import PprCore ( pprParendExpr, pprCoreExpr )
import CoreUnfold ( mkUnfolding, callSiteInline, CallCtxt(..) )
import CoreUtils
+import CoreArity ( exprArity )
import Rules ( lookupRule, getRules )
import BasicTypes ( isMarkedStrict )
import CostCentre ( currentCCS )
RecFlag(..), isNonRuleLoopBreaker )
import Maybes ( orElse )
import Data.List ( mapAccumL )
-import MonadUtils ( foldlM )
-import StaticFlags ( opt_PassCaseBndrToJoinPoints )
import Outputable
import FastString
\end{code}
; (env', rhs')
<- if not (doFloatFromRhs top_lvl is_rec False body2 body_env2)
then -- No floating, just wrap up!
- do { rhs' <- mkLam tvs' (wrapFloats body_env2 body2)
+ do { rhs' <- mkLam env tvs' (wrapFloats body_env2 body2)
; return (env, rhs') }
else if null tvs then -- Simple floating
else -- Do type-abstraction first
do { tick LetFloatFromLet
; (poly_binds, body3) <- abstractFloats tvs' body_env2 body2
- ; rhs' <- mkLam tvs' body3
- ; env' <- foldlM (addPolyBind top_lvl) env poly_binds
+ ; rhs' <- mkLam env tvs' body3
+ ; let env' = foldl (addPolyBind top_lvl) env poly_binds
; return (env', rhs') }
; completeBind env' top_lvl bndr bndr1 rhs' }
where
is_val = n_val_args > 0 -- There is at least one arg
-- ...and the fun a constructor or PAP
- && (isDataConWorkId fun || n_val_args < idArity fun)
+ && (isConLikeId fun || n_val_args < idArity fun)
go _ env other
= return (False, env, other)
\end{code}
-- * or by adding to the floats in the envt
completeBind env top_lvl old_bndr new_bndr new_rhs
- = do { let old_info = idInfo old_bndr
- old_unf = unfoldingInfo old_info
- occ_info = occInfo old_info
+ | postInlineUnconditionally env top_lvl new_bndr occ_info new_rhs unfolding
+ -- Inline and discard the binding
+ = do { tick (PostInlineUnconditionally old_bndr)
+ ; -- pprTrace "postInlineUnconditionally" (ppr old_bndr <+> ppr new_bndr <+> ppr new_rhs) $
+ return (extendIdSubst env old_bndr (DoneEx new_rhs)) }
+ -- Use the substitution to make quite, quite sure that the
+ -- substitution will happen, since we are going to discard the binding
- ; new_unfolding <- simplUnfolding env top_lvl old_bndr occ_info old_unf new_rhs
-
- ; if postInlineUnconditionally env top_lvl new_bndr occ_info new_rhs new_unfolding
- -- Inline and discard the binding
- then do { tick (PostInlineUnconditionally old_bndr)
- ; return (extendIdSubst env old_bndr (DoneEx new_rhs)) }
- -- Use the substitution to make quite, quite sure that the
- -- substitution will happen, since we are going to discard the binding
-
- else return (addNonRecWithUnf env new_bndr new_rhs new_unfolding) }
-
-------------------------------
-addPolyBind :: TopLevelFlag -> SimplEnv -> OutBind -> SimplM SimplEnv
+ | otherwise
+ = return (addNonRecWithUnf env new_bndr new_rhs unfolding wkr)
+ where
+ unfolding | omit_unfolding = NoUnfolding
+ | otherwise = mkUnfolding (isTopLevel top_lvl) new_rhs
+ old_info = idInfo old_bndr
+ occ_info = occInfo old_info
+ wkr = substWorker env (workerInfo old_info)
+ omit_unfolding = isNonRuleLoopBreaker occ_info
+ -- or not (activeInline env old_bndr)
+ -- Do *not* trim the unfolding in SimplGently, else
+ -- the specialiser can't see it!
