keccak: Add ifdef to keccak_iota for synth with yosys

Author: infinitymdm

src/keccak/keccak_iota.sv

@@ -10,13 +10,15 @@ module keccak_iota #(
         for (genvar i = 0; i < 5; i++) begin: sheet_select
             for (genvar j = 0; j < 5; j++) begin: lane_select
                 if ((i == 4) & (j == 4)) begin: apply_rc
-                    // If yosys supported streaming operators, we'd flip the rc bytes like so:
-                    // assign y[i][j] = x[i][j] ^ {<<8{rc}};
-                    // Unfortunately yosys doesn't support the {<<{}} streaming operator :(
-                    // Instead we have to swap bytes manually, adding this gross for loop
-                    for (genvar b = 0; b < w/8; b++) begin: swap_bytes
-                        assign y[i][j][8*(b+1)-1:8*b] = x[i][j][8*(b+1)-1:8*b] ^ rc[w-8*b-1:w-8*(b+1)];
-                    end
+                    `ifdef YOSYS
+                        // Unfortunately yosys doesn't support the {<<{}} streaming operator :(
+                        // Instead we have to swap bytes manually, adding this gross for loop
+                        for (genvar b = 0; b < w/8; b++) begin: swap_bytes
+                            assign y[i][j][8*(b+1)-1:8*b] = x[i][j][8*(b+1)-1:8*b] ^ rc[w-8*b-1:w-8*(b+1)];
+                        end
+                    `else
+                        assign y[i][j] = x[i][j] ^ {<<8{rc}};
+                    `endif
                 end else begin: passthrough
                     assign y[i][j] = x[i][j];
                 end