Emulating variable bit-shift using only constant shifts?

Question

I\'m trying to find a way to perform an indirect shift-left/right operation without actually using the variable shift op or any branches.

The particular PowerPC pro

Answer 1

Here's something that is trivially unrollable:

int result= value;

int shift_accumulator= value;

for (int i= 0; i<5; ++i)
{
    result += shift_accumulator & (-(k & 1)); // replace with isel if appropriate
    shift_accumulator += shift_accumulator;
    k >>= 1;
}