1 -- | Graph coloring register allocator.
4 -- Live range splitting:
5 -- At the moment regs that are spilled are spilled for all time, even though
6 -- we might be able to allocate them a hardreg in different parts of the code.
8 -- As we're aggressively coalescing before register allocation proper we're not currently
9 -- using the coalescence information present in the graph.
11 -- The function that choosing the potential spills could be a bit cleverer.
13 -- Colors in graphviz graphs could be nicer.
16 module RegAllocColor (
23 import qualified GraphColor as Color
43 -- | The maximum number of build/spill cycles we'll allow.
44 -- We should only need 3 or 4 cycles tops.
45 -- If we run for any longer than this we're probably in an infinite loop,
46 -- It's probably better just to bail out and report a bug at this stage.
51 -- | The top level of the graph coloring register allocator.
54 :: Bool -- ^ whether to generate RegAllocStats, or not.
55 -> UniqFM (UniqSet Reg) -- ^ the registers we can use for allocation
56 -> UniqSet Int -- ^ the set of available spill slots.
57 -> [LiveCmmTop] -- ^ code annotated with liveness information.
59 ( [NatCmmTop] -- ^ code with registers allocated.
60 , [RegAllocStats] ) -- ^ stats for each stage of allocation
62 regAlloc dump regsFree slotsFree code
64 (code_final, debug_codeGraphs, graph_final)
65 <- regAlloc_spin dump 0 trivColorable regsFree slotsFree [] code
68 , reverse debug_codeGraphs )
70 regAlloc_spin dump (spinCount :: Int) triv regsFree slotsFree debug_codeGraphs code
72 -- check that we're not running off down the garden path.
73 when (spinCount > maxSpinCount)
74 $ pprPanic "regAlloc_spin: max build/spill cycle count exceeded."
75 ( text "It looks like the register allocator is stuck in an infinite loop."
76 $$ text "max cycles = " <> int maxSpinCount
77 $$ text "regsFree = " <> (hcat $ punctuate space $ map (docToSDoc . pprUserReg)
78 $ uniqSetToList $ unionManyUniqSets $ eltsUFM regsFree)
79 $$ text "slotsFree = " <> ppr (sizeUniqSet slotsFree))
81 -- build a conflict graph from the code.
82 graph <- buildGraph code
84 -- build a map of how many instructions each reg lives for.
85 -- this is lazy, it won't be computed unless we need to spill
86 let fmLife = plusUFMs_C (\(r1, l1) (r2, l2) -> (r1, l1 + l2))
87 $ map lifetimeCount code
89 -- record startup state
92 then Just $ RegAllocStatsStart
95 , raLifetimes = fmLife }
99 -- the function to choose regs to leave uncolored
100 let spill = chooseSpill_maxLife fmLife
102 -- try and color the graph
103 let (graph_colored, rsSpill)
104 = Color.colorGraph regsFree triv spill graph
106 -- see if we've found a coloring
107 if isEmptyUniqSet rsSpill
109 -- patch the registers using the info in the graph
110 let code_patched = map (patchRegsFromGraph graph_colored) code
112 -- clean out unneeded SPILL/RELOADs
113 let code_spillclean = map cleanSpills code_patched
115 -- strip off liveness information
116 let code_nat = map stripLive code_patched
118 -- rewrite SPILL/REALOAD pseudos into real instructions
119 let spillNatTop = mapGenBlockTop spillNatBlock
120 let code_final = map spillNatTop code_nat
122 -- record what happened in this stage for debugging
125 { raGraph = graph_colored
126 , raPatched = code_patched
127 , raSpillClean = code_spillclean
128 , raFinal = code_final
129 , raSRMs = foldl addSRM (0, 0, 0) $ map countSRMs code_spillclean }
133 then [stat] ++ maybeToList stat1 ++ debug_codeGraphs
138 -- spill the uncolored regs
139 (code_spilled, slotsFree', spillStats)
140 <- regSpill code slotsFree rsSpill
142 -- recalculate liveness
143 let code_nat = map stripLive code_spilled
144 code_relive <- mapM regLiveness code_nat
146 -- record what happened in this stage for debugging
149 { raGraph = graph_colored
150 , raSpillStats = spillStats
151 , raLifetimes = fmLife
152 , raSpilled = code_spilled }
155 regAlloc_spin dump (spinCount + 1) triv regsFree slotsFree'
157 then [stat] ++ maybeToList stat1 ++ debug_codeGraphs
163 -- Simple maxconflicts isn't always good, because we
164 -- can naievely end up spilling vregs that only live for one or two instrs.
