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|
----------------------------------------------------------------------
-- |
-- Module : BackOpt
-- Maintainer : AR
-- Stability : (stable)
-- Portability : (portable)
--
-- > CVS $Date: 2005/04/21 16:21:33 $
-- > CVS $Author: bringert $
-- > CVS $Revision: 1.6 $
--
-- Optimizations on GF source code: sharing, parametrization, value sets.
--
-- optimization: sharing branches in tables. AR 25\/4\/2003.
-- following advice of Josef Svenningsson
-----------------------------------------------------------------------------
module GF.Compile.BackOpt (shareModule, OptSpec) where
import GF.Grammar.Grammar
import GF.Infra.Ident
import GF.Infra.Option
import qualified GF.Grammar.Macros as C
import GF.Grammar.PrGrammar (prt)
import GF.Data.Operations
import Data.List
import qualified GF.Infra.Modules as M
import qualified Data.ByteString.Char8 as BS
import Data.Set (Set)
import qualified Data.Set as Set
type OptSpec = Set Optimization
shareModule :: OptSpec -> SourceModule -> SourceModule
shareModule opt (i,mo) = (i,M.replaceJudgements mo (mapTree (shareInfo opt) (M.jments mo)))
shareInfo :: OptSpec -> (Ident, Info) -> Info
shareInfo opt (c, CncCat ty (Just t) m) = CncCat ty (Just (shareOptim opt c t)) m
shareInfo opt (c, CncFun kxs (Just t) m) = CncFun kxs (Just (shareOptim opt c t)) m
shareInfo opt (c, ResOper ty (Just t)) = ResOper ty (Just (shareOptim opt c t))
shareInfo _ (_,i) = i
-- the function putting together optimizations
shareOptim :: OptSpec -> Ident -> Term -> Term
shareOptim opt c = (if OptValues `Set.member` opt then values else id)
. (if OptParametrize `Set.member` opt then factor c 0 else id)
-- do even more: factor parametric branches
factor :: Ident -> Int -> Term -> Term
factor c i t = case t of
T _ [_] -> t
T _ [] -> t
T (TComp ty) cs ->
T (TTyped ty) $ factors i [(p, factor c (i+1) v) | (p, v) <- cs]
_ -> C.composSafeOp (factor c i) t
where
factors i psvs = -- we know psvs has at least 2 elements
let p = qqIdent c i
vs' = map (mkFun p) psvs
in if allEqs vs'
then mkCase p vs'
else psvs
mkFun p (patt, val) = replace (C.patt2term patt) (Vr p) val
allEqs (v:vs) = all (==v) vs
mkCase p (v:_) = [(PV p, v)]
--- we hope this will be fresh and don't check... in GFC would be safe
qqIdent c i = identC (BS.pack ("q_" ++ prt c ++ "__" ++ show i))
-- we need to replace subterms
replace :: Term -> Term -> Term -> Term
replace old new trm = case trm of
-- these are the important cases, since they can correspond to patterns
QC _ _ | trm == old -> new
App t ts | trm == old -> new
App t ts -> App (repl t) (repl ts)
R _ | isRec && trm == old -> new
_ -> C.composSafeOp repl trm
where
repl = replace old new
isRec = case trm of
R _ -> True
_ -> False
-- It is very important that this is performed only after case
-- expansion since otherwise the order and number of values can
-- be incorrect. Guaranteed by the TComp flag.
values :: Term -> Term
values t = case t of
T ty [(ps,t)] -> T ty [(ps,values t)] -- don't destroy parametrization
T (TComp ty) cs -> V ty [values t | (_, t) <- cs]
_ -> C.composSafeOp values t
|
