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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi Renato,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I am clearly not a specialist for debug info. It will certainly put some pressure on the debug info generator at opt level >= 01, as the stack slots will be reused, so it needs to place the info at the right place / right time.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>You have less live variables, at any given point in the function, but this assumes you have handled the dead variables correctly…<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>By the way, my patch indeed also affected some debuginfo (some breakpoint location if I remember correctly). I have switched temporarily to something else, but this patch proved to be extremely complex --- complexity linked to what you can find in the thread about temporary destructors. There is something going wrong in how the scopes are handled and my patch triggers it. I am probably breaking some undocumented or implicit assumptions. But there is definitely a lot of potential to reduce stack usage, and we saw that on real code.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cheers,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>--<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Arnaud<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Renato Golin [mailto:renato.golin@linaro.org] <br><b>Sent:</b> 31 July 2014 10:21<br><b>To:</b> Arnaud De Grandmaison<br><b>Cc:</b> Clang Dev<br><b>Subject:</b> Re: [cfe-dev] Adding lifetime begin/end to unnamed temporaries<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p>Hi Arnaud, <o:p></o:p></p><p>Can't this affect debugging as well?<o:p></o:p></p><p>I mean, if you run this on O1 or less, you'll have a lot more variables optimised away, especially at the end of the function, and at higher optimisation levels you'll have a lot less variables to care about. <o:p></o:p></p><p>Cheers, <br>Renato <o:p></o:p></p><div><p class=MsoNormal>On 23 Jul 2014 01:23, "Arnaud A. de Grandmaison" <<a href="mailto:arnaud.degrandmaison@arm.com">arnaud.degrandmaison@arm.com</a>> wrote:<o:p></o:p></p><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I am trying to implement the lifetime marker insertion for unnamed temporaries in order to reduce stack consumption.<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'>Inserting the lifetime.begin marker is the easy part; on the other hand, inserting the lifetime.end gets a bit more complicated, as it involves scoping , exception handling and lifetime extension.<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'>Ideally, the lifetime.end marker should be inserted when the scope is exited, after the cleanups have been run. The problem is that in some cases, an object with a trivial destructor for example, there is … no cleanup. The existence of cleanups appears in the AST with the ExpWithCleanups, which wraps the underlying MaterializeTemporaryExpr.<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'>This is used in CodeGenFunction::EmitLValue to start a new RunCleanupsScope when visiting an ExpWithCleanups. My problem is how can I add a RunCleanupScope for MaterializeTemporaryExpr that are not part of an ExpWithCleanups. I can not always add a new scope, because it would mess-up the cleanup ordering --- when there are cleanups, the lifetime.end marker should be emitted after the destructor.<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'>Is there anything obvious I am missing ?<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'>Any hints would be welcome. <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'>Cheers,<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'>Arnaud A. de Grandmaison<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div></div><p class=MsoNormal style='margin-bottom:12.0pt'><br>_______________________________________________<br>cfe-dev mailing list<br><a href="mailto:cfe-dev@cs.uiuc.edu">cfe-dev@cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev</a><o:p></o:p></p></div></div></body></html>