Implement auto-specialisation of imported Ids
This big-ish patch arranges that if an Id 'f' is
* Type-class overloaded
f :: Ord a => [a] -> [a]
* Defined with an INLINABLE pragma
{-# INLINABLE f #-}
* Exported from its defining module 'D'
then in any module 'U' that imports D
1. Any call of 'f' at a fixed type will generate
(a) a specialised version of f in U
(b) a RULE that rewrites unspecialised calls to the
specialised on
e.g. if the call is (f Int dOrdInt xs) then the
specialiser will generate
$sfInt :: [Int] -> [Int]
$sfInt = <code for f, imported from D, specialised>
{-# RULE forall d. f Int d = $sfInt #-}
2. In addition, you can give an explicit {-# SPECIALISE -#}
pragma for the imported Id
{-# SPECIALISE f :: [Bool] -> [Bool] #-}
This too generates a local specialised definition,
and the corresponding RULE
The new RULES are exported from module 'U', so that any module
importing U will see the specialised versions of 'f', and will
not re-specialise them.
There's a flag -fwarn-auto-orphan that warns you if the auto-generated
RULES are orphan rules. It's not in -Wall, mainly to avoid lots of
error messages with existing packages.
Main implementation changes
- A new flag on a CoreRule to say if it was auto-generated.
This is persisted across interface files, so there's a small
change in interface file format.
- Quite a bit of fiddling with plumbing, to get the
{-# SPECIALISE #-} pragmas for imported Ids. In particular, a
new field tgc_imp_specs in TcGblEnv, to keep the specialise
pragmas for imported Ids between the typechecker and the desugarer.
- Some new code (although surprisingly little) in Specialise,
to deal with calls of imported Ids
27 files changed: