1 {-# OPTIONS -Wall -fno-warn-name-shadowing #-}
6 , dualLiveLattice, dualLiveness
7 , insertSpillsAndReloads --- XXX todo check live-in at entry against formals
8 , dualLivenessWithInsertion
9 , spillAndReloadComments
19 import Outputable hiding (empty)
20 import qualified Outputable as PP
28 -- The point of this module is to insert spills and reloads to
29 -- establish the invariant that at a call (or at any proc point with
30 -- an established protocol) all live variables not expected in
31 -- registers are sitting on the stack. We use a backward analysis to
32 -- insert spills and reloads. It should some day be followed by a
33 -- forward transformation to sink reloads as deeply as possible, so as
34 -- to reduce register pressure.
36 data ExtendWithSpills m
41 type M = ExtendWithSpills Middle
43 -- A variable can be expected to be live in a register, live on the
44 -- stack, or both. This analysis ensures that spills and reloads are
45 -- inserted as needed to make sure that every live variable needed
46 -- after a call is available on the stack. Spills are pushed back to
47 -- their reaching definitions, but reloads are dropped wherever needed
48 -- and will have to be sunk by a later forward transformation.
50 data DualLive = DualLive { on_stack :: RegSet, in_regs :: RegSet }
52 dualUnion :: DualLive -> DualLive -> DualLive
53 dualUnion (DualLive s r) (DualLive s' r') =
54 DualLive (s `unionUniqSets` s') (r `unionUniqSets` r')
56 dualUnionList :: [DualLive] -> DualLive
57 dualUnionList ls = DualLive ss rs
58 where ss = unionManyUniqSets $ map on_stack ls
59 rs = unionManyUniqSets $ map in_regs ls
61 _changeStack, changeRegs :: (RegSet -> RegSet) -> DualLive -> DualLive
62 _changeStack f live = live { on_stack = f (on_stack live) }
63 changeRegs f live = live { in_regs = f (in_regs live) }
66 dualLiveLattice :: DataflowLattice DualLive
68 DataflowLattice "variables live in registers and on stack" empty add False
69 where empty = DualLive emptyRegSet emptyRegSet
70 -- | compute in the Tx monad to track whether anything has changed
71 add new old = do stack <- add1 (on_stack new) (on_stack old)
72 regs <- add1 (in_regs new) (in_regs old)
73 return $ DualLive stack regs
74 add1 = fact_add_to liveLattice
76 dualLivenessWithInsertion :: BPass M Last DualLive
77 dualLivenessWithInsertion = a_ft_b_unlimited dualLiveness insertSpillsAndReloads
80 dualLiveness :: BAnalysis M Last DualLive
81 dualLiveness = BComp "dual liveness" exit last middle first
83 last = lastDualLiveness
84 middle = middleDualLiveness
86 empty = fact_bot dualLiveLattice
88 -- ^ could take a proc-point set and choose to spill here,
89 -- but it's probably better to run this pass, choose
90 -- proc-point protocols, insert more CopyIn nodes, and run
93 middleDualLiveness :: DualLive -> M -> DualLive
94 middleDualLiveness live m@(Spill regs) =
95 -- live-in on-stack requirements are satisfied;
96 -- live-out in-regs obligations are created
97 my_trace "before" (f4sep [ppr m, text "liveness is", ppr live']) $
99 where live' = DualLive { on_stack = on_stack live `minusRegSet` regs
100 , in_regs = in_regs live `plusRegSet` regs }
102 middleDualLiveness live m@(Reload regs) =
103 -- live-in in-regs requirements are satisfied;
104 -- live-out on-stack obligations are created
105 my_trace "before" (f4sep [ppr m, text "liveness is", ppr live']) $
107 where live' = DualLive { on_stack = on_stack live `plusRegSet` regs
108 , in_regs = in_regs live `minusRegSet` regs }
110 middleDualLiveness live (NotSpillOrReload m) = middle m live
111 where middle (MidNop) = id
112 middle (MidComment {}) = id
113 middle (MidAssign (CmmLocal reg') expr) = changeRegs (gen expr . kill reg')
114 middle (MidAssign (CmmGlobal _) expr) = changeRegs (gen expr)
115 middle (MidStore addr rval) = changeRegs (gen addr . gen rval)
116 middle (MidUnsafeCall _ ress args) = changeRegs (gen args . kill ress)
117 middle (CopyIn _ formals _) = changeRegs (kill formals)
118 middle (CopyOut _ formals) = changeRegs (gen formals)
120 lastDualLiveness :: (BlockId -> DualLive) -> Last -> DualLive
121 lastDualLiveness env l = last l
