[project @ 2003-07-28 16:05:30 by simonmar]

Disable update-in-place.  In its current form, it has a serious bug:
if the thunk being updated happens to have turned into a BLACKHOLE_BQ,
then the mutable list will be corrupted by the update.

Disabling update-in-place has some performance implications: many
programs are not affected, but one program in nofib (nucleic2) goes
about 20% slower.  However, I can get it to go 300% faster by adding a
few strictness annotations and compiling with -funbox-strict-fields.

2 files changed, 3 insertions, 79 deletions

diff --git a/ghc/compiler/codeGen/CgCon.lhs b/ghc/compiler/codeGen/CgCon.lhs
index 57bfffe748..c83a03527a 100644
--- a/ghc/compiler/codeGen/CgCon.lhs
+++ b/ghc/compiler/codeGen/CgCon.lhs
@@ -32,7 +32,7 @@ import CgUsages		( getRealSp, getVirtSp, setRealAndVirtualSp,
 import CgRetConv	( assignRegs )
 import Constants	( mAX_INTLIKE, mIN_INTLIKE, mAX_CHARLIKE, mIN_CHARLIKE,
 			  mIN_UPD_SIZE )
-import CgHeapery	( allocDynClosure, inPlaceAllocDynClosure )
+import CgHeapery	( allocDynClosure )
 import CgTailCall	( performReturn, mkStaticAlgReturnCode,
 			  returnUnboxedTuple )
 import CLabel		( mkClosureLabel )
@@ -316,47 +316,6 @@ cgReturnDataCon con amodes
 	  jump_to_join_point sequel = absC (CJump (CLbl deflt_lbl CodePtrRep))
 		-- Ignore the sequel: we've already looked at it above
 
-	-- If the sequel is an update frame, we might be able to
-	-- do update in place...
-      UpdateCode
-	|  not (isNullaryDataCon con)  -- no nullary constructors, please
-	&& not (any isFollowableRep (map getAmodeRep amodes))
-					-- no ptrs please (generational gc...)
-	&& closureSize closure_info <= mIN_UPD_SIZE
-					-- don't know the real size of the
-					-- thunk, so assume mIN_UPD_SIZE
-
-	-> 	-- get a new temporary and make it point to the updatee
-	   let 
-		uniq = getUnique con
-	       	temp = CTemp uniq PtrRep 
-	   in
-
-	   profCtrC FSLIT("TICK_UPD_CON_IN_PLACE") 
-			[mkIntCLit (length amodes)] `thenC`
-
-	   getSpRelOffset args_sp			`thenFC` \ sp_rel ->
-	   absC (CAssign temp 
-		    (CMacroExpr PtrRep UPD_FRAME_UPDATEE [CAddr sp_rel])) 
-		`thenC`
-
-	   	-- stomp all over it with the new constructor
-	   inPlaceAllocDynClosure closure_info temp (CReg CurCostCentre) stuff 
-		`thenC`
-
-		-- set Node to point to the closure being returned
-		-- (can't be done earlier: node might conflict with amodes)
-	   absC (CAssign (CReg node) temp) `thenC`
-
-	   	-- pop the update frame off the stack, and do the proper
-	   	-- return.
-	   let new_sp = args_sp - updateFrameSize in
-	   setEndOfBlockInfo (EndOfBlockInfo new_sp (OnStack new_sp)) $
-	   performReturn (AbsCNop) (mkStaticAlgReturnCode con)
-
-	where
-	   (closure_info, stuff) = layOutDynConstr con getAmodeRep amodes
-
       other_sequel	-- The usual case
 	  | isUnboxedTupleCon con -> returnUnboxedTuple amodes
           | otherwise ->	     build_it_then (mkStaticAlgReturnCode con)
diff --git a/ghc/compiler/codeGen/CgHeapery.lhs b/ghc/compiler/codeGen/CgHeapery.lhs
index 7cf05ca65e..2329dcb6d2 100644
--- a/ghc/compiler/codeGen/CgHeapery.lhs
+++ b/ghc/compiler/codeGen/CgHeapery.lhs
@@ -1,14 +1,14 @@
 %
 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
 %
-% $Id: CgHeapery.lhs,v 1.38 2003/07/18 14:39:06 simonmar Exp $
+% $Id: CgHeapery.lhs,v 1.39 2003/07/28 16:05:35 simonmar Exp $
 %
 \section[CgHeapery]{Heap management functions}
 
 \begin{code}
 module CgHeapery (
 	funEntryChecks, altHeapCheck, unbxTupleHeapCheck, thunkChecks,
-	allocDynClosure, inPlaceAllocDynClosure
+	allocDynClosure,
 
         -- new functions, basically inserting macro calls into Code -- HWL
         ,fetchAndReschedule, yield
@@ -368,38 +368,3 @@ allocDynClosure closure_info use_cc blame_cc amodes_with_offsets
     closure_size = closureSize closure_info
     slop_size    = slopSize closure_info
 \end{code}
-
-Occasionally we can update a closure in place instead of allocating
-new space for it.  This is the function that does the business, assuming:
-
-	- the new closure doesn't contain any pointers if we're
-	  using a generational collector.
-
-\begin{code}
-inPlaceAllocDynClosure
-	:: ClosureInfo
-	-> CAddrMode		-- Pointer to beginning of closure
-	-> CAddrMode		-- Cost Centre to stick in the object
-
-	-> [(CAddrMode, VirtualHeapOffset)]	-- Offsets from start of the object
-						-- ie Info ptr has offset zero.
-	-> Code
-
-inPlaceAllocDynClosure closure_info head use_cc amodes_with_offsets
-  = let	-- do_move IS THE ASSIGNMENT FUNCTION
-	 do_move (amode, offset_from_start)
-	   = CAssign (CVal (CIndex head (mkIntCLit offset_from_start) WordRep)
-		     	(getAmodeRep amode))
-		     amode
-    in
-	-- GENERATE THE CODE
-    absC ( mkAbstractCs (
-	   [ 
-		-- don't forget to AWAKEN_BQ_CLOSURE: even though we're
-		-- doing update-in-place, the thunk might still have been
-		-- blackholed and another thread might be waiting on it.
-		CMacroStmt AWAKEN_BQ_CLOSURE [head],
-	        CInitHdr closure_info head use_cc 0{-no alloc-}
- 	   ]
-	   ++ (map do_move amodes_with_offsets)))
-\end{code}