1 {-# LANGUAGE GADTs, NoMonoLocalBinds, FlexibleContexts, ViewPatterns #-}
2 -- Norman likes local bindings
3 -- If this module lives on I'd like to get rid of this flag in due course
5 {-# OPTIONS_GHC -fno-warn-warnings-deprecations #-}
6 {-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
7 #if __GLASGOW_HASKELL__ >= 701
8 -- GHC 7.0.1 improved incomplete pattern warnings with GADTs
9 {-# OPTIONS_GHC -fwarn-incomplete-patterns #-}
14 , dualLiveLattice, dualLiveTransfers, dualLiveness
15 --, insertSpillsAndReloads --- XXX todo check live-in at entry against formals
16 , dualLivenessWithInsertion
19 , removeDeadAssignmentsAndReloads
27 import OptimizationFuel
30 import Outputable hiding (empty)
31 import qualified Outputable as PP
36 import Compiler.Hoopl hiding (Unique)
38 import Prelude hiding (succ, zip)
40 {- Note [Overview of spill/reload]
41 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
42 The point of this module is to insert spills and reloads to
43 establish the invariant that at a call (or at any proc point with
44 an established protocol) all live variables not expected in
45 registers are sitting on the stack. We use a backward analysis to
46 insert spills and reloads. It should be followed by a
47 forward transformation to sink reloads as deeply as possible, so as
48 to reduce register pressure.
50 A variable can be expected to be live in a register, live on the
51 stack, or both. This analysis ensures that spills and reloads are
52 inserted as needed to make sure that every live variable needed
53 after a call is available on the stack. Spills are pushed back to
54 their reaching definitions, but reloads are dropped wherever needed
55 and will have to be sunk by a later forward transformation.
58 data DualLive = DualLive { on_stack :: RegSet, in_regs :: RegSet }
60 dualUnion :: DualLive -> DualLive -> DualLive
61 dualUnion (DualLive s r) (DualLive s' r') =
62 DualLive (s `unionUniqSets` s') (r `unionUniqSets` r')
64 dualUnionList :: [DualLive] -> DualLive
65 dualUnionList ls = DualLive ss rs
66 where ss = unionManyUniqSets $ map on_stack ls
67 rs = unionManyUniqSets $ map in_regs ls
69 changeStack, changeRegs :: (RegSet -> RegSet) -> DualLive -> DualLive
70 changeStack f live = live { on_stack = f (on_stack live) }
71 changeRegs f live = live { in_regs = f (in_regs live) }
74 dualLiveLattice :: DataflowLattice DualLive
75 dualLiveLattice = DataflowLattice "variables live in registers and on stack" empty add
76 where empty = DualLive emptyRegSet emptyRegSet
77 add _ (OldFact old) (NewFact new) = (changeIf $ change1 || change2, DualLive stack regs)
78 where (change1, stack) = add1 (on_stack old) (on_stack new)
79 (change2, regs) = add1 (in_regs old) (in_regs new)
80 add1 old new = if sizeUniqSet join > sizeUniqSet old then (True, join) else (False, old)
81 where join = unionUniqSets old new
83 dualLivenessWithInsertion :: BlockSet -> CmmGraph -> FuelUniqSM CmmGraph
84 dualLivenessWithInsertion procPoints g =
85 liftM fst $ dataflowPassBwd g [] $ analRewBwd dualLiveLattice
86 (dualLiveTransfers (g_entry g) procPoints)
87 (insertSpillAndReloadRewrites g procPoints)
89 dualLiveness :: BlockSet -> CmmGraph -> FuelUniqSM (BlockEnv DualLive)
