%
-% (c) The AQUA Project, Glasgow University, 1994-1995
+% (c) The AQUA Project, Glasgow University, 1994-1996
%
\section[SimplCase]{Simplification of `case' expression}
module SimplCase ( simplCase, bindLargeRhs ) where
-import SimplMonad
-import SimplEnv
+IMP_Ubiq(){-uitous-}
+IMPORT_DELOOPER(SmplLoop) ( simplBind, simplExpr, MagicUnfoldingFun )
-import PrelInfo ( getPrimOpResultInfo, PrimOpResultInfo(..), PrimOp,
- voidPrimTy, voidPrimId, mkFunTy, primOpOkForSpeculation
- IF_ATTACK_PRAGMAS(COMMA tagOf_PrimOp)
- IF_ATTACK_PRAGMAS(COMMA pprPrimOp)
+import BinderInfo -- too boring to try to select things...
+import CmdLineOpts ( SimplifierSwitch(..) )
+import CoreSyn
+import CoreUnfold ( Unfolding(..), UnfoldingGuidance(..),
+ SimpleUnfolding, FormSummary
)
-import Type ( splitSigmaTy, splitTyArgs, glueTyArgs,
- getTyConFamilySize, isPrimType,
- maybeDataTyCon
+import CoreUtils ( coreAltsType, nonErrorRHSs, maybeErrorApp,
+ unTagBindersAlts
)
-import Literal ( isNoRepLit, Literal )
-import CmdLineOpts ( SimplifierSwitch(..) )
-import Id
-import IdInfo
-import Maybes ( catMaybes, maybeToBool, Maybe(..) )
-import Simplify
-import SimplUtils
-import SimplVar ( completeVar )
-import Util
+import Id ( idType, isDataCon, getIdDemandInfo,
+ SYN_IE(DataCon), GenId{-instance Eq-}
+ )
+import IdInfo ( willBeDemanded, DemandInfo )
+import Literal ( isNoRepLit, Literal{-instance Eq-} )
+import Maybes ( maybeToBool )
+import PrelVals ( voidId )
+import PrimOp ( primOpOkForSpeculation, PrimOp{-instance Eq-} )
+import SimplEnv
+import SimplMonad
+import SimplUtils ( mkValLamTryingEta )
+import Type ( isPrimType, getAppDataTyConExpandingDicts, mkFunTy, mkFunTys, eqTy )
+import TysPrim ( voidTy )
+import Unique ( Unique{-instance Eq-} )
+import Usage ( GenUsage{-instance Eq-} )
+import Util ( isIn, isSingleton, zipEqual, panic, assertPanic )
\end{code}
-
-
-
-
Float let out of case.
\begin{code}
-> InExpr -- Scrutinee
-> InAlts -- Alternatives
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Rhs handler
- -> OutUniType -- Type of result expression
+ -> OutType -- Type of result expression
-> SmplM OutExpr
simplCase env (Let bind body) alts rhs_c result_ty
tick KnownBranch `thenSmpl_`
completePrimCaseWithKnownLit env lit alts rhs_c
-completeCase env expr@(Con con tys con_args) alts rhs_c
+completeCase env expr@(Con con con_args) alts rhs_c
= -- Ha! Staring us in the face -- select the appropriate alternative
tick KnownBranch `thenSmpl_`
- completeAlgCaseWithKnownCon env con tys con_args alts rhs_c
+ completeAlgCaseWithKnownCon env con con_args alts rhs_c
\end{code}
Case elimination
-- Eliminate unused rhss if poss
rhss = case scrut_form of
- OtherLitForm not_these -> [rhs | (alt_lit,rhs) <- alts,
- not (alt_lit `is_elem` not_these)
- ]
+ OtherLit not_these -> [rhs | (alt_lit,rhs) <- alts,
+ not (alt_lit `is_elem` not_these)
+ ]
other -> [rhs | (_,rhs) <- alts]
AlgAlts alts deflt -> (deflt_binder_unused && all alt_binders_unused possible_alts,
-- Eliminate unused alts if poss
possible_alts = case scrut_form of
- OtherConForm not_these ->
+ OtherCon not_these ->
-- Remove alts which can't match
[alt | alt@(alt_con,_,_) <- alts,
not (alt_con `is_elem` not_these)]
-#ifdef DEBUG
