[GHC] #14372: CMM contains a bunch of tail-merging opportunities

[GHC]

#14372: CMM contains a bunch of tail-merging opportunities
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        Reporter:  heisenbug         |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      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 simonpj):

 It's hard to review code without a spec, or even some input/output
 examples.

 And an overview Note to explain the goal and how the impl works would be
 useful.

 Based on a very quick look, it seems that you hope to branch from one
 `CmmProc` to a label in another.  That's a huge thing to do, because it
 messes up all dataflow analyses, which expect to be able to see all the
 places that jump to a block (e.g. constant propagation).  I'm 99% sure
 that you can't translate it into LLVM.

 Before you invest a lot more effort, can we debate the goal?  There are
 others on ghc-devs who know about this back-end stuff.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14372#comment:10>
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