[llvm] [GlobalISel] Reserve IRTranslator value map and virtual register storage (NFC) (PR #222311)

[Alexis Engelke via llvm-commits]

aengelke wrote:

> is the cycles metric in the compile-time-tracker reliable? It doesn't show any significant change

It's too noisy. You have to do measurements on hardware with sufficient repetitions (e.g. perf stat -r or hyperfine -r).

https://github.com/llvm/llvm-project/pull/222311