[GHC] #13369: Float-out is not idempotent

[GHC]

#13369: Float-out is not idempotent
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Simon Peyton Jones <simonpj@…>):

 In [changeset:"fb9ae288088a3eabc4e1bb4e86fa473a3881d2e2/ghc"
 fb9ae288/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="fb9ae288088a3eabc4e1bb4e86fa473a3881d2e2"
 Make FloatOut/SetLevels idemoptent on bottoming functions

 This fixes Trac #13369.  It turned out that I really had got the
 bottoming-float code wrong, again.  The new story is explained in
 Note [Bottoming floats], esp item (3), and Note [Floating from a RHS].

 I didn't make a regression test; it's hard to to so.

 Nofib result are good

 --------------------------------------------------------------------------------
         Program           Size    Allocs   Runtime   Elapsed  TotalMem
 --------------------------------------------------------------------------------
          banner          -2.2%     -4.6%      0.00      0.00     +0.0%
            bspt          -1.3%     -1.6%      0.01      0.01     +0.0%
       cacheprof          -1.8%     -0.3%     +3.7%     +3.7%     -0.9%
    digits-of-e2          -1.0%     -1.5%     -0.5%     -0.5%     +0.0%
          expert          -1.3%     -0.2%      0.00      0.00     +0.0%
          n-body          -1.1%     -0.2%     +0.1%     +0.1%     +0.0%
         veritas          -2.9%     -0.1%      0.00      0.00     +0.0%
 --------------------------------------------------------------------------------
             Min          -2.9%     -4.6%     -7.4%     -7.4%    -19.8%
             Max          -1.0%     +0.0%     +5.2%     +5.1%    +10.0%
  Geometric Mean          -1.2%     -0.1%     +0.5%     +0.5%     -0.1%

 I /think/ all this is due to this error-floating change; but it's possible
 that some was due to commit "Fix CSE (again) on literal strings" a couple
 of commits earlier.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13369#comment:1>
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