1 module CmmBuildInfoTables
2 ( CAFSet, CAFEnv, CmmTopForInfoTables(..), cafAnal, localCAFInfo, mkTopCAFInfo
3 , setInfoTableSRT, setInfoTableStackMap
4 , TopSRT, emptySRT, srtToData
6 , finishInfoTables, lowerSafeForeignCalls
7 , cafTransfers, liveSlotTransfers
8 , extendEnvWithSafeForeignCalls, extendEnvsForSafeForeignCalls )
11 #include "HsVersions.h"
15 import qualified Prelude as P
22 import Cmm hiding (blockId)
36 import MkZipCfgCmm hiding (CmmAGraph, CmmBlock, CmmTopZ, CmmZ, CmmGraph)
46 import ZipCfg hiding (zip, unzip, last)
47 import qualified ZipCfg as G
51 ----------------------------------------------------------------
52 -- Building InfoTables
55 -----------------------------------------------------------------------
58 -- Given a block ID, we return a representation of the layout of the stack,
59 -- as suspended before entering that block.
60 -- (For a return site to a function call, the layout does not include the
61 -- parameter passing area (or the "return address" on the stack)).
62 -- If the element is `Nothing`, then it represents a word of the stack that
63 -- does not contain a live pointer.
64 -- If the element is `Just` a register, then it represents a live spill slot
65 -- for a pointer; we assume that a pointer is the size of a word.
66 -- The head of the list represents the young end of the stack where the infotable
67 -- pointer for the block `Bid` is stored.
68 -- The infotable pointer itself is not included in the list.
69 -- Call areas are also excluded from the list: besides the stuff in the update
70 -- frame (and the return infotable), call areas should never be live across
73 -- RTS Invariant: All pointers must be word-aligned because each bit in the bitmap
74 -- represents a word. Consequently, we have to be careful when we see a live slot
75 -- on the stack: if we have packed multiple sub-word values into a word,
76 -- we have to make sure that we only mark the entire word as a non-pointer.
78 -- Also, don't forget to stop at the old end of the stack (oldByte),
79 -- which may differ depending on whether there is an update frame.
82 = ( Int -- Offset from oldest byte of Old area
83 , LocalReg -- The register
84 , Int) -- Width of the register
86 live_ptrs :: ByteOff -> BlockEnv SubAreaSet -> AreaMap -> BlockId -> [Maybe LocalReg]
87 live_ptrs oldByte slotEnv areaMap bid =
88 -- pprTrace "live_ptrs for" (ppr bid <+> text (show oldByte ++ "-" ++ show youngByte) <+>
90 -- pprTrace ("stack layout for " ++ show bid ++ ": ") (ppr res) $ res
92 where res = reverse $ slotsToList youngByte liveSlots []
94 slotsToList :: Int -> [RegSlotInfo] -> [Maybe LocalReg] -> [Maybe LocalReg]
95 -- n starts at youngByte and is decremented down to oldByte
96 -- Returns a list, one element per word, with
97 -- (Just r) meaning 'pointer register r is saved here',
98 -- Nothing meaning 'non-pointer or empty'
100 slotsToList n [] results | n == oldByte = results -- at old end of stack frame
102 slotsToList n (s : _) _ | n == oldByte =
103 pprPanic "slot left off live_ptrs" (ppr s <+> ppr oldByte <+>
104 ppr n <+> ppr liveSlots <+> ppr youngByte)
106 slotsToList n _ _ | n < oldByte =
107 panic "stack slots not allocated on word boundaries?"
