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| author | Ben Gamari <ben@smart-cactus.org> | 2020-03-24 13:13:43 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2020-12-14 13:37:09 -0500 |
| commit | 7e9debd4ceb068effe8ac81892d2cabcb8f55850 (patch) | |
| tree | f222f3f3e5d662a12ab00fcb1a81d8e8dfb6c0de /testsuite/tests/deriving | |
| parent | c696bb2f4476e0ce4071e0d91687c1fe84405599 (diff) | |
| download | haskell-7e9debd4ceb068effe8ac81892d2cabcb8f55850.tar.gz | |
Optimise nullary type constructor usage
During the compilation of programs GHC very frequently deals with
the `Type` type, which is a synonym of `TYPE 'LiftedRep`. This patch
teaches GHC to avoid expanding the `Type` synonym (and other nullary
type synonyms) during type comparisons, saving a good amount of work.
This optimisation is described in `Note [Comparing nullary type
synonyms]`.
To maximize the impact of this optimisation, we introduce a few
special-cases to reduce `TYPE 'LiftedRep` to `Type`. See
`Note [Prefer Type over TYPE 'LiftedPtrRep]`.
Closes #17958.
Metric Decrease:
T18698b
T1969
T12227
T12545
T12707
T14683
T3064
T5631
T5642
T9020
T9630
T9872a
T13035
haddock.Cabal
haddock.base
Diffstat (limited to 'testsuite/tests/deriving')
| -rw-r--r-- | testsuite/tests/deriving/should_compile/T14578.stderr | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/testsuite/tests/deriving/should_compile/T14578.stderr b/testsuite/tests/deriving/should_compile/T14578.stderr index 0018ebe569..d93f12c34c 100644 --- a/testsuite/tests/deriving/should_compile/T14578.stderr +++ b/testsuite/tests/deriving/should_compile/T14578.stderr @@ -16,13 +16,12 @@ Derived class instances: = GHC.Prim.coerce @(T14578.App (Data.Functor.Compose.Compose f g) a -> T14578.App (Data.Functor.Compose.Compose f g) a - -> T14578.App (Data.Functor.Compose.Compose f g) a) + -> T14578.App (Data.Functor.Compose.Compose f g) a) @(T14578.Wat f g a -> T14578.Wat f g a -> T14578.Wat f g a) ((GHC.Base.<>) @(T14578.App (Data.Functor.Compose.Compose f g) a)) GHC.Base.sconcat = GHC.Prim.coerce - @(GHC.Base.NonEmpty - (T14578.App (Data.Functor.Compose.Compose f g) a) + @(GHC.Base.NonEmpty (T14578.App (Data.Functor.Compose.Compose f g) a) -> T14578.App (Data.Functor.Compose.Compose f g) a) @(GHC.Base.NonEmpty (T14578.Wat f g a) -> T14578.Wat f g a) (GHC.Base.sconcat @@ -31,7 +30,7 @@ Derived class instances: = GHC.Prim.coerce @(b -> T14578.App (Data.Functor.Compose.Compose f g) a - -> T14578.App (Data.Functor.Compose.Compose f g) a) + -> T14578.App (Data.Functor.Compose.Compose f g) a) @(b -> T14578.Wat f g a -> T14578.Wat f g a) (GHC.Base.stimes @(T14578.App (Data.Functor.Compose.Compose f g) a)) |