[GHC] #4213: LLVM: Add support for TNTC to LLVM compiler suite

[GHC]

#4213: LLVM: Add support for TNTC to LLVM compiler suite
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        Reporter:  dterei            |            Owner:  dterei
            Type:  feature request   |           Status:  new
        Priority:  low               |        Milestone:  7.6.2
       Component:  Compiler (LLVM)   |          Version:  6.13
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by bgamari):

 Looking at the semantics of LLVM's prefix data concept, it seems like it
 doesn't map terribly well on to our use-case. Namely, the `prefix`
 attribute allows you to prepend arbitrary data to the beginning of the
 symbol's definition. While we would want LLVM to place the symbol's
 address after info table, naive use of prefix data would produce symbols
 pointing at the beginning of each function's info table.

 The documentation suggests that this is supposed to be worked around by
 beginning the prefix data with a trampoline to jump to the true beginning
 of the symbol. Given we already have a hack that works, I don't see any
 good reason to implement this hack.

 However, when used with another pending LLVM
 [feature](http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-April/061511.html)
 allowing an offset to be applied to a symbol's address prefix data will
 become much more useful. I suggest we hold off on using LLVM's prefix data
 until this has been implemented. Unfortunately, it seems that the proposal
 is more than a year old with no activity but I can try to resuscitate it.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4213#comment:12>
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