verilator/test_regress/t/t_forceable_var.v
Geza Lore 745605efe3
Fix DFG removing forceable signals (#4942)
DFG could remove forceable signals by replacing them with their
in-design driver. This is a bit of a pain to prevent, and ideally the
forcing transform should happen before DFG, but implementing it there is
a pain due to having to rewrite ports based on direction.  This is an
attempted fix in DFG. More cases might remain.
2024-03-03 16:22:41 +00:00

104 lines
2.4 KiB
Systemverilog

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain, for
// any use, without warranty, 2022 by Geza Lore.
// SPDX-License-Identifier: CC0-1.0
`define stop $stop
`define checkh(gotv,expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d: got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0)
module t (
input wire clk,
input wire rst,
output reg [31:0] cyc
);
always @(posedge clk) begin
if (rst) begin
cyc <= 0;
end else begin
cyc <= cyc +1;
end
end
reg tmp_1;
reg [7:0] tmp_8;
always @(posedge clk) begin
if (rst) begin
tmp_1 <= 0;
tmp_8 <= 0;
end else begin
tmp_1 <= cyc[0];
tmp_8 <= cyc[1 +: 8];
end
end
`ifdef CMT
reg var_1 /* verilator forceable */;
reg [7:0] var_8 /* verilator forceable */;
`else
reg var_1;
reg [7:0] var_8;
`endif
always @* var_1 = tmp_1;
always @* var_8 = tmp_8;
reg obs_1;
reg [7:0] obs_8;
always @* obs_1 = var_1;
always @* obs_8 = var_8;
always @ (posedge clk) begin
$display("%d: %x %x", cyc, obs_8, obs_1);
if (!rst) begin
case (cyc)
0: begin // Reset values
`checkh (obs_1, 0);
`checkh (obs_8, 0);
end
13: begin
`checkh (obs_1, 1);
`checkh ({1'b0, obs_8}, (cyc[0 +: 9] - 1) >> 1);
end
14: begin
`checkh (obs_1, 1);
`checkh (obs_8, 8'hf5);
end
15: begin
`checkh (obs_1, 0);
`checkh (obs_8, 8'hf5);
end
16, 17: begin
`checkh (obs_1, 0);
`checkh (obs_8, 8'h5f);
end
18: begin
`checkh (obs_1, ~cyc[0]);
`checkh (obs_8, 8'h5f);
end
20, 21: begin
`checkh (obs_1, 1);
`checkh (obs_8, 8'h5a);
end
22, 23: begin
`checkh (obs_1, 0);
`checkh (obs_8, 8'ha5);
end
default: begin
`checkh ({obs_8, obs_1}, cyc[0 +: 9] - 1);
end
endcase
end
if (cyc == 30) begin
$write("*-* All Finished *-*\n");
$finish;
end
end
endmodule