--- ConForm c t v -> pprPanic "completeCase!" (ppAbove (ppCat [ppr PprDebug c, ppr PprDebug t, ppr PprDebug v]) (ppr PprDebug alts))
- -- ConForm can't happen, since we'd have
- -- inlined it, and be in completeCaseWithKnownCon by now
-#endif
other -> alts
alt_binders_unused (con, args, rhs) = all is_dead args
-- If the scrutinee is a variable, look it up to see what we know about it
scrut_form = case scrut of
- Var v -> lookupUnfolding env v
- other -> NoUnfoldingDetails
+ Var v -> lookupRhsInfo env v
+ other -> NoRhsInfo
-- If the scrut is already eval'd then there's no worry about
-- eliminating the case
- scrut_is_evald = case scrut_form of
- OtherLitForm _ -> True
- ConForm _ _ _ -> True
- OtherConForm _ -> True
- other -> False
-
+ scrut_is_evald = isEvaluated scrut_form
scrut_is_eliminable_primitive
= case scrut of
- Prim op _ _ -> primOpOkForSpeculation op
- Var _ -> case alts of
- PrimAlts _ _ -> True -- Primitive, hence non-bottom
- AlgAlts _ _ -> False -- Not primitive
- other -> False
+ Prim op _ -> primOpOkForSpeculation op
+ Var _ -> case alts of
+ PrimAlts _ _ -> True -- Primitive, hence non-bottom
+ AlgAlts _ _ -> False -- Not primitive
+ other -> False
-- case v of w -> e{strict in w} ===> e[v/w]
scrut_is_var_and_single_strict_default
rhs1_is_scrutinee = case (scrut, rhs1) of
(Var scrut_var, Var rhs_var)
-> case lookupId env rhs_var of
- Just (ItsAnAtom (VarArg rhs_var'))
- -> rhs_var' == scrut_var
- other -> False
+ VarArg rhs_var' -> rhs_var' == scrut_var
+ other -> False
other -> False
is_elem x ys = isIn "completeCase" x ys
\begin{code}
completeCase env scrut alts rhs_c
= simplAlts env scrut alts rhs_c `thenSmpl` \ alts' ->
- mkCoCase scrut alts'
+ mkCoCase env scrut alts'
\end{code}
bindLargeAlts :: SimplEnv
-> InAlts
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Old rhs handler
- -> OutUniType -- Result type
+ -> OutType -- Result type
-> SmplM ([OutBinding], -- Extra bindings
InAlts) -- Modified alts
\begin{code}
bindLargeRhs :: SimplEnv
-> [InBinder] -- The args wrt which the rhs should be abstracted
- -> OutUniType
+ -> OutType
-> (SimplEnv -> SmplM OutExpr) -- Rhs handler
-> SmplM (OutBinding, -- New bindings (singleton or empty)
InExpr) -- Modified rhs
-- for let-binding-purposes, we will *caseify* it (!),
-- with potentially-disastrous strictness results. So
-- instead we turn it into a function: \v -> e
- -- where v::VoidPrim. Since arguments of type
+ -- where v::Void. Since arguments of type
-- VoidPrim don't generate any code, this gives the
-- desired effect.
--
-- The general structure is just the same as for the common "otherwise~ case
= newId prim_rhs_fun_ty `thenSmpl` \ prim_rhs_fun_id ->
- newId voidPrimTy `thenSmpl` \ void_arg_id ->
+ newId voidTy `thenSmpl` \ void_arg_id ->
rhs_c env `thenSmpl` \ prim_new_body ->
returnSmpl (NonRec prim_rhs_fun_id (mkValLam [void_arg_id] prim_new_body),
- App (Var prim_rhs_fun_id) (VarArg voidPrimId))
+ App (Var prim_rhs_fun_id) (VarArg voidId))
| otherwise
= -- Make the new binding Id. NB: it's an OutId
let
final_rhs
= (if switchIsSet new_env SimplDoEtaReduction
- then mkCoLamTryingEta
+ then mkValLamTryingEta
else mkValLam) used_args' rhs'
in
returnSmpl (NonRec rhs_fun_id final_rhs,
-- it's processed the OutId won't be found in the environment, so it
-- will be left unmodified.
