X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Fcmm%2FCmmContFlowOpt.hs;h=e0d95552f901cd4a2e49e3eed8cfe45b7bfbf0b8;hp=a3239b94a1dc5af6b50f30b9778d83d777173847;hb=1e50fd4185479a62e02d987bdfcb1c62712859ca;hpb=e6243a818496aad82b6f47511d3bd9bc800f747d diff --git a/compiler/cmm/CmmContFlowOpt.hs b/compiler/cmm/CmmContFlowOpt.hs index a3239b9..e0d9555 100644 --- a/compiler/cmm/CmmContFlowOpt.hs +++ b/compiler/cmm/CmmContFlowOpt.hs @@ -14,9 +14,8 @@ import ZipCfg import ZipCfgCmmRep import Maybes -import Monad +import Control.Monad import Outputable -import Panic import Prelude hiding (unzip, zip) import Util @@ -27,20 +26,25 @@ runCmmContFlowOptsZs prog | cmm_top <- prog ] cmmCfgOpts :: Tx (ListGraph CmmStmt) -cmmCfgOptsZ :: Tx CmmGraph +cmmCfgOptsZ :: Tx (a, CmmGraph) cmmCfgOpts = branchChainElim -- boring, but will get more exciting later 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) @@ -79,48 +83,69 @@ replaceLabels env (BasicBlock id stmts) ---------------------------------------------------------------- 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 emptyStackInfo (G.ZLast (G.mkBranchNode id))) + 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 --- Be careful not to mark a block as a lone branch if it carries --- important information about incoming arguments or the update frame. -isLoneBranchZ :: CmmBlock -> Either (BlockId, BlockId) CmmBlock -isLoneBranchZ (G.Block id (StackInfo {argBytes = Nothing, returnOff = 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 - where - replace_eid (G.LGraph eid off blocks) = G.LGraph (lookup eid) off 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 r) = LastCall t (liftM lookup k) a 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 @@ -136,13 +161,14 @@ replaceBranches env g = map_nodes id id last g 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). -- @@ -153,11 +179,11 @@ predMap g = G.fold_blocks add_preds emptyBlockEnv g -- find the back edges blockConcatZ :: Tx CmmGraph blockConcatZ = removeUnreachableBlocksZ `seqTx` blockConcatZ' blockConcatZ' :: Tx CmmGraph -blockConcatZ' g@(G.LGraph eid off blocks) = - tx $ 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')) -> @@ -167,18 +193,12 @@ blockConcatZ' g@(G.LGraph eid off blocks) = else unchanged _ -> unchanged num_preds bid = liftM sizeBlockSet (lookupBlockEnv backEdges bid) `orElse` 0 - canConcatWith b' = - case lookupBlockEnv blocks b' of - Just (G.Block _ (StackInfo {returnOff = Nothing}) _) -> num_preds b' == 1 - _ -> False + canConcatWith b' = b' /= eid && num_preds b' == 1 backEdges = predMap g splice blocks' h bid' = case lookupBlockEnv blocks' bid' of - Just (G.Block _ (StackInfo {returnOff = Nothing}) t) -> - G.zip $ G.ZBlock h t - Just (G.Block _ _ _) -> - panic "trying to concatenate but successor block has incoming args" - Nothing -> pprPanic "unknown successor block" (ppr bid' <+> ppr blocks' <+> ppr blocks) + Just (G.Block _ t) -> G.zip $ G.ZBlock h t + Nothing -> panic "unknown successor block" tx = if changed then aTx else noTx ---------------------------------------------------------------- mkClosureBlockEnv :: [(BlockId, BlockId)] -> BlockEnv BlockId @@ -197,7 +217,7 @@ mkClosureBlockEnvZ blocks = mkBlockEnv $ map follow blocks _ -> id ---------------------------------------------------------------- removeUnreachableBlocksZ :: Tx CmmGraph -removeUnreachableBlocksZ g@(G.LGraph id off blocks) = - if length blocks' < sizeBEnv blocks then aTx $ G.of_block_list id off blocks' +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