Note [Compilation plan for top-level string literals]

Here is a summary on how top-level string literals are handled by various
parts of the compilation pipeline.

* In the source language, there is no way to bind a primitive string literal
  at the top level.

* In Core, we have a special rule that permits top-level Addr# bindings. See
  Note [Core top-level string literals]. Core-to-core passes may introduce
  new top-level string literals.

  See GHC.Core.Utils.exprIsTopLevelBindable, and exprIsTickedString

* In STG, top-level string literals are explicitly represented in the syntax
  tree.

* A top-level string literal may end up exported from a module. In this case,
  in the object file, the content of the exported literal is given a label with
  the _bytes suffix.