/*

 * Create a contiguous bitmask starting at bit position @l and ending at

 * position @h. For example

 * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.

 */

#define GENMASK(h, l) \

	(((~UL(0)) - (UL(1) << (l)) + 1) & \            ||1

	 (~UL(0) >> (BITS_PER_LONG - 1 - (h))))   ||2

Exp. (6,4) of 0x1111 1111

1-->0x1111 1111 - (0x1<<4) = 0x1110 1111  + 1 = 0x1111 0000

2-->0x1111 1111 >> (8-1-6) = 0x0111 1111

1&2 = 0x0111 0000

/*

 * Bitfield access macros

 *

 * FIELD_{GET,PREP} macros take as first parameter shifted mask

 * from which they extract the base mask and shift amount.

 * Mask must be a compilation time constant.

 *

 * Example:

 *

 *  #define REG_FIELD_A  GENMASK(6, 0)

 *  #define REG_FIELD_B  BIT(7)

 *  #define REG_FIELD_C  GENMASK(15, 8)

 *  #define REG_FIELD_D  GENMASK(31, 16)

 *

 * Get:

 *  a = FIELD_GET(REG_FIELD_A, reg);

 *  b = FIELD_GET(REG_FIELD_B, reg);

 *

 * Set:

 *  reg = FIELD_PREP(REG_FIELD_A, 1) |

 *	  FIELD_PREP(REG_FIELD_B, 0) |

 *	  FIELD_PREP(REG_FIELD_C, c) |

 *	  FIELD_PREP(REG_FIELD_D, 0x40);

 *

 * Modify:

 *  reg &= ~REG_FIELD_C;

 *  reg |= FIELD_PREP(REG_FIELD_C, c);

 */

#define __bf_shf(x) (__builtin_ffsll(x) - 1)

#include <stdio.h>

#define UL (unsigned long)

#define GENMASK(h, l, H, L)     \

        ({typeof(h) H = (h);    \

        typeof(l) L = (l);      \

        (((~UL(0)) >>(L)<< (L)) & \

        (~UL(0) >> (64 - 1 - (H))));})

#define GENMASK_OLD(h, l)     \

        (((~UL(0)) >>(l)<< (l)) & \

        (~UL(0) >> (64 - 1 - (h))))

void main(){

        int i = 6, j = 4;

        printf("output:%lx\n", GENMASK_OLD(6,4));

        printf("output:%lx\n", GENMASK_OLD(i++,j++));

        printf("output:%lx\n", GENMASK(i++,j++, H, L));

}

#include <stdio.h>

#define UL (unsigned long)

#define BITS_PER_LONG sizeof(unsigned long)

#define GENMASK_NEW(h, l, H, L)     \

        ({typeof(h) H = (h);    \

        typeof(l) L = (l);      \

        (((~UL(0)) >>(L)<< (L)) & \

        (~UL(0) >> (64 - 1 - (H))));})

#define GENMASK(h, l) \

    (((~UL(0)) - (UL(1) << (l)) + 1) & \

     (~UL(0) >> (64 - 1 - (h))))

#define GENMASK_YIN(h, l) \

    (((~UL(0))>>(64-1-(h))) & \

     (~UL(0))>>(l)<<(l))

void main(){

        unsigned long loop1 = 1000;

        unsigned long loop2 = 10000000;

        int i = 6, j=4;

#if 0

        printf("output:%lx\n", GENMASK_NEW(i++,j++, H, L));

        i = 6; j = 4;

        printf("output:%lx\n", GENMASK_NEW(++i,++j, H, L));

        //org:

        i = 6; j = 4;

        printf("output:%lx\n", GENMASK(i++,j++));

        i = 6; j = 4;

        printf("output:%lx\n", GENMASK(++i,++j));

        return;

#endif

        //printf("GENMASK(i+1, j+1):%lx\n", GENMASK(i+1, j+1));

        printf("GENMASK_NEW(i+1, j+1):%lx\n", GENMASK_NEW(i+1, j+1,H,L));

        while(loop1--){

                loop2 = 10000000;

                while(loop2--){

                        //printf("%lx\n", GENMASK(6, 4));

                        //GENMASK(i+1, j+1);

                        //GENMASK_YIN(i, j);

                        GENMASK_NEW(i,j, H, L);

                }

        }

        //printf("hello%ld, BITS_PER_LONG:%ld\n", sizeof UL, BITS_PER_LONG);

}