[GHC] #15445: SPECIALIZE one of two identical functions does not fire well

[GHC]

#15445: SPECIALIZE one of two identical functions does not fire well
-------------------------------------+-------------------------------------
        Reporter:  nobrakal          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
                                     |  simplCore/should_compile/T15445
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Ben had to revert this patch
 {{{
 Revert "Don't inline functions with RULES too early"
 author  Ben Gamari <ben at smart-cactus.org>
         Wed, 1 Aug 2018 11:42:19 +0100 (06:42 -0400)
 committer       Ben Gamari <ben at smart-cactus.org>
         Wed, 1 Aug 2018 11:54:23 +0100 (06:54 -0400)
 This commit causes significant performance regressions:
 ```
 bytes allocated value is too high:
     Expected    T9872d(normal) bytes allocated: 578498120 +/-5%
     Lower bound T9872d(normal) bytes allocated: 549573214
     Upper bound T9872d(normal) bytes allocated: 607423026
     Actual      T9872d(normal) bytes allocated: 677179968
     Deviation   T9872d(normal) bytes allocated:      17.1 %
 bytes allocated value is too high:
     Expected    T9872c(normal) bytes allocated: 3096670112 +/-5%
     Lower bound T9872c(normal) bytes allocated: 2941836606
     Upper bound T9872c(normal) bytes allocated: 3251503618
     Actual      T9872c(normal) bytes allocated: 3601872536
     Deviation   T9872c(normal) bytes allocated:       16.3 %
 bytes allocated value is too high:
     Expected    T9872b(normal) bytes allocated: 3730686224 +/-5%
     Lower bound T9872b(normal) bytes allocated: 3544151912
     Upper bound T9872b(normal) bytes allocated: 3917220536
     Actual      T9872b(normal) bytes allocated: 4374298272
     Deviation   T9872b(normal) bytes allocated:       17.3 %
 bytes allocated value is too high:
     Expected    T9872a(normal) bytes allocated: 2729927408 +/-5%
     Lower bound T9872a(normal) bytes allocated: 2593431037
     Upper bound T9872a(normal) bytes allocated: 2866423779
     Actual      T9872a(normal) bytes allocated: 3225788896
     Deviation   T9872a(normal) bytes allocated:       18.2 %
 ```
 It's not clear that this was intentional so I'm going to revert for now.

 This reverts commit 2110738b280543698407924a16ac92b6d804dc36.

 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15445#comment:6>
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