From: David Shah <dave@ds0.me>
Date: Thu, 18 Jul 2019 10:33:37 +0000 (+0100)
Subject: mul2dsp: Lower partial products always have unsigned inputs
X-Git-Tag: working-ls180~1039^2~346^2
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=16b0ccf04ca83d76f9bd182e125dd75fa838753a;p=yosys.git

mul2dsp: Lower partial products always have unsigned inputs

Signed-off-by: David Shah <dave@ds0.me>
---

diff --git a/techlibs/common/mul2dsp.v b/techlibs/common/mul2dsp.v
index 7344bc5fe..31469ddeb 100644
--- a/techlibs/common/mul2dsp.v
+++ b/techlibs/common/mul2dsp.v
@@ -92,20 +92,25 @@ module \$__mul_gen (A, B, Y);
 	genvar i;
 	generate
 		if (A_WIDTH > `DSP_A_MAXWIDTH) begin
-			localparam n_floored = A_WIDTH/`DSP_A_MAXWIDTH;
-			localparam n = n_floored + (n_floored*`DSP_A_MAXWIDTH < A_WIDTH ? 1 : 0);
+`ifdef DSP_A_SIGNEDONLY
+			localparam sign_headroom = 1;
+`else 	
+			localparam sign_headroom = 0;
+`endif
+			localparam n_floored = A_WIDTH/(`DSP_A_MAXWIDTH - sign_headroom);
+			localparam n = n_floored + (n_floored*(`DSP_A_MAXWIDTH - sign_headroom) < A_WIDTH ? 1 : 0);
 			wire [`DSP_A_MAXWIDTH+B_WIDTH-1:0] partial [n-1:1];
 			wire [Y_WIDTH-1:0] partial_sum [n-2:0];
 			localparam int_yw = `MIN(Y_WIDTH, B_WIDTH+`DSP_A_MAXWIDTH);
 
 			\$__mul_gen #(
-				.A_SIGNED(A_SIGNED),
+				.A_SIGNED(0),
 				.B_SIGNED(B_SIGNED),
 				.A_WIDTH(`DSP_A_MAXWIDTH),
 				.B_WIDTH(B_WIDTH),
 				.Y_WIDTH(int_yw)
 			) mul_slice_first (
-				.A(A[`DSP_A_MAXWIDTH-1:0]),
+				.A({{sign_headroom{1'b0}}, A[`DSP_A_MAXWIDTH-sign_headroom-1:0]}),
 				.B(B),
 				.Y(partial_sum[0][int_yw-1:0])
 			);
@@ -114,73 +119,78 @@ module \$__mul_gen (A, B, Y);
 
 			for (i = 1; i < n-1; i=i+1) begin:slice
 				\$__mul_gen #(
-					.A_SIGNED(A_SIGNED),
+					.A_SIGNED(0),
 					.B_SIGNED(B_SIGNED),
 					.A_WIDTH(`DSP_A_MAXWIDTH),
 					.B_WIDTH(B_WIDTH),
 					.Y_WIDTH(int_yw)
 				) mul_slice (
-					.A(A[(i+1)*`DSP_A_MAXWIDTH-1:i*`DSP_A_MAXWIDTH]),
+					.A({{sign_headroom{1'b0}}, A[(i+1)*(`DSP_A_MAXWIDTH-sign_headroom)-1:i*(`DSP_A_MAXWIDTH-sign_headroom)]}),
 					.B(B),
 					.Y(partial[i][int_yw-1:0])
 				);
 				//assign partial_sum[i] = (partial[i] << i*`DSP_A_MAXWIDTH) + partial_sum[i-1];
 				assign partial_sum[i] = {
 					partial[i][int_yw-1:0]
-					+ partial_sum[i-1][Y_WIDTH-1:(i*`DSP_A_MAXWIDTH)],
-					partial_sum[i-1][(i*`DSP_A_MAXWIDTH)-1:0]
+					+ partial_sum[i-1][Y_WIDTH-1:(i*(`DSP_A_MAXWIDTH-sign_headroom))],
+					partial_sum[i-1][(i*(`DSP_A_MAXWIDTH-sign_headroom))-1:0]
 				};
 			end
 
