optimizations on evaluated gf in gfc

src/GF/Devel/OptimizeGF.hs

@@ -0,0 +1,128 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : OptimizeGF
+-- 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.Devel.OptimizeGF (shareModule,unshareModule) where 
+
+import GF.Grammar.Grammar
+import GF.Grammar.Lookup
+import GF.Infra.Ident
+import qualified GF.Grammar.Macros as C
+import GF.Grammar.PrGrammar (prt)
+import qualified GF.Infra.Modules as M
+import GF.Data.Operations
+
+import Data.List
+
+shareModule :: (Ident, SourceModInfo) -> (Ident, SourceModInfo)
+shareModule = processModule optim
+
+unshareModule :: SourceGrammar -> (Ident, SourceModInfo) -> (Ident, SourceModInfo)
+unshareModule gr = processModule (const (unoptim gr))
+
+processModule :: 
+  (Ident -> Term -> Term) -> (Ident, SourceModInfo) -> (Ident, SourceModInfo)
+processModule 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 (Yes t) m) = (c,CncCat ty (Yes (opt c t)) m)
+shareInfo opt (c, CncFun kxs (Yes t) m) = (c,CncFun kxs (Yes (opt c t)) m)
+shareInfo opt (c, ResOper ty (Yes t)) = (c,ResOper ty (Yes (opt c t)))
+shareInfo _ i = i
+
+-- the function putting together optimizations
+optim :: Ident -> Term -> Term
+optim c = values . factor c 0
+
+-- we need no counter to create new variable names, since variables are 
+-- local to tables (only true in GFC) ---
+
+-- 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 ("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
+
+
+-- to undo the effect of factorization
+
+unoptim :: SourceGrammar -> Term -> Term
+unoptim gr = unfactor gr
+
+unfactor :: SourceGrammar -> Term -> Term
+unfactor gr t = case t of
+  T (TTyped ty) [(PV x,u)] -> V ty [restore x v (unfac u) | v <- vals ty]
+  _ -> C.composSafeOp unfac t
+ where
+   unfac = unfactor gr
+   vals  = err error id . allParamValues gr
+   restore x u t = case t of
+     Vr y | y == x -> u
+     _ -> C.composSafeOp (restore x u) t
+
+