Subversion Repositories hive

/*

--------------------------------------------------------------------------------

--

-- Module : functions.h

--

--------------------------------------------------------------------------------

--

-- Function:

-- - A bunch of functions for a stack processor.

--

-- Instantiates:

-- - Nothing.

--

--------------------------------------------------------------------------------

*/

        /*

        ---------------

        -- functions --

        ---------------

        */

        // returns safe ceiling value of log2(n)

        // (for vector sizing we never want less than 1)

        // examples: 

        // clog2(0 thru 2)  = 1,

        // clog2(3 & 4)     = 2,

        // clog2(5 thru 8)  = 3,

        // clog2(9 thru 16) = 4, etc.

        function integer clog2;

        input integer in;

                begin

                        clog2 = 1;

                        while ( in > 2 ) begin

                                in = ( in + 1 ) / 2;

                                clog2 = clog2 + 1;

                        end

                end

        endfunction

        // flip 32 bit value

        function [31:0] flip_32;

        input [31:0] in;

        integer i;

                begin

                        for ( i=0; i<32; i=i+1 ) begin

                                flip_32[i] = in[31-i];

                        end

                end

        endfunction

        // return leading zero count of 32 bit value

        // examples:

        // lzc_32(32'b000...000) = 32

        // lzc_32(32'b000...001) = 31

        // lzc_32(32'b000...01x) = 30

        // ...

        // lzc_32(32'b001...xxx) = 2

        // lzc_32(32'b01x...xxx) = 1

        // lzc_32(32'b1xx...xxx) = 0

        function [5:0] lzc_32;

        input [31:0] in;

        integer j, hi_1, all_0;

                begin

                        hi_1 = 31;

                        all_0 = 1;

                        // priority encoder (find MSB 1 position)

                        for ( j = 0; j < 32; j = j + 1 ) begin

                                if ( in[j] ) begin

                                        hi_1 = j;

                                        all_0 = 0;

                                end

                        end

                end

                // invert & concat to get zero count

                lzc_32 = { all_0[0], ~hi_1[4:0] };

        endfunction

        // returns the max of 2 integers

        function integer max_of_2;

        input integer a, b;

                begin

                        if ( a > b ) begin

                                max_of_2 = a;

                        end else begin

                                max_of_2 = b;

                        end

                end

        endfunction