[GHC] #8996: mark more things as const in C codegen

[GHC]

#8996: mark more things as const in C codegen
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        Reporter:  slyfox            |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.2
  (CodeGen)                          |         Keywords:
      Resolution:                    |     Architecture:  Unknown/Multiple
Operating System:  Unknown/Multiple  |       Difficulty:  Easy (less than 1
 Type of failure:  None/Unknown      |  hour)
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by ezyang):

 I think the intent is good.  However, I'd probably go about doing it
 slightly differently: we want this to apply to all read-only data (so
 `ReadOnlyData`, `RelocatableReadOnlyData` and `ReadOnlyData16`), so it
 sounds like what you should do is go through all the PprC branches looking
 for places where a 'const' could be inserted, and then check if the
 relevant section is readonly.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8996#comment:1>
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