-%
+`%
% (c) The AQUA Project, Glasgow University, 1994-1996
%
\section[SimplCase]{Simplification of `case' expression}
module SimplCase ( simplCase, bindLargeRhs ) where
IMP_Ubiq(){-uitous-}
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
IMPORT_DELOOPER(SmplLoop) ( simplBind, simplExpr, MagicUnfoldingFun )
+#else
+import {-# SOURCE #-} Simplify ( simplBind, simplExpr )
+--import {-# SOURCE #-} MagicUFs ( MagicUnfoldingFun )
+#endif
import BinderInfo -- too boring to try to select things...
import CmdLineOpts ( SimplifierSwitch(..) )
import CoreSyn
-import CoreUnfold ( whnfDetails, mkConForm, mkLitForm,
- UnfoldingDetails(..), UnfoldingGuidance(..),
- FormSummary(..)
- )
+import CoreUnfold ( Unfolding, SimpleUnfolding )
import CoreUtils ( coreAltsType, nonErrorRHSs, maybeErrorApp,
- unTagBindersAlts
+ unTagBindersAlts, unTagBinders, coreExprType
)
-import Id ( idType, isDataCon, getIdDemandInfo,
- SYN_IE(DataCon), GenId{-instance Eq-}
+import Id ( idType, isDataCon, getIdDemandInfo, dataConArgTys,
+ SYN_IE(DataCon), GenId{-instance Eq-},
+ SYN_IE(Id)
)
import IdInfo ( willBeDemanded, DemandInfo )
import Literal ( isNoRepLit, Literal{-instance Eq-} )
import PrimOp ( primOpOkForSpeculation, PrimOp{-instance Eq-} )
import SimplEnv
import SimplMonad
-import SimplUtils ( mkValLamTryingEta )
-import Type ( isPrimType, maybeAppDataTyConExpandingDicts, mkFunTy, mkFunTys, eqTy )
+import Type ( isPrimType, maybeAppDataTyConExpandingDicts, getAppDataTyConExpandingDicts, mkFunTy, mkFunTys, eqTy )
+import TyCon ( isDataTyCon )
import TysPrim ( voidTy )
import Unique ( Unique{-instance Eq-} )
import Usage ( GenUsage{-instance Eq-} )
-import Util ( isIn, isSingleton, zipEqual, panic, assertPanic )
+import Util ( SYN_IE(Eager), runEager, appEager,
+ isIn, isSingleton, zipEqual, panic, assertPanic )
\end{code}
Float let out of case.
-> InExpr -- Scrutinee
-> InAlts -- Alternatives
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Rhs handler
- -> OutType -- Type of result expression
+ -> OutType -- Type of result expression
-> SmplM OutExpr
simplCase env (Let bind body) alts rhs_c result_ty
else
bindLargeAlts env outer_alts rhs_c result_ty `thenSmpl` \ (extra_bindings, outer_alts') ->
let
- rhs_c' = \env rhs -> simplExpr env rhs []
+ rhs_c' = \env rhs -> simplExpr env rhs [] result_ty
in
simplCase env inner_scrut inner_alts
(\env rhs -> simplCase env rhs outer_alts' rhs_c' result_ty)
| maybeToBool maybe_error_app
= -- Look for an application of an error id
tick CaseOfError `thenSmpl_`
- rhs_c env retyped_error_app
+ simplExpr env retyped_error_app [] result_ty
+ -- Ignore rhs_c!
+ -- We must apply simplExpr because "rhs" isn't yet simplified.
+ -- The ice is a little thin because body_ty is an OutType; but it's ok really
where
- alts_ty = coreAltsType (unTagBindersAlts alts)
- maybe_error_app = maybeErrorApp scrut (Just alts_ty)
+ maybe_error_app = maybeErrorApp scrut (Just result_ty)
Just retyped_error_app = maybe_error_app
\end{code}
\begin{code}
simplCase env other_scrut alts rhs_c result_ty
- = -- Float the let outside the case scrutinee
- simplExpr env other_scrut [] `thenSmpl` \ scrut' ->
+ = simplTy env scrut_ty `appEager` \ scrut_ty' ->
+ simplExpr env' other_scrut [] scrut_ty `thenSmpl` \ scrut' ->
completeCase env scrut' alts rhs_c
+ where
+ -- When simplifying the scrutinee of a complete case that
+ -- has no default alternative
+ env' = case alts of
+ AlgAlts _ NoDefault -> setCaseScrutinee env
+ PrimAlts _ NoDefault -> setCaseScrutinee env
+ other -> env
+
+ scrut_ty = coreExprType (unTagBinders other_scrut)
\end{code}
-- 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)]
-- 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 = whnfDetails scrut_form
+ scrut_is_evald = isEvaluated scrut_form
scrut_is_eliminable_primitive
= case scrut of
-- the scrutinee. Remember that the rhs is as yet unsimplified.