109 slotsToList n l@((n', r, w) : rst) results =
110 if n == (n' + w) then -- slot's young byte is at n
111 ASSERT (not (isPtr r) ||
112 (n `mod` wORD_SIZE == 0 && w == wORD_SIZE)) -- ptrs must be aligned
113 slotsToList next (dropWhile (non_ptr_younger_than next) rst)
114 (stack_rep : results)
115 else slotsToList next (dropWhile (non_ptr_younger_than next) l)
117 where next = n - wORD_SIZE
118 stack_rep = if isPtr r then Just r else Nothing
120 slotsToList n [] results = slotsToList (n - wORD_SIZE) [] (Nothing : results)
122 non_ptr_younger_than next (n', r, w) =
124 ASSERT (not (isPtr r))
126 isPtr = isGcPtrType . localRegType
128 liveSlots :: [RegSlotInfo]
129 liveSlots = sortBy (\ (off,_,_) (off',_,_) -> compare off' off)
130 (foldFM (\_ -> flip $ foldl add_slot) [] slots)
132 add_slot :: [RegSlotInfo] -> SubArea -> [RegSlotInfo]
133 add_slot rst (a@(RegSlot r@(LocalReg _ ty)), off, w) =
134 if off == w && widthInBytes (typeWidth ty) == w then
135 (expectJust "add_slot" (lookupFM areaMap a), r, w) : rst
136 else panic "live_ptrs: only part of a variable live at a proc point"
137 add_slot rst (CallArea Old, _, _) =
138 rst -- the update frame (or return infotable) should be live
139 -- would be nice to check that only that part of the callarea is live...
140 add_slot rst ((CallArea _), _, _) =
142 -- JD: THIS ISN'T CURRENTLY A CORRECTNESS PROBLEM, BUT WE SHOULD REALLY
143 -- MAKE LIVENESS INFO AROUND CALLS MORE PRECISE -- FOR NOW, A 32-BIT
144 -- FLOAT PADS OUT TO 64 BITS, BUT WE ASSUME THE WHOLE PARAMETER-PASSING
145 -- AREA IS LIVE (WHICH IT ISN'T...). WE SHOULD JUST PUT THE LIVE AREAS
146 -- IN THE CALL NODES, WHICH SHOULD EVENTUALLY HAVE LIVE REGISTER AS WELL,
147 -- SO IT'S ALL GOING IN THE SAME DIRECTION.
148 -- pprPanic "CallAreas must not be live across function calls" (ppr bid <+> ppr c)
150 slots :: SubAreaSet -- The SubAreaSet for 'bid'
151 slots = expectJust "live_ptrs slots" $ lookupBlockEnv slotEnv bid
152 youngByte = expectJust "live_ptrs bid_pos" $ lookupFM areaMap (CallArea (Young bid))
154 -- Construct the stack maps for the given procedure.
155 setInfoTableStackMap :: SlotEnv -> AreaMap -> CmmTopForInfoTables -> CmmTopForInfoTables
156 setInfoTableStackMap _ _ t@(NoInfoTable _) = t
157 setInfoTableStackMap slotEnv areaMap t@(FloatingInfoTable _ bid updfr_off) =
158 updInfo (const (live_ptrs updfr_off slotEnv areaMap bid)) id t
159 setInfoTableStackMap slotEnv areaMap
160 t@(ProcInfoTable (CmmProc (CmmInfo _ _ _) _ _ ((_, Just updfr_off), _)) procpoints) =
161 case blockSetToList procpoints of
162 [bid] -> updInfo (const (live_ptrs updfr_off slotEnv areaMap bid)) id t
163 _ -> panic "setInfoTableStackMap: unexpected number of procpoints"
164 -- until we stop splitting the graphs at procpoints in the native path
165 setInfoTableStackMap _ _ t = pprPanic "unexpected case for setInfoTableStackMap" (ppr t)
169 -----------------------------------------------------------------------
172 -- WE NEED AN EXAMPLE HERE.
173 -- IN PARTICULAR, WE NEED TO POINT OUT THE DISTINCTION BETWEEN
174 -- FUNCTIONS WITH STATIC CLOSURES AND THOSE THAT MUST BE CONSTRUCTED
175 -- DYNAMICALLY (AND HENCE CAN'T BE REFERENCED IN AN SRT).
176 -- IN THE LATTER CASE, WE HAVE TO TAKE ALL THE CAFs REFERENCED BY
177 -- THE CLOSURE AND INLINE THEM INTO ANY SRT THAT MAY MENTION THE CLOSURE.
