It's a noop in most cases because the cost of spilling a given loop variable is still the same relative to other loop variables. But yes, the only affect it

It's a noop in most cases because the cost of spilling a given loop variable is still the same relative to other loop variables. But yes, the only affect it should have is to possibly value loop variables low enough to spill them instead of non loop variables (note that non loop variables are calculated using both exit and entry frequencies) That is almost certainly a bad idea in general, execution frequencies are what you should use whether in loops or not. It most likely the real issue is a bunch of loops are having their relative (to non loop blocks) execution frequencies over estimated highly, and in reality the loop doesn't execute much