[GHC] #13763: Performance regression (~34%) in 8.2.1, poor register allocation(?) in an inner loop over an array

[GHC]

#13763: Performance regression (~34%) in 8.2.1, poor register allocation(?) in an
inner loop over an array
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        Reporter:  jberryman         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (NCG)    |              Version:  8.2.1-rc2
      Resolution:                    |             Keywords:  JoinPoints
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * cc: kavon@… (added)


Comment:

 I'm puzzled. The changes in comment:3 change `letrec` into `joinrec`,
 which ought to be a straight win.

 I'm adding Kavon in cc because he is interested in this back-end stuff.

 More insight into where the regression comes from would be helpful, if
 anyone has time to dig in.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13763#comment:5>
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