coreSyn/CoreTidy.lhs

% % (c) The University of Glasgow 2006 % (c) The AQUA Project, Glasgow University, 1996-1998 % This module contains "tidying" code for *nested* expressions, bindings, rules. The code for *top-level* bindings is in TidyPgm. \begin{code}

    {-# OPTIONS -fno-warn-tabs #-}
    -- The above warning supression flag is a temporary kludge.
    -- While working on this module you are encouraged to remove it and
    -- detab the module (please do the detabbing in a separate patch). See
    --     http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
    -- for details

    module CoreTidy (
    	tidyExpr, tidyVarOcc, tidyRule, tidyRules, tidyUnfolding
        ) where

    #include "HsVersions.h"

    import CoreSyn
    import CoreArity
    import Id
    import IdInfo
    import Type( tidyType, tidyTyVarBndr )
    import Coercion( tidyCo )
    import Var
    import VarEnv
    import UniqFM
    import Name hiding (tidyNameOcc)
    import SrcLoc
    import Maybes
    import Data.List
    import Outputable

\end{code} %************************************************************************ %* * \subsection{Tidying expressions, rules} %* * %************************************************************************ \begin{code}

    tidyBind :: TidyEnv
    	 -> CoreBind
    	 ->  (TidyEnv, CoreBind)

    tidyBind env (NonRec bndr rhs)
      = tidyLetBndr env env (bndr,rhs) =: \ (env', bndr') ->
        (env', NonRec bndr' (tidyExpr env' rhs))

    tidyBind env (Rec prs)
      = let
           (env', bndrs') = mapAccumL (tidyLetBndr env') env prs
        in
        map (tidyExpr env') (map snd prs)	=: \ rhss' ->
        (env', Rec (zip bndrs' rhss'))

    ------------  Expressions  --------------
    tidyExpr :: TidyEnv -> CoreExpr -> CoreExpr
    tidyExpr env (Var v)   	 =  Var (tidyVarOcc env v)
    tidyExpr env (Type ty)  =  Type (tidyType env ty)
    tidyExpr env (Coercion co) = Coercion (tidyCo env co)
    tidyExpr _   (Lit lit)   =  Lit lit
    tidyExpr env (App f a) 	 =  App (tidyExpr env f) (tidyExpr env a)
    tidyExpr env (Tick t e) =  Tick (tidyTickish env t) (tidyExpr env e)
    tidyExpr env (Cast e co) =  Cast (tidyExpr env e) (tidyCo env co)

    tidyExpr env (Let b e)
      = tidyBind env b 	=: \ (env', b') ->
        Let b' (tidyExpr env' e)

    tidyExpr env (Case e b ty alts)
      = tidyBndr env b 	=: \ (env', b) ->
        Case (tidyExpr env e) b (tidyType env ty)
    	 (map (tidyAlt b env') alts)

    tidyExpr env (Lam b e)
      = tidyBndr env b 	=: \ (env', b) ->
        Lam b (tidyExpr env' e)

    ------------  Case alternatives  --------------
    tidyAlt :: CoreBndr -> TidyEnv -> CoreAlt -> CoreAlt
    tidyAlt _case_bndr env (con, vs, rhs)
      = tidyBndrs env vs 	=: \ (env', vs) ->
        (con, vs, tidyExpr env' rhs)

    ------------  Tickish  --------------
    tidyTickish :: TidyEnv -> Tickish Id -> Tickish Id
    tidyTickish env (Breakpoint ix ids) = Breakpoint ix (map (tidyVarOcc env) ids)
    tidyTickish _   other_tickish       = other_tickish

    ------------  Rules  --------------
    tidyRules :: TidyEnv -> [CoreRule] -> [CoreRule]
    tidyRules _   [] = []
    tidyRules env (rule : rules)
      = tidyRule env rule  		=: \ rule ->
        tidyRules env rules 	=: \ rules ->
        (rule : rules)

    tidyRule :: TidyEnv -> CoreRule -> CoreRule
    tidyRule _   rule@(BuiltinRule {}) = rule
    tidyRule env rule@(Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs,
    			  ru_fn = fn, ru_rough = mb_ns })
      = tidyBndrs env bndrs		=: \ (env', bndrs) ->
        map (tidyExpr env') args  	=: \ args ->
        rule { ru_bndrs = bndrs, ru_args = args,
    	   ru_rhs   = tidyExpr env' rhs,
    	   ru_fn    = tidyNameOcc env fn,
    	   ru_rough = map (fmap (tidyNameOcc env')) mb_ns }

\end{code} %************************************************************************ %* * \subsection{Tidying non-top-level binders} %* * %************************************************************************ \begin{code}

    tidyNameOcc :: TidyEnv -> Name -> Name
    -- In rules and instances, we have Names, and we must tidy them too
    -- Fortunately, we can lookup in the VarEnv with a name
    tidyNameOcc (_, var_env) n = case lookupUFM var_env n of
    				Nothing -> n
    				Just v  -> idName v

    tidyVarOcc :: TidyEnv -> Var -> Var
    tidyVarOcc (_, var_env) v = lookupVarEnv var_env v `orElse` v

