-{-# OPTIONS -Wall -fno-warn-name-shadowing #-}
+
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)
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)
----------------------------------------------------------------
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 args (Just id)) = LastCall tgt args (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
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
projects / ghc-hetmet.git / blobdiff