[GHC] #13535: vector test suite uses excessive memory on GHC 8.2

[GHC]

#13535: vector test suite uses excessive memory on GHC 8.2
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10800            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Indeed in most phases of simplification the program with all testcases
 enabled is roughly three to five times larger in `master` than it was in
 `8.0.2`. After CorePrep, however, the program is nearly a factor of 8
 larger,
 {{{
 # 8.0.2
 Result size of CorePrep
   = {terms: 118,005, types: 138,524, coercions: 50,256}

 # master
 Result size of CorePrep
   = {terms: 796,181,
      types: 907,739,
      coercions: 1,094,846,
      joins: 3,382/34,300}
 }}}

 It may also be interesting to note that if you sum the allocations of all
 of the testcases individually, you get something a bit higher than the
 allocations required to compile the "everything" case. I wonder if

 So, there are two (possibly related) questions here:

 1. Why did the Core get so much larger from 8.0 to 8.2?
 2. How was GHC 8.0 able to compile the "everything" case with less than a
 factor of two of the allocations of the individual cases, while 8.2
 requires a factor of five?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13535#comment:8>
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