178 -- (I.E. TAKE THE TRANSITIVE CLOSURE, but only for non-static closures).
181 -----------------------------------------------------------------------
182 -- Finding the CAFs used by a procedure
184 type CAFSet = FiniteMap CLabel ()
185 type CAFEnv = BlockEnv CAFSet
187 -- First, an analysis to find live CAFs.
188 cafLattice :: DataflowLattice CAFSet
189 cafLattice = DataflowLattice "live cafs" emptyFM add False
190 where add new old = if sizeFM new' > sizeFM old then aTx new' else noTx new'
191 where new' = new `plusFM` old
193 cafTransfers :: BackwardTransfers Middle Last CAFSet
194 cafTransfers = BackwardTransfers first middle last
195 where first _ live = live
196 middle m live = foldExpDeepMiddle addCaf m live
197 last l env = foldExpDeepLast addCaf l (joinOuts cafLattice env l)
198 addCaf e set = case e of
199 CmmLit (CmmLabel c) -> add c set
200 CmmLit (CmmLabelOff c _) -> add c set
201 CmmLit (CmmLabelDiffOff c1 c2 _) -> add c1 $ add c2 set
203 add l s = if hasCAF l then addToFM s (cvtToClosureLbl l) () else s
205 type CafFix a = FuelMonad (BackwardFixedPoint Middle Last CAFSet a)
206 cafAnal :: LGraph Middle Last -> FuelMonad CAFEnv
207 cafAnal g = liftM zdfFpFacts (res :: CafFix ())
208 where res = zdfSolveFromL emptyBlockEnv "live CAF analysis" cafLattice
209 cafTransfers (fact_bot cafLattice) g
211 -----------------------------------------------------------------------
214 -- Description of the SRT for a given module.
215 -- Note that this SRT may grow as we greedily add new CAFs to it.
216 data TopSRT = TopSRT { lbl :: CLabel
217 , next_elt :: Int -- the next entry in the table
218 , rev_elts :: [CLabel]
219 , elt_map :: FiniteMap CLabel Int }
220 -- map: CLabel -> its last entry in the table
221 instance Outputable TopSRT where
222 ppr (TopSRT lbl next elts eltmap) =
223 text "TopSRT:" <+> ppr lbl <+> ppr next <+> ppr elts <+> ppr eltmap
225 emptySRT :: MonadUnique m => m TopSRT
227 do top_lbl <- getUniqueM >>= \ u -> return $ mkSRTLabel (mkFCallName u "srt") NoCafRefs
228 return TopSRT { lbl = top_lbl, next_elt = 0, rev_elts = [], elt_map = emptyFM }
230 cafMember :: TopSRT -> CLabel -> Bool
231 cafMember srt lbl = elemFM lbl (elt_map srt)
233 cafOffset :: TopSRT -> CLabel -> Maybe Int
234 cafOffset srt lbl = lookupFM (elt_map srt) lbl
236 addCAF :: CLabel -> TopSRT -> TopSRT
238 srt { next_elt = last + 1
239 , rev_elts = caf : rev_elts srt
240 , elt_map = addToFM (elt_map srt) caf last }
241 where last = next_elt srt
243 srtToData :: TopSRT -> CmmZ
244 srtToData srt = Cmm [CmmData RelocatableReadOnlyData (CmmDataLabel (lbl srt) : tbl)]
245 where tbl = map (CmmStaticLit . CmmLabel) (reverse (rev_elts srt))
247 -- Once we have found the CAFs, we need to do two things:
248 -- 1. Build a table of all the CAFs used in the procedure.
249 -- 2. Compute the C_SRT describing the subset of CAFs live at each procpoint.
251 -- When building the local view of the SRT, we first make sure that all the CAFs are
252 -- in the SRT. Then, if the number of CAFs is small enough to fit in a bitmap,
253 -- we make sure they're all close enough to the bottom of the table that the
254 -- bitmap will be able to cover all of them.
