7.8.1 uses a lot of memory when compiling attoparsec programs using <|>

To reproduce, install a pre-0.11.2.1 version of attoparsec. This bug was worked around in 0.11.2.1 by removing the INLINE on plus in attoparsec.

With this test program:

{-# LANGUAGE OverloadedStrings #-}

import Control.Applicative
import Data.Attoparsec.Text
import Data.Text (Text)

parser :: Parser Text
parser = string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"
     <|> string "a" <|> string "a"

main :: IO ()
main = parseTest parser "a"

and using GHC 7.8.1.rc2:

Compiling using -O2, GHC tops out at ~1GB of RAM and takes 25s.

Using -O0, GHC takes 0.47s and uses <150MB of RAM.

Compare this with GHC 7.6.3:

Compiling using -O2, GHC uses <150MB and takes 3.7s. Memory usage is similar with -O0 although compile time goes down to 0.36s.

An extreme version of this bug can be found in the thyme package here: https://github.com/liyang/thyme/blob/master/src/Data/Thyme/Format.hs#L589-L693. Compiling that module with an unfixed attoparsec makes GHC use all available memory and stall out, forcing kill -9. Replacing the function body with undefined makes the package compile as expected.

Trac metadata

Trac field	Value
Version	7.8.1-rc2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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