+
+-----------------
+addPolyBind :: TopLevelFlag -> SimplEnv -> OutBind -> SimplEnv
-- Add a new binding to the environment, complete with its unfolding
-- but *do not* do postInlineUnconditionally, because we have already
-- processed some of the scope of the binding
-- opportunity to inline 'y' too.
addPolyBind top_lvl env (NonRec poly_id rhs)
- = do { unfolding <- simplUnfolding env top_lvl poly_id NoOccInfo noUnfolding rhs
- -- Assumes that poly_id did not have an INLINE prag
- -- which is perhaps wrong. ToDo: think about this
- ; return (addNonRecWithUnf env poly_id rhs unfolding) }
+ = addNonRecWithUnf env poly_id rhs unfolding NoWorker
+ where
+ unfolding | not (activeInline env poly_id) = NoUnfolding
+ | otherwise = mkUnfolding (isTopLevel top_lvl) rhs
+ -- addNonRecWithInfo adds the new binding in the
+ -- proper way (ie complete with unfolding etc),
+ -- and extends the in-scope set
-addPolyBind _ env bind@(Rec _) = return (extendFloats env bind)
+addPolyBind _ env bind@(Rec _) = extendFloats env bind
-- Hack: letrecs are more awkward, so we extend "by steam"
-- without adding unfoldings etc. At worst this leads to
-- more simplifier iterations
-------------------------------
+-----------------
addNonRecWithUnf :: SimplEnv
- -> OutId -> OutExpr -- New binder and RHS
- -> Unfolding -- New unfolding
- -> SimplEnv
-addNonRecWithUnf env new_bndr new_rhs new_unfolding
- = let new_arity = exprArity new_rhs
- old_arity = idArity new_bndr
- info1 = idInfo new_bndr `setArityInfo` new_arity
-
- -- Unfolding info: Note [Setting the new unfolding]
- info2 = info1 `setUnfoldingInfo` new_unfolding
-
- -- Demand info: Note [Setting the demand info]
- info3 | isEvaldUnfolding new_unfolding = zapDemandInfo info2 `orElse` info2
- | otherwise = info2
-
- final_id = new_bndr `setIdInfo` info3
- dmd_arity = length $ fst $ splitStrictSig $ idNewStrictness new_bndr
- in
- ASSERT( isId new_bndr )
+ -> OutId -> OutExpr -- New binder and RHS
+ -> Unfolding -> WorkerInfo -- and unfolding
+ -> SimplEnv
+-- Add suitable IdInfo to the Id, add the binding to the floats, and extend the in-scope set
+addNonRecWithUnf env new_bndr rhs unfolding wkr
+ = ASSERT( isId new_bndr )
WARN( new_arity < old_arity || new_arity < dmd_arity,
- (ppr final_id <+> ppr old_arity <+> ppr new_arity <+> ppr dmd_arity) $$ ppr new_rhs )
-
- final_id `seq` -- This seq forces the Id, and hence its IdInfo,
- -- and hence any inner substitutions
- -- pprTrace "Binding" (ppr final_id <+> ppr unfolding) $
- addNonRec env final_id new_rhs
- -- The addNonRec adds it to the in-scope set too
-
-
-------------------------------
-simplUnfolding :: SimplEnv-> TopLevelFlag
- -> Id -- Debug output only
- -> OccInfo -> Unfolding -> OutExpr
- -> SimplM Unfolding
-simplUnfolding env top_lvl bndr occ_info old_unf new_rhs -- Note [Setting the new unfolding]
- | omit_unfolding = WARN( is_inline_rule, ppr bndr ) return NoUnfolding
- | is_inline_rule = return (substUnfolding env is_top_lvl old_unf)
- | otherwise = return (mkUnfolding is_top_lvl new_rhs)
+ (ppr final_id <+> ppr old_arity <+> ppr new_arity <+> ppr dmd_arity) $$ ppr rhs )
+ final_id `seq` -- This seq forces the Id, and hence its IdInfo,
+ -- and hence any inner substitutions
+ addNonRec env final_id rhs
+ -- The addNonRec adds it to the in-scope set too
where
- is_top_lvl = isTopLevel top_lvl
- is_inline_rule = isInlineRule old_unf
- omit_unfolding = isNonRuleLoopBreaker occ_info
-\end{code}
-
-
-Note [Setting the new unfolding]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-* If there's an INLINE pragma, we use substUnfolding to retain the
- supplied inlining
-
-* If not, we make an unfolding from the new RHS. But *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
+ dmd_arity = length $ fst $ splitStrictSig $ idNewStrictness new_bndr
+ old_arity = idArity new_bndr
-If there's an INLINE pragma on a loop breaker, we simply discard it
-(with a DEBUG warning). The desugarer complains about binding groups
-that look likely to trigger this behaviour.
