#2916: Adding "-auto-all" when using "-O2 -prof" causes "<<loop>>"
--------------------------+-------------------------------------------------
Reporter: BenMoseley | Owner:
Type: bug | Status: new
Priority: normal | Component: Profiling
Version: 6.10.1 | Severity: normal
Keywords: loop auto-all | Testcase:
Os: Windows | Architecture: x86
--------------------------+-------------------------------------------------
The program below works fine (and outputs "ZeroPmt") when compiled with
"-O2 -prof -fno-cse", but when you add in "-auto-all" it causes
"<<loop>>".
There are many ways to workaround the problem, uncommenting pretty much
any of the commented-out lines avoids the issue, but my impression is that
adding "-auto-all" shouldn't cause this.
This is with stock 6.10.1. "-dcore-lint" has no effect.
{{{
--
-- Compile with : ghc -O2 -prof -auto-all -fno-cse --make ~/loop.hs
--
-- ...and it breaks, outputting <<loop>>
-- ...compile without "-auto-all" and you get ZeroPmt
--
import Data.IORef
import qualified Data.Map as Map
import System.IO
import System.IO.Unsafe
import System.Mem.StableName
main :: IO ()
main = do
-- putStrLn $ show $ unHC $ mkHC ZeroPmt -- Works OK
putStrLn $ show $ unHC $ mkHC $ unHC $ mkHC ZeroPmt
data Expr = Add | ZeroPmt deriving (Ord, Eq, Show)
data ExprHC = ExprHC { unStableName :: !(StableName Expr), unHC ::
!Expr} deriving (Eq)
-- {-# NOINLINE mkHC #-} -- Works OK
-- mkHC e = hashConser e -- Works OK
mkHC = hashConser
{-# NOINLINE hashConser #-}
hashConser :: Expr -> ExprHC
hashConser e = deepSeq e (unsafePerformIO $ mkHC' e)
-- hashConser e = seq (e == e) (unsafePerformIO $ mkHC' e)
where
refTbl = unsafePerformIO $ newIORef Map.empty
mkHC' e = do
tbl <- readIORef refTbl
case Map.lookup e tbl of
Just ehc -> return ehc
Nothing -> do
sn <- makeStableName e
let ehc = ExprHC sn e
writeIORef refTbl $ Map.insert e ehc tbl
return ehc
deepSeq :: Eq e => e -> x -> x
deepSeq e x = seq (e == e) x
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2916>
GHC <http://www.haskell.org/ghc/>
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