where
- rhs_fun_ty :: OutUniType
- rhs_fun_ty = glueTyArgs [simplTy env (idType id) | (id,_) <- used_args] rhs_ty
+ rhs_fun_ty :: OutType
+ rhs_fun_ty = mkFunTys [simplTy env (idType id) | (id,_) <- used_args] rhs_ty
used_args = [arg | arg@(_,usage) <- args, not (dead usage)]
used_arg_atoms = [VarArg arg_id | (arg_id,_) <- used_args]
dead DeadCode = True
dead other = False
- prim_rhs_fun_ty = mkFunTy voidPrimTy rhs_ty
+ prim_rhs_fun_ty = mkFunTy voidTy rhs_ty
\end{code}
Case alternatives when we don't know the scrutinee
simplDefault env scrut deflt deflt_form rhs_c `thenSmpl` \ deflt' ->
returnSmpl (AlgAlts alts' deflt')
where
- deflt_form = OtherConForm [con | (con,_,_) <- alts]
+ deflt_form = OtherCon [con | (con,_,_) <- alts]
do_alt (con, con_args, rhs)
= cloneIds env con_args `thenSmpl` \ con_args' ->
let
env1 = extendIdEnvWithClones env con_args con_args'
new_env = case scrut of
- Var var -> _scc_ "euegC1" (extendUnfoldEnvGivenConstructor env1 var con con_args')
- other -> env1
+ Var v -> extendEnvGivenNewRhs env1 v (Con con args)
+ where
+ (_, ty_args, _) = --trace "SimplCase.getAppData..." $
+ getAppDataTyConExpandingDicts (idType v)
+ args = map TyArg ty_args ++ map VarArg con_args'
+
+ other -> env1
in
rhs_c new_env rhs `thenSmpl` \ rhs' ->
returnSmpl (con, con_args', rhs')
simplDefault env scrut deflt deflt_form rhs_c `thenSmpl` \ deflt' ->
returnSmpl (PrimAlts alts' deflt')
where
- deflt_form = OtherLitForm [lit | (lit,_) <- alts]
+ deflt_form = OtherLit [lit | (lit,_) <- alts]
do_alt (lit, rhs)
= let
new_env = case scrut of
- Var var -> _scc_ "euegFD1" (extendUnfoldEnvGivenFormDetails env var (LitForm lit))
- other -> env
+ Var v -> extendEnvGivenNewRhs env v (Lit lit)
+ other -> env
in
rhs_c new_env rhs `thenSmpl` \ rhs' ->
returnSmpl (lit, rhs')
:: SimplEnv
-> OutExpr -- Simplified scrutinee
-> InDefault -- Default alternative to be completed
- -> UnfoldingDetails -- Gives form of scrutinee
+ -> RhsInfo -- Gives form of scrutinee
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Old rhs handler
-> SmplM OutDefault
= returnSmpl NoDefault
-- Special case for variable scrutinee; see notes above.
-simplDefault env (Var scrut_var) (BindDefault binder rhs) form_from_this_case rhs_c
+simplDefault env (Var scrut_var) (BindDefault binder@(_,occ_info) rhs)
+ info_from_this_case rhs_c
= cloneId env binder `thenSmpl` \ binder' ->
let
- env1 = extendIdEnvWithAtom env binder (VarArg binder')
+ env1 = extendIdEnvWithClone env binder binder'
+ env2 = extendEnvGivenRhsInfo env1 binder' occ_info info_from_this_case
-- Add form details for the default binder
- scrut_form = lookupUnfolding env scrut_var
- final_form
- = case (form_from_this_case, scrut_form) of
- (OtherConForm cs, OtherConForm ds) -> OtherConForm (cs++ds)
- (OtherLitForm cs, OtherLitForm ds) -> OtherLitForm (cs++ds)
- -- ConForm, LitForm impossible
- -- (ASSERT? ASSERT? Hello? WDP 95/05)
- other -> form_from_this_case
-
- env2 = _scc_ "euegFD2" (extendUnfoldEnvGivenFormDetails env1 binder' final_form)
-
- -- Change unfold details for scrut var. We now want to unfold it
- -- to binder'
- new_scrut_var_form = GenForm True {- OK to dup -} WhnfForm
- (Var binder') UnfoldAlways
- new_env = extendUnfoldEnvGivenFormDetails env2 scrut_var new_scrut_var_form
-
+ scrut_info = lookupRhsInfo env scrut_var
+ env3 = extendEnvGivenRhsInfo env2 binder' occ_info scrut_info
+ new_env = extendEnvGivenNewRhs env3 scrut_var (Var binder')
in
rhs_c new_env rhs `thenSmpl` \ rhs' ->
returnSmpl (BindDefault binder' rhs')
-simplDefault env scrut (BindDefault binder rhs) form rhs_c
+simplDefault env scrut (BindDefault binder@(_,occ_info) rhs)
+ info_from_this_case rhs_c