+ -- Arity info
+ new_arity = exprArity rhs
+ new_bndr_info = idInfo new_bndr `setArityInfo` new_arity
+
+ -- 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
+ -- case x of (p,q) -> h p q x
+ -- Here x is certainly demanded. But after we've nuked
+ -- the case, we'll get just
+ -- let x = (a,b) in h a b x
+ -- and now x is not demanded (I'm assuming h is lazy)
+ -- This really happens. Similarly
+ -- let f = \x -> e in ...f..f...
+ -- After inlining f at some of its call sites the original binding may
+ -- (for example) be no longer strictly demanded.
+ -- The solution here is a bit ad hoc...
+ info_w_unf = new_bndr_info `setUnfoldingInfo` unfolding
+ `setWorkerInfo` wkr
+
+ final_info | isEvaldUnfolding unfolding = zapDemandInfo info_w_unf `orElse` info_w_unf
+ | otherwise = info_w_unf
+
+ final_id = new_bndr `setIdInfo` final_info
+\end{code}
-Note [Setting the 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
- case x of (p,q) -> h p q x
-Here x is certainly demanded. But after we've nuked
-the case, we'll get just
- let x = (a,b) in h a b x
-and now x is not demanded (I'm assuming h is lazy)
-This really happens. Similarly
- let f = \x -> e in ...f..f...
-After inlining f at some of its call sites the original binding may
-(for example) be no longer strictly demanded.
-The solution here is a bit ad hoc...
-
%************************************************************************
%* *
simplLam env bndrs body cont
= do { (env', bndrs') <- simplLamBndrs env bndrs
; body' <- simplExpr env' body
- ; new_lam <- mkLam bndrs' body'
+ ; new_lam <- mkLam env' bndrs' body'
; rebuild env' new_lam cont }
------------------
simplNonRecE :: SimplEnv
- -> InBndr -- The binder
+ -> InId -- The binder
-> (InExpr, SimplEnv) -- Rhs of binding (or arg of lambda)
-> ([InBndr], InExpr) -- Body of the let/lambda
-- \xs.e
= do { e' <- simplExpr (setEnclosingCC env currentCCS) e
; rebuild env (mkSCC cc e') cont }
-simplNote env (CoreNote s) e cont
- = do { e' <- simplExpr env e
- ; rebuild env (Note (CoreNote s) e') cont }
+-- See notes with SimplMonad.inlineMode
+simplNote env InlineMe e cont
+ | Just (inside, outside) <- splitInlineCont cont -- Boring boring continuation; see notes above
+ = do { -- Don't inline inside an INLINE expression
+ e' <- simplExprC (setMode inlineMode env) e inside
+ ; rebuild env (mkInlineMe e') outside }
+
+ | otherwise -- Dissolve the InlineMe note if there's
+ -- an interesting context of any kind to combine with
+ -- (even a type application -- anything except Stop)
+ = simplExprF env e cont
+
+simplNote env (CoreNote s) e cont = do
+ e' <- simplExpr env e
+ rebuild env (Note (CoreNote s) e') cont
\end{code}
after the outer case, and that makes (a,b) alive. At least we do unless
the case binder is guaranteed dead.
-In practice, the scrutinee is almost always a variable, so we pretty
-much always zap the OccInfo of the binders. It doesn't matter much though.
