2 % (c) The AQUA Project, Glasgow University, 1993-1996
4 \section[SimplVar]{Simplifier stuff related to variables}
7 #include "HsVersions.h"
14 IMPORT_DELOOPER(SmplLoop) ( simplExpr )
16 import Constants ( uNFOLDING_USE_THRESHOLD,
17 uNFOLDING_CON_DISCOUNT_WEIGHT
19 import CmdLineOpts ( switchIsOn, SimplifierSwitch(..) )
21 import CoreUnfold ( Unfolding(..), UfExpr, RdrName, UnfoldingGuidance(..), SimpleUnfolding(..),
23 okToInline, smallEnoughToInline )
24 import BinderInfo ( BinderInfo, noBinderInfo )
26 import CostCentre ( CostCentre, noCostCentreAttached )
27 import Id ( idType, getIdInfo, getIdUnfolding, getIdSpecialisation,
28 idMustBeINLINEd, GenId{-instance Outputable-}
30 import SpecEnv ( SpecEnv, lookupSpecEnv )
31 import IdInfo ( DeforestInfo(..) )
32 import Literal ( isNoRepLit )
33 import MagicUFs ( applyMagicUnfoldingFun, MagicUnfoldingFun )
34 import Outputable ( PprStyle(..) )
35 import PprType ( GenType{-instance Outputable-} )
38 import TyCon ( tyConFamilySize )
39 import Util ( pprTrace, assertPanic, panic )
40 import Maybes ( maybeToBool )
44 %************************************************************************
46 \subsection[Simplify-var]{Completing variables}
48 %************************************************************************
50 This where all the heavy-duty unfolding stuff comes into its own.
53 completeVar env var args result_ty
55 | maybeToBool maybe_magic_result
56 = tick MagicUnfold `thenSmpl_`
60 maybeToBool maybe_unfolding_info &&
61 (not essential_unfoldings_only || idMustBeINLINEd var) &&
63 -- If "essential_unfolds_only" is true we do no inlinings at all,
64 -- EXCEPT for things that absolutely have to be done
65 -- (see comments with idMustBeINLINEd)
67 -- Need to be careful: the RHS of INLINE functions is protected against inlining
68 -- by essential_unfoldings_only being set true; we must not inline workers back into
69 -- wrappers, even though the former have an unfold-always guidance.
70 costCentreOk (getEnclosingCC env) (getEnclosingCC unfold_env)
73 simplCount `thenSmpl` \ n ->
75 pprTrace "Ticks > 1000 and unfolding" (sep [space, int n, ppr PprDebug var])
80 returnSmpl (mkGenApp (Var var) args)
84 tickUnfold var `thenSmpl_`
85 simplExpr unfold_env unf_template args result_ty
87 | maybeToBool maybe_specialisation
88 = tick SpecialisationDone `thenSmpl_`
89 simplExpr (extendTyEnvList env spec_bindings)
91 (map TyArg leftover_ty_args ++ remaining_args)
95 = returnSmpl (mkGenApp (Var var) args)
98 unfolding_from_id = getIdUnfolding var
100 ---------- Magic unfolding stuff
101 maybe_magic_result = case unfolding_from_id of
102 MagicUnfolding _ magic_fn -> applyMagicUnfoldingFun magic_fn
105 (Just magic_result) = maybe_magic_result
107 ---------- Unfolding stuff
109 = case (lookupOutIdEnv env var, unfolding_from_id) of
111 (Just (_, occ_info, OutUnfolding enc_cc unf), _)
112 -> Just (occ_info, setEnclosingCC env enc_cc, unf)
114 (Just (_, occ_info, InUnfolding env_unf unf), _)
115 -> -- pprTrace ("InUnfolding for ") (ppr PprDebug var) $
116 Just (occ_info, env_unf, unf)
118 (_, CoreUnfolding unf)
119 -> -- pprTrace ("CoreUnfolding for ") (ppr PprDebug var) $
120 Just (noBinderInfo, env, unf)
124 Just (occ_info, unfold_env, simple_unfolding) = maybe_unfolding_info
125 SimpleUnfolding form guidance unf_template = simple_unfolding
127 ---------- Specialisation stuff
128 (ty_args, remaining_args) = initialTyArgs args
129 maybe_specialisation = lookupSpecEnv (getIdSpecialisation var) ty_args
130 (Just (spec_template, (spec_bindings, leftover_ty_args))) = maybe_specialisation
134 sw_chkr = getSwitchChecker env
135 essential_unfoldings_only = switchIsOn sw_chkr EssentialUnfoldingsOnly
136 is_case_scrutinee = switchIsOn sw_chkr SimplCaseScrutinee
137 always_inline = case guidance of {UnfoldAlways -> True; other -> False}
139 ok_to_inline = okToInline form occ_info small_enough
140 small_enough = smallEnoughToInline arg_evals is_case_scrutinee guidance
141 arg_evals = [is_evald arg | arg <- args, isValArg arg]
143 is_evald (VarArg v) = isEvaluated (lookupRhsInfo env v)
144 is_evald (LitArg l) = True
149 do_deforest = case (getDeforestInfo (getIdInfo var)) of { DoDeforest -> True; _ -> False }
153 -- costCentreOk checks that it's ok to inline this thing
154 -- The time it *isn't* is this:
156 -- f x = let y = E in
157 -- scc "foo" (...y...)
159 -- Here y has a subsumed cost centre, and we can't inline it inside "foo",
160 -- regardless of whether E is a WHNF or not.
162 costCentreOk cc_encl cc_rhs
163 = noCostCentreAttached cc_encl || not (noCostCentreAttached cc_rhs)