Question

Good coding convention says that we should use blocking assignments in a combinational block, and non-blocking assignments in a sequential block. I want to use the ++ operator in a combinatorial block, but I don't know if it is blocking. So is this code:

input [3:0] some_bus;
logic [2:0] count_ones;
always_comb begin
  count_ones = '0;
  for(int i=0; i<4; i++) begin
    if(some_bus[i])
      count_ones++;
  end
end

equivalent to this:

input [3:0] some_bus;
logic [2:0] count_ones;
always_comb begin
  count_ones = '0;
  for(int i=0; i<4; i++) begin
    if(some_bus[i])
      count_ones = count_ones + 1;
  end
end

or this:

input [3:0] some_bus;
logic [2:0] count_ones;
always_comb begin
  count_ones = '0;
  for(int i=0; i<4; i++) begin
    if(some_bus[i])
      count_ones <= count_ones + 1;
  end
end

I did look in the 1800-2012 standard but could not figure it out. An answer that points me to the appropriate section in the standard would be appreciated.

Was it helpful?

Solution

According to section 11.4.2 of IEEE Std 1800-2012, it is blocking.

SystemVerilog includes the C increment and decrement assignment operators ++i , --i , i++ , and i-- . These do not need parentheses when used in expressions. These increment and decrement assignment operators behave as blocking assignments.

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