Ticket #7663 (closed feature request: duplicate)
consider free variables as well as parameters in inline discounts
The inliner assigns discount values for scrutinized parameters but not for scrutinized free variables.
Experimenting with an aggressive lambda float at the end of the core2core pipeline identified a situation where (effectively) assigning discounts to free variables gives a performance boost. (The free variables become parameters during the float and hence are then assigned discounts.)
For spectral/boyer2, doing the late lambda float and then simplifying results in a -7% improvement in allocation. Without the simplifications, the late lambda float alone does not change allocation: thus the lion's share of the -7% could be attained simply by assigning discounts to scrutinized free variables.
For reference: the function in boyer2 that gets inlined is a join point that arises near the top of the worker for "Rewritefns.onewayunify".