When enabling the option `-sil-opt-profile-repeat=<n>`, the optimizer runs passes n times and reports the total runtime at the end of the pass pipeline.
This is useful to profile a specific optimization pass with `sil-opt`.
For example, to profile the stack promotion pass:
```
sil-opt -stack-promotion -sil-opt-profile-repeat=10000 -o /dev/null test.sil
```
