Cheng Shao pushed to branch wip/ncg-loopinfo-noop at Glasgow Haskell Compiler / GHC Commits: 52225c88 by Cheng Shao at 2025-08-18T18:23:35+02:00 compiler: use zero cost coerce in GHC.CmmToAsm.CFG.loopInfo This patch refactors GHC.CmmToAsm.CFG.loopInfo to use zero cost coerce and thus addresses the TODO. For coerce to work, constructors of Label/LabelMap/LabelSet from GHC.Cmm.Dataflow.Label are exposed, though I believe it's a worthy tradeoff to avoid unnecessary runtime cost without using unsafeCoerce, since the latter could be a landmine for future refactoring. Co-authored-by: Codex - - - - - 2 changed files: - compiler/GHC/Cmm/Dataflow/Label.hs - compiler/GHC/CmmToAsm/CFG.hs Changes: ===================================== compiler/GHC/Cmm/Dataflow/Label.hs ===================================== @@ -7,9 +7,9 @@ {-# OPTIONS_GHC -Wno-unused-top-binds #-} module GHC.Cmm.Dataflow.Label - ( Label - , LabelMap - , LabelSet + ( Label(..) + , LabelMap(..) + , LabelSet(..) , FactBase , lookupFact , mkHooplLabel ===================================== compiler/GHC/CmmToAsm/CFG.hs ===================================== @@ -56,22 +56,18 @@ import GHC.Utils.Misc import GHC.Data.Graph.Directed import GHC.Data.Maybe -import GHC.Types.Unique import qualified GHC.CmmToAsm.CFG.Dominators as Dom import GHC.CmmToAsm.CFG.Weight -import GHC.Data.Word64Map.Strict (Word64Map) -import GHC.Data.Word64Set (Word64Set) import Data.IntMap.Strict (IntMap) import Data.IntSet (IntSet) import qualified Data.IntMap.Strict as IM -import qualified GHC.Data.Word64Map.Strict as WM import qualified Data.Map as M import qualified Data.IntSet as IS -import qualified GHC.Data.Word64Set as WS import qualified Data.Set as S import Data.Tree import Data.Bifunctor +import Data.Coerce import GHC.Utils.Outputable import GHC.Utils.Panic @@ -92,7 +88,6 @@ import Data.Array.Base (unsafeRead, unsafeWrite) import Control.Monad import GHC.Data.UnionFind -import Data.Word type Prob = Double @@ -849,10 +844,8 @@ loopInfo cfg root = LoopInfo { liBackEdges = backEdges fmap (setFromList . mapKeys ) cfg :: LabelMap LabelSet - --TODO - This should be a no op: Export constructors? Use unsafeCoerce? ... - rooted = ( fromBlockId root - , toWord64Map $ fmap toWord64Set graph) :: (Word64, Word64Map Word64Set) - tree = fmap toBlockId $ Dom.domTree rooted :: Tree BlockId + rooted = coerce (root, graph) + tree = coerce (Dom.domTree rooted) :: Tree BlockId -- Map from Nodes to their dominators domMap :: LabelMap LabelSet @@ -898,11 +891,6 @@ loopInfo cfg root = LoopInfo { liBackEdges = backEdges loopCount n = length $ nub . map fst . filter (setMember n . snd) $ bodies in map (\n -> (n, loopCount n)) $ nodes :: [(BlockId, Int)] - toWord64Set :: LabelSet -> Word64Set - toWord64Set s = WS.fromList . map fromBlockId . setElems $ s - toWord64Map :: LabelMap a -> Word64Map a - toWord64Map m = WM.fromList $ map (\(x,y) -> (fromBlockId x,y)) $ mapToList m - mkDomMap :: Tree BlockId -> LabelMap LabelSet mkDomMap root = mapFromList $ go setEmpty root where @@ -916,12 +904,6 @@ loopInfo cfg root = LoopInfo { liBackEdges = backEdges (\n -> go (setInsert (rootLabel n) parents) n) leaves - fromBlockId :: BlockId -> Word64 - fromBlockId = getKey . getUnique - - toBlockId :: Word64 -> BlockId - toBlockId = mkBlockId . mkUniqueGrimily - -- We make the CFG a Hoopl Graph, so we can reuse revPostOrder. newtype BlockNode (e :: Extensibility) (x :: Extensibility) = BN (BlockId,[BlockId]) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/52225c8817e5d6a841d1d86e4f35ed0d... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/52225c8817e5d6a841d1d86e4f35ed0d... You're receiving this email because of your account on gitlab.haskell.org.