\section{Common subexpression}
\begin{code}
-{-# OPTIONS -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
--- for details
-
module CSE (
cseProgram
) where
import BasicTypes ( isAlwaysActive )
import Util ( lengthExceeds )
import UniqFM
+import FastString
import Data.List
\end{code}
}
cseBinds :: CSEnv -> [CoreBind] -> [CoreBind]
-cseBinds env [] = []
+cseBinds _ [] = []
cseBinds env (b:bs) = (b':bs')
where
(env1, b') = cseBind env b
in (env', Rec pairs')
+do_one :: CSEnv -> (Id, CoreExpr) -> (CSEnv, (Id, CoreExpr))
do_one env (id, rhs)
= case lookupCSEnv env rhs' of
Just (Var other_id) -> (extendSubst env' id other_id, (id', Var other_id))
-- See Note [CSE for INLINE and NOINLINE]
tryForCSE :: CSEnv -> CoreExpr -> CoreExpr
-tryForCSE env (Type t) = Type t
+tryForCSE _ (Type t) = Type t
tryForCSE env expr = case lookupCSEnv env expr' of
Just smaller_expr -> smaller_expr
Nothing -> expr'
expr' = cseExpr env expr
cseExpr :: CSEnv -> CoreExpr -> CoreExpr
-cseExpr env (Type t) = Type t
-cseExpr env (Lit lit) = Lit lit
+cseExpr _ (Type t) = Type t
+cseExpr _ (Lit lit) = Lit lit
cseExpr env (Var v) = Var (lookupSubst env v)
cseExpr env (App f a) = App (cseExpr env f) (tryForCSE env a)
-cseExpr env (Note InlineMe e) = Note InlineMe e -- See Note [CSE for INLINE and NOINLINE]
+cseExpr _ (Note InlineMe e) = Note InlineMe e -- See Note [CSE for INLINE and NOINLINE]
cseExpr env (Note n e) = Note n (cseExpr env e)
cseExpr env (Cast e co) = Cast (cseExpr env e) co
cseExpr env (Lam b e) = let (env', b') = addBinder env b
(env', bndr') = addBinder env bndr
-cseAlts env scrut' bndr bndr' [(DataAlt con, args, rhs)]
+cseAlts :: CSEnv -> CoreExpr -> CoreBndr -> CoreBndr -> [CoreAlt] -> [CoreAlt]
+
+cseAlts env scrut' bndr _bndr' [(DataAlt con, args, rhs)]
| isUnboxedTupleCon con
-- Unboxed tuples are special because the case binder isn't
-- a real values. See [Note: unboxed tuple case binders]
Var v' -> (v', extendSubst env bndr v') -- See [Note: case binder 1]
-- map: bndr -> v'
- other -> (bndr', extendCSEnv env scrut' (Var bndr')) -- See [Note: case binder 2]
+ _ -> (bndr', extendCSEnv env scrut' (Var bndr')) -- See [Note: case binder 2]
-- map: scrut' -> bndr'
arg_tys = tyConAppArgs (idType bndr)
-- This means that it's good to replace e by e'
-- INVARIANT: The expr in the range has already been CSE'd
+emptyCSEnv :: CSEnv
emptyCSEnv = CS emptyUFM emptyInScopeSet emptyVarEnv
lookupCSEnv :: CSEnv -> CoreExpr -> Maybe CoreExpr
Just pairs -> lookup_list pairs expr
lookup_list :: [(CoreExpr,CoreExpr)] -> CoreExpr -> Maybe CoreExpr
-lookup_list [] expr = Nothing
+lookup_list [] _ = Nothing
lookup_list ((e,e'):es) expr | cheapEqExpr e expr = Just e'
| otherwise = lookup_list es expr
+addCSEnvItem :: CSEnv -> CoreExpr -> CoreExpr -> CSEnv
addCSEnvItem env expr expr' | exprIsBig expr = env
| otherwise = extendCSEnv env expr expr'
-- We don't try to CSE big expressions, because they are expensive to compare
-- (and are unlikely to be the same anyway)
+extendCSEnv :: CSEnv -> CoreExpr -> CoreExpr -> CSEnv
extendCSEnv (CS cs in_scope sub) expr expr'
= CS (addToUFM_C combine cs hash [(expr, expr')]) in_scope sub
where
= WARN( result `lengthExceeds` 4, short_msg $$ nest 2 long_msg ) result
where
result = new ++ old
- short_msg = ptext SLIT("extendCSEnv: long list, length") <+> int (length result)
+ short_msg = ptext (sLit "extendCSEnv: long list, length") <+> int (length result)
long_msg | opt_PprStyle_Debug = (text "hash code" <+> text (show hash)) $$ ppr result
| otherwise = empty
+lookupSubst :: CSEnv -> Id -> Id
lookupSubst (CS _ _ sub) x = case lookupVarEnv sub x of
Just y -> y
Nothing -> x
+extendSubst :: CSEnv -> Id -> Id -> CSEnv
extendSubst (CS cs in_scope sub) x y = CS cs in_scope (extendVarEnv sub x y)
addBinder :: CSEnv -> Id -> (CSEnv, Id)
-addBinder env@(CS cs in_scope sub) v
+addBinder (CS cs in_scope sub) v
| not (v `elemInScopeSet` in_scope) = (CS cs (extendInScopeSet in_scope v) sub, v)
- | isId v = (CS cs (extendInScopeSet in_scope v') (extendVarEnv sub v v'), v')
+ | isIdVar v = (CS cs (extendInScopeSet in_scope v') (extendVarEnv sub v v'), v')
| otherwise = WARN( True, ppr v )
(CS emptyUFM in_scope sub, v)
-- This last case is the unusual situation where we have shadowing of