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<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
* To access an unfolding, is `maybeUnfoldingTemplate (idUnfolding v)` the recommended recipe?<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">You can see by looking at the code that idUnfolding returns nothing for a loop breaker. You have to decide if that’s what you want; if not, use realIdUnfolding.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
* Is it the case that this recipe succeeds (`Just`) in some compiler phases and not others?<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">It fails for loop breakers. An Id might be a loop breaker in some phases but not others; e.g. the loop might be broken by some optimisation.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal" style="mso-margin-top-alt:6.0pt;margin-right:0cm;margin-bottom:6.0pt;margin-left:0cm">
* Before an Id is ready for general inlining by the simplifier, can I get the Id's unfolding another way so that I can substitute it early?<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">realIdUnfolding always works. As the code shows<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="Code">idUnfolding :: Id -> Unfolding<o:p></o:p></p>
<p class="Code">-- Do not expose the unfolding of a loop breaker!<o:p></o:p></p>
<p class="Code">idUnfolding id<o:p></o:p></p>
<p class="Code"> | isStrongLoopBreaker (occInfo info) = NoUnfolding<o:p></o:p></p>
<p class="Code"> | otherwise = unfoldingInfo info<o:p></o:p></p>
<p class="Code"> where<o:p></o:p></p>
<p class="Code"> info = idInfo id<o:p></o:p></p>
<p class="Code"><o:p> </o:p></p>
<p class="Code">realIdUnfolding :: Id -> Unfolding<o:p></o:p></p>
<p class="Code">-- Expose the unfolding if there is one, including for loop breakers<o:p></o:p></p>
<p class="Code">realIdUnfolding id = unfoldingInfo (idInfo id)<o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Does that help?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif">Simon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> conal.elliott@gmail.com [mailto:conal.elliott@gmail.com]
<b>On Behalf Of </b>Conal Elliott<br>
<b>Sent:</b> 02 December 2016 18:13<br>
<b>To:</b> Simon Peyton Jones <simonpj@microsoft.com><br>
<b>Cc:</b> ghc-devs@haskell.org<br>
<b>Subject:</b> Re: How to inline early in a GHC plugin?<o:p></o:p></span></p>
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<p class="MsoNormal"><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">
Thanks for the pointers, Simon. Some more specific questions:<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">
* To access an unfolding, is `maybeUnfoldingTemplate (idUnfolding v)` the recommended recipe?<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">
* Is it the case that this recipe succeeds (`Just`) in some compiler phases and not others?<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">
If so, is this difference due to Ids being altered (presumably via `setUnfoldingInfo` being called between phases)?<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">
* Before an Id is ready for general inlining by the simplifier, can I get the Id's unfolding another way so that I can substitute it early?<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">
A short Skype chat might easily clear up my questions and confusions if you have time and inclination.<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">
Regards, - Conal<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">
On Fri, Dec 2, 2016 at 9:07 AM, Simon Peyton Jones <<a href="mailto:simonpj@microsoft.com" target="_blank">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"><span style="font-family:"Calibri",sans-serif">I don’t really understand your question clearly. So I’ll guess</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif">Unfoldings are added to Ids in Simplify.completeBind (look for setUnfoldingInfo). Apart from INLINE pragmas, that’s about the only
place it happens. </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif">Does that help?</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif">S</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-family:"Calibri",sans-serif"> </span><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" style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif"> ghc-devs
[mailto:<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> 01 December 2016 21:51<br>
<b>To:</b> <a href="mailto:ghc-devs@haskell.org" target="_blank">ghc-devs@haskell.org</a><br>
<b>Subject:</b> How to inline early in a GHC plugin?</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">I'm implementing a GHC plugin that installs a `BuiltInRule` that does the work, and I'd like to learn how to inline more flexibly. Given an identifier `v`, I'm using `maybeUnfoldingTemplate
(realIdUnfolding v)` to get a `Maybe CoreExpr`. Sometimes this recipe yields `Nothing` until a later compiler phase. Meanwhile, I guess my variable `v` has been replaced by one with inlining info. First, am I understanding this mechanism correctly? A GHC source
pointer to how inlining is made available would help me. Second, can I access the inlining info before it's made available to the rest of the simplifier?<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, - Conal<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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