90 dualLiveness procPoints g =
91 liftM snd $ dataflowPassBwd g [] $ analBwd dualLiveLattice $ dualLiveTransfers (g_entry g) procPoints
93 dualLiveTransfers :: BlockId -> BlockSet -> (BwdTransfer CmmNode DualLive)
94 dualLiveTransfers entry procPoints = mkBTransfer3 first middle last
95 where first :: CmmNode C O -> DualLive -> DualLive
96 first (CmmEntry id) live = check live id $ -- live at procPoint => spill
97 if id /= entry && setMember id procPoints
98 then DualLive { on_stack = on_stack live `plusRegSet` in_regs live
99 , in_regs = emptyRegSet }
101 where check live id x = if id == entry then noLiveOnEntry id (in_regs live) x else x
103 middle :: CmmNode O O -> DualLive -> DualLive
104 middle m = changeStack updSlots
106 where -- Reuse middle of liveness analysis from CmmLive
107 updRegs = case getBTransfer3 xferLive of (_, middle, _) -> middle m
109 updSlots live = foldSlotsUsed reload (foldSlotsDefd spill live m) m
110 spill live s@(RegSlot r, _, _) = check s $ deleteFromRegSet live r
112 reload live s@(RegSlot r, _, _) = check s $ extendRegSet live r
114 check (RegSlot (LocalReg _ ty), o, w) x
115 | o == w && w == widthInBytes (typeWidth ty) = x
116 check _ _ = panic "middleDualLiveness unsupported: slices"
117 last :: CmmNode O C -> FactBase DualLive -> DualLive
118 last l fb = case l of
119 CmmBranch id -> lkp id
120 l@(CmmCall {cml_cont=Nothing}) -> changeRegs (gen l . kill l) empty
121 l@(CmmCall {cml_cont=Just k}) -> call l k
122 l@(CmmForeignCall {succ=k}) -> call l k
123 l@(CmmCondBranch _ t f) -> changeRegs (gen l . kill l) $ dualUnion (lkp t) (lkp f)
124 l@(CmmSwitch _ tbl) -> changeRegs (gen l . kill l) $ dualUnionList $ map lkp (catMaybes tbl)
125 where empty = fact_bot dualLiveLattice
126 lkp id = empty `fromMaybe` lookupFact id fb
127 call l k = DualLive (on_stack (lkp k)) (gen l emptyRegSet)
129 gen :: UserOfLocalRegs a => a -> RegSet -> RegSet
130 gen a live = foldRegsUsed extendRegSet live a
131 kill :: DefinerOfLocalRegs a => a -> RegSet -> RegSet
132 kill a live = foldRegsDefd deleteFromRegSet live a
134 insertSpillAndReloadRewrites :: CmmGraph -> BlockSet -> CmmBwdRewrite DualLive
135 insertSpillAndReloadRewrites graph procPoints = deepBwdRw3 first middle nothing
136 -- Beware: deepBwdRw with one polymorphic function seems more reasonable here,
137 -- but GHC miscompiles it, see bug #4044.
138 where first :: CmmNode C O -> Fact O DualLive -> CmmReplGraph C O
139 first e@(CmmEntry id) live = return $
140 if id /= (g_entry graph) && setMember id procPoints then
141 case map reload (uniqSetToList spill_regs) of
143 is -> Just $ mkFirst e <*> mkMiddles is
146 -- If we are splitting procedures, we need the LastForeignCall
147 -- to spill its results to the stack because they will only
148 -- be used by a separate procedure (so they can't stay in LocalRegs).
150 spill_regs = if splitting then in_regs live
151 else in_regs live `minusRegSet` defs
152 defs = case mapLookup id firstDefs of
154 Nothing -> emptyRegSet
155 -- A LastForeignCall may contain some definitions, which take place
156 -- on return from the function call. Therefore, we build a map (firstDefs)
157 -- from BlockId to the set of variables defined on return to the BlockId.
