X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Futils%2FUniqFM.lhs;h=9a3d6063ab3310af98830d0f09ed6176411807c5;hb=aa24834506285f4b4a0d78f28ac6978a6b5b9087;hp=642522d3e749b0ff48994ce9f1d3beaa924156cd;hpb=e7033cf34a8a478758c932d4b8cac04198531299;p=ghc-hetmet.git

diff --git a/compiler/utils/UniqFM.lhs b/compiler/utils/UniqFM.lhs
index 642522d..9a3d606 100644
--- a/compiler/utils/UniqFM.lhs
+++ b/compiler/utils/UniqFM.lhs
@@ -48,7 +48,7 @@ module UniqFM (
 	isNullUFM,
 	lookupUFM, lookupUFM_Directly,
 	lookupWithDefaultUFM, lookupWithDefaultUFM_Directly,
-	eltsUFM, keysUFM,
+	eltsUFM, keysUFM, splitUFM,
 	ufmToList 
     ) where
 
@@ -130,6 +130,8 @@ hashUFM		:: UniqFM elt -> Int
 elemUFM		:: Uniquable key => key -> UniqFM elt -> Bool
 elemUFM_Directly:: Unique -> UniqFM elt -> Bool
 
+splitUFM        :: Uniquable key => UniqFM elt -> key -> (UniqFM elt, Maybe elt, UniqFM elt)
+		   -- Splits a UFM into things less than, equal to, and greater than the key
 lookupUFM	:: Uniquable key => UniqFM elt -> key -> Maybe elt
 lookupUFM_Directly  -- when you've got the Unique already
 		:: UniqFM elt -> Unique -> Maybe elt
@@ -137,7 +139,6 @@ lookupWithDefaultUFM
 		:: Uniquable key => UniqFM elt -> elt -> key -> elt
 lookupWithDefaultUFM_Directly
 		:: UniqFM elt -> elt -> Unique -> elt
-
 keysUFM		:: UniqFM elt -> [Unique]	-- Get the keys
 eltsUFM		:: UniqFM elt -> [elt]
 ufmToList	:: UniqFM elt -> [(Unique, elt)]
@@ -358,7 +359,7 @@ plusUFM_C f fm1 fm2	= mix_trees fm1 fm2
 			(mix_trees t2 t2')
 		-- Now the 4 different other ways; all like this:
 		--
-		-- Given j >^ j' (and, say,  j > j')
+ -- Given j >^ j' (and, say,  j > j')
 		--
 		--	  j		j'			 j
 		--	 / \	+      / \	==>		/ \
@@ -608,6 +609,25 @@ lookUp fm i	    = lookup_tree fm
 	  | otherwise	= lookup_tree t2
 
 	lookup_tree EmptyUFM = panic "lookup Failed"
+
+-------------------
+splitUFM fm key = split fm (getKeyFastInt (getUnique key))
+
+split :: UniqFM a -> FastInt -> (UniqFM a, Maybe a, UniqFM a)
+-- Splits a UFM into things less than, equal to, and greater than the key
+split EmptyUFM _ = (EmptyUFM, Nothing, EmptyUFM)
+split fm i       = go fm
+  where
+    go (LeafUFM j b) | i <# j    = (EmptyUFM,    Nothing, LeafUFM j b)
+       		     | i ># j    = (LeafUFM j b, Nothing, EmptyUFM)
+                     | otherwise = (EmptyUFM,    Just b,  EmptyUFM)
+       		     
+    go (NodeUFM j p t1 t2) 
+      | j ># i 
+      , (lt, eq, gt) <- go t1 = (lt, eq, mkSLNodeUFM (NodeUFMData j p) gt t2)
+      | (lt, eq, gt) <- go t2 = (mkLSNodeUFM (NodeUFMData j p) t1 lt, eq, gt)
+
+    go EmptyUFM = panic "splitUFM failed"
 \end{code}
 
 folds are *wonderful* things.
@@ -643,7 +663,9 @@ functionality, but may do a few needless evaluations.
 
 \begin{code}
 mkLeafUFM :: FastInt -> a -> UniqFM a
-mkLeafUFM i a	  = LeafUFM i a
+mkLeafUFM i a =
+  ASSERT (iBox i >= 0) -- Note [Uniques must be positive]
+  LeafUFM i a
 
 -- The *ONLY* ways of building a NodeUFM.
 
@@ -801,8 +823,8 @@ getCommonNodeUFMData (NodeUFMData i p) (NodeUFMData i2 p2)
   | p <# p2	= getCommonNodeUFMData_ p2 (j `quotFastInt` (p2 `quotFastInt` p)) j2
   | otherwise	= getCommonNodeUFMData_ p j (j2 `quotFastInt` (p `quotFastInt` p2))
   where
-    j  = i  `quotFastInt` (shiftL1 p)
-    j2 = i2 `quotFastInt` (shiftL1 p2)
+    !j  = i  `quotFastInt` (shiftL1 p)
+    !j2 = i2 `quotFastInt` (shiftL1 p2)
 
     getCommonNodeUFMData_ :: FastInt -> FastInt -> FastInt -> NodeUFMData
 
@@ -848,3 +870,21 @@ use_snd :: a -> b -> b
 use_snd _ b = b
 \end{code}
 
+{- Note [Uniques must be positive]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The getCommonNodeUFMData function assumes that the nodes use
+positive uniques. Specifically, the inner `loop' shifts the
+low bits out of two uniques until the shifted uniques are the same.
+At the same time, it computes a new delta, by shifting
+to the left.
+
+The failure case I (JPD) encountered:
+If one of the uniques is negative, the shifting may continue
+until all 64 bits have been shifted out, resulting in a new delta
+of 0, which is wrong and can trigger later assertion failures.
+
+Where do the negative uniques come from? Both Simom M and
+I have run into this problem when hashing a data structure.
+In both cases, we have avoided the problem by ensuring that
+the hashes remain positive.
+-}