Merge pull request #2347 from YosysHQ/mwk/techmap-shift-fixes

techmap/shift_shiftx: Remove the "shiftx2mux" special path.

1 files changed, 35 insertions, 67 deletions

diff --git a/techlibs/common/techmap.v b/techlibs/common/techmap.v
index 03c27d49d..2ab28e6e6 100644
--- a/techlibs/common/techmap.v
+++ b/techlibs/common/techmap.v
@@ -143,78 +143,46 @@ module _90_shift_shiftx (A, B, Y);
 	localparam extbit = _TECHMAP_CELLTYPE_ == "$shift" ? 1'b0 : 1'bx;
 	wire a_padding = _TECHMAP_CELLTYPE_ == "$shiftx" ? extbit : (A_SIGNED ? A[A_WIDTH-1] : 1'b0);
 
-	generate
-`ifndef NO_LSB_FIRST_SHIFT_SHIFTX
-		// If $shift/$shiftx only shifts in units of Y_WIDTH
-		//   (a common pattern created by pmux2shiftx)
-		//   which is checked by ensuring that all that
-		//   the appropriate LSBs of B are constant zero,
-		//   then we can decompose LSB first instead of
-		//   MSB first
-		localparam CLOG2_Y_WIDTH = $clog2(Y_WIDTH);
-		if (B_WIDTH > CLOG2_Y_WIDTH+1 &&
-			_TECHMAP_CONSTMSK_B_[CLOG2_Y_WIDTH-1:0] == {CLOG2_Y_WIDTH{1'b1}} &&
-			_TECHMAP_CONSTVAL_B_[CLOG2_Y_WIDTH-1:0] == {CLOG2_Y_WIDTH{1'b0}}) begin
-			// Halve the size of $shift/$shiftx by $mux-ing A according to
-			//   the LSB of B, after discarding the zeroed bits
-			localparam Y_WIDTH2 = 2**CLOG2_Y_WIDTH;
-			localparam entries = (A_WIDTH+Y_WIDTH-1)/Y_WIDTH2;
-			localparam len = Y_WIDTH2 * ((entries+1)/2);
-			wire [len-1:0] AA;
-			wire [(A_WIDTH+Y_WIDTH2+Y_WIDTH-1)-1:0] Apad = {{(Y_WIDTH2+Y_WIDTH-1){a_padding}}, A};
-			genvar i;
-			for (i = 0; i < A_WIDTH; i=i+Y_WIDTH2*2)
-				assign AA[i/2 +: Y_WIDTH2] = B[CLOG2_Y_WIDTH] ? Apad[i+Y_WIDTH2 +: Y_WIDTH2] : Apad[i +: Y_WIDTH2];
-			wire [B_WIDTH-2:0] BB = {B[B_WIDTH-1:CLOG2_Y_WIDTH+1], {CLOG2_Y_WIDTH{1'b0}}};
-			if (_TECHMAP_CELLTYPE_ == "$shift")
-				$shift #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH(len), .B_WIDTH(B_WIDTH-1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(AA), .B(BB), .Y(Y));
-			else
-				$shiftx #(.A_SIGNED(A_SIGNED), .B_SIGNED(B_SIGNED), .A_WIDTH(len), .B_WIDTH(B_WIDTH-1), .Y_WIDTH(Y_WIDTH)) _TECHMAP_REPLACE_ (.A(AA), .B(BB), .Y(Y));
-		end
-		else
-`endif
-		begin
-			localparam BB_WIDTH = `MIN($clog2(`MAX(A_WIDTH, Y_WIDTH)) + (B_SIGNED ? 2 : 1), B_WIDTH);
-			localparam WIDTH = `MAX(A_WIDTH, Y_WIDTH) + (B_SIGNED ? 2**(BB_WIDTH-1) : 0);
+	localparam BB_WIDTH = `MIN($clog2(`MAX(A_WIDTH, Y_WIDTH)) + (B_SIGNED ? 2 : 1), B_WIDTH);
+	localparam WIDTH = `MAX(A_WIDTH, Y_WIDTH) + (B_SIGNED ? 2**(BB_WIDTH-1) : 0);
 
-			wire [1023:0] _TECHMAP_DO_00_ = "proc;;";
-			wire [1023:0] _TECHMAP_DO_01_ = "CONSTMAP; opt_muxtree; opt_expr -mux_undef -mux_bool -fine;;;";
+	wire [1023:0] _TECHMAP_DO_00_ = "proc;;";
+	wire [1023:0] _TECHMAP_DO_01_ = "CONSTMAP; opt_muxtree; opt_expr -mux_undef -mux_bool -fine;;;";
 
-			integer i;
-			(* force_downto *)
-			reg [WIDTH-1:0] buffer;
-			reg overflow;
+	integer i;
+	(* force_downto *)
+	reg [WIDTH-1:0] buffer;
+	reg overflow;
 
-			always @* begin
-				overflow = 0;
+	always @* begin
+		overflow = 0;
+		buffer = {WIDTH{extbit}};
+		buffer[Y_WIDTH-1:0] = {Y_WIDTH{a_padding}};
+		buffer[A_WIDTH-1:0] = A;
+
+		if (B_WIDTH > BB_WIDTH) begin
+			if (B_SIGNED) begin
+				for (i = BB_WIDTH; i < B_WIDTH; i = i+1)
+					if (B[i] != B[BB_WIDTH-1])
+						overflow = 1;
+			end else
+				overflow = |B[B_WIDTH-1:BB_WIDTH];
+			if (overflow)
 				buffer = {WIDTH{extbit}};
-				buffer[Y_WIDTH-1:0] = {Y_WIDTH{a_padding}};
-				buffer[A_WIDTH-1:0] = A;
-
-				if (B_WIDTH > BB_WIDTH) begin
-					if (B_SIGNED) begin
-						for (i = BB_WIDTH; i < B_WIDTH; i = i+1)
-							if (B[i] != B[BB_WIDTH-1])
-								overflow = 1;
-					end else
-						overflow = |B[B_WIDTH-1:BB_WIDTH];
-					if (overflow)
-						buffer = {WIDTH{extbit}};
-				end
-
-				for (i = BB_WIDTH-1; i >= 0; i = i-1)
-					if (B[i]) begin
-						if (B_SIGNED && i == BB_WIDTH-1)
-							buffer = {buffer, {2**i{extbit}}};
-						else if (2**i < WIDTH)
-							buffer = {{2**i{extbit}}, buffer[WIDTH-1 : 2**i]};
-						else
-							buffer = {WIDTH{extbit}};
-					end
-			end
-			assign Y = buffer;
 		end
-	endgenerate
+
+		if (B_SIGNED && B[BB_WIDTH-1])
+			buffer = {buffer, {2**(BB_WIDTH-1){extbit}}};
+
+		for (i = 0; i < (B_SIGNED ? BB_WIDTH-1 : BB_WIDTH); i = i+1)
+			if (B[i]) begin
+				if (2**i < WIDTH)
+					buffer = {{2**i{extbit}}, buffer[WIDTH-1 : 2**i]};
+				else
+					buffer = {WIDTH{extbit}};
+			end
+	end
+	assign Y = buffer;
 endmodule