diff options
Diffstat (limited to 'compiler/GHC/Core/Opt')
| -rw-r--r-- | compiler/GHC/Core/Opt/Arity.hs | 11 | ||||
| -rw-r--r-- | compiler/GHC/Core/Opt/OccurAnal.hs | 11 | ||||
| -rw-r--r-- | compiler/GHC/Core/Opt/Simplify/Env.hs | 2 | ||||
| -rw-r--r-- | compiler/GHC/Core/Opt/Simplify/Iteration.hs | 323 | ||||
| -rw-r--r-- | compiler/GHC/Core/Opt/Simplify/Utils.hs | 5 |
5 files changed, 202 insertions, 150 deletions
diff --git a/compiler/GHC/Core/Opt/Arity.hs b/compiler/GHC/Core/Opt/Arity.hs index 5ed015281a..cd0463961e 100644 --- a/compiler/GHC/Core/Opt/Arity.hs +++ b/compiler/GHC/Core/Opt/Arity.hs @@ -3088,8 +3088,15 @@ etaExpandToJoinPointRule join_arity rule@(Rule { ru_bndrs = bndrs, ru_rhs = rhs | need_args < 0 = pprPanic "etaExpandToJoinPointRule" (ppr join_arity $$ ppr rule) | otherwise - = rule { ru_bndrs = bndrs ++ new_bndrs, ru_args = args ++ new_args - , ru_rhs = new_rhs } + = rule { ru_bndrs = bndrs ++ new_bndrs + , ru_args = args ++ new_args + , ru_rhs = new_rhs } + -- new_rhs really ought to be occ-analysed (see GHC.Core Note + -- [OccInfo in unfoldings and rules]), but it makes a module loop to + -- do so; it doesn't happen often; and it doesn't really matter if + -- the outer binders have bogus occurrence info; and new_rhs won't + -- have dead code if rhs didn't. + where need_args = join_arity - length args (new_bndrs, new_rhs) = etaBodyForJoinPoint need_args rhs diff --git a/compiler/GHC/Core/Opt/OccurAnal.hs b/compiler/GHC/Core/Opt/OccurAnal.hs index fc374adb99..d463b66c50 100644 --- a/compiler/GHC/Core/Opt/OccurAnal.hs +++ b/compiler/GHC/Core/Opt/OccurAnal.hs @@ -2165,6 +2165,17 @@ So we have a fast-path that keeps the old tree if the occ_bs_env is empty. This just saves a bit of allocation and reconstruction; not a big deal. +This fast path exposes a tricky cornder, though (#22761). Supose we have + Unfolding = \x. let y = foo in x+1 +which includes a dead binding for `y`. In occAnalUnfolding we occ-anal +the unfolding and produce /no/ occurrences of `foo` (since `y` is +dead). But if we discard the occ-analysed syntax tree (which we do on +our fast path), and use the old one, we still /have/ an occurrence of +`foo` -- and that can lead to out-of-scope variables (#22761). + +Solution: always keep occ-analysed trees in unfoldings and rules, so they +have no dead code. See Note [OccInfo in unfoldings and rules] in GHC.Core. + Note [Cascading inlines] ~~~~~~~~~~~~~~~~~~~~~~~~ By default we use an rhsCtxt for the RHS of a binding. This tells the diff --git a/compiler/GHC/Core/Opt/Simplify/Env.hs b/compiler/GHC/Core/Opt/Simplify/Env.hs index 699887190e..759f6e24fa 100644 --- a/compiler/GHC/Core/Opt/Simplify/Env.hs +++ b/compiler/GHC/Core/Opt/Simplify/Env.hs @@ -1065,7 +1065,7 @@ subst_id_bndr env@(SimplEnv { seInScope = in_scope, seIdSubst = id_subst }) -- See Note [Bangs in the Simplifier] !id1 = uniqAway in_scope old_id !id2 = substIdType env id1 - !id3 = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding + !id3 = zapFragileIdInfo id2 -- Zaps rules, worker-info, unfolding -- and fragile OccInfo !new_id = adjust_type id3 diff --git a/compiler/GHC/Core/Opt/Simplify/Iteration.hs b/compiler/GHC/Core/Opt/Simplify/Iteration.hs index e29581a2f0..5b757c0e35 100644 --- a/compiler/GHC/Core/Opt/Simplify/Iteration.hs +++ b/compiler/GHC/Core/Opt/Simplify/Iteration.hs @@ -319,14 +319,14 @@ simplLazyBind :: SimplEnv -> TopLevelFlag -> RecFlag -> InId -> OutId -- Binder, both pre-and post simpl -- Not a JoinId - -- The OutId has IdInfo, except arity, unfolding + -- The OutId has IdInfo (notably RULES), + -- except arity, unfolding -- Ids only, no TyVars -> InExpr -> SimplEnv -- The RHS and its environment -> SimplM (SimplFloats, SimplEnv) -- Precondition: the OutId is already in the InScopeSet of the incoming 'env' -- Precondition: not a JoinId -- Precondition: rhs obeys the let-can-float invariant --- NOT used for JoinIds simplLazyBind env top_lvl is_rec bndr bndr1 rhs rhs_se = assert (isId bndr ) assertPpr (not (isJoinId bndr)) (ppr bndr) $ @@ -398,48 +398,45 @@ simplJoinBind env is_rec cont old_bndr new_bndr rhs rhs_se ; completeBind env (BC_Join is_rec cont) old_bndr new_bndr rhs' } -------------------------- -simplNonRecX :: SimplEnv +simplAuxBind :: SimplEnv -> InId -- Old binder; not a JoinId -> OutExpr -- Simplified RHS -> SimplM (SimplFloats, SimplEnv) --- A specialised variant of simplNonRec used when the RHS is already --- simplified, notably in knownCon. It uses case-binding where necessary. +-- A specialised variant of completeBindX used to construct non-recursive +-- auxiliary bindings, notably in knownCon. +-- +-- The binder comes from a case expression (case binder or alternative) +-- and so does not have rules, inline pragmas etc. -- -- Precondition: rhs satisfies the let-can-float invariant -simplNonRecX env bndr new_rhs - | assertPpr (not (isJoinId bndr)) (ppr bndr) $ +simplAuxBind env bndr new_rhs + | assertPpr (isId bndr && not (isJoinId bndr)) (ppr bndr) $ isDeadBinder bndr -- Not uncommon; e.g. case (a,b) of c { (p,q) -> p } = return (emptyFloats env, env) -- Here c is dead, and we avoid - -- creating the binding c = (a,b) - - | Coercion co <- new_rhs - = return (emptyFloats env, extendCvSubst env bndr co) + -- creating the binding c = (a,b) + -- The cases would be inlined unconditionally by completeBind: + -- but it seems not uncommon, and avoids faff to do it here + -- This is safe because it's only used for auxiliary bindings, which + -- have no NOLINE pragmas, nor RULEs | exprIsTrivial new_rhs -- Short-cut for let x = y in ... - -- This case would ultimately land in postInlineUnconditionally - -- but it seems not uncommon, and avoids a lot of faff to do it here - = return (emptyFloats env - , extendIdSubst env bndr (DoneEx new_rhs Nothing)) + = return ( emptyFloats env + , case new_rhs of + Coercion co -> extendCvSubst env bndr co + _ -> extendIdSubst env bndr (DoneEx new_rhs Nothing) ) | otherwise - = do { (env1, new_bndr) <- simplBinder env bndr - ; let is_strict = isStrictId new_bndr - -- isStrictId: use new_bndr because the InId bndr might not have - -- a fixed runtime representation, which isStrictId doesn't expect - -- c.f. Note [Dark corner with representation polymorphism] - - ; (rhs_floats, rhs1) <- prepareBinding env NotTopLevel NonRecursive is_strict - new_bndr (emptyFloats env) new_rhs - -- NB: it makes a surprisingly big difference (5% in compiler allocation - -- in T9630) to pass 'env' rather than 'env1'. It's fine to pass 'env', - -- because this is simplNonRecX, so