1 #if __GLASGOW_HASKELL__ >= 611
2 {-# OPTIONS_GHC -XNoMonoLocalBinds #-}
4 -- Norman likes local bindings
5 -- If this module lives on I'd like to get rid of this flag in due course
7 module CmmBuildInfoTables
8 ( CAFSet, CAFEnv, CmmTopForInfoTables(..), cafAnal, localCAFInfo, mkTopCAFInfo
9 , setInfoTableSRT, setInfoTableStackMap
10 , TopSRT, emptySRT, srtToData
12 , finishInfoTables, lowerSafeForeignCalls
13 , cafTransfers, liveSlotTransfers
14 , extendEnvWithSafeForeignCalls, extendEnvsForSafeForeignCalls )
17 #include "HsVersions.h"
21 import qualified Prelude as P
28 import Cmm hiding (blockId)
42 import MkZipCfgCmm hiding (CmmAGraph, CmmBlock, CmmTopZ, CmmZ, CmmGraph)
52 import ZipCfg hiding (zip, unzip, last)
53 import qualified ZipCfg as G
57 ----------------------------------------------------------------
58 -- Building InfoTables
61 -----------------------------------------------------------------------
64 -- Given a block ID, we return a representation of the layout of the stack,
65 -- as suspended before entering that block.
66 -- (For a return site to a function call, the layout does not include the
67 -- parameter passing area (or the "return address" on the stack)).
68 -- If the element is `Nothing`, then it represents a word of the stack that
69 -- does not contain a live pointer.
70 -- If the element is `Just` a register, then it represents a live spill slot
71 -- for a pointer; we assume that a pointer is the size of a word.
72 -- The head of the list represents the young end of the stack where the infotable
73 -- pointer for the block `Bid` is stored.
74 -- The infotable pointer itself is not included in the list.
75 -- Call areas are also excluded from the list: besides the stuff in the update
76 -- frame (and the return infotable), call areas should never be live across
79 -- RTS Invariant: All pointers must be word-aligned because each bit in the bitmap
80 -- represents a word. Consequently, we have to be careful when we see a live slot
81 -- on the stack: if we have packed multiple sub-word values into a word,
82 -- we have to make sure that we only mark the entire word as a non-pointer.
84 -- Also, don't forget to stop at the old end of the stack (oldByte),
85 -- which may differ depending on whether there is an update frame.
88 = ( Int -- Offset from oldest byte of Old area
89 , LocalReg -- The register
90 , Int) -- Width of the register
92 live_ptrs :: ByteOff -> BlockEnv SubAreaSet -> AreaMap -> BlockId -> [Maybe LocalReg]
93 live_ptrs oldByte slotEnv areaMap bid =
94 -- pprTrace "live_ptrs for" (ppr bid <+> text (show oldByte ++ "-" ++ show youngByte) <+>
96 -- pprTrace ("stack layout for " ++ show bid ++ ": ") (ppr res) $ res
98 where res = reverse $ slotsToList youngByte liveSlots []
100 slotsToList :: Int -> [RegSlotInfo] -> [Maybe LocalReg] -> [Maybe LocalReg]
101 -- n starts at youngByte and is decremented down to oldByte
102 -- Returns a list, one element per word, with
103 -- (Just r) meaning 'pointer register r is saved here',
104 -- Nothing meaning 'non-pointer or empty'
106 slotsToList n [] results | n == oldByte = results -- at old end of stack frame
108 slotsToList n (s : _) _ | n == oldByte =
109 pprPanic "slot left off live_ptrs" (ppr s <+> ppr oldByte <+>
110 ppr n <+> ppr liveSlots <+> ppr youngByte)
112 slotsToList n _ _ | n < oldByte =
113 panic "stack slots not allocated on word boundaries?"
115 slotsToList n l@((n', r, w) : rst) results =
116 if n == (n' + w) then -- slot's young byte is at n
117 ASSERT (not (isPtr r) ||
118 (n `mod` wORD_SIZE == 0 && w == wORD_SIZE)) -- ptrs must be aligned
119 slotsToList next (dropWhile (non_ptr_younger_than next) rst)
120 (stack_rep : results)
121 else slotsToList next (dropWhile (non_ptr_younger_than next) l)
123 where next = n - wORD_SIZE
124 stack_rep = if isPtr r then Just r else Nothing
126 slotsToList n [] results = slotsToList (n - wORD_SIZE) [] (Nothing : results)
128 non_ptr_younger_than next (n', r, w) =
130 ASSERT (not (isPtr r))
132 isPtr = isGcPtrType . localRegType
134 liveSlots :: [RegSlotInfo]
135 liveSlots = sortBy (\ (off,_,_) (off',_,_) -> compare off' off)
136 (foldFM (\_ -> flip $ foldl add_slot) [] slots)
138 add_slot :: [RegSlotInfo] -> SubArea -> [RegSlotInfo]
139 add_slot rst (a@(RegSlot r@(LocalReg _ ty)), off, w) =
140 if off == w && widthInBytes (typeWidth ty) == w then
141 (expectJust "add_slot" (lookupFM areaMap a), r, w) : rst
142 else panic "live_ptrs: only part of a variable live at a proc point"
143 add_slot rst (CallArea Old, _, _) =
144 rst -- the update frame (or return infotable) should be live
145 -- would be nice to check that only that part of the callarea is live...
146 add_slot rst ((CallArea _), _, _) =
148 -- JD: THIS ISN'T CURRENTLY A CORRECTNESS PROBLEM, BUT WE SHOULD REALLY
149 -- MAKE LIVENESS INFO AROUND CALLS MORE PRECISE -- FOR NOW, A 32-BIT
150 -- FLOAT PADS OUT TO 64 BITS, BUT WE ASSUME THE WHOLE PARAMETER-PASSING
151 -- AREA IS LIVE (WHICH IT ISN'T...). WE SHOULD JUST PUT THE LIVE AREAS
152 -- IN THE CALL NODES, WHICH SHOULD EVENTUALLY HAVE LIVE REGISTER AS WELL,
153 -- SO IT'S ALL GOING IN THE SAME DIRECTION.
154 -- pprPanic "CallAreas must not be live across function calls" (ppr bid <+> ppr c)
156 slots :: SubAreaSet -- The SubAreaSet for 'bid'
157 slots = expectJust "live_ptrs slots" $ lookupBlockEnv slotEnv bid
158 youngByte = expectJust "live_ptrs bid_pos" $ lookupFM areaMap (CallArea (Young bid))
160 -- Construct the stack maps for the given procedure.
161 setInfoTableStackMap :: SlotEnv -> AreaMap -> CmmTopForInfoTables -> CmmTopForInfoTables
162 setInfoTableStackMap _ _ t@(NoInfoTable _) = t
163 setInfoTableStackMap slotEnv areaMap t@(FloatingInfoTable _ bid updfr_off) =
164 updInfo (const (live_ptrs updfr_off slotEnv areaMap bid)) id t
165 setInfoTableStackMap slotEnv areaMap
166 t@(ProcInfoTable (CmmProc (CmmInfo _ _ _) _ _ ((_, Just updfr_off), _)) procpoints) =
167 case blockSetToList procpoints of
168 [bid] -> updInfo (const (live_ptrs updfr_off slotEnv areaMap bid)) id t
169 _ -> panic "setInfoTableStackMap: unexpected number of procpoints"
170 -- until we stop splitting the graphs at procpoints in the native path
171 setInfoTableStackMap _ _ t = pprPanic "unexpected case for setInfoTableStackMap" (ppr t)
175 -----------------------------------------------------------------------
178 -- WE NEED AN EXAMPLE HERE.
179 -- IN PARTICULAR, WE NEED TO POINT OUT THE DISTINCTION BETWEEN
180 -- FUNCTIONS WITH STATIC CLOSURES AND THOSE THAT MUST BE CONSTRUCTED
181 -- DYNAMICALLY (AND HENCE CAN'T BE REFERENCED IN AN SRT).
