module CmmContFlowOpt
( runCmmOpts, cmmCfgOpts, cmmCfgOptsZ
, branchChainElimZ, removeUnreachableBlocksZ, predMap
- , replaceLabelsZ, runCmmContFlowOptsZs
+ , replaceLabelsZ, replaceBranches, runCmmContFlowOptsZs
)
where
import ZipCfgCmmRep
import Maybes
-import Monad
+import Control.Monad
import Outputable
-import Panic
import Prelude hiding (unzip, zip)
import Util
-import UniqFM
------------------------------------
runCmmContFlowOptsZs :: [CmmZ] -> [CmmZ]
| cmm_top <- prog ]
cmmCfgOpts :: Tx (ListGraph CmmStmt)
-cmmCfgOptsZ :: Tx CmmGraph
+cmmCfgOptsZ :: Tx (a, CmmGraph)
cmmCfgOpts = branchChainElim -- boring, but will get more exciting later
-cmmCfgOptsZ = branchChainElimZ `seqTx` blockConcatZ `seqTx` removeUnreachableBlocksZ
+cmmCfgOptsZ g =
+ optGraph
+ (branchChainElimZ `seqTx` blockConcatZ `seqTx` removeUnreachableBlocksZ) g
-- Here branchChainElim can ultimately be replaced
-- with a more exciting combination of optimisations
runCmmOpts :: Tx g -> Tx (GenCmm d h g)
-runCmmOpts opt = mapProcs (optGraph opt)
+runCmmOpts opt = mapProcs (optProc opt)
-optGraph :: Tx g -> Tx (GenCmmTop d h g)
-optGraph _ top@(CmmData {}) = noTx top
-optGraph opt (CmmProc info lbl formals g) = fmap (CmmProc info lbl formals) (opt g)
+optProc :: Tx g -> Tx (GenCmmTop d h g)
+optProc _ top@(CmmData {}) = noTx top
+optProc opt (CmmProc info lbl formals g) =
+ fmap (CmmProc info lbl formals) (opt g)
+
+optGraph :: Tx g -> Tx (a, g)
+optGraph opt (a, g) = fmap (\g' -> (a, g')) (opt g)
------------------------------------
mapProcs :: Tx (GenCmmTop d h s) -> Tx (GenCmm d h s)
----------------------------------------------------------------
branchChainElimZ :: Tx CmmGraph
-- Remove any basic block of the form L: goto L',
--- and replace L with L' everywhere else
-branchChainElimZ g@(G.LGraph eid args _)
+-- 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 args (self_branches ++ others)
+ = 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, _) =
- if lookup id == id then
- Just (G.Block id Nothing (G.ZLast (G.mkBranchNode id)))
- else
- Nothing
- in mapMaybe loop_to lone_branch_blocks
+ let loop_to (id, _) =
+ if lookup id == id then
+ Just (G.Block id (G.ZLast (G.mkBranchNode id)))
+ else
+ Nothing
+ in mapMaybe loop_to lone_branch_blocks
lookup id = lookupBlockEnv env id `orElse` id
-isLoneBranchZ :: CmmBlock -> Either (BlockId, BlockId) CmmBlock
-isLoneBranchZ (G.Block id Nothing (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
+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
where
- replace_eid (G.LGraph eid off blocks) = G.LGraph (lookup eid) off blocks
- middle m@(MidComment _) = m
- middle (MidAssign r e) = MidAssign r (exp e)
- middle (MidStore addr e) = MidStore (exp addr) (exp e)
- middle (MidUnsafeCall tgt fs as) = MidUnsafeCall (midcall tgt) fs (map exp as)
- middle (MidAddToContext e es) = MidAddToContext (exp e) (map exp es)
- last (LastBranch id) = LastBranch (lookup id)
- last (LastCondBranch e ti fi) = LastCondBranch (exp e) (lookup ti) (lookup fi)
- last (LastSwitch e tbl) = LastSwitch (exp e) (map (fmap lookup) tbl)
- last (LastCall tgt mb_id s) = LastCall (exp tgt) (fmap lookup mb_id) s
- last (LastJump e s) = LastJump (exp e) s
- last (LastReturn s) = LastReturn s
- midcall (ForeignTarget e c) = ForeignTarget (exp e) c
