[llvm] [CMake][LIT] Add option to run lit testsuites in parallel (PR #82899)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

Oh you're running very tiny lit target!

The problem of this is that most of the lit suite are massively parallel themselves.

The way to achieve good parallelism with lit isn't to call the targets the way you're doing here, instead you can do:

`ninja && bin/llvm-lit ../llvm/test/Analysis/{AliasSet,AssumptionCache,BasicAA,BlockFrequencyInfo,BranchProbabilityInfo,CallGraph,CostModel}`

Or:

```
LIT_OPTS=" --filter='Analysis/AliasSet|Analysis/AssumptionCache|Analysis/BasicAA|Analysis/BlockFrequencyInfo|Analysis/BranchProbabilityInfo|Analysis/CallGraph|Analysis/CostModel' " \
ninja check
```

I believe these are giving you "perfect" parallelism without over-subscription problem associated with the cmake option you introduced.




https://github.com/llvm/llvm-project/pull/82899