182 -- IN THE LATTER CASE, WE HAVE TO TAKE ALL THE CAFs REFERENCED BY
183 -- THE CLOSURE AND INLINE THEM INTO ANY SRT THAT MAY MENTION THE CLOSURE.
184 -- (I.E. TAKE THE TRANSITIVE CLOSURE, but only for non-static closures).
187 -----------------------------------------------------------------------
188 -- Finding the CAFs used by a procedure
190 type CAFSet = FiniteMap CLabel ()
191 type CAFEnv = BlockEnv CAFSet
193 -- First, an analysis to find live CAFs.
194 cafLattice :: DataflowLattice CAFSet
195 cafLattice = DataflowLattice "live cafs" emptyFM add False
196 where add new old = if sizeFM new' > sizeFM old then aTx new' else noTx new'
197 where new' = new `plusFM` old
199 cafTransfers :: BackwardTransfers Middle Last CAFSet
200 cafTransfers = BackwardTransfers first middle last
201 where first _ live = live
202 middle m live = foldExpDeepMiddle addCaf m live
203 last l env = foldExpDeepLast addCaf l (joinOuts cafLattice env l)
204 addCaf e set = case e of
205 CmmLit (CmmLabel c) -> add c set
206 CmmLit (CmmLabelOff c _) -> add c set
207 CmmLit (CmmLabelDiffOff c1 c2 _) -> add c1 $ add c2 set
209 add l s = if hasCAF l then addToFM s (cvtToClosureLbl l) () else s
211 type CafFix a = FuelMonad (BackwardFixedPoint Middle Last CAFSet a)
212 cafAnal :: LGraph Middle Last -> FuelMonad CAFEnv
213 cafAnal g = liftM zdfFpFacts (res :: CafFix ())
214 where res = zdfSolveFromL emptyBlockEnv "live CAF analysis" cafLattice
215 cafTransfers (fact_bot cafLattice) g
217 -----------------------------------------------------------------------
220 -- Description of the SRT for a given module.
221 -- Note that this SRT may grow as we greedily add new CAFs to it.
222 data TopSRT = TopSRT { lbl :: CLabel
223 , next_elt :: Int -- the next entry in the table
224 , rev_elts :: [CLabel]
225 , elt_map :: FiniteMap CLabel Int }
226 -- map: CLabel -> its last entry in the table
227 instance Outputable TopSRT where
228 ppr (TopSRT lbl next elts eltmap) =
229 text "TopSRT:" <+> ppr lbl <+> ppr next <+> ppr elts <+> ppr eltmap
231 emptySRT :: MonadUnique m => m TopSRT
233 do top_lbl <- getUniqueM >>= \ u -> return $ mkSRTLabel (mkFCallName u "srt") NoCafRefs
234 return TopSRT { lbl = top_lbl, next_elt = 0, rev_elts = [], elt_map = emptyFM }
236 cafMember :: TopSRT -> CLabel -> Bool
237 cafMember srt lbl = elemFM lbl (elt_map srt)
239 cafOffset :: TopSRT -> CLabel -> Maybe Int
240 cafOffset srt lbl = lookupFM (elt_map srt) lbl
242 addCAF :: CLabel -> TopSRT -> TopSRT
244 srt { next_elt = last + 1
245 , rev_elts = caf : rev_elts srt
246 , elt_map = addToFM (elt_map srt) caf last }
247 where last = next_elt srt
249 srtToData :: TopSRT -> CmmZ
250 srtToData srt = Cmm [CmmData RelocatableReadOnlyData (CmmDataLabel (lbl srt) : tbl)]
251 where tbl = map (CmmStaticLit . CmmLabel) (reverse (rev_elts srt))
253 -- Once we have found the CAFs, we need to do two things:
254 -- 1. Build a table of all the CAFs used in the procedure.
255 -- 2. Compute the C_SRT describing the subset of CAFs live at each procpoint.
257 -- When building the local view of the SRT, we first make sure that all the CAFs are
258 -- in the SRT. Then, if the number of CAFs is small enough to fit in a bitmap,
259 -- we make sure they're all close enough to the bottom of the table that the
260 -- bitmap will be able to cover all of them.