    -- tidyBndr is used for lambda and case binders
    tidyBndr :: TidyEnv -> Var -> (TidyEnv, Var)
    tidyBndr env var
      | isTyVar var = tidyTyVarBndr env var
      | otherwise   = tidyIdBndr env var

    tidyBndrs :: TidyEnv -> [Var] -> (TidyEnv, [Var])
    tidyBndrs env vars = mapAccumL tidyBndr env vars

    tidyLetBndr :: TidyEnv	       -- Knot-tied version for unfoldings
                -> TidyEnv 	       -- The one to extend
                -> (Id, CoreExpr) -> (TidyEnv, Var)
    -- Used for local (non-top-level) let(rec)s
    tidyLetBndr rec_tidy_env env (id,rhs)
      = ((tidy_occ_env,new_var_env), final_id)
      where
        ((tidy_occ_env,var_env), new_id) = tidyIdBndr env id
        new_var_env = extendVarEnv var_env id final_id
           -- Override the env we get back from tidyId with the
           -- new IdInfo so it gets propagated to the usage sites.

    	-- We need to keep around any interesting strictness and
    	-- demand info because later on we may need to use it when
    	-- converting to A-normal form.
    	-- eg.
    	--	f (g x),  where f is strict in its argument, will be converted
    	--	into  case (g x) of z -> f z  by CorePrep, but only if f still
    	-- 	has its strictness info.
    	--
    	-- Similarly for the demand info - on a let binder, this tells
    	-- CorePrep to turn the let into a case.
    	--
    	-- Similarly arity info for eta expansion in CorePrep
    	--
    	-- Set inline-prag info so that we preseve it across
    	-- separate compilation boundaries
        final_id = new_id `setIdInfo` new_info
        idinfo   = idInfo id
        new_info = idInfo new_id
    		`setArityInfo`		exprArity rhs
                    `setStrictnessInfo`	strictnessInfo idinfo
                    `setDemandInfo`	        demandInfo idinfo
    		`setInlinePragInfo`	inlinePragInfo idinfo
    		`setUnfoldingInfo`	new_unf

        new_unf | isStableUnfolding unf = tidyUnfolding rec_tidy_env unf (panic "tidy_unf")
                | otherwise	            = noUnfolding
        unf = unfoldingInfo idinfo

    -- Non-top-level variables
    tidyIdBndr :: TidyEnv -> Id -> (TidyEnv, Id)
    tidyIdBndr env@(tidy_env, var_env) id
      = -- Do this pattern match strictly, otherwise we end up holding on to
        -- stuff in the OccName.
        case tidyOccName tidy_env (getOccName id) of { (tidy_env', occ') ->
        let
    	-- Give the Id a fresh print-name, *and* rename its type
    	-- The SrcLoc isn't important now,
    	-- though we could extract it from the Id
    	--
            ty'      = tidyType env (idType id)
            name'    = mkInternalName (idUnique id) occ' noSrcSpan
    	id'      = mkLocalIdWithInfo name' ty' new_info
    	var_env' = extendVarEnv var_env id id'

    	-- Note [Tidy IdInfo]
            new_info = vanillaIdInfo `setOccInfo` occInfo old_info
    	old_info = idInfo id
        in
        ((tidy_env', var_env'), id')
       }

    ------------ Unfolding  --------------
    tidyUnfolding :: TidyEnv -> Unfolding -> Unfolding -> Unfolding
    tidyUnfolding tidy_env df@(DFunUnfolding { df_bndrs = bndrs, df_args = args }) _
      = df { df_bndrs = bndrs', df_args = map (tidyExpr tidy_env') args }
      where
        (tidy_env', bndrs') = tidyBndrs tidy_env bndrs

    tidyUnfolding tidy_env
                  unf@(CoreUnfolding { uf_tmpl = unf_rhs, uf_src = src })
                  unf_from_rhs
      | isStableSource src
      = unf { uf_tmpl = tidyExpr tidy_env unf_rhs }	   -- Preserves OccInfo
      | otherwise
      = unf_from_rhs
    tidyUnfolding _ unf _ = unf	-- NoUnfolding or OtherCon

\end{code} Note [Tidy IdInfo] ~~~~~~~~~~~~~~~~~~ All nested Ids now have the same IdInfo, namely vanillaIdInfo, which should save some space; except that we preserve occurrence info for two reasons: (a) To make printing tidy core nicer (b) Because we tidy RULES and InlineRules, which may then propagate via --make into the compilation of the next module, and we want the benefit of that occurrence analysis when we use the rule or or inline the function. In particular, it's vital not to lose loop-breaker info, else we get an infinite inlining loop Note that tidyLetBndr puts more IdInfo back. \begin{code}

    (=:) :: a -> (a -> b) -> b
    m =: k = m `seq` k m

\end{code}