X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplify.lhs;h=45cda3856f130f3d4ab14400059d512a52caba18;hb=522c8ebea4546658b4a5ee6727a0cab64fd72e8b;hp=7c4a2ce86940982c912716a6006423a6840faecb;hpb=c248518fe81b6d2807d3bcbb8a09ae14facce1ad;p=ghc-hetmet.git diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs index 7c4a2ce..45cda38 100644 --- a/compiler/simplCore/Simplify.lhs +++ b/compiler/simplCore/Simplify.lhs @@ -26,10 +26,8 @@ import Id ( Id, idType, idInfo, idArity, isDataConWorkId, idNewDemandInfo, setIdInfo, setIdOccInfo, zapLamIdInfo, setOneShotLambda ) -import IdInfo ( OccInfo(..), isLoopBreaker, - setArityInfo, zapDemandInfo, - setUnfoldingInfo, - occInfo +import IdInfo ( OccInfo(..), setArityInfo, zapDemandInfo, + setUnfoldingInfo, occInfo ) import NewDemand ( isStrictDmd ) import TcGadt ( dataConCanMatch ) @@ -58,7 +56,7 @@ import VarEnv ( elemVarEnv, emptyVarEnv ) import TysPrim ( realWorldStatePrimTy ) import PrelInfo ( realWorldPrimId ) import BasicTypes ( TopLevelFlag(..), isTopLevel, - RecFlag(..), isNonRec + RecFlag(..), isNonRec, isNonRuleLoopBreaker ) import OrdList import List ( nub ) @@ -372,7 +370,6 @@ completeNonRecX env is_strict old_bndr new_bndr new_rhs thing_inside | otherwise = -- Make the arguments atomic if necessary, -- adding suitable bindings - -- pprTrace "completeNonRecX" (ppr new_bndr <+> ppr new_rhs) $ mkAtomicArgsE env is_strict new_rhs $ \ env new_rhs -> completeLazyBind env NotTopLevel old_bndr new_bndr new_rhs `thenSmpl` \ (floats, env) -> @@ -600,14 +597,17 @@ completeLazyBind env top_lvl old_bndr new_bndr new_rhs | otherwise = let - -- Add arity info + -- Arity info new_bndr_info = idInfo new_bndr `setArityInfo` exprArity new_rhs + -- Unfolding info -- Add the unfolding *only* for non-loop-breakers -- Making loop breakers not have an unfolding at all -- means that we can avoid tests in exprIsConApp, for example. -- This is important: if exprIsConApp says 'yes' for a recursive -- thing, then we can get into an infinite loop + + -- Demand info -- If the unfolding is a value, the demand info may -- go pear-shaped, so we nuke it. Example: -- let x = (a,b) in @@ -635,7 +635,7 @@ completeLazyBind env top_lvl old_bndr new_bndr new_rhs returnSmpl (unitFloat env final_id new_rhs, env) where unfolding = mkUnfolding (isTopLevel top_lvl) new_rhs - loop_breaker = isLoopBreaker occ_info + loop_breaker = isNonRuleLoopBreaker occ_info old_info = idInfo old_bndr occ_info = occInfo old_info \end{code} @@ -926,7 +926,7 @@ simplVar env var cont = case substId env var of DoneEx e -> simplExprF (zapSubstEnv env) e cont ContEx tvs ids e -> simplExprF (setSubstEnv env tvs ids) e cont - DoneId var1 occ -> completeCall (zapSubstEnv env) var1 occ cont + DoneId var1 -> completeCall (zapSubstEnv env) var1 cont -- Note [zapSubstEnv] -- The template is already simplified, so don't re-substitute. -- This is VITAL. Consider @@ -940,7 +940,7 @@ simplVar env var cont --------------------------------------------------------- -- Dealing with a call site -completeCall env var occ_info cont +completeCall env var cont = -- Simplify the arguments getDOptsSmpl `thenSmpl` \ dflags -> let @@ -1005,8 +1005,8 @@ completeCall env var occ_info cont