 			\$__mul_gen #(
 				.A_SIGNED(A_SIGNED),
 				.B_SIGNED(B_SIGNED),
-				.A_WIDTH(A_WIDTH-(n-1)*`DSP_A_MAXWIDTH),
+				.A_WIDTH(A_WIDTH-(n-1)*(`DSP_A_MAXWIDTH-sign_headroom)),
 				.B_WIDTH(B_WIDTH),
-				.Y_WIDTH(`MIN(Y_WIDTH, A_WIDTH-(n-1)*`DSP_A_MAXWIDTH+B_WIDTH)),
+				.Y_WIDTH(`MIN(Y_WIDTH, A_WIDTH-(n-1)*(`DSP_A_MAXWIDTH-sign_headroom)+B_WIDTH)),
 			) mul_slice_last (
-				.A(A[A_WIDTH-1:(n-1)*`DSP_A_MAXWIDTH]),
+				.A(A[A_WIDTH-1:(n-1)*(`DSP_A_MAXWIDTH-sign_headroom)]),
 				.B(B),
-				.Y(partial[n-1][`MIN(Y_WIDTH, A_WIDTH-(n-1)*`DSP_A_MAXWIDTH+B_WIDTH)-1:0])
+				.Y(partial[n-1][`MIN(Y_WIDTH, A_WIDTH-(n-1)*(`DSP_A_MAXWIDTH-sign_headroom)+B_WIDTH)-1:0])
 			);
 			//assign Y = (partial[n-1] << (n-1)*`DSP_A_MAXWIDTH) + partial_sum[n-2];
 			assign Y = {
-				partial[n-1][`MIN(Y_WIDTH, A_WIDTH-(n-1)*`DSP_A_MAXWIDTH+B_WIDTH):0]
-				+ partial_sum[n-2][Y_WIDTH-1:((n-1)*`DSP_A_MAXWIDTH)],
-				partial_sum[n-2][((n-1)*`DSP_A_MAXWIDTH)-1:0]
+				partial[n-1][`MIN(Y_WIDTH, A_WIDTH-(n-1)*(`DSP_A_MAXWIDTH-sign_headroom)+B_WIDTH):0]
+				+ partial_sum[n-2][Y_WIDTH-1:((n-1)*(`DSP_A_MAXWIDTH-sign_headroom))],
+				partial_sum[n-2][((n-1)*(`DSP_A_MAXWIDTH-sign_headroom))-1:0]
 			};
 		end
 		else if (B_WIDTH > `DSP_B_MAXWIDTH) begin
-			localparam n_floored = B_WIDTH/`DSP_B_MAXWIDTH;
-			localparam n = n_floored + (n_floored*`DSP_B_MAXWIDTH < B_WIDTH ? 1 : 0);
+`ifdef DSP_B_SIGNEDONLY
+			localparam sign_headroom = 1;
+`else 	
+			localparam sign_headroom = 0;
+`endif
+			localparam n_floored = B_WIDTH/(`DSP_B_MAXWIDTH - sign_headroom);
+			localparam n = n_floored + (n_floored*(`DSP_B_MAXWIDTH - sign_headroom) < B_WIDTH ? 1 : 0);
 			wire [A_WIDTH+`DSP_B_MAXWIDTH-1:0] partial [n-1:1];
 			wire [Y_WIDTH-1:0] partial_sum [n-2:0];
 			localparam int_yw = `MIN(Y_WIDTH, A_WIDTH+`DSP_B_MAXWIDTH);
 
 			\$__mul_gen #(
 				.A_SIGNED(A_SIGNED),
-				.B_SIGNED(B_SIGNED),
+				.B_SIGNED(0),
 				.A_WIDTH(A_WIDTH),
 				.B_WIDTH(`DSP_B_MAXWIDTH),
 				.Y_WIDTH(int_yw)
 			) mul_first (
 				.A(A),
-				.B(B[`DSP_B_MAXWIDTH-1:0]),
+				.B({{sign_headroom{1'b0}}, B[(`DSP_B_MAXWIDTH - sign_headroom)-1:0]}),
 				.Y(partial_sum[0][int_yw-1:0])
 			);
 			if (Y_WIDTH > int_yw)
-				assign partial_sum[0][Y_WIDTH-1:A_WIDTH+`DSP_B_MAXWIDTH]=0;
+				assign partial_sum[0][Y_WIDTH-1:int_yw]=0;
 
