[GHC] #10717: fannkuch-redux allocations increase by factor of 10000 between 7.4.2 and 7.6.3

[GHC]

#10717: fannkuch-redux allocations increase by factor of 10000 between 7.4.2 and
7.6.3
-------------------------------------+-------------------------------------
        Reporter:  bgamari           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  7.6.3
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by bgamari):

 I'm now looking at the ticky output from the testcase run with argument
 `11` after having confirmed that compiling with `-prof` kills the effect
 (both compilers produce executables which allocate heavily).

 The ticky output shows a pretty clear difference.

 == 7.6 ==
 {{{
 ENTERS: 1178454454  of which 1178454454 (100.0%) direct to the entry code
                   [the rest indirected via Node's info ptr]
 36288010 (  3.1%) thunks
       0 (  0.0%) data values
       0 (  0.0%) normal indirections
       0 (  0.0%) permanent indirections

 ...

 RETURNS: 354136250
 36288000 ( 10.2%) from entering a new constructor
                   [the rest from entering an existing constructor]

 UPDATE FRAMES: 36288007 (0 omitted from thunks)
 ...

     Entries     Allocs  Arity Stack    Kinds      Function
 --------------------------------------------------------------------------------
 ...
    39916804  108864012      4     0    iiiA       $wa3{v s3Cl} (main:Main)
 }}}

 == 7.4 ==
 {{{
 ENTERS: 1142166456  of which 1142166456 (100.0%) direct to the entry code
                   [the rest indirected via Node's info ptr]
      10 (  0.0%) thunks
       0 (  0.0%) data values
       0 (  0.0%) normal indirections
       0 (  0.0%) permanent indirections

 ...

 RETURNS: 317848252
       0 (  0.0%) from entering a new constructor
                   [the rest from entering an existing constructor]

 UPDATE FRAMES: 7 (0 omitted from thunks)
 ...

     Entries     Allocs  Arity Stack    Kinds      Function
 --------------------------------------------------------------------------------
 ...
    39916804         12      4     0    iiiA       $wa3{v s3ad} (main:Main)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10717#comment:3>
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