[Bug tree-optimization/122569] Fails to pattern match ctz/clz from DeBruijn

[fxue at os dot amperecomputing.com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122569

--- Comment #3 from Feng Xue <fxue at os dot amperecomputing.com> ---
Here is the real case:

void get_msb_index(unsigned long *result, uint64_t value)
{
    static const unsigned long deBruijnTable64[64] = { 63, 0,  58, 1,  59, 47,
53, 2,  60, 39, 48, 27, 54,
                                                       33, 42, 3,  61, 51, 37,
40, 49, 18, 28, 20, 55, 30,
                                                       34, 11, 43, 14, 22, 4, 
62, 57, 46, 52, 38, 26, 32,
                                                       41, 50, 36, 17, 19, 29,
10, 13, 21, 56, 45, 25, 31,
                                                       35, 16, 9,  12, 44, 24,
15, 8,  23, 7,  6,  5 };

    value |= value >> 1;
    value |= value >> 2;
    value |= value >> 4;
    value |= value >> 8;
    value |= value >> 16;
    value |= value >> 32;

    *result = deBruijnTable64[((value - (value >> 1)) *
uint64_t(0x07EDD5E59A4E28C2)) >> 58];
}