1 -- | Graph coloring register allocator.
4 -- The function that choosing the potential spills could be a bit cleverer.
5 -- Colors in graphviz graphs could be nicer.
7 {-# OPTIONS -fno-warn-missing-signatures #-}
16 import qualified GraphColor as Color
38 -- | The maximum number of build/spill cycles we'll allow.
39 -- We should only need 3 or 4 cycles tops.
40 -- If we run for any longer than this we're probably in an infinite loop,
41 -- It's probably better just to bail out and report a bug at this stage.
46 -- | The top level of the graph coloring register allocator.
50 -> UniqFM (UniqSet Reg) -- ^ the registers we can use for allocation
51 -> UniqSet Int -- ^ the set of available spill slots.
52 -> [LiveCmmTop] -- ^ code annotated with liveness information.
54 ( [NatCmmTop] -- ^ code with registers allocated.
55 , [RegAllocStats] ) -- ^ stats for each stage of allocation
57 regAlloc dflags regsFree slotsFree code
59 (code_final, debug_codeGraphs, _)
60 <- regAlloc_spin dflags 0 trivColorable regsFree slotsFree [] code
63 , reverse debug_codeGraphs )
65 regAlloc_spin dflags (spinCount :: Int) triv regsFree slotsFree debug_codeGraphs code
67 -- if any of these dump flags are turned on we want to hang on to
68 -- intermediate structures in the allocator - otherwise tell the
69 -- allocator to ditch them early so we don't end up creating space leaks.
71 [ dopt Opt_D_dump_asm_regalloc_stages dflags
72 , dopt Opt_D_dump_asm_stats dflags
73 , dopt Opt_D_dump_asm_conflicts dflags ]
75 -- check that we're not running off down the garden path.
76 when (spinCount > maxSpinCount)
77 $ pprPanic "regAlloc_spin: max build/spill cycle count exceeded."
78 ( text "It looks like the register allocator is stuck in an infinite loop."
79 $$ text "max cycles = " <> int maxSpinCount
80 $$ text "regsFree = " <> (hcat $ punctuate space $ map (docToSDoc . pprUserReg)
81 $ uniqSetToList $ unionManyUniqSets $ eltsUFM regsFree)
82 $$ text "slotsFree = " <> ppr (sizeUniqSet slotsFree))
85 -- Brig's algorithm does reckless coalescing for all but the first allocation stage
86 -- Doing this seems to reduce the number of reg-reg moves, but at the cost-
87 -- of creating more spills. Probably better just to stick with conservative
88 -- coalescing in Color.colorGraph for now.
90 {- code_coalesced1 <- if (spinCount > 0)
94 let code_coalesced1 = code
96 -- build a conflict graph from the code.
97 graph <- {-# SCC "BuildGraph" #-} buildGraph code_coalesced1
100 -- We really do want the graph to be fully evaluated _before_ we start coloring.
101 -- If we don't do this now then when the call to Color.colorGraph forces bits of it,
102 -- the heap will be filled with half evaluated pieces of graph and zillions of apply thunks.
104 seqGraph graph `seq` return ()
107 -- build a map of the cost of spilling each instruction
108 -- this will only actually be computed if we have to spill something.
109 let spillCosts = foldl' plusSpillCostInfo zeroSpillCostInfo
110 $ map slurpSpillCostInfo code_coalesced1
112 -- the function to choose regs to leave uncolored
113 let spill = chooseSpill spillCosts
115 -- record startup state
118 then Just $ RegAllocStatsStart
121 , raSpillCosts = spillCosts }
124 -- try and color the graph
125 let (graph_colored, rsSpill, rmCoalesce)
126 = {-# SCC "ColorGraph" #-}
128 (dopt Opt_RegsIterative dflags)
129 regsFree triv spill graph
131 -- rewrite regs in the code that have been coalesced
132 let patchF reg = case lookupUFM rmCoalesce reg of
133 Just reg' -> patchF reg'
136 = map (patchEraseLive patchF) code_coalesced1
139 -- see if we've found a coloring
140 if isEmptyUniqSet rsSpill
142 -- patch the registers using the info in the graph
143 let code_patched = map (patchRegsFromGraph graph_colored) code_coalesced2
145 -- clean out unneeded SPILL/RELOADs
146 let code_spillclean = map cleanSpills code_patched
148 -- strip off liveness information
149 let code_nat = map stripLive code_spillclean
151 -- rewrite SPILL/RELOAD pseudos into real instructions
152 let spillNatTop = mapGenBlockTop spillNatBlock
153 let code_final = map spillNatTop code_nat
155 -- record what happened in this stage for debugging
158 { raGraph = graph_colored
159 , raCoalesced = rmCoalesce
160 , raPatched = code_patched
161 , raSpillClean = code_spillclean
162 , raFinal = code_final
163 , raSRMs = foldl' addSRM (0, 0, 0) $ map countSRMs code_spillclean }
167 if dump then [stat] ++ maybeToList stat1 ++ debug_codeGraphs
170 -- space leak avoidance
171 seqList statList `seq` return ()
177 -- we couldn't find a coloring, time to spill something
179 -- spill the uncolored regs
180 (code_spilled, slotsFree', spillStats)
181 <- regSpill code_coalesced2 slotsFree rsSpill
183 -- recalculate liveness
184 let code_nat = map stripLive code_spilled
185 code_relive <- mapM regLiveness code_nat
187 -- record what happened in this stage for debugging
190 { raGraph = graph_colored
191 , raCoalesced = rmCoalesce
192 , raSpillStats = spillStats
193 , raSpillCosts = spillCosts
194 , raSpilled = code_spilled }
198 then [stat] ++ maybeToList stat1 ++ debug_codeGraphs
201 -- space leak avoidance
202 seqList statList `seq` return ()
204 regAlloc_spin dflags (spinCount + 1) triv regsFree slotsFree'
210 -- | Build a graph from the liveness and coalesce information in this code.
