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%
% (c) The GRASP/AQUA Project, Glasgow University, 1993-1995
%
\section[SaLib]{Basic datatypes, functions for the strictness analyser}
See also: the ``library'' for the ``back end'' (@SaBackLib@).
\begin{code}
#include "HsVersions.h"
module SaLib (
AbsVal(..),
AnalysisKind(..),
AbsValEnv{-abstract-}, StrictEnv(..), AbsenceEnv(..),
StrAnalFlags(..), getStrAnalFlags,
nullAbsValEnv, addOneToAbsValEnv, growAbsValEnvList,
lookupAbsValEnv,
absValFromStrictness
-- and to make the interface self-sufficient...
) where
import IdInfo
import Outputable
import Pretty
\end{code}
%************************************************************************
%* *
\subsection[AbsVal-datatype]{@AbsVal@: abstract values (and @AbsValEnv@)}
%* *
%************************************************************************
@AnalysisKind@ tells what kind of analysis is being done.
\begin{code}
data AnalysisKind
= StrAnal -- We're doing strictness analysis
| AbsAnal -- We're doing absence analysis
deriving Text
\end{code}
@AbsVal@ is the data type of HNF abstract values.
\begin{code}
data AbsVal
= AbsTop -- AbsTop is the completely uninformative
-- value
| AbsBot -- An expression whose abstract value is
-- AbsBot is sure to fail to terminate.
-- AbsBot represents the abstract
-- *function* bottom too.
| AbsProd [AbsVal] -- (Lifted) product of abstract values
-- "Lifted" means that AbsBot is *different* from
-- AbsProd [AbsBot, ..., AbsBot]
| AbsFun -- An abstract function, with the given:
[Id] -- arguments
CoreExpr -- body
AbsValEnv -- and environment
| AbsApproxFun -- This is used to represent a coarse
[Demand] -- approximation to a function value. It's an
-- abstract function which is strict in its i'th
-- argument if the i'th element of the Demand
-- list so indicates.
-- The list of arguments is always non-empty.
-- In effect, AbsApproxFun [] = AbsTop
instance Outputable AbsVal where
ppr sty AbsTop = ppStr "AbsTop"
ppr sty AbsBot = ppStr "AbsBot"
ppr sty (AbsProd prod) = ppCat [ppStr "AbsProd", ppr sty prod]
ppr sty (AbsFun args body env)
= ppCat [ppStr "AbsFun{", ppr sty args,
ppStr "???", -- ppStr "}{env:", ppr sty (keysFM env `zip` eltsFM env),
ppStr "}" ]
ppr sty (AbsApproxFun demands)
= ppCat [ppStr "AbsApprox{", ppr sty demands, ppStr "}" ]
\end{code}
%-----------
An @AbsValEnv@ maps @Ids@ to @AbsVals@. Any unbound @Ids@ are
implicitly bound to @AbsTop@, the completely uninformative,
pessimistic value---see @absEval@ of a @Var@.
\begin{code}
data AbsValEnv = AbsValEnv StrAnalFlags (IdEnv AbsVal)
type StrAnalFlags
= (Bool, -- True <=> AllStrict flag is set
Bool) -- True <=> NumbersStrict flag is set
type StrictEnv = AbsValEnv -- Environment for strictness analysis
type AbsenceEnv = AbsValEnv -- Environment for absence analysis
nullAbsValEnv flags -- this is the one and only way to create AbsValEnvs
= AbsValEnv flags nullIdEnv
addOneToAbsValEnv (AbsValEnv x idenv) y z = AbsValEnv x (addOneToIdEnv idenv y z)
growAbsValEnvList (AbsValEnv x idenv) ys = AbsValEnv x (growIdEnvList idenv ys)
lookupAbsValEnv (AbsValEnv _ idenv) y
= lookupIdEnv idenv y
getStrAnalFlags (AbsValEnv flags _) = flags
\end{code}
\begin{code}
absValFromStrictness :: AnalysisKind -> StrictnessInfo -> AbsVal
absValFromStrictness anal NoStrictnessInfo = AbsTop
absValFromStrictness StrAnal BottomGuaranteed = AbsBot -- Guaranteed bottom
absValFromStrictness AbsAnal BottomGuaranteed = AbsTop -- Check for poison in
-- arguments (if any)
absValFromStrictness anal (StrictnessInfo [] _) = AbsTop
absValFromStrictness anal (StrictnessInfo args_info _) = AbsApproxFun args_info
\end{code}
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