[GHC] #14226: Common Block Elimination pass doesn't eliminate common blocks

[GHC]

#14226: Common Block Elimination pass doesn't eliminate common blocks
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  michalt
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.1
  (CodeGen)                          |             Keywords:  newcomer,
      Resolution:                    |  CodeGen
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9157, #14754     |  Differential Rev(s):  Phab:D3973,
       Wiki Page:                    |  Phab:D3999
-------------------------------------+-------------------------------------

Comment (by Ben Gamari <ben@…>):

 In [changeset:"4e513bf758c32804fc71b98215f96e8481697a36/ghc" 4e513bf/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="4e513bf758c32804fc71b98215f96e8481697a36"
 CBE: re-introduce bgamari's fixes

 During some recent work on CBE we discovered that `zipWith` is used to
 check for equality, but that doesn't quite work if lists are of
 different lengths! This was fixed by bgamari, but unfortunately the fix
 had to be rolled back due to other changes in CBE in
 50adbd7c5fe5894d3e6e2a58b353ed07e5f8949d. Since I wanted to have another
 look at CBE anyway, we agreed that the first thing to do would be to
 re-introduce the fix.

 Sadly I don't have any actual test case that would exercise this.

 Signed-off-by: Michal Terepeta <michal.terepeta at gmail.com>

 Test Plan: ./validate

 Reviewers: bgamari, simonmar

 Reviewed By: bgamari

 Subscribers: rwbarton, thomie, carter

 GHC Trac Issues: #14226

 Differential Revision: https://phabricator.haskell.org/D4387
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14226#comment:32>
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