X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Fcmm%2FCmmContFlowOpt.hs;h=e0d95552f901cd4a2e49e3eed8cfe45b7bfbf0b8;hp=022b2ddaa5f376a784b6552cf93b37ae42140862;hb=1e50fd4185479a62e02d987bdfcb1c62712859ca;hpb=1241c26f3552a2037263769e5ef7fa68d9f3be36 diff --git a/compiler/cmm/CmmContFlowOpt.hs b/compiler/cmm/CmmContFlowOpt.hs index 022b2dd..e0d9555 100644 --- a/compiler/cmm/CmmContFlowOpt.hs +++ b/compiler/cmm/CmmContFlowOpt.hs @@ -1,43 +1,60 @@ module CmmContFlowOpt ( runCmmOpts, cmmCfgOpts, cmmCfgOptsZ - , branchChainElimZ, removeUnreachableBlocksZ + , branchChainElimZ, removeUnreachableBlocksZ, predMap + , replaceLabelsZ, replaceBranches, runCmmContFlowOptsZs ) where +import BlockId import Cmm import CmmTx import qualified ZipCfg as G +import ZipCfg import ZipCfgCmmRep + import Maybes +import Control.Monad +import Outputable +import Prelude hiding (unzip, zip) import Util -import UniqFM ------------------------------------ -mapProcs :: Tx (GenCmmTop d h s) -> Tx (GenCmm d h s) -mapProcs f (Cmm tops) = fmap Cmm (mapTx f tops) - +runCmmContFlowOptsZs :: [CmmZ] -> [CmmZ] +runCmmContFlowOptsZs prog + = [ runTx (runCmmOpts cmmCfgOptsZ) cmm_top + | 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` 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) + +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 (GenCmmTop d h g) -optGraph _ top@(CmmData {}) = noTx top -optGraph 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) +mapProcs f (Cmm tops) = fmap Cmm (mapTx f tops) ---------------------------------------------------------------- branchChainElim :: Tx (ListGraph CmmStmt) --- Remove any basic block of the form L: goto L', --- and replace L with L' everywhere else +-- If L is not captured in an instruction, we can remove any +-- basic block of the form L: goto L', and replace L with L' everywhere else. +-- How does L get captured? In a CallArea. branchChainElim (ListGraph blocks) | null lone_branch_blocks -- No blocks to remove = noTx (ListGraph blocks) @@ -51,7 +68,7 @@ branchChainElim (ListGraph blocks) isLoneBranch :: CmmBasicBlock -> Either (BlockId, BlockId) CmmBasicBlock isLoneBranch (BasicBlock id [CmmBranch target]) | id /= target = Left (id, target) isLoneBranch other_block = Right other_block - -- ^ An infinite loop is not a link in a branch chain! + -- An infinite loop is not a link in a branch chain! replaceLabels :: BlockEnv BlockId -> CmmBasicBlock -> CmmBasicBlock replaceLabels env (BasicBlock id stmts) @@ -66,40 +83,123 @@ 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 +-- 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) - env = mkClosureBlockEnv lone_branch_blocks + 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 (G.ZLast (G.mkBranchNode id))) - else - Nothing - in mapMaybe loop_to lone_branch_blocks - lookup id = G.lookupBlockEnv env id `orElse` id - -isLoneBranchZ :: CmmBlock -> Either (G.BlockId, G.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! - -replaceLabelsZ :: BlockEnv G.BlockId -> CmmGraph -> CmmGraph -replaceLabelsZ env = replace_eid . G.map_nodes id id last + 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 + + 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 = 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 blocks) = G.LGraph (lookup eid) blocks - last (LastBranch id args) = LastBranch (lookup id) args - last (LastCondBranch e ti fi) = LastCondBranch e (lookup ti) (lookup fi) - last (LastSwitch e tbl) = LastSwitch e (map (fmap lookup) tbl) - last (LastCall tgt (Just id)) = LastCall tgt (Just $ lookup id) - last exit_jump_return = exit_jump_return - lookup id = G.lookupBlockEnv env id `orElse` id + 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 + +---------------------------------------------------------------- +-- Build a map from a block to its set of predecessors. Very useful. +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' = + extendBlockEnv env b' $ + extendBlockSet (lookupBlockEnv env b' `orElse` emptyBlockSet) bid +---------------------------------------------------------------- +-- 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 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. +-- +-- Note: This optimization does _not_ subsume branch chain elimination. +blockConcatZ :: Tx CmmGraph +blockConcatZ = removeUnreachableBlocksZ `seqTx` blockConcatZ' +blockConcatZ' :: Tx CmmGraph +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) = + let unchanged = (changed, extendBlockEnv blocks' bid b, concatMap) + in case G.goto_end $ G.unzip b of + (h, G.LastOther (LastBranch b')) -> + 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 _ t) -> G.zip $ G.ZBlock h t + Nothing -> panic "unknown successor block" + tx = if changed then aTx else noTx ---------------------------------------------------------------- mkClosureBlockEnv :: [(BlockId, BlockId)] -> BlockEnv BlockId mkClosureBlockEnv blocks = mkBlockEnv $ map follow blocks @@ -108,9 +208,16 @@ mkClosureBlockEnv blocks = mkBlockEnv $ map follow blocks endChain orig id = case lookupBlockEnv singleEnv id of Just id' | id /= orig -> endChain orig id' _ -> id +mkClosureBlockEnvZ :: [(BlockId, BlockId)] -> BlockEnv BlockId +mkClosureBlockEnvZ blocks = mkBlockEnv $ map follow blocks + where singleEnv = mkBlockEnv blocks + follow (id, next) = (id, endChain id next) + endChain orig id = case lookupBlockEnv singleEnv id of + Just id' | id /= orig -> endChain orig id' + _ -> id ---------------------------------------------------------------- removeUnreachableBlocksZ :: Tx CmmGraph removeUnreachableBlocksZ g@(G.LGraph id blocks) = - if length blocks' < sizeUFM blocks then aTx $ G.of_block_list id blocks' - else noTx g + if length blocks' < sizeBEnv blocks then aTx $ G.of_block_list id blocks' + else noTx g where blocks' = G.postorder_dfs g