158 firstDefs = mapFold addLive emptyBlockMap (toBlockMap graph)
159 addLive :: CmmBlock -> BlockEnv RegSet -> BlockEnv RegSet
160 addLive b env = case lastNode b of
161 CmmForeignCall {succ=k, res=defs} -> add k (mkRegSet defs) env
163 add bid defs env = mapInsert bid defs'' env
164 where defs'' = case mapLookup bid env of
165 Just defs' -> timesRegSet defs defs'
168 middle :: CmmNode O O -> Fact O DualLive -> CmmReplGraph O O
169 middle (CmmAssign (CmmLocal reg) (CmmLoad (CmmStackSlot (RegSlot reg') _) _)) _ | reg == reg' = return Nothing
170 middle m@(CmmAssign (CmmLocal reg) _) live = return $
171 if reg `elemRegSet` on_stack live then -- must spill
172 my_trace "Spilling" (f4sep [text "spill" <+> ppr reg,
173 text "after"{-, ppr m-}]) $
174 Just $ mkMiddles $ [m, spill reg]
176 middle _ _ = return Nothing
178 nothing _ _ = return Nothing
180 regSlot :: LocalReg -> CmmExpr
181 regSlot r = CmmStackSlot (RegSlot r) (widthInBytes $ typeWidth $ localRegType r)
183 spill, reload :: LocalReg -> CmmNode O O
184 spill r = CmmStore (regSlot r) (CmmReg $ CmmLocal r)
185 reload r = CmmAssign (CmmLocal r) (CmmLoad (regSlot r) $ localRegType r)
187 removeDeadAssignmentsAndReloads :: BlockSet -> CmmGraph -> FuelUniqSM CmmGraph
188 removeDeadAssignmentsAndReloads procPoints g =
189 liftM fst $ dataflowPassBwd g [] $ analRewBwd dualLiveLattice
190 (dualLiveTransfers (g_entry g) procPoints)
192 where rewrites = deepBwdRw3 nothing middle nothing
193 -- Beware: deepBwdRw with one polymorphic function seems more reasonable here,
194 -- but GHC panics while compiling, see bug #4045.
195 middle :: CmmNode O O -> Fact O DualLive -> CmmReplGraph O O
196 middle (CmmAssign (CmmLocal reg') _) live | not (reg' `elemRegSet` in_regs live) = return $ Just emptyGraph
197 -- XXX maybe this should be somewhere else...
198 middle (CmmStore lhs (CmmLoad rhs _)) _ | lhs == rhs = return $ Just emptyGraph
199 middle _ _ = return Nothing
201 nothing _ _ = return Nothing
203 ----------------------------------------------------------------
204 --- Usage information
206 -- We decorate all register assignments with usage information,
207 -- that is, the maximum number of times the register is referenced
208 -- while it is live along all outgoing control paths. There are a few
211 -- - If a register goes dead, and then becomes live again, the usages
212 -- of the disjoint live range don't count towards the original range.
214 -- a = 1; // used once
216 -- a = 2; // used once
219 -- - A register may be used multiple times, but these all reside in
220 -- different control paths, such that any given execution only uses
221 -- it once. In that case, the usage count may still be 1.
223 -- a = 1; // used once
230 -- This policy corresponds to an inlining strategy that does not
231 -- duplicate computation but may increase binary size.
233 -- - If we naively implement a usage count, we have a counting to
234 -- infinity problem across joins. Furthermore, knowing that
235 -- something is used 2 or more times in one runtime execution isn't
236 -- particularly useful for optimizations (inlining may be beneficial,
237 -- but there's no way of knowing that without register pressure
241 -- // first iteration, b used once
242 -- // second iteration, b used twice
243 -- // third iteration ...
246 -- // b used zero times
248 -- There is an orthogonal question, which is that for every runtime
249 -- execution, the register may be used only once, but if we inline it
250 -- in every conditional path, the binary size might increase a lot.
251 -- But tracking this information would be tricky, because it violates
252 -- the finite lattice restriction Hoopl requires for termination;
253 -- we'd thus need to supply an alternate proof, which is probably
254 -- something we should defer until we actually have an optimization
255 -- that would take advantage of this. (This might also interact
256 -- strangely with liveness information.)
259 -- // a is used one time, but in X different paths
266 -- This analysis is very similar to liveness analysis; we just keep a
267 -- little extra info. (Maybe we should move it to CmmLive, and subsume
268 -- the old liveness analysis.)
270 data RegUsage = SingleUse | ManyUse
271 deriving (Ord, Eq, Show)
272 -- Absence in map = ZeroUse
275 -- minBound is bottom, maxBound is top, least-upper-bound is max
276 -- ToDo: Put this in Hoopl. Note that this isn't as useful as I
277 -- originally hoped, because you usually want to leave out the bottom
278 -- element when you have things like this put in maps. Maybe f is
279 -- useful on its own as a combining function.
