Make CoreTidy retain deadness info (better -ddump-simpl)

[ghc-hetmet.git] / compiler / coreSyn / CoreTidy.lhs

diff --git a/compiler/coreSyn/CoreTidy.lhs b/compiler/coreSyn/CoreTidy.lhs
index 37c6cb3..586f032 100644 (file)
--- a/compiler/coreSyn/CoreTidy.lhs
+++ b/compiler/coreSyn/CoreTidy.lhs
@@ -7,13 +7,6 @@ This module contains "tidying" code for *nested* expressions, bindings, rules.
 The code for *top-level* bindings is in TidyPgm.
 
 \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 CoreTidy (
        tidyExpr, tidyVarOcc, tidyRule, tidyRules 
     ) where
@@ -62,7 +55,7 @@ tidyBind env (Rec prs)
 tidyExpr :: TidyEnv -> CoreExpr -> CoreExpr
 tidyExpr env (Var v)            =  Var (tidyVarOcc env v)
 tidyExpr env (Type ty)          =  Type (tidyType env ty)
-tidyExpr env (Lit lit)          =  Lit lit
+tidyExpr _   (Lit lit)   =  Lit lit
 tidyExpr env (App f a)          =  App (tidyExpr env f) (tidyExpr env a)
 tidyExpr env (Note n e)  =  Note (tidyNote env n) (tidyExpr env e)
 tidyExpr env (Cast e co) =  Cast (tidyExpr env e) (tidyType env co)
@@ -81,23 +74,25 @@ tidyExpr env (Lam b e)
     Lam b (tidyExpr env' e)
 
 ------------  Case alternatives  --------------
-tidyAlt case_bndr env (con, vs, rhs)
+tidyAlt :: CoreBndr -> TidyEnv -> CoreAlt -> CoreAlt
+tidyAlt _case_bndr env (con, vs, rhs)
   = tidyBndrs env vs   =: \ (env', vs) ->
     (con, vs, tidyExpr env' rhs)
 
 ------------  Notes  --------------
-tidyNote env note            = note
+tidyNote :: TidyEnv -> Note -> Note
+tidyNote _ note            = note
 
 ------------  Rules  --------------
 tidyRules :: TidyEnv -> [CoreRule] -> [CoreRule]
-tidyRules env [] = []
+tidyRules _   [] = []
 tidyRules env (rule : rules)
   = tidyRule env rule                  =: \ rule ->
     tidyRules env rules        =: \ rules ->
     (rule : rules)
 
 tidyRule :: TidyEnv -> CoreRule -> CoreRule
-tidyRule env rule@(BuiltinRule {}) = rule
+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) ->
@@ -181,17 +176,24 @@ tidyIdBndr env@(tidy_env, var_env) id
        -- though we could extract it from the Id
        -- 
        -- All nested Ids now have the same IdInfo, namely vanillaIdInfo,
-       -- which should save some space.
+       -- which should save some space; except that we hang onto dead-ness
+       -- (at the moment, solely to make printing tidy core nicer)
        -- But note that tidyLetBndr puts some of it back.
-        ty'              = tidyType env (idType id)
-       id'               = mkUserLocal occ' (idUnique id) ty' noSrcSpan
-                               `setIdInfo` vanillaIdInfo
-       var_env'          = extendVarEnv var_env id 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'
+        new_info | isDeadOcc (idOccInfo id) = deadIdInfo
+                | otherwise                = vanillaIdInfo
     in
      ((tidy_env', var_env'), id')
    }
+
+deadIdInfo :: IdInfo
+deadIdInfo = vanillaIdInfo `setOccInfo` IAmDead
 \end{code}
 
 \begin{code}
+(=:) :: a -> (a -> b) -> b
 m =: k = m `seq` k m
 \end{code}