[GHC] #10800: vector-0.11 compile time increased substantially with 7.10.1

[GHC]

#10800: vector-0.11 compile time increased substantially with 7.10.1
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        Reporter:  bgamari           |                Owner:  bgamari
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  7.10.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by thomie):

 Compiling `vector` master with HEAD using a devel2 build (which means a
 stage2 compiler  built with `-DDEBUG`), results in a low of warnings such
 as the following:
 {{{
 *** Core Lint warnings : in result of Simplifier ***
 libraries/vector/Data/Vector/Generic.hs:221:1: warning:
     [RHS of length :: forall (v_a3hG :: * -> *) a_a3hH.
                       Vector v_a3hG a_a3hH =>
                       v_a3hG a_a3hH -> Int]
     INLINE binder is (non-rule) loop breaker: length

 libraries/vector/Data/Vector/Generic.hs:1891:1: warning:
     [RHS of unsafeCopy :: forall (v_a38Q :: * -> *)
                                  (m_a38R :: * -> *)
                                  a_a38S.
                           (PrimMonad m_a38R, Vector v_a38Q a_a38S) =>
                           Mutable v_a38Q (PrimState m_a38R) a_a38S
                           -> v_a38Q a_a38S -> m_a38R ()]
     INLINE binder is (non-rule) loop breaker: unsafeCopy
 }}}

 Maybe this gives a clue to what the problem is.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10800#comment:9>
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