280 boundedOrdLattice :: (Bounded a, Ord a) => String -> DataflowLattice a
281 boundedOrdLattice n = DataflowLattice n minBound f
282 where f _ (OldFact x) (NewFact y)
283 | x >= y = (NoChange, x)
284 | otherwise = (SomeChange, y)
287 -- Custom node type we'll rewrite to. CmmAssign nodes to local
288 -- registers are replaced with AssignLocal nodes.
289 data WithRegUsage n e x where
290 Plain :: n e x -> WithRegUsage n e x
291 AssignLocal :: LocalReg -> CmmExpr -> RegUsage -> WithRegUsage n O O
293 instance UserOfLocalRegs (n e x) => UserOfLocalRegs (WithRegUsage n e x) where
294 foldRegsUsed f z (Plain n) = foldRegsUsed f z n
295 foldRegsUsed f z (AssignLocal _ e _) = foldRegsUsed f z e
297 instance DefinerOfLocalRegs (n e x) => DefinerOfLocalRegs (WithRegUsage n e x) where
298 foldRegsDefd f z (Plain n) = foldRegsDefd f z n
299 foldRegsDefd f z (AssignLocal r _ _) = foldRegsDefd f z r
301 instance NonLocal n => NonLocal (WithRegUsage n) where
302 entryLabel (Plain n) = entryLabel n
303 successors (Plain n) = successors n
305 liftRegUsage :: Graph n e x -> Graph (WithRegUsage n) e x
306 liftRegUsage = mapGraph Plain
308 eraseRegUsage :: Graph (WithRegUsage CmmNode) e x -> Graph CmmNode e x
309 eraseRegUsage = mapGraph f
310 where f :: WithRegUsage CmmNode e x -> CmmNode e x
311 f (AssignLocal l e _) = CmmAssign (CmmLocal l) e
314 type UsageMap = UniqFM RegUsage
316 usageLattice :: DataflowLattice UsageMap
317 usageLattice = DataflowLattice "usage counts for registers" emptyUFM (joinUFM f)
318 where f _ (OldFact x) (NewFact y)
319 | x >= y = (NoChange, x)
320 | otherwise = (SomeChange, y)
322 -- We reuse the names 'gen' and 'kill', although we're doing something
323 -- slightly different from the Dragon Book
324 usageTransfer :: BwdTransfer (WithRegUsage CmmNode) UsageMap
325 usageTransfer = mkBTransfer3 first middle last
327 middle :: WithRegUsage CmmNode O O -> UsageMap -> UsageMap
328 middle n f = gen_kill n f
329 last :: WithRegUsage CmmNode O C -> FactBase UsageMap -> UsageMap
330 -- Checking for CmmCall/CmmForeignCall is unnecessary, because
331 -- spills/reloads have already occurred by the time we do this
333 -- XXX Deprecated warning is puzzling: what label are we
335 -- ToDo: With a bit more cleverness here, we can avoid
336 -- disappointment and heartbreak associated with the inability
337 -- to inline into CmmCall and CmmForeignCall by
338 -- over-estimating the usage to be ManyUse.
339 last n f = gen_kill n (joinOutFacts usageLattice n f)
340 gen_kill a = gen a . kill a
341 gen a f = foldRegsUsed increaseUsage f a
342 kill a f = foldRegsDefd delFromUFM f a
343 increaseUsage f r = addToUFM_C combine f r SingleUse
344 where combine _ _ = ManyUse
346 usageRewrite :: BwdRewrite FuelUniqSM (WithRegUsage CmmNode) UsageMap
347 usageRewrite = mkBRewrite3 first middle last
348 where first _ _ = return Nothing
349 middle :: Monad m => WithRegUsage CmmNode O O -> UsageMap -> m (Maybe (Graph (WithRegUsage CmmNode) O O))
350 middle (Plain (CmmAssign (CmmLocal l) e)) f
352 $ case lookupUFM f l of
353 Nothing -> emptyGraph
354 Just usage -> mkMiddle (AssignLocal l e usage)
355 middle _ _ = return Nothing
356 last _ _ = return Nothing
358 type CmmGraphWithRegUsage = GenCmmGraph (WithRegUsage CmmNode)
359 annotateUsage :: CmmGraph -> FuelUniqSM (CmmGraphWithRegUsage)
360 annotateUsage vanilla_g =
361 let g = modifyGraph liftRegUsage vanilla_g
362 in liftM fst $ dataflowPassBwd g [(g_entry g, fact_bot usageLattice)] $
363 analRewBwd usageLattice usageTransfer usageRewrite
365 ----------------------------------------------------------------
366 --- Assignment tracking
368 -- The idea is to maintain a map of local registers do expressions,
369 -- such that the value of that register is the same as the value of that
370 -- expression at any given time. We can then do several things,
371 -- as described by Assignment.
