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If we are lowering a frem and the divisor is known to be an integer power-2, we can use the formula 'frem = x - trunc(x / d) * d'. This avoids the more expensive call to fmod. The results are identical as fmod so long as d is a power-2 (so the mul does not round incorrectly), and the sign of the return is either always positive or not important for zeroes (nsz). Unfortunately Alive2 does not handle this well at the moment. I was using exhaustive checking to test this: (https://gist.github.com/davemgreen/6078015f30d3bacd1e9572f8db5d4b64). I found this in cpythons implementation of float_pow. I currently added it as a DAG combine for frem with power-2 fp constants.