import ZipCfgCmmRep
import Maybes
-import Monad
+import Control.Monad
import Outputable
import Prelude hiding (unzip, zip)
import Util
----------------------------------------------------------------
branchChainElimZ :: Tx CmmGraph
-- Remove any basic block of the form L: goto L',
--- and replace L with L' everywhere else
+-- and replace L with L' everywhere else,
+-- unless L is the successor of a call instruction and L'
+-- is the entry block. You don't want to set the successor
+-- of a function call to the entry block because there is no good way
+-- to store both the infotables for the call and from the callee,
+-- while putting the stack pointer in a consistent place.
+--
+-- JD isn't quite sure when it's safe to share continuations for different
+-- function calls -- have to think about where the SP will be,
+-- so we'll table that problem for now by leaving all call successors alone.
branchChainElimZ g@(G.LGraph eid _)
| null lone_branch_blocks -- No blocks to remove
= noTx g
| otherwise
= aTx $ replaceLabelsZ env $ G.of_block_list eid (self_branches ++ others)
where
- (lone_branch_blocks, others) = partitionWith isLoneBranchZ (G.to_block_list g)
+ blocks = G.to_block_list g
+ (lone_branch_blocks, others) = partitionWith isLoneBranchZ blocks
env = mkClosureBlockEnvZ lone_branch_blocks
self_branches =
let loop_to (id, _) =
in mapMaybe loop_to lone_branch_blocks
lookup id = lookupBlockEnv env id `orElse` id
-isLoneBranchZ :: CmmBlock -> Either (BlockId, BlockId) CmmBlock
-isLoneBranchZ (G.Block id (G.ZLast (G.LastOther (LastBranch target))))
- | id /= target = Left (id,target)
-isLoneBranchZ other = Right other
- -- An infinite loop is not a link in a branch chain!
+ call_succs = foldl add emptyBlockSet blocks
+ where add succs b =
+ case G.last (G.unzip b) of
+ LastOther (LastCall _ (Just k) _ _ _) -> extendBlockSet succs k
+ _ -> succs
+ isLoneBranchZ :: CmmBlock -> Either (BlockId, BlockId) CmmBlock
+ isLoneBranchZ (G.Block id (G.ZLast (G.LastOther (LastBranch target))))
+ | id /= target && not (elemBlockSet id call_succs) = Left (id,target)
+ isLoneBranchZ other = Right other
+ -- An infinite loop is not a link in a branch chain!
+
+maybeReplaceLabels :: (Last -> Bool) -> BlockEnv BlockId -> CmmGraph -> CmmGraph
+maybeReplaceLabels lpred env =
+ replace_eid . G.map_nodes id middle last
+ where
+ replace_eid (G.LGraph eid blocks) = G.LGraph (lookup eid) blocks
+ middle = mapExpDeepMiddle exp
+ last l = if lpred l then mapExpDeepLast exp (last' l) else l
+ last' (LastBranch bid) = LastBranch (lookup bid)
+ last' (LastCondBranch p t f) = LastCondBranch p (lookup t) (lookup f)
+ last' (LastSwitch e arms) = LastSwitch e (map (liftM lookup) arms)
+ last' (LastCall t k a res r) = LastCall t (liftM lookup k) a res r
+ exp (CmmLit (CmmBlock bid)) = CmmLit (CmmBlock (lookup bid))
+ exp (CmmStackSlot (CallArea (Young id)) i) =
+ CmmStackSlot (CallArea (Young (lookup id))) i
+ exp e = e
+ lookup id = fmap lookup (lookupBlockEnv env id) `orElse` id
replaceLabelsZ :: BlockEnv BlockId -> CmmGraph -> CmmGraph
-replaceLabelsZ env = replace_eid . G.map_nodes id middle last
- where
- replace_eid (G.LGraph eid blocks) = G.LGraph (lookup eid) blocks
- middle = mapExpDeepMiddle exp
- last l = mapExpDeepLast exp (last' l)
- last' (LastBranch bid) = LastBranch (lookup bid)
- last' (LastCondBranch p t f) = LastCondBranch p (lookup t) (lookup f)
- last' (LastSwitch e arms) = LastSwitch e (map (liftM lookup) arms)
- last' (LastCall t k a res r) = LastCall t (liftM lookup k) a res r
- exp (CmmLit (CmmBlock bid)) = CmmLit (CmmBlock (lookup bid))
- exp (CmmStackSlot (CallArea (Young id)) i) =
- CmmStackSlot (CallArea (Young (lookup id))) i
- exp e = e
- lookup id = fmap lookup (lookupBlockEnv env id) `orElse` id
+replaceLabelsZ = maybeReplaceLabels (const True)
+
+-- replaceBranchLabels :: BlockEnv BlockId -> CmmGraph -> CmmGraph
+-- replaceBranchLabels env g@(LGraph _ _) = maybeReplaceLabels lpred env g
+-- where lpred (LastBranch _) = True
+-- lpred _ = False
replaceBranches :: BlockEnv BlockId -> CmmGraph -> CmmGraph
replaceBranches env g = map_nodes id id last g
extendBlockEnv env b' $
extendBlockSet (lookupBlockEnv env b' `orElse` emptyBlockSet) bid
----------------------------------------------------------------
--- If a block B branches to a label L, and L has no other predecessors,
+-- If a block B branches to a label L, L is not the entry block,
+-- and L has no other predecessors,
-- then we can splice the block starting with L onto the end of B.
--- Because this optmization can be inhibited by unreachable blocks,
+-- Because this optimization can be inhibited by unreachable blocks,
-- we first take a pass to drops unreachable blocks.
-- Order matters, so we work bottom up (reverse postorder DFS).
--
else unchanged
_ -> unchanged
num_preds bid = liftM sizeBlockSet (lookupBlockEnv backEdges bid) `orElse` 0
- canConcatWith b' = num_preds b' == 1
+ canConcatWith b' = b' /= eid && num_preds b' == 1
backEdges = predMap g
splice blocks' h bid' =
case lookupBlockEnv blocks' bid' of
Just (G.Block _ t) -> G.zip $ G.ZBlock h t
- Nothing -> pprPanic "unknown successor block" (ppr bid' <+> ppr blocks' <+> ppr blocks)
+ Nothing -> panic "unknown successor block"
tx = if changed then aTx else noTx
----------------------------------------------------------------
mkClosureBlockEnv :: [(BlockId, BlockId)] -> BlockEnv BlockId
projects / ghc-hetmet.git / blobdiff