X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2FbasicTypes%2FDemand.lhs;h=a038a23f6ac944046e361a56fa8344f19b223595;hb=52bd2cc7a9f328e6a7f3f50ac0055a5361f457c1;hp=cb45ddcd4ae558dd67b8ed90783a2d97bee03b58;hpb=4e7d56fde0f44d38bbb9a6fc72cf9c603264899d;p=ghc-hetmet.git

diff --git a/ghc/compiler/basicTypes/Demand.lhs b/ghc/compiler/basicTypes/Demand.lhs
index cb45ddc..a038a23 100644
--- a/ghc/compiler/basicTypes/Demand.lhs
+++ b/ghc/compiler/basicTypes/Demand.lhs
@@ -4,19 +4,30 @@
 \section[Demand]{@Demand@: the amount of demand on a value}
 
 \begin{code}
+#ifndef OLD_STRICTNESS
+module Demand () where
+#else
+
 module Demand(
 	Demand(..),
 
-	wwLazy, wwStrict, wwUnpackData, wwUnpackNew, wwPrim, wwEnum, 
+	wwLazy, wwStrict, wwUnpack, wwPrim, wwEnum, 
 	isStrict, isLazy, isPrim,
 
-	pprDemands, seqDemand, seqDemands
+	pprDemands, seqDemand, seqDemands,
+
+	StrictnessInfo(..),	
+	mkStrictnessInfo,
+	noStrictnessInfo,
+	ppStrictnessInfo, seqStrictnessInfo,
+	isBottomingStrictness, appIsBottom,
+
      ) where
 
 #include "HsVersions.h"
 
-import BasicTypes	( NewOrData(..) )
 import Outputable
+import Util ( listLengthCmp )
 \end{code}
 
 
@@ -39,7 +50,6 @@ data Demand
 			-- calling-convention magic)
 
   | WwUnpack		-- Argument is strict & a single-constructor type
-	NewOrData
 	Bool		-- True <=> wrapper unpacks it; False <=> doesn't
 	[Demand]	-- Its constituent parts (whose StrictInfos
 			-- are in the list) should be passed
@@ -59,15 +69,14 @@ type MaybeAbsent = Bool -- True <=> not even used
 -- versions that don't worry about Absence:
 wwLazy	    = WwLazy 	  False
 wwStrict    = WwStrict
-wwUnpackData xs = WwUnpack DataType False xs
-wwUnpackNew  x  = WwUnpack NewType  False [x]
+wwUnpack xs = WwUnpack False xs
 wwPrim	    = WwPrim
 wwEnum	    = WwEnum
 
 seqDemand :: Demand -> ()
-seqDemand (WwLazy a)         = a `seq` ()
-seqDemand (WwUnpack nd b ds) = nd `seq` b `seq` seqDemands ds
-seqDemand other		     = ()
+seqDemand (WwLazy a)      = a `seq` ()
+seqDemand (WwUnpack b ds) = b `seq` seqDemands ds
+seqDemand other		  = ()
 
 seqDemands [] = ()
 seqDemands (d:ds) = seqDemand d `seq` seqDemands ds
@@ -81,25 +90,18 @@ seqDemands (d:ds) = seqDemand d `seq` seqDemands ds
 %************************************************************************
 
 \begin{code}
+isLazy :: Demand -> Bool
+isLazy (WwLazy _) = True
+isLazy _	  = False
+
 isStrict :: Demand -> Bool
-isStrict (WwUnpack NewType _ ds) = isStrict (head ds)
-isStrict (WwUnpack other _ _)    = True
-isStrict WwStrict = True
-isStrict WwEnum	  = True
-isStrict WwPrim	  = True
-isStrict _	  = False
+isStrict d = not (isLazy d)
 
 isPrim :: Demand -> Bool
 isPrim WwPrim = True
 isPrim other  = False
 \end{code}
 
-\begin{code}
-isLazy :: Demand -> Bool
-isLazy (WwLazy False) = True	-- NB "Absent" args do *not* count!
-isLazy _	      = False	-- (as they imply a worker)
-\end{code}
-
 
 %************************************************************************
 %*									*
@@ -120,13 +122,9 @@ pprDemand (WwLazy True)   	 = char 'A'
 pprDemand WwStrict	      	 = char 'S'
 pprDemand WwPrim	      	 = char 'P'
 pprDemand WwEnum	      	 = char 'E'
-pprDemand (WwUnpack nd wu args)  = char ch <> parens (hcat (map pprDemand args))
+pprDemand (WwUnpack wu args)     = char ch <> parens (hcat (map pprDemand args))
 				      where
-					ch = case nd of
-						DataType | wu        -> 'U'
-							 | otherwise -> 'u'
-						NewType  | wu        -> 'N'
-							 | otherwise -> 'n'
+					ch = if wu then 'U' else 'u'
 
 instance Outputable Demand where
     ppr (WwLazy False) = empty
@@ -134,49 +132,77 @@ instance Outputable Demand where
 
 instance Show Demand where
     showsPrec p d = showsPrecSDoc p (ppr d)
+
+-- Reading demands is done in Lex.lhs
 \end{code}
 