373 -- Assignment describes the various optimizations that are valid
374 -- at a given point in the program.
376 -- This assignment can always be inlined. It is cheap or single-use.
378 -- This assignment should be sunk down to its first use. (This will
379 -- increase code size if the register is used in multiple control flow
380 -- paths, but won't increase execution time, and the reduction of
381 -- register pressure is worth it.)
383 -- We cannot safely optimize occurrences of this local register. (This
384 -- corresponds to top in the lattice structure.)
387 -- Extract the expression that is being assigned to
388 xassign :: Assignment -> Maybe CmmExpr
389 xassign (AlwaysInline e) = Just e
390 xassign (AlwaysSink e) = Just e
391 xassign NeverOptimize = Nothing
393 -- Extracts the expression, but only if they're the same constructor
394 xassign2 :: (Assignment, Assignment) -> Maybe (CmmExpr, CmmExpr)
395 xassign2 (AlwaysInline e, AlwaysInline e') = Just (e, e')
396 xassign2 (AlwaysSink e, AlwaysSink e') = Just (e, e')
399 -- Note: We'd like to make decisions about "not optimizing" as soon as
400 -- possible, because this will make running the transfer function more
402 type AssignmentMap = UniqFM Assignment
404 assignmentLattice :: DataflowLattice AssignmentMap
405 assignmentLattice = DataflowLattice "assignments for registers" emptyUFM (joinUFM add)
406 where add _ (OldFact old) (NewFact new)
408 (NeverOptimize, _) -> (NoChange, NeverOptimize)
409 (_, NeverOptimize) -> (SomeChange, NeverOptimize)
410 (xassign2 -> Just (e, e'))
411 | e == e' -> (NoChange, old)
412 | otherwise -> (SomeChange, NeverOptimize)
413 _ -> (SomeChange, NeverOptimize)
415 -- Deletes sinks from assignment map, because /this/ is the place
416 -- where it will be sunk to.
417 deleteSinks :: UserOfLocalRegs n => n -> AssignmentMap -> AssignmentMap
418 deleteSinks n m = foldRegsUsed (adjustUFM f) m n
419 where f (AlwaysSink _) = NeverOptimize
422 -- Invalidates any expressions that use a register.
423 invalidateUsersOf :: CmmReg -> AssignmentMap -> AssignmentMap
424 invalidateUsersOf reg = mapUFM (invalidateUsers' reg)
425 where invalidateUsers' reg (xassign -> Just e) | reg `regUsedIn` e = NeverOptimize
426 invalidateUsers' _ old = old
428 middleAssignment :: WithRegUsage CmmNode O O -> AssignmentMap -> AssignmentMap
430 -- Algorithm for annotated assignments:
431 -- 1. Delete any sinking assignments that were used by this instruction
432 -- 2. Add the assignment to our list of valid local assignments with
433 -- the correct optimization policy.
434 -- 3. Look for all assignments that reference that register and
436 middleAssignment n@(AssignLocal r e usage) assign
437 = invalidateUsersOf (CmmLocal r) . add . deleteSinks n $ assign
438 where add m = addToUFM m r
440 SingleUse -> AlwaysInline e
442 decide CmmLit{} = AlwaysInline e
443 decide CmmReg{} = AlwaysInline e
444 decide CmmLoad{} = AlwaysSink e
445 decide CmmStackSlot{} = AlwaysSink e
446 decide CmmMachOp{} = AlwaysSink e
447 decide CmmRegOff{} = AlwaysSink e
449 -- Algorithm for unannotated assignments of global registers:
450 -- 1. Delete any sinking assignments that were used by this instruction
451 -- 2. Look for all assignments that reference this register and
453 middleAssignment (Plain n@(CmmAssign reg@(CmmGlobal _) _)) assign
454 = invalidateUsersOf reg . deleteSinks n $ assign
456 -- Algorithm for unannotated assignments of *local* registers: do
457 -- nothing (it's a reload, so no state should have changed)
458 middleAssignment (Plain (CmmAssign (CmmLocal _) _)) assign = assign
460 -- Algorithm for stores:
461 -- 1. Delete any sinking assignments that were used by this instruction
462 -- 2. Look for all assignments that load from memory locations that
463 -- were clobbered by this store and invalidate them.
