[project @ 2001-10-25 10:00:05 by simonpj]

Fix egregious bug in cloning

diff --git a/ghc/compiler/coreSyn/CorePrep.lhs b/ghc/compiler/coreSyn/CorePrep.lhs
index 906cd6d..6f607b4 100644 (file)
--- a/ghc/compiler/coreSyn/CorePrep.lhs
+++ b/ghc/compiler/coreSyn/CorePrep.lhs
@@ -24,7 +24,7 @@ import VarSet
 import VarEnv
 import Id      ( mkSysLocal, idType, idNewDemandInfo, idArity,
                  setIdType, isPrimOpId_maybe, isFCallId, isGlobalId, 
-                 hasNoBinding, idNewStrictness, 
+                 isLocalId, hasNoBinding, idNewStrictness, 
                  isDataConId_maybe, idUnfolding
                )
 import HscTypes ( ModDetails(..), implicitTyThingIds, typeEnvElts )
@@ -68,9 +68,15 @@ The goal of this pass is to prepare for code generation.
 
 5.  Do the seq/par munging.  See notes with mkCase below.
 
-6.  Clone all local Ids.  This means that Tidy Core has the property
-    that all Ids are unique, rather than the weaker guarantee of
-    no clashes which the simplifier provides.
+6.  Clone all local Ids.
+    This means that all such Ids are unique, rather than the 
+    weaker guarantee of no clashes which the simplifier provides.
+    And that is what the code generator needs.
+
+    We don't clone TyVars. The code gen doesn't need that, 
+    and doing so would be tiresome because then we'd need
+    to substitute in types.
+
 
 7.  Give each dynamic CCall occurrence a fresh unique; this is
     rather like the cloning step above.
@@ -347,8 +353,9 @@ corePrepExprFloat env (Note other_note expr)
     returnUs (floats, Note other_note expr')
 
 corePrepExprFloat env expr@(Lam _ _)
-  = corePrepAnExpr env body            `thenUs` \ body' ->
-    returnUs (nilOL, mkLams bndrs body')
+  = cloneBndrs env bndrs               `thenUs` \ (env', bndrs') ->
+    corePrepAnExpr env' body           `thenUs` \ body' ->
+    returnUs (nilOL, mkLams bndrs' body')
   where
     (bndrs,body) = collectBinders expr
 
@@ -731,16 +738,19 @@ cloneBndrs env bs = mapAccumLUs cloneBndr env bs
 
 cloneBndr  :: CloneEnv -> Var -> UniqSM (CloneEnv, Var)
 cloneBndr env bndr
-  | isGlobalId bndr            -- Top level things, which we don't want
-  = returnUs (env, bndr)       -- to clone, have become GlobalIds by now
-  
-  | otherwise
+  | isLocalId bndr
   = getUniqueUs   `thenUs` \ uniq ->
     let
        bndr' = setVarUnique bndr uniq
     in
     returnUs (extendVarEnv env bndr bndr', bndr')
 
+  | otherwise  -- Top level things, which we don't want
+               -- to clone, have become GlobalIds by now
+               -- And we don't clone tyvars
+  = returnUs (env, bndr)
+  
+
 ------------------------------------------------------------------------------
 -- Cloning ccall Ids; each must have a unique name,
 -- to give the code generator a handle to hang it on