+insertLateReloads :: LGraph M Last -> DFTx (LGraph M Last)
+insertLateReloads g = mapM_blocks insertM g
+ where env = cmmAvailableReloads g
+ avail id = lookupBlockEnv env id `orElse` AvailRegs emptyRegSet
+ insertM b = functionalDFTx "late reloads" (insert b)
+ insert (Block id tail) fuel = propagate (ZFirst id) (avail id) tail fuel
+ propagate h avail (ZTail m t) fuel =
+ let (h', fuel') = maybe_add_reload h avail m fuel in
+ propagate (ZHead h' m) (middleAvail m avail) t fuel'
+ propagate h avail (ZLast l) fuel =
+ let (h', fuel') = maybe_add_reload h avail l fuel in
+ (zipht h' (ZLast l), fuel')
+ maybe_add_reload h avail node fuel =
+ let used = foldRegsUsed
+ (\u r -> if elemAvail avail r then extendRegSet u r else u)
+ emptyRegSet node
+ in if fuel == 0 || isEmptyUniqSet used then (h, fuel)
+ else (ZHead h (Reload used), fuel-1)
+
+
+removeDeadAssignmentsAndReloads :: BPass M Last DualLive
+removeDeadAssignmentsAndReloads = a_ft_b dualLiveness remove_deads
+ where remove_deads = BComp "dead-assignment & -reload elim" exit last middle first
+ exit = Nothing
+ last = \_ _ -> Nothing
+ middle = middleRemoveDeads
+ first _ _ = Nothing
+
+middleRemoveDeads :: DualLive -> M -> Maybe (Graph M Last)
+middleRemoveDeads _ (Spill _) = Nothing
+middleRemoveDeads live (Reload s) =
+ if sizeUniqSet worth_reloading < sizeUniqSet s then
+ Just $ if isEmptyUniqSet worth_reloading then emptyGraph
+ else graphOfMiddles [Reload worth_reloading]
+ else
+ Nothing
+ where worth_reloading = intersectUniqSets s (in_regs live)
+middleRemoveDeads live (NotSpillOrReload m) = middle m
+ where middle (MidAssign (CmmLocal reg') _)
+ | not (reg' `elemRegSet` in_regs live) = Just emptyGraph
+ middle _ = Nothing
+
+
+
+---------------------
+-- register usage
+
+instance UserOfLocalRegs m => UserOfLocalRegs (ExtendWithSpills m) where
+ foldRegsUsed f z (Spill regs) = foldRegsUsed f z regs
+ foldRegsUsed _f z (Reload _) = z
+ foldRegsUsed f z (NotSpillOrReload m) = foldRegsUsed f z m