255 buildSRTs :: TopSRT -> FiniteMap CLabel CAFSet -> CAFSet ->
256 FuelMonad (TopSRT, Maybe CmmTopZ, C_SRT)
257 buildSRTs topSRT topCAFMap cafs =
258 do let liftCAF lbl () z = -- get CAFs for functions without static closures
259 case lookupFM topCAFMap lbl of Just cafs -> z `plusFM` cafs
260 Nothing -> addToFM z lbl ()
261 -- For each label referring to a function f without a static closure,
262 -- replace it with the CAFs that are reachable from f.
263 sub_srt topSRT localCafs =
264 let cafs = keysFM (foldFM liftCAF emptyFM localCafs)
266 do localSRTs <- procpointSRT (lbl topSRT) (elt_map topSRT) cafs
267 return (topSRT, localSRTs)
268 in if length cafs > maxBmpSize then
269 mkSRT (foldl add_if_missing topSRT cafs)
270 else -- make sure all the cafs are near the bottom of the srt
271 mkSRT (add_if_too_far topSRT cafs)
272 add_if_missing srt caf =
273 if cafMember srt caf then srt else addCAF caf srt
274 -- If a CAF is more than maxBmpSize entries from the young end of the
275 -- SRT, then we add it to the SRT again.
276 -- (Note: Not in the SRT => infinitely far.)
277 add_if_too_far srt@(TopSRT {elt_map = m}) cafs =
278 add srt (sortBy farthestFst cafs)
280 farthestFst x y = case (lookupFM m x, lookupFM m y) of
281 (Nothing, Nothing) -> EQ
282 (Nothing, Just _) -> LT
283 (Just _, Nothing) -> GT
284 (Just d, Just d') -> compare d' d
286 add srt@(TopSRT {next_elt = next}) (caf : rst) =
287 case cafOffset srt caf of
288 Just ix -> if next - ix > maxBmpSize then
289 add (addCAF caf srt) rst
291 Nothing -> add (addCAF caf srt) rst
292 (topSRT, subSRTs) <- sub_srt topSRT cafs
293 let (sub_tbls, blockSRTs) = subSRTs
294 return (topSRT, sub_tbls, blockSRTs)
296 -- Construct an SRT bitmap.
297 -- Adapted from simpleStg/SRT.lhs, which expects Id's.
298 procpointSRT :: CLabel -> FiniteMap CLabel Int -> [CLabel] ->
299 FuelMonad (Maybe CmmTopZ, C_SRT)
300 procpointSRT _ _ [] =
301 return (Nothing, NoC_SRT)
302 procpointSRT top_srt top_table entries =
303 do (top, srt) <- bitmap `seq` to_SRT top_srt offset len bitmap
306 ints = map (expectJust "constructSRT" . lookupFM top_table) entries
307 sorted_ints = sortLe (<=) ints
308 offset = head sorted_ints
309 bitmap_entries = map (subtract offset) sorted_ints
310 len = P.last bitmap_entries + 1
311 bitmap = intsToBitmap len bitmap_entries
314 maxBmpSize = widthInBits wordWidth `div` 2
316 -- Adapted from codeGen/StgCmmUtils, which converts from SRT to C_SRT.
317 to_SRT :: CLabel -> Int -> Int -> Bitmap -> FuelMonad (Maybe CmmTopZ, C_SRT)
318 to_SRT top_srt off len bmp
319 | len > maxBmpSize || bmp == [fromIntegral srt_escape]
320 = do id <- getUniqueM
321 let srt_desc_lbl = mkLargeSRTLabel id
322 tbl = CmmData RelocatableReadOnlyData $
323 CmmDataLabel srt_desc_lbl : map CmmStaticLit
324 ( cmmLabelOffW top_srt off
325 : mkWordCLit (fromIntegral len)
326 : map mkWordCLit bmp)
327 return (Just tbl, C_SRT srt_desc_lbl 0 srt_escape)
329 = return (Nothing, C_SRT top_srt off (fromIntegral (head bmp)))
330 -- The fromIntegral converts to StgHalfWord
332 -- Gather CAF info for a procedure, but only if the procedure
333 -- doesn't have a static closure.
