Re: [GHC] #8974: 64 bit windows executable built with ghc-7.9.20140405+LLVM segfaults

17 Oct 2016

      #8974: 64 bit windows executable built with ghc-7.9.20140405+LLVM segfaults
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        Reporter:  awson            |                Owner:
            Type:  bug              |               Status:  new
        Priority:  high             |            Milestone:  8.0.1
       Component:  Compiler (LLVM)  |              Version:  7.9
      Resolution:                   |             Keywords:
Operating System:  Windows          |         Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash    |            Test Case:
      Blocked By:                   |             Blocking:
 Related Tickets:                   |  Differential Rev(s):
       Wiki Page:                   |
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Comment (by GordonBGood):

 Replying to [comment:49 awson]:
...
Can't reproduce this neither with ghc-8.0.1.20160826+llvm-3.7, nor with
 ghc-8.1.20160921+llvm-4.0(HEAD). I have no segfaults in both cases (tried
 to increase numLOOPS to 100000 and 200000 -- no segfaults either).
Perhaps, that was a bug in GHC which was fixed since 8.0.1 release?
@awson, Perhaps it has been fixed which would be good - I'm using 64-bit
 Haskell Platform with stock/stable 8.0.1.

 I'm also having segfaults with -fllvm and not without even though I don't
 believe it's using 'Integer' with the following paged Sieve of
 Eratosthenes code:

 {{{
 {-# LANGUAGE FlexibleContexts #-}
 {-# OPTIONS_GHC -O3 -rtsopts #-} -- or O2

 import Data.Bits
 import Data.Array.Base
 import Data.Array.ST (runSTUArray, STUArray(..))

 type PrimeType = Int
 range = 1000000 :: PrimeType
 szPGBTS = (2^14) * 8 :: PrimeType -- CPU L1 cache in bits
 szBPBTS = (2^7) * 8 :: PrimeType -- base primes pages can be much smaller

 primesPages :: PrimeType -> [UArray PrimeType Bool]
 primesPages szpgbts = pagesFrom 0 szPGBTS bppgs where
   makePg lowi szbts bps = runSTUArray $ do
     let limi = lowi + szbts - 1
     let nxt = 3 + limi + limi -- last candidate in range
     cmpsts <- newArray (lowi, limi) False
     let pbts = fromIntegral szbts
     let cull (p:ps) =
           let sqr = p * p in
           if sqr > nxt then return cmpsts
           else let pi = fromIntegral p in
                let cullp c = if c > pbts then return ()
                              else do
                                unsafeWrite cmpsts c True
                                cullp (c + pi) in
                let a = (sqr - 3) `shiftR` 1 in
                let s = if a >= lowi then fromIntegral (a - lowi)
                        else let r = fromIntegral ((lowi - a) `rem` p) in
                             if r == 0 then 0 else pi - r in
                do { cullp s; cull ps }
     if bps == [] then do
       pg0 <- unsafeFreezeSTUArray cmpsts
       cull $ listPagePrms [pg0]
     else cull bps
   pagesFrom lowi bts bps =
     let cf lwi = case makePg lwi bts bps of
           pg -> pg `seq` pg : cf (lwi + bts) in cf lowi
   bppgs =  -- secondary stream of primes
     listPagePrms (makePg 0 szBPBTS [] : (pagesFrom szBPBTS szBPBTS bppgs))

 listPagePrms :: [UArray PrimeType Bool] -> [PrimeType]
 listPagePrms (hdpg @ (UArray lowi _ rng _) : tlpgs) =
   let loop i = if i >= rng then listPagePrms tlpgs
                else if unsafeAt hdpg i then loop (i + 1)
                     else let ii = lowi + fromIntegral i in
                          case 3 + ii + ii of
                            p -> p `seq` p : loop (i + 1) in loop 0

 primesPaged :: () -> [PrimeType]
 primesPaged() = 2 : (listPagePrms $ primesPages szPGBTS)

 main = print $ length $ takeWhile ((>=) range) $ primesPaged()
 }}}

 The above segfaults for the "range" set to a million, but not for some
 lesser values (ie. a hundred thousand) for '-fllvm' with the same
 environment as before.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8974#comment:50
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