[GHC] #11649: LLVM code generator produces mal-formed LLVM blocks

[GHC]

#11649: LLVM code generator produces mal-formed LLVM blocks
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                Owner:  erikd
            Type:  bug               |               Status:  patch
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler          |              Version:  8.0.1-rc2
  (CodeGen)                          |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash                              |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9043             |  Differential Rev(s):  Phab:D1996
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"92821ec9a57817e1429ae94c756539259488b728/ghc"
 92821ec9/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="92821ec9a57817e1429ae94c756539259488b728"
 LlvmCodeGen: Fix generation of malformed LLVM blocks

 Commit 673efccb3b uncovered a bug in LLVM code generation that produced
 LLVM code that the LLVM compiler refused to compile:

     {
     clpH:
       br label %clpH
     }

 This may well be a bug in LLVM itself. The solution is to keep the
 existing entry label and rewrite the function as:

     {
     clpH:
       br label %nPV
     nPV:
       br label %nPV
     }

 Thanks to Ben Gamari for pointing me in the right direction on this
 one.

 Test Plan: Build GHC with BuildFlavour=quick-llvm

 Reviewers: hvr, austin, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1996

 GHC Trac Issues: #11649
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11649#comment:13>
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