X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FcodeGen%2FClosureInfo.lhs;h=07a833f5af72f544ae20531f806d8f7d5a7772c5;hb=178eeaa814ab8323a54024e4bb45b4629b7828c8;hp=056d0d81b515f322757d7d3dd5e4cf64a146b7ea;hpb=ad94d40948668032189ad22a0ad741ac1f645f50;p=ghc-hetmet.git

diff --git a/compiler/codeGen/ClosureInfo.lhs b/compiler/codeGen/ClosureInfo.lhs
index 056d0d8..07a833f 100644
--- a/compiler/codeGen/ClosureInfo.lhs
+++ b/compiler/codeGen/ClosureInfo.lhs
@@ -16,7 +16,7 @@ the STG paper.
 -- 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/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module ClosureInfo (
@@ -139,7 +139,7 @@ needsSRT NoC_SRT       = False
 needsSRT (C_SRT _ _ _) = True
 
 instance Outputable C_SRT where
-  ppr (NoC_SRT) = ptext SLIT("_no_srt_")
+  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}
 
@@ -598,7 +598,8 @@ getCallMethod name (LFCon con) n_args
     ReturnCon con
 
 getCallMethod name (LFThunk _ _ updatable std_form_info is_fun) n_args
-  | is_fun 	-- *Might* be a function, so we must "call" it (which is always safe)
+  | is_fun 	-- it *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]
 
@@ -622,11 +623,15 @@ getCallMethod name (LFThunk _ _ updatable std_form_info is_fun) n_args
     JumpToIt (thunkEntryLabel name std_form_info updatable)
 
 getCallMethod name (LFUnknown True) n_args
-  = SlowCall -- might be a function
+  = SlowCall -- Might be a function
 
 getCallMethod name (LFUnknown False) n_args
-  = ASSERT2 ( n_args == 0, ppr name <+> ppr n_args ) 
-    EnterIt -- Not a function
+  | n_args > 0 
+  = WARN( True, ppr name <+> ppr n_args ) 
+    SlowCall	-- Note [Unsafe coerce complications]
+
+  | otherwise
+  = EnterIt -- Not a function
 
 getCallMethod name (LFBlackHole _) n_args
   = SlowCall	-- Presumably the black hole has by now
@@ -676,6 +681,29 @@ isKnownFun (LFLetNoEscape _) = True
 isKnownFun _ = False
 \end{code}
 
+Note [Unsafe coerce complications]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+In some (badly-optimised) DPH code we see this
+   Module X:    rr :: Int = error Int "Urk"
+   Module Y:    ...((X.rr |> g) True) ...
+     where g is an (unsafe) coercion of kind (Int ~ Bool->Bool), say
+
+It's badly optimised, because knowing that 'X.rr' is bottom, we should
+have dumped the application to True.  But it should still work. These
+strange unsafe coercions arise from the case-of-error transformation:
+	(case (error Int "foo") of { ... }) True
+--->	(error Int "foo" |> g) True
+
+Anyway, the net effect is that in STG-land, when casts are discarded,
+we *can* see a value of type Int applied to an argument.  This only happens
+if (a) the programmer made a mistake, or (b) the value of type Int is
+actually bottom.
+
+So it's wrong to trigger an ASSERT failure in this circumstance.  Instead
+we now emit a WARN -- mainly to draw attention to a probably-badly-optimised
+program fragment -- and do the conservative thing which is SlowCall.
+
+
 -----------------------------------------------------------------------------
 SRT-related stuff
 
@@ -978,7 +1006,6 @@ getTyDescription ty
       AppTy fun _      	     -> getTyDescription fun
       FunTy _ res      	     -> '-' : '>' : fun_result res
       TyConApp tycon _ 	     -> getOccString tycon
-      NoteTy (FTVNote _) ty  -> getTyDescription ty
       PredTy sty	     -> getPredTyDescription sty
       ForAllTy _ ty          -> getTyDescription ty
     }