Unlifted primop types

David Feuer david.feuer at gmail.com
Tue Aug 21 15:56:07 UTC 2018

But how do I have to build something like "openAlphaTyVar" for TYPE
'UnliftedRep in the primitive space? I don't understand the toolkit.

On Tue, Aug 21, 2018, 11:07 AM Ben Gamari <ben at smart-cactus.org> wrote:

> David Feuer <david at well-typed.com> writes:
> > On Monday, August 20, 2018 12:11:14 PM EDT Simon Peyton Jones via
> ghc-devs wrote:
> >> I don’t quite know how primops.txt.pp is processed, but perhaps by
> utils/genprimopcode.   You may need to update the syntax a bit?
> >
> > The whole thing is a mystery to me. Whatever it's doing seems to
> > generate code that puts things in TysPrim.hs together, and that module
> > also looks rather murky to the uninitiated.
> primops.txt.pp is processed by genprimopcode, as suggested by Simon.
> genprimopcode has several modes, each of which produces a different
> output. These are listed in compiler/ghc.mk; grep for
> preprocessCompilerFiles. They broadly fall into three categories:
>  * A set of headers which define the `PrimOp` type and functions defining
>    primops' various properties (e.g. out-of-line-ness)
>  * The GHC.PrimopWrappers module of `ghc-prim`, which defines functions
>    wrapping each of the primops; these are used by GHCi (see Note
>    [Primop Wrappers]
>  * The `GHC.Prim`module of `ghc-prim`, which has no code but rather
>    merely serves as a documented source file to be used by Haddock.
> genprimopcode's notion of non-Type kinded tyvars is very limited. It
> provides a few tyvars of kind Type (namely a, b, and c) and an
> "open-kinded" tyvar of any runtime rep (namely o). I believe you would
> need to add an additional binder to the genopcode parser to get what you
> want. I suspect this would only require a few lines, however.
> Cheers,
> - Ben
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