[GHC] #14998: Sort out the strictness mess for exceptions

[GHC]

#14998: Sort out the strictness mess for exceptions
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.3
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  Exceptions
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgraf):

 Ah, `-ddump-prep` revealed that the non-trivial argument to `catch#` on
 non-HEAD was turned into a one-shot PAP `sat = act h`, which allocates. Of
 course! That's probably where the alleged benefit of item 3 came from.
 Indeed `reverse-complement` and `spheres` where the biggest beneficiaries,
 judging from the commit message.

 So, we need to be strict in `act h` because otherwise it will turn into a
 lazy let that allocates.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14998#comment:16>
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