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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:36.0pt">
But now that this has been brought up: currently, does adding an {-# INLINE op #-} (with or without phase) for a class op actually do anything?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
Currently it does nothing, I think, and therefore should perhaps be rejected today. So I hope no one is doing that. Worth double checking:<o:p></o:p></p>
<ul style="margin-top:0cm" type="disc">
<li class="MsoListParagraph" style="margin-top:6.0pt;margin-bottom:6.0pt;margin-left:2.5pt;mso-list:l1 level1 lfo7">
Hackage, to check that no one has INLINE on a method in a class decl<o:p></o:p></li><li class="MsoListParagraph" style="margin-top:6.0pt;margin-bottom:6.0pt;margin-left:2.5pt;mso-list:l1 level1 lfo7">
GHC, to check that an INLINE on method in a class decl is ignored.<o:p></o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
In contrast, an INLINE on an <b>instance decl</b> should mean that <b>that particular class op instance method</b> is inlined. I hope this works correctly today.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:36.0pt">
So I personally could live with a situation where it is controllable for each classop individually - and I'd do the work to get that in.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
OK. This is actually user facing, so I think the right thing is to write a short GHC Proposal. It needn’t take long to get approved. But it does get more eyes on it. And it provides a solid write up to refer to from the implementation.<o:p></o:p></p>
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You could draw on this thread for the raw material, so it would not be hard to write.<o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> Christiaan Baaij <christiaan.baaij@gmail.com>
<br>
<b>Sent:</b> 07 March 2020 08:53<br>
<b>To:</b> Simon Peyton Jones <simonpj@microsoft.com><br>
<b>Cc:</b> Conal Elliott <conal@conal.net>; ghc-devs <ghc-devs@haskell.org><br>
<b>Subject:</b> Re: Class op rules<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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Thanks for explaining Simon!<o:p></o:p></p>
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<o:p> </o:p></p>
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So I personally could live with a situation where it is controllable for each classop individually - and I'd do the work to get that in.<o:p></o:p></p>
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Where if the developer doesn't specify an INLINE pragma, it defaults to AlwaysActive.<o:p></o:p></p>
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That way, the change only affects users who have currently annotated their class op with an {-# INLINE[N] op #-}<o:p></o:p></p>
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(I would have to scour hackage to see if anyone has currently doing that... I hope not...)<o:p></o:p></p>
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<o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
But now that this has been brought up: currently, does adding an {-# INLINE op #-} (with or without phase) for a class op actually do anything?<o:p></o:p></p>
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Or is it basically superfluous because the class op already gets a BuiltInRule that's equal to INLINE AlwaysActive?<o:p></o:p></p>
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Or does it affect whether a default implementation for the method gets inlined into the dictionary?<o:p></o:p></p>
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If the latter, I guess we should use SPECIALIZE instead of INLINE for controlling the rule phase of the class op... unless that SPECIALIZE also has an effect on the class op default implementation...<o:p></o:p></p>
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<o:p> </o:p></p>
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Thanks,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
Christiaan<o:p></o:p></p>
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<o:p> </o:p></p>
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<o:p> </o:p></p>
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On Sat, 7 Mar 2020 at 00:02, Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com">simonpj@microsoft.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Here’s how it works:<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l4 level1 lfo1">
The rewrite from opi (D m1 … mn) <span style="font-family:Wingdings">à</span> mi<o:p></o:p></li></ul>
<p class="gmail-m-8459479282043687378msolistparagraph">is done by a BuiltinRule: see MkId.mkDictSelId, and the BuiltinRule that is made there.<o:p></o:p></p>
<p class="gmail-m-8459479282043687378msolistparagraph"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l6 level1 lfo2">
At the moment, BuiltinRules are always active (in all phases), see GHC.Core.ruleActivation. To allow them to be selectively active, we’d have to give them a ru_act fiels, like ordinary Rules. That would not be hard.<o:p></o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l5 level1 lfo3">
The phases go<o:p></o:p></li></ul>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l5 level2 lfo3">
InitialPhase<o:p></o:p></li><li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l5 level2 lfo3">
2<o:p></o:p></li><li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l5 level2 lfo3">
1<o:p></o:p></li><li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l5 level2 lfo3">
0<o:p></o:p></li></ul>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l2 level1 lfo4">
We could make classop rules active only in phase 1 and 0, say. I don’t know what the consequences would be; running the classop to pick a method out of a dictionary in turn reveals new function applications that might want to work in phase 2, say.<o:p></o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l0 level1 lfo5">
Of course you can always add more phases, but that adds compile time.<o:p></o:p></li></ul>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<li class="gmail-m-8459479282043687378msolistparagraph" style="mso-list:l3 level1 lfo6">
Would you want the classop phase to be fixed for every classop? Or controllable for each classop individually. E.g. class C a where { op :: <bype> {-# INLINE [2] op #-} }<o:p></o:p></li></ul>
<p class="gmail-m-8459479282043687378msolistparagraph">Here the intent is that, since the pragmas is in the class decl, the pragma applies to the method selector.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">I remember Conal raising this before, but I’ve forgotten the resolution. I’m entirely open to changes here, if someone is willing to do the work, including checking for consequences.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Simon<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> ghc-devs <<a href="mailto:ghc-devs-bounces@haskell.org" target="_blank">ghc-devs-bounces@haskell.org</a>>
<b>On Behalf Of </b>Conal Elliott<br>
<b>Sent:</b> 06 March 2020 17:37<br>
<b>To:</b> Christiaan Baaij <<a href="mailto:christiaan.baaij@gmail.com" target="_blank">christiaan.baaij@gmail.com</a>><br>
<b>Cc:</b> ghc-devs <<a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a>><br>
<b>Subject:</b> Re: Class op rules</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">Thank you for raising this issue, Christiaan! The current policy (very early class-op inlining) is a major difficulty and the main source of fragility in my compiling-to-categories implementation.
I have a tediously programmed and delicately balanced collection of techniques to intercept and transform class ops to non-ops early and then transform back late for elimination, but it doesn't work in all situations. Since class operations roughly correspond
to operations in various algebraic abstractions---interfaces with laws---I often want to exploit exactly those laws as rewrite rules, and yet those rules currently cannot be used dependably. - Conal<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">On Fri, Mar 6, 2020 at 7:22 AM Christiaan Baaij <<a href="mailto:christiaan.baaij@gmail.com" target="_blank">christiaan.baaij@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">Hello,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">The other day I was experimenting with RULES and got this warning:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">src/Clash/Sized/Vector.hs:2159:11: warning: [-Winline-rule-shadowing]<br>
Rule "map Pack" may never fire<br>
because rule "Class op pack" for ‘pack’ might fire first<br>
Probable fix: add phase [n] or [~n] to the competing rule<br>
|<br>
2159 | {-# RULES "map Pack" map pack = id #-}<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">The warning seems to suggests two things:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">1. "Class op" -> "dictionary projection" are implemented as rewrite rules and executed the same way as other user-defined RULES<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">2. These rules run first, and you cannot run anything before them<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">Now my question is, is 1. actually true? or is that warning just a (white) lie?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">If 1. is actually true, would there be any objections to adding a "-1" phase: where RULES specified to start from phase "-1" onward fire before any of the Class op rules.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">I'm quite willing to implement the above if A) Class op rules are actually implemented as builtin RULES; B) there a no objections to this "-1" phase.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">Thanks,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">Christiaan<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;margin-bottom:6.0pt">_______________________________________________<br>
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