 
+%************************************************************************
+%*									*
+\subsection[strictness-IdInfo]{Strictness info about an @Id@}
+%*									*
+%************************************************************************
+
+We specify the strictness of a function by giving information about
+each of the ``wrapper's'' arguments (see the description about
+worker/wrapper-style transformations in the PJ/Launchbury paper on
+unboxed types).
+
+The list of @Demands@ specifies: (a)~the strictness properties of a
+function's arguments; and (b)~the type signature of that worker (if it
+exists); i.e. its calling convention.
+
+Note that the existence of a worker function is now denoted by the Id's
+workerInfo field.
+
 \begin{code}
-{-	------------------- OMITTED NOW -------------------------------
-	-- Reading demands is done in Lex.lhs
-	-- Also note that the (old) code here doesn't take proper
-	-- account of the 'B' suffix for bottoming functions
+data StrictnessInfo
+  = NoStrictnessInfo
 
-#ifdef REALLY_HASKELL_1_3
+  | StrictnessInfo [Demand] 	-- Demands on the arguments.
 
-instance Read Demand where
-    readList str = read_em [] str
+		   Bool		-- True <=> the function diverges regardless of its arguments
+				-- Useful for "error" and other disguised variants thereof.  
+				-- BUT NB: f = \x y. error "urk"
+				-- 	   will have info  SI [SS] True
+				-- but still (f) and (f 2) are not bot; only (f 3 2) is bot
+  deriving( Eq )
 
-instance Show Demand where
-    showsPrec p d = showsPrecSDoc p (ppr d)
+	-- NOTA BENE: if the arg demands are, say, [S,L], this means that
+	-- 	(f bot) is not necy bot, only (f bot x) is bot
+	-- We simply cannot express accurately the strictness of a function
+	-- like		f = \x -> case x of (a,b) -> \y -> ...
+	-- The up-side is that we don't need to restrict the strictness info
+	-- to the visible arity of the function.
 
-#else
+seqStrictnessInfo :: StrictnessInfo -> ()
+seqStrictnessInfo (StrictnessInfo ds b) = b `seq` seqDemands ds
+seqStrictnessInfo other		        = ()
+\end{code}
 
-instance Text Demand where
-    readList str  = read_em [] str
-    showsPrec p d = showsPrecSDoc p (ppr d)
-#endif
-
-readDemands :: String -> 
-
-read_em acc ('L' : xs)	= read_em (WwLazy   False : acc) xs
-read_em acc ('A' : xs)	= read_em (WwLazy   True  : acc) xs
-read_em acc ('S' : xs)	= read_em (WwStrict : acc) xs
-read_em acc ('P' : xs)	= read_em (WwPrim : acc) xs
-read_em acc ('E' : xs)	= read_em (WwEnum : acc) xs
-read_em acc (')' : xs)	= [(reverse acc, xs)]
-read_em acc ( 'U'  : '(' : xs) = do_unpack DataType True  acc xs
-read_em acc ( 'u'  : '(' : xs) = do_unpack DataType False acc xs
-read_em acc ( 'N'  : '(' : xs) = do_unpack NewType  True  acc xs
-read_em acc ( 'n'  : '(' : xs) = do_unpack NewType  False acc xs
-read_em acc rest	= [(reverse acc, rest)]
-
-do_unpack new_or_data wrapper_unpacks acc xs
-	  = case (read_em [] xs) of
-	      [(stuff, rest)] -> read_em (WwUnpack new_or_data wrapper_unpacks stuff : acc) rest
-	      _ -> pprPanic "Demand.do_unpack:" (ppr acc <+> dcolon <> text xs)
-
--------------------- END OF OMISSION ------------------------------  -}
+\begin{code}
+mkStrictnessInfo :: ([Demand], Bool) -> StrictnessInfo
+
+mkStrictnessInfo (xs, is_bot)
+  | all totally_boring xs && not is_bot	= NoStrictnessInfo		-- Uninteresting
+  | otherwise		    	        = StrictnessInfo xs is_bot
+  where
+    totally_boring (WwLazy False) = True
+    totally_boring other	  = False
+
+noStrictnessInfo = NoStrictnessInfo
+
+isBottomingStrictness (StrictnessInfo _ bot) = bot
+isBottomingStrictness NoStrictnessInfo       = False
+
+-- appIsBottom returns true if an application to n args would diverge
+appIsBottom (StrictnessInfo ds bot)   n = bot && (listLengthCmp ds n /=GT) -- not more than 'n' elts in 'ds'.
+appIsBottom  NoStrictnessInfo	      n	= False
+
+ppStrictnessInfo NoStrictnessInfo		   = empty
+ppStrictnessInfo (StrictnessInfo wrapper_args bot) = hsep [pprDemands wrapper_args bot]
 \end{code}
 
+\begin{code}
+#endif /* OLD_STRICTNESS */
+\end{code}