Gets rid of the stuff that prevents us from understanding the runtime representation of a type. Including: 1. Casts 2. Newtypes 3. Foralls 4. Synonyms But not type/data families, because we don't have the envs to hand.

True if the type has zero width.

Discovers the primitive representation of a Type. Returns a list of PrimRep: it's a list because of the possibility of no runtime representation (void) or multiple (unboxed tuple/sum) See also Note [Getting from RuntimeRep to PrimRep]

Like typePrimRep, but assumes that there is precisely one PrimRep output; an empty list of PrimReps becomes a VoidRep. This assumption holds after unarise, see Note [Post-unarisation invariants]. Before unarise it may or may not hold. See also Note [RuntimeRep and PrimRep] and Note [VoidRep]

Like typePrimRep, but returns Nothing instead of panicking, when

• The ty was not of form TYPE rep
• rep was not monomorphic

Take a type of kind RuntimeRep and extract the list of PrimRep that it encodes. See also Note [Getting from RuntimeRep to PrimRep] The [PrimRep] is the final runtime representation after unarisation

A PrimRep is an abstraction of a type. It contains information that the code generator needs in order to pass arguments, return results, and store values of this type. See also Note [RuntimeRep and PrimRep] in GHC.Types.RepType and Note [VoidRep] in GHC.Types.RepType.

Convert a PrimRep back to a Type. Used only in the unariser to give types to fresh Ids. Really, only the type's representation matters. See also Note [RuntimeRep and PrimRep]

Find the runtime representation of a TyCon. Defined here to avoid module loops. Returns a list of the register shapes necessary. See also Note [Getting from RuntimeRep to PrimRep]

Like tyConPrimRep, but assumed that there is precisely zero or one PrimRep output See also Note [Getting from RuntimeRep to PrimRep] and Note [VoidRep]

Given the arguments of a sum type constructor application, return the unboxed sum rep type.

E.g.

(# Int# | Maybe Int | (# Int#, Float# #) #)

We call `ubxSumRepType [ [IntRep], [LiftedRep], [IntRep, FloatRep] ]`, which returns [WordSlot, PtrSlot, WordSlot, FloatSlot]

INVARIANT: Result slots are sorted (via Ord SlotTy), except that at the head of the list we have the slot for the tag.