-
-
-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 [Improving seq]
~~~~~~~~~~~~~~~~~~~
Consider
LiberateCase gets to see it.)
-Historical note [no-case-of-case]
-~~~~~~~~~~~~~~~~~~~~~~
-We *used* to suppress the binder-swap in case expressoins when
--fno-case-of-case is on. Old remarks:
- "This happens in the first simplifier pass,
- and enhances full laziness. Here's the bad case:
- f = \ y -> ...(case x of I# v -> ...(case x of ...) ... )
- If we eliminate the inner case, we trap it inside the I# v -> arm,
- which might prevent some full laziness happening. I've seen this
- in action in spectral/cichelli/Prog.hs:
- [(m,n) | m <- [1..max], n <- [1..max]]
- Hence the check for NoCaseOfCase."
-However, now the full-laziness pass itself reverses the binder-swap, so this
-check is no longer necessary.
-
-Historical note [Suppressing the case binder-swap]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-There is another situation when it might make sense to suppress the
-case-expression binde-swap. If we have
-
- case x of w1 { DEFAULT -> case x of w2 { A -> e1; B -> e2 }
- ...other cases .... }
-
-We'll perform the binder-swap for the outer case, giving
-
- case x of w1 { DEFAULT -> case w1 of w2 { A -> e1; B -> e2 }
- ...other cases .... }
-
-But there is no point in doing it for the inner case, because w1 can't
-be inlined anyway. Furthermore, doing the case-swapping involves
-zapping w2's occurrence info (see paragraphs that follow), and that
-forces us to bind w2 when doing case merging. So we get
-
- case x of w1 { A -> let w2 = w1 in e1
- B -> let w2 = w1 in e2
- ...other cases .... }
-
-This is plain silly in the common case where w2 is dead.
-
-Even so, I can't see a good way to implement this idea. I tried
-not doing the binder-swap if the scrutinee was already evaluated
-but that failed big-time:
-
- data T = MkT !Int
-
- case v of w { MkT x ->
- case x of x1 { I# y1 ->
- case x of x2 { I# y2 -> ...
-
-Notice that because MkT is strict, x is marked "evaluated". But to
-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.
\begin{code}
mkDupableAlt :: SimplEnv -> OutId -> (AltCon, [CoreBndr], CoreExpr)
-> SimplM (SimplEnv, (AltCon, [CoreBndr], CoreExpr))
-mkDupableAlt env case_bndr1 (con, bndrs1, rhs1)
- | exprIsDupable rhs1 -- Note [Small alternative rhs]
- = return (env, (con, bndrs1, rhs1))
+mkDupableAlt env case_bndr' (con, bndrs', rhs')
+ | exprIsDupable rhs' -- Note [Small alternative rhs]
+ = return (env, (con, bndrs', rhs'))
| otherwise
- = do { let abstract_over bndr
+ = do { let rhs_ty' = exprType rhs'
+ used_bndrs' = filter abstract_over (case_bndr' : bndrs')
+ abstract_over bndr
| isTyVar bndr = True -- Abstract over all type variables just in case
| otherwise = not (isDeadBinder bndr)
-- The deadness info on the new Ids is preserved by simplBinders
- inst_tys1 = tyConAppArgs (idType case_bndr1)
- con_app dc = mkConApp dc (map Type inst_tys1 ++ varsToCoreExprs bndrs1)
-
- (rhs2, final_bndrs) -- See Note [Passing the case binder to join points]
- | isDeadBinder case_bndr1
- = (rhs1, filter abstract_over bndrs1)
- | opt_PassCaseBndrToJoinPoints, not (null bndrs1)
- = (rhs1, (case_bndr1 : filter abstract_over bndrs1))
- | otherwise
- = case con of
- DataAlt dc -> (Let (NonRec case_bndr1 (con_app dc)) rhs1, bndrs1)
- LitAlt lit -> ASSERT( null bndrs1 ) (Let (NonRec case_bndr1 (Lit lit)) rhs1, [])