= cloneId env binder `thenSmpl` \ binder' ->
let
- env1 = extendIdEnvWithAtom env binder (VarArg binder')
- new_env = _scc_ "euegFD2" (extendUnfoldEnvGivenFormDetails env1 binder' form)
+ env1 = extendIdEnvWithClone env binder binder'
+ new_env = extendEnvGivenRhsInfo env1 binder' occ_info info_from_this_case
in
rhs_c new_env rhs `thenSmpl` \ rhs' ->
returnSmpl (BindDefault binder' rhs')
\begin{code}
completeAlgCaseWithKnownCon
:: SimplEnv
- -> DataCon -> [Type] -> [InAtom]
+ -> DataCon -> [InArg]
-- Scrutinee is (con, type, value arguments)
-> InAlts
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Rhs handler
-> SmplM OutExpr
-completeAlgCaseWithKnownCon env con tys con_args (AlgAlts alts deflt) rhs_c
+completeAlgCaseWithKnownCon env con con_args (AlgAlts alts deflt) rhs_c
= ASSERT(isDataCon con)
search_alts alts
where
| alt_con == con
= -- Matching alternative!
let
- new_env = extendIdEnvWithAtomList env (zip alt_args con_args)
+ new_env = extendIdEnvWithAtoms env
+ (zipEqual "SimplCase" alt_args (filter isValArg con_args))
in
rhs_c new_env rhs
NoDefault -> -- Blargh!
panic "completeAlgCaseWithKnownCon: No matching alternative and no default"
- BindDefault binder rhs -> -- OK, there's a default case
+ BindDefault binder@(_,occ_info) rhs -> -- OK, there's a default case
-- let-bind the binder to the constructor
cloneId env binder `thenSmpl` \ id' ->
let
env1 = extendIdEnvWithClone env binder id'
- new_env = _scc_ "euegFD3" (extendUnfoldEnvGivenFormDetails env1 id'
- (ConForm con tys con_args))
+ new_env = extendEnvGivenBinding env1 occ_info id' (Con con con_args)
in
rhs_c new_env rhs `thenSmpl` \ rhs' ->
- returnSmpl (Let (NonRec id' (Con con tys con_args)) rhs')
+ returnSmpl (Let (NonRec id' (Con con con_args)) rhs')
\end{code}
Case absorption and identity-case elimination
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-mkCoCase :: OutExpr -> OutAlts -> SmplM OutExpr
+mkCoCase :: SimplEnv -> OutExpr -> OutAlts -> SmplM OutExpr
\end{code}
@mkCoCase@ tries the following transformation (if possible):
equation for AlgAlts, one for PrimAlts):
\begin{code}
-mkCoCase scrut (AlgAlts outer_alts
+mkCoCase env scrut (AlgAlts outer_alts
(BindDefault deflt_var
(Case (Var scrut_var')
(AlgAlts inner_alts inner_deflt))))
- | (scrut_is_var && scrut_var == scrut_var') -- First transformation
- || deflt_var == scrut_var' -- Second transformation
+ | switchIsSet env SimplCaseMerge &&
+ ((scrut_is_var && scrut_var == scrut_var') || -- First transformation
+ deflt_var == scrut_var') -- Second transformation
= -- Aha! The default-absorption rule applies
tick CaseMerge `thenSmpl_`
returnSmpl (Case scrut (AlgAlts (outer_alts ++ munged_reduced_inner_alts)
munge_alt (con, args, rhs) = (con, args, Let (NonRec deflt_var v) rhs)
where
v | scrut_is_var = Var scrut_var
- | otherwise = Con con arg_tys (map VarArg args)
+ | otherwise = Con con (map TyArg arg_tys ++ map VarArg args)
- arg_tys = case maybeDataTyCon (idType deflt_var) of
- Just (_, arg_tys, _) -> arg_tys
+ arg_tys = --trace "SimplCase:getAppData...:2" $
+ case (getAppDataTyConExpandingDicts (idType deflt_var)) of
+ (_, arg_tys, _) -> arg_tys
-mkCoCase scrut (PrimAlts
+mkCoCase env scrut (PrimAlts
outer_alts
(BindDefault deflt_var (Case
(Var scrut_var')
(PrimAlts inner_alts inner_deflt))))
- | (scrut_is_var && scrut_var == scrut_var') ||
- deflt_var == scrut_var'
+ | switchIsSet env SimplCaseMerge &&
+ ((scrut_is_var && scrut_var == scrut_var') ||
+ deflt_var == scrut_var')
= -- Aha! The default-absorption rule applies
tick CaseMerge `thenSmpl_`
returnSmpl (Case scrut (PrimAlts (outer_alts ++ munged_reduced_inner_alts)
and similar friends.