 			for (i = 1; i < n-1; i=i+1) begin:slice
 				\$__mul_gen #(
 					.A_SIGNED(A_SIGNED),
-					.B_SIGNED(B_SIGNED),
+					.B_SIGNED(0),
 					.A_WIDTH(A_WIDTH),
 					.B_WIDTH(`DSP_B_MAXWIDTH),
 					.Y_WIDTH(int_yw)
 				) mul (
 					.A(A),
-					.B(B[(i+1)*`DSP_B_MAXWIDTH-1:i*`DSP_B_MAXWIDTH]),
+					.B({{sign_headroom{1'b0}}, B[(i+1)*(`DSP_B_MAXWIDTH - sign_headroom)-1:i*(`DSP_B_MAXWIDTH - sign_headroom)]}),
 					.Y(partial[i][int_yw-1:0])
 				);
 				//assign partial_sum[i] = (partial[i] << i*`DSP_B_MAXWIDTH) + partial_sum[i-1];
@@ -191,8 +201,8 @@ module \$__mul_gen (A, B, Y);
 				//	partial_sum[i-1][A_WIDTH+((i-1)*`DSP_B_MAXWIDTH):0]
 				assign partial_sum[i] = {
 					partial[i][int_yw-1:0]
-					+ partial_sum[i-1][Y_WIDTH-1:(i*`DSP_B_MAXWIDTH)],
-					partial_sum[i-1][(i*`DSP_B_MAXWIDTH)-1:0] 
+					+ partial_sum[i-1][Y_WIDTH-1:(i*(`DSP_B_MAXWIDTH - sign_headroom))],
+					partial_sum[i-1][(i*(`DSP_B_MAXWIDTH - sign_headroom))-1:0] 
 				};
 			end
 
@@ -200,12 +210,12 @@ module \$__mul_gen (A, B, Y);
 				.A_SIGNED(A_SIGNED),
 				.B_SIGNED(B_SIGNED),
 				.A_WIDTH(A_WIDTH),
-				.B_WIDTH(B_WIDTH-(n-1)*`DSP_B_MAXWIDTH),
-				.Y_WIDTH(`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*`DSP_B_MAXWIDTH))
+				.B_WIDTH(B_WIDTH-(n-1)*(`DSP_B_MAXWIDTH - sign_headroom)),
+				.Y_WIDTH(`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*(`DSP_B_MAXWIDTH - sign_headroom)))
 			) mul_last (
 				.A(A),
-				.B(B[B_WIDTH-1:(n-1)*`DSP_B_MAXWIDTH]),
-				.Y(partial[n-1][`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*`DSP_B_MAXWIDTH)-1:0])
+				.B(B[B_WIDTH-1:(n-1)*(`DSP_B_MAXWIDTH - sign_headroom)]),
+				.Y(partial[n-1][`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*(`DSP_B_MAXWIDTH - sign_headroom))-1:0])
 			);
 			// AMD: this came comment out -- looks closer to right answer
 			//assign Y = (partial[n-1] << (n-1)*`DSP_B_MAXWIDTH) + partial_sum[n-2];
@@ -215,9 +225,9 @@ module \$__mul_gen (A, B, Y);
 			//	partial[n-1][`DSP_B_MAXWIDTH-1:0] + partial_sum[n-2][A_WIDTH+((n-1)*`DSP_B_MAXWIDTH)-1:A_WIDTH+((n-2)*`DSP_B_MAXWIDTH)],
 			//	partial_sum[n-2][A_WIDTH+((n-2)*`DSP_B_MAXWIDTH):0]
 			assign Y = {
-				partial[n-1][`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*`DSP_B_MAXWIDTH)-1:0]
-				+ partial_sum[n-2][Y_WIDTH-1:((n-1)*`DSP_B_MAXWIDTH)],
-				partial_sum[n-2][((n-1)*`DSP_B_MAXWIDTH)-1:0]
+				partial[n-1][`MIN(Y_WIDTH, A_WIDTH+B_WIDTH-(n-1)*(`DSP_B_MAXWIDTH - sign_headroom))-1:0]
+				+ partial_sum[n-2][Y_WIDTH-1:((n-1)*(`DSP_B_MAXWIDTH - sign_headroom))],
+				partial_sum[n-2][((n-1)*(`DSP_B_MAXWIDTH - sign_headroom))-1:0]
 			};
 		end
 		else begin