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{-# LANGUAGE Haskell2010 #-}
{-# LANGUAGE NondecreasingIndentation #-}
{-# LANGUAGE CPP, MagicHash, BlockArguments, UnboxedTuples, ScopedTypeVariables #-}
-- Test the atomic exchange primop.
-- We initialize a value with 1, and then perform exchanges on it
-- with two different values. At the end all the values should still
-- be present.
module Main ( main ) where
import Data.Bits
import GHC.Int
import GHC.Exts
import GHC.Word
import Control.Monad
import Control.Concurrent
import Foreign.Marshal.Alloc
import Foreign.Storable
import Data.List (sort)
import GHC.Exts
import GHC.Types
import GHC.Ptr
#include "MachDeps.h"
main = do
alloca $ \(ptr_p :: Ptr (Ptr Word)) -> do
alloca $ \(ptr_i :: Ptr Word) -> do
alloca $ \(ptr_j :: Ptr Word) -> do
poke ptr_i (1 :: Word)
poke ptr_j (2 :: Word)
--expected to swap
res_i <- cas ptr_i 1 3 :: IO Word
-- expected to fail
res_j <- cas ptr_j 1 4 :: IO Word
putStrLn "Returned results:"
--(1,2)
print (res_i, res_j)
i <-peek ptr_i
j <-peek ptr_j
putStrLn "Stored results:"
--(3,2)
print (i,j)
cas :: Ptr Word -> Word -> Word -> IO Word
cas (Ptr ptr) (W# expected) (W# desired)= do
IO $ \s -> case (atomicCasWordAddr# ptr expected desired s) of
(# s2, old_val #) -> (# s2, W# old_val #)
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