immed_8r encoding

ARM32 instruction MOV, #imm will use the immed_8r encoding, basically immed_8r we cared is:

xxxxxxxx xxxxxxxx xxxxrrrr bbbbbbbb

Here rrrr is number of bits need do right shift, bbbbbbbb is 8bit immediate. The final immediate using immed_8r encoding is:

static unsigned ror(unsigned x, unsigned b)
{
        unsigned ret;

        ret = (x >> b) | (( x & ( (1 << b) -1 ) ) << (32 - b) );

        return ret;
}

static unsigned immed_8r(unsigned imm, unsigned sh)
{
        unsigned i;

        for (i = 0; i < sh; i++) {
                imm = ror(imm, 2);               /* we can do 2*15 == 30 ROR totally */
        }

        return imm;
}