261 buildSRTs :: TopSRT -> FiniteMap CLabel CAFSet -> CAFSet ->
262 FuelMonad (TopSRT, Maybe CmmTopZ, C_SRT)
263 buildSRTs topSRT topCAFMap cafs =
264 do let liftCAF lbl () z = -- get CAFs for functions without static closures
265 case lookupFM topCAFMap lbl of Just cafs -> z `plusFM` cafs
266 Nothing -> addToFM z lbl ()
267 -- For each label referring to a function f without a static closure,
268 -- replace it with the CAFs that are reachable from f.
269 sub_srt topSRT localCafs =
270 let cafs = keysFM (foldFM liftCAF emptyFM localCafs)
272 do localSRTs <- procpointSRT (lbl topSRT) (elt_map topSRT) cafs
273 return (topSRT, localSRTs)
274 in if length cafs > maxBmpSize then
275 mkSRT (foldl add_if_missing topSRT cafs)
276 else -- make sure all the cafs are near the bottom of the srt
277 mkSRT (add_if_too_far topSRT cafs)
278 add_if_missing srt caf =
279 if cafMember srt caf then srt else addCAF caf srt
280 -- If a CAF is more than maxBmpSize entries from the young end of the
281 -- SRT, then we add it to the SRT again.
282 -- (Note: Not in the SRT => infinitely far.)
283 add_if_too_far srt@(TopSRT {elt_map = m}) cafs =
284 add srt (sortBy farthestFst cafs)
286 farthestFst x y = case (lookupFM m x, lookupFM m y) of
287 (Nothing, Nothing) -> EQ
288 (Nothing, Just _) -> LT
289 (Just _, Nothing) -> GT
290 (Just d, Just d') -> compare d' d
292 add srt@(TopSRT {next_elt = next}) (caf : rst) =
293 case cafOffset srt caf of
294 Just ix -> if next - ix > maxBmpSize then
295 add (addCAF caf srt) rst
297 Nothing -> add (addCAF caf srt) rst
298 (topSRT, subSRTs) <- sub_srt topSRT cafs
299 let (sub_tbls, blockSRTs) = subSRTs
300 return (topSRT, sub_tbls, blockSRTs)
302 -- Construct an SRT bitmap.
303 -- Adapted from simpleStg/SRT.lhs, which expects Id's.
304 procpointSRT :: CLabel -> FiniteMap CLabel Int -> [CLabel] ->
305 FuelMonad (Maybe CmmTopZ, C_SRT)
306 procpointSRT _ _ [] =
307 return (Nothing, NoC_SRT)
308 procpointSRT top_srt top_table entries =
309 do (top, srt) <- bitmap `seq` to_SRT top_srt offset len bitmap
312 ints = map (expectJust "constructSRT" . lookupFM top_table) entries
313 sorted_ints = sortLe (<=) ints
314 offset = head sorted_ints
315 bitmap_entries = map (subtract offset) sorted_ints
316 len = P.last bitmap_entries + 1
317 bitmap = intsToBitmap len bitmap_entries
320 maxBmpSize = widthInBits wordWidth `div` 2
322 -- Adapted from codeGen/StgCmmUtils, which converts from SRT to C_SRT.
323 to_SRT :: CLabel -> Int -> Int -> Bitmap -> FuelMonad (Maybe CmmTopZ, C_SRT)
324 to_SRT top_srt off len bmp
325 | len > maxBmpSize || bmp == [fromIntegral srt_escape]
326 = do id <- getUniqueM
327 let srt_desc_lbl = mkLargeSRTLabel id
328 tbl = CmmData RelocatableReadOnlyData $
329 CmmDataLabel srt_desc_lbl : map CmmStaticLit
330 ( cmmLabelOffW top_srt off
331 : mkWordCLit (fromIntegral len)
332 : map mkWordCLit bmp)
333 return (Just tbl, C_SRT srt_desc_lbl 0 srt_escape)
335 = return (Nothing, C_SRT top_srt off (fromIntegral (head bmp)))
336 -- The fromIntegral converts to StgHalfWord
338 -- Gather CAF info for a procedure, but only if the procedure
339 -- doesn't have a static closure.
