[GHC] #9646: Strange performance bug

[GHC]

#9646: Strange performance bug
-------------------------------------+-------------------------------------
              Reporter:  erikd       |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:  Linux       |     Architecture:  x86_64 (amd64)
       Type of failure:  Runtime     |       Difficulty:  Unknown
  performance bug                    |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Changes (by erikd):

 * os:  Unknown/Multiple => Linux
 * architecture:  Unknown/Multiple => x86_64 (amd64)


Comment:

 @jstolarek : It looks you you do not have the criterion library installed.

 @dferuer :
 * Changing the order of the benchmarks makes no difference, the New3* runs
 still exhibit the same behaviour.
 * The `make` program is not a factor. I can take the commands printed
 using `make -n` and put them in a shell script for the same result.
 * Running the benchmarking program separately from the compile process
 gives almost identical results.

 I've also assured myself that the ghc command:

 {{{
 ghc -Wall -Werror -fwarn-tabs -fPIC
     -ddump-to-file -ddump-prep -ddump-cmm -ddump-opt-cmm -ddump-stg
 -ddump-asm
     -O3 -XCPP -XMagicHash -XUnboxedTuples -XUnliftedFFITypes
     --make bench-integer.hs -o bench-integer
 }}}

 is the same in both cases. This is to be expected as `make` really just
 calls this `ghc --make` command.

 Behaviour is also the same with `-O2` and `-O1`. I tried compiling with
 `-O0` which gave radically different results but there were no interesting
 conclusions to be drawn.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9646#comment:3>
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