[GHC] #15188: Catch cases where both branches of an if jump to the same block.

[GHC]

#15188: Catch cases where both branches of an if jump to the same block.
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        Reporter:  AndreasK          |                Owner:  AndreasK
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
  (CodeGen)                          |
      Resolution:                    |             Keywords:  CodeGen
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D4740
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"efea32cf2c41d35f2ba5a79bf70cc7768b7b0fd5/ghc"
 efea32cf/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="efea32cf2c41d35f2ba5a79bf70cc7768b7b0fd5"
 Check if both branches of an Cmm if have the same target.

 This for some reason or the other and makes it into the final
 binary. I've added the check to ContFlowOpt as that seems
 like a logical place for this.

 In a regular nofib run there were 30 occurences of this pattern.

 Test Plan: ci

 Reviewers: bgamari, simonmar, dfeuer, jrtc27, tdammers

 Reviewed By: bgamari, simonmar

 Subscribers: tdammers, dfeuer, rwbarton, thomie, carter

 GHC Trac Issues: #15188

 Differential Revision: https://phabricator.haskell.org/D4740
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15188#comment:4>
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