340 -- (If it has a static closure, it will already have an SRT to
341 -- keep its CAFs live.)
342 -- Any procedure referring to a non-static CAF c must keep live
343 -- any CAF that is reachable from c.
344 localCAFInfo :: CAFEnv -> CmmTopZ -> Maybe (CLabel, CAFSet)
345 localCAFInfo _ (CmmData _ _) = Nothing
346 localCAFInfo cafEnv (CmmProc (CmmInfo _ _ infoTbl) top_l _ (_, LGraph entry _)) =
348 CmmInfoTable False _ _ _ ->
349 Just (cvtToClosureLbl top_l,
350 expectJust "maybeBindCAFs" $ lookupBlockEnv cafEnv entry)
353 -- Once we have the local CAF sets for some (possibly) mutually
354 -- recursive functions, we can create an environment mapping
355 -- each function to its set of CAFs. Note that a CAF may
356 -- be a reference to a function. If that function f does not have
357 -- a static closure, then we need to refer specifically
358 -- to the set of CAFs used by f. Of course, the set of CAFs
359 -- used by f must be included in the local CAF sets that are input to
360 -- this function. To minimize lookup time later, we return
361 -- the environment with every reference to f replaced by its set of CAFs.
362 -- To do this replacement efficiently, we gather strongly connected
363 -- components, then we sort the components in topological order.
364 mkTopCAFInfo :: [(CLabel, CAFSet)] -> FiniteMap CLabel CAFSet
365 mkTopCAFInfo localCAFs = foldl addToTop emptyFM g
366 where addToTop env (AcyclicSCC (l, cafset)) =
367 addToFM env l (flatten env cafset)
368 addToTop env (CyclicSCC nodes) =
369 let (lbls, cafsets) = unzip nodes
370 cafset = foldl plusFM emptyFM cafsets `delListFromFM` lbls
371 in foldl (\env l -> addToFM env l (flatten env cafset)) env lbls
372 flatten env cafset = foldFM (lookup env) emptyFM cafset
373 lookup env caf () cafset' =
374 case lookupFM env caf of Just cafs -> foldFM add cafset' cafs
375 Nothing -> add caf () cafset'
376 add caf () cafset' = addToFM cafset' caf ()
377 g = stronglyConnCompFromEdgedVertices
378 (map (\n@(l, cafs) -> (n, l, keysFM cafs)) localCAFs)
380 type StackLayout = [Maybe LocalReg]
382 -- Bundle the CAFs used at a procpoint.
383 bundleCAFs :: CAFEnv -> CmmTopForInfoTables -> (CAFSet, CmmTopForInfoTables)
384 bundleCAFs cafEnv t@(ProcInfoTable _ procpoints) =
385 case blockSetToList procpoints of
386 [bid] -> (expectJust "bundleCAFs" (lookupBlockEnv cafEnv bid), t)
387 _ -> panic "setInfoTableStackMap: unexpect number of procpoints"
388 -- until we stop splitting the graphs at procpoints in the native path
389 bundleCAFs cafEnv t@(FloatingInfoTable _ bid _) =
390 (expectJust "bundleCAFs " (lookupBlockEnv cafEnv bid), t)
391 bundleCAFs _ t@(NoInfoTable _) = (emptyFM, t)
393 -- Construct the SRTs for the given procedure.
