<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Make foldl's inline phased, and see what happens?<br><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
Presumably the reason it doesn't have a phase limit yet is that it never participated in any fusion before, so there was never a reason to not just inline.<br><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">
Other than that it seems like:<br><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> reverse xs<br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> => rewrite<br>
</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> build (\c n -> foldl (noinlineFlip c) n xs)<br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> => inline<br>
</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> foldl (noinlineFlip (:)) [] xs<br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> => rewrite<br>
</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"> reverse xs<br><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">where I assume you need a special flip which may or may not exist in these modules already.<br>
</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Aug 15, 2014 at 12:46 PM, David Feuer <span dir="ltr"><<a href="mailto:david.feuer@gmail.com" target="_blank">david.feuer@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">Yes, but I'm not sure how to do that, especially because foldl doesn't have the phased NOINLINE that foldr does.</p>
<div class="HOEnZb"><div class="h5">
<div class="gmail_quote">On Aug 15, 2014 12:45 PM, "Dan Doel" <<a href="mailto:dan.doel@gmail.com" target="_blank">dan.doel@gmail.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Isn't this kind of thing fixed for other functions by rewriting back into the direct recursive definition if no fusion happens?</div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Fri, Aug 15, 2014 at 11:41 AM, David Feuer <span dir="ltr"><<a href="mailto:david.feuer@gmail.com" target="_blank">david.feuer@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p dir="ltr">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.</p>
<div class="gmail_quote">On Aug 15, 2014 10:58 AM, "GHC" <<a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
#9434: GHC.List.reverse does not fuse<br>
-------------------------------------+-------------------------------------<br>
Reporter: dfeuer | Owner:<br>
Type: bug | Status: new<br>
Priority: normal | Milestone:<br>
Component: | Version: 7.9<br>
libraries/base | Keywords:<br>
Resolution: | Architecture: Unknown/Multiple<br>
Operating System: | Difficulty: Easy (less than 1<br>
Unknown/Multiple | hour)<br>
Type of failure: Runtime | Blocked By:<br>
performance bug | Related Tickets:<br>
Test Case: |<br>
Blocking: |<br>
Differential Revisions: |<br>
-------------------------------------+-------------------------------------<br>
<br>
Comment (by simonpj):<br>
<br>
Great. Just check that when fusion ''doesn't'' take place, the result is<br>
good. And do a `nofib` comparison for good luck. Then submit a patch.<br>
<br>
Thanks for doing all this work on fusion, David.<br>
<br>
Simon<span><font color="#888888"><br>
<br>
--<br>
Ticket URL: <<a href="http://ghc.haskell.org/trac/ghc/ticket/9434#comment:2" target="_blank">http://ghc.haskell.org/trac/ghc/ticket/9434#comment:2</a>><br>
GHC <<a href="http://www.haskell.org/ghc/" target="_blank">http://www.haskell.org/ghc/</a>><br>
The Glasgow Haskell Compiler<br>
</font></span></blockquote></div>
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