- DEFAULT -> ASSERT( null bndrs1 ) (rhs1, [case_bndr1])
-
- ; (final_bndrs1, final_args) -- Note [Join point abstraction]
- <- if (any isId final_bndrs)
- then return (final_bndrs, varsToCoreExprs final_bndrs)
+ ; (final_bndrs', final_args) -- Note [Join point abstraction]
+ <- if (any isId used_bndrs')
+ then return (used_bndrs', varsToCoreExprs used_bndrs')
else do { rw_id <- newId (fsLit "w") realWorldStatePrimTy
- ; return (rw_id : final_bndrs,
- Var realWorldPrimId : varsToCoreExprs final_bndrs) }
+ ; return ([rw_id], [Var realWorldPrimId]) }
- ; let rhs_ty1 = exprType rhs1
- ; join_bndr <- newId (fsLit "$j") (mkPiTypes final_bndrs1 rhs_ty1)
+ ; join_bndr <- newId (fsLit "$j") (mkPiTypes final_bndrs' rhs_ty')
-- Note [Funky mkPiTypes]
; let -- We make the lambdas into one-shot-lambdas. The
-- join point is sure to be applied at most once, and doing so
-- prevents the body of the join point being floated out by
-- the full laziness pass
- really_final_bndrs = map one_shot final_bndrs1
+ really_final_bndrs = map one_shot final_bndrs'
one_shot v | isId v = setOneShotLambda v
| otherwise = v
- join_rhs = mkLams really_final_bndrs rhs2
+ join_rhs = mkLams really_final_bndrs rhs'
join_call = mkApps (Var join_bndr) final_args
- ; env1 <- addPolyBind NotTopLevel env (NonRec join_bndr join_rhs)
- ; return (env1, (con, bndrs1, join_call)) }
+ ; return (addPolyBind NotTopLevel env (NonRec join_bndr join_rhs), (con, bndrs', join_call)) }
-- See Note [Duplicated env]
\end{code}
-Note [Passing the case binder to join points]
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Suppose we have
- case e of cb { C1 -> r1[cb]; C2 x y z -> r2[cb,x] }
-and we want to make join points for the two alternatives,
-which mention the case binder 'cb'. Should we pass 'cb' to
-the join point, or reconstruct it? Here are the two alternatives
-for the C2 alternative:
-
- Plan A(pass cb): j2 cb x = r2[cb,x]
-
- Plan B(reconstruct cb): j2 x y z = let cb = C2 x y z in r2[cb,x]
-
-The advantge of Plan B is that we can "see" the definition of cb
-in r2, and that may be important when we inline stuff in r2. The
-disadvantage is that if this optimisation doesn't happen, we end up
-re-allocating C2, when it already exists. This does happen occasionally;
-an example is the function nofib/spectral/cichelli/Auxil.$whinsert.
-
-Plan B is always better if the constructor is nullary.
-
-In both cases we don't have liveness info for cb on a branch-by-branch
-basis, and it's possible that 'cb' is used in some branches but not
-others. Well, the absence analyser will find that out later, so it's
-not too bad.
-
-Sadly, at the time of writing, neither choice seems an unequivocal
-win. Here are nofib results, for adding -fpass-case-bndr-to-join-points
-(all others are zero effect):
-
- Program Size Allocs Runtime Elapsed
---------------------------------------------------------------------------------
- cichelli +0.0% -4.4% 0.13 0.13
- pic +0.0% -0.7% 0.01 0.04
- transform -0.0% +2.8% -0.4% -9.1%
- wave4main +0.0% +10.5% +3.1% +3.4%
---------------------------------------------------------------------------------
- Min -0.0% -4.4% -7.0% -31.9%
- Max +0.1% +10.5% +3.1% +15.0%
- Geometric Mean +0.0% +0.1% -1.7% -6.1%
-
-
Note [Duplicated env]
~~~~~~~~~~~~~~~~~~~~~
Some of the alternatives are simplified, but have not been turned into a join point
projects / ghc-hetmet.git / blobdiff