Added stack checks to the CPS algorithm

[ghc-hetmet.git] / compiler / codeGen / ClosureInfo.lhs

diff --git a/compiler/codeGen/ClosureInfo.lhs b/compiler/codeGen/ClosureInfo.lhs
index 831e4ec..ad26b2e 100644 (file)
--- a/compiler/codeGen/ClosureInfo.lhs
+++ b/compiler/codeGen/ClosureInfo.lhs
@@ -127,6 +127,10 @@ data C_SRT = NoC_SRT
 needsSRT :: C_SRT -> Bool
 needsSRT NoC_SRT       = False
 needsSRT (C_SRT _ _ _) = True
+
+instance Outputable C_SRT where
+  ppr (NoC_SRT) = ptext SLIT("_no_srt_")
+  ppr (C_SRT label off bitmap) = parens (ppr label <> comma <> ppr off <> comma <> text (show bitmap))
 \end{code}
 
 %************************************************************************
@@ -257,12 +261,12 @@ mkLFThunk thunk_ty top fvs upd_flag
            (might_be_a_function thunk_ty)
 
 might_be_a_function :: Type -> Bool
+-- Return False only if we are *sure* it's a data type
+-- Look through newtypes etc as much as poss
 might_be_a_function ty
-  | Just (tc,_) <- splitTyConApp_maybe (repType ty), 
-    not (isFunTyCon tc)  && not (isAbstractTyCon tc) = False
-       -- don't forget to check for abstract types, which might
-       -- be functions too.
-  | otherwise = True
+  = case splitTyConApp_maybe (repType ty) of
+       Just (tc, _) -> not (isDataTyCon tc)
+       Nothing      -> True
 \end{code}
 
 @mkConLFInfo@ is similar, for constructors.
@@ -583,17 +587,24 @@ getCallMethod this_pkg name (LFCon con) n_args
     ReturnCon con
 
 getCallMethod this_pkg name (LFThunk _ _ updatable std_form_info is_fun) n_args
-  | is_fun     -- Must always "call" a function-typed 
-  = SlowCall   -- thing, cannot just enter it [in eval/apply, the entry code
+  | is_fun     -- *Might* be a function, so we must "call" it (which is always safe)
+  = SlowCall   -- We cannot just enter it [in eval/apply, the entry code
                -- is the fast-entry code]
 
+  -- Since is_fun is False, we are *definitely* looking at a data value
   | updatable || opt_DoTickyProfiling  -- to catch double entry
       {- OLD: || opt_SMP
         I decided to remove this, because in SMP mode it doesn't matter
         if we enter the same thunk multiple times, so the optimisation
         of jumping directly to the entry code is still valid.  --SDM
        -}
-  = ASSERT( n_args == 0 ) EnterIt
+  = EnterIt
+    -- We used to have ASSERT( n_args == 0 ), but actually it is
+    -- possible for the optimiser to generate
+    --   let bot :: Int = error Int "urk"
+    --   in (bot `cast` unsafeCoerce Int (Int -> Int)) 3
+    -- This happens as a result of the case-of-error transformation
+    -- So the right thing to do is just to enter the thing
 
   | otherwise  -- Jump direct to code for single-entry thunks
   = ASSERT( n_args == 0 )