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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi all,<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">thanks for the feedback.<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">Richard: On a second thought, it looks like it may not have much impact in the code generation, at least in x86. This was just in case unaligned accesses start
to appear in other targets. But maybe I’m being too cautious here. So I will drop the flag from the patch.<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">Reid: I agree that there is enough machinery now for packed fields and __unaligned would add little here. I will be dropping this from the patch as well.<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">Kind regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Roger<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>
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<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""> Reid Kleckner [mailto:rnk@google.com]
<br>
<b>Sent:</b> 17 February 2017 17:48<br>
<b>To:</b> Roger Ferrer Ibanez<br>
<b>Cc:</b> cfe-dev@lists.llvm.org; nd<br>
<b>Subject:</b> Re: [cfe-dev] [RFC] Implement code generation for __unaligned<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">I don't think we want __unaligned to affect record layout, we just want it to affect the alignment used when loading and storing an unaligned type. That's the way I read the MSDN description of __unaligned. I don't think Clang should implement
its own, different semantics from MSVC for __unaligned. That causes confusion and the compatibility issues you mention.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I think programmers already have enough tools to control record layout. They have __attribute__((packed)) and __attribute__((aligned(N))). What they don't have are good tools to take unaligned pointers from code they don't control and access
them safely. The MSVC version of __unaligned lets you do that, so I think we should just finish implementing it as described and call it a day.<o:p></o:p></p>
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