{-# LANGUAGE GADTs #-} {-# OPTIONS_GHC -fno-warn-warnings-deprecations #-} module CmmLive ( CmmLive , cmmLiveness , liveLattice , noLiveOnEntry, xferLive ) where import BlockId import Cmm import CmmExpr import Control.Monad import OptimizationFuel import PprCmmExpr () import Compiler.Hoopl import Maybes import Outputable import UniqSet ----------------------------------------------------------------------------- -- Calculating what variables are live on entry to a basic block ----------------------------------------------------------------------------- -- | The variables live on entry to a block type CmmLive = RegSet -- | The dataflow lattice liveLattice :: DataflowLattice CmmLive liveLattice = DataflowLattice "live LocalReg's" emptyRegSet add where add _ (OldFact old) (NewFact new) = case unionUniqSets old new of join -> (changeIf $ sizeUniqSet join > sizeUniqSet old, join) -- | A mapping from block labels to the variables live on entry type BlockEntryLiveness = BlockEnv CmmLive ----------------------------------------------------------------------------- -- | Calculated liveness info for a CmmGraph ----------------------------------------------------------------------------- cmmLiveness :: CmmGraph -> FuelUniqSM BlockEntryLiveness cmmLiveness graph = liftM check $ liftM snd $ dataflowPassBwd graph [] $ analBwd liveLattice xferLive where entry = g_entry graph check facts = noLiveOnEntry entry (expectJust "check" $ mapLookup entry facts) facts gen_kill :: (DefinerOfLocalRegs a, UserOfLocalRegs a) => a -> CmmLive -> CmmLive gen_kill a = gen a . kill a -- | On entry to the procedure, there had better not be any LocalReg's live-in. noLiveOnEntry :: BlockId -> CmmLive -> a -> a noLiveOnEntry bid in_fact x = if isEmptyUniqSet in_fact then x else pprPanic "LocalReg's live-in to graph" (ppr bid <+> ppr in_fact) -- | The transfer equations use the traditional 'gen' and 'kill' -- notations, which should be familiar from the dragon book. gen :: UserOfLocalRegs a => a -> RegSet -> RegSet gen a live = foldRegsUsed extendRegSet live a kill :: DefinerOfLocalRegs a => a -> RegSet -> RegSet kill a live = foldRegsDefd delOneFromUniqSet live a -- Testing! xferLive :: BwdTransfer CmmNode CmmLive xferLive = mkBTransfer3 fst mid lst where fst _ f = f mid :: CmmNode O O -> CmmLive -> CmmLive mid n f = gen_kill n f lst :: CmmNode O C -> FactBase CmmLive -> CmmLive lst n f = gen_kill n $ case n of CmmCall {} -> emptyRegSet CmmForeignCall {} -> emptyRegSet _ -> joinOutFacts liveLattice n f