<html xmlns:v="urn:schemas-microsoft-com:vml" 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 14 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="blue" vlink="purple">
<div class="WordSection1">
<p class="MsoNormal"><a name="_MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The text in the committee draft is different (e.g., the exhortation about non-default alignment is gone), with an example to the effect
that a value of 8 means the entity's address is a multiple of 8 (not 2^8). So, alignment is conceived in terms of address bits, whatever those represent (not always bytes).
<o:p></o:p></span></a></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">If Clang is being infested with more target knowledge, okay, but that means tolerating the weirder targets in these cases. Dividing by CHAR_BITS makes an assumption
that isn't necessarily correct.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">--paulr<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">P.S. The committee is hoping to get a draft out for public comment Real Soon Now.<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>
<div style="border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt">
<div>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in">
<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""> cfe-commits [mailto:cfe-commits-bounces@lists.llvm.org]
<b>On Behalf Of </b>David Blaikie via cfe-commits<br>
<b>Sent:</b> Monday, September 12, 2016 5:12 PM<br>
<b>To:</b> reviews+D24426+public+6ee6274d38fdf0d6@reviews.llvm.org; vleschuk@accesssoftek.com; echristo@gmail.com; aprantl@apple.com; mehdi.amini@apple.com<br>
<b>Cc:</b> cfe-commits@lists.llvm.org<br>
<b>Subject:</b> Re: [PATCH] D24426: DebugInfo: Pass non-zero alignment to DIBuilder only if aligment was forced<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal">On Mon, Sep 12, 2016 at 5:00 PM Paul Robinson <<a href="mailto:paul.robinson@sony.com">paul.robinson@sony.com</a>> wrote:<o:p></o:p></p>
</div>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<p class="MsoNormal">probinson added a subscriber: probinson.<br>
<br>
================<br>
Comment at: lib/CodeGen/CGDebugInfo.cpp:3691<br>
@@ -3635,1 +3690,3 @@<br>
+ if (D->hasAttr<AlignedAttr>())<br>
+ AlignInBits = D->getMaxAlignment();<br>
StringRef DeclName, LinkageName;<br>
----------------<br>
dblaikie wrote:<br>
> is max alignment the right thing here? Should it be min alignment?<br>
> (is alignment in bits the desired thing across all of this too? It looked like in the backend patch there was some division by CHAR_BITS, etc?)<br>
I should think bits is the right choice here; seems more the province of the backend to convert it into the appropriate addressable units (commonly but not universally chars).<o:p></o:p></p>
</blockquote>
<div>
<p class="MsoNormal"><br>
The alternative thinking is that we've a generally sense we want to make more of this type information opaque to LLVM - so I'm somewhat inclined to make the frontend do the work of choosing what to emit and the backend just being as simple as possible.<br>
<br>
Hmm, seems like the DWARF spec details I can find: <a href="http://www.dwarfstd.org/ShowIssue.php?issue=140528.1">http://www.dwarfstd.org/ShowIssue.php?issue=140528.1</a> don't really specify what the value of DW_AT_alignment is, it's sort of assumed, by the
looks of it? I'm assuming it's bytes, the same as the byte_size attribute.<br>
<br>
<br>
<o:p></o:p></p>
</div>
<blockquote style="border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in">
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br>
<a href="https://reviews.llvm.org/D24426" target="_blank">https://reviews.llvm.org/D24426</a><br>
<br>
<br>
<o:p></o:p></p>
</blockquote>
</div>
</div>
</div>
</div>
</body>
</html>