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
+ -> case (runEager $ lookupId env rhs_var) of
+ 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}
App (Var prim_rhs_fun_id) (VarArg voidId))
| otherwise
- = -- Make the new binding Id. NB: it's an OutId
- newId rhs_fun_ty `thenSmpl` \ rhs_fun_id ->
-
- -- Generate its rhs
+ = -- Generate the rhs
cloneIds env used_args `thenSmpl` \ used_args' ->
let
new_env = extendIdEnvWithClones env used_args used_args'
+ rhs_fun_ty :: OutType
+ rhs_fun_ty = mkFunTys (map idType used_args') rhs_ty
in
+
+ -- Make the new binding Id. NB: it's an OutId
+ newId rhs_fun_ty `thenSmpl` \ rhs_fun_id ->
rhs_c new_env `thenSmpl` \ rhs' ->
let
- final_rhs
- = (if switchIsSet new_env SimplDoEtaReduction
- then mkValLamTryingEta
- else mkValLam) used_args' rhs'
+ final_rhs = mkValLam used_args' rhs'
in
returnSmpl (NonRec rhs_fun_id final_rhs,
foldl App (Var rhs_fun_id) used_arg_atoms)
-- it's processed the OutId won't be found in the environment, so it
-- will be left unmodified.
where
- 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]
-> InAlts
-> (SimplEnv -> InExpr -> SmplM OutExpr) -- Rhs handler
-> SmplM OutAlts
+-- For single-constructor types
+-- case e of y -> b ===> case e of (a,b) -> let y = (a,b) in b
+
+simplAlts env scrut (AlgAlts [] (BindDefault bndr@(id,occ_info) rhs)) rhs_c
+ | maybeToBool maybe_data_ty &&
+ not (null cons) && -- Not an abstract type (can arise if we're pruning tydecl imports)
+ null other_cons
+ = ASSERT( isDataTyCon tycon )
+ newIds inst_con_arg_tys `thenSmpl` \ new_bindees ->
+ let
+ new_args = [ (b, bad_occ_info) | b <- new_bindees ]
+ con_app = mkCon con [] ty_args (map VarArg new_bindees)
+ new_rhs = Let (NonRec bndr con_app) rhs
+ in
+ simplAlts env scrut (AlgAlts [(con,new_args,new_rhs)] NoDefault) rhs_c
+ where
+ maybe_data_ty = maybeAppDataTyConExpandingDicts (idType id)
+ Just (tycon, ty_args, cons) = maybe_data_ty
+ (con:other_cons) = cons
+ inst_con_arg_tys = dataConArgTys con ty_args
+ bad_occ_info = ManyOcc 0 -- Non-committal!
simplAlts env scrut (AlgAlts alts deflt) rhs_c
= mapSmpl do_alt alts `thenSmpl` \ alts' ->
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 v -> extendUnfoldEnvGivenConstructor env1 v con con_args'
+ Var v -> extendEnvGivenNewRhs env1 v (Con con args)
+ where
+ (_, ty_args, _) = getAppDataTyConExpandingDicts (idType v)
+ args = map TyArg ty_args ++ map VarArg con_args'
+
other -> env1
in
rhs_c new_env rhs `thenSmpl` \ 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 v -> extendUnfoldEnvGivenFormDetails env v (mkLitForm lit)
+ Var v -> extendEnvGivenNewRhs env v (Lit lit)
other -> env
in
rhs_c new_env rhs `thenSmpl` \ 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)
- other -> form_from_this_case
-
- env2 = extendUnfoldEnvGivenFormDetails env1 binder' final_form
-
- -- Change unfold details for scrut var. We now want to unfold it
- -- to binder'
- new_scrut_var_form = GenForm 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 = 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')
| alt_con == con
= -- Matching alternative!
let
- new_env = extendIdEnvWithAtomList env (zipEqual "SimplCase" alt_args (filter isValArg 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 = extendUnfoldEnvGivenFormDetails env1 id'
- (mkConForm con 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 con_args)) rhs')
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\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)
v | scrut_is_var = Var scrut_var
| otherwise = Con con (map TyArg arg_tys ++ map VarArg args)
- arg_tys = case (maybeAppDataTyConExpandingDicts (idType deflt_var)) of
- Just (_, arg_tys, _) -> arg_tys
+ arg_tys = 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
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
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