<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=utf-8"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:105%;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.MsoListParagraphCxSpFirst, li.MsoListParagraphCxSpFirst, div.MsoListParagraphCxSpFirst
{mso-style-priority:34;
mso-style-type:export-only;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:105%;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.MsoListParagraphCxSpMiddle, li.MsoListParagraphCxSpMiddle, div.MsoListParagraphCxSpMiddle
{mso-style-priority:34;
mso-style-type:export-only;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:105%;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.MsoListParagraphCxSpLast, li.MsoListParagraphCxSpLast, div.MsoListParagraphCxSpLast
{mso-style-priority:34;
mso-style-type:export-only;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
margin-bottom:.0001pt;
mso-add-space:auto;
line-height:105%;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
.MsoChpDefault
{mso-style-type:export-only;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:1041441870;
mso-list-type:hybrid;
mso-list-template-ids:-119520174 134807567 134807555 134807557 134807553 134807555 134807557 134807553 134807555 134807557;}
@list l0:level1
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level2
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:"Courier New";}
@list l0:level3
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:Wingdings;}
@list l0:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:Symbol;}
@list l0:level5
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:"Courier New";}
@list l0:level6
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:Wingdings;}
@list l0:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:Symbol;}
@list l0:level8
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:"Courier New";}
@list l0:level9
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;
font-family:Wingdings;}
ol
{margin-bottom:0in;}
ul
{margin-bottom:0in;}
--></style></head><body lang=EN-US link=blue vlink="#954F72"><div class=WordSection1><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Ah, thanks Simon!</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This helps a lot.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,</p><p class=MsoNormal>Tamar</p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'><o:p> </o:p></span></p><div style='mso-element:para-border-div;border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='border:none;padding:0in'><b>From: </b><a href="mailto:simonpj@microsoft.com">Simon Peyton Jones</a><br><b>Sent: </b>Wednesday, June 15, 2016 13:07<br><b>To: </b><a href="mailto:lonetiger@gmail.com">lonetiger@gmail.com</a>; <a href="mailto:omeragacan@gmail.com">Ömer Sinan Ağacan</a><br><b>Cc: </b><a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a><br><b>Subject: </b>RE: CoreToStg Asserts</p></div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>Ah yes. This is a long-standing wart:<o:p></o:p></span></p><p class=MsoListParagraphCxSpFirst style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'><span style='mso-list:Ignore'>1.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'>The CoreTidy pass predicts what will be CAFFY (see https://ghc.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/GC/CAFs). It predicts that info because the output of CoreTidy is what goes into interface files.<o:p></o:p></span></p><p class=MsoListParagraphCxSpMiddle style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'><span style='mso-list:Ignore'>2.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'>The CorePrep pass messes the code a bit<o:p></o:p></span></p><p class=MsoListParagraphCxSpLast style='text-indent:-.25in;mso-list:l0 level1 lfo1'><![if !supportLists]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'><span style='mso-list:Ignore'>3.<span style='font:7.0pt "Times New Roman"'> </span></span></span><![endif]><span lang=EN-GB style='font-size:12.0pt;line-height:105%'>The CoreToStg pass coverts to STG, and at that point we know for sure what will be CAFFY and what will not<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>The assert trips when the predication in (1) doesn’t agree with reality in (3).<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>It would be Much Much better if we took the info from (3) and used that to drive the Core-to-IfaceSyn conversion that creates the interface file content.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>The only reason not to do this is that it’d mean delaying Core-to-IfaceSyn until pass (3) had happened.. possibly bad for space. But maybe it’s a non-issue in practice.