perf(library/vm/vm): small optimizations
perf(library/vm/vm): small optimizations

soonhokong/lean-osx,soonhokong/lean-osx,soonhokong/lean-osx,Kha/lean,leanprover/lean,avigad/lean,fgdorais/lean,soonhokong/lean-osx,dselsam/lean,johoelzl/lean,leanprover/lean,rlewis1988/lean,soonhokong/lean-windows,fgdorais/lean,dselsam/lean,leanprover-community/lean,avigad/lean,digama0/lean,digama0/lean,fgdorais/lean,digama0/lean,soonhokong/lean-windows,soonhokong/lean-windows,johoelzl/lean,soonhokong/lean-windows,leodemoura/lean,leodemoura/lean,fpvandoorn/lean,leanprover-community/lean,digama0/lean,rlewis1988/lean,digama0/lean,dselsam/lean,dselsam/lean,leanprover/lean,rlewis1988/lean,soonhokong/lean-windows,Kha/lean,fpvandoorn/lean,Kha/lean,rlewis1988/lean,avigad/lean,avigad/lean,leodemoura/lean,johoelzl/lean,leanprover/lean,johoelzl/lean,fgdorais/lean,leanprover/lean,rlewis1988/lean,fgdorais/lean,johoelzl/lean,Kha/lean,rlewis1988/lean,fgdorais/lean,fpvandoorn/lean,leanprover-community/lean,fpvandoorn/lean,avigad/lean,leanprover/lean,soonhokong/lean-osx,digama0/lean,leanprover-community/lean,leodemoura/lean,fpvandoorn/lean,Kha/lean,leanprover-community/lean,fpvandoorn/lean,leanprover-community/lean,avigad/lean,johoelzl/lean,dselsam/lean,leodemoura/lean,dselsam/lean,leodemoura/lean,Kha/lean