214 -> UniqSM (Color.Graph Reg RegClass Reg)
218 -- Slurp out the conflicts and reg->reg moves from this code
219 let (conflictList, moveList) =
220 unzip $ map slurpConflicts code
222 -- Slurp out the spill/reload coalesces
223 let moveList2 = map slurpReloadCoalesce code
225 -- Add the reg-reg conflicts to the graph
226 let conflictBag = unionManyBags conflictList
227 let graph_conflict = foldrBag graphAddConflictSet Color.initGraph conflictBag
229 -- Add the coalescences edges to the graph.
230 let moveBag = unionBags (unionManyBags moveList2) (unionManyBags moveList)
231 let graph_coalesce = foldrBag graphAddCoalesce graph_conflict moveBag
233 return graph_coalesce
236 -- | Add some conflict edges to the graph.
237 -- Conflicts between virtual and real regs are recorded as exclusions.
241 -> Color.Graph Reg RegClass Reg
242 -> Color.Graph Reg RegClass Reg
244 graphAddConflictSet set graph
245 = let reals = filterUFM isRealReg set
246 virtuals = filterUFM (not . isRealReg) set
248 graph1 = Color.addConflicts virtuals regClass graph
249 graph2 = foldr (\(r1, r2) -> Color.addExclusion r1 regClass r2)
252 | a <- uniqSetToList virtuals
253 , b <- uniqSetToList reals]
258 -- | Add some coalesence edges to the graph
259 -- Coalesences between virtual and real regs are recorded as preferences.
263 -> Color.Graph Reg RegClass Reg
264 -> Color.Graph Reg RegClass Reg
266 graphAddCoalesce (r1, r2) graph
268 = Color.addPreference (regWithClass r2) r1 graph
271 = Color.addPreference (regWithClass r1) r2 graph
274 = Color.addCoalesce (regWithClass r1) (regWithClass r2) graph
276 where regWithClass r = (r, regClass r)
279 -- | Patch registers in code using the reg -> reg mapping in this graph.
281 :: Color.Graph Reg RegClass Reg
282 -> LiveCmmTop -> LiveCmmTop
284 patchRegsFromGraph graph code
286 -- a function to lookup the hardreg for a virtual reg from the graph.
288 -- leave real regs alone.
292 -- this virtual has a regular node in the graph.
293 | Just node <- Color.lookupNode graph reg
294 = case Color.nodeColor node of
298 -- no node in the graph for this virtual, bad news.
300 = pprPanic "patchRegsFromGraph: register mapping failed."
301 ( text "There is no node in the graph for register " <> ppr reg
303 $$ Color.dotGraph (\_ -> text "white") trivColorable graph)
305 in patchEraseLive patchF code
309 -- for when laziness just isn't what you wanted...
311 seqGraph :: Color.Graph Reg RegClass Reg -> ()
312 seqGraph graph = seqNodes (eltsUFM (Color.graphMap graph))
314 seqNodes :: [Color.Node Reg RegClass Reg] -> ()
318 (n : ns) -> seqNode n `seq` seqNodes ns
320 seqNode :: Color.Node Reg RegClass Reg -> ()
322 = seqReg (Color.nodeId node)
323 `seq` seqRegClass (Color.nodeClass node)
324 `seq` seqMaybeReg (Color.nodeColor node)
325 `seq` (seqRegList (uniqSetToList (Color.nodeConflicts node)))
326 `seq` (seqRegList (uniqSetToList (Color.nodeExclusions node)))
327 `seq` (seqRegList (Color.nodePreference node))
328 `seq` (seqRegList (uniqSetToList (Color.nodeCoalesce node)))
339 seqRegClass :: RegClass -> ()
346 seqMaybeReg :: Maybe Reg -> ()
352 seqRegList :: [Reg] -> ()
356 (r : rs) -> seqReg r `seq` seqRegList rs
362 (r : rs) -> r `seq` seqList rs