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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">You might also find compiler/ghci/RtClosureInspect.hs useful.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">It’s the main module of the GHCi debugger, and allows Haskell code to inspect the Haskell heap. So it has mechanisms for unpacking arbitrary closures, all in Haskell.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">It’s tough going though. It was written a long time ago by Pepe Iborra (in a GSoC project), and has not received much love since. Maybe you could be a source of love?!<o:p></o:p></span></p>
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<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"> Libraries <libraries-bounces@haskell.org>
<b>On Behalf Of </b>Andrew Martin<br>
<b>Sent:</b> 06 February 2019 20:57<br>
<b>To:</b> Matthew Pickering <matthewtpickering@gmail.com><br>
<b>Cc:</b> Haskell Libraries <libraries@haskell.org><br>
<b>Subject:</b> Re: Peeking into StgInfoTable in cmm<o:p></o:p></span></p>
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<p class="MsoNormal">Or even better, it looks like cmmGetClosureType already combines the two for me.<o:p></o:p></p>
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<p class="MsoNormal">On Wed, Feb 6, 2019 at 3:49 PM Andrew Martin <<a href="mailto:andrew.thaddeus@gmail.com">andrew.thaddeus@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Thanks. The source code of ghc-heap has led me to what I was looking for. That whole library hinges upon unpackClosure# (stg_unpackClosurezh), whose implementation opens with the telling:<o:p></o:p></p>
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<p class="MsoNormal"> info = %GET_STD_INFO(UNTAG(closure));<o:p></o:p></p>
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<p class="MsoNormal">In CmmParse.y, we find the implementation of GET_STD_INFO, and just a few lines below is the INFO_TYPE macro. The combination of these (along with a cmm implementation of UNTAG, which I am still unsure of exactly how to accomplish) should
do the trick.<o:p></o:p></p>
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<p class="MsoNormal">On Wed, Feb 6, 2019 at 2:53 PM Matthew Pickering <<a href="mailto:matthewtpickering@gmail.com" target="_blank">matthewtpickering@gmail.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal">Unless I am misunderstanding you want something which works like ghc-heap.<br>
<br>
If so, perhaps these three files will be instructive?<br>
<br>
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2Fblob%2Fmaster%2Flibraries%2Fghc-heap%2FGHC%2FExts%2FHeap%2FInfoTable.hsc&data=02%7C01%7Csimonpj%40microsoft.com%7C06915c8ff0cf44831aa208d68c75bb48%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636850834616930861&sdata=7AOF4PAMQw7jFWNo0t6Hq4tWiT%2FOscQ40xm25gag6Ys%3D&reserved=0" target="_blank">https://gitlab.haskell.org/ghc/ghc/blob/master/libraries/ghc-heap/GHC/Exts/Heap/InfoTable.hsc</a><br>
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2Fblob%2Fmaster%2Flibraries%2Fghc-heap%2FGHC%2FExts%2FHeap%2FInfoTableProf.hsc&data=02%7C01%7Csimonpj%40microsoft.com%7C06915c8ff0cf44831aa208d68c75bb48%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636850834616930861&sdata=YzGRBEBOVYFNdAQdfEk2wZqJ7t3vJW7VFs0B%2FfNY7ik%3D&reserved=0" target="_blank">https://gitlab.haskell.org/ghc/ghc/blob/master/libraries/ghc-heap/GHC/Exts/Heap/InfoTableProf.hsc</a><br>
<a href="https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.haskell.org%2Fghc%2Fghc%2Fblob%2Fmaster%2Flibraries%2Fghc-heap%2FGHC%2FExts%2FHeap%2FClosures.hs%23L25&data=02%7C01%7Csimonpj%40microsoft.com%7C06915c8ff0cf44831aa208d68c75bb48%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636850834616940859&sdata=%2FrzmmYNnEBkPeFPMiwaerspjuOxJKI4B519Ev041zN4%3D&reserved=0" target="_blank">https://gitlab.haskell.org/ghc/ghc/blob/master/libraries/ghc-heap/GHC/Exts/Heap/Closures.hs#L25</a><br>
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Cheers,<br>
<br>
Matt<br>
<br>
On Wed, Feb 6, 2019 at 7:29 PM Andrew Martin <<a href="mailto:andrew.thaddeus@gmail.com" target="_blank">andrew.thaddeus@gmail.com</a>> wrote:<br>
><br>
> For an optimization I’m implementing, I’m trying to write an inline primop that gives me lets me inspect the closure type of an arbitrary heap-allocated value. I’m close to figuring this out, and the FCode machinery is starting to make sense, but one thing
eludes me. Starting from a StgHeader, I get the info table pointer. This is easy since it’s the first field in the struct. But next I have to deference the info table pointer and get the closure type. There are two fields at the beginning of an info table
that may or may not be present. I don’t know how to figure out if they are present or not. I suspect that there is something I can get out of DynFlags that tells me this, but I can’t find anything else in the stg-to-cmm pass that reads from an info table.<br>
><br>
> Sent from my iPhone<br>
> _______________________________________________<br>
> Libraries mailing list<br>
> <a href="mailto:Libraries@haskell.org" target="_blank">Libraries@haskell.org</a><br>
> <a href="https://nam06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fmail.haskell.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Flibraries&data=02%7C01%7Csimonpj%40microsoft.com%7C06915c8ff0cf44831aa208d68c75bb48%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636850834616940859&sdata=7%2Fc3qcuTEGeUjd9lG%2FXYVnb3bZ8%2B61jEf4XidnEgfUw%3D&reserved=0" target="_blank">
http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries</a><o:p></o:p></p>
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<p class="MsoNormal">-Andrew Thaddeus Martin<o:p></o:p></p>
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<p class="MsoNormal">-Andrew Thaddeus Martin<o:p></o:p></p>
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