import CmdLineOpts ( DynFlag(..), dopt )
import HsSyn ( HsDecl(..), InstDecl(..), TyClDecl(..), HsType(..),
- MonoBinds(..), HsExpr(..), HsLit(..), Sig(..),
+ MonoBinds(..), HsExpr(..), HsLit(..), Sig(..), HsTyVarBndr(..),
andMonoBindList, collectMonoBinders, isClassDecl, toHsType
)
import RnHsSyn ( RenamedHsBinds, RenamedInstDecl, RenamedHsDecl,
tcExtendTyVarEnvForMeths,
tcAddImportedIdInfo, tcLookupClass,
InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
- simpleInstInfoTy, newDFunName, tcExtendTyVarEnv,
+ simpleInstInfoTy, newDFunName,
isLocalThing,
)
import InstEnv ( InstEnv, extendInstEnv )
-import TcMonoType ( tcTyVars, tcHsSigType, kcHsSigType, checkSigTyVars )
+import TcMonoType ( tcHsTyVars, tcHsSigType, kcHsSigType, checkSigTyVars )
import TcSimplify ( tcSimplifyCheck )
import HscTypes ( HomeSymbolTable, DFunId,
ModDetails(..), PackageInstEnv, PersistentRenamerState
import Generics ( validGenericInstanceType )
import Module ( Module, foldModuleEnv )
import Name ( getSrcLoc )
-import NameSet ( emptyNameSet, unitNameSet, nameSetToList )
+import NameSet ( unitNameSet, nameSetToList )
import PrelInfo ( eRROR_ID )
import PprType ( pprClassPred, pprPred )
import TyCon ( TyCon, isSynTyCon )
import Subst ( mkTopTyVarSubst, substTheta )
import VarSet ( varSetElems )
import TysWiredIn ( genericTyCons, isFFIArgumentTy, isFFIImportResultTy )
+import ForeignCall ( Safety(..) )
import PrelNames ( cCallableClassKey, cReturnableClassKey, hasKey )
import Name ( Name )
import SrcLoc ( SrcLoc )
-- For example: instance (C a, C b) => C (a+b) where { binds }
= -- Extract the universally quantified type variables
- tcTyVars (nameSetToList (extractHsTyVars hs_ty))
- (kcHsSigType hs_ty) `thenTc` \ tyvars ->
- tcExtendTyVarEnv tyvars $
+ let
+ sig_tvs = map UserTyVar (nameSetToList (extractHsTyVars hs_ty))
+ in
+ tcHsTyVars sig_tvs (kcHsSigType hs_ty) $ \ tyvars ->
-- Type-check the instance type, and check its form
tcHsSigType hs_ty `thenTc` \ inst_ty ->
-- Always inline the dfun; this is an experimental decision
-- because it makes a big performance difference sometimes.
-- Often it means we can do the method selection, and then
- -- inline the method as well. Marcin's idea.
+ -- inline the method as well. Marcin's idea; see comments below.
dict_rhs
| null scs_and_meths
main_bind `AndMonoBinds` prag_binds)
\end{code}
+ ------------------------------
+ Inlining dfuns unconditionally
+ ------------------------------
+
+The code above unconditionally inlines dict funs. Here's why.
+Consider this program:
+
+ test :: Int -> Int -> Bool
+ test x y = (x,y) == (y,x) || test y x
+ -- Recursive to avoid making it inline.
+
+This needs the (Eq (Int,Int)) instance. If we inline that dfun
+the code we end up with is good:
+
+ Test.$wtest =
+ \r -> case ==# [ww ww1] of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True ->
+ case ==# [ww1 ww] of wild1 {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+ };
+ Test.test = \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+If we don't inline the dfun, the code is not nearly as good:
+
+ (==) = case PrelTup.$fEq(,) PrelBase.$fEqInt PrelBase.$fEqInt of tpl {
+ PrelBase.:DEq tpl1 tpl2 -> tpl2;
+ };
+
+ Test.$wtest =
+ \r [ww ww1]
+ let { y = PrelBase.I#! [ww1]; } in
+ let { x = PrelBase.I#! [ww]; } in
+ let { sat_slx = PrelTup.(,)! [y x]; } in
+ let { sat_sly = PrelTup.(,)! [x y];
+ } in
+ case == sat_sly sat_slx of wild {
+ PrelBase.False -> Test.$wtest ww1 ww;
+ PrelBase.True -> PrelBase.True [];
+ };
+
+ Test.test =
+ \r [w w1]
+ case w of w2 {
+ PrelBase.I# ww ->
+ case w1 of w3 { PrelBase.I# ww1 -> Test.$wtest ww ww1; };
+ };
+
+Why doesn't GHC inline $fEq? Because it looks big:
+
+ PrelTup.zdfEqZ1T{-rcX-}
+ = \ @ a{-reT-} :: * @ b{-reS-} :: *
+ zddEq{-rf6-} _Ks :: {PrelBase.Eq{-23-} a{-reT-}}
+ zddEq1{-rf7-} _Ks :: {PrelBase.Eq{-23-} b{-reS-}} ->
+ let {
+ zeze{-rf0-} _Kl :: (b{-reS-} -> b{-reS-} -> PrelBase.Bool{-3c-})
+ zeze{-rf0-} = PrelBase.zeze{-01L-}@ b{-reS-} zddEq1{-rf7-} } in
+ let {
+ zeze1{-rf3-} _Kl :: (a{-reT-} -> a{-reT-} -> PrelBase.Bool{-3c-})
+ zeze1{-rf3-} = PrelBase.zeze{-01L-} @ a{-reT-} zddEq{-rf6-} } in
+ let {
+ zeze2{-reN-} :: ((a{-reT-}, b{-reS-}) -> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ zeze2{-reN-} = \ ds{-rf5-} _Ks :: (a{-reT-}, b{-reS-})
+ ds1{-rf4-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ case ds{-rf5-}
+ of wild{-reW-} _Kd { (a1{-rf2-} _Ks, a2{-reZ-} _Ks) ->
+ case ds1{-rf4-}
+ of wild1{-reX-} _Kd { (b1{-rf1-} _Ks, b2{-reY-} _Ks) ->
+ PrelBase.zaza{-r4e-}
+ (zeze1{-rf3-} a1{-rf2-} b1{-rf1-})
+ (zeze{-rf0-} a2{-reZ-} b2{-reY-})
+ }
+ } } in
+ let {
+ a1{-reR-} :: ((a{-reT-}, b{-reS-})-> (a{-reT-}, b{-reS-})-> PrelBase.Bool{-3c-})
+ a1{-reR-} = \ a2{-reV-} _Ks :: (a{-reT-}, b{-reS-})
+ b1{-reU-} _Ks :: (a{-reT-}, b{-reS-}) ->
+ PrelBase.not{-r6I-} (zeze2{-reN-} a2{-reV-} b1{-reU-})
+ } in
+ PrelBase.zdwZCDEq{-r8J-} @ (a{-reT-}, b{-reS-}) a1{-reR-} zeze2{-reN-})
+
+and it's not as bad as it seems, because it's further dramatically
+simplified: only zeze2 is extracted and its body is simplified.
+
%************************************************************************
%* *
maybe_tycon_app = splitTyConApp_maybe first_inst_tau
Just (tycon, arg_tys) = maybe_tycon_app
- ccallable_type dflags ty = isFFIArgumentTy dflags False {- Not safe call -} ty
+ ccallable_type dflags ty = isFFIArgumentTy dflags PlayRisky ty
creturnable_type ty = isFFIImportResultTy dflags ty
check_tyvars dflags clas inst_taus
projects / ghc-hetmet.git / blobdiff