bndr is not in scope in the RHS. - - ; (bind_float, env2) <- completeBind (env1 `setInScopeFromF` rhs_floats) - (BC_Let NotTopLevel NonRecursive) + = do { -- ANF-ise the RHS + let !occ_fs = getOccFS bndr + ; (anf_floats, rhs1) <- prepareRhs env NotTopLevel occ_fs new_rhs + ; unless (isEmptyLetFloats anf_floats) (tick LetFloatFromLet) + ; let rhs_floats = emptyFloats env `addLetFloats` anf_floats + + -- Simplify the binder and complete the binding + ; (env1, new_bndr) <- simplBinder (env `setInScopeFromF` rhs_floats) bndr + ; (bind_float, env2) <- completeBind env1 (BC_Let NotTopLevel NonRecursive) bndr new_bndr rhs1 - -- Must pass env1 to completeBind in case simplBinder had to clone, - -- and extended the substitution with [bndr :-> new_bndr] ; return (rhs_floats `addFloats` bind_float, env2) } @@ -761,49 +758,54 @@ prepareRhs :: HasDebugCallStack -- x = Just a -- See Note [prepareRhs] prepareRhs env top_lvl occ rhs0 - = do { (_is_exp, floats, rhs1) <- go 0 rhs0 - ; return (floats, rhs1) } + | is_expandable = anfise rhs0 + | otherwise = return (emptyLetFloats, rhs0) where - go :: Int -> OutExpr -> SimplM (Bool, LetFloats, OutExpr) - go n_val_args (Cast rhs co) - = do { (is_exp, floats, rhs') <- go n_val_args rhs - ; return (is_exp, floats, Cast rhs' co) } - go n_val_args (App fun (Type ty)) - = do { (is_exp, floats, rhs') <- go n_val_args fun - ; return (is_exp, floats, App rhs' (Type ty)) } - go n_val_args (App fun arg) - = do { (is_exp, floats1, fun') <- go (n_val_args+1) fun - ; if is_exp - then do { (floats2, arg') <- makeTrivial env top_lvl topDmd occ arg - ; return (True, floats1 `addLetFlts` floats2, App fun' arg') } - else return (False, emptyLetFloats, App fun arg) - } - go n_val_args (Var fun) - = return (is_exp, emptyLetFloats, Var fun) - where - is_exp = isExpandableApp fun n_val_args -- The fun a constructor or PAP - -- See Note [CONLIKE pragma] in GHC.Types.Basic - -- The definition of is_exp should match that in - -- 'GHC.Core.Opt.OccurAnal.occAnalApp' - - go n_val_args (Tick t rhs) + -- We can' use exprIsExpandable because the WHOLE POINT is that + -- we want to treat (K <big>) as expandable, because we are just + -- about "anfise" the <big> expression. exprIsExpandable would + -- just say no! + is_expandable = go rhs0 0 + where + go (Var fun) n_val_args = isExpandableApp fun n_val_args + go (App fun arg) n_val_args + | isTypeArg arg = go fun n_val_args + | otherwise = go fun (n_val_args + 1) + go (Cast rhs _) n_val_args = go rhs n_val_args + go (Tick _ rhs) n_val_args = go rhs n_val_args + go _ _ = False + + anfise :: OutExpr -> SimplM (LetFloats, OutExpr) + anfise (Cast rhs co) + = do { (floats, rhs') <- anfise rhs + ; return (floats, Cast rhs' co) } + anfise (App fun (Type ty)) + = do { (floats, rhs') <- anfise fun + ; return (floats, App rhs' (Type ty)) } + anfise (App fun arg) + = do { (floats1, fun') <- anfise fun + ; (floats2, arg') <- makeTrivial env top_lvl topDmd occ arg + ; return (floats1 `addLetFlts` floats2, App fun' arg') } + anfise (Var fun) + = return (emptyLetFloats, Var fun) + + anfise (Tick t rhs) -- We want to be able to float bindings past this -- tick. Non-scoping ticks don't care. | tickishScoped t == NoScope - = do { (is_exp, floats, rhs') <- go n_val_args rhs - ; return (is_exp, floats, Tick t rhs') } + = do { (floats, rhs') <- anfise rhs + ; return (floats, Tick t rhs') } -- On the other hand, for scoping ticks we need to be able to -- copy them on the floats, which in turn is only allowed if -- we can obtain non-counting ticks. | (not (tickishCounts t) || tickishCanSplit t) - = do { (is_exp, floats, rhs') <- go n_val_args rhs + = do { (floats, rhs') <- anfise rhs ; let tickIt (id, expr) = (id, mkTick (mkNoCount t) expr) floats' = mapLetFloats floats tickIt - ; return (is_exp, floats', Tick t rhs') } + ; return (floats', Tick t rhs') } - go _ other - = return (False, emptyLetFloats, other) + anfise other = return (emptyLetFloats, other) makeTrivialArg :: HasDebugCallStack => SimplEnv -> ArgSpec -> SimplM (LetFloats, ArgSpec) makeTrivialArg env arg@(ValArg { as_arg = e, as_dmd = dmd }) @@ -1244,7 +1246,7 @@ simplExprF1 env (Let (NonRec bndr rhs) body) cont | otherwise = {-#SCC "simplNonRecE" #-} - simplNonRecE env False bndr (rhs, env) body cont + simplNonRecE env FromLet bndr (rhs, env) body cont {- Note [Avoiding space leaks in OutType] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1505,8 +1507,9 @@ rebuild env expr cont StrictArg { sc_fun = fun, sc_cont = cont, sc_fun_ty = fun_ty } -> rebuildCall env (addValArgTo fun expr fun_ty ) cont - StrictBind { sc_bndr = b, sc_body = body, sc_env = se, sc_cont = cont } - -> completeBindX (se `setInScopeFromE` env) b expr body cont + StrictBind { sc_bndr = b, sc_body = body, sc_env = se + , sc_cont = cont, sc_from = from_what } + -> completeBindX (se `setInScopeFromE` env) from_what b expr body cont ApplyToTy { sc_arg_ty = ty, sc_cont = cont} -> rebuild env (App expr (Type ty)) cont @@ -1518,25 +1521,48 @@ rebuild env expr cont ; rebuild env (App expr arg') cont } completeBindX :: SimplEnv + -> FromWhat -> InId -> OutExpr -- Bind this Id to this (simplified) expression -- (the let-can-float invariant may not be satisfied) - -> InExpr -- In this lambda + -> InExpr -- In this body -> SimplCont -- Consumed by this continuation -> SimplM (SimplFloats, OutExpr) -completeBindX env bndr rhs body cont - | needsCaseBinding (idType bndr) rhs -- Enforcing the let-can-float-invariant - = do { (env1, bndr1) <- simplNonRecBndr env bndr - ; (floats, expr') <- simplLam env1 body cont +completeBindX env from_what bndr rhs body cont + | FromBeta arg_ty <- from_what + , needsCaseBinding arg_ty rhs -- Enforcing the let-can-float-invariant + = do { (env1, bndr1) <- simplNonRecBndr env bndr -- Lambda binders don't have rules + ; (floats, expr') <- simplNonRecBody env1 from_what body cont -- Do not float floats past the Case binder below ; let expr'' = wrapFloats floats expr' - ; let case_expr = Case rhs bndr1 (contResultType cont) [Alt DEFAULT [] expr''] + case_expr = Case rhs bndr1 (contResultType cont) [Alt DEFAULT [] expr''] ; return (emptyFloats env, case_expr) } - | otherwise - = do { (floats1, env') <- simplNonRecX env bndr rhs - ; (floats2, expr') <- simplLam env' body cont - ; return (floats1 `addFloats` floats2, expr') } + | otherwise -- Make a let-binding + = do { (env1, bndr1) <- simplNonRecBndr env bndr + ; (env2, bndr2) <- addBndrRules env1 bndr bndr1 (BC_Let NotTopLevel NonRecursive) + + ; let is_strict = isStrictId bndr2 + -- isStrictId: use simplified binder because the InId bndr might not have + -- a fixed runtime representation, which isStrictId doesn't expect + -- c.f. Note [Dark corner with representation polymorphism] + + ; (rhs_floats, rhs1) <- prepareBinding env NotTopLevel NonRecursive is_strict + bndr2 (emptyFloats env) rhs + -- NB: it makes a surprisingly big difference (5% in compiler allocation + -- in T9630) to pass 'env' rather than 'env1'. It's fine to pass 'env', + -- because this is simplNonRecX, so bndr is not in scope in the RHS. + + ; (bind_float, env2) <- completeBind (env2 `setInScopeFromF` rhs_floats) + (BC_Let NotTopLevel NonRecursive) + bndr bndr2 rhs1 + -- Must pass env1 to completeBind in case simplBinder had to clone, + -- and extended the substitution with [bndr :-> new_bndr] + + -- Simplify the body + ; (body_floats, body') <- simplNonRecBody env2 from_what body cont + ; let all_floats = rhs_floats `addFloats` bind_float `addFloats` body_floats + ; return ( all_floats, body' ) } {- ************************************************************************ @@ -1674,6 +1700,14 @@ simplArg env dup_flag fun_ty arg_env arg ************************************************************************ -} +simplNonRecBody :: SimplEnv -> FromWhat + -> InExpr -> SimplCont + -> SimplM (SimplFloats, OutExpr) +simplNonRecBody env from_what body cont + = case from_what of + FromLet -> simplExprF env body cont + FromBeta {} -> simplLam env body cont + simplLam :: SimplEnv -> InExpr -> SimplCont -> SimplM (SimplFloats, OutExpr) @@ -1690,15 +1724,24 @@ simpl_lam env bndr body (ApplyToTy { sc_arg_ty = arg_ty, sc_cont = cont }) -- Value beta-reduction simpl_lam env bndr body (ApplyToVal { sc_arg = arg, sc_env = arg_se - , sc_cont = cont, sc_dup = dup }) - | isSimplified dup -- Don't re-simplify if we've simplified it once - -- See Note [Avoiding exponential behaviour] + , sc_cont = cont, sc_dup = dup + , sc_hole_ty = fun_ty}) = do { tick (BetaReduction bndr) - ; completeBindX env bndr arg body cont } + ; let arg_ty = funArgTy fun_ty + ; if | isSimplified dup -- Don't re-simplify if we've simplified it once + -- Including don't preInlineUnconditionally + -- See Note [Avoiding exponential behaviour] + -> completeBindX env (FromBeta arg_ty) bndr arg body cont + + | Just env' <- preInlineUnconditionally env NotTopLevel bndr arg arg_se + , not (needsCaseBinding arg_ty arg) + -- Ok to test arg::InExpr in needsCaseBinding because + -- exprOkForSpeculation is stable under simplification + -> do { tick (PreInlineUnconditionally bndr) + ; simplLam env' body cont } - | otherwise -- See Note [Avoiding exponential behaviour] - = do { tick (BetaReduction bndr) - ; simplNonRecE env True bndr (arg, arg_se) body cont } + | otherwise + -> simplNonRecE env (FromBeta arg_ty) bndr (arg, arg_se) body cont } -- Discard a non-counting tick on a lambda. This may change the -- cost attribution slightly (moving the allocation of the @@ -1730,8 +1773,7 @@ simplLamBndrs env bndrs = mapAccumLM simplLamBndr env bndrs ------------------ simplNonRecE :: SimplEnv - -> Bool -- True <=> from a lambda - -- False <=> from a let + -> FromWhat -> InId -- The binder, always an Id -- Never a join point -> (InExpr, SimplEnv) -- Rhs of binding (or arg of lambda) @@ -1740,56 +1782,48 @@ simplNonRecE :: SimplEnv -> SimplM (SimplFloats, OutExpr) -- simplNonRecE is used for --- * non-top-level non-recursive non-join-point lets in expressions --- * beta reduction +-- * from=FromLet: a non-top-level non-recursive non-join-point let-expression +-- * from=FromBeta: a binding arising from a beta reduction -- --- simplNonRec env b (rhs, rhs_se) body k +-- simplNonRecE env b (rhs, rhs_se) body k -- = let env in -- cont< let b = rhs_se(rhs) in body > -- -- It deals with strict bindings, via the StrictBind continuation, -- which may abort the whole process. -- --- from_lam=False => the RHS satisfies the let-can-float invariant +-- from_what=FromLet => the RHS satisfies the let-can-float invariant -- Otherwise it may or may not satisfy it. -simplNonRecE env from_lam bndr (rhs, rhs_se) body cont - = assert (isId bndr && not (isJoinId bndr) ) $ - do { (env1, bndr1) <- simplNonRecBndr env bndr - ; let needs_case_binding = needsCaseBinding (idType bndr1) rhs - -- See Note [Dark corner with representation polymorphism] - -- If from_lam=False then needs_case_binding is False, - -- because the binding started as a let, which must - -- satisfy let-can-float - - ; if | from_lam && not needs_case_binding - -- If not from_lam we are coming from a (NonRec bndr rhs) binding - -- and preInlineUnconditionally has been done already; - -- no need to repeat it. But for lambdas we must be careful about - -- preInlineUndonditionally: consider (\(x:Int#). 3) (error "urk") - -- We must not drop the (error "urk"). - , Just env' <- preInlineUnconditionally env NotTopLevel bndr rhs rhs_se - -> do { tick (PreInlineUnconditionally bndr) - ; -- pprTrace "preInlineUncond" (ppr bndr <+> ppr rhs) $ - simplLam env' body cont } - - -- Deal with strict bindings - | isStrictId bndr1 && seCaseCase env - || from_lam && needs_case_binding - -- The important bit here is needs_case_binds; but no need to - -- test it if from_lam is False because then needs_case_binding is False too - -- NB: either way, the RHS may or may not satisfy let-can-float - -- but that's ok for StrictBind. - -> simplExprF (rhs_se `setInScopeFromE` env) rhs - (StrictBind { sc_bndr = bndr, sc_body = body - , sc_env = env, sc_cont = cont, sc_dup = NoDup }) - - -- Deal with lazy bindings - | otherwise - -> do { (env2, bndr2) <- addBndrRules env1 bndr bndr1 (BC_Let NotTopLevel NonRecursive) - ; (floats1, env3) <- simplLazyBind env2 NotTopLevel NonRecursive bndr bndr2 rhs rhs_se - ; (floats2, expr') <- simplLam env3 body cont - ; return (floats1 `addFloats` floats2, expr') } } +simplNonRecE env from_what bndr (rhs, rhs_se) body cont + | assert (isId bndr && not (isJoinId bndr) ) $ + is_strict_bind + = -- Evaluate RHS strictly + simplExprF (rhs_se `setInScopeFromE` env) rhs + (StrictBind { sc_bndr = bndr, sc_body = body, sc_from = from_what + , sc_env = env, sc_cont = cont, sc_dup = NoDup }) + + | otherwise -- Evaluate RHS lazily + = do { (env1, bndr1) <- simplNonRecBndr env bndr + ; (env2, bndr2) <- addBndrRules env1 bndr bndr1 (BC_Let NotTopLevel NonRecursive) + ; (floats1, env3) <- simplLazyBind env2 NotTopLevel NonRecursive + bndr bndr2 rhs rhs_se + ; (floats2, expr') <- simplNonRecBody env3 from_what body cont + ; return (floats1 `addFloats` floats2, expr') } + + where + is_strict_bind = case from_what of + FromBeta arg_ty | isUnliftedType arg_ty -> True + -- If we are coming from a beta-reduction (FromBeta) we must + -- establish the let-can-float invariant, so go via StrictBind + -- If not, the invariant holds already, and it's optional. + -- Using arg_ty: see Note [Dark corner with representation polymorphism] + -- e.g (\r \(a::TYPE r) \(x::a). blah) @LiftedRep @Int arg + -- When we come to `x=arg` we myst choose lazy/strict correctly + -- It's wrong to err in either directly + + _ -> seCaseCase env && isStrUsedDmd (idDemandInfo bndr) + ------------------ simplRecE :: SimplEnv @@ -1835,7 +1869,7 @@ Note [Avoiding exponential behaviour] One way in which we can get exponential behaviour is if we simplify a big expression, and then re-simplify it -- and then this happens in a deeply-nested way. So we must be jolly careful about re-simplifying -an expression. That is why simplNonRecX does not try +an expression (#13379). That is why simplNonRecX does not try preInlineUnconditionally (unlike simplNonRecE). Example: @@ -2618,15 +2652,10 @@ Is this inefficient? Not really: we are about to walk over the result of the rule firing to simplify it, so occurrence analysis is at most a constant factor. -Possible improvement: occ-anal the rules when putting them in the -database; and in the simplifier just occ-anal the OutExpr arguments. -But that's more complicated and the rule RHS is usually tiny; so I'm -just doing the simple thing. - -Historical note: previously we did occ-anal the rules in Rule.hs, -but failed to occ-anal the OutExpr arguments, which led to the -nasty performance problem described above. - +Note, however, that the rule RHS is /already/ occ-analysed; see +Note [OccInfo in unfoldings and rules] in GHC.Core. There is something +unsatisfactory about doing it twice; but the rule RHS is usually very +small, and this is simple. Note [Optimising tagToEnum#] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -2930,7 +2959,7 @@ rebuildCase env scrut case_bndr alts cont where simple_rhs env wfloats case_bndr_rhs bs rhs = assert (null bs) $ - do { (floats1, env') <- simplNonRecX env case_bndr case_bndr_rhs + do { (floats1, env') <- simplAuxBind env case_bndr case_bndr_rhs -- scrut is a constructor application, -- hence satisfies let-can-float invariant ; (floats2, expr') <- simplExprF env' rhs cont @@ -2997,7 +3026,7 @@ rebuildCase env scrut case_bndr alts@[Alt _ bndrs rhs] cont | all_dead_bndrs , doCaseToLet scrut case_bndr = do { tick (CaseElim case_bndr) - ; (floats1, env') <- simplNonRecX env case_bndr scrut + ; (floats1, env') <- simplAuxBind env case_bndr scrut ; (floats2, expr') <- simplExprF env' rhs cont ; return (floats1 `addFloats` floats2, expr') } @@ -3483,12 +3512,11 @@ knownCon env scrut dc_floats dc dc_ty_args dc_args bndr bs rhs cont bind_args env' (b:bs') (arg : args) = assert (isId b) $ do { let b' = zap_occ b - -- Note that the binder might be "dead", because it doesn't - -- occur in the RHS; and simplNonRecX may therefore discard - -- it via postInlineUnconditionally. + -- zap_occ: the binder might be "dead", because it doesn't + -- occur in the RHS; and simplAuxBind may therefore discard it. -- Nevertheless we must keep it if the