334 -- (If it has a static closure, it will already have an SRT to
335 -- keep its CAFs live.)
336 -- Any procedure referring to a non-static CAF c must keep live
337 -- any CAF that is reachable from c.
338 localCAFInfo :: CAFEnv -> CmmTopZ -> Maybe (CLabel, CAFSet)
339 localCAFInfo _ (CmmData _ _) = Nothing
340 localCAFInfo cafEnv (CmmProc (CmmInfo _ _ infoTbl) top_l _ (_, LGraph entry _)) =
342 CmmInfoTable False _ _ _ ->
343 Just (cvtToClosureLbl top_l,
344 expectJust "maybeBindCAFs" $ lookupBlockEnv cafEnv entry)
347 -- Once we have the local CAF sets for some (possibly) mutually
348 -- recursive functions, we can create an environment mapping
349 -- each function to its set of CAFs. Note that a CAF may
350 -- be a reference to a function. If that function f does not have
351 -- a static closure, then we need to refer specifically
352 -- to the set of CAFs used by f. Of course, the set of CAFs
353 -- used by f must be included in the local CAF sets that are input to
354 -- this function. To minimize lookup time later, we return
355 -- the environment with every reference to f replaced by its set of CAFs.
356 -- To do this replacement efficiently, we gather strongly connected
357 -- components, then we sort the components in topological order.
358 mkTopCAFInfo :: [(CLabel, CAFSet)] -> FiniteMap CLabel CAFSet
359 mkTopCAFInfo localCAFs = foldl addToTop emptyFM g
360 where addToTop env (AcyclicSCC (l, cafset)) =
361 addToFM env l (flatten env cafset)
362 addToTop env (CyclicSCC nodes) =
363 let (lbls, cafsets) = unzip nodes
364 cafset = foldl plusFM emptyFM cafsets `delListFromFM` lbls
365 in foldl (\env l -> addToFM env l (flatten env cafset)) env lbls
366 flatten env cafset = foldFM (lookup env) emptyFM cafset
367 lookup env caf () cafset' =
368 case lookupFM env caf of Just cafs -> foldFM add cafset' cafs
369 Nothing -> add caf () cafset'
370 add caf () cafset' = addToFM cafset' caf ()
371 g = stronglyConnCompFromEdgedVertices
372 (map (\n@(l, cafs) -> (n, l, keysFM cafs)) localCAFs)
374 type StackLayout = [Maybe LocalReg]
376 -- Bundle the CAFs used at a procpoint.
377 bundleCAFs :: CAFEnv -> CmmTopForInfoTables -> (CAFSet, CmmTopForInfoTables)
378 bundleCAFs cafEnv t@(ProcInfoTable _ procpoints) =
379 case blockSetToList procpoints of
380 [bid] -> (expectJust "bundleCAFs" (lookupBlockEnv cafEnv bid), t)
381 _ -> panic "setInfoTableStackMap: unexpect number of procpoints"
382 -- until we stop splitting the graphs at procpoints in the native path
383 bundleCAFs cafEnv t@(FloatingInfoTable _ bid _) =
384 (expectJust "bundleCAFs " (lookupBlockEnv cafEnv bid), t)
385 bundleCAFs _ t@(NoInfoTable _) = (emptyFM, t)
387 -- Construct the SRTs for the given procedure.
