[GHC] #10170: Find versioned versions of LLVM tools

[GHC]

#10170: Find versioned versions of LLVM tools
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        Reporter:  erikd             |                   Owner:  erikd
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler (LLVM)   |                 Version:  7.11
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  None/Unknown      |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
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Comment (by rwbarton):

 > More importantly configure should fail if whatever version of llc it
 finds isn't the currently blessed version.

 Right.

 > Yes, it should look for a versioned `/usr/lib/llc-X.Y` but also accept
 `/usr/lib/llvm-3.6/bin/llc`

 Let me rephrase what I meant. Hard-coding knowledge of the directory
 `/usr/lib/llvm-3.6/bin` into ghc's autoconf is wrong because (in my
 estimation) the fact that `llc-3.6` is a symlink to
 `/usr/lib/llvm-3.6/bin/llc` is an implementation detail of the Debian
 `llvm-3.6` package and the executable may be (and is) located elsewhere on
 other distributions. The public interface of `llvm-3.6` (on Debian and
 hopefully on other distributions) is that it provides `llc-3.6` on the
 standard `$PATH`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10170#comment:7>
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