<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Would <a href="http://llvm.org/docs/LangRef.html#langref-datalayout">http://llvm.org/docs/LangRef.html#langref-datalayout</a> be help?</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">- chenwj</div><div class="gmail_extra"><br><div class="gmail_quote">2017-05-22 23:26 GMT+08:00 Dr. ERDI Gergo via llvm-dev <span dir="ltr"><<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Mon, 22 May 2017, Dr. ERDI Gergo wrote:<br>
<br>
</span><span class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Actually, tracking down the sequence of function calls, it turns out that '8' is ultimately coming from the following call in DataLayout::getAlignment:<br>
<br>
getAlignmentInfo(AGGREGATE_ALI<wbr>GN, 0, abi_or_pref, Ty);<br>
<br>
this seems to return 8 with the following datalayout string:<br>
<br>
e-S8:p:16:8-i8:8-i16:8-i32:8-i<wbr>64:8-f32:8-f64:8-n8-a:8<br>
<br>
I think my problem is that 'a:8' probably doesn't mean what I think it should mean. What is the difference between 'a:8' and 'a:0'?<br>
</blockquote>
<br></span>
OK I just now tried with 'a:0' for identical result. I am now quite sure I am fully confused about what these alignment settings mean.<br>
<br>
Does 'a:8' mean single byte alignment (i.e. *no* alignment)? If yes, does that mean getAlignment for a struct type should return 1? In fact, when getAlignment returns 8, does that mean 8 bits (no alignment) or 8 bytes (64 bits) alignment? Or does that mean the lowest 8 bits of the address needs to be 0, i.e. 256-byte alignment?<div class="HOEnZb"><div class="h5"><br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Wei-Ren Chen (陳韋任)<br>Homepage: <a href="https://people.cs.nctu.edu.tw/~chenwj" target="_blank">https://people.cs.nctu.edu.tw/~chenwj</a></div></div></div>
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