[GHC] #14626: No need to enter a scrutinised value

[GHC]

#14626: No need to enter a scrutinised value
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        Reporter:  heisenbug         |                Owner:  heisenbug
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  performance
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #13861            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by heisenbug):

 Replying to [comment:15 alexbiehl]:
 > Indeed GHC seems to unnecessarily enter `MkT`s argument!
 >
 > {{{
 >     ...
 > c1ab: // global
 >    R1 = P64[R1 + 7] & (-8); -- load xs and untag(!) it
 >    Sp = Sp + 8;
 >    call (I64[R1])(R1) args: 8, res: 0, upd: 8; -- and enter it!
 > }}}

 Yes, my branch is supposed to fix (soon) many (if not all) of these cases.
 Simon fixed the lost tracking of ''evaled-ness'' in core-prep already, now
 I am building on that patch. Which GHC do you use to check? My branch
 currently won't bootstrap, so you can only do your experiments with
 `stage1` (or roll your own modifications).

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14626#comment:16>
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