#9013: addWord2# is buggy ------------------------------------+------------------------------------- Reporter: pumpkin | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Unknown/Multiple Architecture: Unknown/Multiple | Type of failure: None/Unknown Difficulty: Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | ------------------------------------+------------------------------------- Looks like its behavior differs between optimization levels: {{{#!haskell {-# LANGUAGE MagicHash, UnboxedTuples #-} import GHC.Prim import GHC.Word big :: Word big = maxBound good = let x = case big of W# w -> w in case plusWord2# x x of (# a, b #) -> (W# a, W# b) main = do putStrLn $ case good of (0, z) -> "Such optimal, much sad" (1, z) -> "No optimization here" }}} I thought I was going crazy! Try the above code with and without -O2 and you'll get different output. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9013 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler