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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/deSugar | |
| 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/deSugar')
| -rw-r--r-- | testsuite/tests/deSugar/should_compile/T2431.stderr | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/testsuite/tests/deSugar/should_compile/T2431.stderr b/testsuite/tests/deSugar/should_compile/T2431.stderr index 86d74c2d35..6e7df6c5de 100644 --- a/testsuite/tests/deSugar/should_compile/T2431.stderr +++ b/testsuite/tests/deSugar/should_compile/T2431.stderr @@ -1,9 +1,9 @@ ==================== Tidy Core ==================== Result size of Tidy Core - = {terms: 63, types: 43, coercions: 1, joins: 0/0} + = {terms: 63, types: 39, coercions: 1, joins: 0/0} --- RHS size: {terms: 2, types: 4, coercions: 1, joins: 0/0} +-- RHS size: {terms: 2, types: 3, coercions: 1, joins: 0/0} T2431.$WRefl [InlPrag=INLINE[final] CONLIKE] :: forall a. a :~: a [GblId[DataConWrapper], Caf=NoCafRefs, @@ -15,7 +15,7 @@ T2431.$WRefl [InlPrag=INLINE[final] CONLIKE] :: forall a. a :~: a T2431.$WRefl = \ (@a) -> T2431.Refl @a @a @~(<a>_N :: a GHC.Prim.~# a) --- RHS size: {terms: 4, types: 8, coercions: 0, joins: 0/0} +-- RHS size: {terms: 4, types: 7, coercions: 0, joins: 0/0} absurd :: forall a. (Int :~: Bool) -> a [GblId, Arity=1, Str=<U>b, Cpr=b, Unf=OtherCon []] absurd = \ (@a) (x :: Int :~: Bool) -> case x of { } |