Issue 125720043: code review 125720043: cmd/gc: make liveness ~10x faster - Code Reviewcmd/gc: make liveness ~10x faster 1) The arrayindexof lookup function is O(n). Replace with O(1) lookups. 2) The checkptxt function is O(n²) and is purely for debugging. Only run when the debugging flags are turned on. 3) Iterating over sparse bitmaps can be done faster word by word. Introduce and use bvnext for that. Run times before and after, on my 2.5 GHz Core i5 MacBook Pro. x.go 9.48 0.84 is
