add -fsimpleopt-before-flatten

[ghc-hetmet.git] / compiler / simplCore / SimplEnv.lhs

diff --git a/compiler/simplCore/SimplEnv.lhs b/compiler/simplCore/SimplEnv.lhs
index 865acdc..d9eea39 100644 (file)
--- a/compiler/simplCore/SimplEnv.lhs
+++ b/compiler/simplCore/SimplEnv.lhs
@@ -1,5 +1,5 @@
 %
-% (c) The AQUA Project, Glasgow University, 1993-1998
+o% (c) The AQUA Project, Glasgow University, 1993-1998
 %
 \section[SimplMonad]{The simplifier Monad}
 
@@ -12,18 +12,14 @@ module SimplEnv (
        -- The simplifier mode
        setMode, getMode, updMode,
 
-       -- Switch checker
-       SwitchChecker, SwitchResult(..), getSwitchChecker, getSimplIntSwitch,
-       isAmongSimpl, intSwitchSet, switchIsOn,
-
-       setEnclosingCC, getEnclosingCC,
+        setEnclosingCC, getEnclosingCC,
 
        -- Environments
        SimplEnv(..), StaticEnv, pprSimplEnv,   -- Temp not abstract
        mkSimplEnv, extendIdSubst, SimplEnv.extendTvSubst, 
        zapSubstEnv, setSubstEnv, 
        getInScope, setInScope, setInScopeSet, modifyInScope, addNewInScopeIds,
-       getSimplRules, inGentleMode,
+        getSimplRules,
 
        SimplSR(..), mkContEx, substId, lookupRecBndr,
 
@@ -50,6 +46,8 @@ import VarEnv
 import VarSet
 import OrdList
 import Id
+import MkCore
+import TysWiredIn
 import qualified CoreSubst
 import qualified Type          ( substTy, substTyVarBndr, substTyVar )
 import Type hiding             ( substTy, substTyVarBndr, substTyVar )
@@ -106,8 +104,7 @@ data SimplEnv
      -- wrt the original expression
 
        seMode      :: SimplifierMode,
-       seChkr      :: SwitchChecker,
-       seCC        :: CostCentreStack, -- The enclosing CCS (when profiling)
+        seCC        :: CostCentreStack, -- The enclosing CCS (when profiling)
 
        -- The current substitution
        seTvSubst   :: TvSubstEnv,      -- InTyVar |--> OutType
@@ -223,19 +220,40 @@ seIdSubst:
 
 
 \begin{code}
-mkSimplEnv :: SwitchChecker -> SimplifierMode -> SimplEnv
-mkSimplEnv switches mode
-  = SimplEnv { seChkr = switches, seCC = subsumedCCS, 
-              seMode = mode, seInScope = emptyInScopeSet, 
-              seFloats = emptyFloats,
-              seTvSubst = emptyVarEnv, seIdSubst = emptyVarEnv }
+mkSimplEnv :: SimplifierMode -> SimplEnv
+mkSimplEnv mode
+  = SimplEnv { seCC = subsumedCCS
+             , seMode = mode
+             , seInScope = init_in_scope
+             , seFloats = emptyFloats
+             , seTvSubst = emptyVarEnv
+             , seIdSubst = emptyVarEnv }
        -- The top level "enclosing CC" is "SUBSUMED".
 
----------------------
-getSwitchChecker :: SimplEnv -> SwitchChecker
-getSwitchChecker env = seChkr env
+init_in_scope :: InScopeSet
+init_in_scope = mkInScopeSet (unitVarSet (mkWildValBinder unitTy))
+              -- See Note [WildCard binders]
+\end{code}
 
----------------------
+Note [WildCard binders]
+~~~~~~~~~~~~~~~~~~~~~~~
+The program to be simplified may have wild binders
+    case e of wild { p -> ... }
+We want to *rename* them away, so that there are no
+occurrences of 'wild-id' (with wildCardKey).  The easy
+way to do that is to start of with a representative
+Id in the in-scope set
+
+There can be be *occurrences* of wild-id.  For example,
+MkCore.mkCoreApp transforms
+   e (a /# b)   -->   case (a /# b) of wild { DEFAULT -> e wild }
+This is ok provided 'wild' isn't free in 'e', and that's the delicate
+thing. Generally, you want to run the simplifier to get rid of the
+wild-ids before doing much else.
+
+It's a very dark corner of GHC.  Maybe it should be cleaned up.
+
+\begin{code}
 getMode :: SimplEnv -> SimplifierMode
 getMode env = seMode env
 
@@ -245,11 +263,6 @@ setMode mode env = env { seMode = mode }
 updMode :: (SimplifierMode -> SimplifierMode) -> SimplEnv -> SimplEnv
 updMode upd env = env { seMode = upd (seMode env) }
 
-inGentleMode :: SimplEnv -> Bool
-inGentleMode env = case seMode env of
-                       SimplGently {} -> True
-                       _other         -> False
-
 ---------------------
 getEnclosingCC :: SimplEnv -> CostCentreStack
 getEnclosingCC env = seCC env