#7460: Double literals generated bad core
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Reporter: tibbe | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.2 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Runtime performance bug | Blockedby:
Blocking: | Related:
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The following code results in core containing expression like
`doubleFromInteger (wordToInteger sc_s2pw)`:
{{{
{-# LANGUAGE CPP, BangPatterns #-}
module Main (main) where
#define VDIM 100
#define VNUM 100000
import Data.Array.Base
import Data.Array.ST
import Data.Array.Unboxed
import Control.Monad.ST
import GHC.Word
import Control.Monad
import Data.Bits
prng :: Word -> Word
prng w = w'
where
!w1 = w `xor` (w `shiftL` 13)
!w2 = w1 `xor` (w1 `shiftR` 7)
!w' = w2 `xor` (w2 `shiftL` 17)
type Vec s = STUArray s Int Double
kahan :: Vec s -> Vec s -> ST s ()
kahan s c = do
let inner w j
| j < VDIM = do
!cj <- unsafeRead c j
!sj <- unsafeRead s j
let !y = fromIntegral w - cj
!t = sj + y
!w' = prng w
unsafeWrite c j ((t-sj)-y)
unsafeWrite s j t
inner w' (j+1)
| otherwise = return ()
outer i | i < VNUM = inner i 0 >> outer (i + 1)
| otherwise = return ()
outer 0
calc :: ST s (Vec s)
calc = do
s <- newArray (0,VDIM-1) 0
c <- newArray (0,VDIM-1) 0
kahan s c
return s
main :: IO ()
main = print . elems $ runSTUArray calc
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7460>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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