- midcall m@(PrimTarget _) = m
- exp e@(CmmLit _) = e
- exp (CmmLoad addr ty) = CmmLoad (exp addr) ty
- exp e@(CmmReg _) = e
- exp (CmmMachOp op es) = CmmMachOp op $ map exp es
- exp e@(CmmRegOff _ _) = e
- exp (CmmStackSlot (CallArea (Young id)) i) =
- CmmStackSlot (CallArea (Young (lookup id))) i
- exp e@(CmmStackSlot _ _) = e
+ last (LastBranch id) = LastBranch (lookup id)
+ last (LastCondBranch e ti fi) = LastCondBranch e (lookup ti) (lookup fi)
+ last (LastSwitch e tbl) = LastSwitch e (map (fmap lookup) tbl)
+ last l@(LastCall {}) = l
lookup id = fmap lookup (lookupBlockEnv env id) `orElse` id
----------------------------------------------------------------
predMap :: G.LastNode l => G.LGraph m l -> BlockEnv BlockSet
predMap g = G.fold_blocks add_preds emptyBlockEnv g -- find the back edges
where add_preds b env = foldl (add b) env (G.succs b)
- add (G.Block bid _ _) env b' =
+ add (G.Block bid _) env b' =
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).
--
-- To ensure correctness, we have to make sure that the BlockId of the block
--- we are about to eliminate is not named in another instruction
--- (except an adjacent stack pointer adjustment, which we expect and also eliminate).
--- For
+-- we are about to eliminate is not named in another instruction.
--
-- Note: This optimization does _not_ subsume branch chain elimination.
blockConcatZ :: Tx CmmGraph
blockConcatZ = removeUnreachableBlocksZ `seqTx` blockConcatZ'
blockConcatZ' :: Tx CmmGraph
-blockConcatZ' g@(G.LGraph eid off blocks) =
- tx $ pprTrace "concatMap" (ppr concatMap) $ replaceLabelsZ concatMap $ G.LGraph eid off blocks'
+blockConcatZ' g@(G.LGraph eid blocks) =
+ tx $ replaceLabelsZ concatMap $ G.LGraph eid blocks'
where (changed, blocks', concatMap) =
foldr maybe_concat (False, blocks, emptyBlockEnv) $ G.postorder_dfs g
- maybe_concat b@(G.Block bid _ _) (changed, blocks', concatMap) =
+ maybe_concat b@(G.Block bid _) (changed, blocks', concatMap) =
let unchanged = (changed, extendBlockEnv blocks' bid b, concatMap)
in case G.goto_end $ G.unzip b of
(h, G.LastOther (LastBranch b')) ->
- if num_preds b' == 1 then
+ if canConcatWith b' then
(True, extendBlockEnv blocks' bid $ splice blocks' h b',
extendBlockEnv concatMap b' bid)
else unchanged
_ -> unchanged
num_preds bid = liftM sizeBlockSet (lookupBlockEnv backEdges bid) `orElse` 0
+ canConcatWith b' = b' /= eid && num_preds b' == 1
backEdges = predMap g
splice blocks' h bid' =
case lookupBlockEnv blocks' bid' of
- Just (G.Block _ Nothing t) -> G.zip $ G.ZBlock h t
- Just (G.Block _ (Just _) _) ->
- panic "trying to concatenate but successor block has incoming args"
+ Just (G.Block _ t) -> G.zip $ G.ZBlock h t
Nothing -> panic "unknown successor block"
tx = if changed then aTx else noTx
----------------------------------------------------------------
_ -> id
----------------------------------------------------------------
removeUnreachableBlocksZ :: Tx CmmGraph
-removeUnreachableBlocksZ g@(G.LGraph id off blocks) =
- if length blocks' < sizeUFM blocks then aTx $ G.of_block_list id off blocks'
- else noTx g
+removeUnreachableBlocksZ g@(G.LGraph id blocks) =
+ if length blocks' < sizeBEnv blocks then aTx $ G.of_block_list id blocks'
+ else noTx g
where blocks' = G.postorder_dfs g
projects / ghc-hetmet.git / blobdiff