[llvm] [Inliner] Add cost model loop penalty for -Os. (PR #227042)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

I wonder about a "allowed-cost=9999" function attribute that the inliner sets on functions the first time it sees a function, and inlining (and even loop unrolling) eats up that budget until it goes to 0

it'd be nice to know in this specific case how big the function gets and to get a flame graph (or just time report) of where LLVM is spending time

https://github.com/llvm/llvm-project/pull/227042