case-binder is alive, -- because it may be used in the con_app. See Note [knownCon occ info] - ; (floats1, env2) <- simplNonRecX env' b' arg -- arg satisfies let-can-float invariant + ; (floats1, env2) <- simplAuxBind env' b' arg -- arg satisfies let-can-float invariant ; (floats2, env3) <- bind_args env2 bs' args ; return (floats1 `addFloats` floats2, env3) } @@ -3514,7 +3542,7 @@ knownCon env scrut dc_floats dc dc_ty_args dc_args bndr bs rhs cont ; let con_app = Var (dataConWorkId dc) `mkTyApps` dc_ty_args `mkApps` dc_args - ; simplNonRecX env bndr con_app } + ; simplAuxBind env bndr con_app } ------------------- missingAlt :: SimplEnv -> Id -> [InAlt] -> SimplCont @@ -3621,15 +3649,15 @@ mkDupableContWithDmds env dmds (TickIt t cont) ; return (floats, TickIt t cont') } mkDupableContWithDmds env _ - (StrictBind { sc_bndr = bndr, sc_body = body + (StrictBind { sc_bndr = bndr, sc_body = body, sc_from = from_what , sc_env = se, sc_cont = cont}) -- See Note [Duplicating StrictBind] -- K[ let x = <> in b ] --> join j x = K[ b ] -- j <> = do { let sb_env = se `setInScopeFromE` env ; (sb_env1, bndr') <- simplBinder sb_env bndr - ; (floats1, join_inner) <- simplLam sb_env1 body cont - -- No need to use mkDupableCont before simplLam; we + ; (floats1, join_inner) <- simplNonRecBody sb_env1 from_what body cont + -- No need to use mkDupableCont before simplNonRecBody; we -- use cont once here, and then share the result if necessary ; let join_body = wrapFloats floats1 join_inner @@ -3757,6 +3785,7 @@ mkDupableStrictBind env arg_bndr join_rhs res_ty , StrictBind { sc_bndr = arg_bndr , sc_body = join_rhs , sc_env = zapSubstEnv env + , sc_from = FromLet -- See Note [StaticEnv invariant] in GHC.Core.Opt.Simplify.Utils , sc_dup = OkToDup , sc_cont = mkBoringStop res_ty } ) @@ -4430,7 +4459,9 @@ simplRules env mb_new_id rules bind_cxt ; return (rule { ru_bndrs = bndrs' , ru_fn = fn_name' , ru_args = args' - , ru_rhs = rhs' }) } + , ru_rhs = occurAnalyseExpr rhs' }) } + -- Remember to occ-analyse, to drop dead code. + -- See Note [OccInfo in unfoldings and rules] in GHC.Core {- Note [Simplifying the RHS of a RULE] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ diff --git a/compiler/GHC/Core/Opt/Simplify/Utils.hs b/compiler/GHC/Core/Opt/Simplify/Utils.hs index 5c01132359..0a09183bf4 100644 --- a/compiler/GHC/Core/Opt/Simplify/Utils.hs +++ b/compiler/GHC/Core/Opt/Simplify/Utils.hs @@ -21,7 +21,7 @@ module GHC.Core.Opt.Simplify.Utils ( BindContext(..), bindContextLevel, -- The continuation type - SimplCont(..), DupFlag(..), StaticEnv, + SimplCont(..), DupFlag(..), FromWhat(..), StaticEnv, isSimplified, contIsStop, contIsDupable, contResultType, contHoleType, contHoleScaling, contIsTrivial, contArgs, contIsRhs, @@ -192,6 +192,7 @@ data SimplCont -- or, equivalently, = K[ (\x.b) e ] { sc_dup :: DupFlag -- See Note [DupFlag invariants] , sc_bndr :: InId + , sc_from :: FromWhat , sc_body :: InExpr , sc_env :: StaticEnv -- See Note [StaticEnv invariant] , sc_cont :: SimplCont } @@ -213,6 +214,8 @@ data SimplCont type StaticEnv = SimplEnv -- Just the static part is relevant +data FromWhat = FromLet | FromBeta OutType + -- See Note [DupFlag invariants] data DupFlag = NoDup -- Unsimplified, might be big | Simplified -- Simplified |