394 setInfoTableSRT :: FiniteMap CLabel CAFSet -> TopSRT -> (CAFSet, CmmTopForInfoTables) ->
395 FuelMonad (TopSRT, [CmmTopForInfoTables])
396 setInfoTableSRT topCAFMap topSRT (cafs, t@(ProcInfoTable _ procpoints)) =
397 case blockSetToList procpoints of
398 [_] -> setSRT cafs topCAFMap topSRT t
399 _ -> panic "setInfoTableStackMap: unexpect number of procpoints"
400 -- until we stop splitting the graphs at procpoints in the native path
401 setInfoTableSRT topCAFMap topSRT (cafs, t@(FloatingInfoTable _ _ _)) =
402 setSRT cafs topCAFMap topSRT t
403 setInfoTableSRT _ topSRT (_, t@(NoInfoTable _)) = return (topSRT, [t])
405 setSRT :: CAFSet -> FiniteMap CLabel CAFSet -> TopSRT ->
406 CmmTopForInfoTables -> FuelMonad (TopSRT, [CmmTopForInfoTables])
407 setSRT cafs topCAFMap topSRT t =
408 do (topSRT, cafTable, srt) <- buildSRTs topSRT topCAFMap cafs
409 let t' = updInfo id (const srt) t
411 Just tbl -> return (topSRT, [t', NoInfoTable tbl])
412 Nothing -> return (topSRT, [t'])
414 updInfo :: (StackLayout -> StackLayout) -> (C_SRT -> C_SRT) ->
415 CmmTopForInfoTables -> CmmTopForInfoTables
416 updInfo toVars toSrt (ProcInfoTable (CmmProc info top_l top_args g) procpoints) =
417 ProcInfoTable (CmmProc (updInfoTbl toVars toSrt info) top_l top_args g) procpoints
418 updInfo toVars toSrt (FloatingInfoTable info bid updfr_off) =
419 FloatingInfoTable (updInfoTbl toVars toSrt info) bid updfr_off
420 updInfo _ _ (NoInfoTable _) = panic "can't update NoInfoTable"
421 updInfo _ _ _ = panic "unexpected arg to updInfo"
423 updInfoTbl :: (StackLayout -> StackLayout) -> (C_SRT -> C_SRT) -> CmmInfo -> CmmInfo
424 updInfoTbl toVars toSrt (CmmInfo gc upd_fr (CmmInfoTable s p t typeinfo))
425 = CmmInfo gc upd_fr (CmmInfoTable s p t typeinfo')
426 where typeinfo' = case typeinfo of
427 t@(ConstrInfo _ _ _) -> t
428 (FunInfo c s a d e) -> FunInfo c (toSrt s) a d e
429 (ThunkInfo c s) -> ThunkInfo c (toSrt s)
430 (ThunkSelectorInfo x s) -> ThunkSelectorInfo x (toSrt s)
431 (ContInfo v s) -> ContInfo (toVars v) (toSrt s)
432 updInfoTbl _ _ t@(CmmInfo _ _ CmmNonInfoTable) = t
434 -- Lower the CmmTopForInfoTables type down to good old CmmTopZ
435 -- by emitting info tables as data where necessary.
436 finishInfoTables :: CmmTopForInfoTables -> IO [CmmTopZ]
437 finishInfoTables (NoInfoTable t) = return [t]
438 finishInfoTables (ProcInfoTable p _) = return [p]
439 finishInfoTables (FloatingInfoTable (CmmInfo _ _ infotbl) bid _) =
440 do uniq_supply <- mkSplitUniqSupply 'i'
441 return $ mkBareInfoTable (retPtLbl bid) (uniqFromSupply uniq_supply) infotbl
443 ----------------------------------------------------------------
444 -- Safe foreign calls:
445 -- Our analyses capture the dataflow facts at block boundaries, but we need
446 -- to extend the CAF and live-slot analyses to safe foreign calls as well,
447 -- which show up as middle nodes.
