- -- Attach the rules for each locally-defined Id to that Id.
- -- - This makes the rules easier to look up
- -- - It means that transformation rules and specialisations for
- -- locally defined Ids are handled uniformly
- -- - It keeps alive things that are referred to only from a rule
- -- (the occurrence analyser knows about rules attached to Ids)
- -- - It makes sure that, when we apply a rule, the free vars
- -- of the RHS are more likely to be in scope
- --
- -- Both the LHS and RHS Ids are marked 'no-discard'.
- -- This means that the binding won't be discarded EVEN if the binding
- -- ends up being trivial (v = w) -- the simplifier would usually just
- -- substitute w for v throughout, but we don't apply the substitution to
- -- the rules (maybe we should?), so this substitution would make the rule
- -- bogus.
-
-addRulesToBinds binds local_rules
- = (map zap_bind binds, rule_lhs_fvs)
+-- Update the binders of top-level bindings as follows
+-- a) Attach the rules for each locally-defined Id to that Id.
+-- b) Set the no-discard flag if either the Id is exported,
+-- or it's mentoined in the RHS of a rule
+--
+-- Reason for (a)
+-- - It makes the rules easier to look up
+-- - It means that transformation rules and specialisations for
+-- locally defined Ids are handled uniformly
+-- - It keeps alive things that are referred to only from a rule
+-- (the occurrence analyser knows about rules attached to Ids)
+-- - It makes sure that, when we apply a rule, the free vars
+-- of the RHS are more likely to be in scope
+--
+-- Reason for (b)
+-- It means that the binding won't be discarded EVEN if the binding
+-- ends up being trivial (v = w) -- the simplifier would usually just
+-- substitute w for v throughout, but we don't apply the substitution to
+-- the rules (maybe we should?), so this substitution would make the rule
+-- bogus.
+
+updateBinders rule_ids rule_rhs_fvs is_exported binds
+ = map update_bndrs binds