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...
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