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>See <a href="https://ghc.haskell.org/trac/ghc/ticket/9718">https://ghc.haskell.org/trac/ghc/ticket/9718</a><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span lang=EN-GB style='font-size:12.0pt'>Windows interacts with this because with DLLs some pointers that would be static closures turn into thunks (I think). See </span><span lang=EN-GB style='font-size:10.0pt;font-family:"Courier New"'>StgSyn.isDllConApp</span><span lang=EN-GB style='font-size:12.0pt;font-family:"Times New Roman",serif'>, and </span><span lang=EN-GB style='font-size:10.0pt;font-family:"Courier New"'>TidyPgm.hasCafRefs</span><span lang=EN-GB style='font-size:12.0pt;font-family:"Times New Roman",serif'> <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'>Simon</span><span lang=EN-GB style='font-size:12.0pt'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:12.0pt'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> ghc-devs [mailto:ghc-devs-bounces@haskell.org] <b>On Behalf Of </b>lonetiger@gmail.com<br><b>Sent:</b> 15 June 2016 00:26<br><b>To:</b> Ömer Sinan Ağacan <omeragacan@gmail.com><br><b>Cc:</b> ghc-devs@haskell.org<br><b>Subject:</b> RE: CoreToStg Asserts</p></div></div><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hi Ömer,</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks for the pointers, should help me find out more.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>It’s not a stock GHC as I’m working on getting Dynamic linking back on Windows.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This assert is triggered on the dyn version of the libs. So something’s bit rotted here.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Cheers,</p><p class=MsoNormal>Tamar</p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'><o:p> </o:p></span></p><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From: </b><a href="mailto:omeragacan@gmail.com">Ömer Sinan Ağacan</a><br><b>Sent: </b>Tuesday, June 14, 2016 18:46<br><b>To: </b><a href="mailto:lonetiger@gmail.com">Phyx</a><br><b>Cc: </b><a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a><br><b>Subject: </b>Re: CoreToStg Asserts<o:p></o:p></p></div><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman",serif'><o:p> </o:p></span></p><p class=MsoNormal>Hi Tamar,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Have a look at Note [Disgusting computation of CafRefs] in TidyPgm.hs. The</p><p class=MsoNormal>assertion triggered here is the one that checks `hasCafRefs` mentioned in that</p><p class=MsoNormal>note matches with actual CAF-ness.</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Are you using stock GHC? Which version? Do you have a minimal program that</p><p class=MsoNormal>reproduces this?</p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>2016-06-13 7:01 GMT-04:00 Phyx <<a href="mailto:lonetiger@gmail.com">lonetiger@gmail.com</a>>:</p><p class=MsoNormal>> Hi *,</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> I'm hoping someone could help me understand what the asserts in CoreToStg on</p><p class=MsoNormal>> line 240 and 216 are trying to tell me.</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> I hit both of them while trying to compile libraries as dyn.</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> WARNING: file compiler\stgSyn\CoreToStg.hs, line 250</p><p class=MsoNormal>> $trModule2 False True</p><p class=MsoNormal>> ghc-stage1.exe: panic! (the 'impossible' happened)</p><p class=MsoNormal>> (GHC version 8.1.20160612 for x86_64-unknown-mingw32):</p><p class=MsoNormal>> ASSERT failed!</p><p class=MsoNormal>> file compiler\stgSyn\CoreToStg.hs line 216 $trModule2</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> Please report this as a GHC bug: <a href="http://www.haskell.org/ghc/reportabug">http://www.haskell.org/ghc/reportabug</a></p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> WARNING: file compiler\simplCore\SimplCore.hs, line 633</p><p class=MsoNormal>> Simplifier bailing out after 4 iterations [6737, 736, 51, 9]</p><p class=MsoNormal>> Size = {terms: 12,990, types: 9,998, coercions: 443}</p><p class=MsoNormal>> WARNING: file compiler\stgSyn\CoreToStg.hs, line 250</p><p class=MsoNormal>> $fEqBigNat_$c/= False True</p><p class=MsoNormal>> ghc-stage1.exe: panic! (the 'impossible' happened)</p><p class=MsoNormal>> (GHC version 8.1.20160612 for x86_64-unknown-mingw32):</p><p class=MsoNormal>> ASSERT failed!</p><p class=MsoNormal>> file compiler\stgSyn\CoreToStg.hs line 240</p><p class=MsoNormal>> [$fEqBigNat_$c/=, $fEqBigNat]</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> Please report this as a GHC bug: <a href="http://www.haskell.org/ghc/reportabug">http://www.haskell.org/ghc/reportabug</a></p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> Kind Regards,</p><p class=MsoNormal>> Tamar</p><p class=MsoNormal>><o:p> </o:p></p><p class=MsoNormal>> _______________________________________________</p><p class=MsoNormal>> ghc-devs mailing list</p><p class=MsoNormal>> <a href="mailto:ghc-devs@haskell.org">ghc-devs@haskell.org</a></p><p class=MsoNormal>> <a href="http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs">http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs</a></p><p class=MsoNormal>><o:p> </o:p></p></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>