2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[SaLib]{Basic datatypes, functions for the strictness analyser}
6 See also: the ``library'' for the ``back end'' (@SaBackLib@).
12 AbsValEnv{-abstract-}, StrictEnv, AbsenceEnv,
14 nullAbsValEnv, addOneToAbsValEnv, growAbsValEnvList,
19 #include "HsVersions.h"
23 import CoreSyn ( CoreExpr )
25 import IdInfo ( StrictnessInfo(..) )
26 import Demand ( Demand, pprDemands )
30 %************************************************************************
32 \subsection[AbsVal-datatype]{@AbsVal@: abstract values (and @AbsValEnv@)}
34 %************************************************************************
36 @AnalysisKind@ tells what kind of analysis is being done.
40 = StrAnal -- We're doing strictness analysis
41 | AbsAnal -- We're doing absence analysis
45 @AbsVal@ is the data type of HNF abstract values.
49 = AbsTop -- AbsTop is the completely uninformative
52 | AbsBot -- An expression whose abstract value is
53 -- AbsBot is sure to fail to terminate.
54 -- AbsBot represents the abstract
55 -- *function* bottom too.
57 | AbsProd [AbsVal] -- (Lifted) product of abstract values
58 -- "Lifted" means that AbsBot is *different* from
59 -- AbsProd [AbsBot, ..., AbsBot]
61 | AbsFun -- An abstract function, with the given:
62 Type -- Type of the *argument* to the function
63 (AbsVal -> AbsVal) -- The function
65 | AbsApproxFun -- This is used to represent a coarse
66 [Demand] -- approximation to a function value. It's an
67 AbsVal -- abstract function which is strict in its
68 -- arguments if the Demand so indicates.
69 -- INVARIANT: the [Demand] is non-empty
71 -- AbsApproxFun has to take a *list* of demands, no just one,
72 -- because function spaces are now lifted. Hence, (f bot top)
73 -- might be bot, but the partial application (f bot) is a *function*,
76 mkAbsApproxFun :: Demand -> AbsVal -> AbsVal
77 mkAbsApproxFun d (AbsApproxFun ds val) = AbsApproxFun (d:ds) val
78 mkAbsApproxFun d val = AbsApproxFun [d] val
80 instance Outputable AbsVal where
81 ppr AbsTop = ptext SLIT("AbsTop")
82 ppr AbsBot = ptext SLIT("AbsBot")
83 ppr (AbsProd prod) = hsep [ptext SLIT("AbsProd"), ppr prod]
84 ppr (AbsFun bndr_ty body) = ptext SLIT("AbsFun")
85 ppr (AbsApproxFun demands val)
86 = ptext SLIT("AbsApprox") <+> brackets (interpp'SP demands) <+> ppr val
91 An @AbsValEnv@ maps @Ids@ to @AbsVals@. Any unbound @Ids@ are
92 implicitly bound to @AbsTop@, the completely uninformative,
93 pessimistic value---see @absEval@ of a @Var@.
96 newtype AbsValEnv = AbsValEnv (IdEnv AbsVal)
98 type StrictEnv = AbsValEnv -- Environment for strictness analysis
99 type AbsenceEnv = AbsValEnv -- Environment for absence analysis
101 nullAbsValEnv -- this is the one and only way to create AbsValEnvs
102 = AbsValEnv emptyVarEnv
104 addOneToAbsValEnv (AbsValEnv idenv) y z = AbsValEnv (extendVarEnv idenv y z)
105 growAbsValEnvList (AbsValEnv idenv) ys = AbsValEnv (extendVarEnvList idenv ys)
107 lookupAbsValEnv (AbsValEnv idenv) y
108 = lookupVarEnv idenv y
112 absValFromStrictness :: AnalysisKind -> StrictnessInfo -> AbsVal
114 absValFromStrictness anal NoStrictnessInfo = AbsTop
115 absValFromStrictness anal (StrictnessInfo args_info bot_result)
116 = case args_info of -- Check the invariant that the arg list on
117 [] -> res -- AbsApproxFun is non-empty
118 _ -> AbsApproxFun args_info res
120 res | not bot_result = AbsTop
121 | otherwise = case anal of