[llvm] [doc][mlgo] Document the logger (serialization) and expose the doc (PR #141094)

[Mircea Trofin via llvm-commits]

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@@ -338,12 +338,94 @@ requiring no out of tree build-time dependencies.
   presumably a python training algorithm. We do not envision using this in a
   production environment.
 
+- ``NoInferenceModelRunner``. This serves as a store for feature values, and its
+  ``evaluate`` should never be called. It's used for training scenarios, when we
+  want to capture the behavior of the default (non-ML) heuristic.
+
 Note that training leaves it to the training infrastructure to handle
 distributed computing. The assumed architecture has python processes
 communicating remotely between themselves, but managing local communication with
 clang.
 
-..
-    TODO(mtrofin): 
-        - logging, and the use in interactive mode.
-        - discuss an example (like the inliner)
+Logging Facility
+----------------
+
+When training models, we need to expose the features we will want to use during
+inference, as well as outcomes, to guide reward-based learning techniques. This
+can happen in 2 forms:
+
+- as an effect of running the compiler on some input, as a capture of the
----------------
mtrofin wrote:

ptal

https://github.com/llvm/llvm-project/pull/141094