388 setInfoTableSRT :: FiniteMap CLabel CAFSet -> TopSRT -> (CAFSet, CmmTopForInfoTables) ->
389 FuelMonad (TopSRT, [CmmTopForInfoTables])
390 setInfoTableSRT topCAFMap topSRT (cafs, t@(ProcInfoTable _ procpoints)) =
391 case blockSetToList procpoints of
392 [_] -> setSRT cafs topCAFMap topSRT t
393 _ -> panic "setInfoTableStackMap: unexpect number of procpoints"
394 -- until we stop splitting the graphs at procpoints in the native path
395 setInfoTableSRT topCAFMap topSRT (cafs, t@(FloatingInfoTable _ _ _)) =
396 setSRT cafs topCAFMap topSRT t
397 setInfoTableSRT _ topSRT (_, t@(NoInfoTable _)) = return (topSRT, [t])
399 setSRT :: CAFSet -> FiniteMap CLabel CAFSet -> TopSRT ->
400 CmmTopForInfoTables -> FuelMonad (TopSRT, [CmmTopForInfoTables])
401 setSRT cafs topCAFMap topSRT t =
402 do (topSRT, cafTable, srt) <- buildSRTs topSRT topCAFMap cafs
403 let t' = updInfo id (const srt) t
405 Just tbl -> return (topSRT, [t', NoInfoTable tbl])
406 Nothing -> return (topSRT, [t'])
408 updInfo :: (StackLayout -> StackLayout) -> (C_SRT -> C_SRT) ->
409 CmmTopForInfoTables -> CmmTopForInfoTables
410 updInfo toVars toSrt (ProcInfoTable (CmmProc info top_l top_args g) procpoints) =
411 ProcInfoTable (CmmProc (updInfoTbl toVars toSrt info) top_l top_args g) procpoints
412 updInfo toVars toSrt (FloatingInfoTable info bid updfr_off) =
413 FloatingInfoTable (updInfoTbl toVars toSrt info) bid updfr_off
414 updInfo _ _ (NoInfoTable _) = panic "can't update NoInfoTable"
415 updInfo _ _ _ = panic "unexpected arg to updInfo"
417 updInfoTbl :: (StackLayout -> StackLayout) -> (C_SRT -> C_SRT) -> CmmInfo -> CmmInfo
418 updInfoTbl toVars toSrt (CmmInfo gc upd_fr (CmmInfoTable s p t typeinfo))
419 = CmmInfo gc upd_fr (CmmInfoTable s p t typeinfo')
420 where typeinfo' = case typeinfo of
421 t@(ConstrInfo _ _ _) -> t
422 (FunInfo c s a d e) -> FunInfo c (toSrt s) a d e
423 (ThunkInfo c s) -> ThunkInfo c (toSrt s)
424 (ThunkSelectorInfo x s) -> ThunkSelectorInfo x (toSrt s)
425 (ContInfo v s) -> ContInfo (toVars v) (toSrt s)
426 updInfoTbl _ _ t@(CmmInfo _ _ CmmNonInfoTable) = t
428 -- Lower the CmmTopForInfoTables type down to good old CmmTopZ
429 -- by emitting info tables as data where necessary.
430 finishInfoTables :: CmmTopForInfoTables -> IO [CmmTopZ]
431 finishInfoTables (NoInfoTable t) = return [t]
432 finishInfoTables (ProcInfoTable p _) = return [p]
433 finishInfoTables (FloatingInfoTable (CmmInfo _ _ infotbl) bid _) =
434 do uniq_supply <- mkSplitUniqSupply 'i'
435 return $ mkBareInfoTable (retPtLbl bid) (uniqFromSupply uniq_supply) infotbl
437 ----------------------------------------------------------------
438 -- Safe foreign calls:
439 -- Our analyses capture the dataflow facts at block boundaries, but we need
440 -- to extend the CAF and live-slot analyses to safe foreign calls as well,
441 -- which show up as middle nodes.
