[GHC] #9577: String literals are wasting space

[GHC]

#9577: String literals are wasting space
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              Reporter:  xnyhps      |            Owner:  xnyhps
                  Type:  bug         |           Status:  new
              Priority:  low         |        Milestone:
             Component:  Compiler    |          Version:  7.8.2
  (NCG)                              |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Unknown
  Unknown/Multiple                   |       Blocked By:
       Type of failure:  Runtime     |  Related Tickets:
  performance bug                    |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by dfeuer):

 Replying to [comment:3 xnyhps]:
 > The main argument in favor of alignment seems to be: code often
 `memcpy`s string literals into buffers. By doing that with aligned
 addresses (apparently) SSE instructions can be used. This is irrelevant
 for GHC, because the strings are only parsed into `[Char]`s, never copied.

 Will that always be the case if a string literal represents something like
 `Text` or `ByteString`? If so, will that continue to hold in the future?
 Might a future optimization fuse `putStr` with the conversion to do a
 copy? It may be that these concerns are baseless, but it might make sense
 to consider what alternative optimizations yours could preclude.

 You mention that there are a lot of string literals in the Prelude. I
 would bet that the vast majority of those are error messages. Might it be
 possible to specifically target ''exceptional'' strings that should never
 be anywhere speed-critical, and pack them all together? Putting them all
 together, ideally starting or ending on a page boundary, would (hopefully)
 mean that they wouldn't even need to be swapped in unless an error
 occurred.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9577#comment:4>
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