parameter WIDTH = 2;
+
+	(* force_downto *)
+	input [WIDTH-1:0] P, G;
+	input CI;
+
+	(* force_downto *)
+	output [WIDTH-1:0] CO;
+
+	integer i, j;
+	(* force_downto *)
+	reg [WIDTH-1:0] p, g;
+
+	wire [1023:0] _TECHMAP_DO_ = "proc; opt -fast";
+
+	always @* begin
+		p = P;
+		g = G;
+
+		// in almost all cases CI will be constant zero
+		g[0] = g[0] | (p[0] & CI);
+
+		for (i = 0; i < $clog2(WIDTH); i = i + 1) begin
+			// iterate in reverse so we don't confuse a result from this stage and the previous
+			for (j = WIDTH - 1; j >= 2**i; j = j - 1) begin
+				g[j] = g[j] | p[j] & g[j - 2**i];
+				p[j] = p[j] & p[j - 2**i];
+			end
+		end
+	end
+
+	assign CO = g;
+endmodule

techlibs/common/techmap.v

@@ -207,7 +207,7 @@ module _90_fa (A, B, C, X, Y);
 endmodule
 
 (* techmap_celltype = "$lcu" *)
-module _90_lcu (P, G, CI, CO);
+module _90_lcu_brent_kung (P, G, CI, CO);
 	parameter WIDTH = 2;
 
 	(* force_downto *)

tests/techmap/kogge-stone.ys

@@ -0,0 +1 @@
+test_cell -s 1711533949 -n 10 -map +/techmap.v -map +/choices/kogge-stone.v $lcu