448 extendEnvWithSafeForeignCalls ::
449 BackwardTransfers Middle Last a -> BlockEnv a -> CmmGraph -> BlockEnv a
450 extendEnvWithSafeForeignCalls transfers env g = fold_blocks block env g
452 tail (bt_last_in transfers l (lookup env)) z head
453 where (head, last) = goto_end (G.unzip b)
454 l = case last of LastOther l -> l
455 LastExit -> panic "extendEnvs lastExit"
456 tail _ z (ZFirst _) = z
457 tail fact env (ZHead h m@(MidForeignCall (Safe bid _) _ _ _)) =
458 tail (mid m fact) (extendBlockEnv env bid fact) h
459 tail fact env (ZHead h m) = tail (mid m fact) env h
460 lookup map k = expectJust "extendEnvWithSafeFCalls" $ lookupBlockEnv map k
461 mid = bt_middle_in transfers
464 extendEnvsForSafeForeignCalls :: CAFEnv -> SlotEnv -> CmmGraph -> (CAFEnv, SlotEnv)
465 extendEnvsForSafeForeignCalls cafEnv slotEnv g =
466 fold_blocks block (cafEnv, slotEnv) g
468 tail ( bt_last_in cafTransfers l (lookupFn cafEnv)
469 , bt_last_in liveSlotTransfers l (lookupFn slotEnv))
471 where (head, last) = goto_end (G.unzip b)
472 l = case last of LastOther l -> l
473 LastExit -> panic "extendEnvs lastExit"
474 tail _ z (ZFirst _) = z
475 tail lives@(cafs, slots) (cafEnv, slotEnv)
476 (ZHead h m@(MidForeignCall (Safe bid _) _ _ _)) =
477 let slots' = removeLiveSlotDefs slots m
478 slotEnv' = extendBlockEnv slotEnv bid slots'
479 cafEnv' = extendBlockEnv cafEnv bid cafs
480 in tail (upd lives m) (cafEnv', slotEnv') h
481 tail lives z (ZHead h m) = tail (upd lives m) z h
482 lookupFn map k = expectJust "extendEnvsForSafeFCalls" $ lookupBlockEnv map k
483 upd (cafs, slots) m =
484 (bt_middle_in cafTransfers m cafs, bt_middle_in liveSlotTransfers m slots)
486 -- Safe foreign calls: We need to insert the code that suspends and resumes
487 -- the thread before and after a safe foreign call.
488 -- Why do we do this so late in the pipeline?
489 -- Because we need this code to appear without interrruption: you can't rely on the
490 -- value of the stack pointer between the call and resetting the thread state;
491 -- you need to have an infotable on the young end of the stack both when
492 -- suspending the thread and making the foreign call.
493 -- All of this is much easier if we insert the suspend and resume calls here.
495 -- At the same time, we prepare for the stages of the compiler that
496 -- build the proc points. We have to do this at the same time because
497 -- the safe foreign calls need special treatment with respect to infotables.
498 -- A safe foreign call needs an infotable even though it isn't
499 -- a procpoint. The following datatype captures the information
500 -- needed to generate the infotables along with the Cmm data and procedures.
502 data CmmTopForInfoTables
503 = NoInfoTable CmmTopZ -- must be CmmData
504 | ProcInfoTable CmmTopZ BlockSet -- CmmProc; argument is its set of procpoints
505 | FloatingInfoTable CmmInfo BlockId UpdFrameOffset
506 instance Outputable CmmTopForInfoTables where
507 ppr (NoInfoTable t) = text "NoInfoTable: " <+> ppr t
508 ppr (ProcInfoTable t bids) = text "ProcInfoTable: " <+> ppr t <+> ppr bids
509 ppr (FloatingInfoTable info bid upd) =
510 text "FloatingInfoTable: " <+> ppr info <+> ppr bid <+> ppr upd
512 -- The `safeState' record collects the info we update while lowering the
513 -- safe foreign calls in the graph.
514 data SafeState = State { s_blocks :: BlockEnv CmmBlock
515 , s_pps :: ProcPointSet
516 , s_safeCalls :: [CmmTopForInfoTables]}
518 lowerSafeForeignCalls
519 :: [[CmmTopForInfoTables]] -> CmmTopZ -> FuelMonad [[CmmTopForInfoTables]]
520 lowerSafeForeignCalls rst t@(CmmData _ _) = return $ [NoInfoTable t] : rst
521 lowerSafeForeignCalls rst (CmmProc info l args (off, g@(LGraph entry _))) = do
522 let init = return $ State emptyBlockEnv emptyBlockSet []
523 let block b@(Block bid _) z = do
524 state@(State {s_pps = ppset, s_blocks = blocks}) <- z
525 let ppset' = if bid == entry then extendBlockSet ppset bid else ppset
526 state' = state { s_pps = ppset' }
527 if hasSafeForeignCall b
528 then lowerSafeCallBlock state' b
529 else return (state' { s_blocks = insertBlock b blocks })
530 State blocks' g_procpoints safeCalls <- fold_blocks block init g
531 let proc = (CmmProc info l args (off, LGraph entry blocks'))
532 procTable = case off of
533 (_, Just _) -> [ProcInfoTable proc g_procpoints]
534 _ -> [NoInfoTable proc] -- not a successor of a call
535 return $ safeCalls : procTable : rst
537 -- Check for foreign calls -- if none, then we can avoid copying the block.
