I need some help from those of you who have expensive simulators.
The attached program is from PR#748. The question I need resolved
is whether the signed operands are sign extended always, or only
when the whole expression is signed. So output from big name tools
would help me resolve this.
Thanks,
--
Steve Williams "The woods are lovely, dark and deep.
steve at icarus.com But I have promises to keep,
http://www.icarus.com and lines to code before I sleep,
http://www.picturel.com And lines to code before I sleep."
module signed_multiplier_test;
reg signed [5:0] s_prod;
wire [2:0] u_pos_two = 3'b010;
wire signed [2:0] s_pos_two = 3'sb010;
wire signed [2:0] s_neg_two = 3'sb110;
wire s = 1'b1; // flag to indicate signed
wire u = 1'b0; // flag to indicate unsigned
initial begin
// unsigned positive two as first argument of multiply
#1 s_prod = u_pos_two * u_pos_two;
check_mult(1,u,u_pos_two,u,u_pos_two,s_prod,6'sb000100);
#1 s_prod = u_pos_two * s_pos_two;
check_mult(2,u,u_pos_two,s,s_pos_two,s_prod,6'sb000100);
// This makes an unsigned result.
#1 s_prod = u_pos_two * s_neg_two;
check_mult(3,u,u_pos_two,s,s_neg_two,s_prod,6'sb001100);
// signed positive two as first argument of multiply
#1 s_prod = s_pos_two * u_pos_two;
check_mult(4,s,s_pos_two,u,u_pos_two,s_prod,6'sb000100);
#1 s_prod = s_pos_two * s_pos_two;
check_mult(5,s,s_pos_two,s,s_pos_two,s_prod,6'sb000100);
#1 s_prod = s_pos_two * s_neg_two;
check_mult(6,s,s_pos_two,s,s_neg_two,s_prod,6'sb111100);
// signed negative two as first argument of multiply
// This makes an unsigned result.
#1 s_prod = s_neg_two * u_pos_two;
check_mult(7,s,s_neg_two,u,u_pos_two,s_prod,6'sb001100);
#1 s_prod = s_neg_two * s_pos_two;
check_mult(8,s,s_neg_two,s,s_pos_two,s_prod,6'sb111100);
#1 s_prod = s_neg_two * s_neg_two;
check_mult(9,s,s_neg_two,s,s_neg_two,s_prod,6'sb000100);
$finish;
end
task check_mult;
input [31:0] idx;
input signeda;
input [ 2:0] arga;
input signedb;
input [ 2:0] argb;
input [ 5:0] result,expected;
if (result !== expected) begin
$write("failed: test %0d, ",idx);
if (signeda)
$write("3'sb%b",arga);
else
$write("3 'b%b",arga);
$write(" * ");
if (signedb)
$write("3'sb%b",argb);
else
$write("3 'b%b",argb);
$write(" = 6'sb%b (expected 6'sb%b)\n",result,expected);
end
endtask
endmodule