interesting_cont = interestingCallContext (notNull args) (notNull arg_infos) call_cont - active_inline = activeInline env var occ_info - maybe_inline = callSiteInline dflags active_inline occ_info + active_inline = activeInline env var + maybe_inline = callSiteInline dflags active_inline var arg_infos interesting_cont in case maybe_inline of { @@ -1341,8 +1341,8 @@ try to eliminate uses of v in the RHSs in favour of case_bndr; that way, there's a chance that v will now only be used once, and hence inlined. -Note 1 -~~~~~~ +Note [no-case-of-case] +~~~~~~~~~~~~~~~~~~~~~~ There is a time we *don't* want to do that, namely when -fno-case-of-case is on. This happens in the first simplifier pass, and enhances full laziness. Here's the bad case: @@ -1353,6 +1353,15 @@ in action in spectral/cichelli/Prog.hs: [(m,n) | m <- [1..max], n <- [1..max]] Hence the check for NoCaseOfCase. +Note [Case of cast] +~~~~~~~~~~~~~~~~~~~ +Consider case (v `cast` co) of x { I# -> + ... (case (v `cast` co) of {...}) ... +We'd like to eliminate the inner case. We can get this neatly by +arranging that inside the outer case we add the unfolding + v |-> x `cast` (sym co) +to v. Then we should inline v at the inner case, cancel the casts, and away we go + Note 2 ~~~~~~ There is another situation when we don't want to do it. If we have @@ -1391,8 +1400,8 @@ eliminate the last case, we must either make sure that x (as well as x1) has unfolding MkT y1. THe straightforward thing to do is to do the binder-swap. So this whole note is a no-op. -Note 3 -~~~~~~ +Note [zapOccInfo] +~~~~~~~~~~~~~~~~~ If we replace the scrutinee, v, by tbe case binder, then we have to nuke any occurrence info (eg IAmDead) in the case binder, because the case-binder now effectively occurs whenever v does. AND we have to do @@ -1418,23 +1427,31 @@ after the outer case, and that makes (a,b) alive. At least we do unless the case binder is guaranteed dead. \begin{code} -simplCaseBinder env (Var v) case_bndr - | not (switchIsOn (getSwitchChecker env) NoCaseOfCase) +simplCaseBinder env scrut case_bndr + | switchIsOn (getSwitchChecker env) NoCaseOfCase + -- See Note [no-case-of-case] + = do { (env, case_bndr') <- simplBinder env case_bndr + ; return (env, case_bndr') } +simplCaseBinder env (Var v) case_bndr -- Failed try [see Note 2 above] -- not (isEvaldUnfolding (idUnfolding v)) - - = simplBinder env (zapOccInfo case_bndr) `thenSmpl` \ (env, case_bndr') -> - returnSmpl (modifyInScope env v case_bndr', case_bndr') + = do { (env, case_bndr') <- simplBinder env (zapOccInfo case_bndr) + ; return (modifyInScope env v case_bndr', case_bndr') } -- We could extend the substitution instead, but it would be -- a hack because then the substitution wouldn't be idempotent -- any more (v is an OutId). And this does just as well. +simplCaseBinder env (Cast (Var v) co) case_bndr -- Note [Case of cast] + = do { (env, case_bndr') <- simplBinder env (zapOccInfo case_bndr) + ; let rhs = Cast (Var case_bndr') (mkSymCoercion co) + ; return (addBinderUnfolding env v rhs, case_bndr') } + simplCaseBinder env other_scrut case_bndr - = simplBinder env case_bndr `thenSmpl` \ (env, case_bndr') -> - returnSmpl (env, case_bndr') + = do { (env, case_bndr') <- simplBinder env case_bndr + ; return (env, case_bndr') } -zapOccInfo :: InId -> InId +zapOccInfo :: InId -> InId -- See Note [zapOccInfo] zapOccInfo b = b `setIdOccInfo` NoOccInfo \end{code} @@ -1565,7 +1582,7 @@ simplDefault env case_bndr' imposs_cons cont (Just rhs) cant_match tys data_con = not (dataConCanMatch data_con tys) simplify_default imposs_cons - = do { let env' = mk_rhs_env env case_bndr' (mkOtherCon imposs_cons) + = do { let env' = addBinderOtherCon env case_bndr' imposs_cons -- Record the constructors that the case-binder *can't* be. ; rhs' <- simplExprC env' rhs cont ; return [(DEFAULT, [], rhs')] } @@ -1593,7 +1610,7 @@ simplAlt env handled_cons case_bndr' cont' (DEFAULT, bndrs, rhs) simplExprC env' rhs cont' `thenSmpl` \ rhs' -> returnSmpl (Just (emptyVarEnv, (DEFAULT, [], rhs'))) where - env' = mk_rhs_env env case_bndr' (mkOtherCon handled_cons) + env' = addBinderOtherCon env case_bndr' handled_cons -- Record the constructors that the case-binder *can't* be. simplAlt env handled_cons case_bndr' cont' (LitAlt lit, bndrs, rhs) @@ -1601,7 +1618,7 @@ simplAlt env handled_cons case_bndr' cont' (LitAlt lit, bndrs, rhs) simplExprC env' rhs cont' `thenSmpl` \ rhs' -> returnSmpl (Just (emptyVarEnv, (LitAlt lit, [], rhs'))) where - env' = mk_rhs_env env case_bndr' (mkUnfolding False (Lit lit)) + env' = addBinderUnfolding env case_bndr' (Lit lit) simplAlt env handled_cons case_bndr' cont' (DataAlt con, vs, rhs) = -- Deal with the pattern-bound variables @@ -1613,10 +1630,9 @@ simplAlt env handled_cons case_bndr' cont' (DataAlt con, vs, rhs) simplBinders env (add_evals con vs) `thenSmpl` \ (env, vs') -> -- Bind the case-binder to (con args) - let unf = mkUnfolding False (mkConApp con con_args) - inst_tys' = tyConAppArgs (idType case_bndr') + let inst_tys' = tyConAppArgs (idType case_bndr') con_args = map Type inst_tys' ++ varsToCoreExprs vs' - env' = mk_rhs_env env case_bndr' unf + env' = addBinderUnfolding env case_bndr' (mkConApp con con_args) in simplExprC env' rhs cont' `thenSmpl` \ rhs' -> returnSmpl (Just (emptyVarEnv, (DataAlt con, vs', rhs'))) @@ -1651,8 +1667,13 @@ simplAlt env handled_cons case_bndr' cont' (DataAlt con, vs, rhs) zap_occ_info | isDeadBinder case_bndr' = \id -> id | otherwise = zapOccInfo -mk_rhs_env env case_bndr' case_bndr_unf - = modifyInScope env case_bndr' (case_bndr' `setIdUnfolding` case_bndr_unf) +addBinderUnfolding :: SimplEnv -> Id -> CoreExpr -> SimplEnv +addBinderUnfolding env bndr rhs + = modifyInScope env bndr (bndr `setIdUnfolding` mkUnfolding False rhs) + +addBinderOtherCon :: SimplEnv -> Id -> [AltCon] -> SimplEnv +addBinderOtherCon env bndr cons + = modifyInScope env bndr (bndr `setIdUnfolding` mkOtherCon cons) \end{code} @@ -1732,7 +1753,7 @@ bind_args env dead_bndr (b:bs) (arg : args) thing_inside -- Note that the binder might be "dead", because it doesn't occur -- in the RHS; and simplNonRecX may therefore discard it via postInlineUnconditionally -- Nevertheless we must keep it if the case-binder is alive, because it may - -- be used in teh con_app + -- be used in the con_app. See Note [zapOccInfo] in simplNonRecX env b' arg $ \ env -> bind_args env dead_bndr bs args thing_inside