538 hasSafeForeignCall :: CmmBlock -> Bool
539 hasSafeForeignCall (Block _ t) = tail t
540 where tail (ZTail (MidForeignCall (Safe _ _) _ _ _) _) = True
541 tail (ZTail _ t) = tail t
542 tail (ZLast _) = False
544 -- Lower each safe call in the block, update the CAF and slot environments
545 -- to include each of those calls, and insert the new block in the blockEnv.
546 lowerSafeCallBlock :: SafeState-> CmmBlock -> FuelMonad SafeState
547 lowerSafeCallBlock state b = tail (return state) (ZBlock head (ZLast last))
548 where (head, last) = goto_end (G.unzip b)
549 tail s b@(ZBlock (ZFirst _) _) =
551 return $ state { s_blocks = insertBlock (G.zip b) (s_blocks state) }
552 tail s (ZBlock (ZHead h m@(MidForeignCall (Safe bid updfr_off) _ _ _)) t) =
555 { s_safeCalls = FloatingInfoTable emptyContInfoTable bid updfr_off :
557 (state'', t') <- lowerSafeForeignCall state' m t
558 tail (return state'') (ZBlock h t')
559 tail s (ZBlock (ZHead h m) t) = tail s (ZBlock h (ZTail m t))
562 -- Late in the code generator, we want to insert the code necessary
563 -- to lower a safe foreign call to a sequence of unsafe calls.
564 lowerSafeForeignCall ::
565 SafeState -> Middle -> ZTail Middle Last -> FuelMonad (SafeState, ZTail Middle Last)
566 lowerSafeForeignCall state m@(MidForeignCall (Safe infotable _) _ _ _) tail = do
567 let newTemp rep = getUniqueM >>= \u -> return (LocalReg u rep)
568 -- Both 'id' and 'new_base' are KindNonPtr because they're
569 -- RTS-only objects and are not subject to garbage collection
571 new_base <- newTemp (cmmRegType (CmmGlobal BaseReg))
572 let (caller_save, caller_load) = callerSaveVolatileRegs
573 load_tso <- newTemp gcWord -- TODO FIXME NOW
574 let suspendThread = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "suspendThread")))
575 resumeThread = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "resumeThread")))
576 suspend = mkStore (CmmReg spReg) (CmmLit (CmmBlock infotable)) <*>
579 mkUnsafeCall (ForeignTarget suspendThread
580 (ForeignConvention CCallConv [AddrHint] [AddrHint]))
581 [id] [CmmReg (CmmGlobal BaseReg)]
582 resume = mkUnsafeCall (ForeignTarget resumeThread
583 (ForeignConvention CCallConv [AddrHint] [AddrHint]))
584 [new_base] [CmmReg (CmmLocal id)] <*>
585 -- Assign the result to BaseReg: we
586 -- might now have a different Capability!
587 mkAssign (CmmGlobal BaseReg) (CmmReg (CmmLocal new_base)) <*>
589 loadThreadState load_tso
590 Graph tail' blocks' <-
591 liftUniq (graphOfAGraph (suspend <*> mkMiddle m <*> resume <*> mkZTail tail))
592 return (state {s_blocks = s_blocks state `plusBlockEnv` blocks'}, tail')
593 lowerSafeForeignCall _ _ _ = panic "lowerSafeForeignCall was passed something else"