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| author | Simon Peyton Jones <simon.peytonjones@gmail.com> | 2023-03-31 11:28:54 +0100 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2023-05-12 23:50:25 -0400 |
| commit | 8b9b7dbc913b66795c283683c7fe1fb48672666d (patch) | |
| tree | 920a6f25019a433283e3fcb17c7edd984d283443 /compiler/GHC/Tc/Solver/Rewrite.hs | |
| parent | dc0c957439c2fae14547de24ff665fc4f5db56a7 (diff) | |
| download | haskell-8b9b7dbc913b66795c283683c7fe1fb48672666d.tar.gz | |
Use the eager unifier in the constraint solver
This patch continues the refactoring of the constraint solver
described in #23070.
The Big Deal in this patch is to call the regular, eager unifier from the
constraint solver, when we want to create new equalities. This
replaces the existing, unifyWanted which amounted to
yet-another-unifier, so it reduces duplication of a rather subtle
piece of technology. See
* Note [The eager unifier] in GHC.Tc.Utils.Unify
* GHC.Tc.Solver.Monad.wrapUnifierTcS
I did lots of other refactoring along the way
* I simplified the treatment of right hand sides that contain CoercionHoles.
Now, a constraint that contains a hetero-kind CoercionHole is non-canonical,
and cannot be used for rewriting or unification alike. This required me
to add the ch_hertero_kind flag to CoercionHole, with consequent knock-on
effects. See wrinkle (2) of `Note [Equalities with incompatible kinds]` in
GHC.Tc.Solver.Equality.
* I refactored the StopOrContinue type to add StartAgain, so that after a
fundep improvement (for example) we can simply start the pipeline again.
* I got rid of the unpleasant (and inefficient) rewriterSetFromType/Co functions.
With Richard I concluded that they are never needed.
* I discovered Wrinkle (W1) in Note [Wanteds rewrite Wanteds] in
GHC.Tc.Types.Constraint, and therefore now prioritise non-rewritten equalities.
Quite a few error messages change, I think always for the better.
Compiler runtime stays about the same, with one outlier: a 17% improvement in T17836
Metric Decrease:
T17836
T18223
Diffstat (limited to 'compiler/GHC/Tc/Solver/Rewrite.hs')
| -rw-r--r-- | compiler/GHC/Tc/Solver/Rewrite.hs | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/compiler/GHC/Tc/Solver/Rewrite.hs b/compiler/GHC/Tc/Solver/Rewrite.hs index 6508a21420..64d590cbe9 100644 --- a/compiler/GHC/Tc/Solver/Rewrite.hs +++ b/compiler/GHC/Tc/Solver/Rewrite.hs @@ -41,6 +41,7 @@ import Control.Applicative (liftA3) import GHC.Builtin.Types (tYPETyCon) import Data.List ( find ) import GHC.Data.List.Infinite (Infinite) +import GHC.Data.Bag( listToBag ) import qualified GHC.Data.List.Infinite as Inf {- @@ -155,7 +156,7 @@ bumpDepth (RewriteM thing_inside) -- Precondition: the CtEvidence is a CtWanted of an equality recordRewriter :: CtEvidence -> RewriteM () recordRewriter (CtWanted { ctev_dest = HoleDest hole }) - = RewriteM $ \env -> updTcRef (re_rewriters env) (`addRewriterSet` hole) + = RewriteM $ \env -> updTcRef (re_rewriters env) (`addRewriter` hole) recordRewriter other = pprPanic "recordRewriter" (ppr other) {- @@ -945,7 +946,7 @@ runTcPluginRewriters rewriteEnv rewriterFunctions tys TcPluginRewriteTo { tcPluginReduction = redn , tcRewriterNewWanteds = wanteds - } -> do { emitWork wanteds; return $ Just redn } + } -> do { emitWork (listToBag wanteds); return $ Just redn } TcPluginNoRewrite {} -> runRewriters givens rewriters {- |