Modifications made

This project purpose is to modify and adapt yafpgatetris code to make it friendly to current version of Yosys framework. Below is a description of major modifications we had to implement.

memories

Most modifications refer to lack of support for multi-dimentional and composite data types in Yosys. One and only multi-dimentional data type supported should be written like this:

  reg [3:0] mem [0:15] [0:15];
  always @(posedge clk) begin
    y <= mem[a][b];
    mem[a][b] <= c;
  end

This memory type is very restrictive. Particularly, memories can't be sliced. This forced us to flatten almost all SystemVerilog packed arrays to one-dimentional Verilog-style vectors. That is not a rewarding job.

Limited support for multi-dimentional and composite data types decreases relevance of using Yosys for larger projects.

enums

typedef enum { EV_LEFT, 
               EV_RIGHT, 
               EV_DOWN,
               EV_ROTATE,
               EV_NEW_GAME } user_event_t;

changed to

// user_events
`define EV_DOWN 3'b000
`define EV_RIGHT 3'b001
`define EV_LEFT 3'b010
`define EV_ROTATE 3'b011
`define EV_NEW_GAME 3'b100

typedefs

typedef struct packed {
  logic        [3:0][0:3][0:3]                 data;
  logic        [`TETRIS_COLORS_WIDTH-1:0]      color;
  logic        [1:0]                           rotation;
  logic signed [`FIELD_COL_CNT_WIDTH:0]        x;
  logic signed [`FIELD_ROW_CNT_WIDTH:0]        y;
} block_info_t;

changed to

// next block info
logic [4*4*4-1:0] next_block_data;
logic [`TETRIS_COLORS_WIDTH-1:0] next_block_color;
logic [1:0] next_block_rotation;
logic signed [`FIELD_COL_CNT_WIDTH:0] next_block_x;
logic signed [`FIELD_ROW_CNT_WIDTH:0] next_block_y;

SystemVerilog all-zeros shortcut

field_clean = '0;

changed to

field_clean = 0;

inline integer declarations

  for( integer row = 0; row < `FIELD_EXT_ROW_CNT; row++ ) begin
    for( integer col = 0; col < `FIELD_EXT_COL_CNT; col++ ) begin

changed to

  integer row;
  integer col;
  for( row = 0; row < `FIELD_EXT_ROW_CNT; row = row+1  ) begin
    for( col = 0; col < `FIELD_EXT_COL_CNT; col = col+1 ) begin

arithmetic operators

bcd_o[ (bcd*4+3):(bcd*4+0) ] += 4'd3;

changed to

bcd_o[ (bcd*4+3):(bcd*4+0) ] += bcd_o[ (bcd*4+3):(bcd*4+0) ] + 4'd3;