diff options
| -rw-r--r-- | compiler/basicTypes/MkId.lhs | 41 | ||||
| -rw-r--r-- | compiler/coreSyn/CorePrep.lhs | 12 | ||||
| -rw-r--r-- | compiler/stranal/WorkWrap.lhs | 13 |
3 files changed, 36 insertions, 30 deletions
diff --git a/compiler/basicTypes/MkId.lhs b/compiler/basicTypes/MkId.lhs index b28b985e7f..a85b69c682 100644 --- a/compiler/basicTypes/MkId.lhs +++ b/compiler/basicTypes/MkId.lhs @@ -33,7 +33,7 @@ module MkId ( -- And some particular Ids; see below for why they are wired in wiredInIds, ghcPrimIds, unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId, - lazyId, lazyIdUnfolding, lazyIdKey, + lazyId, lazyIdKey, mkRuntimeErrorApp, mkImpossibleExpr, rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID, @@ -920,29 +920,34 @@ seqId = pcMiscPrelId seqName ty info rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)]) ------------------------------------------------ -lazyId :: Id --- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too) --- Used to lazify pseq: pseq a b = a `seq` lazy b --- --- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here, --- not from GHC.Base.hi. This is important, because the strictness --- analyser will spot it as strict! --- --- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapperpass --- (see WorkWrap.wwExpr) --- We could use inline phases to do this, but that would be vulnerable to changes in --- phase numbering....we must inline precisely after strictness analysis. +lazyId :: Id -- See Note [lazyId magic] lazyId = pcMiscPrelId lazyIdName ty info where info = noCafIdInfo ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy) - -lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal -lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x) - where - [x] = mkTemplateLocals [openAlphaTy] \end{code} +Note [lazyId magic] +~~~~~~~~~~~~~~~~~~~ + lazy :: forall a?. a? -> a? (i.e. works for unboxed types too) + +Used to lazify pseq: pseq a b = a `seq` lazy b + +Also, no strictness: by being a built-in Id, all the info about lazyId comes from here, +not from GHC.Base.hi. This is important, because the strictness +analyser will spot it as strict! + +Also no unfolding in lazyId: it gets "inlined" by a HACK in CorePrep. +It's very important to do this inlining *after* unfoldings are exposed +in the interface file. Otherwise, the unfolding for (say) pseq in the +interface file will not mention 'lazy', so if we inline 'pseq' we'll totally +miss the very thing that 'lazy' was there for in the first place. +See Trac #3259 for a real world example. + +lazyId is defined in GHC.Base, so we don't *have* to inline it. If it +appears un-applied, we'll end up just calling it. + +------------------------------------------------------------- @realWorld#@ used to be a magic literal, \tr{void#}. If things get nasty as-is, change it back to a literal (@Literal@). diff --git a/compiler/coreSyn/CorePrep.lhs b/compiler/coreSyn/CorePrep.lhs index 3a6d037979..89ec98f6f2 100644 --- a/compiler/coreSyn/CorePrep.lhs +++ b/compiler/coreSyn/CorePrep.lhs @@ -11,6 +11,7 @@ module CorePrep ( #include "HsVersions.h" +import PrelNames ( lazyIdKey, hasKey ) import CoreUtils import CoreArity import CoreFVs @@ -89,6 +90,8 @@ The goal of this pass is to prepare for code generation. We want curried definitions for all of these in case they aren't inlined by some caller. +9. Replace (lazy e) by e. See Note [lazyId magic] in MkId.lhs + This is all done modulo type applications and abstractions, so that when type erasure is done for conversion to STG, we don't end up with any trivial or useless bindings. @@ -341,9 +344,14 @@ cpeRhsE :: CorePrepEnv -> CoreExpr -> UniqSM (Floats, CpeRhs) cpeRhsE _env expr@(Type _) = return (emptyFloats, expr) cpeRhsE _env expr@(Lit _) = return (emptyFloats, expr) -cpeRhsE env expr@(App {}) = cpeApp env expr cpeRhsE env expr@(Var {}) = cpeApp env expr +cpeRhsE env (Var f `App` _ `App` arg) + | f `hasKey` lazyIdKey -- Replace (lazy a) by a + = cpeRhsE env arg -- See Note [lazyId magic] in MkId + +cpeRhsE env expr@(App {}) = cpeApp env expr + cpeRhsE env (Let bind expr) = do { (env', new_binds) <- cpeBind NotTopLevel env bind ; (floats, body) <- cpeRhsE env' expr @@ -475,7 +483,7 @@ cpeApp env expr collect_args (App fun arg) depth = do { (fun',hd,fun_ty,floats,ss) <- collect_args fun (depth+1) - ; let + ; let (ss1, ss_rest) = case ss of (ss1:ss_rest) -> (ss1, ss_rest) [] -> (lazyDmd, []) diff --git a/compiler/stranal/WorkWrap.lhs b/compiler/stranal/WorkWrap.lhs index 772a8623f3..a3219abb20 100644 --- a/compiler/stranal/WorkWrap.lhs +++ b/compiler/stranal/WorkWrap.lhs @@ -15,14 +15,12 @@ import Id ( Id, idType, isOneShotLambda, idUnfolding, setIdNewStrictness, mkWorkerId, setIdWorkerInfo, setInlineActivation, setIdArity, idInfo ) -import MkId ( lazyIdKey, lazyIdUnfolding ) import Type ( Type ) import IdInfo import NewDemand ( Demand(..), StrictSig(..), DmdType(..), DmdResult(..), Demands(..), mkTopDmdType, isBotRes, returnsCPR, topSig, isAbsent ) import UniqSupply -import Unique ( hasKey ) import BasicTypes ( RecFlag(..), isNonRec, isNeverActive, Activation, inlinePragmaActivation ) import VarEnv ( isEmptyVarEnv ) @@ -107,17 +105,12 @@ matching by looking for strict arguments of the correct type. \begin{code} wwExpr :: CoreExpr -> UniqSM CoreExpr -wwExpr e@(Type _) = return e -wwExpr e@(Lit _) = return e +wwExpr e@(Type {}) = return e +wwExpr e@(Lit {}) = return e +wwExpr e@(Var {}) = return e wwExpr e@(Note InlineMe _) = return e -- Don't w/w inside InlineMe's -wwExpr e@(Var v) - | v `hasKey` lazyIdKey = return lazyIdUnfolding - | otherwise = return e - -- HACK alert: Inline 'lazy' after strictness analysis - -- (but not inside InlineMe's) - wwExpr (Lam binder expr) = Lam binder <$> wwExpr expr |