442 extendEnvWithSafeForeignCalls ::
443 BackwardTransfers Middle Last a -> BlockEnv a -> CmmGraph -> BlockEnv a
444 extendEnvWithSafeForeignCalls transfers env g = fold_blocks block env g
446 tail (bt_last_in transfers l (lookup env)) z head
447 where (head, last) = goto_end (G.unzip b)
448 l = case last of LastOther l -> l
449 LastExit -> panic "extendEnvs lastExit"
450 tail _ z (ZFirst _) = z
451 tail fact env (ZHead h m@(MidForeignCall (Safe bid _) _ _ _)) =
452 tail (mid m fact) (extendBlockEnv env bid fact) h
453 tail fact env (ZHead h m) = tail (mid m fact) env h
454 lookup map k = expectJust "extendEnvWithSafeFCalls" $ lookupBlockEnv map k
455 mid = bt_middle_in transfers
458 extendEnvsForSafeForeignCalls :: CAFEnv -> SlotEnv -> CmmGraph -> (CAFEnv, SlotEnv)
459 extendEnvsForSafeForeignCalls cafEnv slotEnv g =
460 fold_blocks block (cafEnv, slotEnv) g
462 tail ( bt_last_in cafTransfers l (lookupFn cafEnv)
463 , bt_last_in liveSlotTransfers l (lookupFn slotEnv))
465 where (head, last) = goto_end (G.unzip b)
466 l = case last of LastOther l -> l
467 LastExit -> panic "extendEnvs lastExit"
468 tail _ z (ZFirst _) = z
469 tail lives@(cafs, slots) (cafEnv, slotEnv)
470 (ZHead h m@(MidForeignCall (Safe bid _) _ _ _)) =
471 let slots' = removeLiveSlotDefs slots m
472 slotEnv' = extendBlockEnv slotEnv bid slots'
473 cafEnv' = extendBlockEnv cafEnv bid cafs
474 in tail (upd lives m) (cafEnv', slotEnv') h
475 tail lives z (ZHead h m) = tail (upd lives m) z h
476 lookupFn map k = expectJust "extendEnvsForSafeFCalls" $ lookupBlockEnv map k
477 upd (cafs, slots) m =
478 (bt_middle_in cafTransfers m cafs, bt_middle_in liveSlotTransfers m slots)
480 -- Safe foreign calls: We need to insert the code that suspends and resumes
481 -- the thread before and after a safe foreign call.
482 -- Why do we do this so late in the pipeline?
483 -- Because we need this code to appear without interrruption: you can't rely on the
484 -- value of the stack pointer between the call and resetting the thread state;
485 -- you need to have an infotable on the young end of the stack both when
486 -- suspending the thread and making the foreign call.
487 -- All of this is much easier if we insert the suspend and resume calls here.
489 -- At the same time, we prepare for the stages of the compiler that
490 -- build the proc points. We have to do this at the same time because
491 -- the safe foreign calls need special treatment with respect to infotables.
492 -- A safe foreign call needs an infotable even though it isn't
493 -- a procpoint. The following datatype captures the information
494 -- needed to generate the infotables along with the Cmm data and procedures.
496 data CmmTopForInfoTables
497 = NoInfoTable CmmTopZ -- must be CmmData
498 | ProcInfoTable CmmTopZ BlockSet -- CmmProc; argument is its set of procpoints
499 | FloatingInfoTable CmmInfo BlockId UpdFrameOffset
500 instance Outputable CmmTopForInfoTables where
501 ppr (NoInfoTable t) = text "NoInfoTable: " <+> ppr t
502 ppr (ProcInfoTable t bids) = text "ProcInfoTable: " <+> ppr t <+> ppr bids
503 ppr (FloatingInfoTable info bid upd) =
504 text "FloatingInfoTable: " <+> ppr info <+> ppr bid <+> ppr upd
506 -- The `safeState' record collects the info we update while lowering the
507 -- safe foreign calls in the graph.
508 data SafeState = State { s_blocks :: BlockEnv CmmBlock
509 , s_pps :: ProcPointSet
510 , s_safeCalls :: [CmmTopForInfoTables]}
512 lowerSafeForeignCalls
513 :: [[CmmTopForInfoTables]] -> CmmTopZ -> FuelMonad [[CmmTopForInfoTables]]
514 lowerSafeForeignCalls rst t@(CmmData _ _) = return $ [NoInfoTable t] : rst
515 lowerSafeForeignCalls rst (CmmProc info l args (off, g@(LGraph entry _))) = do
516 let init = return $ State emptyBlockEnv emptyBlockSet []
517 let block b@(Block bid _) z = do
518 state@(State {s_pps = ppset, s_blocks = blocks}) <- z
519 let ppset' = if bid == entry then extendBlockSet ppset bid else ppset
520 state' = state { s_pps = ppset' }
521 if hasSafeForeignCall b
522 then lowerSafeCallBlock state' b
523 else return (state' { s_blocks = insertBlock b blocks })
524 State blocks' g_procpoints safeCalls <- fold_blocks block init g
525 let proc = (CmmProc info l args (off, LGraph entry blocks'))
526 procTable = case off of
527 (_, Just _) -> [ProcInfoTable proc g_procpoints]
528 _ -> [NoInfoTable proc] -- not a successor of a call
529 return $ safeCalls : procTable : rst
531 -- Check for foreign calls -- if none, then we can avoid copying the block.
