If I have a 32 bit two's complement number and I want to know what is the easiest way to know of two numbers are equal... what would be the fastest bitwise operator to know this? I know xor'ing both numbers and check if the results are zero works well... any other one's?
how about if a number is greater than 0?? I can check the 31'st bit to see if it's greater or equal to 0..but how about bgtz?
Contrary to your comments, '==' is part of Verilog, and unless my memory is a lot worse than usual tonight, it should synthesize just fine. Just for example, you could write something like:
// warning: untested, incomplete and utterly useless in any case.
// It's been a while since I wrote much Verilog, so my syntax is probably a bit off
// anyway (might well be more like VHDL than it should be).
//
module add_when_equal(clock, a, b, x, y, z);
input clock;
input [31:0] a, b, x, y;
output [31:0] z;
reg [31:0] a, b, x, y, z;
always begin: main
@(posedge clock);
if (a == b)
z <= x + y;
end
endmodule;
Verilog also supports the other comparison operators you'd normally expect (!=, <=, etc.). Synthesizers are fairly "smart", so something like x != 0 will normally synthesize to an N-input OR gate instead of a comparator.
if you can xor and then compare the result with zero then you can compare a result with some value and if you can compare something to a value then you can just compare the two values without using an xor and a 32 bit zero.
// this should work as comparator for Equality
wire [31:0] Cmp1, Cmp2;
wire Equal;
assign Equal = &{Cmp1 ~^ Cmp2}; // using XNOR
assign Equal = ~|{Cmp1 ^ Cmp2}; // using XOR