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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Chandler Carruth [mailto:chandlerc@google.com]
<br>
<b>Sent:</b> Thursday, October 04, 2012 3:56 PM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> Kim Gräsman; Evan Cheng; llvm-commits@cs.uiuc.edu LLVM; Nadav Rotem; cfe-commits@cs.uiuc.edu cfe<br>
<b>Subject:</b> Re: [cfe-commits] [llvm-commits] [Patch] Move TargetData from Target to Support/VMCore<o:p></o:p></span></p>
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<p class="MsoNormal">On Thu, Oct 4, 2012 at 3:51 PM, Villmow, Micah <<a href="mailto:Micah.Villmow@amd.com" target="_blank">Micah.Villmow@amd.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-size:11.0pt;font-family:"Calibri","sans-serif"">I'm curious how this could work.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;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-size:11.0pt;font-family:"Calibri","sans-serif"">I have two classes.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">TargetData and DataLayout.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;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-size:11.0pt;font-family:"Calibri","sans-serif"">I want to point all uses of TargetData at DataLayout.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;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-size:11.0pt;font-family:"Calibri","sans-serif"">typedef won't work not just because of forward declarations, but also because of static functions.</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;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-size:11.0pt;font-family:"Calibri","sans-serif"">So, I could define DataLayout as a subclass of TargetData, but once I want to move to DataLayout, how do I define
TargetData in a way that won't require changes to many many locations.</span><o:p></o:p></p>
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<p class="MsoNormal">I think you need to reverse the suggestion and instead use:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">class TargetData {<o:p></o:p></p>
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<p class="MsoNormal"> // existing code<o:p></o:p></p>
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<p class="MsoNormal">};<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">class DataLayout : public TargetData {<o:p></o:p></p>
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<p class="MsoNormal"> // some forwarding boilerplate<o:p></o:p></p>
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<p class="MsoNormal">}<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Then you can change everyone to refer to DataLayout, and then lift the implementation of TargetData up into DataLayout.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">You'll have to change folks to refer to DataLayout in o "top-down" way -- producers first.<o:p></o:p></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">[Villmow, Micah] This is a good suggestion, but I was actually thinking of doing it in the reverse. Turn TargetData into the forwarding boilerplate, but I just wanted
to make sure this was the intention instead of moving forward and having to redo some work.<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">What subprojects do I need to modify?<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Clang/LLVM/compiler-RT I know<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Others would be LLDB, dragonegg, vmkit?<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">What about libc++/polly/klee/safecode, etc...?<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Basically what is the line that separates which projects need to be updated by myself and what needs to be updated by their owners?<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Thanks,<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Micah<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;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-size:11.0pt;font-family:"Calibri","sans-serif"">Micah</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 style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Kim Gräsman [mailto:<a href="mailto:kim.grasman@gmail.com" target="_blank">kim.grasman@gmail.com</a>]
<br>
<b>Sent:</b> Thursday, October 04, 2012 1:33 PM<br>
<b>To:</b> Villmow, Micah<br>
<b>Cc:</b> Chris Lattner; Evan Cheng; <a href="mailto:llvm-commits@cs.uiuc.edu" target="_blank">
llvm-commits@cs.uiuc.edu</a> LLVM; <a href="mailto:cfe-commits@cs.uiuc.edu" target="_blank">
cfe-commits@cs.uiuc.edu</a> cfe; Nadav Rotem</span><o:p></o:p></p>
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<p class="MsoNormal"><br>
<b>Subject:</b> Re: [cfe-commits] [llvm-commits] [Patch] Move TargetData from Target to Support/VMCore<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>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">HI Micah,<o:p></o:p></p>
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<br>
On Thursday, October 4, 2012, Villmow, Micah wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Chris, the problem with steps #2/#3 is that plenty of clients have forward declarations of TargetData and the typedef won't work in this case, so I need to update the clients anyways.<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;mso-margin-bottom-alt:auto">One trick I've used as an alternative to typedefs is to just derive from the old class, e.g.<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;mso-margin-bottom-alt:auto"> class NewName : public TargetData {};<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;mso-margin-bottom-alt:auto">This is forward-declarable just as well as TargetData itself.<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;mso-margin-bottom-alt:auto">FWIW,<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">- Kim<o:p></o:p></p>
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