532 hasSafeForeignCall :: CmmBlock -> Bool
533 hasSafeForeignCall (Block _ t) = tail t
534 where tail (ZTail (MidForeignCall (Safe _ _) _ _ _) _) = True
535 tail (ZTail _ t) = tail t
536 tail (ZLast _) = False
538 -- Lower each safe call in the block, update the CAF and slot environments
539 -- to include each of those calls, and insert the new block in the blockEnv.
540 lowerSafeCallBlock :: SafeState-> CmmBlock -> FuelMonad SafeState
541 lowerSafeCallBlock state b = tail (return state) (ZBlock head (ZLast last))
542 where (head, last) = goto_end (G.unzip b)
543 tail s b@(ZBlock (ZFirst _) _) =
545 return $ state { s_blocks = insertBlock (G.zip b) (s_blocks state) }
546 tail s (ZBlock (ZHead h m@(MidForeignCall (Safe bid updfr_off) _ _ _)) t) =
549 { s_safeCalls = FloatingInfoTable emptyContInfoTable bid updfr_off :
551 (state'', t') <- lowerSafeForeignCall state' m t
552 tail (return state'') (ZBlock h t')
553 tail s (ZBlock (ZHead h m) t) = tail s (ZBlock h (ZTail m t))
556 -- Late in the code generator, we want to insert the code necessary
557 -- to lower a safe foreign call to a sequence of unsafe calls.
558 lowerSafeForeignCall ::
559 SafeState -> Middle -> ZTail Middle Last -> FuelMonad (SafeState, ZTail Middle Last)
560 lowerSafeForeignCall state m@(MidForeignCall (Safe infotable _) _ _ _) tail = do
561 let newTemp rep = getUniqueM >>= \u -> return (LocalReg u rep)
562 -- Both 'id' and 'new_base' are KindNonPtr because they're
563 -- RTS-only objects and are not subject to garbage collection
565 new_base <- newTemp (cmmRegType (CmmGlobal BaseReg))
566 let (caller_save, caller_load) = callerSaveVolatileRegs
567 load_tso <- newTemp gcWord -- TODO FIXME NOW
568 let suspendThread = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "suspendThread")))
569 resumeThread = CmmLit (CmmLabel (mkCmmCodeLabel rtsPackageId (fsLit "resumeThread")))
570 suspend = mkStore (CmmReg spReg) (CmmLit (CmmBlock infotable)) <*>
573 mkUnsafeCall (ForeignTarget suspendThread
574 (ForeignConvention CCallConv [AddrHint] [AddrHint]))
575 [id] [CmmReg (CmmGlobal BaseReg)]
576 resume = mkUnsafeCall (ForeignTarget resumeThread
577 (ForeignConvention CCallConv [AddrHint] [AddrHint]))
578 [new_base] [CmmReg (CmmLocal id)] <*>
579 -- Assign the result to BaseReg: we
580 -- might now have a different Capability!
581 mkAssign (CmmGlobal BaseReg) (CmmReg (CmmLocal new_base)) <*>
583 loadThreadState load_tso
584 Graph tail' blocks' <-
585 liftUniq (graphOfAGraph (suspend <*> mkMiddle m <*> resume <*> mkZTail tail))
586 return (state {s_blocks = s_blocks state `plusBlockEnv` blocks'}, tail')
587 lowerSafeForeignCall _ _ _ = panic "lowerSafeForeignCall was passed something else"