[GHC] #1371: Add -O3

[GHC]

#1371: Add  -O3
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        Reporter:           |            Owner:
  simonmar                  |           Status:  new
            Type:  task     |        Milestone:  _|_
        Priority:  normal   |          Version:  6.6.1
       Component:           |         Keywords:
  Compiler                  |     Architecture:  Unknown/Multiple
      Resolution:           |       Difficulty:  Moderate (less than a day)
Operating System:           |       Blocked By:
  Unknown/Multiple          |  Related Tickets:
 Type of failure:           |
  None/Unknown              |
       Test Case:           |
        Blocking:           |
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Comment (by schyler):

 I keep seeing people use -O2 -optlo -O3 when using -fllvm. Maybe this is
 worth taking a look at, if anything, just to bump up some base numbers and
 increase the llvm optimisation level in a more friendly way.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/1371#comment:9>
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