167 chooseSpill_maxConflicts
168 :: Color.Graph Reg RegClass Reg
171 chooseSpill_maxConflicts graph
172 = let node = maximumBy
174 (sizeUniqSet $ Color.nodeConflicts n1)
175 (sizeUniqSet $ Color.nodeConflicts n2))
176 $ eltsUFM $ Color.graphMap graph
184 -> Color.Graph Reg RegClass Reg
187 chooseSpill_maxLife life graph
188 = let node = maximumBy (\n1 n2 -> compare (getLife n1) (getLife n2))
189 $ eltsUFM $ Color.graphMap graph
191 -- Orphan vregs die in the same instruction they are born in.
192 -- They will be in the graph, but not in the liveness map.
193 -- Their liveness is 0.
195 = case lookupUFM life (Color.nodeId n) of
202 -- | Build a graph from the liveness and coalesce information in this code.
206 -> UniqSM (Color.Graph Reg RegClass Reg)
210 -- Add the reg-reg conflicts to the graph
211 let conflictSets = unionManyBags (map slurpConflicts code)
212 let graph_conflict = foldrBag graphAddConflictSet Color.initGraph conflictSets
215 -- Add the coalescences edges to the graph.
216 let coalesce = unionManyBags (map slurpJoinMovs code)
217 let graph_coalesce = foldrBag graphAddCoalesce graph_conflict coalesce
219 return $ graph_coalesce
222 -- | Add some conflict edges to the graph.
223 -- Conflicts between virtual and real regs are recorded as exclusions.
227 -> Color.Graph Reg RegClass Reg
228 -> Color.Graph Reg RegClass Reg
230 graphAddConflictSet set graph
231 = let reals = filterUFM isRealReg set
232 virtuals = filterUFM (not . isRealReg) set
234 graph1 = Color.addConflicts virtuals regClass graph
235 graph2 = foldr (\(r1, r2) -> Color.addExclusion r1 regClass r2)
238 | a <- uniqSetToList virtuals
239 , b <- uniqSetToList reals]
244 -- | Add some coalesence edges to the graph
245 -- Coalesences between virtual and real regs are recorded as preferences.
249 -> Color.Graph Reg RegClass Reg
250 -> Color.Graph Reg RegClass Reg
252 graphAddCoalesce (r1, r2) graph
253 | RealReg regno <- r1
254 = Color.addPreference (regWithClass r2) r1 graph
256 | RealReg regno <- r2
257 = Color.addPreference (regWithClass r1) r2 graph
260 = Color.addCoalesce (regWithClass r1) (regWithClass r2) graph
262 where regWithClass r = (r, regClass r)
265 -- | Patch registers in code using the reg -> reg mapping in this graph.
267 :: Color.Graph Reg RegClass Reg
268 -> LiveCmmTop -> LiveCmmTop
270 patchRegsFromGraph graph code
272 -- a function to lookup the hardreg for a virtual reg from the graph.
274 -- leave real regs alone.
278 -- this virtual has a regular node in the graph.
279 | Just node <- Color.lookupNode graph reg
280 = case Color.nodeColor node of
284 -- no node in the graph for this virtual, bad news.
286 = pprPanic "patchRegsFromGraph: register mapping failed."
287 ( text "There is no node in the graph for register " <> ppr reg
289 $$ Color.dotGraph (\x -> text "white") trivColorable graph)
291 in patchEraseLive patchF code
294 plusUFMs_C :: (elt -> elt -> elt) -> [UniqFM elt] -> UniqFM elt
296 = foldl (plusUFM_C f) emptyUFM maps