adding new files to do with new cmm functionality

[ghc-hetmet.git] / compiler / cmm / CmmContFlowOpt.hs

diff --git a/compiler/cmm/CmmContFlowOpt.hs b/compiler/cmm/CmmContFlowOpt.hs
new file mode 100644 (file)
index 0000000..149d33e
--- /dev/null
+++ b/compiler/cmm/CmmContFlowOpt.hs
@@ -0,0 +1,116 @@
+{-# OPTIONS -Wall -fno-warn-name-shadowing #-}
+module CmmContFlowOpt
+    ( runCmmOpts, cmmCfgOpts, cmmCfgOptsZ
+    , branchChainElimZ, removeUnreachableBlocksZ
+    )
+where
+
+import Cmm
+import CmmTx
+import qualified ZipCfg as G
+import ZipCfgCmm
+import Maybes
+import Util
+import UniqFM
+
+------------------------------------
+mapProcs :: Tx (GenCmmTop d h s) -> Tx (GenCmm d h s)
+mapProcs f (Cmm tops) = fmap Cmm (mapTx f tops)
+
+
+------------------------------------
+cmmCfgOpts  :: Tx (ListGraph CmmStmt)
+cmmCfgOptsZ :: Tx CmmGraph
+
+cmmCfgOpts  = branchChainElim  -- boring, but will get more exciting later
+cmmCfgOptsZ = branchChainElimZ `seqTx` removeUnreachableBlocksZ
+        -- 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)
+
+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)
+
+----------------------------------------------------------------
+branchChainElim :: Tx (ListGraph CmmStmt)
+-- Remove any basic block of the form L: goto L',
+-- and replace L with L' everywhere else
+branchChainElim (ListGraph blocks)
+  | null lone_branch_blocks     -- No blocks to remove
+  = noTx (ListGraph blocks)
+  | otherwise
+  = aTx (ListGraph new_blocks)
+  where
+    (lone_branch_blocks, others) = partitionWith isLoneBranch blocks
+    new_blocks = map (replaceLabels env) others
+    env = mkClosureBlockEnv lone_branch_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!
+
+replaceLabels :: BlockEnv BlockId -> CmmBasicBlock -> CmmBasicBlock
+replaceLabels env (BasicBlock id stmts)
+  = BasicBlock id (map replace stmts)
+  where
+    replace (CmmBranch id)       = CmmBranch (lookup id)
+    replace (CmmCondBranch e id) = CmmCondBranch e (lookup id)
+    replace (CmmSwitch e tbl)    = CmmSwitch e (map (fmap lookup) tbl)
+    replace other_stmt           = other_stmt
+
+    lookup id = lookupBlockEnv env id `orElse` id 
+----------------------------------------------------------------
+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 _)
+  | 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
+    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
+  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 
+----------------------------------------------------------------
+mkClosureBlockEnv :: [(BlockId, BlockId)] -> BlockEnv BlockId
+mkClosureBlockEnv 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
+    where blocks' = G.postorder_dfs g