GHC.Core.SimpleOpt

Simple optimiser options

Default options for the Simple optimiser.

Returns Just (bndr, rhs) if the binding is a join point, or can be made into a join poin. Returns Nothing otherwise.

• If the input binder is a JoinId, just return it;

• if it's not yet a JoinId but is always tail-called, make it into a JoinId and return that.

In the latter case, eta-expand the RHS if necessary, to make the lambdas explicit, as is required for join points.

Precondition: the TailCallInfo of the InBndr is conservative:

• if it says AlwaysTailCalled, it is definitely always tail called,

• if it says NoTailCallInfo, then we're not sure.

See Note [JoinId vs TailCallInfo].

Returns Just ([b1..bp], dc, [t1..tk], [x1..xn]) if the argument expression is a *saturated* constructor application of the form let b1 in .. let bp in dc t1..tk x1 .. xn, where t1..tk are the *universally-quantified* type args of dc. Floats can also be (and most likely are) single-alternative case expressions. Why does exprIsConApp_maybe return floats? We may have to look through lets and cases to detect that we are in the presence of a data constructor wrapper. In this case, we need to return the lets and cases that we traversed. See Note [exprIsConApp_maybe on data constructors with wrappers]. Data constructor wrappers are unfolded late, but we really want to trigger case-of-known-constructor as early as possible. See also Note [Activation for data constructor wrappers] in GHC.Types.Id.Make.

We also return the incoming InScopeSet, augmented with the binders from any [FloatBind] that we return