how to declare integer variable in verilog to keep track of a value to be used in multiple for loops? - verilog

Question

so I have this assignment to make a generic Wallace tree multiplier in Verilog, I wrote the code but didn't test it yet. my problem is in the 2nd stage where I am supposed to bypass some wires which couldn't fit in the current stage into the next stage and the results of the current stages are passed to next stage, so I made a simple for loop to that operation:
/*the logic in this module*/
generate
for(i = 0; i < size/3; i = i + 1)
begin
integer k = 0;
for(j = i; j < size-3; j = j + 3)
begin
CSAlike #(2 * size) parallelAdder(intermediateWires[k][i+1], intermediateWires[k+1][i+1], intermediateWires[j][i], intermediateWires[j+1][i], intermediateWires[j+2][i]);
k = k + 2;
end
/*assign the wires from this stage who couldn't fit into the current stage (0 or 1 or 2 wires)*/
for(l = size-(size%3); l < size; l = l + 1)
begin
assign intermediateWires[k][i+1] = intermediateWires[l][i];
k = k + 1;
end
end
endgenerate
well , ModelSim give me this error :
vlog -work work -stats=none {D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v}
Model Technology ModelSim - Intel FPGA Edition vlog 2020.1 Compiler 2020.02 Feb 28 2020
-- Compiling module multiplierTree
** Warning: D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(17): (vlog-2417) Multiple packed dimensions are not allowed.
-- Compiling module multiplyAllBits
** Warning: D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(46): (vlog-2417) Multiple packed dimensions are not allowed.
-- Compiling module addIntermedaiteWires
** Warning: D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(61): (vlog-2417) Multiple packed dimensions are not allowed.
** Warning: D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(67): (vlog-2417) Multiple packed dimensions are not allowed.
** Error: (vlog-13069) D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(92): near "=": syntax error, unexpected '='.
** Error: D:/PROJECTS/third year/first term/VLSI/mini project 2/codes (before synthesis)/verilog codes/multiplierTree.v(92): (vlog-13205) Syntax error found in the scope following 'k'. Is there a missing '::'?
and this is the full code:
/*resources :
https://www.youtube.com/watch?v=4-l_PGPog9o
https://www.youtube.com/watch?v=lcPIMvI57dM
*/
module multiplierTree #(parameter size = 32) (Res, OVF, A, B, clk);
/*the inputs to be multiplies*/
input [size-1:0] A, B;
input clk;
reg [size-1:0] A_in, B_in;
/*the outputs from the multiplier*/
output reg [(size-1)*2:0] Res;
output wire OVF; // overflow flag
/*intermediate wires for clean code*/
wire [size-1:0][(size-1)*2:0] wiresMultiplied;
wire [(size-1)*2:0] secondStage_Res, secondStage_carry, totalRes;
/*calling necessary modules*/
multiplyAllBits #(size) firstStage(wiresMultiplied, A_in, B_in);
addIntermedaiteWires #(size) secondStage(secondStage_Res, secondStage_carry, wiresMultiplied);
addResWithCarry #(2 * size) thirdStage(totalRes, secondStage_Res, secondStage_carry);
/*important assigns*/
assign OVF = Res[(size-1)*2] ^ A[size-1] & Res[(size-1)*2] ^ B[size-1] ;
/*the logic of the module*/
always#(posedge clk)
begin
A_in <= A;
B_in <= B;
Res <= totalRes;
end
endmodule
/*this is the first stage in the wallace tree*/
module multiplyAllBits #(parameter size = 32) (wiresMultiplied, A, B);
/*inputs to 1st stage of wallace tree*/
input wire [size-1:0] A, B;
/*outputs from the 1st stage*/
output wire [size-1:0][(size-1)*2:0] wiresMultiplied;
/*the actual logic in the circuit*/
genvar i, j;
generate
for(i = 0; i < size; i = i + 1)
assign wiresMultiplied[i] = ({size{B[i]}} & A) << i;
endgenerate
endmodule
/*this is the second stage in wallace tree*/
module addIntermedaiteWires #(parameter size = 32) (Res, carry, wiresMultiplied);
/*inputs coming from the 1st stage*/
input wire [size-1:0][(size-1)*2:0] wiresMultiplied;
/*outputs from 2nd stage*/
output wire [(size-1)*2:0] Res, carry;
/*intermediate wires for clean code*/
wire [size+1:0][size+1:0][(size-1)*2:0] intermediateWires;
genvar i, j, l;
/*important assigns*/
generate
for(i = 0; i < size; i = i + 1)
begin
assign intermediateWires[i][0] = wiresMultiplied[i];
end
endgenerate
/*getting the results*/
assign Res = intermediateWires[size+1][size+1];
assign calling = intermediateWires[size+1][size+1];
/*the logic in this module*/
generate
for(i = 0; i < size/3; i = i + 1)
begin
integer k = 0;
for(j = i; j < size-3; j = j + 3)
begin
CSAlike #(2 * size) parallelAdder(intermediateWires[k][i+1], intermediateWires[k+1][i+1], intermediateWires[j][i], intermediateWires[j+1][i], intermediateWires[j+2][i]);
k = k + 2;
end
/*assign the wires from this stage who couldn't fit into the current stage (0 or 1 or 2 wires)*/
for(l = size-(size%3); l < size; l = l + 1)
begin
assign intermediateWires[k][i+1] = intermediateWires[l][i];
k = k + 1;
end
end
endgenerate
endmodule
/*this is CSA look like to add parallely*/
module CSAlike #(parameter size = 32) (result, carry, A, B, C);
/*list of the inputs*/
input wire [size-1:0] A, B, C;
/*outputs*/
output wire [size-1:0] result, carry;
/*temp genvar*/
genvar i;
/*actual logic of parallel adders*/
for(i = 0; i < size; i = i + 1)
begin
FA fa(A[i], B[i], C[i], result[i], carry[i]);
end
endmodule
module addResWithCarry #(parameter size = 32) (Res_out, Res_in, carry_in);
/*list of the inputs*/
input wire [size-1:0] Res_in, carry_in;
/*outputs*/
output wire [size-1:0] Res_out;
/*using normar adder (verilog adder (adder plus))*/
assign Res_out = Res_in + carry_in;
endmodule
as it tells me that writing
k = k + 2;
is wrong inside the generate loop, but I don't know why, also it gave me some warnings telling me that writing
wire [size-1:0][(size-1)*2:0] wiresMultiplied;
has something wrong with it but IDK what's wrony with my code.

Answer 1

it tells me that writing
k = k + 2;
is wrong inside the generate loop, but I don't know why
It is a syntax error to make that assignment where you do in the code. It is an error for the same reason as this extreme simplification of your code is an error:
module dut;
integer k = 0;
k = k + 2;
endmodule
The integer declaration line is legal, but the other assignment line is illegal because it looks like you are trying to make a procedural assignment outside of a procedural block (like an always block).
When debugging problems with generate loops, it's always helps to "unroll" the loop and start writing out the code the long way. These loops are advanced syntax constructs and are tricky to use. Especially nested loops. Especially for students who are just starting to learn Verilog.