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