How good your knowledge of bitwise tricks? Exercise.

I searched for rotate left/right function in pure C and found this:

// https://blog.regehr.org/archives/1063
uint32_t rotl32 (uint32_t x, uint32_t n)
{
        assert (n<32);
        return (x<<n) | (x>>(-n&31));
}

Ouch! John Regehr provided only rotate left function without corresponding right one. But I can manage this! I can reimplement rotr() using rotl(). My function is:

uint32_t rotr32_my(uint32_t x, uint32_t n)
{
        return ??? rotl32(?, ?) ???;
};

In my case, the length of "return ??? rotl32(?, ?) ???;" is 23 characters. If you can reimplement rotate right using only rotate left, your solution shouldn't be any longer.

In the same way, ROR x86 assembly instruction can be implemented using ROL. How?

UPD: the answer.

(the post first published at 20220914.)

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