[GHC] #9434: GHC.List.reverse does not fuse

[Dan Doel]

Isn't this kind of thing fixed for other functions by rewriting back into
the direct recursive definition if no fusion happens?


On Fri, Aug 15, 2014 at 11:41 AM, David Feuer <david.feuer at gmail.com> wrote:

> I'm having trouble when it doesn't fuse—it ends up with duplicate bindings
> at the top level, because build gets inlined n times, and the result lifted
> out. Nothing's *wrong* with the code, except that there are multiple copies
> of it.
> On Aug 15, 2014 10:58 AM, "GHC" <ghc-devs at haskell.org> wrote:
>
>> #9434: GHC.List.reverse does not fuse
>>
>> -------------------------------------+-------------------------------------
>>               Reporter:  dfeuer      |            Owner:
>>                   Type:  bug         |           Status:  new
>>               Priority:  normal      |        Milestone:
>>              Component:              |          Version:  7.9
>>   libraries/base                     |         Keywords:
>>             Resolution:              |     Architecture:  Unknown/Multiple
>>       Operating System:              |       Difficulty:  Easy (less than
>> 1
>>   Unknown/Multiple                   |  hour)
>>        Type of failure:  Runtime     |       Blocked By:
>>   performance bug                    |  Related Tickets:
>>              Test Case:              |
>>               Blocking:              |
>> Differential Revisions:              |
>>
>> -------------------------------------+-------------------------------------
>>
>> Comment (by simonpj):
>>
>>  Great.  Just check that when fusion ''doesn't'' take place, the result is
>>  good. And do a `nofib` comparison for good luck. Then submit a patch.
>>
>>  Thanks for doing all this work on fusion, David.
>>
>>  Simon
>>
>> --
>> Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9434#comment:2>
>> GHC <http://www.haskell.org/ghc/>
>> The Glasgow Haskell Compiler
>>
>
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