464 middleAssignment (Plain n@(CmmStore lhs rhs)) assign
465 = mapUFM_Directly p . deleteSinks n $ assign
466 -- ToDo: There's a missed opportunity here: even if a memory
467 -- access we're attempting to sink gets clobbered at some
468 -- location, it's still /better/ to sink it to right before the
469 -- point where it gets clobbered. How might we do this?
470 -- Unfortunately, it's too late to change the assignment...
471 where p r (xassign -> Just x) | (lhs, rhs) `clobbers` (r, x) = NeverOptimize
474 -- Assumption: Unsafe foreign calls don't clobber memory
475 middleAssignment (Plain n@(CmmUnsafeForeignCall{})) assign
476 = foldRegsDefd (\m r -> addToUFM m r NeverOptimize) (deleteSinks n assign) n
478 middleAssignment (Plain (CmmComment {})) assign
482 -- * Stack slots do not overlap with any other memory locations
483 -- * Non stack-slot stores always conflict with each other. (This is
484 -- not always the case; we could probably do something special for Hp)
485 -- * Stack slots for different areas do not overlap
486 -- * Stack slots within the same area and different offsets may
487 -- overlap; we need to do a size check (see 'overlaps').
488 clobbers :: (CmmExpr, CmmExpr) -> (Unique, CmmExpr) -> Bool
489 clobbers (ss@CmmStackSlot{}, CmmReg (CmmLocal r)) (u, CmmLoad (ss'@CmmStackSlot{}) _)
490 | getUnique r == u, ss == ss' = False -- No-op on the stack slot (XXX: Do we need this special case?)
491 clobbers (CmmStackSlot (CallArea a) o, rhs) (_, expr) = f expr
492 where f (CmmLoad (CmmStackSlot (CallArea a') o') t)
493 = (a, o, widthInBytes (cmmExprWidth rhs)) `overlaps` (a', o', widthInBytes (typeWidth t))
494 f (CmmLoad e _) = containsStackSlot e
495 f (CmmMachOp _ es) = or (map f es)
497 -- Maybe there's an invariant broken if this actually ever
499 containsStackSlot (CmmLoad{}) = True -- load of a load, all bets off
500 containsStackSlot (CmmMachOp _ es) = or (map containsStackSlot es)
501 containsStackSlot (CmmStackSlot{}) = True
502 containsStackSlot _ = False
503 clobbers _ (_, e) = f e
504 where f (CmmLoad (CmmStackSlot _ _) _) = False
505 f (CmmLoad{}) = True -- conservative
506 f (CmmMachOp _ es) = or (map f es)
509 -- Check for memory overlapping.
516 type CallSubArea = (AreaId, Int, Int) -- area, offset, width
517 overlaps :: CallSubArea -> CallSubArea -> Bool
518 overlaps (a, _, _) (a', _, _) | a /= a' = False
519 overlaps (_, o, w) (_, o', w') =
522 in (s' < o) && (s < o) -- Not LTE, because [ I32 ][ I32 ] is OK
524 lastAssignment :: WithRegUsage CmmNode O C -> AssignmentMap -> [(Label, AssignmentMap)]
525 -- Variables are dead across calls, so invalidating all mappings is justified
526 lastAssignment (Plain (CmmCall _ (Just k) _ _ _)) assign = [(k, mapUFM (const NeverOptimize) assign)]
527 lastAssignment (Plain (CmmForeignCall {succ=k})) assign = [(k, mapUFM (const NeverOptimize) assign)]
528 lastAssignment l assign = map (\id -> (id, assign)) $ successors l
530 assignmentTransfer :: FwdTransfer (WithRegUsage CmmNode) AssignmentMap
531 assignmentTransfer = mkFTransfer3 (flip const) middleAssignment ((mkFactBase assignmentLattice .) . lastAssignment)
533 assignmentRewrite :: FwdRewrite FuelUniqSM (WithRegUsage CmmNode) AssignmentMap
534 assignmentRewrite = mkFRewrite3 first middle last
536 first _ _ = return Nothing
537 middle (Plain m) assign = return $ rewrite assign (precompute assign m) mkMiddle m
538 middle _ _ = return Nothing
539 last (Plain l) assign = return $ rewrite assign (precompute assign l) mkLast l
540 -- Tuple is (inline?, reloads)
541 precompute assign n = foldRegsUsed f (False, []) n -- duplicates are harmless
542 where f (i, l) r = case lookupUFM assign r of
543 Just (AlwaysSink e) -> (i, (Plain (CmmAssign (CmmLocal r) e)):l)
544 Just (AlwaysInline _) -> (True, l)
545 Just NeverOptimize -> (i, l)
546 -- This case can show up when we have
547 -- limited optimization fuel.
