Compile module in attached zip
javac -d out --module-source-path . `find . -name "*.java"`

Then run Jlink
jlink --module-path out:jdk/jmods --output jlink-out --add-modules m1 --suggest-providers p1.B

you will see
Suggested providers:
  module m1 provides p1.B, used by m1
  module m1 provides p1.S, used by m1

The second line contains info about p1.S.