122 where last (LastReturn ress) = changeRegs (gen ress) empty
123 last (LastJump e args) = changeRegs (gen e . gen args) empty
124 last (LastBranch id args) = changeRegs (gen args) $ env id
125 last (LastCall tgt args Nothing) = changeRegs (gen tgt. gen args) empty
126 last (LastCall tgt args (Just k)) =
127 -- nothing can be live in registers at this point
128 -- only 'formals' can be in regs at this point
130 if isEmptyUniqSet (in_regs live) then
131 DualLive (on_stack live) (gen tgt $ gen args emptyRegSet)
133 panic "live values in registers at call continuation"
134 last (LastCondBranch e t f) = changeRegs (gen e) $ dualUnion (env t) (env f)
135 last (LastSwitch e tbl) = changeRegs (gen e) $ dualUnionList $
136 map env (catMaybes tbl)
137 empty = fact_bot dualLiveLattice
139 gen, kill :: UserOfLocalRegs a => a -> RegSet -> RegSet
140 gen a live = foldRegsUsed extendRegSet live a
141 kill a live = foldRegsUsed delOneFromUniqSet live a
143 insertSpillsAndReloads :: BFunctionalTransformation M Last DualLive
144 insertSpillsAndReloads = BComp "CPS spiller" exit last middle first
146 last = \_ _ -> Nothing
147 middle = middleInsertSpillsAndReloads
149 -- ^ could take a proc-point set and choose to spill here,
150 -- but it's probably better to run this pass, choose
151 -- proc-point protocols, insert more CopyIn nodes, and run
155 middleInsertSpillsAndReloads :: DualLive -> M -> Maybe (Graph M Last)
156 middleInsertSpillsAndReloads _ (Spill _) = Nothing
157 middleInsertSpillsAndReloads _ (Reload _) = Nothing
158 middleInsertSpillsAndReloads live (NotSpillOrReload m) = middle m
159 where middle (MidAssign (CmmLocal reg') _) =
160 if reg' `elemRegSet` on_stack live then -- must spill
161 my_trace "Spilling" (f4sep [text "spill" <+> ppr reg',
162 text "after", ppr m]) $
163 Just $ graphOfMiddles [NotSpillOrReload m, Spill $ mkRegSet [reg']]
166 middle (CopyIn _ formals _) =
167 -- only 'formals' can be in regs at this point
168 let regs' = kill formals (in_regs live) -- live in regs; must reload
169 is_stack_var r = elemRegSet r (on_stack live)
170 needs_spilling = -- a formal that is expected on the stack; must spill
171 foldRegsUsed (\rs r -> if is_stack_var r then extendRegSet rs r
172 else rs) emptyRegSet formals
173 in if isEmptyUniqSet regs' && isEmptyUniqSet needs_spilling then
176 let reload = if isEmptyUniqSet regs' then []
178 spill_reload = if isEmptyUniqSet needs_spilling then reload
179 else Spill needs_spilling : reload
180 middles = NotSpillOrReload m : spill_reload
182 my_trace "At CopyIn" (f4sep [text "Triggered by ", ppr live,
183 ppr (Reload regs' :: M),
184 ppr (Spill needs_spilling :: M),
185 text "after", ppr m]) $
186 Just $ graphOfMiddles middles
189 -- | For conversion back to vanilla C--
190 spillAndReloadComments :: M -> Middle
191 spillAndReloadComments (NotSpillOrReload m) = m
192 spillAndReloadComments (Spill regs) = show_regs "Spill" regs
193 spillAndReloadComments (Reload regs) = show_regs "Reload" regs
195 show_regs :: String -> RegSet -> Middle
196 show_regs s regs = MidComment $ mkFastString $ showSDoc $ ppr_regs s regs
199 ---------------------
202 instance Outputable m => Outputable (ExtendWithSpills m) where
203 ppr (Spill regs) = ppr_regs "Spill" regs
204 ppr (Reload regs) = ppr_regs "Reload" regs
205 ppr (NotSpillOrReload m) = ppr m
207 instance Outputable (LGraph M Last) where
210 instance DebugNodes M Last
212 ppr_regs :: String -> RegSet -> SDoc
213 ppr_regs s regs = text s <+> commafy (map ppr $ uniqSetToList regs)
214 where commafy xs = hsep $ punctuate comma xs
216 instance Outputable DualLive where
217 ppr (DualLive {in_regs = regs, on_stack = stack}) =
218 if isEmptyUniqSet regs && isEmptyUniqSet stack then
219 text "<nothing-live>"
221 nest 2 $ fsep [if isEmptyUniqSet regs then PP.empty
222 else (ppr_regs "live in regs =" regs),
223 if isEmptyUniqSet stack then PP.empty
224 else (ppr_regs "live on stack =" stack)]
226 my_trace :: String -> SDoc -> a -> a
227 my_trace = if False then pprTrace else \_ _ a -> a
229 f4sep :: [SDoc] -> SDoc
231 f4sep (d:ds) = fsep (d : map (nest 4) ds)