Modifying a constant in code might make sense because it saves several precious bytes of variable storage.
Your program is either front-end stalled by uop count or instruction cache latency, or back-end bound by memory bandwidth or ALU throughput or a serial dependency chain. It doesn't matter which is the bottleneck for this case, because inlining constants improves most of the above!
When the back end is the bottleneck, the front end stalls and vice versa, though I'm not sure how all processors report it.