$modfloor

$modfloor (A, B, Y)

Modulo/remainder of division with floored result (rounded towards negative infinity).

Invariant: $divfloor(A, B) * B + $modfloor(A, B) == A

Simulation model (Verilog)

Listing 322 simlib.v:1160

module \$modfloor (A, B, Y);

    parameter A_SIGNED = 0;
    parameter B_SIGNED = 0;
    parameter A_WIDTH = 0;
    parameter B_WIDTH = 0;
    parameter Y_WIDTH = 0;

    input [A_WIDTH-1:0] A;
    input [B_WIDTH-1:0] B;
    output [Y_WIDTH-1:0] Y;

    generate
        if (A_SIGNED && B_SIGNED) begin:BLOCK1
            localparam WIDTH = B_WIDTH >= Y_WIDTH ? B_WIDTH : Y_WIDTH;
            wire [WIDTH-1:0] B_buf, Y_trunc;
            assign B_buf = $signed(B);
            assign Y_trunc = $signed(A) % $signed(B);
            // flooring mod is the same as truncating mod for positive division results (A and B have
            // the same sign), as well as when there's no remainder.
            // For all other cases, they behave as `floor - trunc = B`
            assign Y = (A[A_WIDTH-1] == B[B_WIDTH-1]) || Y_trunc == 0 ? Y_trunc : $signed(B_buf) + $signed(Y_trunc);
        end else begin:BLOCK2
            // no difference between truncating and flooring for unsigned
            assign Y = A % B;
        end
    endgenerate

endmodule

Note

This page was auto-generated from the output of help $modfloor.