549 rewrite _ (False, []) _ _ = Nothing
550 -- Note [CmmCall Inline Hack]
551 -- ToDo: Conservative hack: don't do any inlining on CmmCalls, since
552 -- the code produced here tends to be unproblematic and I need
553 -- to write lint passes to ensure that we don't put anything in
554 -- the arguments that could be construed as a global register by
555 -- some later translation pass. (For example, slots will turn
556 -- into dereferences of Sp). This is the same hack in spirit as
557 -- was in cmm/CmmOpt.hs. Fix this up to only bug out if certain
558 -- CmmExprs are involved.
559 -- ToDo: We miss an opportunity here, where all possible
560 -- inlinings should instead be sunk.
561 rewrite _ (True, []) _ n | not (inlinable n) = Nothing -- see [CmmCall Inline Hack]
562 rewrite assign (i, xs) mk n = Just $ mkMiddles xs <*> mk (Plain (inline i assign n))
564 inline :: Bool -> AssignmentMap -> CmmNode e x -> CmmNode e x
566 inline True _ n | not (inlinable n) = n -- see [CmmCall Inline Hack]
567 inline True assign n = mapExpDeep inlineExp n
568 where inlineExp old@(CmmReg (CmmLocal r))
569 = case lookupUFM assign r of
570 Just (AlwaysInline x) -> x
572 inlineExp old@(CmmRegOff (CmmLocal r) i)
573 = case lookupUFM assign r of
574 Just (AlwaysInline x) -> CmmMachOp (MO_Add rep) [x, CmmLit (CmmInt (fromIntegral i) rep)]
575 where rep = typeWidth (localRegType r)
579 inlinable :: CmmNode e x -> Bool
580 inlinable (CmmCall{}) = False
581 inlinable (CmmForeignCall{}) = False
584 rewriteAssignments :: CmmGraph -> FuelUniqSM CmmGraph
585 rewriteAssignments g = do
586 g' <- annotateUsage g
587 g'' <- liftM fst $ dataflowPassFwd g' [(g_entry g, fact_bot assignmentLattice)] $
588 analRewFwd assignmentLattice assignmentTransfer assignmentRewrite
589 return (modifyGraph eraseRegUsage g'')
591 ---------------------
594 ppr_regs :: String -> RegSet -> SDoc
595 ppr_regs s regs = text s <+> commafy (map ppr $ uniqSetToList regs)
596 where commafy xs = hsep $ punctuate comma xs
598 instance Outputable DualLive where
599 ppr (DualLive {in_regs = regs, on_stack = stack}) =
600 if isEmptyUniqSet regs && isEmptyUniqSet stack then
601 text "<nothing-live>"
603 nest 2 $ fsep [if isEmptyUniqSet regs then PP.empty
604 else (ppr_regs "live in regs =" regs),
605 if isEmptyUniqSet stack then PP.empty
606 else (ppr_regs "live on stack =" stack)]
608 -- ToDo: Outputable instance for UsageMap and AssignmentMap
610 my_trace :: String -> SDoc -> a -> a
611 my_trace = if False then pprTrace else \_ _ a -> a
613 f4sep :: [SDoc] -> SDoc
615 f4sep (d:ds) = fsep (d : map (nest 4) ds)