\begin{code}
-mkCoCase scrut alts
+mkCoCase env scrut alts
| identity_alts alts
= tick CaseIdentity `thenSmpl_`
returnSmpl scrut
identity_alts (AlgAlts alts deflt) = all identity_alg_alt alts && identity_deflt deflt
identity_alts (PrimAlts alts deflt) = all identity_prim_alt alts && identity_deflt deflt
- identity_alg_alt (con, args, Con con' _ args')
+ identity_alg_alt (con, args, Con con' args')
= con == con'
&& and (zipWith eq_arg args args')
&& length args == length args'
The catch-all case
\begin{code}
-mkCoCase other_scrut other_alts = returnSmpl (Case other_scrut other_alts)
+mkCoCase env other_scrut other_alts = returnSmpl (Case other_scrut other_alts)
\end{code}
Boring local functions used above. They simply introduce a trivial binding
\end{code}
\begin{code}
- -- A cheap equality test which bales out fast!
cheap_eq :: InExpr -> InExpr -> Bool
+ -- A cheap equality test which bales out fast!
+
cheap_eq (Var v1) (Var v2) = v1==v2
cheap_eq (Lit l1) (Lit l2) = l1==l2
-cheap_eq (Con con1 tys1 args1) (Con con2 tys2 args2) = (con1==con2) &&
- (args1 `eq_args` args2)
- -- Types bound to be equal
-cheap_eq (Prim op1 tys1 args1) (Prim op2 tys2 args2) = (op1==op2) &&
- (args1 `eq_args` args2)
- -- Types bound to be equal
-cheap_eq (App f1 a1) (App f2 a2) = (f1 `cheap_eq` f2) && (a1 `eq_atom` a2)
-cheap_eq (CoTyApp f1 t1) (CoTyApp f2 t2) = (f1 `cheap_eq` f2) && (t1 == t2)
+cheap_eq (Con con1 args1) (Con con2 args2)
+ = con1 == con2 && args1 `eq_args` args2
+
+cheap_eq (Prim op1 args1) (Prim op2 args2)
+ = op1 ==op2 && args1 `eq_args` args2
+
+cheap_eq (App f1 a1) (App f2 a2)
+ = f1 `cheap_eq` f2 && a1 `eq_arg` a2
+
cheap_eq _ _ = False
-- ToDo: make CoreArg an instance of Eq
-eq_args (arg1: args1) (arg2 : args2) = (arg1 `eq_atom` arg2) && (args1 `eq_args` args2)
-eq_args [] [] = True
-eq_args other1 other2 = False
-
-eq_atom (LitArg l1) (LitArg l2) = l1==l2
-eq_atom (VarArg v1) (VarArg v2) = v1==v2
-eq_atom other1 other2 = False
+eq_args (a1:as1) (a2:as2) = a1 `eq_arg` a2 && as1 `eq_args` as2
+eq_args [] [] = True
+eq_args _ _ = False
+
+eq_arg (LitArg l1) (LitArg l2) = l1 == l2
+eq_arg (VarArg v1) (VarArg v2) = v1 == v2
+eq_arg (TyArg t1) (TyArg t2) = t1 `eqTy` t2
+eq_arg (UsageArg u1) (UsageArg u2) = u1 == u2
+eq_arg _ _ = False
\end{code}
projects / ghc-hetmet.git / blobdiff