GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/GF/Canon/Share.hs

@@ -0,0 +1,147 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : Share
+-- Maintainer  : AR
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/06/17 14:15:18 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.12 $
+--
+-- Optimizations on GFC code: sharing, parametrization, value sets.
+--
+-- optimization: sharing branches in tables. AR 25\/4\/2003.
+-- following advice of Josef Svenningsson
+-----------------------------------------------------------------------------
+
+module GF.Canon.Share (shareModule, OptSpec, shareOpt, paramOpt, valOpt, allOpt) where
+
+import GF.Canon.AbsGFC
+import GF.Infra.Ident
+import GF.Canon.GFC
+import qualified GF.Canon.CMacros as C
+import GF.Grammar.PrGrammar (prt)
+import GF.Data.Operations
+import Data.List
+import qualified GF.Infra.Modules as M
+
+type OptSpec = [Integer] ---
+
+doOptFactor opt = elem 2 opt
+doOptValues opt = elem 3 opt
+
+shareOpt :: OptSpec
+shareOpt = []
+
+paramOpt :: OptSpec
+paramOpt = [2]
+
+valOpt :: OptSpec
+valOpt = [3]
+
+allOpt :: OptSpec
+allOpt = [2,3]
+
+shareModule :: OptSpec -> (Ident, CanonModInfo) -> (Ident, CanonModInfo)
+shareModule opt (i,m) = case m of
+  M.ModMod (M.Module mt st fs me ops js) -> 
+    (i,M.ModMod (M.Module mt st fs me ops (mapTree (shareInfo opt) js)))
+  _ -> (i,m)
+
+shareInfo opt (c, CncCat ty t m) = (c, CncCat ty (shareOptim opt c t) m)
+shareInfo opt (c, CncFun k xs t m) = (c, CncFun k xs (shareOptim opt c t) m)
+shareInfo _ i = i
+
+-- | the function putting together optimizations
+shareOptim :: OptSpec -> Ident -> Term -> Term
+shareOptim opt c 
+  | doOptFactor opt && doOptValues opt = values . factor c 0
+  | doOptFactor opt = share . factor c 0
+  | doOptValues opt = values    
+  | otherwise = share
+
+-- | we need no counter to create new variable names, since variables are 
+-- local to tables
+share :: Term -> Term
+share t = case t of
+  T ty cs  -> shareT ty [(p, share v) | Cas ps v <- cs, p <- ps]  -- only substant.
+  R lts -> R [Ass l (share t) | Ass l t <- lts]
+  P t l -> P (share t) l
+  S t a -> S (share t) (share a)
+  C t a -> C (share t) (share a)
+  FV ts -> FV (map share ts)
+
+  _ -> t  -- including D, which is always born shared
+
+ where
+   shareT ty = finalize ty . groupC . sortC
+ 
+   sortC :: [(Patt,Term)] -> [(Patt,Term)]
+   sortC = sortBy $ \a b -> compare (snd a) (snd b)
+
+   groupC :: [(Patt,Term)] -> [[(Patt,Term)]]
+   groupC = groupBy $ \a b -> snd a == snd b
+
+   finalize :: CType -> [[(Patt,Term)]] -> Term
+   finalize ty css = T ty [Cas (map fst ps) t | ps@((_,t):_) <- css]
+
+
+-- | do even more: factor parametric branches
+factor :: Ident -> Int -> Term -> Term
+factor c i t = case t of
+  T _ [_] -> t
+  T _ []  -> t
+  T ty cs -> T ty $ factors i [Cas [p] (factor c (i+1) v) | Cas ps v <- cs, p <- ps]
+  R lts   -> R [Ass l (factor c i t) | Ass l t <- lts]
+  P t l   -> P (factor c i t) l
+  S t a   -> S (factor c i t) (factor c i a)
+  C t a   -> C (factor c i t) (factor c i a)
+  FV ts   -> FV (map (factor c i) ts)
+
+  _ -> t
+ where
+
+   factors i psvs =   -- we know psvs has at least 2 elements
+     let p   = pIdent c i
+         vs' = map (mkFun p) psvs
+     in if   allEqs vs'
+        then mkCase p vs' 
+        else psvs
+
+   mkFun p (Cas [patt] val) = replace (C.patt2term patt) (LI p) val
+
+   allEqs (v:vs) = all (==v) vs
+
+   mkCase p (v:_) = [Cas [PV p] v]
+
+pIdent c i = identC ("p_" ++ prt c ++ "__" ++ show i)
+
+
+-- | we need to replace subterms
+replace :: Term -> Term -> Term -> Term
+replace old new trm = case trm of
+  T ty cs -> T ty [Cas p (repl v) | Cas p v <- cs]
+  P t l   -> P (repl t) l
+  S t a   -> S (repl t) (repl a)
+  C t a   -> C (repl t) (repl a)
+  FV ts   -> FV (map repl ts)
+  
+  -- these are the important cases, since they can correspond to patterns  
+  Par c ts | trm == old -> new
+  Par c ts            -> Par c (map repl ts)
+  R _ | isRec && trm == old -> new
+  R lts   -> R [Ass l (repl t) | Ass l t <- lts]
+
+  _ -> trm
+ where
+   repl = replace old new
+   isRec = case trm of
+     R _ -> True
+     _ -> False
+
+values :: Term -> Term
+values t = case t of
+  T ty [c] -> T ty [Cas p (values t) | Cas p t <- [c]] -- preserve parametrization
+  T ty cs  -> V ty [values t | Cas _ t <- cs] -- assumes proper order
+  _ -> C.composSafeOp values t