from @stevengj's analysis (https://github.com/JuliaLang/julia/commit/e805fd6b505bf8a086b3d0b0b4dd798a1870c176#commitcomment-6089161)

and some of my own, I think we were significantly overestimating the conversion factor. i think we are roughly 1-to-1 for the symbols counted by occurs_more and the number of arguments to the llvm intrinsics

the estimate here is that 12 symbols in a line is relatively short. the limit on the number of lines is intended mostly as an optimization to skip counting when it is unlikely to be worth inlining